Section I Aluminum-the MetalChapter I Early and Present-Day Processing Aluminum is the most abundant of all metals and. next to oxygen and silicon. is the most abundant of some 90 elements found in the earth's crust. Aluminum is a ductile metal, silver-white in color, which can be readily worked by rolling, drawing, spinning. extruding, and forging. Its specific gravity is 2.70. Pure aluminum melts at 6600(; (I 2200F). Aluminum has relatively high thermal and electrical conductivities. The metal, in the presence of oxygen. is always covered with a thin, invisible film of oxide which is impermeable and protective in character. Aluminum, therefore, shows stability and long life under ordinary atmospheric exposure. Because of its chemical activity and affinity for oxygen, aluminum does not occur in nature in its metallic state; it is always in combination with other elements. Many gems are crystalline forms of aluminum compounds. Rubies and sapphires, for example, are combinations of aluminum and oxygen; garnets are aluminum and silica; and jade is aluminum with sodium. oxygen, and silicon. Alums are aluminum compounds which bave been in widespread use since ancient times. Alums were employed by Egyptians and Babylonians to compound medicines and vegetable dyes. In 1782, the French chemist, Antoine Laurent Lavoisier , stated his belief that alumine (alum) was an oxide of a metal having an affinity for oxygen so strong that it could not be isolated by then known means. In 1807, Sir Humphrey Davy attempted to isolate aluminum electrolytically, but was unsuccessful. However, he named the unisolated element aluminum, and in 1809 produced an iron aluminum alloy by means of an electric arc. In the year 1812, a body of aluminum ore was dis covered at Les Baux, France. Named after the town of its discovery. bauxite is the most important commercial ore containing hydrated aluminum oxide. In 1825, H. C. Oerstedt succeeded in producing small bits of metallic aluminum by heating an amalgam of aluminum chloride and potassium. Twenty years later, FriedriCh Wohler managed to produce aluminum particles as large as pin heads. He enthusiastically noted, "The metal is light, ductile, stable in air. and can be melted with a blow pipe." In 1854, Henri Sainte-Claire Deville announced the production of aluminum "lumps the size of marbles." Limited production started, and the price of aluminum dropped from $545 per pound in 1852 to $17 per pound in 1859. In 1888, a German chemist, Karl Joseph Meyer, was issued a patent for a process of making alu minum oxide (alumina) from low silicon-content bauxite. Further research that made possible the present-day processes was conducted in France by Paul Louis Herault, and in America by Charles Martin Hall. Unknown to each other. they independently found that electrolytic reduction of alumina could readily be achieved if alumina was dissolved in molten cryolite. Owing to the widespread distribution of accessible fields of bauxite, many of which can be mined by surface-strip methods, bauxite is readily obtained. Research and development for the benefit of both producers and users are economically practical. The present-day process for primary production of aluminum ingot, subject to variation depending on alloy and properties required. is schematicaUy shown by Figure I-I. The Bayer process is used to convert bauxite into aluminum oxide, called alumina (upper part of Figure I-I). The alumina is then reduced to metallic aluminum by the Hall process (lower pari of Figure 1- I). The subsequent conversion of the aluminum ingots into rods for cold drawing of conductor wire or for making extruded bus bars is performed in fabricating plants as shown by Figure 1-2, subject to process variation by individual fabricators. Aluminum MetaJ.Womlll Precesses As an aid to understanding the function of the equip ment shown on the flow sheet of Figure 1-2, a brief out line of the processes used for production of aluminum conductors either as stranded cable or as bus shapes and tubes is as follows (detailed consideration of many of these processes is discussed in subsequent chapters): Extruding. The aluminum is forced under pressure through one or more die openings. To accomplish this, the aluminum billets are heated and placed in a cylindrical container filted at one end with a die having an opening shaped to produce the desired section. A ram activated by a hydraulic piston forces the metal of the biDet through the die opening onto a run-out table so it appears 1-1 o/uminum--the me/ol + + BAUXITE + COAL FUEl OIL + SODA LIME '~------------------------------------------------------------~,-~I •{) METAllURGICAL \ :7 .1 + TAR COKE -- PETIIOLEUM I '\, + FLUORSPAR +SULPHUR '~""""""-r'-""""""~' PITCH COK£ I U ~--{}~--~ BAKED CARBON AlUMINUM flUORIDE FURNAcr LINING , .. 4 ALUMINUM SMElTER Fig. 1·]. What it takes to make aluminum: From bauxite to ingot. ~'I'OUffta ()'"r~I<' M'~ 1·2 /111M..", ., ~ T..NM~Am;;liif;a;,nrl -----, · uu ~ .. lIi1U.frm<. 1£., 111£4"'«1 <Io£NCH '''''N'''E .......E. CASr ' AGI"" 'U'H",C ... .. PlATE --.~'''--.- rH. oc ...., r·"'IJi. SHEAIi CASTER ""SH HE., FUR'ACE ~ AGING _ 'U.HAtE SHEA. ~ sr~!C~'~ -;..;e,;;,~. ~/~ /,,/ ~ / HEAT TAEA1'lttG OVENCk AGING /'t. :;QitmilJiiIj- jujj)ii1 I!O~ :~.a~:L~" 'MCE ,, FURNACE fURNACE CHAAf$fR ~~ ,, litO,,>. 1IA!i:i!iifI'" W1llLlJII!I!:: I, ,I, rALy~IIIUM $eRArr f' Gf;,.1£'~' - w• /, / Ii,\ I, I / HeAT I ALlOYW{; \ \ ~1f~)LOW HEATING FURNACE ~---.. ~ ~" FUIINA<;r nnm IN:lj: ~ FINISH RottiNG MILL COlLER 4tfNEAll."'" 'lfIlU: Fu~ .. ~~ "vRAWliro ~AC£ " ' , '- ~ _..\I" ~ STff~O/N(; MACHIN! liIACHIN£ Slst£rCHrR ffJII. $~lftfG Will Afltl f'i.?ilj;-j l2l!J @AI!'!. ~A~ ~~.Ujiji\~i. ~ifgJ E.1Rusro/j PRess ~ SA~~ ,~_ . CO ANNE:~tltlG f:'URN4Cr CHAIiBEi! srllA>GH"N'R S4W. ~ , \ OUJ.I~'" I'~' Will AGING • ELtCTRICALj CONOUCTOR ~-- ~--!'W!Ir.IWIWI/I. '<:XT/lOOED SHAPES ANI) TUBE j '''''t'''N. 'U"'CEa"eJ\: P<llht,. '"MAce • -~I)RAWN :'":j;a,: &::e..,. L!U8E tefl/ JfIl[[[I !t. PiC. 1·2. Bow aluminum i. !abrft::ated. <l1IAw "EA' J'RE'TI/IC - ~- "-. . !M=IIl, : I WENcH;_ tANA' I srRE'CHOl SAw ACING FURNAC' ....... ~"',-- aluminum--the metal in the required shape. Extrusions are used for many bus conductor shapes and also for preliminary stages of production of rods that later are to be rolled and drawn to small diameter as wires. Rolling. Mills fitted with suitable rolls are employed to reduce the diameter and increase the length of aluminum biUets. A series of such roUing stands is required before the diameter is reduced to 3/8 inch. This is the usual size of rolled rod employed as stock for the wire-drawing machines which reduce the aluminum to the required final wire diameter. Wire-drawing. In this operation the 3/8 inch diameter redraw rod is drawn through a series of successively smaller dies in a coarse-wire machine, and then through a fine-wire drawing machine. Intermediate annealing, coiling, and heat-treating may be done between the various operations. Stranding. In production of most bare cable, stranding is the final operation. Aluminum conductor of 7. 19, 37, or 61 strands is produced on stranding machines. When these strandings surround an inner core of a single wire. or a core of 7 or 19 wires, the various strandings described in Chapter 3 are produced. Tubular or rigid frame stranding machines are used, the latter for applying the last layers of wire. The various wires received from coils are spun around a central core and brought out in the shape of a cone. The apex of the COne is the core around which the wires are spirally wrapped. Auxiliary devices relating to coiling, cutting, safety cut outs, friction brakes, and the like are associated with much of the described equipment. Casting. The production of single aluminum castings for conductor fittings is accomplished by pouring the desired molten alloy into sand or permanent molds, or into a die-casting machine. The castings may be heat treated, quenched. and aged as required. Large, thick aluminum bus bars for station circuits in electrolytic plants and those of other large-current users often are made by a continuous casting process: the melted metal is run out through an orifice slightly larger than the section desired. Water cooling is applied at the orifice, and after shrinkage from cooling the required finished size is obtained, as a solid bar of the desired length. A modification of this continuous casting process is also used for production of rod that is then finish-rolled to redraw size (3 (8 inch diameter) for subsequent wire drawing. Sequence of Fabricating Operations The aluminum ingots from the reduction plant (smelt er) shown in Figure 1·1, plus alloying materials, are remelted as the first operation in the fabrication piant, Figure 1·2. Subsequent operations vary according to the end·product desired. The flow sheet shows a typical arrangement for the production of electrical conductors in the form of stranded conductors. and extruded bus 1·4 bars and tubes. Fabricators may not have fully integrated plants. For example, some cable fabricators start with 3/8-inch diameter round redraw rod of specified properties (ASTM B 233). The redraw rods are the result of rolling to that diameter by another fabricator. The finished stranded conductor, including drawing from 3/S-inch rod to the final wire diameter, is the work of the final fabricator. Aluminum and Aluminum Alloys for Electrical CondudOls Aluminum and aluminum alloys are listed according to the major alloying element, and are designated by four digit numbers. The first digit of the number designates the major alloying element, and the remaining three-digits represent modifications of the basic alloy, according to its registration with The Aluminum Association. The alloy listing based upon this method is as follows: Principal Alloying Element (99.0% pure aluminum minimum) Copper Manganese Silicon Magnesium Magnesium and Silicon Zinc Other Elements 4-digit Number lXXX HeatTreatable no 2XXX 3 XXX 4XXX 5XXX yes no no no 6 X X X 7XXX 8XXX yes yes some Aluminum 1350, the form of aluminum most widely used for electrical conductors, has a minimum aluminum content of 99.50 percent, and because of this high purity it is not considered to be an alloy. It has a conductivity of approximately 61.0 percent lACS minimum. It is also available with 62.0 percent lACS conductivity. Greater strength, however, is obtained if certain alloying ingre dients are added, and though the resulting aluminum alloy conductors have less conductivity than aluminum 1350, considerations in which strength is a factor justify their use. Practice has substantially limited wire for stranded electrical conductors to the alloys shown in Table I-I which also may be stranded in combination with steei wires or with other alloys of aluminum wire. Treatment for Improvement of Physical Properties Improvement of strength. ductility, bending quality, and corrosion resistance often may be achieved by the addition of alloying elements, cold working (strain harden ing), and heat treatment. The means of increasing strength classify the alloys roughly into two categories, non-heat-treatable and heat-treatable. The initial strength of non-heat-treatable aluminum (1350,5005, and the 8XXX series alloys) depends partly early and present·day pro,essing TABLE 1·1 Mechanical and Physical Properties of Aluminum and Aluminum Alloy for Use in Electrical Conductors(1) (2) Designation 1350-H19 1350·HI6 or -H26 1350-H14 or -H24 1350-H12 or ·H22 1350-0 I Tensile Strength(3) , ksi 11000 Iblln2) Min Max 29.0 22.0 20.0 17.0 14.0 ""."," _lJr I 8030-H221 15.0 8176-H24 8177-H221 15.0 15.0 .. ... 24.0 16.0 14.0 24.5 17.0 15.0 12.0 12.0 4.0 8.5 6201-T81 I 460 21.0 22.0 \ , 20.0 22.0 , I ! , i , i Minimum Conductivity % IACS(5) ASTM Spec Temper 1.5 61.0 61.0 610 61.0 8 230 8 609 8509 8 609 Hard 3/4 Hard 1/2 Hard 114 Hard 20.0(6) 61.8 8 609 3.0 10.0(7) 52.5 61.0 61.0 8398 8800 B 800 ; Yield Strength Minimum ksi(3) Elongation (Typlcal)(4) '% in 10 in. 10.0 10.0 10.0 !i I 61.0 8800 Fully Annealed Hard Intermediate Intermediate Intermediate 61.0 8800 , Intermediate ; , ! (1) For reduction in strength at joints, see applicable ASTM Specification. (2) For strength and conductivity of bus-conductor and bolt alloys, see Tables 13-1 and B-2, Chapter 13. (3) There is a slight variation, depending on diameter. The listed strengths apply to wire between 0.1001 inch and 0.1100 inch diameter. (4) There is no yield in the generally accepted sense of the term. The listed values are typical of stress when permanent elongation is 0.002 in. per in. (5) Conductivity is measured in tenms of that of annealed copper as established by the International Electro-Technical Commission as an International Annealed Copper Standard (lACS). See Chapter 3. Commercial hard-drawn copper wire has • conductivity of 96.16% lACS. (6) Approximate, not minimum. (7) Shall not be less than 10%. on the hardening effect of elements such as manganese, silicon, iron, and magnesium. singly or in combinations. Additional strengthening is obtained by various degrees of cold-working, inclUding that of the wire-drawing pro cess. Heat treatment during processing does not increase strength, except that alloys containing appreciable amounts of magnesium when supplied in strain-hardened tempers are usually given a final elevated-temperature treatment called stabilizing to insure stability of properties. This heat treatment sometimes also produces a certain amount of annealing. The strength of heat-treatable alloy 6201 is increased by subjecting it to thermal treatment. The complete process of obtaining the T81· temper involves a combina lion of solution heat treatment, quenching, wire drawing, and artificial aging. Strain hardening during wire-drawing also is a strengthening factor. Temper Designations The Aluminum Association issues a compilation* (also ANSI H35.1-1988) of designations for alloys and tempers. The alloy-number designations are those shown on page 1-4 hereof. The principal temper designations are the H-numbers for non-heat-treatable alloys (1350 and 5005) and T-numbers for heat-treatable alloy (6201) and alloys used for bus conductors. Abstra.:ts of designations applying to wrought el"'trical conductor aluminum or aluminum alloys are as follows: -Aluminum Standards &: Dola; latest edition available from The Aluminum ASSociation. Of member companies. 1·5 aluminum--the metal TABLE 1-2 Chemical Composition Limits (Maximum) for Wrought Aluminum Alloys for Electrical Conductors in Percent<1) Aluminum-Alloy Number. Bus Conductor Wire Principal Bolts 1350 6201 8017 8030 8176 8176 6101 6063 6061 2024(2) Copper 0.05 Iron OAO Silicon 0.10 0.01 0.10 O.SO 0.50-{).9 0.Q3 0.6-0.9 0.10 0.03 0.06 0.10-0.20 0.55-0.08 0.10 0.15·0.30 0.30-0.8 0.10 0.40-1.0 0.03-0.15 0.04 0.25·0.45 0.10 0.01-{).05 0.05 0.05 0.05 om 0.04·0.12 0.05 0.10 0.35 0.20·0.6 0.10 0.45-{).9 0.10 0.10 0.15-0.40 0.7 0.40-0.8 0.15 0.6-1.2 0.25 0.04·0.35 3.8-4.9 0.50 0.50 0.30-{).9 1.2-1.8 0.25 0.10 0.04 (3) 0.03 0.10 0.01-{).04 0.10 O.SO 0.30-0.7 0.03 0.35-0.8 0.10 0.03 0.06 0.10 0.05 0.15 0.15 0.05 0.15 0.05 0.15 Alloy Element Manganese MagneSium Chromium Soron 0.05 0,01 0.05 TItanium (2) Zinc Other. each Other, total Aluminum 0.03 0.10 99.50 0.03 0.10 0.04 (4) 0.Q3 0.10 Remainder 0.05 0.15 0.03 0.10 003 0.10 Remainder (1) Composition in weight percent unless shown as a range. (2) 0.02 Vanadium plus TItanium. (3) 0.003 Ll1hium. (4) 0.Q3 Gallium. (5) Bolts of 2024·T4 alloy should be anodized with adequate thickness and seal to impart adequate corrosion resistance for the application. F: 0: H: 1-6 as fabricated. Applies to the shaping processes in which no special control over thermal conditions or strain-hardening is employed. For wrought products. there are no mechanical property limits. annealed, Applies to wrought products which are annealed to obtain the lowest strength temper, and to cast products which are annealed to im prove ductility and dimensional stability. The 0 may be followed by a digit other than zero. strain-hardened (wrought products only). Applies to products which have their strength increased by strain-hardening, with or without supplementary thermal treatments to produce some reduction in strength. The H is always followed by two or more digits. The first digit following the H indicates the specific combination of basic opera tions, thus: HI: strain-hardened only. without supplementary ther mal treatment. H2: strain-hardened and then partially annealed. The second digit following HI or H2 indicates the final degree of strain hardening. They range from 0 to 9. "9" designates fully hard tempers whose min imum ultimate tensile strength exceeds that of the 8 temper by 2.0 ksi or more. The other numbers represent ultimate strength as related to "0" fully annealed and "8" representing hard. Thus, "4" designates half-hard, "2" quarter hard, and "6" three quarters hard. The third digit when used indicates a variation of two-digit H temper, thus: Hill: strain hardened less than the amount required for controlled H II temper. early and present-day processing H1l2: some temper acquired from the shaping process but no special control over the amount of strain hardening or thermal treatment, but there are mechanical property limits. T: thermally treated to produce stable tempers other thon F, 0, or H, with or without supplemen tary strain-hardening to produce stable tempers. The T is always followed by one or more digits. The numerals 1 through 10 following the Tin dicate specific sequences of basic treatments as follows, applying to bus conductors or to 6201 alloy: T6: solution heat-treated and then artificially aged. Applies to products which are not cold worked after solution heat treatment, or in which the effect of cold work in flattening Or straightening may not be recognized in applicable specifications. T8: solution heat-treated, cold worked, and then arti ficially aged. Applies to heat-treated products which are cold-worked to improve strength, or in which the effect of cold work is recognized in applicable specifications. Additional digits, the first of which shall not be zero, may be added to T6 or T8 to indicate a variation of treatment which significantly alters the characteristics of the product. Anodizing Aluminum bolts for bus-conductor assemblies, if likely to be used under moisture conditions, should be anodized. Anodizing is an electrolytic process which increases oxide layer thickness, first producing a porous layer which is then sealed. The result is a surface that is smooth, hard, and corrosion resistant. All aluminum bolts and nuts require suitable lubrication to reduce friction, prevent seizing, and improve corrosion resistance. Other Processes The chapters in this book describe other processes re lated to the fabrication of electrical conductor components and systems. Among these are welding, plating, forming, application of protective armor, and insulation, and the many that are related to installation and connection of the conductors. 1-7 . rather than electrical conductor. The Effect of Alloying A detailed study of aluminum applications usually involves aluminum alloys that have properties markedly different from those of the basic metal. Light weight: Ease of handling. longer spans. Most industrial. the supplemental treatment (cold worlting and heat treatment) usually is divided into two parts often at different locations: (I) that performed during the production of redraw rod (0. as well as the properties under extremes of temperature.0 percent lACS. the conductivity of aluminum 1350 is 61. are also shown in Table I. which are used in the pro duction of wires for cables.4% lACS is available in 1350 on a special order basis). The conductivities of 6201 and the 8XXX series alloys in the tempers. clean stripping.Section I Aluminum-the Metal Chapter 2 Aluminum Conductor Properties and Advantages The mechanical and electrical properties of bare alu minum wire and stranded conductor are tabulated in Chapter 4 and of bus conductor in Chapter 13. Thus. Workability: Permitting a wide range of processing from wire drawing to extrusion or rolling. these are: I. Certaln general properties related to the use of aluminum. and mOre distance between pull-ins. In the manufacture of heat-treatable aluminum alloy conductor wire. 2.0 ks!.0 percent lACS minimum due to low level impurities inherent to commerical processing (up to 62. in their application as electrical conductors are discussed in this chapter. Principally. Other qualities of aluminum. The reduction of conductivity associated with this major change of strength is only from 61. as distinct from other metals. depending on alloy. The conductivity for bus conductor alloys is shown in Table B-2. low installation costs. However. Creep: Like all metals under sustained stress. and the strength of the heat-treatable-alloys is brought to that of the specified -T temper by heat treatment as explained in greater detail in Chapter I. 5. and chemical atmospheres do not cause corrosion. Strength: A range of strengths from dead soft to that of mild steel. 3. The strength of the non-heat-treatable alloys is brought to the value specified by the -H temper of the alloy by cold working and/or partial annealing. Aging may be performed subsequently.0 percent lACS. Conductivity The conductivity of pure aluminum is about 65. The cor rosion resistance of all alloys can be improved by anodizing. Merely adding the alloying elements to the mixture is not sufficient to produce the desired results. are rarely associated with any commercial use of electrical conductors. Conductivity: More than twice that of copper. 6.0 percent lACS to 55.0 percent addition of other metals supplemented by a specified heat treatment converts nearly pure aluminum to 6101-T6 electrical bus conductor with an increase in minimum yield strength from 3. Corrosion resilance: A tough.L A comparison of conductivities of metals sometimes used for electrical conductors is shown in Table 2-1. less than 2. With aluminum. such as thermal con ductivity and fatigue resistance. marine. design factors take it into account. The high-rellectivity and non-magnetic characteristics. hence are not considered herein. Compatibility with insulation: Does not adhere to or combine with usual insulating materials. there is a gradual deformation over a term of years. No tin-coating required. The high est strength alloys are employed in structural. The 2-1 . 4. have a bearing on con ductor section. providing the proper alloy is selected. Excel lent bend quality. per pound.375 inch diameter) and (2) that performed during or after reduction of diameter of the redraw rod to the finished wire size. 7. applications. Bus-conductor shapes have most of the necessary heat treatment per formed during extrusion.5 ksi to 25. protective oxide coat ing quickly forms on freshly exposed aluminum and it does not thicken significantly from con tinued exposure to alr. 7 8.0 Conductivity Specific Percent lACS Gravity(3) Wgt. zinc. titan ium. but it is customary to anodize such bolts for corrosion protection and to lubricate them to reduce friction and prevent seizing.2 Liallt Weiallt The relative conductor weights required for equal con· ductivity using various metals are listed in Table 2-2.6 213.1 38. and nickel cause but small reductions in con· ductivity of aluminum.51 1. These were developed from Table 2·1 (percent lACS mass conductivity and density values) applying conversion methods described in ASTM Specification B 193.93 2. Ninth Edition. As com mercially supplied.70 4. Volume 2.7 376. to I200C. Reduced capital and installation costs are an added advantage of aluminum conductors by reason of the long-span capability of ACSR and ACAR.0% lACS 8030·H221 61. (3) Specific gravity is density of a materia! compared to that of 'pure water which has a density of one gmJcm~" (4) Conductivity on a weight basis compares the conductivities of metals The tables of mechanical properties in Chapter 4 show rated fracture strengths of aluminum and aluminum-alloy conductors as single wires or as stranded cables.0% lACS Sodium 41. metals listed are . The variation of conductivity (and its reciprocal. for the same weight.0% lACS 8176·H24 61.those in almost pure form. Basis(2) Silver Copper ! Aluminum Titanian Magnesium i Sodium 108. Direct current (de) resistivity values for the usual aluminum alloys used for conductors are shown in Table 3-5.49 8. HD 96. silicon. using the unit ksi values of tensile strength for tbe various alloys as listed in Table 13·1.0% lACS 6201·T81 52.0% lACS) Metal Percent lACS Percent lACS Mass Relative Volume Conductivity .5% lACS 8017·H212 61.97 91. magnesium. and the greater distance between pull-in points in duct and conduit installation.4 103. 2-2 Chapter 13 contains similar tables of sizes and structural properties of usual bus-conductor shapes so that tbe strength of a bus installation under normal or short-circuit conditions may be readily computed. Stnmgtll (2) Conductivity on a volume basis compares conductivities of metals for the same cross-sectional area and length.5% lACS 6101·T65 56. the conductivity values are slightly less. Copper.9 102.1 197. and manganese are alloying elements that cause the greatest reduction of conductivity.0% lACS 8177·H221 61. reo sistivity) for usual applications is described in Chapter 3 where tables and formulas show the variation of co efficient of dc resistance with temperature and witb alloy for the usual range of conductor temperatures. The lighter weight aluminum provides obvious handling cost reductions over heavier metals. but it is not used as a major alloying element in electrical conductors because of a re duction in corrosion resistance. or in combination with steel reinforcing wires for ACSR (alumi num-conductor steel-reinforced) or with high-strength aluminum-alloy reinforcement for ACAR (aluminum cable alloy-reinforced).aluminurn---the metal TABLE 2-1 Relative Conductivities of Pure Metals(l) Metal Conductivity : Percent lACS i Vol.9 4. The reduction of conductivity caused by individual alloying agents in aluminum has been studied extensively. Chrontium.0% lACS Copper Comm'l. Copper as an alloying agent adds much to strength. The reasons why alloying and associated cold-working and/or heat·treatment increase the strength of the basic metal are explained in texts on aluminum metallurgy.74 0. Temperature coefficients for bus·conductor alloys are listed in Table 13-3.7 41. Basis(4) 10. WorUbility This term has to do with the ability of the electrical con· ductor to withstand single or repeated bending (the latter TABLE 2-2 Relative Weights of Bare Conductor to Provide Equal Direct Current Conductance (20°C) (as Related to the Weight of a Conductor of Aluminum 1351l-61. Conductivity Weight Aluminum 1350 61. Iron. The resistance under alternating current (ac) condi tions involves the concept of skin effect and R=!R"c ratio as explained in Chapter 3.0% lACS 201 174 187 201 201 201 201 96 376 100 116 108 100 100 100 100 209 53 . and vanadium produce greater reductions.1 64. (1) Conductivities and densities taken from the ASM Metals Handbook. Cables of other types similarly are strength rated. Aluminum alloy 2024· T4 bolts contain copper as an important alloying element. a WOO-foot span of ACSR cable is estimated to increase its sag from 22 feet to 26 reet in 10 years at WOP. Other thermal properties that require consideration in applications are the expansion or contraction with changes in temperature and the thermal conductivity (the rate at which heat is conducted).0000115 in. Also. Corl1lSion Resistance The inherent corrosion resistance of aluminum is due to the thin. The excellent workability of aluminum is also apparent from noting the facility with which it may be extruded. The coefficient for the bronze alloys commonly used for bolts is about the same as that listed for copper. though not listed as "marine" alloys.4 to 0. Charts such as Fig. but they are not significant in usual engineer ing design. hence it has no effect on rubber or rub ber-like compounds containing sulphur. and drawn. The bend radii for tlatwise and edgewise bending of aluminum bus bars depends on alloy and temper. hard-drawn 1350-H19 aluminum wire in stranded cables under a steadily applied load of 14 ksi at 20'C (70 percent of minimum yield strength) will creep approximately 0. Creep data have been incorporated in stress-strain curves for overhead conductors. the IO-year creep for a 1350-H19 cable at 10 ksi is estimated to be 0. Similarly.lOC Slight differences occur for various aDoys and tempera ture ranges.17 percent. are well suited for oceanshore applications. 5-11. Usual insulating materials do not adhere to the aluminum: hence removal is easily performed by simple stripping.23 percent: the horizontal distance between curves 2 and 4 at 10 ksi. For overhead cables. Aluminum re quires no tinning of the conductor metal before insulation is applied. changes in sag due to temperature changes are discussed in Chapter 5.lin. and its tension drops from 5700 pounds to 5100 pounds. as well as for usual industrial and chemical atmospheres. formed.lin. tough. temperature and time under load. by comparing Fig.lOC Steel 0. This deformation is in addition to the expected elastic deformation. Thus. metal stressed below yield for a short time returns to its original shape and size by virtue of its elasticity.0 percent generally is considered allowable. Bus bars creep in compression.6 percent of initial length in 10 years.series. The usual design coefficients of linear expansion for the principal conductor metals as well as those to which the conductor might be joined are as follows: Aluminum 0. Actual movement of 2·3 . when the time period is sufficiently long. Where unplated flat surfaces are joined. the ratio of arc length increase for this change of sag is about 0. as with bus conductors or terminal pads. From Fig. 5-11 also are available for many ACSR sizes to pro vide better accuracy.. suitable alloys of the 600Q. Cable manufacturers supply sag and tension data that include the effect of creep.0000230 in. oxide coating that forms directly after a fresh surface of metallic aluminum is exposed to air. metal fabrication. From the catenary Table 5-4. Present-day compression connectors act to break the oxide layer on the wires of stranded cable connections. that is. compared with that of the unwelded alloy. and because the metal is not hard drawn. Instances where corrosion has appeared are usually traceable to connections between dissimilar metals subjected to moisture conditions. a 10-year creep of 1. 5-2 and 5-3. Allowance must be made for differing rates of thermal expansion when aluminum is joined by steel or bronze bolts. scratch brushing and the addition of oxide-inhibiting joint compound remove the oxide and prevent its further formation because the compound excludes oxygen. is further evidence of the workability of aluminum.lOC Copper 0. shape and load.aluminum conductor properties and advantages for portable cables). and for bus bars to be bent to a specified radius either tlatwise or edgewise. occurs. or when aluminum pads are bolted to copper pads. For example. the long time creep is about 1.7 feet of arc length for the WOO-foot span. as are the aluminum 1350 conductors. Creep can be considerably reduced by proper choice of metal.0000169 in.lin. rolled. That bus conductors also can be readily welded with only partial loss of rated strength. The extent of creep is determined by the properties of the metal involved. Aluminum compares favorably with other conductor metals in this regard. called creep. plastic deformation. Compatibility with Insulatillll Aluminum does not have the sulphur-combining prop erties of copper. Creep Creep is plastic deformation that occurs in metal at stresses below its yield strength. and the unwanted effects of creep may be nullified by proper deSign. Design stresses to limit creep to this amount in various alloys are in Table 134. Protective means should be employed to prevent this. Thermal Properties The variation of electrical dc resistance with tempera· ture was covered in the preceding discussion of conduc tivity. applied stress. Another reason for the excellent corrosion resistance of aluminum conductors in ordinary atmospheres is that the alloy components are selected so as to minimize corrosion. it does not produce stearates Or soaps by combining with oil content of an insulation. Normally. However. They are listed in Tables 13-5 and -6 as a design guide to what can be expected during fabrication of a bus-bar assembly. conduit. or when buried. For copper. This factor is important when locating underground faults (see Chapter 12). is not proportional to increase in conductor length with temperature. it is about 0.48. Tests show that lateral displace ment (snaking) of the cables will absorb 3 to 5 times the increase in length.. the amperage at which the conductor will melt and separate at a ground point. i. it is about 0. . it is about 0. The thermal conductivity of aluminum depends on alloy and temper.aluminum-the metal insulated conductors in duct. it is less. For 1350-H19. whereas for alloys of lower electrical conductivity. Heat dissipation from bare suspended cable is about the same for aluminum and copper conductors of the same ampacity rating.56 callcm2/cml OC/sec. They serve to explain why aluminum is such a satisfactory metal for electrical conductors. For 6063-T6. This subject is discussed in Chapter 13.e. and to some extent it is related to short-circuit ampacity rating. ••••••••• The preceding discussions of general properties of aluminum conductors provide background for the design considerations described in the following chapters. as proved by its excellent long-time operating-experience record. tray. a factor taken into account when planning welding procedures. 2-4 The rate at which heat is conducted from a hot spot (the thermal-conductivity rate) affects the "burn-off" characteristic of a conductor.98. hence heat is not conducted away from a hot spot in aluminum as rapidly as with some other metals. insulation type. (3) An increase of ten gage numbers multiplies area and weight by 10 and divides de resistance by 10. and halves dc resistance. For wire sizes larger than 4/0 AWG.) diameter. " Symbols for types of aluminum conductors: AAC all-aluminum conductors (of 1350 aluminum). Certain general physical prop erties have been described in previous chapters. and approximate relationships between the sizes. Many types of bare conductors are in use depending on application requirements. neutral configuration and size.3-1) Area in cir mils 1. Fig. R. Detailed physical and electrical properties of lbe various com mercial sizes of bare conductors are listed in Chapter 4.500 cmil. ~raphs and data in tables are taken from Alcoa Aluminum Overhead Con ductor Engineering Series handbooks. the size is desig nated in circular mils. Fig. as in the example under Table 3-6 wherein the code word "Blue bell" identifies a specific cable. number of phase conductors.033. Wire sizes of 4/0 AWG and smaller also are often designated in cir mils. These code words are tabulated in Aluminum Association pUblications "Code Words for Underground Distribution Cables" and "Code Words for Overhead Aluminum Electrical Cables.. One cir mil is the area of a circle I mil (0. 3-1 shows typical full-size cross-sections. code words are often used. however much lbat applies to hare conductors also pertains to lbe metaUic part of in sulated or covered conductors which are considered in Section III. As one emil = ". type of assembly.000. ACSR aluminum-conductor steel-reinforced (steel wire rein forcement)./4 sqmils (Eq.) 3·1 . In our text. configuration.). Expressing diameter of wire D. For many years it has been the practice to employ code words to identify and precisely define specific conductor constructions and designs (conductor size. method of assembly. in. formerly known as Brown & Sharpe (B&S) gage. and a diameter of 1.2732 X 10' X area in sq. mils Area. ACAR-aluminum conductor aluminum al loy-reinforced (high strength 6201-T81 wire reinforce ment). (Actual size.600 Approximate Relationships (I) An increase of three gage numbers doubles area and weight. the area in cir mils equals diameter-in-mils squared. (2) An increase of six gage numbers doubles diameter. stranding.9 10.000 cir mils has an area of n/4 sq.600 211.3-1. Brown in 1857.3-2) D = 1O-'cmil"orcmil I()6D' Thus a solid round conductor of 1. that is. cmils #10 #30 AWG Awe 10 100 101. and is now standard for wire in the United States.001 in.00 in. bare aluminum 1350 conductor. voltage rating. AAAC all-aluminum alloy-conductors (of 6201-T81). etc. in inches (Eq. 37 strand. Successive AWG numbered sizes represent the approximate reduction in diameter associated with each successive step of wire drawing.380 • #1/0 AWG #'10 AWG 324. was introduced by J.0 105.9 460. The conductors accordingly may be either lengths of single wires or a stranded group of smaller wires arranged in Nominal Diameter. Mechanical Design of Conduc:lors American Wire Gage (A WG) This wire system. Typical cross-sections ofsolid-round A WG-size wires and approximare relationships. and corrosion resistance. in. They may differ in electrical and physical properties. in this case a 1.Section II Bare Aluminum Wire and Cable Chapter 3 Engineering Design This chapter describes lbe principal design features of bare uninsulated conductors. Except as otherwise referenced. Stranded Conductors Flexibility requirements for conductors vary widely. Fig. 7/w Single layer 7/. C. Still greater flexibility of stranded conductors. and adding 96 percent of the minimum stress in the steel wires at 1. aluminum conductors that are concentric-lay stranded of 1350 or 6201 alloys in the various tempers have their rated tensile strength (or minimum rated strength) taken as the following percentages of the sum of the minimum average tensile strengths of the component wires. Typical Examples of Concentric Lay Conduc figures. this effect is more than offset by the fact that the unit tensile strength of commercially cold-drawn wire generally increases as its diameter is reduced. Two layer. as is evident by the comparison for H 19 stranded conductor in Table 3-2.001 cmil Sizes 2.or left-hand depending on whether the top wire of the helix extends to right or left as the conductor is viewed axially in the direction away from the observer. AAC/TW is a new design of all aluminum conductor composed of shaped wires (Trapezoidal) in a compact concentric-lay-stranded configuration. and adding 93 37/.000. How ever. multiplied by rating factors. This effect can reduce the total load at which the first strand breaks as compared with that of a solid conductor of equal cross section. 91. the former usually for bare-wire ov-erhead applications and the latter for covered overhead lines. The stranding arrangement of each class is also specified m ASTM Conductor Standards. (Class B) percent of the minimum stress at 1.000. Ameriean practiee (ASTM) recognizes two classes of bare concentric-lay stranded conductors. 00 of Stranded Over that of Solid Conductors Sizes 4. Wires of softer temper than the usual hard drawn wires can be used. (Class AA) 0. The length of lay is the axial length parallel to the center line of the assembled conduc tor of one turn of the helix of a single wire.} 3-2 0.594 in. two. The amount of increase for ali-alumi num conductors may be computed according to a method described in ASTM B 231. AA and A.000.1953. Concentric-Lay Stranding Incremental Increase for Weight and de Resistance Most bare power conductors are in concentric-lay stranded form. These have more wires for a given size of conductor than used for Class AA or A stranding.586 in. or four layers of aluminum 19/w wires. three. re spectively. 00 central wire or a single layer of steel wires. 93. 37/w All strengths are listed in pounds to three significant Fig. 00 .000 to 3. as below: 7 19 37 61 91 wires per conductor wires per conductor wires per conductor wires per conductor wires per conductor (and over) One layer Two layers Three layers Four layers Five layers (and over) 96% 93% 91% 90% 89% Similarly.(lllustrations are approximately to conductors. the rated strength of ACSR is obtained by ap plying rating factors of 96. Bare alu minum conductors conventionally have a right-hand lay on outside layer. or the standard increments of increase listed in Table 3·1 (also from ASTM B 231) may be used. or even finer strandings. and these strengths also apply to compact-round tors. a single straight core wire is sur rounded by one or more helically curved wires.001 emil Sizes 3. Added flexibility also may be obtained by using small braided wires or those in "bunched" arrangement. All wires of a given layer generally are of same diameter. According to ASTM Standards. All 266.000 to 2. The direc tion of twist of lay is usually reversed in adjacent layers.8 kcmil. 3-2 shows typical examples of concentric-lay stranded bare conductors for various degrees of flexibility. The direction of lay is either right.0 percent elongation if there are two layers of steel wires. .000 emil or under 4% 3% 2% DifJerences Between Stranded and Solid Conductors Because of the helical path of the strand layers there is more length of metal in a given length of stranded con ductor than in a solid round conductor of the same A WG size.000. the total cross sectional area of all component conducting wires deter mines the A WG or emil size of the assembled conductor. In ellber case. D. and 90 percent. and the properties are listed in Tables 4-10 and 4-11. hence both the weight and de resistance per unit length are increased.000. The tensile load on a conductor is not always equally diVided among the strands. 3-2.bare aluminum wire and cable TABLE 3·1 Strand Lengths VS Solid Conductor Lengths for ASTM B 231 some regular manner.0 percent elongation for cables having one Three layer. mostly used for insulated conductors. are those with Class B.1185. The design is de scribed in ASTM B 778.593 in. to the strengths of the aluminum wires of con ductors having one. that is. (Class A) scale. 0.0849. 19/. utilizing component members which are themselves either concentric stranded or bunched. 1225 1350 1410 Rope lay Concentric Stranded Conductor- Compact Concentric Stranded Conductor Expanded Core Concentric Stranded Conductor Fig. In. is also frequently used for HV or EHV lines. or may be unidirectional with all layers stranded in the same direction but with different lay lengths. 3-3. two 795 kcmil ACSR Drake under typical conditions of spacing and temperature provide 24 percent more ampacity per kcmi! than a single 1780 kcmil ACSR Chukar. and cost. Bunched members are cabled with the individual components bearing no fixed geometric relationship be tween strands. Rope-lay stranded conductors may be stranded with subsequent layers reversing in direction. are used TABLE 3-2 Strength of 1360-H19 Aluminum Conductors ISu-and AWG Stranding :Oiam. conductors made up of strands of different alloys or different materials. where the required strength is greater than the strength obtainable with I 350-H 19 grade aluminum strands. To meet varying requirements. the design advantages of bun dling are not wholly dependent upon ampacity. (2) 1350 stranded conductors reinforced by alu minum-clad steel wires which may be in the core or dis tributed throughout the cable (ACSRIAW). etc . ACSR is available 3-3 . Composite Conductors Composite conductors.2576 2 7 Strand: 0. Aluminum Conductor Steel Reinforced (A CSR) and Modifications ACSR has been in common use for more than half a century. Lb I Solid. A "bundled" conductor arrangement with two or mOre conductors in parallel.engineering design Special Conductor Constructions Large conductors requiring exceptional flexibility may be of rope-lay construction. Table 3-3 compares breaking strengths of several all-aluminum stranded con ductors with ACSR and one of hard-drawn copper. but the current carrying capacity relationship is similar.0974 2 19 Strand i 0.. The stranded cables are smoothed in a compacting operation so that the outer strands loose their circularity. Normal radio interference. expanded core concentric-lay conductor. Although the ratio of radiating area to volume increases as the individual conductor size decreases. (Fig. strength. It consists of a solid or stranded steel core Sur rounded by strands of aluminum 1350. uses fibrous Or other material to increase the diameter and increase the ratio of surface area to metal cross-section or weight.0591 Calculated from ASTM B230 and B 231. spaced a short distance apart. they provide a more economical balance between cable diameter and current carrying capacity. 3-3) Designed to minimize corona at voltages above 300 kV. but more recently as conductors became larger. (Fig. Thus. The principal eco nomic factors involved are weight. (Fig. each strand keys against its neighbor and many interstrand voids dis appear. Historically. The principal kinds of composite conductors are (I) 1350 stranded conductors reinforced by a core of steel wires (ACSR). Some cables are designed to produce a smooth outer surface and reduced overall diameter for reducing ice loads. 3-3) A similar result is commonly obtained by use of trapezoidal strands that intertie with adjacent strands to create a smooth. interlocking surface. Rope-lay stranded cables are concentric-lay stranded. Rated Strength. Or (3) 1350 stranded conductors reinforced by wires of high-strength aluminum alloy (ACAR). Typical cross-sections of some special conductor shapes. all of approximately equal d-c resistance. the amount of steel used to obtain higher strength soon increased to become a substantial portion of ACSR.• and the usual controlling design characteristics are discussed elseWhere. 3-7) Another cable design. and under some conditions wind loading. the trend has been toward use of a smaller proportion of steel.1 2 0. 3"1. Copper. This type of cable is used for lines above 300 kV. has been deleted from this edition because it is no longer commercially available. and 84/19. A description of the method of computing rated break ing strength of ACSR found in ASTM B 232 is abstracted in right-hand column of page 3-2. etc. 4517.400 394. and 2617 strandings are much used. calculated from their specified nominal wire diameter and the appropriate specified minimum average tensile strength given in ASTM Specification B 230. to be .6 370. and depends On type of stranding.3 527. having steel content of 26"1•• 26"1.luminum wires shall be taken as that percentage according w the number of layers of 1350 aluminum wires indicated in Table 4 of the sum of tne strengths of the 1350-HI9 wires. Aluminum Conductor Alloy Reinforced (ACAR) Another form of stranded composite conductor consists of 1350-H19 strands reinforced by a core or by otherwise distributed wires of higher-strength 620 1-T81 alloy. comprising a range of steel content from II "10 to 18"10. indicated in Table 4 of the sum of the strength of the aluminum wires calculated from their specified nominal wire diameter and the minimum stress as 1 percent extens.150 13.) "The rated strength of completed conductors shall be taken as the aggregate strength of the 1350 aluminum and aluminum alloy components calculated as follows. river cross ings. the most used strandings are 18/1. The ASTM approved method for determining ACAR rated strength is described in ASTM B 524 as follows: (The mentioned Table 4 is that of ASTM B 524. in a wide range of steel content-from 7"1. 54/7. The inner-core wires of ACSR may be of zinc-coated (galvanized) steel. are used mostly for overhead ground wires.666 0.OCk for H. 3·4 differs from that stated in Table 3-\.600 i I Type ! 1350-H19 6201-T81 ACSR HD Copper I : ! Relative ! Weight Ib per fI Rated Breaking Strength fb Strength 0/0 315.D. 8% for steel. Expanded ACSR.9 1000 : I Condue tance i 102. according to the number of layers of aluminum alloy wires.741 0. The apparent conductivity of ACSRI AW rein forcement wire is 20. available in standard weight Class A coating or heavier coatings of Class B or Class C thick neSSes. ACSRlfW is a new design of ACSR composed of shaped aluminum wires (Trapezoidal) stranded around a standard steel core. because of stranding of ACSR.300 9. Resistances are based on IACS. It is fully described in ASTM B 779 and Tables 4-19 to 4·22. is a conductor the diameter of which has been increased or expanded by aluminum skeletal wires between the steel core and the outer aluminum layers. Class B coatings are about twice the thickness of Class A and Class C coatings about three times as thick as Class A. 8/1.ion. 3-4. The latter produces a conductor designated as ACSRI AW in which the aluminum cladding comprises 25 percent of the area of the wire. Table V of B232 is reproduced on next page as Table 3-4A. Typical stranding arrangements for ACSR and high strength ACSR are depicted in Fig.0514 0. Galvanized or aluminized coats are thin.500 336. The strength contribution of the aluminum aHoy wires shall be taken as that percentage. with a minimum coating thickness of 10 percent of overall radius.0502 0. Today.721 0.0 102.154 35. (lACS). de Re sistance Ohms per 1000 fI at 20'C 19 19 30/7 7 0. and 97..522 0. In.1 653.400 211.0516 ! ! Size emil 336. This shall be considered. 5005 H19.0 52.300 17. and for the moderatelY higher strength ACSR 54/19. extra long spans. The amount of increase also may be com puted according to a method described in ASTM B232. The strength contribution oftbe 1350 a. The incremental increase for dc resistance over that of solid round conductors. 3-6. The conduc· tivity of these thin-coated core wires is about 8 percent (lACS). for the larger-than-AWG sizes. Fig.3 6.bare aluminum wire and cable TABLE 3-3 Comparison of Properties of Typical ACSR Conductor With Those of Similar All-Aluminum and Hard-Crawn Copper Stranded Conductors' ! Stranding Diam. by weight for the 36/1 stranding to 40"10 for the 3017. and 31 "I" respectively.8 100.2% for 135Q. and are ap plied to reduce corrosion of the steel wires. 7217.H19.4 101.6 76. 1217 and 16/19 strandings.8 'Abstracted from ASTM Standards and industry sources. The inner cores may also be of aluminum coated (aluminized) steel or aluminum-clad steel. The reinforcing wires may be in a central core or distributed throughout the cable.5% for 6201~T81.% conductiVities of 61. The high-strength ACSR.8 100. although included in earli€r editions of this handbook.0511 0. 52. . ASTM B 232) % de Resistance Stranding % de Resistance I 42 AI/19 S. of Electrical Resistance of Aluminum Wires in ACSR of Various Strandings (Table 5. 6/1 18 AliI S. Aluminum Alloy Reinforced (ACAR) (Referenced in ASTM B 524 as Table 4) Stranding 30 AI/19 S. 45 AI17S. layers are considered to be full layers for each material. thereby obtaining a range of strength-conductance properties be- 54 AI/19 S. 54 AI17 S.5 1-5 2. 12 AliI S.0 2. 3-4. TABLE 3-4B Strength Rating Factors Extm.0 2. 1.5 2. Typical stranding arrangements of aluminum cable steel-reinforced (ACSR).75 3. 21 AIl37 S. Rated strength and breaking strength values shall be rounded-off to three significant figures in the final value only.vidual wires. 30 AI!7 S.75 7/1 8/1 18/1 36/1 1217 2417 2617 30/7 : i 4217 4517 4817 5417 72/7 16/19 30/19 54/19 2.engineering design @ @ 6 AI!1 S..ct from ASTM Specification B 524 for Concentric-Lay-Stranded Aluminum Conductors.0 2. 7 AliI S. 26 AI!7 S. 38 AII19 S.5 3. For purposes of determining strength rating factors. TABLE 3-4A Increase. . Numbe r of Wires Number of Layers'" 1350 1350 6201·1'81 620I·T81 Rating Factor.5 2. mixed 3-5 . ~ ® 8 AliI S." Because the 6201-T81 reinforcement wires in ACAR may be used in the core and/or for replacement of some of the J350-H19 wires in the strands. 5 AI!1 S. 6 AI!7 S.0 2.0 84/19 3. 24 AI!7 S. 16 Ali19 S.5 2.5 2. Percent.0 The above resistance factors also are usuaUy taken into account In tables of de resistance for ACSR. per <enl 1350 6201-1'81 % % % 4 15 12 3 4 7 I 96 2 93 33 30 4 3 7 2 13 2 19 1 3 3 2 2 24 18 54 48 42 33 28 72 '9 7 13 19 63 28 54 37 % 3 3 2 91 96 93 93 96 1 2 2 96 2 91 91 2 3 2 3 3 93 93 9' 91 93 93 93 % 93 93 91 93 91 91 .5 2.5 2.0 76/19 3. 95 percent of the minimum average tensile strength specified for the wire diameter in Table 2 of ASTM Specification B 398. Fig. i Stranding 36 AliI S. almost any desired ratio of reinforcement 1350-H19 wires is achieved.5 2. The conductor size and ampacity for any arrangement depends On the size of the ind. . 800 24.T81 alloy.100 25. 3-6 . diameter the strength-weight ratios are as shown: (the strengths are slightly higher ifsmaller wires are usedJ_ The strengthlwt_ ratios compare rated strength per ASTM B 524 and conductor weight in Iblft. Typical stranding arrangements of aluminum cable alloy-reinforced (A CAR).bare aluminum wire and cable o ~ KEY 1350-H1g wire 6201-T81 wire 4-1350 3-6201 3-1350 4-6201 12-1350 7-6201 15-1350 4-6201 30-1350 7-6201 24-1350 13-6201 18-1350 9-6201 54-1350 7-6201 48-1350 13-6201 42-1350 19-6201 Stranding Strength/ Wt ratio Stranding Strength/ Wt ratio Stranding Strength/ Wt ratio 4/3 15/4 1217 26. 3-5.500 20. and that individual wires are larger than 0. Assuming the reinforcement is 6201.600 23.100 3017 24/13 18/19 21.000 22.100 26.200 Fig.150 in.800 48/13 42119 5417 21. 3-6.02048 1. The size shown is 1595 kcmi!.168" ALUMINUM WIRES -L. diameter 1 ft long. thus. This constant is sometimes multiplied by 1000 which provides ohms per 1000 ft..H. LAY &. lACS. Fig. two volume resistivity constants' are used (Table 3-5): 1. LAY W pw = .lft.75 in. 2. by inverting the p. terms of percent International Annealed Copper Standard (lACS) instead of in mhos (the unit of conductance).4CSR is 1.fRTl" STEEL WIRES Weight Resistivity = W • x 0.168" ALUMINUM WIRES·R.0% lACS 620I-T-81 52.-.H. as below.54 in.as W the case may be. LAY (Eq. "The resistivity constants are based on ohms when conductor is at AST:M Standard temperature of 20°C (68 F).02015 1. Some tables are based on temperaLUfe of25"C. in cross-sectional area and 1 ft long. If so.H. R PwL' --. representing the resistance in ohms of a round conductor 0. OD is 1. from Eq. and resistance. length. 34) L equation. Air-Expanded .001 in.L 24 x 0. The rating factors for various strandings of ACAR using 6201-T81 reinforcing wires are shown herewith as extracted from ASTM B 524.0% lACS B5!l-H 19 6]. new resistivity constrants can be computed for 25"C if considerable work is to be done (see Table 3~7). They are used as the basis for calculating the properties of ACAR listed in Chap ter 4. 3-3) L II = Cross-sectional area L=Length R = Resistance 19 x O. and if these units are used consistently R may be obtained for any A.5% lACS by 1. representing the resistance in ohms of a conductor of I sq in. Composite conductors similar to A CSR also may be manufactured by using trapezoidally shaped strands as shown above for selfdamping conductor. International Annealed Copper Standard [n 1913 the International Electro-Technical Commis Fig. The diameter of equivalent regular . or a temperature coefficient can be applied to the 20"C value of R"c to obtain that for 25"C. For USA practice. LAY 30 x 0. Ohm-sq in. or W. Commercial hard drawn copper conductor is considered as having conductivity of 97"l.. sion established an annealed copper standard (lACS) which in terms of weight resistivity specifies the resistance of a copper wire I meter long that weighs one gram. Fig.4)( 0.1591" ALUMINUM WIRES ·R. 3-7.4CSR.2R in which = Weight These resistivity constants may be stated in whatever form is required by the units used for area.01734 3·7 . Ohm-cmillft. L.1591" ALUMINUM WIRES -LH.R in which (Eq.engineering design tween constructions of all 1350-H19 wires or those of all 6201-T81 wires. Resistivity is expressed as follows: Calculation of dc Resistance Volume Resistivity = USA practice is to exptess conductor conductivity in II pv = . weight.or --=. 3-5 depicts several stranding ar rangements of ACAR cables of 1350-HI9 and 6201-T81 wires. 3-3. Multiply the 20" value 135!l-HI9 62. 754 0.)] (Eq.33 0.013310 435.00404 Over a moderate temperature range (OCC to 120CC) the resistance of a conductor increases lineatly with in crease of temperature. [1 (T. D.2% lACS con ductivity. by H. see ASTM B 193. thus R.27 HD Copper 97.04007 Alumoweld 20.7.0083974 •Abstracted and calculated from ASTM Standards.. . E.2 0.13 507. = R.. = =.01777 0..1 in which"" 0: . Table 3.01 0. = Resistance at temperature T. For stranded conductors. or may be read directly from Table 3-7.015515 51.500 It is customary to compute the conductor resistance from known resistance at 20¢C (68 ¢F). 3-5 it is apparent that the temperature co efficient for 20 D C cannot be used when the known re sistance is at some other temperature. coefficient ofresistance at T.00404. .946 0. ohms 1. 3R5280XI6.946xl.0 Steel 902.64 0. Temperature coefficients for 20°C resistance values are in Table 3-6. House and P.0200883 AI PP YlI'lg reSistivity factor from Table ·5.10182 9574. 0:: $l for 1350 {6L2~o Applying Eq..T..0 10. 3-8 + (Tx - Calculation of ac Resistance* Skin effect is by convention regarded as inherent in the conductor itself. [win. For a complete listing of the formulas covering these resistivity relationships. The net driving emf at the ·Reports of resistance and Kvar reactive requirements For large-sizr conductors (single. Temperature-Resistance Coefficients for Various Temperatures From Eq.033. February 1958. plus an increment that reflects the increased ap-.QQ)6() 1 ----+(50-20) 0. and expanded core} are in AlEE paper 59~897 power Appar(lW$ (md Systems. These papers also refer extensively to th(' effect on ampadty of wind velocity transmission~Une and temperature rise. Some tables.02817 1350·H19 61. .... "" = Skin effect results in a decrease of current density to ward the center of a cylindrical conductor (the current tends to crowd to the surface).03284 0.5 19.24 6201·T81 52. = Resistance at temperature T.3·5) + "" in which R.500 emil area of 1350 of 61..08481 3191.... hence when the ac resistance of a con ductor is stated. resistance values obtained by use of these factors are to be increased by the stranding-increment ratio. per Table 3·1 for all aluminum conductors. coefficient at Tx deg C. (Eq3-6) 20) = Temp. What is it for 509 C? Change of dc Resistance with Temperature For coefficients for other temperatures see Table ).2 8. Tuttle. allowing 2% stranding increment.. Example: Find de resistance at 20'C of one mile of Bluebell cable of 1. by Earl Hazan and AlEE paper 58·41 Curren(~Ca")'ing C(lpacity oj ACSR. however. parent resistance in the conductor caused solely by the skin-effect inequality of current density. Docember 1959.692 0. Temp. 3·6 1 "'so = . what is meant is the de resistance usually in ohms.bare aluminum wire and cable TABLE 3-5 Equivalent Direct Current (de) Resistivity Values for Aluminum Wire Alloys at 20'C' Volume Conductivity percent lACS Alloy Weight Ohm-emil per ft Volume Resistivity Ohm-mm 2 per m Resistivity Ohms-in2 per 1000 ft Ohms-Ib per mile2 16.033..21552 0. = Temperature coefficient at 20"C A longitudinal element of the conductor near center is surrounded by more magnetic lines of force than is an element near the rim. Example: The 200C temperature coefficient lACS) alloy is 0. R. hence the induced counter-emf is greater in the center element.0 129.. O. Fat this condition 1 "'x = . or per Table 3-4A for ACSR. specify resistance at 25°C which are related to lO'C values by the factors in footnote on page 3-7. ' . 3-9 and Table 3-8A. The ):>asic calcula\ions of R"/R. "I:he comparison at 75010 loading.00404 (50-20)1 =0. What are the ratios for load currents of 200. as stated.. at m"C per degree C 61. if the distance apart of the conductors exceeds ten times the diameter of a conductor the extra I'R loss Skin Effect in Steel-Reinforced Stranded Conductors (ACSR. and these values can be obtained from curves based on such calcu lations or tests..IR".5 kcmil size and to about 1.). However.1lll83 [1 + 0. What i. and multiplying these values by the basic ratio provides the desired ratio in col. it usually is more con~ venient to use diameters which ordinarily can be" read from conductor tables.0 0. Accepted catalog data for most commercial designs are available.. Some tables include the effect of core conductance./R d . ratio will vary with current.5 kcmll has Ra~/R(l~ ratio of 1.025 at 25 0 C.. see footnote. For use' of the curves of Fig. If the number of aluminum layers is odd (1. The Rae/Ru. tS) of Table 3-8.) The R. similarly has the R"/R". R". Rae is then obtained from the R. The effect is considerable in one-layer conductors. 800. their mutual induc tance affects the current distribution in each conductor.2% lACS) has de resistance of 0./Ru.28)]'/. 3·9. ratio have been made for round wires and tubes of solid material.ir" = 0. 1. (3). and they also may be ap plied for stranded conductors by treating the stranded cro~ section as if it were spHd. Three-layer ACSR. suits. ratio of ACSR conductors that have an ·As fo/rn equals ratio of diameters. 3-8. Proximity Effect When two conductors are spaced relatively close to one another and carry alternating current. From the upper curve of Fig. mod erate in 3-layer conductors. Example: All·aluminum Bluebell stranded conductor of 1350-H19 (61.0188 ohms per 1000 II at 5<fC.) is almost unity for small aU-aluminum conductors at power frequencies. hence show a slight variation of ratio.09 in the 1590 kcmi! size. without regard to core magnetic effect. or in which the steel is sur rounded by a thick aluminum coating is almost impos sible except for the simplest configurations. However. This effect is further de scribed and illustrated by Fig.1 -"C 24...0188 x 5. ratios for solid round or tubular conductors..0883 ohms. is the external radius. The one-layer ACSR may be less desirable electrically and it is used mostly where high strength is required at the sacrifice of conductance and for small sizes..4 etc..00360 0.00347 0.5 97. values are tabulated in col..2% (lACS) 1350-H19 at 20(>C . The ratio of ac resistance to de resistance (R. regardless of load current. Curlew of 1033.) may be estimated from the curves of Fig.33 9. ratio read from the chart. 600. hence the R.0990 ohms center element is thus reduced with consequent reduction of current density.is 0. the effect may be allowed for by applying values from Fig.of core permeability in the one-layer ACSR whereas it has no effect in 2-layer ACSR.031. 400.. shown in Table 3-8A illustrates the effe~ . and r.0 20. Abscissa parameter./Rd . and it may be disregarded for 5-layer conductors and more. etc. 3-9 . In such conductors the core flux varies with load current. and 1000 amp. 3-9 which shows the correction factor to be applied to tbe ratio with varying load. Fig. ratios for one-layer ACSR are obtained from tables or curves that show test results at various load currents./Ru. Calculation of skin-effect ratios for composite designs in which the steel reinforcement is located whoUy or partly away from the central core. the Roo/Rue ratio for ACSR conductors is affected by the magnetic flux in the core. Consequently such values are taken from tables that represent test r. provided To is the radius of the Core and r. ratio affected by load current.3. is first obtained and corrected for temperatore. Table 3-S. 60 Hz.00. which compares with a value from pubJlshed tables of 1:ti30.. It increases to about 1.00361 0. [60/(0. no account is taken of the current in the steel core.00404 0.· respectively? See also footnote under an Table 3-8. which occurs because there is an unbalance of mmf due to opposite spiraling of adjacent layers. Substituting in equation at bottom of Fig. 3-8. Example: A 54/7 ACSR conductor. etc./Rd~ ratio for 60 Hz? even number of layers of aluminum wires (2.engineering design TABLE 3-6 Temperature Coefficients of dc Resistance of Wire Materials C( x 20"C (68' F) (Abstracted from ASTM Standards) Conductivity Percent lACS Material Aluminum 1350-H19 6201-T61 Copper (h-d) Alumoweid Steel Temperature Coefficlent oc ..6 and R IRdI.' By this method. What is its approximate Ra.04 for the 1113. . 4/0 and under. 3-8 on basis of ohms per mile.. 3-8 shows R.2 52.:.00320 Example: The resistance of one mile of Bluebell stranded conductor of 61. it at 500C? Applying coefficient from Table 3·6 R50 =0. 00398 .025 1.025 1.025 1.048 1. Conductor Hysteresis and Eddy Current EfJects (4).00324 .00314 . Correc1lld Ratio (3) x (4) ! I i 1.0990 [I + 0.bare aluminum wire and cable TABLE 3-7 Temperature Coefficients of dc Resistance of Wire Materials at Various Temperatures· Alloy Conductivity TempoC 1350-H19 61. They are only important in large ampacity conductors when magnetic material is used in suspension and dead end clamps.038 1.00272 0 10 20 25 30 40 50 60 70 80 90 100 'Calculated per NBS Handbook .00389 . What is it at 200c? Applying the 5()0 coefficient from Table 3-7 in Eq. Constants are available from the Aluminum Association that facilitate this adjustment of R.0990 ohms. (5) (2) (3) (1) Load amp Amps per emil x 106 Resistance multiplier Fig.00315 .025 1. etc. so no separate estimate of them is ordinarily re quired.00404 . The calculation of eddy-current and hysteresis loss in adjacent metallic materials. Usual tests that determine R"/R.00361 [20 . the operating temperature will increase with load. To supplY these losses.) Or its estimate by tests is beyond the scope of this book.00348 .018 1.025 715 960 .c/Roc ratio.00440 . or similar items which are closely adjacent to the conductor. hence ordi TABLE 3-8 Comparison of Basic and Corrected RaclRdc Curlew narily can be neglected.00373 .044 1. 3-7 Basic RaclRdc Ratio 200 400 600 800 1000 194 388 581 1.025 1.5% lACS . 3-5: R20 = 0. (structures. 3-10 Hysteresis and eddy current losses in conductors and adjacent metallic parts add to the effective a-c resistance.022 1.lOR Example: The resinanee of one mile of Bluebell stranded conductor of 1350-Hl9 alloy at SOOC is measured at 0. housings.00287 ..00359 .00347 .00374 .2% lACS 6201-T81 52. ratios for conductors as reported in tables of properties take into account any hysteresis or eddy-current loss that is in the conductor itself.032 1.00305 .00279 . Radiation Loss This component of power loss in a conductor is negligi .013 1.SOli = 0. more power is required from the line.0883 ohms.00361 .00325 .00336 . caused by this crowding is less than I percent.00306 .007 1. hence the basic Rac/Rdc ratio must be adjusted to reflect the variation of Rdc with temperature.00335 .00341 .00421 .00296 .051 *If these current variations occur in a conductor when ambient temperature is constant. ... I .76 Tn I ~=OBO Tn I To -=0. o f I I i 'f r I I I CONDUCTOR CROSS UCTION 1&1 /V I Tn I 1 I / f I '/ / / V I / / 1)1 / / / /I.1-1' 1.. D V 60 !Rdc Rdc in ohms per mile I ~~=O921 Fig...= 050 1 ) f... / / / II J VI I I / V / 1// / / / / / / / fJ"I / I ../ . oct t )% III III: 1. / / / :.B81 / / // ~ Tn . 3-11 .30 ao 10 / / ....engineering design I II Tn ~=O. ~ /~ /.08 ij 1 f.11 o t- To -_0.. B.. ~::::_ r ~=O90 :::- a.. I II TO 1&1 ~ V Z .01 / / ~ .07 I V oct .00 I /0~_0'01 /J V III - II t. "1923.OO I '0 . / ~ f. Woght. . " '/ / / / 'l '/. .-:: 1.=010 I 1.82 Tn I ~=o. H.20 Tn 1 . Skin-eDect factor for solid-round or tubular conductor at 60 Hz.. o Tn . 3·8..=OhO I II !!!=0. "Skin £JIm in Tubu/wand Flllt Cf»fdu<t()l'J.""U I ~=0.84 Tn I / II 1 V I I I '/ / / // / I Q 1.70 Tn I To -=0...14 I ~:::O... + 0.+ 0. are considered herein. 345 i:V and above. among them leakage reactance of apparatus. and at unity power factor is I 'For further information regarding corona.42 0. Corona" Corona oCcurs when the potential of the conductor is such that the dielectric strength of the surrounding air is exceeded. L also is defined by e = L (dildt) in which dildt indicates the rate of change of current with time. to neutral I = Current in conductor. An ex. The quantity X=2"f L. being more pronounced where there are irregularities of the conductor surface. it becomes important only at radio and higher frequencies.bare aluminum wire and cable TABLE 3-SA Comparison of R. The total system reactance also In cludes many factors not related to the conductors. i Reference Book. 3-12 . and their consideration is beyond the scope of this book.350 0. both expressed in absolute units. either as parts of a single-phase or a three-phase circuit. Only the reactances that are related to the conductors..2% lACS 7 ACSR (1 layer) 6. but the 90° out-of phase voltage and current must be supplied to sustain the magnetic and electric fields created. Bundled conductors are frequently used to obtain lower voltage stress on the air insulation for voltages above 3S0kV. These system conditions are taken into account as a part of circuit analysis for which a high degree of electrical engineering skill is required. 266. Inductance and capacitance. volts. McGraw-HiH Company. The discharge is accompanied by the odor of ozone.384 1.S kcmi!.384 ! ACSR (2 layer) 26.350 0. but negli gible capacitance. either as alternating current or as a transient of any kind. Inductive and Capacitive Reactance Variable current flow in an electrical conductor. or adjacent carrier and signal circuits. 14 which alSo contains references to the varioUs n:search paperS.349 Resistance RacfRck i 1..7 0. 60 Hz Ratio 0. and there may be a hissing sound.. dc E/ (R + jX) in which.364 RKiR. and the extent that automatic tap-changing and power·factor control are used. Sec. L is the coefficient of proponionality. influence system stability in high-voltage lines to a greater extent than re sistance.005 0.:eUem text on corona and EHV line design is the EPRI Transmission Line . amp ohms .7 . that is. expressed in ohms~ but in phasor notation the inductive-reactance drop is perpendicular to the resistllnce drop. dc ! 60 Hz 0.IR•• Ratios for All-Aluminum and ASCR. X = Inductive reactance.349 I 0. the current I in a conductor having both resistance and inductive reactance.366 1. The air becomes ionized and bluish illu minated gaseous tufts or streamers appear around the conductor. and e is the momentary induced voltage.3-7) E = Emf. however. gives rise to the parameters of inductance (usually expressed in millihenrys) and capacitance (usually expressed in micro farads) and their related properties of inductive and capacitive reactance.ductive reactance.349 0. = Vector operator (-1)'" (Eq. Single-Layer Conductors. is the in.00 of I'R loss in the conductors occurs because of them. ! i 0.364 1.545 1. Corona discharge from a bare conductor power line may interfere with radio and TV reception. so a slight increase 1. respectively. see Standard HandboQk for Electrical Engineers. usually expressed as ohms per mile and megohm-niiles.349 ble at usual power frequencies. Accordingly no method of estimating such loss is considered herein. No energy loss is asso ciated directly with these parameters.. 61. Inductiye Reactance The inductance L of a circuit is a measure of the number of interlinkages of unit electric current with lines of magnetic flux produced by the current. and Equivalent 2-Layer Conductor Resistance value in ohms per mile Light Load at 25°C 75% Load at WC Resistance Conductor Stranding 1350·H19. in which I is frequency in Hz. 77. If the spacing is unequal. inductive reactance of the conductor X under usual load conditions. may be obtained by methods later described.-. is an inherent conductor electrical property. Conductor spacing D for 3-phase circuits is the geo metric mean distance (GMD) as later defined. The inductive reactances discussed herein and listed in tables of conductor properties are suitable for calculations of either positive. taking into account the reactance due to the flux out to a distance of 1 ft from center of the conductor. on the basis of unit lengths. the GMD is a geometric average value which. Tuttle.. and are un related to size of an individual conductor../ / V /'" / V ~ / . and composite con ductors. thus. + + Numerically (R jX) = (R' X2)14 and is desig nated impedance. D. these ftlCtors also may be used for aluminum of 61. Simplifying of reactance calculations is effected if the reactance is considered to be split into two terms • ( I ) that due to flux within a radius of 1 ft (X. The values also are useful as a basis for calcu lating impedance under fault conditions (zero-sequence). X.. stranded. Without significant error. Tables are set up in this manner.- ".. _1 54 / 7 strondingl 54/19 . A further simplifying convention is that the tabulation of the latter distance is the distance between centers of the two conductors instead of the distance from one-foot radius of One conductor to * First proposed by W.01 . Thus. AlEE. in a flat 3·13 . and is so tabulated for round.10. Zero-sequence values.. thus. Lewis and P. Resistance multiplying factors for tktee-layer ACSR for aluminum conductivity of 62%. Part IU. The value for any other frequency is directly proportional. 3-9. These data are used to reflect the increase in resistance due to magnetizing effects of the core.. usually one mile.. See also W. A. depend on spacing of the conductors. Inasmuch as zero-sequence inductive reactance is the principal factor that limits phase-to-ground fault currents. Table 3-9 lists values of X. the surface of the adjacent one.. The Resistance and Reactance of Aluminum Con ductors. Normally. 1958. at 60 Hz based on separation distance between centers of the conductors. The conductor spacing for other than a simple two-con ductor circuit is its geometric mean distance (GMD) in ft.engineering design 1. usually is satisfactory for preliminary calculations. as em ployed for usual transmission and distribution circuits. It is to be noted that X. however. and (2) that due to the flux between 1 ft radius and the center of the equivalent return conductor-(X. also expressed in ohms. in ohms per mile..Or negative-sequence reactance. A. 200 400 600 800 1000 - rn 1200 . Lewis. Trans...) is the required The sum of the two terms (X. A few of the usual arrangements and their GMD's are shown in Table 3.. The values of X" how ever. ~.2% lACS conductivity.03 1... there will be minus X" values tabulated for distance between conductors that are less than 1 ft apart.). Steel Rein/orced. usually as ohms per mile. . as required for unbalanced condi tions or fault-currents.. its value is important in conductor selection.) including the internal reactance within the conductor. .04 1. for convenience. computations of R and X for transmission lines are made.- .+5/7 strandingl • - 1400 1600 60 HZ AMPERES PER MilLION eMil OF ALUMINUM AREA CURRENT DENSITY Fig.. for 25 Hz it is 25/60 of the 60-Hz value. Vol. {I) From formula: at 60 Hz Xd .2666 0.3953 0.4445 0. each ring being a specified G MD apart.3-8) GMR in which X.1399 0.3015 0.1491 0.1973 0.1604 0.0492 -0.2390 0.4584 0.2347 0.2910 0.3112 0.bare aluminum wire and cable TABLE 3·9 Separation Component (X.4243 0.0789 0.2485 0.1682 0. 7 ft between Band C. = 0.3507 0.1152 0.4382 0.4722 3·14 1 2 3 4 5 I 6 I 7 9 8 10 I 11 -0.2194 - j 60 1 loglo . X. Hz GMR = Geometric mean radius.0097 0.0654 -0. Or 7.1912 0..0187 0.1891 0.- (Eq.1825 0.0271 0. feet 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 • 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 - 0 0.2207 0.0106 0.1549 0.0423 0.4348 0.2140 1 0. e.1461 0.0349 -0.2472 0.3751 0. .1682 -0. and C with 5 ft between A and e.1062 -0.0492 0.3805 0. and 12 ft between A and C.3906 0.1657 0. = Inductive reactance to 1 ft radius.0679 0. 2332 1 0.2794 0.2458 0. 0.1631 0.1756 0.Q735 0.1112 0.2157 0.4697 0. which represents the radius of an infinitely thin tube the inductance of which under the same current loading equals that of the conductor.1299 0..4619 0.4592 0.2123 0.2"!.1264 0.3856 0.0620 0. Westinghouse Electric Corporation.2191 0.1802 0. in which r is radius of conductor in ft.0221" -0. 1964.0891 0.1366 0.1779 0. Xa and Geometric Mean Radius (GMR) The calculation of inductive reactance to a radius of 1 ft (X.2317 0.) of Inductive Reactance at 60 Hz (1) Ohms per Conductor per Mile Separation of Conductors Inch.1847 0.0568 0. The GMR of a stranded conductor without steel rein forcement or center voids is obtained by using the concept of concentric rings of solid round wires.2069 0.2431 From: Electrical Transmission and Distribu~ tion Reference Book. ohms/mile I = Frequency.2794 10gl 0 d d = separation in feet 3-phase arrangement of conductors A.2302 0.0938 0.0841 0.2174 -0.1520 0. * The GMR of a stranded multi-layer ACSR or an ex panded all-aluminum conductor with hollow center is *FOr methods of calculation see reL at bottom of page 3-13.) is aided by the factor GMR.2445 0.4414 0.1430 0.2174 0.0841 -0.4646 0. ft The GMR of a single solid round conductor is 0.4127 0.3364 0.3694 0.2050 0.4279 0.2224 0.3438 0. 3-10 is a curve showing GMR for an annular ring.3573 0.4043 0.1028 0.2287 0.4506 0.3286 0.3635 0.2240 0.4167 0.1869 0. the reactance voltage drop from any conductor to neutral does not vary more rhan 2.0349 0.3999 0. For non-magnetic materials.2418 0.1732 0.5 ft.4672 0.1333 -0.2511 0.2361 0.3015 -0.1707 0.1788r.1071 0.1953 0.4086 0.4476 0.2012 0. from the voltage based on average D (A x B x C) A.2087 0.1190 0.4535 0.4314 0.2031 0.1993 0.0984 0.2404 0.2105 0.2256 0.1227 0.1577 0. Fig.2498 0.2376 0.2523 0.1933 0.2271 0.1333 0.3202 0.4205 0. "Efe"Jlk Prr~r Trorlsmi. . Right Triangle similarly based on the assumption of a hollow tube of aluminum wires.8 .170 in.S5 8 / I / .263 ohms per mile X. Cbeck tbe X" value. hence Avg GMDis (6 x 8 x 14)'" = 8. OF INSIDE.5 .3 . Tbe GMR values (in ft) for tbe various kinds of con ductors are listed as an electrical property of the conductor in the conductor tables herein. values for tbese conductors are experimentally determined and made available in tables or curves for various currents and temperatures. r. Interpolating in Table 3·9 and from conductor table (assuming Bluebell) Total inductive reactance of any conductor X.) is listed witb GMR as 0. = 0.662 ohms per mile 3-15 . E"""'" C L F. GMD 0.. WoQ</rttjJ. GMR of annular rings. o . Tbe X. 8 ft 8 to C.122 A ~ C 1 Unequal Triangle • A • • B C • II ].:yAxaxc Example: A 115-kv 3-phase flat-arranged drcuit has 6 ft A to B.399 ohms per mile at 60 Hz.90 I GMR r..6 . d / 0.95 CONDUCTOR GEOMETRY / . as 0. The following examples show the application of some of the previous equations and the comparative magnitude of some of the relationships.5 kcIflii stranded aluminum cable (overall diam.4 . Bluebell 1033. A or B or C A C 1.26 A Symmetrical Flat • A.n68 0.7 .1 . values for 3-1ayer ACSR is So little affected by the variable core magnetization that it is customary to ignore it.0 r.engineering design 1.2 . I / I I 0. = 0.si(jff (In(J Dt:Wribulrol'l. GMD . and bow much it differs from that of a solid round con· ductor of the same diameter. bence the GMR values for 3-layer ACSR are included in tables of conductor properties in the same manner as are those of other multi-layer conductors.0373 ft and X.0 TABLE 3·10 I / Values of Geometric Mean Distance. !yJ8. is affected by the cyclic magnetic flux wbicb in turn is dependent on current and tempera ture. 2= RATIO r.399 ohms per mile X = 0.75 d . 3·10. R:AOIUS TO OUTSIDE RADIUS Fig. • B C AX BXC • • Unsymmetrical Flat -. 1.9 1.60 V V 0. Tbe X. and 14 ft A to C. / 0. The GMR values for single-layer ACSR are not con stant because the X. / .76 ft. . . in which X. or 4 subconductors but the distance between the conductors of a phase group is small compared with the distance between centers of the groups. diam.4917 x:. for any such arrangement. because of the hollow-tube effect and increased diameter.5 ft is 0. an average of all Xd values for all dis tances between individual conductors is obtained. -:. for 1.642 0..4476) = 0.(m-l) X)] where m is the number of sub conductors 10 each group. as per Eq. 3-8 footnote. . Code Drake. Owl 617 0. flows to ground. ~r -.5~ ~'<J\ .7788 X + 0. 1. 3-8. 3-9) p.0. 2617 stranding. The variation of X. according to standard tables of electrical properties.489 layer The increased diameter of Partridge as compared with that of Daisy shows that X. . The design of such a bundled-conductor circuit is beyond the scope of this book.1002 ohms per mile. and skin and proximity effects are negligible.385 and GMR of 0.0492 The average X. provided the in dividual conductors are the same size.0492 0. thereby showing the reduction of X.55 @ 400 amps 0. of Drake is 0.. as follows: (to) in ohms per mile and X. The influence of the earth return can be given by two additional terms.0373 1. of 0. 0. when fully loaded.760 (~) R.. However. Zero-sequence currents are the three components of unbalanced phase currents that are equal in magnitude and common in phase.2794 log. for 3 subconductors = [\13(0. Thus. the same group arrangement is used for all phases. = approx 2. • • ~1. 3.465 Stranding All-aluminum Code Daisy AAC ACSRone- layer ACSR two- l<Aile 0.~1 As the distance between groups is compara tively large..1002 + 0.(rn-!) X)] + X. in the example there are 27 such distances.3915 ohms 3 per mile. if p. For 4 subconductors.4191 (to) log. 6O-Hz. Curlew. X. A corresponding size of ACSR. ibid. An X. 20 ft. If a more accurate value of is desired (usually when distances within a group are not small as compared with phase distances).50 @ 200 amps O.48@Damp' Partridge 2617 0.(. Comparison with solid round GMR = 0. = 0. The total inductive reactance of a single group X: + is thus X = X~ ohms per mile.. 0.0105 Hence.399 .(0. but the one layer Owl has 18 % greater X. Zero-Sequence Resistance and Inductive Reactance Zero-sequence currents (/0) that occur under fault con ditions are all equal and in phase.0380 X.2794 X 10glO 1 0.' Example: Consider the arrangement below in which each conductor is ACSR m kcmii.399 which checks table. = 0.~----20~1----~.888 ohms per mile at 60 Hz. Note that I. and divided by 27 to obtain an average X~.0492) = 0. each of the individual phase lines is sometimes subdivided into 2.(2)0. Inductive Reactance of Bundled Conductors For increasing load stability and power capability in high-voltage lines.0492 ohms per mile (see Table 3-9).3915 = 0. 77. then totaled.0420 ft. = X. and 3 I. is [(11m (X. is listed with X. respectively. of a phase is 1/3 (0. an approximation for for a single group is made by conSidering the inter-conductor distances d as 20 ft.8 kcmi! conductors: X. is taken at 100 (see Table 3-11) (Eq..397 0. . is shown below for 266.2858 (Eq. Kind af Cable Ohms per 1 Overall diameter 0.0492)] = 0. an earth resistance and reactance.3635 0. Hence they move out simultaneously through the phase conductors and return either through the earth or a combination of earth and ground-wire return paths. the inductive reactances may be found as per the following example. p.399 ohms per mile 1 0. 0.633 0. is reduced 5%. ----•• 1~.0492 ohms per mile. b + X: = 0. flows in each phase conductor.3635 0. ':j . value from Table 3-9 is obtained for each of these distances. for different cable constructions of the same size. whence from Table 3-9. and 40 ft.170 0.3-1O) • See also AlEE papers 58-41 and 59-897.586 in. "'1.-----20~1 3·16 • • + The reactance to I ft radius X~ for any group of 2 or 3 subconductors is [(lIm) (X. b 1 Xc = .bare aluminum wire and cable Check of X.246 in.0380 ft X: 2X12 = X. .E 3-11 of a single conductor. Rill:< 0.726 J5~ From Eq. ground wires. but an average value of 100 may be used in the absence of definite information. 1 = --"---ohms (Eq.3566)) ohms! mile 0.?8SS* X'l 2.3286 + 004127) = 0. and is in the range shown in Table 3-11.050 f t 1 X.888.(0.3286 + 0. . X. usually for 60 Hz. !l) From formulas: He = 0. 3-9 and 3-10 above total capacitive reactance similarly may be divided into X. Shunt Capacilive Reactance -L log 77. "TroMmiman and DisltifxllicfI Hruvibwk. and X t = 2. In long high-voltage transmission lines the distributed capacitance caused by the electric field between and sur rounding the conductors can attain high values which markedly affect circuit properties.399 -2(0.600 3.000 10. j (X. not including ca pacitance effects.engineering design TABI. I = .001805 megohms (1805 ohms).888 3. is Similar to the use of X a to represent inductive reactance Z. lightning performance. 0. f is frequency Hz. the zero-sequence reactance and impedance 795 kcmil 54/7 ACSR at a phase spacing of 20 ft.181 3. as previously noted. This value depends on quality of the earth. system stability. 60 Hz. = ac resistivity of the earth return path in ohm-meters (the resistance between the faces of a one-meter cube of earth).762 2. or as taken from table. X'. for 100 miles of a line using In addition.3-11) to radius of 1 ft and Xd to represent inductive reactance in which Roo = ac resistance in ohms per phase per mile in the remaining space up to an adjacent conductor.000 Re Example: Consider the arrangement below in which conductor is ACSR 795 komi!. + = + + = + Wl'Slilli'itOIm'. r--15 0.1805 megohm dance of one mile of a 3-phase transmission line without miles divided by 100 or 0.4228 j 2. the is also affected by a mutual reactance term because of megohms of shunt capacitive reactance which determines nearby ground wires Or circuits.1370 ohms per milt at 75~C X.2858 j(2. To obtain the megohms of shunt capacitive reactance f = Frequency.2858 ~O X = 0. Drake. where f = frequency p. that is. It is customary in engineering work to express shunt capacitance in microfarads per mile and X'. The shunt capacitive reactance of a conductor system is in which p.000 5. " 1964.608angleSO. The zero-sequence impe the charging current wiD be the listed 0. ohms per mile From tables. 3~9 R~ = 0. at 15 ft is 0. are given by Eqs. = 0. The prime (') is affixed to the X' to prevent confusion with X-values that represent inductive reactance.3286 and at 30 ft is 004127 Substituting in Eq. Roo R. = resistivity (ohm-meter) * This is an average value which may be used in the absence of definite information.and X. corona. the listed megohm-miles value is to be divided by length of line in miles. and Xd are inductive reactances in ohms per mile components as follows: = + 3-17 . Zero-Sequence Resistance and Inductive Reactance Factors (R.4191 -.2Xd ) (Eq.2858. and X. Hz that controls charging current of a line longer than one mile.lil) Frequency tn 60 Hz Frequency (f) 60Hz Resistivity (Pe ) Ohm-meter ohms per conductor per mile All values 1 5 10 50 100' 500 1. 3-11 for im:pedance Zo Z.343 2.469 2. and transients set up by faulting or line switching. per mile 2. the R. but with ground return.67D.307 3.1370 0. the corre sponding reactance in megohm-miles.3566 3 ohms per mile in which Xd. regulation.3-12) 2"jC In which if C is in farads.5738 ohms!mile 2.760 60 60 f p.888 0. among them voltage distribution.399 ohm. 0737 Corporation.0506 0.1028 Substituting in the termS of Eq.1094 0.. the right-hand term represents X'd' the 0. that affects zero-sequence capacitive 0.0532 -0.0411 0.0588 0.1037 I 0.0913 + 0.0584 0.0429 0.0435 0.0326 -0.0229 0.0473 0.0889 0.1)461 ft.0574 0.0510 0.0594 0.0326 0. 0.0318 0. are listed in the tables of electrical properties of 0.0411 -0.0544 0.1087 X'.0350 0.0272 0.0515 0.0462 0.0711 tion Reference Book. 3·18 + = = 'n = . 0. Hz 0.0567 0.0563 0.0461 0.0614 -0.0120 -0.0501 0. 20 rt spacing.1071 X'.0085 0.0160 -0.0930 The left-hand term of the above two-term equation 0.0903 f = Frequency.0917 0. Capacitive reactance in megohm-miles per COn 0.1136 X'.0889 = 0.0241 0.0482 0.0874 Overall radius of conductor.0372 0. It 0. ft 0.0652 0. 0.0683 -loglO 0.0598 0. £t 0.0552 0.1149 (Eq.0540 0.0536.0417 0.0803 X'd = 0.0193 0.0591 0.0823 d : : : Separation in feet X'.0342 0.0943 represents X'" the capacitive reactance lor 1 ft spacing 0.dius of conductor 0.1129 sentedby 0.0291 0.0487 0.0218 0.0497 0.3-14) 0.0577 0.0441 0.0392 0.0152 0. = 0.0251 0.0046 0.0683 -10glO dab 0.0205 60 log".1123 reactance depends on distance above ground.1079 megohm-miles 0.0683 X 1.0913 0.0399 0.0206 0.0206 -0.0532 0.0300 0.0405 0.0978 These two values have been tabulated lor 60 Hz.0955 (to I-ft radius). 1964.0357 0.0601 0.1802 megohm-miles 0.1063 megohm·miles 0.06831 log lOd in which 0. Westinghouse Electric 0. 0.0385 0.0761 60 X.0604 0.3010 = 0.0523 0.0608 0.0024 0.0889 d" = Separation distance to return conductor.bare aluminum wire and cable TABLE 3-12 Separation Component (X'd I of Capacitive Reactance at 60 Hz III Megohm-Miles Per Conductor Separation of Conductors inches feet! 0 0 1 2 3 4 5 6 7 - 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 35 37 38 39 40 41 42 43 44 45 46 47 48 49 1 ! 2 3 4 5 6 7 9 8 = 11 10 -0.1055 0.0309 0.0457 0.1109 0.0999 conductors and those for X'd are in Table 3-12.0783 (1) From formula: for 60 Hz f rn I (Eq. Ra.0136 0.0365 0.3-13) 0. .0085 0.0423 0.0967 separation component.0617 0.0180 0.1102 Zero-Sequence Capacitive Reactance 0.0559 0.0054 -0.1019 6(} Hz.0166 0 0.0683 108" . = 0.0683 X 1..0282 0. It is repre 0.0737 -0.1116 An added term E'.0519 0. 60 1 0.0989 for X'.0103 0.0570 0.1009 Example: For 795 kcmil Drake. = 0.0446 0.0611 0.1046 X'.0334 0.0683 From: Electrical Transmission and Distribu 0. 3~ 13 0.0066 0.0581 i 0.0683 log" 20 = 0. 0.0452 0.0262 0.= 0.0548 0. = 0.3365 = 0.0841 ductor 0. both are in terms 01 megohm-miles.0478 0.0379 0. Those 0.0492 0.0026 0.0555 0.1155. 0.0120 0.0260 -0. 2h in which h is height of can 0.0858 0.0467 0.1142 t ductor above ground.0527 0. Basic to the calculation is the establishment of an ambi ent temperature level. When the tempera ture of the conductor rises to the point where heat output * Conductor ampacity has been reported extensively by Schurig and Frick. 3-19 . lisual practice is to assume an ambient temperature of 40'C for overhead conductors. Most aluminum transmission conductors are hard-drawn and operate over predetermined ranges of maximum sags and tensions. Hear Balance: Temperature rise in a conductor ciepends on the bal ance between heat input (FR loss plus heat received from sunsbine) and heat output (due to radiation from the COn ductor surface. and atmospheric pressure (altitude). =: 0.. The factors of importance that affect ampacity for a given temperature are wind velocity.. temperature risc.. Ampacity of Bare Conductors' The major considerations involving the current-carrying capacity (ampacity) of overhead transmission conductors are the effect of conductor heating by the current and the consequent reduction of tensile strength. The brief treatment herein is abstracted from many sources. of conductor surface W.. The effect of sunlight and altitude as well as of varia tions of emissivity constants are shown by small auxiliary curves of Fig. at sea level for 60°C rise above 40°C ambient. Convection Heat Loss (W. + X'd . amp The convection heat loss W" depends on wind velocity. and the amount of the latter depends on temperature of the outside air. its roughness. lower ambients will be found in some applications. and the temperature rise for a given operating temperature must be altered accordingly. Obviously the ampacity is related to temperature rise. (Eq. The usual maximum operating temperature for ten sioned bare conductors is 70° to 85'C. and a body that radiates all heat would have. Newly installed conduc tors mav have.) for 2 ft/sec wind.elI-blackened after year~ of servj~e.. = 0. 3-11 et seq). I. and of course the ambient temperature.)b may then be used in place of X'" and X'" in the corresponding equations for positive. The radiation heat loss W. and their results checked by test programs.2X'. i = Current for balanced condition (the (Eq. McAdams. This value (. Radiation loss. The various factors entering the heat balance equations have been summarized by one conductor engineering group into the following: 1. reactance components. the heat balance may be expressed as PRo. in.. Xd(W.engineering design The zero-sequence capacitive reactance of one 3-phase circuit without ground wires in terms of megohm-miles per conductor is X'o ~ X'. equals heat input the temperature remains steady. W. etc.)b and (X'. House and Tuttle and others.23. = R"rr = Total effective resistance per ft of conductor. except a prime is added to each X. Heating to relatively high temperatures for appreciable time periods anneals the metal. with 100'C and ovcr permiSSlble only in limited emergencies. principally the Alcoa Aluminum Overhead Conductor Engineering Data book: Section 6. 36 miles per hr) as well as for still but unconfined air (Figs. The emis sivity factor < for aluminum conductor surfaces depends on the degree of oxidation and discoloration of surface. which also show values based on a cross wind of 2 ft per sec (1. H. Thus (X'.90 after being ". "" 0. A value of . =0 (W. 3-15. atmospheric pressure (which affects ampacity at high altitudes).3-16a) I ampacity). W.. SO is ignored. and the tables and charts herein are on that basis. and the stranding. However. that expresses the ability of the conductor to radiate internal heat. is considered to depend on tempera ture rise and an emissivity constant . and transfer because of convection of air currents). thus reducing the yield strength and increasing elongation. 3-15) in which the terms have previously been defined. ohms. Neglecting sunshine heat input. Convection loss. watts/sq in.• ~--=-"'C":~ ~-~ .. A perfect non-radiative surface would have.) = ~-------------------R0ff in which d = Outside diameter of conductor..+W..or zero-sequence inductive reactance.5) is used for the tables and curves herein. including the resistance-equivalent of pertinent components of loss under a-c con ditions. as low as 0.. watts/sq in. and the current for such condition is the ampacity for that tempera ture under the stated conditions.) A" both terms in watts/linear ft.. (skin and proximity effects.5 provides a safety factor for the majority of ex posed conductors which have been installed for several years. The heat loss arising from metallic conduction to supports is negligible. of conductor surface A = Surface area of conductor per ft of length. conductor surface emiSSivity. (Eq.. and mav be 0.) which reduces to . .3-16) and in which W. sq in. Hence the ampacity of such conductors is generally stated to be the current which under the assumed conditions of operation will not produce sufficient heating to affect significantly the tensile properties of the conductor.. Capacitive Reactance of Bundlcd Conductors The shunt capacitive reactance of bundled conductors can be found from equations identical with those used in the numerical example relating to inductive reactance of bundled conductors (page 3-17). 5 (an average emissivity for weathered conductors) (Eq.) in the above equations. = 3.01 43.7 St. 8AI. 12AI. 12AI.600 134.73 d watts per ft of length for < 0. = 6.072 d· 75 6 t.994.000 176. lACS multiply by 0.7 St. at the lower ambient and the same temperature rise.200 BAI. the radiated heat loss is less.3-19) 3. Sun Heat Gain (W.3-17) W. diameter and over (Eq.7 St. Ampacity of 1350-HJ9AII-Aluminum ConduclOr and Standard-Strengtit ACSR Conductors Ampacity graphs for 1350 all-aluminum conductors. values for 600C rise are from Eqs. W. For 61.600 159.300 203. Small graphs of mUltiplying factors for sunlight.000 159. 13. 12AI. . 12AI. 3-17. + W. 12AI. 12AI. and 14 for still air and for 2fps wind at 4I)OC ambient for.5 emissivity. 12AI.5388 (1.50 and 62.7 St.7 St. 16AI-19 St.3-20) 4.6 in. = 22.800 211. Current in Amperes ! Code Name Size emil. Petrel Minorca Leghorn Guinea Dotterel Dorking Cochin Brahm.22 d V.7 St.) for 60 e C rise above 40°C ambient - W.800 110. lACS aluminum without sunlight effect.7 St. Stranding Grouse 80. 3-18) 2.800 190. a small change in ampacity for a given temperature rise may be obtained because the resistance of the conductor is less (because of its reduced temperature). no sun.7 St.7 St.3-21) 3·20 Temp Rise IDe 106 62 125 75 132 79 149 92 166 104 178 111 187 117 199 126 188 120 I Temp Rise Temp Rise 30e aoe 175 113 236 166 263 190 277 201 314 231 352 262 374 280 394 296 422 318 389 296 204 133 211 142 239 162 266 182 285 196 300 208 319 223 301 210 .7 St. Radiation Heat Loss (W.800 134. 3-15. 12AI.900 176. 0. 3-11. The W. If the ambient temperature is less than 40°C. and Standard-Strength ACSR are shown in Figs.300 211.000 80. = Wind Condition 2 ft per sec Still Air 2 It per sec Still Air 2 ft per sec Still Air 2 It per sec Still Air 2 ft per sec Still Air 2 ft per sec Still Air 2 It per sec Still Air 2 ft per sec Still Air 2 It per sec Still Air + W.1 St.bare aluminum wire and cable TABLE 3-13 Current Ratings for High-8trength ACSR with Single Layer of Aluminum Strands 40 C ambient € = 0. 12AI. and W.2". at sea level W. The slope of the lines from the 60 0C values is based on experimental data.0 d watts per ft of length for mid latitudes (Eq.•2) watts per ft of length for d up to 1.'·25 watts per ft of length in which 6 t.7 St.7 St.7 St.15 dO·' watts per ft of length for d 1. 12AI.)-to be subtracted from (W.1 St. 12AI.800 101.6 in. 16AI-19 St. 12AI. and -20..7 St. The net result is that the current for a given temperature is little changed over a considerable range of ambient temperature. 12. diameter (£q. is temperature rise above ambient (Eq.000 101. and emissivity corrections are shown in Fig..900 190. -18. However. altitude.) for still air.800 110. 12AI. Convection Heat Loss (W.200 203. =0. 12AI. (still) 0. By interpolating in Fig. The maximum assumed emissivity for a fully weathered con ductor in normal altitude is 0.23? Note: The multiplying factors of Fig. diam. E = 0.90 = 630 amp. wind of 2 ft per sec.5"70 lACS Examples of Ampacity Values Obtained from Figs. and the emissivity factor taken from the right-hand diagram with sun for. if the 1350 wires are 61.. it is noted that ~his intersects the 35"C line at 630 amp.83 X 0.83 (approx) for I. 3-150 as being 0. Cable size 795 kemil ACSR 26n stranding.23 is 0. the equavalent conductivity value is used. but inasmuch as the ampadty diagonals on Fig.165 in. It intersects the 35'C rise horizontal at 835 amp. the ampacity of any conductor of conductivity other than 62% lACS is found closely per the following example: Find ampacity in still air for 30'C rise of 394. lACS conductivity of the ACAR conductor.91. Hence. the ampacity at 52. diam.5 is the maximum assumed for weathering conditions at high altitudes (l0. this reduces to 1050 X 0. The Aluminum Associ ation pUblication.50.90.1 in.5) 161 = 58.5/62. for conditions stated in Example 1.5% lACS is 320 x (52.) cable of 6201-T81 of 52.0)i!. 3-13 and 3-14. Conductor Economics The high cost of energy and generation facilities has made it very important that power losses be evaluated when selecting the correct conductor size to be used in a given project. is (42 X 61. 3~ 13 are almost straight lines. thus. diam. the "7. for 42119 ACAR (1350 and 6201-T81) of 1. which is the am pacity for the stated conditions.000 ft with sun. lACS.000 ft). the unadjusted ampacity is 1050 amperes.83 X Q. of the order of 1% or 2% in this instance is: obtained. Ampacity of6201-T81 and ACAR Conductors Inasmuch as heat loss for a given temperature rise is proportional to conductor surface (or diameter) and heat input is proportional to FR. These strktly are applicable only for lOO~C operating: temperature.684 in. Q Emissivity Limitations for Figs. the same value as previously obtained. Construction and energy costs have increased dramatically during the past decade. and 60'C rise. 3·14 at intersection of 60"C rise and 785 amp. and fonowA ing down an imaginary diagonal that is parallel to an adjacent diagonal.2 + 19 X 52. 3-14 note the diagonal line that extends downward from the designated size. Entering Fig. 3-11 10 3-14 An emissivity of < = 0. The desired am pacity is 835 X 0. 3·15 are to be used. "The Evaluation of Losses in CondUC tors.!'X) = 785 amp...engineering design Ampacity of Single-Layer High-Strength ACSR Conductors Table 3-13 can be used for ampacity values for high strength ACSR in larger-than-A WG sizes for 10'. it is satisfactory to apply the muitipJying factors directly to the 35"'C rise ampadty of 835 amp. the ampacity of 62"70 lACS 1350 conductor of same diameter (if it could be ob tained) would be 320 amp. The following typical examples illustrate the use of the various graphs: I. or 294 amp. 3-21 . The altitude factor with sun is taken from the left-hand diagram of Fig.l in. 3-11 to 15 Incl.ese values on log-log paper simi lar to that used for Figs.' For ACAR which has wires of two conductivities. what is ampacity if altitude is 10. After applying the multiplying fac tors. and this trend seems likely to continue. 30'. and with emissivity factor reduced to 0. and the values obtained are conservative. 2.¢/Rde ratio caused by change of in~ ductance." provides details on how such an economic analysis couId be done. a slight increase of ampacity.5 % lACS cOn ductivity. = 0. Note: If the multiplying factors are applied to the 60 Rise ampacity. • The method described is based solely on comparative [2ft Joss. outside diameter.5 kemil (0. or 75°C operating temperature? At top of Graph Fig. approx. What is ampacity for 35°C rise. If correction is made for the slight change of Rt. Values for intermediate temperatures may be obtained by plotting tb.2"1. 3-11. For the cable of Example 1. 1. ..' " '" '" .. • ~ to SIZE AWG KCMIL STRANDING 60 " N "- "- "- " N M N 0N M ci ci 0 0 I N "- "- '" M "- "- . . ~ M M N c- "- '"'" 0 '"0 "- M M M M N N ".I" I T I I / I " rr I/V iY • - j I' 1 1 11 II II 'I r· w '":::> ."'" "-.O_N(") "- 0 '"'" 0 0 0 000 000 e N '" M 0 M '" N .'" ro '"ci N ~ M ~ N :0- '" ro DIAMeTER -INCHES 0 0 0 " '" '" . multiply values by 0. I 40 III V 50 I / l i l 'r II II 60 70 j . and for high a/tiludes. '"" .w g ..30 '" I I' I ::!i_ Ii jI 'I r : J '" I r' ' I I j l V /}w l 1/ / I I I fA fA f I I' I 1/ / I '1"~... No Sun~Sea Level...'"'" '"'" '""-'" o. Ambient Temperature 4(f'C Emissivity (t) 0... "-'" a>'"'" ro '" '" 0 0 0 '" 0 '" " '"<i -ON M M N 0 -. see Fig. '" '" '" ".. III II I I' 'I ' u .. Current-Temperature-Rise Graph for Ampacity £!fBareAluminum Cable Stranded 1350-H19 62% JACS Still Air. to 0 ::l Q. 0 <0 0 "- ~ ~.. 3-15.". .t~~tt~Ll~I1. ".5...2% JACS.w w .v I I¥ / V I( I I I ( j j j j II I 80 90 100 150 200 300 400 500 600 700 800900 1000 1500 2000 CURRENT 60 HZ AMPERES Fig.'"" N M N 0)00 Nf'.. « 20 I l: ~ 10 I 30 11I ..:t M '" NN""": V'lMO<"'-U1 o. .r~~. I / ..:!2 N "'''' II 3 c: 3 "'". For multiplying factors for various sun and emissivities... A / II I ((I T It ( i. ... Chart A.. "0 ~ 50 40 I I II I A ... 3·11...r'~..994. '" '" "' ":N M-o-<>-o-o -0 N ~ ...r~~~~~~~~ I I"I ..V}O"'f NM"..... For 61. '0(h 0- M N N M "'''' ~~ ro'" " "'''' '" '" '" N M .'I I I " '1'1 ' . For 61.. multiply values by 0.•!2• " · III Q y' w « ::.- N - N 50 . I r'I i'I'r ..f)'O>{') N "'1:N 0000 "<t " 0 '" '"0 "'''' 00 M If') 0 a 0 0 <f)I:"'1Q-t-..() " M N N"".SIZE AWG KCMIL . M-Q -0-0-0 .. 40 I " I"i ' l l ' fA "J I'j I ' I 'I I~ J . I I t111/ I' II "'I ' I' I I I n Il I) d ·r-I-- I .. I' II I~ t. . No Sun-Sea Leyel... I!. and for high altitudes.994..-. I ...5. c5 ~: " <Q ! " . AmMent Temperatu.> 100) I!... ..... I' I JJ I'I •' Jj r. 3-12.f) -NMM "'<. ro ''"" '"'". see Fig..... .. .. Por multiplying factors for various sun and emissivities.e 4(J'C Emissivity (E) 0... <i -i( <i M D- '" '" "- " "'"0 '"0 '"'"<> '" M N N V) 0 '" '" '" '<tMNN~ 0 _ 0-0 ........ '" 00 ~ 1"-. 0.. Chart B...t -- 00 00 N N M "- " 0 l. Yj II> I 70 eo 90 100 150 200 300 400 500 600 700 800 900 1000 CURRENT 60 HZ AMPERES 1500 2000 3000 Pig.. lli1 I'I ..2% lACS..... I YI " .201 ~ .. I'I' I I . 3-15.N M 0 '" . 0- N 0- "- 0 0- "M . Current-Temperature-Rise Graph for Ampacity of Bare Alumillum Cable Stranded 1350-H19 62% lACS Still Wind 2 fps....: 301 8 .r '" f u '"w ::...> • 15 1 V 10' 50 60 • I I III I • I I ( 1 j f' II ' ( i I' " j I } II I ' " I I' rI 1~ )' II l ' I }' J I I .. w ..." 0 0 0 N ro DIAMETER-INCHES ~ N N N M N 0 M 0 ..l(")O"<:t l.. . " STRANDING '" '" " N 0- M N 0 60 ~ M '" '" '" '" '" '"ro ...... .. '"'"<i '"'" ""'" '" '" '" '" '" ...r " L{' B 'I / I I' If'I If'I IJ II I I'I rI i . - .. ~ :.. '".jNNNN 1.. '" "'" '" '" '" ..... Ambient Temperature 41l'C Emissivity 0..1") (".I")1.1'1-0 '"vi '" .. It") . "'v to '" ....1") "- } A I{ .I")"<t"lt (">1000.. I fI jI . '" "- STRANDING '""''' '" .." '-"" """ . t-. I'. F T l i Lf f / V I{ or :it ::J ~201 ~ If . "'''' '" '"0 00 0 NN 0 60.. ... For 61...:. " " '"r-. . SIZE AWG KCMIL ".. . ...P jI 1 II r I nlA/1 711# /1/ I'o//ll .. ..1") " " 0-0 ..". ~("oj M a <> '<> ~ '"" JJ M M 1. M ) .... II ..o. . .r:~~~~~~~~~~~~~~~~~~~~::~~~~ 40 I iil 1500 Fig...0.... YIlT 'iy (J n ~I IIVIIIJI" 400 AMPERES 500 /11 J~ 1\ j0 ... • l / V'lOr'J ...... ". 101 nil N 30 40 I f i l lI H1 50 60 It 70 III II 60 90 100 II I I II Y' 1_.. 0.... " ... ./1 150 AfJ uri rIf AI...j iJ '~~T· V) "t""'<t -o'<)Nv)"'-. " '" II"') N N .. Current-Temperature-Rise Graph for Ampacity of Bare ASCR 62% lACS Still Air.. No Sun-Sea Level.. .. "'" "'" r-.0'0-0 "wt"'lf \01")1.. '" II 501 _N MOl .0-<> .. -0-0.... "'''' ~ 'Z 'Z M "" "" '"'" " ..1") M Q "'ItMNN - I '" 1. «'!~. M .. .. I I{ r j /£y .2% lACS. M N 0 I . ttl" 200 CURRENT 300 60~HZ I I AI I ( . ... multiply values by 0. 0 .. NMM'!If .. .' .j7r---lf~~-j~~~7r.. '" '" '" -" " '"-0 'to..'" '"'" .... .. .. and for high altitudes.994..-- ..01. see Fig... <t") 0 ()..... "-<>0 ....... 0'" 0 i ~ ~ ~ .. n 030'---~[..: . For multiplyingfaclOrs for various sun and emissivities........ ..(>.' c: 3 '" u 0:: Q <: Q. ""<t Q) (0 N 2 ......' If } .. II V I 1I 7 v I £ } L1I r I I Jnl £ IIJ Ti' I I ~ I 7' I r r I 'I I ~ I YJ r..." .: '-: ... Chart C. 0" '" DIAMETE R-INCHES .J! I II! 600 700 800 900 1000 Q ..... '-r-~-'-'- IIlll! II IV AI I ..."""" ..5.. 2000 rE) .-- 0.. M 1.'" "''''" ... .... . V) «')-0 " ("oj II I MOl .w • N . 3-13.. ()...... 00 In 1 " "- "- IHI M J ."<tO"'ltNO 0 .. . A '"0:: .-. "'I'..'" 0 MOl "" M N . ~..:"'" "'''' "''' 00 00 0" d dod ...-. 3-15........ } ..} £1 T "f i l lq T '"or II• £ • • iii" IV ~ I I.N to • .' <1> Q r UJ Cl or 3 :. 0 <i -0 -<> _ M""<t N -:0 "" :0:0 N c::.o.1 u '"ttl \)3olr--L w <:> ..I N N NN('H'fN \l")V)'<t'<t'lt'<t co 00 "!f- M to .w• VI Fig..-' ... Current-Temperature-Rise Graph for Ampacity of Bare ACSR 62% lACS Wind 2 fps.0.0"" " MM (). . see Fig.' :rm (Q i'" .-OO. For multiplying factors for various slIn and emissivities...l I 1/ I I I -f--It .'" w w '" ::> !.g=~!~ ...f~~~~ ..... -0 N N M ~.<s:O " STRANDING 1 00 DIAMETER-INCHES 0- 0 6 0 ~ 0 a N _ N _.. II 40 600 700 800 900 1000 1500 CURRENT 60 HZ AMPERES .. 0-- ~ 11")"0-0"" IJ")V') ""'MNN __ O 0 co -0 o-... Chart lJ. No Sun-Sea Level..z:::...5..l""'. -(O~:O <t " <s~..a~~ ~ ~ -('. 3-/5. '" '" "M lI"lMO>-r-. 3-14....994.....i20~--~ '" " w lIE w I 151---~11 lOL--.. .SI ZE AWG KCMIL "¢ "'It . -""" " " " " ~':....q 00 " ~ : 0 0 co co - 0 0 ....1")0("") .oll"l'Ov)v) 1. and for high altitudes.. multiply values by 0..r--..... V1 N ~ ""... ~ ~ :0 <r -() V) 0 0 M..g 0 0 M N ~ ~ 00 '!f"!f lI"l \11 . MM M lI') . Ambient Temperature 40'C Emissivity (Ei 0..""""-''"' "<t '¢ 00 S'2 V) ~ N so 4011-.....2% JACS. 2000 3000 " (Q ..-CO -o-oN<I"/"N N N ~H:~ ~ ~ ~~~C'>~ ~~g"~~~ ~ ~ 000 0000"'... For 61.. 90. "nth sun - - 0. 3-26 .0. Emissivity Effect c· Emi$$ivity Effec I no lun with Ivn --- 2.OS 1.95 SUfi i No Sun ~ 0.1. 1.65 ...85 .95 1.00 I ~II 1.10 1.90.!to I 0. sun.j.5 w IE c.EII1'nl".05 1.91 0. Eminivity Effe(:t b...85 ... .91 0. w i .80 .90 to 8 1.80..5 Sun S" 0. Fig. .95 .9 I " Z 0.90.50 II --- SuJ °S5 . fz t) - :> "z 8 O· Altitude Effect 10. 5 ~ No I 1..0 0.50.SO C-For stranded ACSR in still air.o '" t. U . 3-12.1 5 .5 b.5 O. :95 0. and altitude.85 ..50.5 b.10 II . - - ~ 1.90 .90 . \ .. Fig. . 5 \ .95 .75 ..i ty Efhtd no - 2.Emiuivity IHied ¢. I.23 B-For stranded 1350-wind 2 jps. r 50 I CURRENT A-For stranded 1350 in still air.85 ij to . 1...00 1. 0.85 . 3·15 (A.85 1.0 '" D ~t5 (123 0. ~ ~ 0. B. . 3-11 to 3-14 for 600C rise inclusive by the applicable foctor at bottom of diagram corresponding to the associated ampacity CUlVe. '" ..0 -- 0.23 I . 2. . No Sun .80... Altit'Ude fffec t 10.80.000 feet 0..90 1. ! - - 0. 5 - - o 1.. 1.bare aluminum wire and cable Chart B Chart A a.95 .0. 5 Q 8 No Son 1. Multiply the ampacity value obtained from Figs.0 :> 0.So. .23 -- 0.0.90 . 1\ . Fig.95 CURR£NT D-For stranded ACSR-wind 2 jps. . Q WI! aU t.90 Chart C . EmissivityEHect no sun - - SOO 0. i Alti'ude EH~ct 10000 feet 2.23 Sun\ CURRINT Q. C.91 I . . 5 - - - - - 2. '" 10.Altitude Effec1 .95 - Chart D - 2.10 1.91 I ~t 5 U :> 0...00 UO 1-20 .95 ...000 f~et $ ..9 ~ l.50. .15 .20 .5 "x aU t. Fig. sb .05 1.95 .00 I l.50.0.95 1.91 0. and D)-Multiplying factor for various conditions of emissivity (.75 . - - I $ . Emissivity Effe<f c.90. I . 3-11.23 0.23 0.95 ~ 10·23 - I .65 . 0.. u b..90 0. ! 2. Emi1-sivity Effect wah S\ln no $lIn - 0.50.000 feet . 3-13. 0..90 - 0..5 i. 3-14.85 . 1. .5 CURRENT 2)) . - \ II 91 with svn b. Q.0 . Fig. AAAC. which provide moderate protection against corrosion and abrasion but have no voltage rating. all~alumiw num condLlctors listed as with B. etc. Outside diameter reduced after stranding. Thus. Further information regarding weather-resistant coverings is in Chapters 7 and 8. NOle: The tlbove list comprises cond"Jctofs that ordinarily are installed in :. Expanded core designs for EHV generally use 1350 H19 strands for conductance along with steel rein forcement. Other designations associated with the con ductor such as AAC. many of the various conductors are identified not only by size and description. As a convenience. without covering or it'lSuJa tion. For information on their eventual applications reference should be made to the chapters in Section 3 on "Covered and Insulated Wire and Cable. C. from the strain bus at the generation plant substation through the transmission con ductors and overhead ground wires to the distribution sys tem and the neutrals for service drops. Some of the bare conductor data is also applicable to conductors that are covered with weather-resistant materials.are condition: that is. flexible concentric tubes or combinations of aluminum wires and fibrous ropes. A typical exam ple of an expanded-core cable is shown in Fig. ACAR. Homogeneous designs ofaluminum conductor consists of: AAC (see Aluminum Conductor): 1350-H19 (Standard Round of Compact Round) AACrrW (Shaped Wire): l380-H19 (Trapezoidal wire) AAAC (see Aluminum Alloy Conductor): 6201-T8l 2. fish. Tables 4-26 and 4-27 covering Aluminum Unilay 19 wire conductors and the 8000 series Aluminum Alloy conduc tors are included in this chapter in order to list the details of the various strandings for the bare condition. No tables of properties of EHV cables are included herein because each project requires special analysis. 3-6. The word may be that of a bird. and the 4·1 . as registered with The Alumi num Association. They arC summarized below to aid reference to the: various tables herein: 1. and D strandin!! ore usually covered or insulated when in use. though may be bare for short lengths in apparatus. ACSR. and design practice is not as yet standardized. Product Classification of Bare Aluminum Conductors ACSR/TW (Shaped Wire): 1350-H19 Trapezoidal wire ACAR (Aluminum Conductor Alloy Reinforced): 1350-H19 and Strands of 6201-T81 Aluminum-Clad Steel Wire and Strand 3. Composite designs of aluminum conductor consist of: ACSR (Aluminum Conductor Steel Reinforced): l350-H19 Aluminum strands with: Class A (Standard Weight) Coated Galvanized Steel Core (ACSR) ACSR (Compact Round): 1350-H19 Strand. M The alloy and conductor-type designations used for bare aluminum conductors are described in Chapter 3. Expansion is by open helices of aluminum wires." Product Identification For ease of reference. to which a suffix may be added to denote product variations.Section II Bare Aluminum Wire and Cable Chapter 4 Product Identification and Data This chapter supplements Chapter 3 with tables of mechanical and electrical properties of specified sizes of commercially available bare conductors. but also by an industry code word. terminal leads. etc. Serricc Application of Bare Conducrors The tvpicat electric power svstem has many applications for bare stranded conductors. tables also are included in this chapter thut list modificutions of (he hnsic bare conduetOfs which ordi narily are to be covered or inSUlated before use. flower. and SOme larger-than AWG all-aluminum conductois are now sized on the basis of 50. Suffix notations that designate other than what is implied in A (above): For 1350-aluminum and Temper (for physical properties.03 Electrical Conductors. data in this chapter are based on these specifications. such as 1350-H19 and 6201 T81. type ofconductor than ordinarily would be expected." Common practice in conductor designation utilizes as sumptions and abbreviations.0 kcmil copper.0 kcmil 1350-HI9 aluminum conductor has approxi mately the same dc resistance as 300. The trend in recent years. Pa. are available at moderate cost from ASTM. Thus. the T81 temper is assumed. Use of the code word system and possible variations is described in the Aluminum Association pUblication "Code Words for Aluminum Electrical Conductors. the core is assumed to have standard weight galvanized class A steel core and 1350-HI9 aluminum wires. For 1350 aluminum. 1350-H 16 and -H26 designate %-hard wire. A. and the 795. however. which includes all specifications pertaining to Metallic Electrical Conductors. Specification numbers and descriptions at time of this publication are shown in Table 4-1. B. 1350-H12 and -H22 designate \<i-hard wire. For ACSR. For ACSR GB designates Class B galvanized steel core wire. * Size Relationships The tables of properties of aluminum conductors herein show a larger number of sizes within a given range and 4·2 • 1916 Race Street.000 emil increments. Individual ASTM Specifications and a book.0 kcmil copper. Technical Data and Catalog In/ormalion The construction and properties of many kinds of bare aluminum conductors are covered by individual ASTM specifications and unless otherwise noted. the Hl9 temper is assumed. 1350-H14 and -H24 designate V. the odd-size 477. ASTM volume 02. The wide range of breaking strengths of a given size of ACSR because of variations of steel-to-aluminum ratios also adds to the conductors available for transmission line design. AW designates aiuminllm-clad steel core wire. Hence each is not exactly the equivalent of any other type of conductor as to conduc tance Or diameter.-hard wire. 19103 . see Table 1-1) 1350-0 designates fully annealed wire. GC designates Class C galvanized steel core wire.0 kcmil conductor corresponds to 500. some AAAC and ACAR conductors are sized for diameter equivalence with certain sizes of ACSR. For 6201 alloy. Philadelphia. This comes about because replacement ofone type ofconductor by another is facilitated if they have equal dc resistance. or if their outside diameters are equai. is toward reducing the number of generally available sizes that are based on equivalence with other conductors. have been explained in previous chapters. Similarly. "Camp" designates compact stranding. AZ designates aluminized steel core wire.bare aluminum wire and cable alloy temper designations. Physical and Mechanical Properties. Steel Reinforced. Physical and Electrical Properties ACSR Aluminum Conductors. and D Strandings. Mechanical. Steel Reinforced. Physical. Sized to Have Diameters Equal to Standard ACSR. C. Physical and Electrical Properties AAC. Physical and Electrical Properties ACSR Compact Round Conductors. Aluminum-Clad Steel Reinforced. Physical and Mechanical Properties of Galvanized A. and Electrical Properties. Physical and Electrical Properties AAAC AU-. Electrical Properties ACSRfTW Shaped Wire Compact Conductors. Physical Properties ACSRfTW Shaped Wire Compact Conductors. Physical and Electrical Properties for Even kcmil Sizes AAC All-Aluminum 1350 of Various Hardnesses in Class B.'\luminum Alloy Conductors 6201-T81 to ACSR Diameters.TW Shaped Wire Compact Conductors in Fixed Diameter Increments.product identification and dolo LIST OF TABLES IN CHAPTER 4 4. Electrical Properties ACSRJAW Aluminum Conductors. Sized to Standard ACSR Areas. Physical and Electrical Properties AWAC Aluminum Conductors with Aluminum Clad Steel Wires as Reinforcement. Physical and Electrical Properties AAAC AU-Aluminum Alloy Conductors 8XXX Series. Electrical Properties ACAR Aluminum Conductor Alloy Reinforced. 1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 4-11 4-12 4-13 4-14 4-15 4-16 4-17 4-18 4-19 4-20 4-21 4-22 4-23 4-24 4-25 4-26 4-27 Titles and Numbers of ASTM Specifications for Bare Aluminum Conductors Conductor Metals. Sized to Standard ACSR Areas. Steel Reinforced. Physical and Mechanical Properties AAC All-Aluminum 1350-HI9 Compact Round Conductors. Physical and Electrical Properties AAClTW Shaped Wire Compact Conductors. Steel Reinforced. Physical and Electrical Properties AAC All-Aluminum 1350 Combination Unilay 19 Wire Stranded Conductors. Physical and Electrical Constants Aluminum Wire Data. AAC All-Aluminum 1350-H19 Stranded Conductors. Sized to Have Diameters Equal to Standard ACSR. Physical and Electrical Properties ACSRlTW Shaped Wire Compact Conductors. Electrical Properties ACSR Conductors Multi-Layer sizes. Physical Properties ACSRfIW Shaped Wire Compact Conductors. Tensile Strength and Elongation Solid Round 1350 Aluminum Wires. and C and Aluminized (AZ) Core Sizes ACSR Conductors Single-Layer sizes. Physical and Electrical Properties AAAC All-Aluminum Alloy Conductors 6201-T81 for Even AWG and kcmil Sizes. Steel Reinforced. Physical and Electrical Properties 4·3 . Physical and Electrical Properties AW Aluminum-Clad Wire and Strand. B. AAC Electrical Properties of Conductors listed in Table 4-5 AAC All-Aluminum 1350-H19 Stranded Conductors. Areas Equal to Standard AAC Sizes. Steel Reinforced Aluminum 1350 Round Wire. Steel Reinforced (ACSRIAZ) Aluminum-Alloy 5OOS-HI9 Wire for Electrical Purposes Concentric-Lay-Stranded Aluminum-Alloy 5OO5-H19 Conductors Aluminum-Alloy 6201-T81 Wire for Electrical Purposes Concentric-Lay-Stranded Aluminum-Alloy 6201-TSI Conductors Compact Round Concentric-Lay-Stranded 1350 Aluminum Conductors Compact Round Concentric-Lay-Stranded Aluminum Conductors. Aluminum Clad Steel-Reinforced. Aluminum Alloy Reinforced (ACAR and 1350/6201) Concentric-Lay-Stranded Aluminum Conductors. Concentric-Lay-Stranded (AAC) Concentric-Lay-Stranded Aluminum Conductors. Coated. B 230 B 231 B 232 B 258 B 341 B 3% B 397 B 398 B 399 B 400 B 401 B 415 B 416 B 498 B 500 B 502 B 524 B 549 B 606 B 609 B 682 B 701 B 711 B 778 B 779 B 786 B 800 B 801 4-4 Aluminum 1350-H19 Wire for Electrical Purposes Aluminum 1350 Conductors. Steel-Reinforced (ACSR) Standard Nominal Diameters and Cross-sectional Areas of Solid Round Wires Aluminum-Coated (Aluminized) Steel Core Wire for Aluminum Conductors. Zinc-Coated (Galvanized). Steel-Reinforced (ACSR) Aluminum-Clad Steel Core Wire for Aluminum Conductors. (ACSRlAW) High-Strength Zinc-Coated (Galvanized) Steel Core Wire for Aluminum and Aluminum-Alloy Conductors. Steel Reinforced (AACSR) (6201) Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors (AAClTW) Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors. Steel Reinforced (ACSRlSD) Concentric-Lay-Stranded Aluminum-Alloy Conductors.bare aluminum wire and cable TABLE 4-1 ASTM Standard Specifications for Bare Aluminum Conductors Standard No. Steel Reinforced (ACSRlCOMP) Hard-Drawn Aluminum-Clad Steel Wire Concentric-Lay-Stranded Aluminum-Clad Steel Conductors Zinc-Coated (Galvanized) Steel Core Wire for Aluminum Conductors. Steel Reinforced (ACSRITW) 19 Wire Combination Unilay-Stranded Aluminum 1350 Conductors 8XXX Series Aluminum Alloy Wire for Electrical Purposes Aluminum Alloy 8XXX Concentric-Lay-Stranded Conductors for Subsequent Covering or Insulation . Annealed and Intermediate Tempers for Electrical Purposes Standard Metric Sizes of Electrical Conductors Concentric-Lay-Stranded Self-Damping Aluminum Conductors. Aluminum-Clad Steel-Reinforced Concentric-Lay-Stranded Aluminum Conductors. Steel Reinforced (ACSR) Stranded Steel Core for Aluminum Conductor. 0975 2. coefficient of resistance per degree C at 2O"C 25% Aiuminum-Ciad SteeIAW" HD Copper Galvanized Steel 52.0000128 0.64 51.000.000.000.000 10.281 6.002 19.2381 Coefficient of Linear Expansion per degree F 0. u"'For the purpose of calculating weights.000 17. "'Note: Aluminumwclad steel wire is being produced typically in a grade with the concentric aluminum covering comprising 25% of the sectional area of the wire and a guaranteed minimum thickness of 10% of the wire radius.321 7.946 Temp. cross~ 4-5 .0000128 0.785 129.0036 Density at 2(rC'" Grams per cubic centimeter Lb.0 20.0 Max. Solid Wire Approximate.098 2.00290 0.690 0. average conductivity.0000064 0.0000072 Modulus of Elasticity.000 23.78 0.00404 0.2 61.0000094 0. percent lACS at 2O"C 61.3 17.705 0.00347 0.097 8.product identification and data TABLE 4-2 Conductor Metals· Physical and Electrical Constants I 1350-H19 Aluminum 8000-H12 -H22 Aluminum 6201-T81 Alumimum Min.000 I i "Drawn or finished wire.0000128 0.89 0. average resistance at 2O"C Ohm-cmil/It 16.000 29. per sq.59 0.00403 0.755 10.000.00378 0.500. per cubiC inch 2. 10.01 0. in.710 0.000 10.000.5 96. Lb.16 8. ---- Elongation in 1()" for IndlY.0 48.0 3.0800 to 0. 4_6~'0~_Li 48.3_'0_ _ .1401 24.1400 to 0.0 46.0501 29.5 1.0 1.0 0.5 48.0601 28.5 1.2 0.0 2.5 1.1878 to 0.0612 0.0105 25.0 44.2100 to 0.1327 to 0. _ _ L-_ _ m I .5 0.1800 to 0.0 46.. Tests-Min.0 44.0 ~.0 3.0 23.2101 23.7 48.5 2..0 26..0 to 0.1328 0.9 46.~ 0.Q700 4·6 --.1501 24.7 0.0 44.0 25.1400 to 0.5 1. % Individual Test I 46.0 46.2600 to 0.5 48.0 ::: .1100 to 0.0600 to 0.0 24.0 0.1201 25.0 0.0 3.-_ _ 23_..1500 to 0.0500 to 0.0700 to 0.1801 Tensile Strength ksi Average for Lot .5 23.0 3.1001 26.0 0.0701 28.0901 27.0 3.1101 25.bare aluminum wire and coble TABLE 4-3 Aluminum Wire Data Tensile Strength and Elongation (ASTM Specifications) 1350-H19 Aluminum (8230) 6201-TBl (8398) I---------~~-----_+-~--------__r- Tensile Strength ksi Wire Diameter (Inches) Average for Lot Individual Test Elongation in 10" for Indiv.1 000 to 0.1801 24.5 22.8 46.0_ .0 46.0 3.0 23. % 0.0 46.0 0.0 44.5 1.L-I_ _ _ _ _ _.4 48.5 1.0 0.5 23.0 3.0 0.0 3.0 46.0 23.1200 to 0. Test&-Min.0 0.0 3..1201 0. 00046 0.620 41.1819 0.43 38.04 9.0159 640 511 404 320 253 0.780 2.06 9.9 76.8 350.4 I .05 48.00082 0.0 220.8 820. 0.0508 17 : 0.00073 0.000017 0.000 It at 2O"C Ib i Ohms 194.704 3.11 15. 141.51 I I I ! I 886.942 110.00 114. 4.0 781.89 25.95 61.7 0.000100 0. Breaklng strength value of 1350~H19 are based on minimum average tensile strength of ASTM B 230.20 12.20 15.0253 0.01635 0.600 I 0.230 0.6 557.0285 21 23 per Weight Per Mile 1.00417 0.2 122.1443 0.389 4.78 40.2893 .0907 0.00147 0.52 34.1662 167. Nominal Breaking Strength Ib Threequarter Full Hard Hard 1350-H16 1350-H19 I 1350-H26 3822 2825 2241 3031 1777 2404 1409 1907 1117 1512 1225 971.370 1. 2.9 309.1045 105.348 1. Three~Quarter (3J4) and half hard wife shaJl not break at a value less than shown above.15 19.0808 0.233 443.0201 I 0.01028 0.686 2.125 1.0142 0.06573 66.26 21.01297 0.000503 0.0641 0.186 87.817 5.07 48. Weights.5333 0.00058 0.3 786.050 1.29 4.000 psi for half hard.15 0.8 0.0359 20 I 0.110 3.6 0.409 I ! 4.77 3.589 0.00513 0.3 353.0149 2493 1977 . 20.00323 0.144 2.76 17.00590 0.755 3.31 20. 0.7 0.00185 0.45 24.0691 0.090 10.0226 0.08291 83.2 0.295 ! 279.00065 0.04133 0.1144 0.4 278.00128 0.965 0.620 1.820 16.45 0.380 8.000638 0.00 2.5 174.00041 0.91 43.545 6.3648 0.495 55.00407 0. 0.38 2.78 27.740 33.090 26.00468 0.16 15.000804 0.100 ' 0.551 6. and Nominal Breaking Strength Area 1350 Aluminum Wire dc Resist- : I ance Wire Size AWG 0000 000 00 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Wire Diam eter Inches 0.360 52.875 1.7 389.0179 0.Q105 0.00744 0.9 0.000125 128 I 0.015 4.7 400.00092 7.3249 0.890 1. These strengths are based on minimum of 17.118 700.6 154. 0.02061 : 1.57 6.96 3.85 8.37 21.00234 0.1620 22 24 25 26 27 28 29 Circular Square Mils Inches 211.419 6.748 139.0 702. Electncal resistance is baS<ld on the electrical conductivity of 61.00165 0.372 221.020 812 0.180 4.00262 0.00331 0.284 3.97 74.00104 0.2294 0.product identification and data TABLE 4-4 Solid Round 1350 Aluminum Wires Sizes.19 54.297 5.38 0.1 212.00052 2.95 12.837 8.00208 0.530 5.51 27.000158 159 0.1318 133.03 I 1.196 0.290 1.00 91.600 0.4228 ! 154. 0.45 38.00526 0. Published values above take into account nominal wire area.00294 ! 24.0320 0.5 0.96 3.0126 0.240 .556 7.21 69.17 13.5 97.690 .2 262.3 441.03 7.15 19.4 0.40 30.7 ! .7 324.7 494.2043 0.12 2.0118 1568 1244 0.67 i I 43.260 2.57 0.580 0.02599 0.00371 0.4096 0.00663 0.8 87. Data shown are subject to normal manufacturing tolerances.78 3.09 69.42 1.00939 986.57 10.00648 61.0 174.700 : I i ! ! : OneGeometric half Mean Hard Radius 1350-H14 GMR 135O-H24 It 0.700 2.0453 0.383 2.0113 I 202 0.1285 I 0.146 553.000199 0.500 0.2576 0.67 10.8476 77.1019 0.3 194.05212 0.0 491.00101 0.0403 18 19 .470 175.6 109.2 245.60 1.000401 0.000252 0.0720 0.00116 0.00256 0. 3.29 31.03278 0.8 138.800 .01 4.00836 0.4600 0.3 96. de Resistance.2 0.876 13.617 10.44 34.00037 I 1.0133 0.93 6.26 58.41 30.2% lACS.8 623.70 17.000 psi for 3/4 hard and 15.00161 0.00203 6.510 13.00131 0.0571 0.15 12. 4·7 .6723 122.00816 0. 640 98.1198 0.5 Narcissus Columbine Carnation Gladiolus Coreopsis 1.590.3 745.000 .113. unless otherwise specified.AA A.172 1.078 1.3122 0.350 1. : : 0.1444 0.8741 0.AA A.1251 0.792 0. Class A stranding is usually specified for conductors to be covered with weatheNesistant (weatherproof) materials and used for bare conductors where greater flexibility is required than afforded by Class AA The direction of lay of the outside layer of wires with Class AA and Class A will be right~hand.0 1.724 0.033.858 0.0 I 556.0328 0.077 1.4 521.1226 0.1574 0.5 874.8117 0. 0.8117 0.970 6.600 27.6 894.5 954.1489 0.6244 0.510. .975 0.510 3. in.0772 0. • Code Word Peachbell Rose Iris .AA A.464 0.bare aluminum wire and coble TABLE 4-5 All-Aluminum Concentric-Lay Class AA and A Stranded Bare Conductors Area.184 0.3 820.131.830 4.1466 ! 0.0974 0.5 372.192.414 0.830 250.0 671.AA A.AA AA A i I I I ! . : 0.7493 745.5 1.300 25.0 874.5620 521. 4-8 .1 315.0 715.1672 0.AA AA 1/0 210 3/0 4/0 Dahlia Mistletoe Orchid Violet Nasturtium Crocus MagnOlia I Total Size i Stranding AWG or kcmil : Class ! i .300 1. AA A AA A AA A AA A A.216 1.0612 0.8 4.AA A.1083 0.AA A.4 969.8 966.5 1.7493 0. 2.300 15.990 2.1318 0.1391 0.3 596.1606 I : 61 37 61 61 61 0.1711 0.1351 I 0.AA A. Weight.3744 0.6868 0. Square in.918 0.5 477.040 3.900 17.026 1.AA A.5 Arbutus lilac 795.8 157.1548 0.000 23.0 Anemone .170 1.3744 19 37 37 37 61 ! 0.4371 0.062 1.9366 0.1952 0.1331 0.2 78.974 0.9 446.866 0..110 8.8 336.2 1044 1117 16.1093 0. Data shown are subject to normal manufacturing tolerances. ! I ! 24.0 1.1228 0.593 0.940 11.186 1.1398 1.1142 0.6244 0.1302 0.OS57 0.232 0.379 1.272.AA AA Wire ! Number : Diameter of Wires .300 8.100 13.258 61 61 61 61 61 0.454 ! .700 18.124 1.7 820.249 ! I ! .4 250.800 13.1311 0.0521 0.800 16.400 894. Goldenrod Bluebell Larkspur Marigold Hawthorn 954.~-- 1.2095 19 19 19 19 37 0.0 795.5 1.150 7.124 0.5 556.4 397.0 671.0829 0. and Strength of AWG and kcmil Sizes Physical Properties 1350-H19 ASTM B 231 Bold face code words indicate sizes most otten used. Class AA stranding is usually specified for bare conductors used on overhead lines.2 198.1379 0. Pansy 6 4 2 1 Poppy Aster Phlox Oxlip Daisy 266.000 15.1615 1.1045 0.5 715.400 12. : .300 19.S 39.0 1.9990 1.AA ! ! A.033.100 1192 1266 1342 1417 1489 22.1 62.292 0.586 0.0 A A A.328 0.900 14.2095 0.4995 0.1584 0.1532 0.417 1.5 636.1185 0.5 7 7 7 7 7 7 7 7 7 37 61 37 61 37 I I ! Weight per 1000 It Ib Conductor I Area Diameter : in. A A A.8 Laurel Tulip Canna Cosmos Syringa 266.9 124.02OS 0.6666 0.028 1.4 Rated Strength Ib ! 583 881 1.AA AA A AA A A.1447 0.666 0.690 ! ! 9.4371 0.368 0.400 24.522 0.1662 0.126 1.AA A.5 1.795 0.750 9.1135 : 0.2 1.0 1.700 21.8 446.1739 0.2844 0.0 477.5620 0.1538 0.340 1.0 1.351. 0431 0.216 0.946 ohm-cmilfft at 20"C for 1350 aluminum nominal area of conductor with standard stranding increments ASTM 6231.235 0.153 0.528 0.402 1.114 0.169 0.518 0.453 1.00700 .0254 0.06375 .421 0.177 0.419 0. 0.385 0.0935 0.398 0.0377 0.415 0.414 0. 0.169 0.674 1.384 1.142 0.0743 0.8 336.5 1113.235 0. using 0.0456 0.132 0.1043 0.0 954.158 0.216 0.102 0.119 0.120 0.350 0.556 0.2.0893 0.532 0. 1. 0. 0.541 1.09560 I 0.106 0.0921 0.278 0.158 0.0896 0.469 0.197 0.0 1351.103 0.124 0.149 0.3421 0.0935 0.101 0.5 1033.197 • 0.5 477.0362 0.0832 1.0896 0.0695 .428 0.334 0.202 0.0668 0.0331 0.145 0. 0.130 0.0841 0.0968 . i Megohm-Miles X'• 0.0187 0.Ohmsl Mile i MUe Peachbell Rose Iris Pansy 3.5441 .145 0.104 0.0881 0.131 0.332 0.109 0.305 0.0906 ! i .0819 .08823 • 0.551 ! GMR 3.438 0.0 1033.0908 0.130 0.389 0.110 0.0360 ! Inductive Capacitive Ohms/Mile X.0989 0.0968 0.504 0.5 836.0312 0.378 0.232 .0817 0.0731 0.1914 i 0.00883 0.114 0.374 1.384 .1435 0.00555 . 2.665 0.4 397.0988 0.489 0.446 i ! 0.5 874. 0.0111 0.420 0.202 0.224 I i 75'C SO'C Ohmsl Ohmsl Mile Mile ! I i 0. Altemating current (ae) resistance is based on de resistance corrected for temperature.120 0.0847 0.5 1590.138 0.0 1192.282 0.258 0.0275 0.1275 0.0839 0.06748 0.546 0. 0.0418 0.0 fI . Phase-to-Neutra! 60 Hz Reactance at One fI Spacing Resistance ae-60hz de 2O'C 25'C Size Code Word i AWG or kcmil Ohmsl .381 0.101 0.0 874.101 I 0.0155 .6856 . i i i i 0.5 556.0228 .403 0.682 0.700 0.0 1510.00991 4.0328 0.131 0.1276 0.0.235 0.145 0.0270 0.0933 0.630 0.0210 • 0.419 0.2294 0.4311 i 0.5 1272.133 0.06736 I I 0.1043 0.Q7655 0. 3--11 and 3~12.0294 0.0950 0.0911 0.0347 0.117 0.0920 0.550 0.0140 0.403 0.0 795.0391 0.2711 .09563 i 0120 0.0 556.8646 1°.131 0.0125 0.07721 0.0374 0.102 0. 0.1147 0.120 0.970 0. see Ftg.0875 0.8 268.5 715.111 0.1148 0.120 0.0885 0.602 0. 0.350 I 0. 0.188 1.120 0.680 1.00404 as temperature coefficjent of resistMty per degrees C" at 20~ and for skin effect 3.110 0.00039 0.0314 0.0795 0. I 0. 0. 4-9 .375 0.0872 0.1641 0.109 0.0856 0.0756 0.101 .0720 0.436 0.372 0.07175 0.769 0.0344 0.0634 .1915 795.399 0.3418 I 0.5 I 3.574 0.838 0.0 477.0177 I 0.08197 0.057 0.0444 0. 0.186 0.5 954.110 0.903 2.08826 .408 0.611 0.0951 0.255 2.0933 ! 0.127 0.0865 0.186 0. Direct current (de) resistance is based on 16. 0.448 0.product identification and data TABLE 4-6 All-Aluminum Concentric-Lay Class AA and A Stranded Bare Conductors Electrical Properties of Sizes Listed in Table 4-5 135()'H19 ASTM B 231 Bold face code words indicate sizes most often used.481 2.110 0.483 0.441 0.0778 0.459 0.0663 0.0468 I i I I 0. For ampacity ratings of bare conductors.1641 i 0.0 715.393 0.111 0.5 1431.409 0.142 0.484 ! 0.091 Poppy Aster Phlox Oxlip Daisy Laurel Tulip Canna Cosmos Syringa Dahlia Mistletoe Orchid Violet Nasturtium Arbutus Lilac Anemone Crocus Magnolia Goldenrod Bluebell Larkspur Marigold Hawthorn 6 4 2 1 i I i I ! I ! I i I Narcissus Columbine Carnation Gladiolus Coreopsis I i 110 210 3/0 410 266.0405 0.0250 i 0.0951 0. 127 0.- ----- ---- Sneezewort Valerian Peony Daffodil 250 250 300 350 AA A A A 7 19 19 19 0.997 0.998 0. Class AA slranding is usually specified for bare condUctors used on overhead lines. AltemaUng current (sc) resistance is basad on dc resistance corrected for tempefature. .249 0. (weatherproof) materials and for bare conductors where greater flexibility is required than using 0.0256 0.116 0.823 1._.320 r' .1560 0.A Shunt Inductive Capacitive Ohms per Megohm Mile X.0308 0. Mile Mile Mile Ib Sq.5498 0.750 2.0683 0.200 17. 1---. 'j-' A AA A - .1964 0.114 0.332 0.0954 0.5 468.3040 0.1305 0.432 0.0352 0.1357 0.f .00404 as temperature coeffiCient of resistivity per degrees C" al 20"C and for afforded by Class AA. Bold face code words indicate sizes most otten used.0913 2 0.0418 0.760 9.111 0.3534 0.0916 0. r' . For ampacity ratings of bare conductors.206 0.373 0373 0. Data shOwn are subject to normal manufacturing tolerances. In.476 0.172 0.108 0. r-' ..1424 0.998 1---.0 937. 0.1539 0.3650 0._. A stranding is usually speCified tor conductors to be covered with weather-resistant 4..1890 0.4712 421.152 61 91 91 127 0.0368 0. 0.8 468.1014 0.0446 0..964 0.0901 - 0..311 ----- AA A AA.126 0.111 0..443 0.1217 0..0977 0.5890 0.3 936.'" ~".0198 0..3651 0.0319 0..0526 0.1964 '0.1537 1.0321 0. Direct current (de) resislance is based on 16.770 0.445 0.0285 0.157 0.158 ----- 0.188 0..0445 0.0737 0.126 0..0634 0.106 .002 2..2509 GOldentuft Zinnia HyaCinth Meadowsweet 450 500 500 600 AA 19 19 37 37 0.447 0.8 15. .100 0. r' .410 0.3 562.629 0.480 6.342 0.400 15..660 5.0521 4 0..- Bluebonnet 3.148 0.7 655.574 0.0349 0.0818 0..0 7.5890 655.700 00417 00406 0.225 0.116 0.963 0. --.418 0.0943 0. Class the conductor with standard stranding increments ASTM B 231. .0525 0.2749 234.139 0. I I Phase-to-Neutral 60 Hz Reactance atOne Foot Spacing Resistance 80-60 Hz Weight .'--- 0.267 0.209 0.520 4.0798 0..188 0.0.2028 0. 3.890 8...1660 2.1375 0.- 127 1.350 ----- 844..891 0.0567 0.0954 0.1304 0.0265 ----- ~ut.0214 _ 0..161 0. de Total Wire Conductor per Rated Ohmsp 75 er 1 °C Size Stranding Number Diameter Diameter Area 1000 ft Strength Mile Ohms/Ohmsl Ohms! GMR kcmll Class of Wires in.- r TABLE 4-7 "'•" All-Aluminum Concentric-Lay Class AA and A Bare Stranded Conductors 1350-H19 ASTM B 231 Physical and Electrical Properties of Even kcmi! Sizes C) -.0715 0.466 0.121E 0.1827 0.3791.091~ 6 ----- 1641 1873 2365 2640 29.1215 0. r' .094 1. .401 0..3 281.1273 0.372 0.225 0..500 A .- 37 61 37 61 0.0917 0..206 0. Ib 20°C ft I 25"C 15O'C 1 Code Word Q § - ..1071 0..045E 6 0.1622 0.1694 0.000 Cowslip lupine Trillium AA A AA A AA A A A f--.700 Verbena Flag Petunia Cattail 700 700 750 750 AA 37 61 37 61 0.0512 0. ..1257 0..151 1..188 0. Miles X'.500 0. 0.229 0.000 1.. ~.2 703.106 0.0307 2 0.114 0..0490 0..1147 0.0963 0.700 1-- 0.400 0..811 0..630 1.151 0.. 1.900 13.700 34.100 13.749 3345 58.7854 0.~5. .374 1..1109 0.0609 0..110 10..0260 0.2 12.0585 0.0181 0.1162 0.0765 0.946 ohm-cmilJft at 20~ for nominal area of 2..161 0.105 0.036e 9 0.493 0.300 2.5498 0.0964 0.567 0.0944 0.0 644.1522 0.3927 0.0371 0.1826 0.0901 0.0479 0.679 0.813 0. 3-11 and 3-12.0310 0._.000 Jessamine 1.366 0.3927 0. The direction of lay of the outside layer of wires with Class AA and skin effect 5.451 0.407 0.421 0..9 4.500 12.0646 0.0588 0.151 0..447 0. see Figs.. 'S.102 0..487 0.7069 0.ln.500 3.4 327.1280 1.1014 0.422 0.. i'il Q a.127 0.390 0.105 0.04021 0..0697 .092 1.344 ~ 1.2356 0.7096 0.900 50. 8 If .4 234.8 703.106 0.525 .294 0.410 0.139 0.101 0.t~ .0243 0.357 0. Cockscomb Snapdragon Hawkweed Camellia 900 900 1..1644 0.570 1. . Class A will be right-hand unless otherwise specified.000 2.7854 .900 17.200 41.135 0.1482 0.0392 0.323 0.1657 0.:..0171 0. 681 0.2 157.682 6760 6920 6970 4260 4200 4160 3/0 4/0 4/0 300 I i ! (See foonotes at end of table.9 1650 1620 1600 1460 1430 1410 1840 1800 1780 157.471 0.0206 4 4 4 0.4 281.) C D I I I 1.1319 0.235 0.1055 37xO.0424 0.4 i I i ! I 2/0 2/0 210 0.9 (Continued) 4-11 .6 24.296 0.630 0.2354 0.0206 0.681 0.1662 B C D 19><0.0591 37xO.1 39.9 98. I 3210 3180 3140 3600 3580 I I i 3760 3710 3670 ! ! I i 62.1661 0.631 0. B C D I Rated Strength Ib CondUelor Dia.0828 0.0658 0. of Wires.235 B C D 7xO.4 78.0534 61xO.529 0.0640 91xO.470 0.184 0.420 2670 2760 2350 310 310 0.528 0.2745 0.0522 1 1 1 0.9 327.0757 91xO.186 0.297 B C 19><0.374 0.0973 61xO.1 39.1045 0.2 157.4 2160 2190 1870 1310 1280 1270 1160 1130 1120 98.232 0.0524 0.0822 61xO.1661 0.0207 0. Stranding Conductor Size Number and Dis. 3~11 and 3-12.000 It Ib I I .420 0.292 0.4 281.576 4910 5030 5070 3040 3000 2970 2680 2650 2620 300 B C D 37xO.2 62.472 3310 3410 3430 2080 2040 2010 410 0. and D Stranded Bare Conductors Physical Properfies-ASTM B 231 1350-H19 (Hard Drawn). as the slight difference caused by stranding variation is not significant in usual engineering calculations. AWG or Square Inches kcmil 6 6 6 0.2747 B 37xO.0328 0.0837 37xO.0900 61xO.0620 0.631 5890 5930 6080 3640 300 0.0701 91x0.8 234.0522 0.3 234.0940 37xO.0658 110 0.576 0.332 0.0658 0.0372 37xO.0521 0.0416 0.1964 0.0745 37xO.6 24.575 0.4 327.419 0.2355 350 350 350 0.0829 1/0 liG I Class I I I ! 0.6 I 681 783 746 535 519 508 472 458 446 39.1962 B C D 37xO. 13SD-H14 8.0974 19><0. 13S0-H16 & -H26 (3/4 Hard).0772 19xO.0664 37xO. For ampaclty ratings of bare conductors.2751 0.0600 61xO.0328 2 2 2 I 0. C. interpolate from Figs.0612 19><0.2354 0.9 98..0756 61xO.0370 0.3 234.0328 0.1045 B C D 19xO.0828 0.2 124.374 D I B C D I Weigh! per in. ac resistance and reaciance may be taken as the values for Class A conductors of equivalent size.333 19xO.0336 0.8 124.1982 0.2 198.0574 0.4 198.530 4020 4230 4340 2630 2570 2540 2320 2270 2240 250 250 250 0.1316 0.1315 B C D 19xO.2 62.1 1350 1405 1188 851 824 807 751 727 713 1740 1500 1480 1040 1020 1000 918 898 886 78.4 78.0476 61xO.8 124.333 0.0589 0.6 327.1046 0.3 ! 281.373 0. in.0469 37xO. -H24 (112 Hard) Direct current (de) resistance is the same as given in Tables 4-6 and 4~7 for corresponding sizes.4 198. 7xO.0673 61xO.186 B C 7xO.0467 0.0524 0.product identification and data TABLE 4-8 All-Aluminum Concentric-Lay Class B.0266 D -" I 1350-H26 135D-H16 1350-H19 135O-H24 1350-H14 ! 563 480 468 336 326 318 297 287 280 24. 6288 0.8 655.0810 91xO.0938 127xO.1215 91xO.7061 0.0703 0.ll09 91xO.032 14400 15100 15700 9610 9510 9510 8480 8390 8390 750.930 0.7 61xO.0 844.0768 0.3924 C 550 550 550 0.152 1.0 562.7 750.0950 91xO.3535 0.095 15900 17000 17300 10200 10700 10700 9550 9430 9440 844.8644 0.8 91xO.7 750.0658 0.3143 0.8 421.0777 127xO.3141 C 450 450 450 0.0843 1.728 0.2 516.0992 91xO.4318 C 600 600 600 0.813 0.0931 169xO.5099 C 700 700 700 0.3535 0.0 61 xO.930 11900 12500 12700 7810 7720 7720 6890 6810 6810 609.8632 0.8 421.772 0.) 4-12 B D B D B D B D B D B D B D B D B D B D B D B D B D Rated Strength Ib Number and Dia.265 21400 22600 23100 14300 14300 14300 12600 12600 12600 1126 1126 1126 Weight per Ib (Continued) .2 61xO.3 468.0663 0.6288 C 900 900 900 0.773 8200 8750 8800 5470 5410 5340 4830 4770 4720 421.5883 C 800 800 800 0. Conductor Ola.0908 127xO.5495 0.0905 91xO.929 0.4712 0.893 0.5491 C 750 750 750 0.7071 C 1000 1000 1000 0. in.773 0. Of Wires.6281 0.0972 169xO.2 703.0877 127xO.815 0.4315 0.8 609.0794 1.263 1.032 1.0807 1.7849 0.5892 0.l048 127xO. in.211 20000 20800 21200 13100 13100 13100 11500 11500 11500 1033 1033 1033 91xO.8 61xO.729 0.2 516.964 0.0887 1.855 0..209 1.5497 0.7850 0.0687 0.964 0.0715 0.9419 0.0742 0.3143 0.ll03 61xO.9423 0.bare aluminum wire and cable TABLE 4-8 (Continued) Stranding Conductor Size kcmil Square Inches 400 400 400 0.7072 0.031 1.7 375.965 12900 13500 13700 8410 8320 8310 7420 7340 7330 655.4324 0.9431 C Class (See foonotes at end of table.3924 0.7847 C 1100 1100 1100 0.855 0.1148 127xO.8 61xO.8644 C 1200 1200 1200 0.893 11500 11500 11900 7210 7130 7120 6360 6290 6280 562.0812 127xO.0994 127xO.1162 61xO.II45 91xO.l 032 91xO. 1350-H26 1350-H16 1350-H24 1350-H14 1.7 37xO.8 37xO.815 9110 9540 9780 6070 6000 5940 5360 5300 5240 468.l040 61xO.l071 91xO.093 1.3 61xO.l099 127xO.893 0.153 17700 18200 19200 12000 11900 11900 10600 10500 10500 936.3924 0.8 655.4714 0.7 375.1280 91xO.210 1.264 1.999 0.3 468.0859 91xO.8 609.998 13500 14200 14700 9020 8920 8900 7950 7870 7850 703.8 936.5103 0.0 844.3532 C 500 500 500 0.729 7440 7780 7970 4860 4810 4750 4290 4240 4190 375.0741 0.5892 0.8 936.000 It 1350-H19 37xO.0 61xO.2 703.094 1.153 1.5102 0.0845 127xO.0 562.2 61xO.4707 C 650 650 650 0.0842 1.855 10500 10800 11000 6620 6530 6530 5840 5760 5760 516.998 0. 100 1.1332 217xO.376 1.365 1.1195 127xO. and/or covered.9817 B C D 1300 1300 1300 1.571 1. 4·13 .526 1.505 30300 30900 32700 20200 20200 20200 17800 17800 17800 B 127xO.1439 217xO. Number and Dia.632 1.315 1.0960 1.258 1.1018 217xO. The outer layer of wires has left-hand lay.1003 217xO.158 59900 61200 62300 41600 41600 41600 36700 36700 36700 3344 3344 ! i ! C D B ! : .290 22300 23600 24000 14900 14900 14900 13100 13100 13100 1171 1171 1171 1.0911 i i i ! I B C D 127xO. of Wires.590 1.178 1. in. Square kemll Inches Class 1250 1250 1250 0.505 1.1122 169xO.0859 1.414 1.413 26200 27300 28300 17800 17800 17800 D 127xO.1157 169x0.316 23200 23600 25000 15400 15400 15400 13600 13600 13600 1218 1218 1218 1. Class C and D conductors are those for use where greater flexibility is required than is provided by Class B conductors. Class B conductors are those normally insulated.824 1.824 1. 1350-H19 135O-H26 1350-H16 135O-H24 1350-H14 1.l087 169xQ.9817 0.267 B C 1.l060 217xO.l052 1. Data shown are subject to normal manufacturing tolerances. I B C D .527 1.632 1.1191 169xO.021 C D 1400 1400 1400 1.999 1.1240 127xO.1270 271xO.0910 ! i Rated Strength Ib ! Conductor Dia. 127xO.l050 169xO.493 2000 2000 2000 1.099 1500 1500 1500 1.356 B C D 169xO.product identification and data TABLE 4-8 (Continued) Stranding Conductor Size .0860 91xO.0877 91xO.548 1..021 1.632 C D 127xO.1216 217xO.1172 127xO.460 28500 30200 30800 19000 19000 19000 B C D 127xO.527 31200 31800 33600 20800 20800 20800 18400 18400 18300 1841 1641 1641 1. 217xO. 2.375 1.289 1.413 1.0992 169xO.963 1.548 1.491 1.459 1.1284 127xO.290 1.099 1.0898 1.1403 169xO.1136 2. 25400 ! ! Weight per 1.0942 1.414 1900 1900 1900 1. in.178 1.1255 169x0.l088 .l032 217xO.549 32100 32700 34000 21400 21400 21400 18900 18900 18800 1688 1688 1688 1.158 2.571 2500 2500 2500 1.000 ft Ib 1311 1311 1311 91xO.0885 1.365 24500 26400 16600 16600 16600 14700 14700 14700 15700 15700 15700 1406 1406 1406 16800 16800 16800 1499 1499 1499 1593 1593 1593 .357 2.355 2.747 B C D 169x0.335 1. 23800 I I I I 1874 1874 1874 3344 1. B ! i 91xO.492 1.l073 1.257 1.460 1.316 1.l012 169xO.0973 217xO.374 1800 1800 1800 1.178 1600 1600 1600 1.354 1.963 1.412 1.748 2.504 1.591 33200 34500 35900 22600 22600 22600 19900 19900 19900 1780 1780 1780 35000 36400 37700 23600 23800 21000 21000 21000 C D .9815 0.998 1.335 1700 1700 1700 : 1750 1750 1750 1.159 2.749 2.021 1.415 1.335 1.824 42800 43700 45400 29700 29700 29700 26200 26200 26200 2366 2366 2366 2.0936 B 127xO.1176 271xO.590 1. C D ! B C D .999 52400 53500 54500 36500 36700 35600 31400 31400 31400 2838 2838 2838 2.962 3000 3000 3000 3500 3500 3500 B ! .1174 169x0. also for uses indicated under Class A (see Table 4·5 footnote 2) where greater fleXIbility is required.571 1.1223 169x0. 6 39.0 19 19 37 0.830 4.570 0.3927 328 372 447 468 6.640 5.350 1.423 0.000 16.336 0.658 0.603 0.0 266.1 62.475 0.0829 0.9 125 125 1. .150 0.414 0. In.2714 0.2711 350.328 0. in.0 19 19 19 19 0.4316 250.1662 0.213 0.1964 0.0 336. 4·14 .2609 0.603 0.360 8.310 3.09563 Conductor Slze.1662 157 157 198 198 .670 0.169 0.522 0.520 0.659 0. In.3122 0. but the compacting in the cabte somewhat offsets this by improving thermal transfer within the cable.5 795. 3. Non-Compact Dia.478 0. . 2.0206 0.2294 0.3651 0.124 0. The ac resistances at various temperatures are to be taken from Tables 4-6 and 4~7 tor the corresponding AWG or kcmil sizes.6856 0.0 397.660 4.2095 234 234 250 250 4.858 1.793 0.537 0.830 4.528 01318 0.724 0. The ampacity ratings of oompacHound bare conductors differ slightly from those of regular types of same sizes because of reduction of exposed surface.110 8.2642 281 281 315 315 5.520 0.376 0.990 2.419 0.940 15.292 0..0657 15.8654 0.160 2. Weight per 1000 It Ib 7 7 7 7 0.5 24.024 0.981 1.3043 0. of Wires 8 6 4 2 7 1/0 1/0 2/0 210 310 3/0 4/0 .0 500.475 0464 0.520 4.537 0. Sq. Area .510 2. i to normal manufacturing tolerances..722 0. Data shown are subject .146 0.023 1.5436 0.079 1.232 0.3746 0.4 7 19 7 19 0.593 0.1045 0.0 250.811 0.970 0.679 0..6856 4/0 7 19 7 19 0423 0.3421 300. 37 1.2356 0.0 874.574 0.AWG or kcmil No.1641 0.621 0.2749 0.0130 0.520 3.760 0.629 0.4371 0.932 0.6244 0.2642 0.400 0.2 78.736 0.336 0.5 954.7493 521 745 821 895 9.4 311 563 881 1.bare aluminum WIre and cable TABLE 4-9 All-Aluminum Concentric-Lay Compact-Round Stranded Bare Conductors Physical and Electrical Properties 135G-H19 Hard-Drawn ASTM B 400 These conductors have light~hand lay of outer layer. The values of GMR and inductive and capacitive reactances listed in Tables 4-6 and 4-7 may be used for compacted cable without significant error for usual design applications.1964 0.1045 98.480 5.8646 0.1912 0.368 0.8 7 19 7 19 0.4311 0.390 7.616 0. 3040 3. Sectional .0328 0.091 7 19 7 19 0.1148 0.188 1.430 5.0829 0.666 0.780 0.376 0.6866 0.960 6.0521 0.586 0.3418 0.570 0.567 0.2095 0. Direct current (de) resistance is computed on same basis as that of Table 4-6.373 0.268 0.1043 0.0 300..2356 0.134 0.8 266. I I de 20"C Resistance Ohms per Mile Rated Strength Ib ! .4 336. Compact Conductor Dia.5 477.020 05441 0. 4.184 0.1826 556.9 98.750 13.374 1.3040 0.1318 0.299 0.481 2.3380 0. 0.80 1.600 27. Direct current (00) resistance is based on 16.6 Jefferson.1864.1510 0.TW HoodlTW ac-60Hz de 1 1 Inductive Capacitive ! Conductor per ! Rated 2O"C 25'C 5O"C 7S'C' Size No.09830. Data shown are subject to normal manufacturing tolerances.10 1. 4.08580.3 1056 1267 1489 49 49 52 71 71 ! 4 4 1.0785 2648 ! 51.0670 0.432 i 0.0804 0.0.0454! 0.200 0.0889 0.0524 0._34_2--1_0.960 0.2 Adams/TW 3006.0854 0. !<cmil !Wires I Layers.1557! 0.rrw 2388.366 0.05611 0.0419 0.30 864.70 0.447 0.0932 0.2 10.0578~.5 17 17 17 17 2 2 2 2 0.0610 0.400 0.0252.0822 1976 2256 I 40.'ft at 20' 62% lACS conductivity.2463.60 0.0418 0.0.0520I0.8 761.27890.0625 0.1710.8 1123.31 13.200 0.40 1.0.80 0.100 0.0915 0.0570 0.1129 0.349 0.0465!0.produd identification and data TABLE 4-10 All-Aluminum Shaped Wire Concentric-Lay Compact Conductors AACITW Physical and Electrical Properties ASTM B no in Fixed Diameter Increments ! : Phase--to-Neutral 60 Hz.0501 0.11 5.056310. Ib' Ib Mile Mile Mile Mile I It 0. Resistance at One ft Spacing Resistance 1 • ! Code Word Logan/TW WheelerlTW Robsonrrw McKinleyrrw Rainierrrw Helens/TW Baker.0188: 421.1009 0.385 0.0319 0.1344!0. Properties of the industrial wires are those of the equivalent round wires of ASTM B 230.70 1.2001 0.0438 O.0540 0.0843 35.0974 322. Megohm Mile X.0411 0.0788 0.3140 0.375 0.0380 0.2055 i 0.0912 0.8 1583.04490.. of: Diameter 1000 ftSlrength Ohms! Ohms.2 Whitneyrrw • Weight I i 4 5 5 302.463 0.100 19.rrw 2083.0303 0.0865 1.482 ! 0.103010.0803 2528 I 45.0499! 0.0433 0.0736 0.0460.418 00406 0.0489: 0. Alternating current (ac) resistance is based on de resistance corrected for temperature and skin effe<:t.1012 0.0: 8.2259 0.80 1713 ! 31.5 449.030 0.045O!0.1094 0.700 23.00 1.357 0._07_68_ 1812.1048 0. GMR Ohms.1 ShastafTW 2667. 4·15 . in.4 595.0341 0.1181 0.0680 0.1225 0.395 0.2 31 31 31 34 3 3 3 3 1. 713.1464Io.0722! 0.0352 0.2855.50 1.7 Powell.0220' 558.0384 0. 2.086310.20 1.0385 0.0. of.100 0.727 ohm-cmi.900 0. 3.1227 0. Miles X.Ohmsl Ohms!.3425:0.0581 :0.0284 16.1 1346. No.90 918.000 : 0.700 0. 900 0.0 49 3 3 3 4 JessaminefTW Cowslip.0385 0.0994 0. Direct CUrrent (de) resistance is based on 16.1684 0.018 702.0976 0.300 0.5 600.1253 0.0903 0.2262 0.416 0.2 372.1545 0.0446 0.0192 0.236 1.661 0.01 31 2 2 3 3 0.7 846.0957 0.0807 0.100 19.1993 0. MiIesX~ kcmll Wires Layers TuliplTW Canna'TW Cosmos.0439 0.369 0.6 744.457 0.395 0.950 0.0i 17 795.419 0.0 2000.803 0.0968 0. Resistance ! ac-60 Hz at One ft Spacing Weight dc Inductive Capacitive Conductor per Rated 20"(.470 0.400 0.0333 0.9 468.1885 0.0829 0.0905 1.2673 0.799 1654 1890 2369 2843 30.0946 0.1131 175 0.8 11.500 18.0656 0.0861 1.0597 0.430 0.1384 0.0579 0.700 0.1089 0.0941 0. 17 17 17 17 2 2 2 2 0.700 24.0720 0.1088 0.720 0.377 1.4 397.775 0.06290.01 17 900.500 20.727 ohm-<:millft at 20° 62% lACS conductivity.2128 0.399 0.0830 0.2 1047 1122 17.0 2500.1603 0.5 11431.0 700.446 0.202 1.1459 0.0364 0.07850.bare aluminum wire and cable TABLE 4-11 All-Aluminum Shaped Wire Concentric-lay Compact Conductors AACrrw Physical and Electrical Properties ASTM B 778 Area Equal to Standard AAC Sizes Resistance Code Word Phase-la-Neutral 60 Hz.383 0.1131 0.400 50.600 27.0228 0.230 8.1936 0.0916 0.1009 0.0880 0. Data shown are subject to normal manufacturing tolerances.220 7.1051 0.1498 0.1040 0.900 15.6 897.0811 0.0244 562.TW 336.0884 0.1747 0.0757 0.0901 0.0 17 17 17 17 2 2 2 2 0.800 16.0760 0.0684 0.0272 0.919 0.0386 0.0896 0.0999 0.0350 0.530 8.TW LupinefTW TrilliunvTW '1750.377 0.0 11192.353 0.0325 0.0290 10.0829 0.095 1.1 10.0768 HawkweedfTW BlueballfTW Marigold'TW HawthomfTW 1000.0232 0.1096 0.1008 0.3284 0.460 0.7 12.156 1.1086 0.0927 0.1798 0. Properties of the industrial wires are those of the equivalent round wires of ASTM B 230.1 243 0.500 0. 3.1041 0.315 1196 1271 1346 1503 22.884 521. • 75°C Size No.400 13.2321 0.940 1.0882 0.0303 0.04720.4 0.3 9. 2.0951 0.0888 0.1848 0.0543 0.3010 0.1152 0.01 17 954.1404 0.1829 0.0478 0.1697 0.0338 0.0850 0.1616 0.0946 0.000 34.900 0.342 0.468 1.4 13. Alternating current (ac) resistance is based on de reSistance corrected for temperature and skin effect.0 500.0570 0.2319 0. of No.0679 0.0 49 49 71 71 4 4 5 5 11272.391 0.736 315.0922 0.2551 0.2215 0.0505 0.0710 0.0453 0.0.0 3000.0425 0.443 0.612 0.893 0.6 972.0631 0.'TW CockscombfTW MagnoliafTW 75O.1414 0. 4-16 00407 .2031 0.437 0.300 23.0848 0.057 1.0561 0.1184 0.1460 0.'TW Zinnia.433 0.0208 0.1590 0.07450.700 0.0281 .1033 Mislletoe.0986 NasturtiumfTW ArbUluS. 4.04120. 25°C 50"(. Mile ft MiIeX.0260 656.451 0.1018 0.990 1.0 11351.0439 0.0253 595.0.041 1.0794 0.0851 0.5 31 31 31 31 3 3 3 3 NarcissusfTW ColumbinefTW CamationiTW CoreopsisfTW 31 31 31 11590.5 1113.0604 0.1289 0.0 636.'TW MeadowsweetfTW OrchidlTW VerbenafTW 556.2737 0.648 1.2781 0.132 940.0518 0.1004 0.0807 0.0938 1.480 0.0 ! • 6.0362 00413 00411 00403 0.5 477.0931 0.0' 1033.1486 0.1 329 0. Mile Mile.4 446.0397 0. of Diameter 1000 ft Strength Ohms/Ohms! Ohms/Ohms! GMR Ohms! Megohm In.0518 0.0739 0.0316 10.1022 0.0374 0.0874 0.825 0.1850 0. Ib Ib Mile.500 42. -2617 397.1148 0.9 144. Code Word Size of Resistance ACSR Nearest AAC of Equal ac-60 Hz Dlam.758 0.0 608. 3.1878 0.02402 0.1441 ~. Direct current (de) resistance i.406 0.4309 0. 4·17 .250 0.5% lACS.40 3. with standard stranding increment of 2 percent. Stranding Resistance Ib Ib In.4 397.173 0. As the values of GMR and inductive and capacitive reactances of any all-aluminum stranded cable of a specified outside diameter are closely equal.7 11000 13300 15600 18600 0.3 155.316 0.1583 1.3402 0.755 ohm-cmillft.60 1.514 Azusa Anaheim Amherst Alliance 123.8631 0. As the difference is slight.1283 0. ASTM B 399 lists both Class AA and Class A stranding (see footnote 2 of Table 4-5 for explanation).347 0.0 795.554 0.182 0.2 19 37 37 0.6 21900 24400 30500 0.2697 0.878 0.-2617 477. interpolation from the nearest diameters readily obtains the desired GMR.6848 0. Alternating current {ac) is based on de resistance corrected for temperature.1490 0.028 0.376 0.816 0.4 740. see Figs.211 0.5818 0. etc. or Tables 4~6 and 4-7 may be used fOr the above table if the diameters are equa1.03824 0.927 0.0661 0.8 927.-2617 636.563 0.721 0.1327 0.47 7 7 7 0.00347 as temperature coefficient of resistivity per degree C at 20'C.502 0.1221 0.139 I ~.273 0.4 72.8 394.9 7 7 7 7 0. ConDiameter Size of Weight dc-20'C AWGor Approx.697 0.447 0.4 559.7282 556.1939 Butte Canton Cairo Darien 312. Data shown are subject to normal manufacturing tolerances.196 0.69 77.119 0.14 2.2 1110 1760 2800 3.322 0.8 336. 2.1902 0.1853 1.299 0.3098 0.58 48.9 182. 5.1537 0. For ampacity ratings of bare conductors.22 1.-26/7 556.1415 0.991 0. of Wire Diam.-2617 795.3 690.0834 0.1716 0.5437 0.228 Elgin Flint Greeley 652.642 0. In.3855 0. Sq. using 0.5 636. Area kcml! and Equal Mile in.129 0.858 0.5 45. it is trade custom to supply cables that meet the Class AA requirements unless othelWise specified.84 2.195 0.108 0. unless otherwise specified.953 0. and for skin effect.2286 0.396 0.1052 0.783 0.4394 266.1672 0.5 465..196 0. 4.-2617 336.9 433.5 477.9 521.09681 0.8 864. based on 19. the values of GMR. SO'C : 75°C per Rated Each duClor Ohms 25'C 1000 It Strength per Ohmsl OhmslOhms! Size No.5 19 19 19 19 0.1585 0.439 0.4 195.64 1/0 210 310 410 114. and the listings herewith apply to either Class AA or Class A. 52.148 0.601 0.7 246.276 0.373 3.648 0.41 1.2 4460 5390 6790 8560 0.6 367. etc.52 4.-26/7 266. at 20'C.05084 6-6/1 4-6/1 2-6/1 1/0-6/1 210-6/1 3/0-6/1 4/0-6/1 6 4 2 28. Mile kcml! Wires Mile Mile Akron AHon Ames 30.product identification and dote TABLE 4·12 AII·Aluminum Alloy Concentric· Lay Stranded Bare Conductors Physical and Electrical Characteristics 6201·T81 ASTM B 399 ACSR Equivalent Diameter These conductors have right-hand lay of outer layer.1436 0.254 0.476 1.5124 0.168 0.1631 0. 3·11 and 3-12 and adjust values according to method described in accompanying text.2456 0. It the same diameter is not found in Tables 4-6 and 4-7 as the above table.479 2.161 0.0 291.185 1.5 230.234 0.54 2. 255 0. interpolation from the nearest d~meters readily obtains the desired GMA.2358 0. As the values of GMR and inductive and capacitive reactances of any a!l~aluminum stranded cable of a specified outside diameter are closely equal.7 559.183 24700 26300 29600 32900 0.160 0.556 1.008 0.1257 0.1182 0.4 197. Resistance . 350.963 0.891 0.092 1.63 4.236 0.522 0. ! 500.883 0.3926 0. 0.1622 0.1539 i . 300.1418 0.464 0.952 0.1774 0.1470 0.1325 0.0974 i .5 No.77 4.471 0.6 19 37 37 37 37 0.646 0. of -Wires 7 7 7 7 7 7 7 Wire.363 0.7 932.811 0.2128 0.310 0.184 0. 0.058 2. 52.574 0.83 3.7854 699.1521 0.143 0.1 156.423 0. ! i ! i ! ! ! ~DHz 25'C I 500(.0206 0. 0.2364 0.215 0.1273 ! 0. . Direct current {de) resistance is based on 19..1357 ! 0. i 24.1560 0.4 . Area Sq. Ohms per Mile 949 1510 2400 4.337 0.599 8760 10500 11800 13400 15100 0.4318 0.182 I 0. 4-18 .5% lACS.701 0. it is trade custom to supply cables that meet the Class AA requirements unless otherwise specified.1644 0.198 0.283 16800 18900 20600 22300 23000 0.1 512. 0.00347 as temperature coefficient of resistivity per degree C at 2O'C.242 I 0.198 i 0.170 0.1228 . ! 750. etc. 800. As the difference is slight. ! Conductor Size AWGor kcmil 6 4 2 110 210 310 4/0 .5026 1.1219 0.3 373.129 .3534 233. 0.-.550 1. of Tables 4·6 and 4·7 may be used for the above table if the diameters are equal.1451 0.0772 0.3544 0. with standard stranding increment of 2 percent.1379 . 3~11 and 3-12 and adjuslvalues according to method described in accompanying text.997 1. Diam.133 0.218 0.6280 0.1 605. see Figs.928 0.04 1. If the same diameter is not found in Tables 4-6 and 4-7 as 1he above table. in.1963 0.262 0. ASTM B 399 lists both Class AA and Class A stranding (see footnote 2 of Table 4-5 for explanation). I .7072 0.1663 19 19 19 19 19 0. 5.434 0.0829 0.1935 0.6 839.392 0. 2.120 0..755 ohm.151 .0521 0. i 0.679 0. ! ! Weight per 1000 II Ib Conductor Diam.295 0.2748 0.1 280. Ohms! ! Ohms! Mile Mile Rated Strength Ib do-2Do(.508 0.4709 0. the values of GMA.91 3820 4620 5820 7340 1.1548 i 0. at 2ifC.7 652.159 0. Each .1317 0.171 0.bare aluminum Wlre and cable TABLE 4-13 All-Aluminum Alloy Concentric-Lay Stranded Bare Conductors Physical and Electrical Characteristics 6201-T81 ASTM B 399 Even AWG and kcmi! Sizes These conductors have right-hand lay of outer layer.20 0.1331 0.11 0.1147 0.629 0.5494 46S. elc. For ampacity ratings of bare conductors. 900. SOO.029 1.6343 0.5102 0.1375 0.3 37 37 37 37 0.7993 0.292 0. 1000.149 0.3 124.361 0.232 0.13 2..726 0. in.1045 0.602 4.0 326.232 0.. 650. 400. and for skin effect 4.3041 0.2660 0. unless otherwise specified.anil/ft.03 0. Alternating current (ae) is based on de resistance corrected for temperature.0 419.318 0.59 1.368 0. Data shown are subject to normal manufacturing tolerances.9 98. ! ! i 75°C Ohms! Mile --~~ 1. 550. using 0.1424 0.9 61.1638 0.5 38. 450.414 0.3142 ! 0. I in. 700.48 2.756 0. and the listings herewith apply to either Class AA or Class A.1739 0.0612 0.4258 0.6 745. ! i ! 250. .0328 0.197 0. 3.853 0..60 1.272 0.213 0.512 1.814 0.1064 0.183 0.5893 0.770 0. 2642 0.620 8.350 3.2820 0. Steel Reinforced (ASCR).1138 7x.1489 lx.800 266.700 19.743 0.0 365.0 614.0884 7x.0 655.0788 7x.257 0.1486 26x.325 0.900 Steel Standard Weight Ib CodeWord Clan Turkev Swan Swanate Sparrow Sperate AA-A AA-A AA-A AA-A AA-A 6 4 4 2 2 0.-- .0 746.0411 0.280 2.100 16.0 526.0961 7x.700 18.409 603.000 8.3628 0..100 17.260 13.927 0.1354 30x.450 4.) .200 19.860 2.100 11.l053 7x.360 2.1181 0.300 556.1045 0.783 0. Concentric-Lay Stranded ASTM B 232 with Class AA and A Stranding and Various Types of Steel Core Physical Properties Bold-face code words deSignate sizes most commonly used.1362 lx.300 20.810 2.9 246.4 28.6 449..3259 18x.800 .400 13.640 3.1137 30x.300 397.1217 26x..1672 6x.447 0.1410 26x.940 16.4 296. Steel Core in.0240 0.5 209.l029 1x.6 36.1367 7x.2436 0.880 7.3 81.5 448.900 26.700 16.8 241.250 5.160 1.3849 18x.000 18.8 300.6 58.0 249.100 18.1628 0.1217 7x.420 6.2095 0.3783 517.700 8.0653 6x.260 3.0 871.700 6.8 1.5 374.l052 lx.2642 0.300 16.6 18.300 9.858 0.900 23.410 8.500 20. Weight per 1000 Feet -- Total Aluminum Ib Ib TypeZlnc Coaling or Core e C Aluminum Coated (AZ) Core 1.1538 0.0 291.4938 0.4 0.1628 24x.------- - Osprey Parakeet Dove Eagle ..0 546.950 8.------- - 1/0 210 3/0 4/0 -------_.1672 lx.600 18.0383 0.1151 0.4 39.770 11.130 6.0 29.8 74.3177 289.4 336.780 9.760 2.0661 0.1 524.540 10.1489 0. Pelican Flicker Hawk Hen AA --------- 336.0 145.563 0.800 17.I463 30x.500 16.1628 7x.609 0.720 0.200 2.9 197.5 556.800 15.160 2.2 102.l059 lx.3045 0.3747 0.6 129.2 155.4372 0.341 0.0 39.2364 0.5 556.600 16.--- (Continued) .5 316.690 15.1261 1x.1878 lx.9 9.850 3.080 3.1074 18x.290 3.0 61.1236 30x.5 0.400 18.1758 24x.700 21.5 0.3 11.1486 7x.1052 0.680 0.300 21.316 0.3453 431.0 716.500 19.3122 0.1 375.3 11.0206 0.814 0.0328 0.7 70.1217 0.4621 18x..1219 0.USB 7x.980 4.120 1.0829 0.1486 0.4353 0.9 62.340 4.l013 26x.1367 0..0 230.1 93.3955 0.200 18.2 315.400 22.0608 0.2211 0.0 91.2 164.0657 0.0661 6x.-------- 12.4233 0.3070 0.l1Bl 6x.198 0.2789 0.0974 lx.914 0.--- ------ (See footnotes at end of table.0834 0.1758 0.640 .1 58.846 0.510 1.0940 7x.3159 0.0 446.355 0.0967 0.2652 0.3744 0.953 0.4 67.2640 0.800 22.050 6.2095 0.4 49.TABLE 4-14 Bare Aluminum Conductors.0 336.7 Robin Raven Quail Pigeon Penguin AA-A AA-A AA-A AA-A AA-A 1 0..4 124.1367 26x.9 46.900 9.3295 0.1878 0.1327 lx.300 12.390 1.200 25.540 13.883 0.250 0. ~~~~~ Rated Strength-Ib Outside Diameter Conductor Size --------- Area Square Inches Strendlng In.l 98.8 266.1029 0.3120 0.5 206.300 19.8 250.606 0.1299 36.9 523.398 0.600 477 477 477 477 0.3121 0.741 0.900 24.1662 0.5083 0.879 0.120 1.5 171.1181 lx.600 12.0 622.300 15.1 345.4 262.1318 0.680 3.7 13.500 23.4369 0. .530 15.3 44.0 366.760 3.0 521.1489 6x.9 191.760 2.0 462.680 14.642 0.550 4.800 13.950 3. 1052 7<.800 11.684 0..0 183.5 397.4371 0.502 0.0835 1x.600 13.720 5.000 11.300 7.100 21.1672 0.0328 0. f" '" M AA AA AA .0521 0.1878 115.2883 0.5 397.1261 0.1523 26x.5 ~ AA AA AA M .1327 0.200 6..600 27.3747 0.0 7B.2355 0.300 8.0 24.310 6.8 449.120 5.640 11.0 412.380 5.5 556.2 115.l059 0.190 1.4371 0.880 11.0 372.l015 7x.4621 0..2 523.0 765.1327 6x.1151 lx.0 145.I362 0.I299 0.2738 0.4 39.3747 0.5 317.0 6. Waxwing Partridge Ostrich Merlin Linnet Oriole AA AA AA AA AA AA Chickadee Ibis M Lark M .2505 0. AWG or kcmil Alumlnum Total Aluminum Steel Complete Conductor in.0521 0.900 18.0834 7x.5391 18x.0772 6x.0661 lx.0834 lx.000 12.0767 0.650 10.1939 6x.0 57. 100 22.303 0.400 39.596.6244 0.7492 0.600 32.1273 7x.6156 48x.426 --- 87 5 0.000 0.140 1.259 1. 0.1213 c----- -~ 1.1628 45x.900 27.0 939.600 22.200 26.300 24.--95.l111 1.5133 36x.1436J.600 13.03 .300 27.408 Aluminum Steel Standard Ib Ib Weight --.040 1.400 16.000 30.165 1.150 1.196 1.----.1749 30'.6244 0.9 1022 748 ..700 --.9854 54X.1588 26x.400 29.8 37.940 0.-.8010 45x.5 ( .6347 54x.0 873.800 39.1420 ---- +----- i 0.5 0.148 0.1 22..437 690.5 ( 5 1.162 0.---- 1l.l049 1'11~( 1.Conductor in.283 0.----.245 1.1329 ..100 21.----' .977 7x.6417 0.800 21.000 -----15.600 29.t~824 1126 1013 847 648 1158 1.0874 1.600 32. .200 .5634 - Towhee Redbird Cardinal Ortolan AA AA Curlew Bluejay Finch Bunting Grackle - ' l AA AA AA AA -----~- (See footnotes at end 01 table.1151 7x.0971 95 0..0 818.5 30.1880 0.9164 54x.7049 36x.200 25.""~ TABLE 4-14 (Continued) ---~--- Q :onductor Size Outside Diameter --- Area Square Inches I Class I Code Word AW' I [----.------0.~ 1430 1342 1531 ---- \---- .700 674.387 804 745 1024 750 1093 749 751 1234 895 748.700 40.446 1163 1329 00489 0.1994 7x.1456 19x.0 --.1659 7x.333 0.8 23.500 33.1213 7x.930 0.4749 0..1414 7x.1880 lx.175 0.1383 7x.5617 0.5275 18x.0552 54x.400 146.7494 0.4994 0. " ---~ Aluminum Coated (AZ) Core -- (Continued) .1544 19x. 21.192.600 569.600 32..4956 0.000 37.900 344 31.1820 26x.0852 r-- --.0 832.7494 0.400 22.5808 26x.1525 30x.700 31.800 35.0886 7x.463 TypeZincCoallngorCore .600 ' 34.800 600.900 13..200 22.0 920.1360 19x.100 30.7264 0.5 0.l097 95 0.500 - 628.2184 7x.200 598.399 0.051 0.800 27.03 .300 22.5620 0.092 1.6674 0.900 28.500 28.1628 0.r----- 16.994 .l085 0.000 23.192.-i. I--.4995 AA AA AA AA 66 71 71 71 Condor 795 5 AA~' 79 AA 79 5 AA 795 AA 79.--.000 20.700 39.-----.900 30.000 674.4751 0.7 596.5643 24x.l010 1.291 0.4 93.400 23.6247 0..400 27.400 15.7491 0.196 1.300 35.5 AA 795 Crane Ruddy Canary AA AA AA Corncrake AA AA AA AA AA Coot AA Cuckoo Orake Maliard Tern - 0.019 .7053 0.600 24.-.7066 0.293 1.4753 0.500 31.5917 24x.----.600 28.7669 0.SOO 30.800 --~ 899 899 899 899 899 973 973 roo - 1054 1123 1128 .0971 954 0.1216 0..326 0.1456 7x.0 246 26.600 376 219 403 39.1628 7x.1486 7x.6135 30x.700 598.200 31..8673 45x..345 0.2 208.0 47.300 571.1151 1.365 0.--- 7x.---- --~ .3 25. 570.200 28.5620 0.6242 0.8465 24x.6240 - Aluminum Complete -.800 29.900 27.400 31.315 0.8 26.1329 54x.100 22.600 26. -----~~-.966 0.415 0.6535 26x.4995 0.1486 24x.l059 7x.----1..8 219.8462 54x.291 0.300 28.8112 0.5522 0. _ -1-----.0 1109 .----- 0.000 21.302 1.800 16.700 31.600 ---- 30.0 984.6673 0.400 24.--.1273 901 0.800 25.600 16..400 29.000 ------ 175 176 224 329 329 - 190 356 25.600 13.500 33.0014 45x.400 675 34.. 1085 1.500 37.5238 0.318 0.1291 .329 0.--0.500 24.100 21.092 Steel Core in.7492 0.300 30.063 1.108 1.".200 24..300 25._- lx.---.364 0.100 25.600 26.1291 7x.5370 0.600 ' 33.800 21.--.6 15.953 0...100 37.2 386.r------ 0.8011 2Ox. Steel 24x.400 166 310 31.326 0.5 367.700 23.700 26..6245 0.) Total Ib 0.400 23.431 0..133 0.300 24.000 24.131 1. -- 0.7 1.1329 95 0.Alumior num Total kcm ii -- Peacock Squab Teal AA AA AA Kingbird Rook Grosbeak Swift Egret Flamingo Crow Starling Redwing 60 5 605 605 AA AA AA AA AA 63 63 636 63 63 0.100 24.1564 7x.188 0.2 309.858.200 25.600 26.100 274 28.7764 54x.081 I----- t- 6 5 5 5 Stranding in.7965 54x..0926 1.300 29.000 28.400 20.700 28.500 33.2 22.990 0.367 0.. ----- Weight per 1000 Feet ---- -~ Rail Rated Strength-Ib ---- ----- .0943 90' 0.900 27.1 261..000 --14.113 ( 5 0.165 1.0 0.400 24..800 59 274 27.8112 0.1667 7x.0 643.-.I--.600 25.212 1.000 275.800 32.1573 7x.500 29.9 24.7555 45x.364 ---- 1.266 0.--0.700 36.0 967.1383 5 0.800 35.1410 7x.o8~ 1.382 0.338 ---- B C -- 779.6897 3Ox.1213 r------..600 434 - 1..- 302 31.040 0.1329 7x.356 0.8 r---.1486 19x.7069 0.1329 lx..100 26.9350 45x.4997 0.000 30.500 483 38.100 25.0892 .1329 0.700 27.0 13.400 23.400 29.100 32.1290 1.1515 7x.0977 7x.399 1074 1075 1123 1226 1228 0.000 .1186 19x.I---.2 229.000 41. 437 0.1327 ~~ Guinea Dotterel Dorklng Brahma Coch!n AA AA AA AA AA 0.300 33.100 54.7 189.1880 54x. and are used for ground wires and for extraAong span construction .2200 .156 2.9993 1.700 ----- 48.4 179.0 254. 34.900 45.400 20.1235 1.700 46.272 1.500 45.0949 lx.890 9.6 0.1856 1.990 4.762 1.0 441.431 1.780 2.357 0.400 35.461 0.BOO ------ 48.600 15.800 41.800 59.3986 1.700 .8 203.1819 Rated Strength-Ib I~~ Complete Conductor In..1535 45x.400 11.0977 7x.1628 45x.0 625.700 15..5 2.1240 1.300 16.424 7x.1249 0.200 26.1327 ~ ~ ~~ ------- TypeZincCoatingorCore B C Aluminum Coated (AZI Core in.100 43. ~ ~~~ .1266 .1 95.0 5. HIGH~STRE -------- ~-~~ ~ ~~~ Bobolink Ptover Nuthatch Parrot Lapwing Falcon ~~~~ Outside Diameter ~~~~ 1198 1205 1273 1279 ~~- 234 429 248 456 ~ ~~~ 1348 1355 1422 1429 1498 1505 ~- r~~ ~ 263 483 278 509 292 537 .168 54x.200 39.9 198.0847 .1958 Chukar Mockingbird Bluebird Kiwi Thrasher Jorea AA AA AA AA AA AA AA AA AA AA AA AA 1.l030 1.1127 12x.900 45.100 55.900 40.500 48.7758 1. 0.502 0. Dala shown are subject to norma! manufacturlng tolerances.6931 1.8309 1.735 1.800 17.1 166.200 10.1735 76x.0628 AA 101.505 1.1121 19x.1122 19x.1977 .0 336.600 36.900 .000 25.700 37.3177 149..100 51. Weight per 1000 Feat Steel Core Grouse Petrel Mlnorca Leghom GTH S RANDINGS 80.347 0.100 59.700 ------- 0.300 41.382 1.0961 12x.1189 19x.607 0.663 0.500 51.576 0.034. 49.100 40.1057 AA .3453 0.700 Aluminum Steal Standard Ibs Ibs Weight ~~ 7x.590 1.600 47.300 13.700 39. ~_ L •.2 16.407 0.0 73.661 1.0814 19x.400 43.400 40.9 103..0961 7x.336 0. 1685 1929 2040 2051 2188 2384 ~ r-' .5122 1.600 17.312 2.900 27.802 1.0614 1.------- ------ 7x.0 0.631 0.8155 1.3642 0.475 1.0614 1.351.1674 8x.1598 0.7022 1.. The High-Strength Conductors listed at bottom of Section 148 of this table have a high ratio of mechanical strength to ampaclty.800 43.9750 1.1389 0.1348 1.400 38.700 5O.1 172.000 49.l059 159.1716 84x.714 0. 3.1 326.2763 0.481 0.510.240 10.800 56.1672 45x.3 485.700 28.200 46.800 60.8 0. ~~~-~ Total Aluminum ------- Blttem Pheasant Dipper Martin AA AA AA AA 1.. 2.700 34. Class A stranding is for conductors to be covered with weather-resistant materials. Class AA stranding is for bare conductors on overhead lines.1214 7x.386 1.3981 396.489 0.1660 ~~~~ 1.000 17.0921 7x.3355 1.0 527..2492 1.0 75.0870 AA 134.376 0.200 38.9 274.0 276.l000 12x.700 42.8 246.367 0.481 0.167 2.1155 19x.600 36.431 1.300 49.0921 7x.100 32.000 46.300 18.900 46.2 211.600 4.2681 1..500 37.800 18.1157 19x.5979 1.3020 .1261 19x.4072 1..0977 7x.400 4.1744 76x.1681 84x.0676 1.100 0.200 15.504 1.100 19.000 36.1151 7x.425 I- ~~- 2072 2163 2508 2300 2523 2749 .465 1.9 127..0921 12x.800 32. 367 234 468 249 335 365 ------ ~-~ ~~~- 51.366 0..6671 1.0 176.9144 2.5 1.5 1.0828 45x.2373 .9 190.2012 12664 1.1832 54x.1582 Steel ~~~~- 45x.200 54.1862 1.400 54.3 .0874 7x.347 0.300 49.500 57.1670 0.0 476.400 42.461 0.900 1.345 1.516 ~~ ~~~~ 1611 1836 1700 1938 1790 2042 .8 0.515 1.1151 12x.5 1.300 13.2883 0. .100 48.880 1432 1634 1521 1735 ----- 0.1733 54x.1783 54x.530 0.000 16..602 1.0961 7x.1059 ~~~-~~~ ~~~~ Total Ibs 0.545 19x.TABLE 4-14 (Continued) ~ Conductor Size -~~ CodeWord Class AWG or kcmil Area Square Inches Aluml num Stranding in.100 17.000 12.500 45.0800 AA 110.9 158.466 1.700 48.0 149.460 10.510.5 0~9987 0.3357 1.1261 16x.2489 1.100 12.336 0.470 9.900 46.6 296.400 53.100 57.1670 7x.700 61. .4885 0.1 209.1499 0.590 1.800 59.427 1.1259 1.300 50.800 10.272 1.910 9.351.1253 19x.1378 .1602 72x.800 14.3783 0.1221 19x.200 34.l003 7x.1214 12x.0850 .800 60.. 14.1456 72x.2628 12x. 3.7678 0. 3-13 and 3-14.bore aluminum wire and cable TABLE 4-15 Bare Aluminum Conductors.774 1.723 i 0.1423 0.621! 0. 0.'-L.! ~::!lJH_!.499 .586! 1.00404 as temperature coefficient of resistivity pel'.363 110 145 145 195 195 250 ! ! ! i 350' 0.537 i 0. Stranding ac-60 Hz 60 Hz Reactance X~ I--.1160 0.1060 1.:._~_i_~_-.5353 1. 101.553 0.000 0.175' 2. 1189~ 1214.582 0.0901 0.150..1291 2.677 0..858 0.:. with standard increments for stranding. Currents assumed in calculating magnetization effect in percent of assumed 7S"C current: 2SOG-10%.563 1..614 0. and for effect of core magnetization using method of Lewis and Tuttle.1250 0. 0.580..588 0. Power Apparatus and Systems.1285 0.590 0.1147 0.552 1.-L_~.787 0..755 2. 1959.572 0.598' 0.564' 0..041 0. Currents assumed for magnetization calculations in percent of assumed 7SoC current: 25'C-10%. .601 0. 1189-1214.646 0. Altemating current (ac) resistance is based on dc resistance corrected for temperature using 0.8410 : 0. 0. 1.0029 per degree C for steel core.753' 1.8 134. pp.865' 0.city ratings see Figs.64 ohm-circular mil/ft. Feb. (8.946 ohm-cmitlft.~~_~_::.1276 1.-_g_·r_:_5-L. NOTE: For amp.960 4.862 0. Power Apparatus and Systems. 50"C-75%.587 0. and adjust according to method desclibad in the accompan'l'ng text. 0.1131 0.611 0. Steel-Reinforced (ACSR) Electrical Properties of Single-Layer Sizes Resistances (Approximate) .6323 0. Feb.r.626 .574 i 0.r.628 0..020' 0. Inductive reactance includes magnetization effect of steel core calculated using method of lewis and Tuttle.---.-~_·_r_.-i_!.638 0.596 0.8360 0.538 0.548 0.563 0.1091 3.687 0._~:_i~7'~.0617 0. 1 ft Equivalent 7SOC Conductor 75'C 20'C 2S'C 50'C 25'C 50 C i 75"C Spacln~ Hz Size Current i Ohms! Ohms! Ohms/ Ohms! Ohms/ Ohms/ Ohms/ r::::----- Code Word kemll AI.613 0.__~_:i_L_~:_ _ .929 0.-_~·_~_~i---.1354 0.254 1. Steel i Amps Turkey SWan Swanate 6 4 6 : 6i 4 Sparrow Sparate 2 2 7' i 6 7 1 1 1 1 1 Robin 1 6 Raven 110 210 310 410 6 6 80.674 0.308 2.546 0.1182 0.1107 0.694 0.114' 0. 4-22 .524' 0.2% lACS) at 2O"C for the nominal aluminum area of the conductors and 129.6 159.651 0.----J Assumed Q.578 0.549 0.1.306 1.--------1lnductlve Reactance X•• 1 ft Equivalent Spacing' Capacitive (Approximate) de . PP.087 0.179 1.734 0.434 1. degree C for aluminum 1350 and 0.l.1345 0.531 i 2.637 0.652 0. _~_r_~_:-.556 0.!.358 i 1.446 2.654 0. ASTM B 232 2.6679 .629 0.6341 0.c! 1.509 0.517 i 0.3381 1. SO"C-75%..3230 220 255 295 340 390 200 265 300 330 Mile 3.3893 2.094 1.799 0.4612 0. 1959.1173 0. (61.427 1..853 0.527 0..8 110.727 1.4199 1.741 0.760.113 1.606 0. 12 12 12 12 1 7 7 7 7 ~~6 9 12 7 Quail Pigeon Penguin Grouse Petrel Minorca Leghorn Guinea Dotterel I 6 6 8 1 i 1 1 1 1 Mile Mile Mile Mile Mile Mile i Megohm-Miles 3.380 1.873 0.608.J'_I_~.670 0.590 0.763 0.1240 0.512 0.1216 0.617 0.607 0.460 2.599 0.537 0.0% lACS) for the nominal steel area.621 0. Direct current (de) resistance is based on 16.5297 '0.247 1.141 0. 1248 0.426 0.153 0.425 0.415 0.153 0.140 0.0352 0.128 0.4 336.1417 0.330 0.403 0.129 0.153 0.128 0.0988 0.399 0.128 0.1410 0.0319 0.0304 0.435 0.6 715.0912 0.415 0. 0.118 0.1135 0.477 0.141 0.5 241 261 301 181 241 7 7 7 7 2 2 2 2 2 Dove Eagle Peacock Squab Teal 556.4 397.162 0.0313 0.0327 0.229 0.168 0.146 0.1030 0.234 0.271 0.158 0.1420 0.160 0.194 0.148 0.252 0.297 0.5 477 301 181 261 301 181 7 Flicker Hawk Hen Osprey Parakeet 477 477 477 556.5 Coot Cuckoo Drake Mallard Tern Condor Crane Ruddy Canary 1 7 7 1 7 1 7 7 1 1 GMR (See footnotes at end of table) 4-23 .183 0.114 0.300 2 2 2 2 2 0.128 0.0335 0.168 0.175 0.393 0.423 0.2693 0.1475 0.432 0.344 0.5 900 900 541 7 451 7 541 7 3 3 3 0.1613 0.0277 0.0283 0.0221 0.138 0.412 0.183 0.1620 Capacitive Megohm-Miles X'• It Inductve OhmslMile X.0230 0.1002 0.441 0.117 0.117 0.130 0.196 0.458 0.164 0.180 0.463 0.276 0.101 0.411 0.0374 0.0284 0.324 0.0361 0.279 0.103 0.141 0.424 0.102 0.198 0.0392 0.0392 0.166 0.0328 0.0265 0.5 556.420 0.0368 0.166 0.184 0.405 0.119 0.0355 0.0980 0.0372 0.303 0.233 0.274 0.176 0. Steel Reinforced (ACSR) Electrical Properties of Multi-Layer Sizes Resistance Phase-to-Neutral.0932 0.200 0.174 0.166 0.231 0.147 0.0301 0.145 0.257 0.124 0.254 0.0263 0.1129 0.1490 0.395 0.231 0.0946 0.0925 0.0342 0.327 0.418 0.0902 0.0375 0.0965 0.0928 0.366 0.product identification and data TABLE 4-16 Bare Aluminum Conductors.2993 0.0917 0.273 0.0306 0.0327 0.451 0.1629 0.162 0.2279 0.232 0.229 0.107 0.167 0.173 0.399 0.130 0.1254 0.0944 2 2 2 3 2 0.159 0.3398 0.115 0.117 0.195 0.0898 Stranding A!.0904 0.0920 0.1602 0.406 0.0957 0.406 0.1883 0.410 0.1008 0.347 0.2671 0.1899 0.0217 0.415 0.1146 0.5 715.153 0.116 0.377 0.182 0.416 0.0387 0.401 0.100 0.104 0.1122 0.191 0.8 266.0197 0.1485 0.5 605 605 605 261 7 301 7 241 7 261 7 30/19 2 2 2 2 2 Kingbird Rook Grosbeak Swift Egret 636 636 636 636 636 181 1 241 7 261 7 361 1 30/19 Flamingo Crow Starling Redwing 666.104 0.182 0.127 0.0969 0.1411 0.1403 0.5 397. 336.1869 0.0290 0.306 0.172 0.0917 874.0372 0.0335 0.412 0.139 0.0957 0.127 0.5 556.412 0.107 0. 60 Hz Reactance at One It Spacing ac--60 Hz dc 20°C Ohmsl Mile 25°C 50°C 75°C Ohmsl Ohmsl Ohms! Mile Mile Mile 2 2 2 2 2 0.106 0.106 0.0244 0.0992 0.0953 0.5 397.1352 0.0240 0.0351 0.430 0.1248 0.212 0.1135 0.214 0.142 0.193 0.181 0./St.1143 0.0964 0.166 0.140 0.0300 0.151 0.0937 241 7 541 7 261 7 30/19 2 3 2 2 0.0943 0.154 0.4 181 261 261 181 261 Oriole Chickadee Ibis Lark Pelican 336.0907 0.399 0.452 0.2650 0.277 0.153 0.465 0.0981 0.119 0.142 0.0950 0.129 0.441 0.2260 0.1889 0.445 0.144 0. Number of Aluminum Layers Code Word Size kcmil Waxwing Partridge Ostrich Merlin Linnet 266.125 0.393 0.139 0.103 0.336 0.199 0.3364 0.8 300.141 0.210 0.399 0.0255 0.0335 0.382 0.0951 0.2243 0.432 0.5 715.0920 795 795 795 795 795 795 361 1 241 7 261 7 30/19 451 7 541 7 3 2 2 2 3 3 0.106 0.213 0.109 0. 0829 0.101 0.0878 0.0910 0.385 0.0846 0.0666 0.0480 0.0798 0.64 ohm-cmillft.0742 0.355 0.5 1192.108 0.0396 0.0805 0.364 0.0847 0.05714 0.0710 0.0922 0.0391 0.bare aluminum wIre and cable TABLE 4-16 (Continued) Resistance Code Word Size kcmil Comcrake Rail Towhee Redbird Cardinal 954 954 954 954 954 Number of Aluminum Layers dc 20'C Ohms! Mile 2S'C SO'C Ohms/ Ohms/ Mile Mile 7S'C Ohms/ Mile 7 7 7 7 7 2 3 3 2 3 0.5 1033.0385 0.0759 0.0508 0.5 1590 1590 1780 45/ 7 54/19 45/ 7 54/19 84/19 3 3 3 3 4 0. 1.0416 0.0521 0.08798 0.0466 0.0856 Bittern Pheasant Dipper Martin Bobolink Plover 1272 1272 1351.0431 0.0477 0.5 1431 1431 45/ 7 54/19 45/ 7 54/19 45/ 7 54/19 3 3 3 3 3 3 0.0756 ohm~cmil/ft.0641 0.358 0. 3-13 and 3-14.348 0.0751 0.393 0.0498 0.0729 0.0570 0.08728 0.374 0.390 0.368 0.0522 0.0673 0.365 0.0950 0.109 0.04229 0.395 0.0796 0.09526 0.118 0.0783 0.0954 0.03643 0.109 0.0588 0.118 0.0820 0.0947 0.0674 0.5 1113 1113 1192.380 0.0472 0.0717 0.07122 0.0459 0.102 0.0898 0.0516 0.108 0.0788 0.0874 0.0404 0.117 0.06017 0.0939 0.0983 0.0484 0. The effective ac resistance of 3-layer ACSR increases with current density due to core magnetization.099 0.0528 0.0699 0.0851 0.0898 0.0445 0. 4.0459 0.348 0. Alternating current (ac) resistance is based on the resistance corrected for temperature using 0.396 0.0436 0.0757 0. 60 Hz Reactance alOne fI Spacing a~OHz GMR Inductve Ohms/Mile Capacitive Megohm-Miles fI X.0880 0.0507 0.0945 0.0828 0.0681 0.0454 0.367 0.0611 0.0428 0.08161 0.0872 0. Direct current (de) resistance is based on 16.0721 0.0890 0.0555 0. see Figs. and 129.0804 0.0814 0.0837 0.05699 0.378 0.0658 0.0561 0. 4-24 . For ampacity ratings of bare conductors.0600 0.0890 0.0775 0.099 0.0867 0.0495 0.0553 0.0765 0.0491 0.392 0.0451 0.5 1510.0829 Nuthatch Parrot Lapwing Falcon Chukar 1510.386 0.338 0. and for skin effect.376 0.0534 0.04488 0.0896 0.0803 Mockingbird Bluebird Kiwi Thrasher Jaree 2034.06003 0./St.5 45/ 7 54/ 7 45/ 7 54/19 45/ 7 54/19 3 3 3 3 3 3 0. ASTM B 232.946 2.101 0.5 1351.372 0.0859 0. (61.343 0.0779 0.110 0. X'• 0.07146 0.0822 0.0620 0. 20/ 45/ 48/ 24/ 54/ Phase-to-Neutral.06352 0.0840 0.0378 0.362 0.0838 0.344 0.382 0.09452 0.0649 0.06706 0.0734 0.04228 0.371 0.0996 0.0486 0.389 0.108 Stranding Ai.0562 0.0864 0. with standard increments for stranding.0420 0.07600 0.2% lACS) at 20°C for nominal aluminum area of the conductors.06332 0.5 2156 2167 2312 2515 72/ 7 84/19 721 7 76/19 76/19 4 4 4 4 4 0.0821 0.0591 0.0549 0.08138 0.108 0.0950 0. See Chapter 3 for details.0890 Ortolan Curlew Bluejay Finch Bunting Grackle 1033.0609 0.0621 0.07619 0.03960 0.05119 0. (8% lACS) at 20°C for the nominal steel area.118 0.0775 0.0848 0.00404 as temperature coefficient of resistiVity per degree C for aluminum and 0.0029 per degree C for steel.0897 0.0931 0.0767 0.0706 0.0855 0.0401 0.0886 0. 3.117 0.06724 0.0994 0.0485 0.098 0. 740 52.1829 0.100 138.2644 0.447 1.6262 0. multiply value from Fig.2239 0.1915 0.2705 0.1878 0.5 702.300 21.540 13.000 477.000 624.1 i 19.140 6.2588 0.000 477.6 392.0 520.400 13.5747 0.100 168.500 43. and diameter of core.080 15. The values in Tables 4-15 and 4-16 may be used for GMR.2188 0. PelicanlAW Ricker/AW HaWkiAW HenlAW OspreylAW 477.9938 0.2185 0.102 2.740 41.690 6.600 Waxwing/AW PartridgelAW OstrichiAW Merlin/AW LinnetlAW 266.2254 0.451 1. inductive reactance.000 0.800 504.4601211.100 403.230 2.100 341. For approximate ampacity.1451 0.7 68.9 86.1888 0.2536 0.246 1.620 66.1621 0.800 26.3261 0.3767 0.2294 0.800 629.000 556.1658 0.537 I 54.400 413.3 584.500 397.1819 0.4965 109.1562 0.400 336.500 I ParakeetJAW DovelAW Eagle/AW PeacockiAW SquablAW 558. 305 X (220.411 1.600)'" 311 for Penguin!AW.700 9.1841 0.665 1.600 (See footnotes at end of table) 4-25 .2 219.2007 0.600 0.6 62.630 87.370 69.1578 0.252 0.1916 0.1980 507.6 440.3257 0.2233 0.1477 0.6 I 11.1779 0.2310 I 0.1803 0.1823 0.060 2.1493 0.200 589.170 70.4105 0. diameter of complete cable.500 556.2458 0.820 10.2994 0.800 21.2210 0.2663 0.2903 0.000 410.100 8.3 356.6568 0.1783 0.6457 0.500 558.250 5.000 I ac--60 Hz de :WC Ohms! mile I i I ! I i 5O"C Ohmsi Mile I Weight per 1000 It Ib 75°C Ohmsl Mile 2.516 2. the number of wires and diameter of wires in strand.800 19. the values in Table 4-14 (A and B) may be used for cross-sectonal area of aluminum wires.581 1.285 2.2051 0.800 300.993 1. Aluminum-Clad Steel Reinforced (ACSRlAW) Physical and Electrical Properties NOTE: For a cable of same dimensions and Code Word.1531 0.829 1.500 397.900 584. Hence.3654 0.3252 0.295 1.2725 0.4083 1.1875 0.1838 I 0.4 624.800 174.1610 0.2484 0.1936 0.047 0.000 477.2841 0. for Penguin at 60" rise Fig.9121 0.400 420.600 496.9 463.2586 0.300 277.0 747. Thus.3360 0.370 54.400 ! I II ) i Total Aluminum Area cmil 25"C Ohms! Mile 2.1764 687.1621 0.1570 0.2256 0. and capacitive reactance.2621 495.700 220.046 1.2192 I 0.360 66.1722 0.9 357.760 3.1786 0.500 .005 1.4 276.700 579.690 105.5 136.product identification and data TABLE 4·17 Bare Aluminum Conductors.2072 0.1 442.3543 0.6 491.780 2.5 349.800 211.3328 0.5126 0.700 312.600 133.2 589.500 16.2962 0.800 12.000 350. 3-13 or 3-14 by the square root of the ratio of the total aluminum area to the aluminum wire area in circular mils.4149 1.4557 1.309 2.400 Oriole/AW ChickadeelAW BrantlAW IbisiAW LarkiAW 336.1484 0.400 397.7883 0.7 792. = Resistance I Area of Aluminum Wires emil ACSR Code Word SwaniAW SwanateiAW SwaJlOWiAW SparrowlAW SparatelAW 41.700 19.320 110.8304 0.8 99.321 1.9136 0.1759 0.2407 0.3162 253.3981 0.510 3.2532 0.7235 0. I I ! ! I Rated Strength Ib 1. 3-13 shows 305 amp.5 729.200 574.260 2.2898 0.150 0.500 16.000 605.800 266.280 2.2762 0.1 819.5233 0.500 397.780 14.500 605.700 492.026 0.300 0.2 174.0 591.3094 0.1869 0.400 270.000 336.2143 0.2105 0.2262 0.000 23.460 4.3435 0.000 23.360 Robin/AW RavenlAW QuaiUAW Pigeon!AW PenguinlAW 83.2678 0.9 i ! .470 44.300 7.8 0. total cross-sectional.632 1. 052.000 1.400 1962 i 2015 2439 2265 2475 .L-- ! i .500 .000 656.431.590.04883 Rated Strength Ib I 0.07772 0.000 1.06372 0.1169 0.09418 0.500 1.09254 0.1512 0.1129 0.07949 0.700 SO.0504 0.07726 0.455.0654 0.07211 0.0593 0.1454 0.000 49.1408 0.000 636.900 I ! i .1346 0.1049 1.08515 0.520 1081 988.200 970.1494 0. ! I 40.200 33.08175 0.000 0.08863 0.08009 0.033.06407 0.600 23.07791 0.05575 0..bare aluminum wire and cable TABLE 4-17 (Continued) Resistance a0---60 Hz Weight ACSR CodeWord Area of Aluminum Wires emil Total Aluminum Area emil de 2O'C Ohms! mile 25°C Ohms! Mile 50'C Ohms! Mile TeallAW Kingbird/AW RookiAW GrosbeakiAW EgretJAW 605.343.08868 0.000 (See footnotes at end 01 table) 4-26 ! i ! i I I ! 1.000 2. 0.1389 0.590.000 808.SOO 41.07332 0.500 BobolinkiAW PloverlAW Nuthatch!AW ParrotlAW LapwinglAW 1.1107 0.500 900.817.200.09585 0.394.000 1.08682 0.000 1.500 1.05476 0.0416 0.1281 0. i I 0.04705 0.0563 0. ! i .510.900 672.1235 0.1039 0.900 1135 1275 1224 1374 1311 27.1589 0.500 821.000 795.1363 I 0.07548 0.1512 0.113.1006 0. i I ! 0.09938 0.1448 0.000 1.1105 i ! I i 0.000 1.300 37.1004 0.0751 1.294.900 01317 i 0.06669 --.192.700 39.1378 0.400 45.641.0741 0.06131 0. i i i 0.300 .970 31.000 24.SOO 1.375.1141 0.272.000 2.000 1.0939 0.000 639.09704 0.700 53.213.130 55.000 795.09872 0.156.200 29.0555 0.1373 0.510.300 0.05187 0.1104 0.1214 0.1143 0.230.1127 0. GrackleiAW Bittem!AW PheasantlAW DipperlAW MartiniAW 1.700 59.000 1.500 1.1141 .1207 i 0.000 1.09087 0.1251 0.04528 0.1366 0.1014 0..000 1.1193 01357 0.500 27.07491 0.100 37.000 1.08689 0.133.113.SOO 820.4 981.000 636.06488 0.04805 0.1167 0.400 915.1213 0.000 954.600 47.400 32.000 1.0886 O.000 1.000 1.05533 0.000 2.06575 0.07567 0.1110 0.05242 873.0663 0.800 29.0 883.0817 0.07369 0.000 1.1142 0.000 954.1253 903.0391 _ _--'-_ _ ~.700 661.000 1.400 42.1320 0.536.000 1.1252 0.068.000 Falcon/AW ChukarlAW BluebirdlAW KiwilAW Thrasher!AW 1.100 27.000 2.07085 0.09243 0.1735 0.000 1.07330 0.500 15.000 1.06932 0.000 25.0976 0.431.000 0.600 774.400 35.200 927.1228 01488 0.1347 0.08476 0.1542 0.313.05088 0.600 827.1093 0.0564 0.312.1252 0.000 2.0996 0.800 30.1073 0.351.1361 0.3 1044 873.300 1471 1398 1570 1485 1667 1572 1766 1660 1862 1748 I ! 23100 .000 i I I .1494 0.500 1.563.000 795.06008 0.0805 0.500 715.1422 0.600 715.351.1697 0.700 840.1228 0.9 1111 1049 1178 30.192.1381 0.700 775.07044 0.272.000 900.1238 0.000 2.191.500 715.1411 0. 666600 666.0921 ! 0.1342 0.149. i i TernlAW Condor!AW DrakeiAW MaliardiAW Cuckoo!AW CraneiAW RuddyiAW Canary!AW RaiUAW Cardinal!AW OrtolanlAW CurlewlAW BluejayiAW Finch/AW BuntinglAW - i i I 874.615.07172 0.000 795.700 i 0.1136 0. 0.1267 0.000 636.08205 28.0694 0.08312 0.4 937.1373 0.500 1.06804 0.09812 0.600 738.8 ! ! I 21.05974 0.1240 0.06242 0.3 1042 1161 981.09091 0. .400 645.0705 0. 638500 693.1729 0.000 49.200 35.1594 0.0626 0.1074 0.167.SOO 33..020 22.500 984.0794 0.07937 0.SOO .477.780.0419 0.500 31.000 636.000 25.1393 0.000 1.1054 0.06507 0.300 27.500 37.08727 0.1041 0.1214 0.1406 0.08SO 0.1079 0.1559 0. 26.000 1.1466 795.700 .1678 01646 FlamingolAW GannettiAW Crow!AW StariinglAW RedwinglAW .000 1.033.06975 0. 48900 0.000 80.100 248.800 211.5391 0.300 16.7673 0.4492 0.200 Total Aluminum Area emil .9165 0.600 242.2 602.8 250.200 182.2445 0.300 19.4013 0.000 176.7001 0.5274 0.000 86.600 i i i i de 20"C Ohms! mile 0. The values listed above differ from the corresponding ones of tables for ACSA because the COnductivity of the aluminum in the thick cladding of the core wires is taken into account Electrical properties of the aluminum wires are those of ASTM B 230 and of the core wires are those of ASTM B 502.4416 0. The single and three-layer ACSR/AW ae resistances have not been corrected for the magnetic effect of the core wire.3539 0.000 15.5804 0.600 127.1426 0.4914 0.200 202.4094 0.4847 0.0408 0.800 110.600 218.515.8419 0.8418 0.9 477.3469 ae-60 Hz I 25'C Ohms! Mile sooC Ohms! Mile 75'C Ohms! Mile 0.0 399. 4·27 .2 ! 303.900 18.5869 0.7733 0.6 ! i Rated Streng!h Ib 60.890 9.4 430.04890 0.product identification and data TABLE 4-17 (Continued) Resistance Area of Aluminum Wires emil ACSR CodeWord Joree/AW Grouse/AW Petrei/AW MinorcaiAW Leghom/AW GuinealAW DottereliAW DorkingiAW CochiniAW BrahmalAW i i 2.04243 1.970 116.4221 : Weight I 1000 ft Ib per 2693 137.6368 : 0.04564 1. 2.7048 0.3698 0. i 2. See text of Chapter 3.700 27.300 203.6932 0.600 159.9 359.7 229.5692 ! 0.000 101.549.800 13.100 1.0200 0.3880 ! i i 1.000 154.4330 0.3624 0.800 134.4417 0.160 4.4057 0.910 10.900 190.4817 0.0360 1.7524 0. 4-28 .0.198 0.0328 10.8 70.7493 ' 1468.31 67. in. I Diam.9 39.2356 336.236 0.3 .6 i 24.5 i 0. 91.1672 0.365 0.2 ! 106.2693 0. 746.0 364.0 ' 44.1327 ' 0.1181 0.3230 3290 3980 4680 5860 7420 1.0 '0.06196 i 1. Size num ' No.0629 ' 0.3893 2.398 0.3381 1.300 .5297 0.100 i I I I i 1120 1760 2160 2640 3260 3.091 1.91 29.the magnetizing currents for single-layer cables are based on 10010 of specified current for 25i>C.0 ! 821.1291 0.0 108.1486 1 0.593 0.bare aluminum WIre and coble TABLE 4-18 Compact-Round Concentric-Lay Stranded Aluminum Conductor Steel Reinforced (ACSR Compact Round) with Single Core Wire of Class B Zinc-Coated or Aluminized (AZ) Steel 13So-H19 ASTM B 401 Physical and Electrical Properties I I I I .0 230.1662 6 6 6 266.1045 .0 ' 28.7 61.6679 0.353 0.288 .0. 282.1291 2.1559 0.5 156.410 0. 18.0617 0. 6 .6 182.61 0.100 29.413 Resistance dc-20'C I Class B i Aluminized Ohms! Mile Zinc Core . Electrical data will be close enough to the equivalent size of Ilf. Steel Core AWGor Area kcmil . in.0 11.229 0.1029 0.>n·compacted conductor that data for those conductors may be used for practical purposes.0 54.8 518.0206 0.447 0. Applicable footnotes of Table 4-15 and 4-16 also apply to the above table. in.250 0.563 115.8 ' 124.039 1.4 I 1160 1810 2260 2760 3510 3450 4250 5130 8410 8060 249.182 0.3 44. for sooe. 0.1367 0.2. 70. Compact Compact Total I Alum.0657 i 0.742 0.1299 I I . . Allowance should also be made for GOre magnetization in the 3&-wire cables.609 0.1 145.0 i 78. ACSR.09530 0.646 0.8 I 0. 0. Cable. 3·13 and 3·14 and adjust according to the methOd described in the accompanymg text.15321 36 36 36 36 6 4 4 2 2 1 liO 2/0 3iO 410 6 I 0.1469 0.325 36. 0.0934 0.0 '0. 3.300 17.1060 1. in. of .3020 0.2642 477.0521 6 6 7 6 7 0. 98.3746. I I 1. 2.0521 I : 0.1217 0.4 0.8410 0..6868 954.2095 300.2 6770 7610 8540 11.140 1. 75%.814 289.461 0.290 0.0.664 0.1628 ' 0. For ampacity ratings see Figs.298 0.1 326. I Weight per 1000 ft ! Aluml· .600 30.0 .900 19.0 I 16. of Diam.0 ' 57.559 0.257 0.0 .62441 874.1039 .0 885.9 0. of Dlam.9.2.100 0.3398 0.1144 0.61 588 : 74:1 93.Sq. I 0.4 ' 39.0.. 0. Wires: Wire.517 0.1628 0.4 i 0.0 ' 966~ I 896. 49.600 605. I I 0. 0. Data shown above are subject to normal manufacturing tolerance. AZCore 11.994 1.0 64. Ib Ib Ib 0.0 61.5 447.4199 6540 7360 8260 11.0. 18 18 18 18 795. of Single • Complete Alum.0 1494.040 1. 4.2019 ! 0.1899 16.326 0.1878 i Rated Strength-Ib 36.1052 0.0328.500 19.0 1386. Non .9 46.316 0.948 0..502 0.0 315.8 197. that is.628 0. and 100% tor 7ftC.600 17.4 290.4 38.1318 : 0.0.0661 . 0815 1.l030.700 46.8011 7 0.1959 13 BobolinkiTW 11431.0961 1.2 25.9146.102 1.7 .500 32.4371 556.000 25.5' 1.0 0.3746 556.0.980 5 0. i 19xO. .08741 .1192.500 1 0.900 49.3 1 599.5 0. 19xO.0681.5 16494'45'!.1348 7 Martin.2017' 7 PlovertTW '1431.044 1.4371 0.0 975.1189' 119.2808 1286 .0 1.0 873.9848.4995 GrosbeakiTW 636.3147 1257 I 1052.5 1.0013 Grackle.8312! 8 I i 13.8534 7 0.2820.4! 23.2642 477.51 0.:~I I 1 I 0.0 175.1 746.1360' 7xO.4356 0.089 1.100 50. 7 0.1 27.8 28.1367! 0.0.2 .6 I 130.5.51502040 0. 25.600 901.2 46.0 i 1113.2788 0.700 61.01 22.Oj OA995 RookiTW 636.143 10.8117 '0.789 0.8117 0.1085' 7xO. 27 19 20 17 18 Weight per 1000 fI 1 I' .2488 ChukariTW . 7xO.900 897.6464 13 SnowbirdiTW OrtolanfTW CurlewiTW AvoceVTW BluejayiTW FlnchiTW 1 0.0.1256 13 DipperiTW .0837 7xO.4745 .5' 315. 5 0.rrw : 1351.9 i228.2913' 1075 :0.0! 1.3414 365.512.400 21.600 1499 1503 1676 2047 292 537 367 42. 4-29 .6244 954.0: 1.852 0.9990 11.0' 0.608 '0.3 19.7493 ~:.0 0.43702063 0.0.8 655.4895 1632 1522 1734 1613 1636 LapwingiTW 1590.5643 13 0. 0.12161 .3159 0. 7xO. Aluminum 1 336.152.2. 7 ' PheasanVTW 1272.204.0615 1.9191. 7xO.9991 1.0 816.7876 5 0.0 1.4 . 7xO.5 1241.51 0.9 36.iTW .ll08i 0. 13.7493 954.206.0 612. Rated strengths of the complete conductors are calculated In accordance with ASTM B 779.1192.5! 1033.1530 '0.400 34. in.0 1 0.9189 13! 0.8742 0.0949I .3 328. 0.129 1.41 0.000 523.8742 0.220 0.5.0554 13 ScissortaillTW 1272.993 1.705~113 Steel !Outside Diameter Complete' Steel Conductor Core : in. is the ratio of the steel to aluminum areas expressed as a percentage.600 lxo. 5.4 20 20 30 32 20 7xO.08SS i 7XO.0967 7xO.129 1.3747 477. 7xO.3030 1185 975.3648 . 19xO. 1780.200 448.5.2 1273.2613 1115 973.2712 1201 .256 1.9 764.12031 I.l085 19xO.9366 0. Weights are based on 1350 aluminum and Class A zinc-coated steel.1 .3987 1226 30 32 22 30 33 36 7xO. 16 0.1 745.9210 i 7xO.1253 .2 . 692.200 747.4149 1327 971.3567 .890 0.l010! 7X0.8 141.4 1275. 646.0: 0.0505 5 BitternlTW 1272.3759 1791 0.0971 7xO.900 747. 1033.0.500 22.2664' 13 30 33 38 30 35 7xO.1429 376.1121 1.445 1.8' 597. 7xO.7 33.500 1163 219 '403 174 234 29.1 I 598.8 30.203 1.4233 0. 1.100 36.191.700 10.100 7XO.01 0.908 0.061 1.5133 0.0 0.1155 19x0.8i 28.product identification and dolo TABLE 4-19 Shaped Wire Concentric-Lay Compact Aluminum Conductor Steel Reinforced (ACSRITW) Physical Properties ASTM B 779 Area Equal 10 Standard ACSR Sizes I Area Square Inches i .0 1.0934 36 42 37 64 7x0.9851 13 ' Oxbirdrrw .3255 1343 1°.358 lA08 1. 8. 6 13 16 13 16 ' SwiftiTW i 636.264 1.3351 7 1.084 10.5 0.6300. 11113.5608.100 0.1367 7xO.355.1239 1. 8 1.0 1.4310.0 714.300 1048.5083.7493 954.3255 0.0.3639 1021 IOA080 1092 0. 13 1.9 .4937 0.8678 0.0892' 7xO.2901.200 55. The type no.0871. 1.700 900.0936I 7xO.835 0.1590.0: 0.69191 10 CondoriTW DrakeiTW PhoeniXlTW RailiTW GardinaliTW 0.0940 7xO. 0.337 OA805 0. 2.400 41.9347.300 0.71 20.4071.6244 PuffiniTW 795. Rated Total Aluminum Steel i Strength Ib 'Ib I Ib Ib 0.9990 1.l049.776 0. 17.3986 Bluebirdrrw : 2156.l053.9366 1.600 1202 1274 1278 1350 1353 '430 248 456 263 483 44.9386 1.6675 7 0.560 448.980 0.0.4 39.9 '219.1372 0. 11381 0. 3.2658 10.3324.0977' 1.8742 0. 14 18 18 18 20 lxO.850 0.400 523.900 31.010 1.2 188.300 1.1236 1.900 25.l0l~1 7xO.1329' 0. Code Word Merlin/TW FlickeriTW HawkiTW ParakeeVTW Dove!TW Stranding Conductor Size ' Type I kernll 'Aluminum I Total No.0904.6244 0.13291 7xO.291 1.800 36.0' 0.0.3045 0.8117 0.01 0.0.8 '344.1383 .4805 2515 1.100 489 Data stlown are subject to normal manufacturing tolerances. 1033.2488 FalooniTW .0 '1113.7261' 16 0.4460 . 4.1329 0.4995 TerniTW 795.1351.5.2511 1032 10. AlUminum strands are of a trapezoidal shape and thus round wire sjze is not shown. 5 7 BuntingiTW i 1192.3465 0.33631 1433 39 35 39 36 37 19xO.01 0.6244 0. 0867 II 0.rrw Phoenixrrw RaillTW CardinallTW ! 795. 4.1633 0. 0.0908 0.0 I 8 .0928. 0.0869 0.0. 7 32/7 954.0 1113.4165 0.0.1147 0. 0.383 0.1373 0.5 1113. 0.405 0.0931 0.0399 0. 0.0865 0.0 PloverfTW 11431. -~--~----~------1.370 0.1461 0.394 0. Miles X.0029 per degree G for steel.111810.431 .0.2715 '0.7 954.0627 I 0.0 Dipper.0847 0.17481 0.0544.0941 0.2966 0.0859 0. Ohmsl AIJSt.O"k lAGS) at 20'G for the nominal steel area.0993.'7 42119 . ft MerlinfTW FlickeriTW HawkfTW ParakeetITW DovefTW 336..0903 0.1077' 0.1123Io.402 0.1017 0.0376.0415 0.4209 0.0.1593 i 0.0 i 8 . See Chapter 3 for details. Dir.437 0.0706 0. Layers.441 0.398 0. Aluminum i Ohms! i Ohms! Ohms!.0801 i •0.0962 .0945 0.1380 0.0 795.1710 '0.1628.0449 0..0403.0594 0..0312' 0.0668. and 129.0296.0 636.1878 0.1854.0860 0. 0.444 0.0504 0.390 0.to-Neutral Resistance ac-60 Hz dc No.0859 0. I 39/19 3517 13 • 39/19 7 i ! 13 1 1590.396 0. 1 ------". 0.1388 0.0 3 13 16 7' 10 i 2711 18/7 20/7 1717 18/7 3 [0.'TW i 1351.1860 10.1390 ! 0. 795.0806 I 0. 0.398 0.03621 0.0998 0.0. i i .727 ohm-crnil/ft (62.0 5 1272.0584 .1274 '0.427 0.0661 0.0653 0.---.0476.1416 ! 0.0349.5 1033.0747 0.0991 -.0482.0942 0. approximate values can be obtained from Figs.0749 0.0426 I 0.1056 i 0.0451 0.20:7 2.0339 0.0598 0.0752 0.1152 0.0377 0.1113! 0.0805 '0.2284 0.5 1033.1790 i 0.1717.0791 0.0979 0. Alternating current (ac) resistance is based on de resistance corrected for temperature using 0.1953. 3 Ii 2 SnowbirdlTW OnolanrrW CurlewfTW AvocetiTW BluejayfTW FinchiTW 1033.0893 0.1260 i 0.2087.0390 1 0.5 556.0845 0. 0.0369.1063 0.368 0.0971 0.0982 0. i I 1 ~-------~--~~.0914 0.0 LapwinQJ1W Falcon.4 477.0874 0.-------'-.0644 0.0945 0. No. 0.0.0896 0.0394 1 0.0389 . 1431.0991 0.rrw ChukarfTW BluebirdfTW i 5 7 13 5' 7 i 13 30/7 327 21/7 30/7 33.0 i 13 .4137 0.5 MartinfTW i 1351.1426 2 iO.1959 0.387 0.4094 00407 0. i I .1151 0.423 0.1192.0753 .376 I 0.Q709 0.0 795.Q705 3 1 0. The effective ac resistance of a layer ACSRfTW increases with current density due to core magnetization.1568 i 0.0689 0.0659 1 0.0995 0.1160 2 . and for skin effect.1073 0.0264 2 0..2277 0. 0.1111. For ampaclty ratings of TW conductors.1009 0.0 636.1160 0.---j-----i-----i---"RookiTW GrosbeakiTW TernlTW PufflnfTW CondoriTW Drake.391 0. 2 i 3.0277' 2 i 0.0883 0.5.2654 .435 0.1574.2094 0.0427' 0.0784 0. Size Type Stranding.~-- 2.0817 0. I 60 Hz Resistance at One ft Spacing GMR .07361 0.1796 0.02731 0.1904 0. Mile Mile Mile Mile Code Word ! kcmll . 0. i I' 0.0561 0.0. 0.1083 0.bare aluminum wire and cable TABLE 4-20 Shaped Wire Concentric-lay Compact Aluminum Conductors Steel Reinforced (ACSRlTW) Electrical Properties Area Equal to Stranded ACSR Sizes ~~~~'-~r-~~---r- ~--~~~-.7 39/19 i 3 3 3 0.0917 0.1266 0. 0.0928 0.1395.--\---l----j-----r--.0994 0.1605\ 0. i 1 0 0851 0:0841 0.0721 0.0984 ~:~: g:~: ~:g~: •g:: g:~~ ~:~~ \ i.0 477. 7 .0331 0.5 6 13 16 13 16 1411 18/7 1817 18/7 20:7 2.0824 I0.0363 0.0 556.0602 I . 0.1588.0906 0.4105 0.5 BobolinlvTW .0934 0.0 3 3 2 3 OxbirdfTW Bunnng:'TW GracklefTW ScissortailfTW BittemlTW 11192.1013 0.0% lAGS) at 2O'G for nominal aluminum area of the conductors.0. 5 30.0925 0.0701 3 1 3 3 3 3 3 3 3 37/19 3 3 3 84/19 4 36. 3.3258' 0. 13 '1780. 1590.0906 0.0868 I. 0.0323.1172 0.0.07451 0.0978 0.0876 0.0919 0.0891 0.0926 0.0888 0.377 • 0.0874 0.0412.0906 '0.355 1 .0257 1 2 0.0343 0.0837 1 i 0.--~--~------- Pha.0885 i .0783 0.01 7 .0607 '0.0867 0.0.0382 0.0.475 0.ct CtJrrent (de) resistance is based on 16.0794 0..383 .0815 0. 0.0606 0. 0.7 38119 I 3017 33'7 38/19 3017 35/7 1.0286 i SwiftfTW 636.0949 0.1005 0. ! i 0. 0.400 0.0545 0.0 .0538 I 0. 0.1432 2 2 .0 13 20/7 .51 5 . of 20'C 25'C 50'C i 75'C .0 7 PheasantiTW 1272.1081 0. 0.00409 as temperature coefficient of resistIVity per degree G for aluminum and 0.0200 2 0. I 1 0.0465 0.0792 0.64 ohm·cmilift (8.0866 0.392 0.1144 0.0.0917 0.403 0. 36.0503 0.0940 0.0730 0.0955 0.0 1 1113.0976 i 0.1192.0 2017 16 I 954.0356 0.0940 0.1079 0. 2156.0.. 4-30 .1370 0. 3-13 and 3-14.5 13 1272. Inductive I Capacitive Ohms! MegohmMile X.0717 0. 0.1257' 0.0632 0.0305 I 0. O 10.0 .17 ThameslTW SI.0.17 54/19 45.4 159.8 20 7x.259 10.913 0.3 1.1 0. ~or I ~re In. 3.245 30 • 7x.366 :0.977 iO.060 :0.6034 0.5 1033.3343 1047 762.4'1.927 10.3 2.0.l030 7x.9175 0.980 0. 7x.17 54/1 45. 0.rrw TruckeeiTW MackenziaITW :1272.300 35.2 537.600 556.21241 :1455.17 720.800 39.4439 686.345 1. .17 54.113S 19x.300 • 61. 2.4770 7 .2222 : 1433 6 1. 54119 42/7 45.0'0. 636.3438 .1780.17 26.165 0.200 49. num : Steel 405.0.33621 6 571.3 1.5 1431.1154 1. In.6:229.0 1590.20.4429 i 13 Pee Deel1W i1758.6 30 7x.3957 1982 1658 1324 41.l074 1.900 .092 0. 1062 1.3123 1585 il363202 '0.1520 0. 13 21 I 7x.1115 1.1392' 19x.5134 1.6.8 0.17 JamesiTW AlhabaskaiTW CumberiandiTW PowderiTW Santee. 13 SchuytkmiTW i1657. 13 i2153.3222 1693 !1478 215 46.6'1.8038.7 717 330 ! 902.6 1.6:0.1331' 0. 14 18 18 20 20 lx.0505 5 :1257. CroixiTW Miramichi.700 477.0 54.500 26.5 1033. 3920 1 7 Pecos/1W 1622.000 556.17 2217 I NechakoiTW MaumeaITW WabashiTW KettleiTW FraserlTW ' 768.40141241 ' 908 i333 22 : 7x..9674.3234 1308 1092 216 .2957 i 39 19x.1334 5 1359.860 0.2778'1260 1100.000 29.5320 2107 '1533 :574 37 i 7x.1557. 7x. 1054 1.'TW i kcmll :TypeiAlumi-.1493 1.0.424 iO.3020 0.6375 '2221 1636 1585 10.0557 7 i1233. The type no.17 4217 4517 54(7 CatawbalTW Nelsom1W Yukon.8168i 10 35 .9646 5 1158.340 33 • 7x.0 1 795.l075.4 .489 1840 1358 '434 0.1200 1.290 7x.3012 1481 :1293.6 0.9733 7 1158.455 1586 11186.8' 61.2 722.0: 42/7 45.4490 0.600 795.4187.196 0.600 39.17 54i19 84/19 84/19 11730.1241 1.2268 i 8 19x.334 '0.0910 1.5310 3048 :2477 :571 59.6072: 16 ~:.203 30 35 .4479.400 i 51.17 4217 45.5 1351.6 0.9 768.5 1192.7049.5992 0.7'0.0978 1. 1.9669'1.3462 1142 i ColumbialTW Suwannee!1W CheyenneiTW Geneseel1W Hudsol1l1W • 966.1111 1 7x.9991 1.200 .5 1272.'TW MerrimacklTW Plattel1W 11334.4 0. 13 7x.0.3345 1417 1185.7x.l004 1.500 46.382 :0.7518 0.000 28.2 894 248 .0 12156.'TW 34 42 42 54 54 .762 1.155 0.6912 1.6039 0.0 0.504 1.1113.108 0.17 54/19 4217 .700 30.2043 1.5 1113.0 24.9098 1.6 1.1520 !0.3600 1540 1372 i2 68 0.067911.0 954.292 33 7x.0926 1.2 0.1609. num Steel Strength Ibs 'Jbs Ibs Ibs kcmil Stranding I 441.0 795.213 38 :19x.9'0.0967 1.1319 1.078 .1430. 13 5 7 13 5 Potomacl1W .1467i 1.! plete CondUC-i Steel I AJumi-! CodeWord MonongahelaITW MohawkilW CalumetifW MyslicffW Oswego.1418 7 7x.' 265.6377: 7 11926.8'0.4 20.2232 1.0 11192.7 0.3090 '0. S.7 625.700 38.0.622~1 3 27 : 1x.470 1.2919 1079 957.4720 1713 !~261.200 42. Rated Total.0 1113.8573 13 ' 959. Weights are based on 1350 aluminum and Class A zjnc~coated steel.1520 781.8 1.000 57.658 0.7589 0.1 p.063 2.1.2323.900 ' 65.0 .7 626.0 • 795.900 31.5 26.8290 1 8 '2627.0 22.600 .4805 2498 .3079 7 Rio Grande.5665 2471 1821 1650 . is the ratio of the steel to aluminum areas expressed as a percentage.0 i1590.400 34.0944 1.product identification and data TABLE 4-21 Shaped Wire Concentric-Lay COmpact Aluminum Conductors Steel Reinforced (ACSRITW) ASTM B 779 Physical Properties Sized to Have Diameters Equal to Standard ACSR COnductors Conductor Size Area Square Inches ! Outside Diameter Stranding Com.l041 1.1159 1.4 379.545 1..4176 2199 1838 i361 :0.0. 4.3.5221 .0 11351.200 44.3 0.200 336. Aluminum strands are of a trapezoidaJ shape and thus round wire Size is not shown.5312 1.2677: 11589.400 27. 1078 1.077 . 4-31 .846 0.1244 . 7 : 32 946.rrw 11533.8 856.990 !0.1318 903 415 7x.7 61.5236 684.1 i191.7x.302 36 39 i19x.348 1.0 734.7 1.0 954.0 45.400 36. 913.0' 1 636.3840 1868 11 563 :305 36 39 19x.0 1. 16.900 33.5060 1968 1449 !519 7x.10.4401 1489 1089 400 ' 26 34.1.5074 13 565.427 0.6!451.700 i1272.1338 1.1195i 0.6986 16 20 7x. 31.3181 0.5 1.000 37.31 197.9 1. 477. i1467.1.6819.0.21 0 .0 ! 636.0 .5 1192.0' 954.900 il033. 7x.1431. 1.7436 0.3810 il.6 0.125 :1.!~i .1.3 0.8762 16 1186.0925 13 1372.8 1.6314113 .0961 19x.5 0.602 1.7537 0.1520i 7x. Rated strengths of ti1e complete conductors are calculated in accordance with ASTM B 779.~ .100 1 74.359 1.8 176.2739 1. No.3723 1755 1468 <:87 36 39 19x.9095 0.3732 Weight per 1000 ft I Size & Stranding at ACSR with equal diameter : !Alumi.1147 .3330 10.0281. 33 7x.3477:1630 1280 250.1529 1. .0 1272.1. Data shown are subjec1 to normal manufaC1uring tolerances.0 3611 24/7 2617 45.2901 1372 !1198 174 0.0973 1.l012 1.7 714.5 18/1 2417 2617 2417 26.1280 1.1949.4 1. num : Total.3571.3585 987.4 523.5 '419.0 54/19 45.4i288.2030 :468 10.500 .7i231.248 36 ' 7x.900 53. 390 0.0764 0.0690 0.376 3 0. 0. 0.0617 0.1168.363 CumberlandlTW 1926.1166: 0.0948..3. 0.0951: 0. of I 2O·C ' 25'C ' SO'C '75'C GMR 1 Type Stranding Aluminum' Ohms! OhmEl/ Ohms!' Ohmsl I No.0913 0. For ampacity .358 PowderfTW 2153..0666 YukonlTW '1233.0698 0.0.390 0.0612 0.6 7 42/7 3 0.0903 0.1214' 0. ' .L_94_6_.2.1045.0877 1 1372.0500 0.092210.1364 i 0.0595 0.0730 • 0.'TW 1730.0716' 0.142810.1451 ! 0.0723 I 0.0.0988 0.1329 0.0350 00407 0.0963 0.0839 0.0713' 0.0330 0.0734 0.8 6 13 16 13 16 14/1 18/7 .2258' 0..0858 i i PotomaclTW Rio GrandelTW SchuylkilL'TW PecosfTW Pee DeefTW 36!7 39/19 36r7 . See Chapter 3 for details.1923 0.0573 0.0420: 0. 0.0617 0.0_3_58+'_0. 0.365 Athabaska.09491°.6 OswegolTW I 664.0473.7.64 ohm-cmiV~ (8.0.0420' 0.05821 0. i MonongahelafTW.1748.388 0..0.0810.372 0.421 i .8 33!7 i 0..lTW i' 957.0616 0.04001 0._8---'_64~ /1_9---''--_4_.0.0639.0554 I i 0.0.0877 TruckeelTW MackenzielTW 1359.0% lACS) at 20'C for the nominal steel area.0538 0.09181°.0949 WabashlTW 762.4 13 1 21!7 22!7 3O!7 33/7 25/7 .0364 0.ee C for aluminum and 0. 2O!7 20!7 20/7 2.0.0541 : 0.0_5_94.1189 0.0029 per degree C lor steel.2205' 2 10.0304 0.0775 1.6 13 39/19 3 I' 0.0. 5 1158.397 0395 0.00409 as temperature coefficient of resistivity per deg.0654 0. 0.-10_.91' 3 27/1 3.05061 0.0464 i 0.0976. CroixlTW i 1467.402 0.• 0.6 13 39/19 3 '0.0895 0.0494 0.079410.atings 01 TW conductors.0891 I 0.416 .0218 0.0585.0690 0.0630 0. ! Miles X.370 James.0845 0.. 405. and lor skin effect. 0.0584' 0.1367' 0..1071 0.0341 .0968 0.0459.0. 00653 0. apprOximate values can be obtained from Figs.0549 i 0.0782 0.1564 2.6 13 38/19 3 ' 0.1155' 0.0889 CatawbafTW ! 127201 5 3O!7 ' 3 ' 00706 i 00747 I 00817 i 00888 003941 0392 00689 NelsoflllW • 1257. 0.0655.0815 0._0_.0654: 0.1638 0.0897 0.0445 0.0288 0.0718 I 0.10421'0.0622.01 7 1158.9..388 0.0 5 0.0886' 0.0647 0. Alternating current (ac) resistance Is based on de reSistance corrected for temperature using 0.270~ I 0.0658 0.343~ 1 • 1 .1309 0.l-0_. 7 36/7 3 0.391 0.6.0776 0.0603 .l_17_3-j'_0_.04381 0.0501 • 0.382 0.0929 0._404_+_o.0523 0.0826 0..0.0466' 0.0866 5 at. 0.0964 NechakolTW 768.0. 0.727 ohm-cmillft (62.0395 • 0.379 3 0.433 0.0431 3 0.bare aluminum wire and cable TABLE 4-22 Shaped Wire Concentric-Lay Compact Aluminum Conductors Steel Reinforced (ACSRITW) Electrical Properties Sized to Have Diameters Equal to Standard ACSR Conductors I I i' Code Word Size I kcmil I Phase-to-Neutral ReElISlance i 60 Hz Resistance at One It Spacing ac-«I Hz dc No.1331 2 10.2483. 13 42/19 3.J. 2.0925 FraserlTW _ _ _.0.0591 .0780 0.0325 0.8' 16 20!7 2 0.399 0.1763' 0. 1758.0516 0.0991 0.1138 i 0.1171.0% lACS) at 20'C for nominal aluminum area of the conductors.0874 ----+---+-~----~----~--~--~---r--~--~----~ ThameslTW 11334.1500 0.0.0281 0.464 0.0378.0300 0.0720' 0.0970 0.0758 i 0.374 0.2 13 20F1 I 2 ! 0.0822 0.0.7.1590.0658.0._09_1_9__ ColumbiaITW Suwanee. Layers Mile Mile..0.0400 1 0.0637 0.0637 0.385 0.0676 0.lTW CheyennellW GeneseelTW HudsonlTW 1966.0867 MerrimaclTW 1433. 0.0618 0. AlJS!.0658 0.081310.0481. 2 2 3 3 2 10._0_94_5. The effective ac resistance of 3 layer ACSRt1W increases with current densIty due to core magnetizatiOn.0424! 0.0901 0.0770 0.!_1_0+_3_5!7_-1_ _3_-L_0.7 .0867 MlramichillW 1455.0.0460 0.378 0.425 ! 0. 16 . 3-13 and 3-14.1424..368 0..640 3 0.0946 Kettle.355 _Sa_nt_ee_lTW _ _--'_26_27_~. 4·32 . Inductive' Capacitive Ohmsl i Megohm Mile X. Mile Mile: It . 0.0.0697 0.1097 0.07531 0.1550' 2 10.6 13 39119 0.0409 I 0.0938 0.0674' 0.1332: 0. 0. 3.0510 0.098_2_'l-l'0_. Direct current (de) resistance is based on 16.0653 0.0450 0.0550 0.0917 0.05461 0.0871: 0.J.0761 0.1635..0575.0965 MaumeelTW i 768.0888' 0.0503.0310 0.0803 0.0703: 0.0373 0.04271 0.8 ' 8 64/19 4 : 0.1306'0.0543.1' 7 35!7 3.0414 i' 0.1159 0.3 MystlclTW 666.1191 0. ! 0. and 129.413 1 0.0673.5: 5 3O!7 3 0.0.0439 0.2113 1 959.565. .1: MohawkfTW I 571. 0.424 0.0459 I 0. 0.0731 0. 7 3217 3 i' 0. 0.1907 0.0764 0.0637 0.0924! 0.0462.0364 0.3 36/7 7 0.0856 33/7 PlattelTW 1569.430 0.1603! 0.6 39/19 3717 3 3 3 3 3 . 4.1.0804 0.'TW 1949.077410.1503 0.0553. CalumetiTW .0769.1136 0._10_7_7J--0_.0829 0. l05~ I 4xO.0 10500 : 0.3' 9350 I 0.0: 98.1855 .484 0.0 239.3 ' 156.1686 11700 '0.7' 0.1219: 0. 1219 I 0.1.512 : 0.6 230.368 0.1357.0.726 41.0 296. 172. i 266.1228: 4xO.757 0.9' 222.5.4 88.5 237. 333.2 89.1 233.1927 0. 4xO.0 228.1162 4xO.302 : 0. 0.697 10.1877 0.2091 10.3.3784 I 0.4591 i 0.629 7xO.4 I 468.22 1.6: 327.591 4790 0.813 0.422 ! 0.190 0.11621 500 '0.402 234.2352 i 0.0 71.439 .0521 4xO. 4xO.811 83.0 45. 304.1147: 12xO. ac-60Hz dC 20'C 11.1162I 500 .458 6200 '0.9 281. I 4XO.52 : 0.7 i 327.40 1 1.3924 3OxO.1747 14400 0.3924 24xO.12571 4xO.255 ! 0.24 ' 2.7301 3. 3xO.0.556 0.11 .522 0.135~ I 0.770 0.814 !0.0240 0.1791 0.701 0. 0.1882 0. 84.180 0.2748 15xO.1162' 19xO.235 10000 i 0. 0.0 i 132.316 0.1939 2SO 2SO 300 300 0.6254 4100 ! 0.1923 0.7: 2.679 4xO.228 10800 10.813 .0.3208 : 0.3926 12xO. 0.1147.563 15xO.3 26.S07 5180 10.1357! 350 i 0.1539! 0.1701.230 11900 .1 1 35.0.0 : 85.1379! 3xO.813 0. I:.184 0.0 0.1963 .1539: 7xO.1 3xQ.14901 3xO.328 8410 : 0.1228 3xO.1451 450 450 500 500 i I i .1162I 7xO. 1350·H19 with 6201-T81 Reinforcement ASTM B 524 Sizes Physical and Electrical Properties Size AWG or Cross Section : Square kcmil .853 0.1147: 4xO.60 2.1147 7xO.7884 1°.7 145. 4xO.03 :1.328 0.0 550 550 5SO 550 550 550 0.884 62.1701 4XO.l052 3XO.240 468.1708 12900 0.241 10.1162: 500 0.16221 0.602 0.4966.3 Rated 25"C 5lrC ' 75" Strength Ohms! Ohms! Ohms! 1Ohmsi Mile Mile Ibs Mile Mile 826 13.209 .8 183.215 i 0.0382 0.0 78.5.1822I 7xO.464 30.1219! 0.2: 98.218 (See footnotes at end of table) 4·33 .284 ! 0.261 0.395 : 0.954 10.11621 0.1162.207 0.0 ' 68. 1622 .82 12.811 0.0 374.191 i 0.0 370.629 155. 56.1327 : 4xO.0772 4xO.939 '1.178 1120 : 2.15391 .0661 4xO.0 : i 1 359.197 0.0 137.51: 26.0 296.7: 19.1963 0.220 : 0.9 0.2358 350 0.2! 16.193 0.2..1739' 3xO.0 5480 I 0.0328 0.1 10400 .194 10.4 : 515.1045 4xO.726 7xO.: Alumi 1350-H19 : 6201-T81! in.390 0.14901 4xO.258 0.1739 4xO.4320. 3xO.287 9520 0.230 0.174 0.1379 i 0.0.382 7390 0.1257.5794 : 0.321 I' 0.1257i 12xO.211 0.2669 10.0 421.282 • 0.37 i 2.5 110 123.1357! 0.447 0.212 468.2 197 .2358 0.193 ! 0.853 407 325 460 418 334 251 I· i 0.1317 195. 10.1 468.2408 : 0.0: 78.398 0.0974: 3XO.0.9207 .176 '0.879 i 0.1451 I 0.180 . 400 0.0868 0.6 39.49 31. 0.214 0.1.3 i 155.54 2.851 0.359.4318 .574 0.308 .270 .6 62.17011 .7' 207.853 0.1752 10800 : 0.3935: 0. num : 6201 Alumi-I' num Total ! 3.574 0.3924 33xO.7 49.03 .product identification and data TABLE 4-23 ACAR Aluminum Alloy Conductors.330 1290 .0 i 58.1! 148.0661.1219.3 53.61 98.0829 0.28 i 1.216 0.0.4320 118xO.293 I' 88.0608 0.0974! 0.1219: 28.63 1°.250 0.0 467.1219 .1537 I 4/0 0.1663 246.234 13200 0. 7xO.1971 0.3: 210 0.1327 3xO.210 0.394 • 0.4318 15xO.851 0. 7xO.1 i 185.410.1257! 0.351 ! 0.1451! 0.1219 19xO.334 8430 0.5 2010 2690 3140 3310 11. 115.8 i 105.431 '0.0 380.2.221 0.0 120.1 67.42 .232 0.2 124.202 0.0. 4xO. 12xQ. 0.679 : 0.1672.7 3830 10.6 4 48.469 6040 0.0 : 103.275 .15391 4xO.3534 12xO.2753 : 0.176 0.213 0.1711 13000 0.3142 15xO.4 515 97 180 514 263 514 ! 3.477 1 I 7470 I 0.0 515 108 514 189 55.198 .414 .4: 22. 24xQ.1221 310 0.996 1750 1.0 I 49.201 0.744 0.4320 130xO.1.198 0. Inches Resistance Stranding Weight per 1000 Feet' • Outside '1350 i Diameter .3924 18xO.3926 15xO.0 468.239 11400 0.5 42.1878 0.216 50.468 6S00 I' 0.2140 0.0834 i 3xO.770 0.853 0. 15XO.646' 0.209 0.601 0. 7xO.247 0.554 i 0.0 1 : 418.813 0.235 421.3142 12xO.5 66.0 113.804 0.84 .3853 '0.3134 i 0.0.1548 I 4xO.0 72.292 16.0.9 280.1672.0.1548I 3xO.91' 178.0 11800 10.0772.2748 12xO.1878 3xO.4320 : 33xO.3534 15xO.1219 13xQ.197 0.198 0.0B34 . 0.6 12. 0.16Z: I 4xO.5 77.0 .' 374.13xO.1701.0 SOO ! 0.192 0.1.1 184.0.639 • 0.77 0.1451I' 400 0. 156 10. 0.116 0.114 10.116 I 936 21100 10.1560 I 0.1470 .0... 1.5892 ! 33XO..0.000 1.125 0.1560 i 1. 359 703 702 702 701 : 14400 .128 10.~ : 0..112 !0.003 i 585 : 532 : 425 I 319 750 750 750 750 I 0.6280 0.029 1.1777 4XO. 627 800 800 500 800 I: 0.1602 0.092 1.109 !0..1424 1 0. ac-60Hz de Diameter I' Alumi.4709 600 ! 0.155 0.1470: 130XO.101 0..7849 54XO.118 0.7849 48XO.1602 7XO.1424 : i 0..1568 1.141 10.130 : 17100 : 0.175 12800 i 0. I : I.1560 .151 1.7072 I24XO.1_1_2-.185 I' g:..-i0_.092 1.151 836 760 608 ! 456 101 176 328 479 937 936 936 935 18900 0.1280 28.1260: 0.000 1.116 0.0.1375 7xO.148 10.5494 • 0.122 10.1644 13XO.1777: i 12XO.184 66 115 1 213 : 311 609 609 608 607 I 71 123 656 655 .1642 0.0.168 : 0.1273 . 0. .1273 18xO. 0.153 10.7072 I 18xO.1602.1093 : 0. 19XO.132 22400 : 0.192 0. in.5102 i 0.159 0.167 0.113 0.112 .09417 0.1602 13XO.029 1.118 ! 0.5494 '33XO.997 0.: Stranding Weight per 1000 Feet I' : Outside . Inches 1350-H19 i 6201-181 i AWG num 0.09877 21400 0.1375 13xO.108 0.003 0.963 0.891 0.1067 10.169 .5892 ' 24xO.09_7_69-.1103 iO.1273 24XO.1777 .1424 13XO.117 0.1273 4XO.171 0.110 : 0.1644 4xO.121 794 1..7849: 42XO.1090 .142 0..1280 0.148 10. 0..09269 20400 0.5102 '0.121 1.l09 0.124 : 0.103 0.1250 0.061 1 711 646 I 517 I ! 388 900 900 900 900 0.121.1420.1777 7XO.7849: 33xO.997 .13XO.1273..117 22900.1312 0.107 :0.. 365 850 850 850 850 0.145 .1516· 13XO.1_2_1_ .192 0.128 18400 0.0. 0.0.1470· 7xO.1280 7xO.121 1.137 iO.154 10.133 19000 0.928 0.196 0.152 829 737 845 ! 507 i 107 199 290 428 (See footnotes at end of table) 4-34 0.163 : 0.152 1.1470..1516 . ' 1 1 ! 654 .119 10.1375 i 19x0.7853: 3OXO.5494 Ii 3OXO.000 1.125 .1605 '0.099110.09555 0. 4xO.1470 I 4XO.108 0.123 0..1_0_3-.128 .l44 10. .121 10.104 0.119 0.16441 0.1 132 : 246 .1325 30xO.114 .119 935 1 935 .131 0.0.09761 19400 0.6280 24XO.1424.092 1.1644: 1.928 0.1260 13xO.7458: 24xO.149 :0....165 0.7853 i 18.6280 i 18xO.09379 22600 0.101 0.0.000 1.~ i~:.1325 24xO. 0.1602 0.118 0.I.1516 0..139 1 I I.1407 0.936 19700 !0.1375 0.1325I 4XO.177 I 14100 0.1546 0..7456 :30XO.142 407 796 796 795 411 91 159 295 431 644 ' 643 842 842 17000 10.134 1.136 .5494 18xO.1470 I 13xO.1373 10.1159 10.0.1602 0.110 0. 889 17900 0.000 1..181 11800 0..061 1..1479 0.7072! 33xO.162 0.1516i i 18XO.1560 4XO.-0_.161 0.061 1.181 15500 0.190 0...1273 3OxO.5892 18xO.1325 10.1424.151614xO.bare aluminum wire and cable TABLE 4-23 (Continued) .115 !0.166 0.152 1.160 81 141 262 ! 363 749 749 748 748 I 15300 10.1644 0.128 1 :0.963 0.1325: 7XO.136 10.106 0.7458! 18xO.1644I 0. Size I· Cross.125 : 20300 ..1427 '0.1280 I 1.5102 I 0.. 1350 i Section: or : Square kcmi! .09283iO.135 10.1202 0.0977 0.6679 : 33XO.1042 iO. 19XO.1273119xO.0.1375 4xO..r . .691 444 650 650 650 650 i 0.889 0.1644 19xO.-0_.146 I· 86' 797 16000 17400 19200 21400 10.029 .200 12800 0.891 0.1560.1470 1 i 1.128 15500 10..092 950 950 950 950 0.1012 23900 :0. 15300 0.1564 0.1560: : 0.0.157 '0.1602 19xO.139 10.172 ! I '0.122 18200 i 0.000 6201 ' Rated 20'C Strength Ohms! Ibs .1156 ' iO.000 1.5892 '30XO. 329 i 335 654 13600 :1 14700 16100 i 17900 76 .1424 4xO.129 20300 :0.6679 : 0.1325 700 700 700 700 : 0..691 0.029 1.r .6679 .1444 0.0.1231 0.0.1325: 19XO.7458! 33.1516 i 19XO.1375 24xO..122 0.1424 7xO..162 : 0..1560 .889 0..151 1.1280 I 0. · 0.151 1.r . 7xO. 433 96 167 311 455 : 890 ..165 : 0..1424 I 0.160 0.1644 7XO.112 0.148 0.1516: I 24XO.0. 33xO..4709 600 .1516 i I30XO.6679 0..108 Ii 0.121 165000.1037 0.1470: 19xo.1602 .-.103 0.7663: 24xO.1375 i : 0.0..132 '0.4712 600 i 0.4709 600 . 722 : 577 .145 10. 13xO.097810.11730.1560 7XO.4709 I Resistance 1 ! 753 !1 684 547 i 150 279 ! 889 888 I: I i 0.126 10..151 10.0.152 1.1325 18xO..1602..7072.000 1.4712 500 I 0. 494 395 296 1 ! 570 i 456 342 I I 668 608 486 i 25'C 75' 5O'C Ohms! Ohms! Ohms! Mile Mile Mile num Total 118 206 60 106 196 287 562 561 561 562 561 560 12500 0.09645 0.-1i_2_75_00_L!'0_.176 : 13800 '0.997 0. 7xO.163 0.1341 : 0.177 .09606 25200 : 0. 600 I 0.177 14100 0.1375 I 0.0988 0.7853 133x0.1516! 1.928 .196 0.1235 .061 1.107 0.928 0. 30xO.1280 0.1280 19xO.6280 133X0.134 10 .i Alumi. Mile 355 501 456 365 273 ! 543 .1130 10.121 1.5102 115xO.153 iO.1325.1029 .181 ! 17100 0. 0.1273113XO. 0. : 33xO. 0.997 0. 0.1403 1.261 1.287 1.0852 0.07509 0.07816 0.1029 ! 1029 0.1343I 1.0607 .0781 0.0976 i 25600 'I' 622 . 0.07577 0.0793 0.0906 ' 0.300 i 1.0.300 1.107 10.250 1. 22500 .1838 7xO.0796 25700 '0.1724 1 .07838 26700 • 0.100 1.100 ac-60Hz dc i Ohmsl Mile 25~ 5O'C 75" Ohms! Ohmsl Ohm$! Mile Mile Mile 20700 '0.100 1.06974 0. 363 I 535 1170 1169 1169 1168 1.0205 .9426 24xO.1403 13xO.0996 1.07535' 0.0921 0.0.263 1.0878 0.0912 29300 0.200 1.18.1724 i 7><0.200 1.0.287 1045 950 760 570 126 220 410 598 .08204' 0.0924 0.1343 .0212! 48xO.1838 1.0939 0.0888 0.0996 1.07344 0.1217 1217 1216 1215 24500 .0.300 1.100 26600 i 0. 0.209 1.0899 0.0947 1079 959 839 659 I 139 258 378 557 11218 .09429' 0.07238 0.1431 113xO.09679.07503 I 0.0949 0.09433 [ 0. 1838 I 0.8637 0.200 1.250 1.0834 '0.06722 0.300 '1.0946 28900 '0.250 1.0791 0.0788 0.13431 0.250 1.0861 0.0821 31500 • 0.0863 0.1838 13xO.287 1.0212.0872 0.1403 48xO.364 0.0856 31200 0. 0.18741 7xO.107 0.07877 0.06827 0.0834 0.100 30200 0.product identification and data TABLE 4·23 (Continued) SiZe Stranding Cross Section Square Inches 13S0·H19 AWG or kcmil Resistance I Weight per 1000 Feel 1350 I 6201 ! 33><0.086741 0. num I Total 1.08131 '0.1460 28.1838 4><0.1403 19xO.364 1.0.1724.0911 I 0.0975.312 1.1724 I 13xO.207 1.9430 0.0976 22900 I 0.1724.0867 0.187~! 4xO.9430 '0.0982 27100 0.0974 0.0982 1 24100 10.0986 [' 24800 .08554 I 0.1431 0.0985' 24800 i 0.0945 0.100 1.267 1.0.1874 1.9426 3OxO.0.1874.0948 0. 23100 i 0.1403 33><O.109 0.263 1.8641 42><0.312 1.209 1. 19><0.1874 1.0854 0.8641 '33.0878.0899 0.0864 0.1801 0. : 24><0.9810 142><0.07393 0.0892 0.0847 0.1217 . 13.8637 1. 1124 54.108 0.111 10.0918.0719 0.1431 1 7xO.0795 i 0.0937! 0.1431 0.8637 0. 0.0964 0.0836 0. 54xO.0.07815.1343! 28xO.209 1.1515 28.1515 33xO.0908 0.250 1.106 0.0874 0.1515 7xO.1801 119. 13xO.1460 .1403 ' 42x0.250 1.0866 0.9817 3OxQ.300 1.364 1.1480 1.0752 0.0. num .0.314 1.1431 '28xO.1431 i 19xO.180114XO.18xO.I.0844 0.200 1.314 1.0986 0.1801 0.0205 3OxO.1403 7><0.106 .0.0.0.0938 0.1801 1.07727 24700 I 0.209 913 811 710 558 118 219 319 471 [1031 '1030 .1343' 0.1515 42xO.0996 54xO.288 1.30><0.100 1.400 0.300 1 1.089531 0.0904 0.314 1.07645 I 0.288 1036 921 806 633 134 248 .250 1.0878 ~~ I ~ 0.1874 1.102 .0.200 1.102 I.9817 1&0.261 1.0737 0.200 1.8637 0.1801 113><O.0904 26600 0.Q7685 0.400 1.101 23600 . .1431 1.0996 0.0804 0.9430 I 0.1515 48xO. 547 '1030 .9426 33XO.o.0810 0.0948 0.1838 0.0996 1.207 1.1403128xO.0.0817 30000 .100 1.0.0871 0. 1217 1216 25100 I 0.0804 28200 .263 1.0776 0.100 1.250 1.9810 48xO.0924 0.8641 54xO.110 22600 '0.0768 I 0.0205 33XO.07133 0.08528 I 0.0905 0.1.400 1.07427 ! 0.06821 i 0.207 1.0839 0.0894 0.0778 0.1515 13.9430 I 11.0. 4><0.207 1.200 1.286 1.103 21600 I 0.1801 0.0904 0. 27800 0.9810 54xO.0836 26800 10.8641 48xO.1515 19.1801 7xO.261 1003 912 730 547 : 121 ' 212 393 ! 575 .08004! 0.1171 i 1170 11170 .1460 I 1.0. 1030 [ 1029 I 1028 0.364 1.1480.0728 0.101 27700 '0.07953 28800 10.9426 18xO.9817 33xQ.312 1086 131 593 1.1168 0.17241 919 836 669 501 111 194 360 .314 1.1838 19xO.1874 1.9817 24.0937 0.0815 (See footnotes at end Qf table) 4·35 .9810 • 33xO.0.100 1.1460 1.0826 .200 1.261 1.0826 0.087351 0.1724 19xO.1343 i 0.0836 0.0205 24xO.0926 0.300 1.0844 0.0895 .0940 1162 1033 904 710 150 278 407 599 1312 1311 1311 1309 26500 28400 30800 33300 0.07135 0.1874! 19.1724 i .0929 32700 0.07415.400 1. 1343' 13><0.07218 0.0973 24500 10.263 996 886 775 609 ! 128 I 239 349 i 514 i 1124 11125 11124 i 1123 0.288 1.0788 0.300 1.0.0212 133x0.1838 0.1515 i ! 1124 1123 1122 20'C Rated Strength Ibs 'Outside Diameter Alum.1480 I 7xO.07723. 0.0.312 1.0914 0.0960 0.13431 7xO.1480 19.0212 142x0.0800 0.0910 0.·: Alum!· ' 6201·T81 in.1431 0. 1778 ' 1777 36000 0.0626! 0.823 54.700 1.0611 i 0.1494 1326 1162 913 193 356 523 .0580 50600 0. 157~ 1 1.13xO.0639 1.1.700 1.1482. AWG 'Section Outside 1350 or . 0.500 2.0756 ' 0.0656 ! 0. 298 : I:: ! 171 318 1 465 685 ' 1405 .962 72xO.04286 0.0.900 i 1.630 1.600 1. .0522 53700 . 0.04775 ' 0.04350 ! 0.0553 0.1811.3345 33xO. 0.0.0622 80 1.0494 0.0685 0.1765 1.05153 '0.800 11.1694 42x0.06367.589 . 1657 : 1.0647 0.1779 54xO. 7x0.0536 I .1811 42x0.1620 28xO.1765' 13xO.375 1.0505 ! 0.0616 0.1718 : 7xO.630 1.525 1.458 1. 0.1694 48xO.5713 1.54xO.375 1. 0. . 0.0494 .5713 1. 0.2573 54xO.1620 1.1620 1.525 1.0.0685 .900 : 1.750 I 1.502 1. num • Total in.589 1.l568 ' 7x0.05578 .0604 ' 0.1765 33.057310.05304 ! 0.250 2.623 63xO. 0.0681 39600 .1657 i 1.630 I 1476 1291 214 398 581 856 1874 1074 1872 .0623 0.0643 0. num 1.1779 42xO.0577 0.5713 1.l620 ' 7x0. 176~ 119xO.0593 35500 ' 0.0752 0.000 2.03857 0.0544 0.766 72xO.4140 42x0. 0.0725 0. 1.0581 46300 • 0.0531 ' 0.37xO.0586 0.0710 38100 0.05746 i 0.1811! 7xO. 0.500 .1404 ! 1404 : 1402 11499 1499 ! 1498 ! 1497 ao-6OHz de :!SoC 75° Rated 20°C 50°C Strength Ohms! Ohmsl Ohms! 1Ohms! Ibs Mile Mile Mile Mile 0.589 1.1568 19xO.1482 ~ 28xO.04853 41800 0.bare aluminum wire and cable TABLE 4-23 (Continued) Resistance Stranding Size .1811 1.766 1.0737 0.1482 i 19xO.BOO 1.0793 : 0.04561 0.502 1410 1253 1097 862 182 338 ' 494 1 727 ! 1592 .630 1.0722 32200 .0593 .05795 ! 0.700 1.525 1.0612.589 1.l568 13xO. 1657 .1297 i 1112 389 573 758 1871 1870 1870 1.1811 : 13xO.0605 ' 0.4140 46xO. I 19xO. 1.0596 ! 0.04637 40600 0.0554 .750 1.0532 .05025 45300 : 0.0766 i 0. 0.3346 54xO.0691 0.0.0674 36500 0.1620 19xO.1568 ' i 1.630 ! 1482 .750 1.0640 ' 0.04704 44000 0.500 11.1640 i 1474 ' 1263 442 652 861 2126 2126 2124 1.0629 I 0.0666 37400 0. 0.0668 0.06099 10.0633.05620 .600 i 1.4924 1.0615 0.04646 .1779 .1716 1. 45500 .0.0542 0.1 0.0693 32500 0.0689 42900 . 0.729 1.630 1. 0.411 1..1765 i 7xO.2573 42xO.823 11871 '1637 i 1403 491 724 957 .BOO 1.000 2. . 0.502 1.729 63xO.0677 0. 0.0668 1. 0.500 1.250 2.630 1.0560 ! 0.4140 33xO.04880 ! 0.2573 33xO.411 1244 1106 968 760 1.1669 ! 1.0707 1.06186 : 0.0634 0. 1694' 7xO.0538 0.05981 0. 1572 ' 1.1568 1.0717 0.458 1328 1181 1033 B12 161 .0777 ! 28400 30400 33000 1 35700 ! i I 0.1594 33xO.0743 0.05227 .411 1.0629 .0706 .0544 : 0.1. 1482' '63xO.0550 0.0586.0622 ! 0.3345 42xO.1694 28xO. 203 ! .766 1. 0.0527 57700 0.750 1.570 72x0.0.900 1 1.1620! 1.000 2.0593 .1765 42x0.4924 1.0499. 1684 34100 10.0649.0709 0. 0.0824 30400 ' 0.1577 ' 1402 1226 964 378 552 813 17BO 17BO .0461 .05879 : 0.1765 48xO.4140 54xO. 0.1716.04773 47600 .000 2.03801 0.1718 1. Square ! Diameter Aluml.546 1. 1668 13xO.1811 33xO.0701 35200 0.171B 28xO. (See footnotes at end of lable) 4-36 888 ! ! ! ! .1811 128xO.1811 48xO. 1591 1591 1589 1.1657 .4924 1.1568 28xO.1657.0489 ' 0.2362 2361 2360 2.0717 41000 i 0.l9x0.0764 ' 0.0470610.05 43400 : 0.1572I 37xO. 0.1568 1.000 2.06275 • 0.0608 . 28xO.05377 ! 0.0700 1.1669 1. 1660 1014 ! i .l669 28x0.0579 0. 1637 33200 • 0.05455 . 0.1669 1.Alumi-! kcmil ! Inches. 135D-H19 6201-T81 . Weight per 1000 Feet I Cross I 6201 .0650 0.0574 0.458 1.0802 . 0.0655 0.600 ' 1.171~ 1 19xO.05539 ! 0.0658 34500 0.525 ' 1452 1291 1130 187 347 506 ! 749 1639 1638 1638 . 1870 37900 0.0622 0.500 2. 0.1568 .0499 0.500 1.1620 13xO.05423 .0.04882 38600 0.411 1.1669 .000 2.546 1. 0.1657 ' 37xO.0586 46600 .0688 ! 0.729 54xO.05965 0.0466 ' 0.1669 19x0.0657 ! 0.0635 0.06510 0.0748 ! 0.570 1.1694 19x0.1718 1.0567 : 0.0607 41700 0.1572 ' 19xO.0735 0.1572 . 28.0568 0.546 1.05138 ! 0.05300 .375 i i ! .0538 ! 0.1.900 .0652 ! 0.03915 0.0560 .502 1.0619 1.4924 '54xO.000 2.05460 ! 0.1620 1.375 54xO. 51900 : 0.458 1.546 .1716 1.5713 .500 .600 11.2573 48xO.700 1.771 1687 1686 ! 1685 . 0.1765 28xO.0600 38500 0.1779 48xO.0642 ' 0.0641 ! 0.0.1669 1.1482 1.04224 0.1694'l3x0.1.3345 48xO.962 11.0668 ' 0. 33xO.0694 0.962 1.0673 40500 0.570 1. 1572 .600 .1482 54xO.1694 1.250 2. 0408 I 0.946 ohm--cmil/ft.0431 0.750 I Stranding 1 55600 i 0.1816 12247 ' 1966 i 1686 590 869 1150 1 2837 2835 2836 19xO.0453 64500 .159 2. 5. for 1350~H19 wires and 19.1738 19xO.912 • 63.03259 : 0.159 2. etc.03165 0.1738 • 1.0. 1350 In.912 i 54xO.0489 63500 : 0.0400: 0.912 '2058 ' 1601 1544 I 543 796 1050 12601 ! 2597 .1816 . Properties of the individual wIres are those of ASTM B 230 and B 398. If the diameter is not found in Tables 4-6 or 4-7 as in the above table.1738 i 1.03211 0. 2. 1.0462 1 Data shown are subject to normal manufacturing tolerances. 1.000 3.63xO.03506 : 0.0. of Tables 4-6 and 4-7 may be used for the above table if the diameters are equal.0.0427 0.18l6 28xO.0484 59000 ! 0.1738 28x0.998 ! I 60700 10.357 i 2.0494 . etc.357 2.0425 0. Direct current (de) resistance is based on 16. for 6201~TB1 wire. Alternating current (ao) resistance is based on de resistance corrected for temperature and skin effect 4.750 2. 2.72:<0.159 3.2594 I72xO.000 2.1738 .1816 Resistance ac:-60Hz de Ralad i 2O"C I 25'C 50"C: 75' Strength ' Ohms/ 'Ohms/ Ohms! i Ohms! Ibs 1 Mile Mile: Mile : Mile 6201 i Alumi· ' num i Total Dia~_r IAlum!! 2.04551 0.0404 i 0.750 2. interpolation from the nearest diameters readily obtains the desired SMR.755 ohm-cmillft.1738 37.1816 37.0.998 1.1816 • 54xO.. 4·37 .998 1.0459 ' 0. .000 3.0434 0.357 num .0435 : 0. As the values of GMR and inductive and capacitive reactances of any all~aluminum stranded cable of a specific outside diameter are closely equal.0430 0.product identification and data TABLE 4-23 (Continued) Size AWG or kcmll I Weight per 1000 Feet Cross Section Square Inches 1350-H19 : 6201·T81 Outside .03455 0.0458 69300 i 0. the value of SMR. 3.03558 : 0.0464 ' 0. 08224 0.038 0.9 6301 7945 10020 12630 15930 19060 22730 27030 1. No. 10 3 No. Direct current (de) resistance is based on 51..1 224.089 2450 1.811 6.2464 0.721 0.00646 0.0907 0.810 0. No.3805 0.47 23.3107 0.3535 0. in.07196 0.0808 0.05356 0.07796 70.13 1.0 416.1819 103. No.127 0.7088 0. 8 3 No. Data shown are subject to normal manufacturing tolerances. .801 0.01297 001635 0.6 130.05708 0. 10 No.4458 0.06184 0.65 18.541 1.343 0.1354 0.5 1134 1430 27190 34290 43240 51730 61700 73350 02079 0.1549 01954 0.220 0.00513 0.642 0.912 3.02062 0.1819 0. No. 6 3 No. No.8936 0.5177 0.896 3.03890 0.943 1.03278 14.43 63.1285 01443 0.4796 0.0 1108 1396 1762 2222 2802 0.713 0.6050 0.6 164.33% lACS with stranding increments as shown in ASTM B 416.01028 0.25 ! 93. 8 7 6 5 --~.910 0.008155 0.5 899. 19 No.6 261.7 5658 713..01 1.486 0.37 37. 7 3 No.1649 0.1037 0.29 29. No.272 0.bare aluminum wire and cable TABLE 4-24 Aluminum-Clad Steel Wire and Strand (Alumoweld) for Overhead Ground Wire and for Limited Applications as a Neutral Messenger ASTM B 415 and B 416 Physical and Electrical Properties No.999 1.242 0.392 0. Strand 3 No.63 1000 1261 1590 2005 2529 3025 3608 4290 5081 4532 5715 7206 8621 10280 12230 7.1443 0.02446 0. 9 No.2 178.04523 0.1074 0.277 0. 19 No.651 1..222 ! 0.433 0.02600 0.365 0. Total Weight Area Sq. No. 5 No. 19 No 19 No.9615 879.04905 0.247 0.7 207. I ! i 0.3916 0.311 0.1309 0. No.3 524.7626 0.2622 i i 0.2803 0.03085 0. 19 No.5 0.509 0572 0.27 i i i i i i 52950 66770 64200 100700 120200 142800 ! i 1.0 141.4938 448. 10 9 7 7 7 7 7 7 7 7 37 37 37 37 37 37 S S 7 6 5 No.194 4.1019 0.646 0.03590 0. 2. 4·38 .309 1.1144 0. per 1000 ft de ReSistance at 20'C Ohmsl1000 ft Rated Strength Ib Ib ----------4---------T--------~--------+_------~----------- Solid Wire 12 11 10 9 8 7 i 6 5 4 .03 4669 58.306 0.01 ohm·cmWft al 20°C. 20. 9 3No. and Size of Outside Diameter Wires in.6528 1.1145 0.88 74.2264 0.5821 0.8 330. 12 11 10 9 8 7 6 19 No.81 112. No.2043 i 0.08516 0.349 0.3017 0.04247 1. No.8232 1.1620 0.06754 0.09077 0. 0.5725 0.360 66.1123 83.002 ohm~cmilfft for aluminum wires and 51.4 ! 0.8760 0.1448 0 .5 1 5.8554 I0.080 1.360 66.1.1285 0.5 i 11.735 .5161 :0.1171 10.6147 0.554 611 211.0918 0.5511 0.1490 0.1541 .557 1.9 .529 1.5362 0.1122 210.0817 0. I Total ac-60 Hz 1 Alumi.1459 0.6479 0.1147 0.1156 0. 410 0.7781.1257 0.64940.291 0.068 12.1329 0.6758 0.1320 0.757 1.690' 83.7960' 0.908 2.1 2.0871 0.3 0. MileX.502 0.004365 0.1307 0.1022 0. 135D-H19 Wires Stranded with Aluminum-Clad Steel Wires (Alumoweld) as Reinforcement (AWAC) in Distribution and Neutral-Messenger Sizes Physical and Electrical Properties Resistances i i .5360: 0.690 83.008 0.2.620 413 52.0.6825 0.721 0.1216 0.1238 0. 3-13 or 3--14.078 '2.7630 :0. CapacitiVe X~ MegohmOhmsl Miles X.1861 ! 0.72:48 0.4 1 14.4 10.237 .630 13.01 ohm--crnil/ft for aluminum-clad wires in strands and cladding. 4-39 .1476 0.438 0.9564 0.033 11.218 12 . 4/3 167.8 .4 .386 0.8979 0.5768 0. Ampacity for 6/1 ratio is directly listed in Figs.1 I 4.0. No.569 0. 2!t'C 25<C 50'C 7S"C Equiv.1 8.316 0.0.360 66.620' 611 512 413 314' 215.1182 0.79681°..940 2.100 11 .710 2.559 1.240 1.900 394.1168 0.200 6.9620 4. 66.555 1.6008 0.1327 .6896 0.330 0.01375 1.6780 0.681 10.376 0.5645 0.6377 0.500 0.100 0.940 2. in.1030 0. Mile Stranding emil Sq.1169 0.500 1.392 512 413 314 2'5 No.360 0.1824 6(1 167.309 0.52851°.4357.1624 0.370 146.product identification and data TABLE 4-25 Bare Aluminum Conductors.04831 10.690 196.6650 0. 0.6067 0.1300 0.360 0.5221 0.5346 0.600 0.106 1.1234 0.1135 0.139.003812 0.355 0.740 0.5927 0.004809 0.060 0.1266 0. Mile tn.6966 1 I .650 110.250 1.106 11.200 iO. 0.6309 0.398 0.213 .821610.1119 0.1974 1.1639 10.6201 2/5 52.1480 312. Alternating current (ao) resistance is based on de resistance corrected for temperature and for skin effect.6568 0.007956 ' 0. 210 41.395 1.600' 0.1802 Sf1 133.245 0.541 0.740' 41.6720 0.Mile' Mil.06634 10.4 '0.42:0 2.7873 !0.160 8.01002 I 371.580 9.007076 1.5585 0.6291 0.04629 66.416 0.3 ! 2.340 0.5503 0.1.6431 0.1150 10.5202 0. 105.187 ' 1.0.7 169.1 : 0.076 I 3/4 52.1203 0.690 10.008061 7.4254 0. No.4270 0.004277 1.9 1 6.08303 213.04172 69.992 12.290 11.1605 10.406 0.7 0.151 1.0038991 2.140 0.7 92.800 19. This value is also conservative for other ratios because the increase of radiating surface resutting from the larger diameter at the Other ratios is partly offset by increased 12R loss in the additional Sleel.6337 0.009543 1.0.1.990 2.0.600 105.302 1.007826 0.0 i 0.800.001073.5 • 0.4665 '0.1157 iO.487 0.930 2. '0.572 0.1053 0.291 0.5399 0.482 6/1 105.9700 0. 4 3 2 1 No. 2.600! 83.005 0.43731°.6196 0.6510 10.002660 1.1150 .84060.360 66.1385 0.697 0.8 ' 4.275 0.8422.5290 0.500 10.1228 0.002287.600 0.004926 1.8203 0.7401 GMR Phase to Neutral 60 Hz Reactance at One ft Spacing 167.9808.03671 52.1194 0.9900 '0.686 1.524 0. Direct current (de) resistance is based on 17.09122 .006665 0.380 ' 0 .6663 10.306 .600 105.547 1 0.0.703 0.115 : 1.6306.338 1.01205 0.667310.1191 0.0821.6467 0.0978 0.248 1.500 I 0.09289 132.006738 2.1860 0.1290 0.5082 0.120 10.600 No.1341 0.450 8.165 2.000! 105. 4.294 0.1429 10.1416 : 3396 I 0.059 1.1113 265.9587 I0. Weight dc Diameter Outside of Each Total pe' Rated.7369 0.6 1 11. 247.9957 0.1293 0.1153 0.819110.1099 0.686 1.377 1.417 0. ft 2.1273 0.003212 3.07234 155.082 : 1.645 .565 1.1133 1.717 0.364 1.172 '2.5865 0.370 0.363 1.9 0.129 .1225 0.5917 0.07362 105..620 512 52.800 15(4 211.006311 1. 310 41.175 1.479 0.300 11.130 2.600 9.1 0.8OO! 10.011 1.080 6.6954 10.400 I 305. Ib .71 0.003402' 2.1.335 1.1674 0.790 4.429 6/1 5/2 4/3 3/4 215 83.344 0.007563 0.008931 0.1147 '0.492 0.05637 !0.1766 428. Data shown are subject to normal manufacturing tolerances. 9. No.036 1.100 413.3 13.447 0.6447 0.1272 0.1159 iO.1222 0.700 0.800.800 0.7 1 6.06092 116.754 0.8072 0.740 41.6 269.1556 0. 110 6/1 5/2 413 314 215 No.467 0.740310.100 314133.347 0. AWG.69°1 83.09687 165.310 5.1943 1.1125 0.6027 0.455 2.642 ' 1.1221 233.006202 10.1840 0.6167 0.005604 0. 5.126 1.01353 280.8315 1.6618 0.690.657 0.05737 123.152 1.1107 0.395 0.005522 1.006498' 1. i i No.07682 0.1677 0.6 ' 0.1055 i 0.08366 139.390 0.61 176. Size and Area 1000 ft Strength I Ohms! IOhmsl Ohmsl OhmsJ' Area Diameter Ib . 3.459 2. Inductive X.1747 .3 16.100' 512 133. 7.01518 10.0.7401 41.1250 0.173 1.9148 0. num Wi.156 1.525 1.05261 87.1.293 0.030 294.0053961 1°·003807 0.7107 ! 1 0.1182 0.7401 611 52.514210.6 .723 1.952 1.1829 : 1. 0.002547 0.1263 0.1360 0.260 0. 3.0937 0. Properties of the individual wires are those of ASTM B 502 and ASTM 6 230.307 0.266 : 1.434 0.72520.963 2.7876 0.1291 0.147 1.930 222.1330 '0.552 0.003 '0.004992 2.07061 1 0.575 5/2 167.200 16.597 11. In.8590 1. 160 120 lB8 238 300 379 257 71 113 142 180 227 26.454 0.2 521.526 4.607 0. 210 310 410 0.973 8.6 31.0718 0.0591 0.2294 0.1658 0.09 ! 16.5 I 0.691 105.1914 0.0185 0.09 41.0468 0..7 0.5 19.08291 0.1841 83.5441 0.0319 0. and -H24 ASTM B 786 Rated Strength Wire Diameter Conductor Size kcmil A.643 0.82 12 10 9 8 7 I 0.1255 0. -H24.226 0.0417 0.573 0.1 280.0807 0. The rated strengthe of the -H14.bare aluminum WIre and coble TABLE 4-26 All-Aluminum Combination Unilay 19 Wire Stranded Bare Conductors Physical and Electrical Properties 1350-H19.827 7080 7950 8430 8840 9760 4940 4360 4930 372.382 0.9 124.rea sq.202 0.2 421.143 0.0 39.0 0.404 0.01297 0.1756 0.4311 250. in.36 i 6 5 4 3 2 0.6856 0.4 350.8 1.2028 0.0331 0.2642 0.0507 0.0996 0. -H26.04133 0. The diameter of the larger wire 0.2356 0.9 315.113 0.1825 0.0 336.06573 1/0 0.0745 0.1556 0.51 ' 20. In.1146 0.0452 0.03278 0. x 0.0356 0.732.1285 0.8 300. 3.254 0.4 98.1 i 167.3 i 249.5 450.0939 0.1 3.3 15.360 0.0640 0.188 1.3041 0.699 0.2483 397.0 500.8646 0.05212 0. 5.0 327.1242 0. Data shown are subject to normal manufacturing tolerances.0906 0.0653 0.090 0. The overall conductor diameter is equal to 3D 1 + 2D2 . Ib Weight per 1000 ft Ib Resistance dc-20'C Ohms/Mile Conductor 1----. 135O-H19 6.321 0.1360 0.-----.0 266.0 477.1715 0.0836 0.0253 0.091 0.1017 0.2149. and -H24 tempers are based on the minimum tensile requirements for these tempers as listed in ASTM B 609.1853 0.8 211.0234 0.1316 0.0294 0.0147 0.6 I.-----1 135O-H26 1350·H16 1350·H24 1350·H14 81 128 6. -H14.970 5.1075 0.0208 0.4371 ~: II 3830 5590 5920 6210 6910 5220 I! 5460 6100 49.764 0.2095 0.00816 0.481 2.1469 0.02599 0.1 0.286 477 604 857 1080 1350 324 410 516 653 824 287 362 456 576 726 24. The conductors fisted in this table are stranded for subsequent insulation.756 2.3122 0.3927 0.6 468.1283 0.1963 0.179 0. 6.1 1.0402 0.1440 0. -H16.0201 0.3534 0.1662 0. 4.1045 0. in.WG A.2749 0. -H16.0284 0. in.4 446.62 66.744 0.790 6. The diameter of the smaller wire Dz is equal to D. 7. Direct current (de) resistance IS based on an electrical conductivity of 61.3746 0.554 0.0909 0.24 33.3421 0.1 198. Cia. 4-40 DI~ .5 13.0 556.0570 0.0371 0.1 62.6 157. 2.0262 0.7 12.127 0.38 i 13.1054 0.53 10.656 4840 4950 5560 8090 6340 3110 3310 3720 4180 4340 2740 2920 3290 3690 234.1356 0.6 I 133.01535 0. is equal to VcmiJ area/16.74 52.1 9.374 1 I 0.1142 0.734 1.0526 0.01028 0.2% lACS.510 1720 2140 2880 3230 4000 1040 1310 1650 2080 2630 915 1180 1460 1840 2320 78.3650 0.00513 '0.756 0. D.02061 0.1219 0.2711 0. 820 251 251 2.0661 0.0850 5.230 2.1033 0.830 0. 4. 5.650 3.661 0.659 0.4 i i 106 168.669 i Min.0743 I 207 1 330: 524: 661 62.252 7xO.299 0.260 1.1303 0. 400. and Dis.270 2.100 2.528 0.0. 0.5 1 1.707 0.616 0.406 0.603 0.110 721 909 472 595 0.336 0. 37xO. in.0 350.880.450 0.610 i:~~~i .848 0.146 0.560 5.330 655 : 1.4 676i 1. I I .659 0.910 0. I Ib .0436 0.810 3.520 0.603 317 317 ' 317 0.320.0 i : I : . 0.559 19x0.616 0.0837 7xO.1642 0.310 1.1739 19.180 I 0. 8 6 4 7xO. H22X 1.292 0.0.659 0.770 3.704 0.0434 2.160 I 251 1 1. 0.707 0.471 0.0495 0.0436 6.575 0.670 2.090 I 4.419 0.140 3. I.070 1.product identification and data TABLE 4-27 All-Aluminum Alloy Concentric-Lay Stranded Conductors Physical and Electrical Properties ASTM B 801 8XXX Series Alloy 0.450 : 1.400' 4. 158 ! 158 : 158 0.603 0.110 : 2. 3 2 1 110 1/0 2/0 210 : 3/0 310 3/0 4/0 410 410 250 250 250 266.5' 24.728 0.457 7.110 2.260 4.180 5.020 Max.320.300: 2.500 1. per 0 Temper Size 01 Wires Conventional Compressed Compact 11000 It in.610 I 0.659 0.659 0.631 19xO.0434 0.0. 210 4.423 0.0820 0.020 2.703 0.232 0. 61 xO.770 3.040 0.750 3.0.0822 61.230 3. -H12X and -H22X Tempers Rated Strength Ib Nominal Conductor Diameter I [Weight Stranding Conductor No.8101 3. 37xO.800 I 3.0486 7xO.1642 0.660 3.770. 37xO.0820 0.0640 0. I 37xO.0495 0.990 6.0612 7.470 4.100 4.376 0.0.500: 350.0436 0.0867 0.475 0.410 2.1257 .0757 : 91xO.414 0.611 I 0.659 376 376 376 37.0516 0.040 6.263 0.710 3.050 78.0745 0.0650 4.537 1 0.570 0.575 0.600 5.373 0.5 397.0578 0.268 0.5 397.362 7xO.210 1. 5.8 99.659 0.0650 4. Min.860 2.169 0.0578 2.368 0.357 0.0694 0.0 300.4 336. Max.4 336. 19xO.4 336.5 397.670 1.0 1 187 199 199 199 1 235 235 I 235 ! 853 826 1.350 4. ~7 0.650 2.390 3.020 1 1 (See footnotes at end of table) 4-41 .330 99.094O 37xO.170: 2.0661 0.1033 1.5 .1331 r .8 266.464 0.513 0.860 6.8 300.6101 0. AWG or kcmll : in.290 1.2072 0.595 19x 0.840 1.400 5.666 0.612 0.4155 750 916 1.150 : 1.0974 : 19.0694 0.0 2.725 0. 2.1379 19x0.0820 .0578 0.7~ 0.706 0.0900 61.0495 0.0.0.040 i 1.134 0.594 0.140 3.6601 3.0434 0.3 49.475 0. 0.0701 0.376 : 0.0954 .1147 37.570 0.322 0. 650 1 2.660 2.522 0.0 400.0673 0. I 0.900 0.726 0.661 61 xO.810 .880 6.512 0.990 : 4.0.336 : Resistance dc-20"C Ohmsl 1000 It H12)(.6609 0.0 350.0516 0.040 4.225 0.3~6 1.332 0.724 0.180 [ 5.646 0.649 19. 6.402 0.682 i 453: 0.537 0. 3. 329 • 329 i 0.:~: 2.727 0.616 0.0.5201 1.0504 0.320 4.0.0849 61.0.830.0.629 0.300 2.570 0.576 0.1036 285 1.557 0.0 400.1357. [ 61xO.0495 2.900 2.681 0. 0.610 i i I 3~ O.178 0.0807 ' 91.0 300.1228 19xO.0810 : 91xO.537 [ 0.460 1.0.574 0. 425 1 833 51~! 1. 37.130.190 1.1040 I 61xO.705 0.1185 .910 6.0 350.390 2.1447 "1 0.400 5.729 0.142 0.800 2.661 0.0894 0.423 0.0820 0.400 i 4.456 0.1035 .0664 7xO.140 1.230 2. 267 3371 Temper 125 125 .593 0.520 0.659 374 374 ' 374 i 374 0.616 329 .900 282 262 282 397.577 I 19.423 I 37.506 0.475 0.184 0.0516 2.5 .661 0.740 2.920 4.0772 7xO.900 2.558 0.1033 0.702 0.360 1. I .820 1.400 1 3.213 0.520 0.660.0756.9901 4.0973 1 .7' 39.390 2.860 6.679 0.0863 .260 0.820 3.040 3.430.470 0.550 1.650: 4.180 . in.86~ I 3.680 2.238 1 : I : 15.910 6.320 1. 3.400 4.040 6.660 2.020 2.529 0.668 0.350 2. 4.1303 0.990 .576 0.020 4.0.710 6.0436 0.630 0.2613 0.1548 19xO.8 266. 0.866 0.0312 0.480' 13.000 ::6.540 7..0 61XO.000 06 0.800 21.600.400 I 0.770 7.935 0.770.600 13.0 1000.0905 91xO.0703 I.0 650.006 0. The conductors listed in these tables are stranded for subsequent insulation.640 -:13.775 0.0 900.119 1.0217 0.0312 0.845 0.400 6.0 61xO. Direct current (dc) r.0. rl Conductor Size kcmil 450.7.890 .893 0.153 1.800 8. 1000 ft ! in. Min.340: 3.789 0.0315 5.795 0.0347 0.640' 5. 7.770 I 4.860 I I 5.780 0.845 0.910 6.771 0.700 7.936 0.1.400 I.3001 6.0 450.780 524 524 524 1 524 3. of Wires • In.736 0.240 1 0.860 I 12.950 17.0662 0.000 6. 7.280 1 4713.300 3.280 471 13.877.031 1.0 127xO.093 I 127xO.0315 6.770 12. ~:~: 1.900 5.360: 10.2.791 0.855 0.780 0.500 i 0.0 900.813.360 10.650 4. 127xO.500 '20.2401 0.500 0.610 I 9.0 650.1145 91xO.650' 4.750 I' ! : 0.400.880 0.0 750.722 449 0.340 I 3.772 0.0267 0.773 I I' 61xO.:: 8.~ 0.829 556.736 0.----H-12-X-.3.000.1162' 61xO.1219 550.0936 127x0.730 5.900 5.900 17.0267 0.2001 3.910 6. 565 0.600 6. 4-42 '2.0364 471 [3.860 0.0173 0.010 26.0 477.0955' 91xO.l1091 91XO·0907066: 12 lxO.700 424 424 424 0.800i21.1260 91 xO.000.998 I 0.Co __ nd_u_ct_o_r_D_i_am.845 700.100 4.2.116 1 1.900: 9.0687 477.0217 0.060 1.l103! 61XO.900117.0248 0.080 941 941 841 1.010 ' 26.600 8.930 0.770 .700 0. Max.7001 7.629 0.829 0. 6.300: 8.300 3.010 26.902 0.928 0.200 i 3.400! 6.0289 : 3.853 0.1 099 127xO..659 0.280 5.815 0.5 '37xO. 5.832 0.I 9.902 0.0385 5.500 1 0.340.1135: 0.000: 1 706 4.999 0.0 500.615 550.0 650.200118.866 0.300 I 8.0742 I 0.600.0 61xO.200116.1375I 91xO.0 1000.300 6.0 II 37xO.893 0.999 847 1.060: 8.540.0 600.980 6. 37xO.1000 ft: 0 Temper Temper I Ohms/ .380 3.100 4..90~117.800 21.834 0.540115.0173 .0312 0.749 0.~~:~~.600 ~::~~ ~:~! i~:.0 500.420' 12.996 4.950113.877 1659 0.0612 127xO.750 0.4OO 4.0842 1000.449 0.-H-2 -ci Resistance Stranding 2X : per : dc-20'C No and Dia Conventional' Compressed I Co~pact .0724 0.0782I 127xO.700 7.001 600.0658 I 0. Min. Data shown are subject to normal manufacturing tolerances.0 I 37xO.0 91xO.775 0.420112.100 0.845 0.153 --------+-----~ 650.0 600.0364 5.600 37xO.864 0.950113.17.722.640 5.001 i 1.791 0.930 0.600 117.655 0.990 5.082 ' 0. I Ib .0 600.830 .0 700.890111.480 13.0777! 550.700 10. 7. 0.032 1 1.1273: 61 xO.600 3.835 0.360 I 10.500' 20.900' ! 2. Max.sistance is based on an electrical conductivity of 61.813 1 565 0.929 0.0347 0. 2.969 0.0312 7.000 1 7.0385 0.893 0.bore aluminum wire and cable TABLE 4-27 (Continued) Rated Strength _--11 f-_N_o_m_in_a_'.000 .'9908 I 706 0.890: 11.0289 0.0741 0.117 .0950 I' 550. 6.990 5.0173 0.936 0.0385 0.2% lACS. 0.001 0.300 I " ' 0. Diameter of individual wires is shown for conventional round wire conductor.0289 0. 6.0315 5.965 0.990 6.0931 1. 11.480' 13.000 6.4.736 1 .0 .500 20. 3.658 0.900 0.I I ' __ -----r------_r----+---_r--+_--_r---r---+ 0.650 4.1325 61xO.855 0.0231 0.910 6.5 556.200 i 16.3601 8.1.06591' 1 91xO.l071.700 1 5.610 9.420112.0884I 91xO.830' 9.936 0.780 0.000 .827 0.0193 ~:~~: 9.400 .0 37xO.990 5.965 1 I 612 612 612 612 ~:~~~ I ~::~ !:~ 1.891 0.0 ! 6.300' 6.960111.540 7.0217 900.813 0.340 I 0.500!' 0.152 1.938 '0.500 : 5.901 0.0267 0.772 0.0715: 0.938 1753 i 753 I 753 0.0992 91xO.0 700.960 5.5 555.0 .0 500.830: 9.477.677 1 659 750.990 6.0267 4. 1 In.430110.240.0 61xO.032 1.060 1.775 518 516 518 518 0.0231 0.700 10.0347 0.2001 3.950 '13.-ete_r 'b 1 I Weight ----.990 ' 0..1226 I ' 61xO.400 24.0 450.300 .17.700 1' 5.968 0.834 0.0248 1'3.722 449 0.813 585 3.300.968 .910.0231 600.1032 91xO.964 0.0 I ! I 1 0.775 0.0364 5. 4.908 06 0°.0794 1.0248 0.640: .0 . 9.610 0. 8 I 0. ' tn.2001 0.' 6.5 556.0289 0.060 8.772 0.700 .796 37xO.813 I 585 0..796 0..820 7.540 7.0 600.61xO.610: 9.040:.3001 6.89~1.773 0.0 750.700 10.0845 127xO.110 8.0 800.4.0315 5. conductor tension and sags. To distinguish between span length and con ductor length. Anything that increases arc length after initial stringing increases the sag.. Users of this handbook probably are more likely to work with manu facturer-supplied graphs and data for application to a specific installation than to work on the analysis of physical properties of conductors.. Technically. k-------S-SPAN . there are still several mechanical considera tions which will have an effect on installation practices and may influence the final choice of conductor. tables. and weight loading. * For sags up to 6% of span. to regard the curve as a parabola. and for a sag of 10% of span.. the error is about In %. temperature. Usually it is convenient.. The "tcnsion limits" used as the basis fot calculations in thi~ chapter are s(a:ed a" nOt exceeding a speciried percentage or the rated s. etc.. (3) creep gradually lengthening the conductor wires as a result of tension being applied over a period of many years.Section II Bare Aluminum Wire and Cable Chapter 5 Installation Practices Once the route and length of a transmission or distribu tion line has been decided upon and the correct conductor size and type selected to carry the system load safely and economically.. charts and graphs in thiS chapter werc supplied by conductor manufacturers. Diagram showing family of sag curves. the parabola results in a sag about 2 % too small. 5-1. Much of this informa tion is supplied by wire and cable manufacturers in the form of tables and graphs that are to be used by the line designer. there are two distinct types of study: (1) That which is ordinarily performed by the engineers of the wire and cable manufacturers. templates. (2) in crease of conductor apparent weight because of wind and! or ice load. 5-1 .' Supplementing these. * A family of such curves exists for a given conductor and span..-.. Line Design Factors The line designer must consider such factors as tower and pole locations and heights.-~ CLEARANCE t Fig.1 SAG=D ~ L=~ length of conductor f.. Thus. ground clearances. This will be followed by a brief outline of the work ordinarily done under manu facturer's auspices. this means that he must have detailed knowledge of conductor sag-tension characteristics as a function of span length... the greater the tension the less the sag. the latter is usually designated arc length. and these strengths are calculated in accordance with current AST~ standards. 5-1. that are related to a specific installation. a few general statements that apply to both kinds of analysis are made. and (2) that which is performed by the line-design engineer to utilize the manufacturer supplied information to best advantage. First.. Hence the first section of this chapter endeavors to show how the line designer uses manufacturer-supplied data. etc.. the line designer prepares other graphs. The mid-point sag depends on tension in the conductor. without significant error.rrenglh of the cOnduCiQr. Factors that may bring this about are ( J) thermal expansion of the conductor because of in crease of temperature above that during stringing. The sag is less wi:h increase of conductor tension.. Fig. span lengths. *If not otherwise Identified. (4) stressing of wires beyond their elastic limits. An overhead conductor suspended between insulator supports aSsumes the shape of a catenary Curve provided the conductor is of uniform weight per ft.. This can be noted from curve 15 of the final chart (Fig.024 lb per ft. To the resultant add K = 0. With full ice and wind load. plus 4 Ib/sq ft horz. Thus. 5-2 the rated strength because. for many applica. ACSR has components that have differing stress· strain characteristics. the required sag·tension analysis has been made by others. This value bas been selected as the maximum allowable tension and the No. there are interrelated factors that must be taken into account. To the resultant add K = 0. The rated strengtb of this conductor is 28. is 33. Only a moderate amount of additional work is necessary to utilize them for specific applications. the sag· tension values are shown for bare conductor (no ice or wind) at six different temperatures. according to the map below though heavier loadings are used if local conditions appear to require them. "If the conductor is.200 or 11. tbe tension as shown by cUrve 9 on the initial chart (Fig. and they normally undergo differing unit tensile stresses. These charts apply to a 795 kcmi! 5417 ACSR Condor with standard class A steel core wire and include both bare and heavy loading as defined by the National Electric Safety Code (NESC) and listed in Table 5·1. plus 'I. Fig. The resultant of the conductor weight plus ice and side wind load (which is at rigbt-angle to the line) is increased by a constant K = 0. several computer programs have been developed to do these calculations and they are available to utility and <:omputer engineers so they can do this work themselves. plus 4 Ib/sq ft horz.280 lb. wind on projected area.·in. Appl ied at 30'F. 5-2 shows initial sags and tensions based on one-hour creep. 5·3 shows final sag and tension values. Applied at 15'F. ice plus 4 Ib/sq ft wind plus a constant. Since curve 15 on the initial chart does not exceed 9000 Ibs. 5-2 shows conductor tension in Ib vs span in ft. the cable weight alone is 1.·· 112 in. it should be noted that for spans below 721) ft. In this example. However. ice at 320 F and heavy loading of 112 in. usually applicable to sections of the United States. [n addition.bore aluminum wire and coble Though it might appear that sag-tension problems re lating to these subjects could be solved in a simple man ner. for spans shorter than this. The resultant NESC Heavy loading on the conductor is 2. creep is the governing condition in determining the final sag and tensions. Fig. the allowable initial tension on the unloaded or bare conductor. curves for the highest temperature likely to be encountered should be added. To the resultant add K = 0. Thus.20 Ib per ft. wind on projected area. the final tension limit of 25 percent of rated strength at OOF is ruling.· Inilial and Final Sag· Tension Charts Jor Variable·Length Spans Two typical sag-tension charts are shown in Figs.. 5·2 and 5·3. 5·3) where the tension levels out at 7. subject to electrical overloads. However. Referring to the explanatory table accompanying Fig.432 Ib per ft. it is evident that proper selection of span length and sags for a given profile and conductor in order to minimize installation and operational costs requires a high order of engineering skill. Heavy NESC district loading map of United States for mechanical loading of overhead lines (1987 edition) . Cond. The curves of these graphs show sags and tensions for various temperatures for spans from 400 to 1600 ft.. plus 9 Ib sq ft horz. For example. 5-2) is less than 40 percent of ·In addition. Since the probable average span for an overhead con ductor of this size is about 1000 ft. differing coefficients of thermal expansion. The upper set of curves of Fig. this requirement is met. tions. when installed. the strength margin for the conductor is even more favorable as seen by the reduced tensions above 720 ft. Applied at O°F. I sag curve is drawn correspondingly. the allowable tension as shown below the explanatory table is 40"70 of 28. . Overhead conductor loadings of the three above classes . TABLE 5-1 National Electric Safety Code (1987 Edition) for Overhead Conductor-Mechanical Load Classifications Loading District Light Medium Description and Method of Obtaining Loaded Weight per foot • Cond. the lower set shows sag in ft vs span in ft. wind on projected area.100 lb for these shorter spans and does not exceed 25 percent of rated strength. the sag after 10 year creep exceeds the final sag after heavy loading.30 Ib per ft.3 percent or 9400 lbs.r.200 lb.30 Ib per ft.. plus 'h·in. ice. 5·2. and the results are available in tables and graphs supplied by wire and cable manufacturers for all com mercially offered conductors.05 lb per ft. ice. Cond. [n the example. _---_. the user should consult his conductor manufacturer. <. 795 kcmil. Some charts also include sag and tension curves for estimated maximum temperatures greater than I200F.-~--- ------- Fig.30 -. for a span of 1000 ft.__ . 5-3 . 5-2. b. 2 3 4 5 6 7 8 Obvious relationships are shown by the curves. TENSION LIMITS: a.Final (after maximum load or ten year creep) with no ice or wind at Q'F not to exceed 25% of the Rated Strength. 13 14 Wind Temperature NESt of Ib/sq/ft Constant __. Thus. Where higher operating temperatures are anticipated. Initial (when installed) with no ice Or wind at OaF not to exceed 33._---_. 0 0 0 32 120 90 60 0 30 0 Q -20 0. It shows the effect of long time elongation from JO-year creep or heavy loading if it happens to permanently stretch the conductor . Sags and Tensions. such values in this book may differ slightly from computed valUes from which the graph was made. Initial. 54/7 Condor ACSR.. 5-2.. 5-2. 11 12 15 0 0 0 0 0 0 0 0 16 0 . With ~" ice+4 Ib wind+constant at OaF not to exceed 40% of Rated Strength.3% of the Rated Strength. Because of unceI1ainties of reading values from a chart... 5-3 showing the final sags and tensions can be interpreted in the same manner as Fig. Sag Curve Tension eliI'Ve Ice inches 1 9 10 % 4 y..installation practices 15 SPAN-FEET Fig. and sag increases from 19 ft to 26 ft (curves 7 and 3) as shown in Fig. the tension drops from 6800 lb" to 4950 lb when temperature increases from OOF to I200F (curves 15 and 11). 5-4. will be different for each span and in such a series. 5417 Condor ACSR. (or Fig. From Fig. 795 kcmil. This adjustment is obtained from the temperature-tension line (curve 1) On Fig. if taken directly off Figs. Initial Stringing Chart Curves such as Figs. (Fig. and preparing an initial stringing sag chan such a. 5·4. is for a new 795 kcmil 54/7 ACSR based on a ruling span of 1000 ft and 11. an initial sag of 22. in this case. 5-2 for the ruling span as herein defined. it can be noted that tbe tension at OOF is 6800 Ibs. baving spans of differing lengths is based on taking the values off the initial sag-tension grapb Fig. 5-4. this curve gives the value of the stringing tension to be used for the particular temperature at which new conductor is installed in a section of line having this particular ruling span. from the sag-tension chart Fig. Thus. but they cannot be used for a series of spans of different lengths because the tensions. and so insulator strings will hang vertically. the initial stringing chan. 5-2 curve 5) increases to 25. This chart shows 5·4 the amount of sag for a span of any length that will result from a cOnstant tension in all spans of the Ime. Sags and tensions. 5-2.bare aluminum wire and cable SPAN FEET Fig. . 5-3 curve 5) and the tension (curve 13 in both figures) drops from 5700 Ib to 5loolb. Thus. 5·2 for a 1000 ft span at the various temperatures and plotting them as shown in Fig. 5-2 and 5-3 provide basic informa tion for use in the preliminary design of overhead lines and can be used directly for individual spans dead-ended at each end. 5-4.280 Ibs maximum ten. 5-3. or section of line between dead-ends. final. 5-2 and 5-3.ion with NESC heavy loading.4 ft at 600F (Fig. The procedure for finding the initial sag and tension in a line. as shown here. 5-4. These and intermediate values are used to determine curve 1 of Fig. of spans the line tensions must be equal so there will be no significant unbalanced longi tudinal loads on structures. This tension will require adjustment so as to allow for the conductor temperature at the time of stringing. The Ruling Span Tbe first slep in the preparation of a stringing chart Fig. Curve 1 for tension and temperature is obtained by taking the tension values from Fig. at 600 F is 5700 Ib and at 1200 F is 4950 lb. is shown in Fig. to a greater degree than that resulting from creep. 5-2. Thus.5 ft. This rule.:.8 ft for 1200F and similarly for the other temperatures. 25.:~. S._7_S. 5-4. which in effect is a weighted average taken from the various span lengths that oCCUr in the line between dead ends..:. T. hence the use of Eq. I ~ U'> 0 10 1200 o 1400 Fig. Initial Stringing Chart. The ruling span is somewhat longer than the average span. and by applying the approximate rule it i$ 1129 ft. S~l is 1006 ft..OOOft and 11.s:. and tWO spans of 1200 ft.:.: Ruling Span :.. 54. 18. The method used for complet ing the curves and obtaining the sags for spans other than the lOOO-ft ruling span is by using a parabola for the approximation of the sag values at various temperatures. J'.installation practices 50 2 CURVE 1 (j) 7000 Cl Z Sag (DI120°F 9QoF ::> o " 6000 I.::_+_S.. In order to establish the sag curves for the various temperatures shown in the stringing chart. In a parabola the sags are proportional to the square of 5-5 .. .. A frequently used approximate rule is to make the ruling span equal to the average span plus two-thirds of the dif ference between the maximum span and the average span.::._ _. that is. If the ruling: span calculated by the approximate rule were to be used. The formula for Ruling Span is S.F I- w w u.:..80 120 30 TEMPERA! URE -DEGRE S .. obtains results that often vary con siderably from what is obtained by applying Eq.. for this example a 1000 or 1006 ft ruling span should be used. the actual final sags would be greater than the design final sags.. hence tension is per curve 1.:..4 ft for 6OOF. There is no loading during initial stringing.280 Ib maximum initial tension with heavy loading. 5-1. three spans of 800 ft. Example: A line having ten spans of 1000 ft.. For Ruling Span of I. however. 5-2 to Fig.8 ft for OOF.:. the sags for the 1000-ft span of bare conductor (curves 3-8) are transferred from Fig.. Z: O· in 5000 4000 ~ a9 (D) 60°F ag (D) 30 F 40 OaF f- :"20 1 20 0 40 . t (Eq. Stringing sags and tensions for constant tension at a given temperature for a 795 kcmil 5417 Condor ACSR.+_. . 5-3 for pre-stressed conductor) is to find the Ruling Span. 5·1) in which the successive S-values are actual spans in ft. [ s" + s" T S. 5-1 is preferred. the Ruling Span by applying Eq. 22. 6 120'F 10. If strung to supposedly final sags.3 12.e.3 Sag in Feet 3. 5-4 is based on values obtained from the Initial Sag-Tension Chart.6 ft be in ft. HI = H2 and therefore in = Since Wand the constant 8 are common to both sides we have (Eq. 5·3 is also used as basis for final sag values in right-hand column. This value is on curve 4 of Fig.lb Span in Feet 400 500 600 700 800 1000 1200 1400 I .6 4. to complete the column for 600F Table 5-2 USe sag for a tension of 5.5 25. 60'F gooF 120'F Initial Initial Initial lnitial Initial Final 6800 6200 5700 5300 4950 4400 3.2 12. Completion of Stringing Graph by Use of Parabola Formula As previously noted.0 18.8 27. However. ft W = Weight of conductor. the actual final sags will be greater than planned.1 6.4 10.1 11. Since each span of the section of the horizontal tensions line between deadends are to be equal. as explained in text.7 29. 5-4 under a constant tension for all spans at a given tempera ture.9 6. An approximate rule of thumb is to string old conductor half-way between initial and final sags because when conductor is removed from a line and rereeled it relaxes.8 47.7 11. It is now necessa.400 ft. 5·2. Thus.0 57. 5-3 is to be used as basis for sag values.8 15.6 8.7 7.0 4. For this purpose. In .5-3) Using this formula Table 5-2 and Fig. conduCtor that has been removed from an old line or has been pre-stressed to final con ditions should not be restrung to initial conditions. 5-4 at 50D ft.7 29.5 14. because.2 43.ooo-foot span on Fig.3 22. From the above formula the following ratio is derived as a simple means of obtaining the required sags. 5-4.6 5.2 20. ft.2 7. 5-2 as points on the vertical line for the I. Note that these values are also listed in Table 5-2 on the horizontal line for the l.bare aluminum wire and cable TABLE 5-2 Stringing Sags for Various Spans of Bare Unloaded 795 kernil ACSR 54/7 Wt 1.2 34. the stringing of new conductor is assumed. 5-4.7OD lb. Fig.ry to find the other mid-point sag values to complete Table 5-2 and Fig. Fig. Fig.4) (400)2 (1.4 32.2 42. and Ruling Span of 1000 Ft Temperature Tension. thus. 5-4 have beell' transferred from Fig.6 ftl.000)2 = 3.5 24.4 4.ooo-foot span.0 14. lb (a constant for each temperature) D The above sag value should be corrected if the sag ex ceeds about 5% of span length (see Eg. at 22. Ib per ft S = Span length. as stated.8 3. the parabola formula is satisfactory for calculating the sags. (22. the span.2 50. WS' D::-- 8H 5-6 (Eq. The Initial Stringing Chart Fig.5 9.ooo-foot ruling span for the stringing chart Fig.3 18.8 40.5-2) in which = Sag.1 13. for Specified Constant Tension at Stated Temperatures.1 8.4 and applying it to the ratio of the spans for the 400 span the result is and so on up to spans for 1. 5-2.8 37.0 36.7 6.9 ·3. the sag values for the l. below). 5.3 O°F 30'F 5.024 Iblft.2 Note: For initial values this table is compiled from the lOoo·ft values of Fig. thus the sag at 60 0 F for a 5OD.8 9. If the conductor has been prestressed.7 16.ft span is 1/4 that of a looo-ft span (i. 5-4 can completed. ft H :: Horizontal Tension. reference should be made to the IEEE publication P-524 entitled "A Guide to the Installation of Overhead Transmission Line Conductors". at different intervals. Stringing charts are used to obtain the values used for the control of the tension and sag of the conductor. Depicted in Fig. 5-2. An extract from such a stringing sag table.2 ft for ruling span of 1000 ft. and heavy loadings are included. tension charts from which Stringing-Sag charts. WIth the advent of computer programs it is much more common to use Stringing-Sag Tables instead of charts. 5-5 is the sag-span parabola· for the conductor and conditions described in the legend. A similar parabola for emergency-overload temperature is also advisable. For a more detailed treatment of stringing methods. 5-3 for 1200 F. They avoid the need of reading from curves or interpolating from large-interval tables. This sag is shown by curve 3 of Fig. 5-5. the conductor should be run through Stringing sheaves which rurn freely and are in good condition. an amount should be added to the sag read from Fig. Only the mid-span initial sag is known from charts such as Fig. 5-4) 6H = in which D Sag in feet obtained from Eq. The Sag-Span Parabola and Templale Use of Stringing Charls A stringing chart such as Fig. but the use of the parabola for intermediate values introduces no significant error. are made. This correction rarely is necessary (see footnote on page 5-1). As the conductor is brought up to initial sag it should be checked against the values taken from the chan. Table 5-3 is from a book that contains 69 such tables for various ruling spans and for A WG sizes of ACSR in 6/1 and 7/1 strandings-with spans as short or as long as prac ticable for the specified ruling spans. The mid-point sag for the ruling span of 1000 ft most probably was obtained from a catenary curve. The same parabola is used for inclined spans. 5-4) and the curves drawn for each temperature.OOO-foot ruling span. 5-4. Other values are as stated for Eq. 5-5 is based on only the I .. equipment etc. 5-2. as is described later in this chapter. See Page 5·1 L 5-7 . During the stringing operation. 5-3 because the latter figure is drawn to cover a range of "ruling spans" whereas Fig. The sags should be checked even if the conductor is pulled. 5-3 is used as the basis for Fig. Such stringing charts are used principally as an aid in line design of transmission and distribution lines where there is not much repetition. S-5 for spans that differ from the 1000 ft ruling span vary from those for the same spans as shown on Fig. depending on user's standard for emergency temperature of bare con duetors. The mid-point sags for other spans are obtained from the parabola (also listed in the right hand column of Table 5-2). for various ruling spans. Preferably this should be near each dead-end.installation practices a similar manner Table 5-2 is completed for the other temperatures. Stringing-Sag Tables Figs. Tables for NESC light. by means of a dynamo meter. The 1200F mid-point sag for the lOOO-ft ruling span from Fig. the final maximum sag at 1200 F (or estimated maximum conductor temperature jf greater than 1200 F) will not exceed the ten-year creep design sag. Sag Correction for Long Spans If the sag exceeds about 5 % of span length. 5-3 which indicates the unloaded condition at 1200 F. The mid-point sags shown by Fig. as noted from Fig. 5-2 and S-3 are typical of manufacturer supplied For determining minimum clearance under a line over an irregular profile it is necessary to know the final sag at all points of the span. When the conductor has mid-point sags according to the Initial Stringing Chan. 5-4. are generally compiled by utilities for their own use. such as 5-4. In such cases some spans may be up to the required tension while others may nor. as pre viously described. Strung on this basis. 5-4. "' Such parabolas are easily prepared. depending on the length of the section being sagged. These sag values are then transferred to the Initial Stringing Graph (Fig. medium. in our example. The maximum possible sag for clearance in vestigations usually occurs when the conductor is at high temperature because of an emergency-load. computed as follows: W Correction (ft) D2 X (Eq. 5-3 it is seen that the sag of a bare conductor at 1200 F is greater than that of a conductor carrying full ice load. The normal differences caused by Sloping or offset COntours are discussed on page 5-8. the conductor ground clearance will not be less than that specified in the line design criteria. because from Fig. Normal sheave friction can result in uneven sag bet ween spans. These tables. or the sheave does not move freely. in the middle. to the required tension. and in spans as close as possible to the ruling span. should be prepared and used for each line or section having different ruling spans and tensions between dead-ends. These intermediate sag values are obtained graphically by plotting a parabolic curve between the point of maximum sag and the point of elevation of the suppon. The values are based oPo a constant tension of 4400 Ib and mid-point sag of 29. Sometimes the conductor will become caught in a stringing sheave. it is convenient to cut its outline in a plastic sheet as a template marked with its vertical axis. 5-6. at the mid-point of the span. and D is a tangent under C. lor . I! can be shown that the mid-point sag CD is equal to that of a horizontal span equal in length to the inclined span (in this case 18. Under these conditions it is also possible that side winds will cause the suspension insulator to swing beyond a safe . BJ = AH + Diff. Diff.arious temperatures (FI Span Length leet 0' 15° 30° i 12 230 60° I 75' 90' 1000 15 16 I 18 19 21 22 14 13 1100 45° I thence continuing lor span intervals 0110 It to 700 It 530 540 550 560 570 61 63 65 68 70 66 69 71 74 77 72 75 78 81 84 700 106 115 126 I 79 82 85 88 91 87 90 93 96 100 95 98 102 106 109 103 107 111 115 119 111 115 119 124 128 118 122 126 131 136 138 151 165 179 193 205 If a parabola is used very much. sometimes have steep inclines in some of the spans.7 t. in elevation = 33. the conductor may shorten sufficiently. This step will show the normal maximum sag between each support.7 ft. However.bare aluminum wire and cable TABLE 5-3 Stringing-Sag Values for 1/0 ACSR (6/1). so that the force on the support at tower C is upward instead of downward. and if the towers are not properly spaced a condition can exist similar to that depicted in Fig. 5-5 also may be used to find the low point of a conductor suspended between sup ports that are not at the same elevation. Such a condition is to be avoided and there should be a considerable downward force at the conductor support to prevent collapse of the suspen sion insulators or a pullout at the insulator caps.3 Ft. 5-6 denotes the application of the Fig. inches. in hilly and mountainous terrain. distance HF Span (1 _ Elev. as follows: ( ) 2 AH = CD I GB 4(CD) or in this case AH = 18.7 (I _ 5-8 (Eq. and this is found graphically as illustrated in Fig. Points A and B are located to the same scale as that of the parabola. The Uplift Condition (Negative Sag) Transmission lines. and Maximum Tension 60% of Rated Strength 1nitial sag. Sag When Supports Are at Different Elevations The parabola template of Fig. Fig. in which F is low point. In cases such as this. 5-7.7) 8. because of thermal contraction.3 Ft. it is point F that is required in order to determine adequate clearance. The outline is then drawn as the Curve AFDB. 5-5 template to an 800 ft span which has one support 25 ft above the other. the maximum sag is obtained in the usual manner from the applicable 1200F (or whatever maximum temper ature the utility uses for this purpose) parabola template. 5-5) ~)2 4(18. if the temperature drops to the lowest likely to be encountered in the unloaded condition (with no ice load to increase the sag). Thus. Point F also may be found in terms of the mid-point sag on a horizontal span of the same length provided the difference in elevation is not greater than four times the mid-point sag.). for RUling Span of 550 ft for NESC Heavy Loading for Various Temperatures. However. A graphic method of drawing the parabola is described on Page 5-11.) = 265 F 2 4 x 18. The template is then shifted until both points A and B fall on the parabola outline and the para bola axis is vertical. Formulas are also available for use when the difference of elevation is greater than four times the mid-point sag and also for critical work where a catenary curve is used instead of a parabola. Horiz. Also see right-hand column oj Table 5-2.. with a mid-point sag of 18. This condition is usually corrected by altering the tower spacing. a template might be prepared for a I. . 5·9 .0 --: . is "flatter" than that of Fig. 5-7.0 600 FT.FEET Fig.0 ~ if) 25.w 1000 FT.W " . 5-5 is prepared based on the ruling span.0 35. but done for the lowest temperature likely to be encountered in the un loaded condition. by increasing the height of the towers where this occurs. 5-8. .0 20. 5.300 lbs. 5-5 because both the aluminum and the steel are carrying their full share of the load. Template parabolajor jinal sags (ajter 10 years) oj bare unloaded 795 kcmi! ACSR 5417.0 500FT. . In some areas this temperature may be well below OOF. 700 600500 400 00 200 100 o 100 200 300 400 500 600 700 HORIZONTAL DISTANCE . In order to predict and evaluate the possibility of such an occurance.0 1200 FT.OOO-foot ruling span for -20 0 F.0 SO. The template is based on Fig.0 • > - . 1. angle (usuaUy 45 0 per !'lESe). Usually both the maximum sag and uplift curves are drawn on the same template. Thus. 5-5.700FT. or by installing dead-ends where the slope from the tower is large. When this curve is applied to a line layout similar to that shown in Fig. it will indicate a condition of uplift at support C. Fig. 10.0 400FT. 15.O 45.'. 1(~00FT. The resulting parabola.8 feet and a tension of 7. I 30. 40.installation practices 1400 FT.024 Ibljt. a parabola template similar to Fig. (from curve 16 of Fig. jor 120'F at 4400 Ib tension. 55. 5-3. wt. 5-2). RULING SPAN . 5-2 for initial stringing because this represents the period of minimum sag before load offsets Or appreciable creep occurs. Compiled jrom the 1000-jt Values oj Fig. bore aluminum wire and coble B rna tical or graphical analysis, particularly for composite conductors, The steel and aluminum components of ACSR. for example, differ as to stress-strain properties, coefficient of thermal expansion, and allowable stress, hence ACSR analysis is not a simple process. PARA$OLA AXIS I 25 FT c E tI . • 1 :G SAG 16.8 FT BHOW SIGHT LINE A-S A¥____ MiD- POIN1 SAG TO TANGENT 18.7 FT F t H~--~~_$ZL~-----~J I _265FT--! \......- - - - - - 8 0 0 ' 1 SPAN------O-! HORIZONTAL SCALE 200 FT PER IN. vE RTICAL SCALE 10 fT PER IN. Fig. 5-6. Chart obtained by application of templale of Fig. 5-5 to obtain sag when supports are at different elevations, Unbalanced Forces al Support Points [n a series of spans between dead-ends, adjacent spans may differ in length, or their supports may be at different elevations. In addition, sleet may drop from one span and ,not from an adjacent one. These conditions caUSe an unbalance of longitudinal forces at the insulator support. This unbalance will cause a suspension insulator to swing from vertical positions, or a cantilever load will be applied to a cap-and-pin insulator. If the unbalance is greater than what is regarded as good practice, as often is the case in hilly country, dead-end connections at individual spans are used to avoid these forces on the insulators. Note: For more information on this subject, reference should be made to the IEEE paper 64-146 "Limitations on Stringing and Sagging Conductors." Preparation of Sag-Tension Chans The sag-tension charts Figs, 5-2 and 5-3, that are the basis of line design, usually are prepared by wire and cable manufacturers, Differing methods are used for such work-principally those originated by P. H. Thomas, J. S, Martin, and H. H. Rodee, or a combination of them. References should be consulted for full explana tion of these methods,· All require considerable mathe 5·10 Space does nOt permit a full discussion of these methods. but a brief outline of the Rodee GraphiC Method is in cluded. that applies to a non-composite AAC conductor. along with a worked-out example. The Catenary Curve and Preliminary Sag-Tension Graph The sag curves of Fig, 5-1 are catenaries if the con ductor is of uniform weight per ft, Though such a curve can be approximated by a parabola, it is customary to obtain mid-point sags for sag-tension graphs Figs, 5-2 and 5-3, by the catenary formula, and to use the parabola for finding mid-point sags at constant stress as depicted in Fig, 5-4. All catenary curves can be defined from the values in Table 5-4, Those jn the two-left-hand columns apply to any catem"y, regardless of material. weight per ft or length. Thus. for a 500- ft span in which the conductor arc length increases by 0.30"1., or to 501 ,5 ft, the mid-point sag is 3.3576"1. of 5()() ft, or 16.8 ft, or if it is a 1000-ft span, the sag is 33.6 ft. Mid-point sag values for any arc-length elongation are similarly found for the range of applicable sag percents. They are plotted as curve D on the Preliminary Sag-Tension Graph. Fig. 5-11. for the specified 5()()-ft span. This same Curve D is on all similar graphs for 5()()-ft spans, regardless of the kind or weight of the conductor. The values in the three right-hand columns of Table 5-4 enable calculation of tension (Ib) Or tensile stress (psi) in the conductor for any arc-elongation percent for any weight of conductor and span, Thus, using symbols of Table 5-4. the tensile stress (psi) in the conductor is as follows: Stress (psi) =~ = ( ~ ) X W EWE (Eq, 5-6) or, substituting: P/W from table as Y2 of 3745 = 1873. for 500-ft span W = Weight of conductor = 0.3725 Ib per ft E = Conductor Area 0.3122 sq in, Stress (psi) = 1873 X 0,3725 = 2235 psi 0.3122 The value 2235 psi is the point On Curve B for 0.30% arc elongation and Similarly the other values for Curve B are obtained, The designation B for the curve signifies Bare-unloaded, ·See Sec. 14. lIth Edition. Sfandard Handbook for Electrical En gineers, McGraw-Hill Book Co" New York. installation practices 40.0 MIN. SAG - INITIAL AT _20 0 F I r ______________________~1~4~00~F~T.~ A 35.0 30.0 1200 FT. RULING SPAN 1000 FT. ..... f-________!.Qi2QJEL..=P~-L-_120.0 ~ c o Fig. 5-7. Condition that causes uplift force which would collapse suspension insulators and damage ties on cap~ and-pins. 0 i i--____~~..!:,I'--,L-+--i---i115.0 ;:c; -.f+---t---i----ilO.O 5.0 o I f it be assumed that the conductor is to carry ice and wind load corresponding to the NESC Heavy Loading the conductor weight is 1.587 lblft, and the stress is increased proportionately to 9520 psi, which becomes a point on curve H for the 3007. arc elongation. Similarly curves B, L, M, and H are completed. The Land M signify Light and Medium NESC loadings, per Table 5-1. The completion of the Preliminary Sag-Tension Graph before it can be used for preparation of graphs such as Figs. 5-2 and 5-3 requires the additions of index points as indicated on Fig. 5-11 to show the stress limits that cannot be exceeded. Thus, for a conductor with a rated strength of 6880 Ib and 0.3122 sq in. area, the breaking stress is 22,000 psi. If 5007. of this amount is allowable as maximum stress at OOF under Heavy loading, 33-1/3070 thereof as initial stress at OOF when installed, and 250/0 at OOF without ice or wind load after IO-year creep, then the corresponding stress limits are marked by index points on Fig. 5-11 CUrve H (II ,000 psi) and on curve B (7330 and 5500 psi). No index points are added to curves L and M because it is assumed that the design in this instance is for Heavy loading, so only values for bare unloaded conductor and for Heavy loaded conductor are required. 100 200 300 400 500 600 700 HORIZONTAL DISTANCE"':l- SPAN. FEET Fig. 5-8. Temp/ate half-outline for conductor used for Fig. 5-5, but for initial stringing at _20 0 F for 1000-ft ruling span-tension 7300 lb. i-----i-----+----+-----~D i-------r------+------+--~--~c ~----~------~----~~------~8 Method of Drawing the Parabola Referring to Fig. 5-9 the horizontal and vertical scales may be as desired. Given half-span distance 0-4 and mid point sag distance equal to D-4, a parabola titted to points o and D is obtained by: (1) Divide lines 0-4 and 4-D into the same number of equal parts; (2) Draw lines o 1 2 3 4 Fig. 5-9. Diagram for plolting points on a parabola. 5 -11 bare aluminum wire and cable TABLE 5-4 Catenary Constants for Horizontal Spans Listil'.g Percent Change in Sag and Tension-Factors for Conductor Weighing l-Ib per ft for Various Pee-cents of Elongation of Arc Length in a 1000-ft Span SYMBOLS USED IN TABLE 5·4 L = Arc length of cable, ft T = Tension at Support, Ib H =. Tension at Midpoint, Ib P =- Average Tension (T + H)!2, Ib S = Horizontal Span, Ft D = Mid·point Sag, ft W = Weight of conductor, Ib per ft Thou9h the T/W, H!W, and P!W values are for a 1000·ft span, they are suitable also for other spans; thUS, for 100 ft span, divide table values by 10; for a 2000·ft span, multiply table values by 2. A-O, B-O, etc. Their intersection with the ordinate, above points 1, 2, etc .. are points on the parabola. The vertical distances from the base line to the curve are proportional to the square of the distances of the ordinates from point O. The Stress-Strain Graph As has been stated, a sagging conductor comes to rest when the external force required to sustain its weight produces an arc-elongation percent in the conductor that equals the elongation-percent in the conductor that would be obtained by applying the same force to the conductor in a testing machine. It is customary to use stress (psi) instead of force (lb) when applying this principle to sag tension analysis. The relation of stress in the conductor (psi) and the resulting elongation (strain). herein expressed as percent of conductor length. is shown by a stress-strain graph. Fig. 5-10, which is typical for all-aluminum stranded con ductor of 1350-H19 wires regardless of size, though there are slight variations depending on stranding. The curve of 620 I alloy is similar, except that they are extended to higher stress values (because of their greater strengths). For ACSR. a different graph is used for each temperature because of differing thermal-expansion rates of aluminum and steel. Fig. 5-16 shows typical curves for composite conductors of various kinds, but each curve applies only to one stranding for that kind of conductor. Referring to Fig. 5-10 for AAC new conductor, curve 2 shows elongation percents that are obtained as stress gradually is increased to 7007, of rated strength (sometimes called the "working limit"). During this in crease the stress is held for one-half hour at 30% of rating, after which load is slowly withdrawn. It is then slowly reapplied until stress is 50% of rating, at which it 5-12 % Increase Arc Length o~:.::n (~-11 100 I i. mooo.Foot i % Sag ~e=. (~ P ·····~WH. w Vi I TW 100 ---''--.0-1-0-~=--.6-1-24~ Span ' 20413 16667 14434 12910 11786 10217 I 20416 .015 .020 .025 .030 .040 .7500 .8661 .9683 1.0608 1.2249 20419 16675 14443 12920 11796 10219 .050 .075 .100 .150 ,200 .250 .300 .350 1.3695 1.6775 1.9372 2.3730 2.7405 3.0645 3.3576 3.6273 9143 7471 6475 5295 4593 4115 3762 3488 9129 7454 6456 5272 4566 4084 3728 3452 9136 7463 6466 5264 4579 4099 3745 3470 .400 ,450 .500 .550 .600 .650 .700 .750 3.8764 4.1144 4.3377 4.5502 4.7534 4.9483 5.1360 5.3172 3268 3086 2932 2800 2685 2564 2494 2413 3229 3045 2889 2755 2638 2534 2442 2360 3249 3066 2911 2777 2661 2559 2468 2386 .800 .900 1.000 1.100 1.200 1.300 1.400 1.500 5,4925 5.8277 6.1451 6,4473 6.7363 7.0138 7.2811 7.5393 2340 2213 2106 2014 1934 1864 1802 1746 2285 2155 2044 1949 1867 1794 1729 1670 2312 2184 2075 1982 1900 1829 1765 1708 1.600 1.700 1.800 1.900 2.000 2.100 2.200 2.300 7.7892 8.0317 8.2674 8,4969 8.7206 8.9391 9.1526 9.3615 1695 1650 1608 1570 1535 1502 1472 1444 1618 1570 1526 1485 1448 1413 1381 1351 1657 1610 1567 1528 1491 1458 1426 1397 16671 14439 12915 11791 10213 2,400 9.5662 1418 1322 1370 2.500 9.7668 1393 1296. 1345 2.600 9.9636 1370 1271 I 1321 2.700 10.1569 1349 1247 1298 _=-2"'.8"'00"-......L-'.10~."'34:::68==--L.._l!..>3~2"'8_,---,-12",2=5 .-L 1277 installation practices - :r: I 20.000 I u ~ IJJ ~ Sl '"c.. i Z - 1 / 10.000 ,;" I V) V) 2 I ::::> o c.. ,;" , IJJ o I f-'" ,/' IJJ '"t 0.0 .... . .... V V) I I" - 5 .4 >- ,.... I- j V 0.1 120°F 90?F 60°F - / 3 "" , I 0.2 30°F IsoF O°F -20°F -r 8 , i i I O.J 0.4 ELONGATION PER CENT Fig. 5-10. Stress-strain curves. Conductor: ....... 397.5 kernil AAC Canna. Stranding: 19 X .1447 73°F ....... . Temperature: 2. Initial stress-strain curve after holding load I hour 3. Final stress-strain curve after holding load I hour 4. Creep for 10 years 5. Final stress-strain curve after holding load at 4000 psi for 10 years at 60'F is held for One hour, followed by reduction as before. A final slow load application is made until 70% of rating at which point the final reading is not taken until after one hour. The values for curve 2 reflect the delay at 30%, 50"1., and 70% of rated strength. By this process the conductor attains a high degree of compactness and stabilized length. Line 3 shows the stress-elongation relationship while stress is decreased from the 70% point, or is subsequently increased again to that point. Line 3 is practically straight. Subsequent increase or decrease of stress causes elonga tions that are represented by this line or one paralJel to it. The distance between the bottom of curve 2 and that of line 3 represents the permanent increase of elongation, caused by the settling of the cable strands and reduction of spaces between them, and also perhaps by a slight perma nent set of the aluminum. 5 represents the condition when stress is reduced after 10 years of 60 c F creep at 4000 psi. An increase of load shortly thereafter will likewise show elongation percents indicated by line 5. It is customary to place temperature indexes on the abscissa of such graphs as Fig. 5-10 to adapt the graph for use when the conductor is at various temperatures. The use of these temperature indexes is explained in the de scription of the application of the graph. Index-points for temperatures above 120°F are not normally shown on the stress-strain graph, though they may be added if re quired. The stress-strain graphs for composite conductors, Fig. 5-16 show a sharp knee toward the bottom of curve 3 be cause the permanent elongation of the 1350-H19 part of the conductor is greater than that of the reinforcing component due to their different elastic limits. At stresses below the knee, the reinforcing wires carry the full load. The slope of the part of curve 3 below the knee is less than what is above the knee because the cross-sectional area of the reinforcing wires is small. Because the 1350-H19 wires of steel-reinforced com posite conductors creep more at a given temperature than do the reinforcing wires, the stress at which the curve 3 changes in slope increases during the IO-year creep period. Line 4 represents conditions after lO-year creep at aver age temperature of 60 c F, but no single application of an increasing stress produces such a line. The line is the locus of points each of which is a point on curve 2 from which a horizontal line extends to represent the elongation percent after 10-year 60'F creep at the indicated stress. Also line 5·13 bare aluminum wire and cable D 15 D B I 30000 U Z a:: '" H « ::> Sag a] Conductor tension without ice or wind Conductor tension plus heavy loading 0' <J) bl C1 Maximum tension limit (11,000 psi) Initial tension limit (7,330 psi) Final tension limit (5,500 psi) '" '" " l!) « <J) a:: 20000 10 r '" a.. 5 <J) o z ::> o " <J) <J) 10000 a:: '" r 1i ,000 psi a] o H <J) 7,330 psi bl 'S:SSOP;i C] 0.0 M L B 0.1 0.2 0.3 0.4 0.5 ARC ELONGATION IN PER CENT OF SPAN Fig. 5·11. Preliminary Sag-Tension Graph. Conductor: 397.5 kcmi! 19-strand aluminum, Canna, Span: 500 ft Initial and Final Sag and Tension of a Designated Conductor, Span and NESC Loading for Various Temperatures Given the applicable preliminary sag-tension graph, Fig. 5-11 and the stress-strain graph, Fig. 5-10, we can determine the sag-tension values at which the arc elongation in percent of the conductor under sag, as ;hown in Fig. 5-11, equals the percent of elongation of the tested conductor under the same tension and temperature. Another requirement is that the stresses under the various conditions will not exceed the values indexed on Fig. 5-11 as ii, bj, and C], as previously 5-14 defined when describing Fig. 5-Il. Essentially, the process is one of graphic comparison. The temperature selected for the first comparison is the lowest likely to be encountered for the specified loading (in this case the Heavy loading). For average conditions, O'F ordinarily may be taken. An infrequent below-zero temperature rarely occurs with full ice-and-wind load, and if it should, the margin of safety is ample; also, after long time creep, the stress is likely to be below what it is initial ly. If the temperature, however, will be below OOF for long periods, this lower value should be assumed for the first comparison. installation practices 20 , D -S09 B , , Conductor without ice or wind H -Conductor plus heovy loading 2 -Initial stress-strain curve after holding load 1 hour 3 - Final stress-strain curve ofter holding load 1 hour 4 -Creep for 10 years to 60° F O'l-Maximum tension (11,000 psi) bl-Initiol tension limit 17,330 psi) 'l-Finol tension limit (5,500 psi) 3 c -Finol $tress~stroin curVe after loading to ,maximum tensIon , Sag under heavy loading 14.5' :t: U 30000 ~ Final sag. after heavy loading 1L 5 ' 'Initial sag 10.3' LLJ '" « .:::> :0 V) '" 20000 'LLJ Q. (/) £l Z .:::> 0Q. 10000 , Final tension after heavy loading, 3.190 psi 15 :f:H:+:110 .... LLJ LLJ " I ~ Vl 5 at 60° F o (/) II) LLJ '"t;; 7,330 psi bl 5.500 psi c B Initial tension 3.630 psi o 0.0 OJ 0.2: 'iO°F gO°F SO" 30·F . : 0.3 0.4 0.5 ARC elONGATION IN PER CENT OF SPAN : ; QOf -20°F Fig. 5-12. First-trial check oj tension limits. Conductor: 397.5 kemil 19-strand aluminum, Canna, Span: 500 ft The comparison is made graphically by superposing a transparent-paper stress-strain graph, Fig. 5-10, (with its grid, ordinate, and abscissa values removed) over the preliminary sag-tension graph, Fig. 5-11, so their abscissas coincide and so the initial line 2 of Pig. 5- J 0 intersects the 11 ,00 psi index mark on line H. It is then apparent that neither tension limit bl or Cl will be exceeded. Therefore, tension al is the governing condition. The superposed graphs then appear as Fig. 5-12. The sag under heavy loading (14.5 ft) is found verti eallyabove'"iil on curve D. The initial tension at oop with out ice and wind (3,630 psi) is found at the intersection of curve 2 with curve B, and the corresponding sag (10.3 ft) is on curve D. The final stress-strain curve 3a after heavy loading and holding for one hour is drawn from point parallel to curve 3, and the final tension after heavy loading (3,140 psi) is found where it intersects curve B. The correspond ing sag (11.5 ft) is found On curve D. The next operation is to determine whether the final sag after la-year creep at 60°F will exceed the final sag after heavy loading. Before moving the stress-strain graph from ar 5·15 bare aluminum wire and cable 20 D - Sag B - Conductor without ice or wind H -Condl,ldor plus heavy ,loading 2 -Initiol stressw strain curve ofter holding load 1 hour 3 - FInal stress-strain curve after holding load 1 hour .4 -Creep for 10 years Shaded a indicates ~;!;::: of creep ~ •.'~. 10 lears . Iw OJ- Maximum iens,on limit i<l 20 .. (ll,OOO)psi i~ b)-Initial tension limit (7,330)ps; CJ- Final tension limit :~ (5.500) psi 3 0 -Finol stress~ strain Curve a her load!g to () maxi murn tension .' ,'! at OOF 3 b Finol stress-strain I ij ot600F .., curve under maximum tension after (reep for ! f-"':330 PSi , '.500 r~i " iO yeors at 60° F " dOl 0.0 0,1 : (I" 0.2 I 110'f 90'F 60'F iG"F ".p -;O·F i.; "ON CATION IN PER CENT OF SPAN Fig. 5-13, Second trial to check eDect of lO-year creep a160°F. Conductor: 397.5 kcmil19-strand aluminum, Canna, Span: 500 ft its present position, the location of O'F on its temperatuTe scale is marked on the first-trial check of tension limits (Fig, 5·12) as reference point R, The stress-strain graph is then moved to the right until 60'F on the temperature scale coincides with reference point R, Fig. 5-13. The initial tension at 60°F (2,910 psi) is found at the intersection of curve 2 with curve B, and the corresponding sag (12,85 ft) is on curve D, The final tension at 60?F after heavy loading is found at the intersection of curve 3, with curve B. It will be ob served that Curve 4, which shows the elongation of the 5·16 conductor after creep for 10 years, intersects curve B at 2,570 psi. The corresponding sag (14.45 ft) is found on curve D, Since this sag exceeds the final sag after heavy loading at oaF creep is the governipg condition, A new final stress-strain curve 3, is now drawn parallel to Cutve 3 through the point on curve 4 where it intersects curve B, The final sag and tension at oaF must now be corrected~ using the revised stress-strain curve. For this purpose the stress-strain graph is moved to its former position so that OaF on the temperature scale coin cides with reference point R, Fig, 5-14, The corrected final 330 psi bl 't. These value.0 - (7.:.. I 10000 (j) (j) . The final sag after iO-years at 60 0 P after Heavy loading (14. the correspond ing tension is 10. 5-14. found where curve 3" intersects curve B.1-'+.470 psi) is found at the intersection of curve 2 with curve B. 0 . with curve B and the corresponding sag (16.. Canna.b "" 7. and the corresponding sag (15.w curve under maximum . ere not indexed on the curves. Values for O'F unloaded. <.. for 120°F the stress-strain graph is shifted until the l20 0 P point is moved to reference mark R to produce Fig. from which the initial ten sion (2. and O°F with heavy load are entered from this graph on Table 5·5.5.installation practices 20 .5 ft) is on curve D. The corresponding sag (12.270 psij is found at the inter section of curve 3. Sags and ten sions for other temperatures are similarly found and en tered in Table 5-5. .330) psi 11.000 psi'ii]i Final tension after creep for 10 years at 60°F 3100 psi Conductor without ice 3 ::j::j: ! U Z' w "" « 20000 Sag B 2 final sag after creep for 10 years at 60°f no' I I: p B I Fig.500) psi Fino! stress strain . 3 0.. Pinal tension (2.. 5-15. m (j)' Cl Z ::> -to 'Q.500psi Cl • i . Thus.fl' o ~ I~' ~3b H or wind Conductor plus heovy loading Initioi stress-strain curve after holding load 1 hour Finol stress-strain curve after holding lood l hour 4 Creep for 10 yeors at 01 60·F Maximum tension limit {11. Conductor: 397.840 psi. J: 30000 j ~P 1 R$= .5 kcmil 19-strand aluminum..100 psi) i. w 1-.(/) i ""w Q.w I ~ '? 5 o 4 R 10 tension ofter creep for 10 years ot 60° F H m . Span: 500 ft tension (3.. The sag and tension values thus far found are entered in Table 5-5 as the initial and final sags and tensions 'for OOp. 5·17 .0 ft) is on curve D..15 It) is on curve D.7 ft) is found where the ordinate at intersection of curve 3. Final trial for O'F after adjustment for lO-year creep correction. both unloaded and for Heavy loading.000)psi b1 Initial tension limit C1 Finol tension limit 3b (5. and curve H intersects curve D. . .5' Initial sag 15.500) psi S . The values from Table 5-5 are then transferred to Initial and Final Sag.bare aluminum wire and cable 20 0.Sog B Conductor without ice or wind H Conductor plus heavy loading 2 Initiol stress-strain o . '" UJ ..5 kcmill9-strand aluminum.330 psi 1i1 'final tension after ~ creep for 10 years at 60°F 2. Z ::. Similar to Fig. Values for this temperature are emered in Table 5-5. I 11.i a VI .0000 . The load values in pounds P are obtained by multiplying the tensile stress values in psi by the conductor area (0. Conductor: 397.finol stress-strain J: curve ofter holding V 30000 lood 1 hour Z Initial tension limit Cl finol tension limit 10 . 5-16). temperature coefficient of expansion.000) psi « ':::>" '"~ Maximum tension limit _ * w 10000 CiJ 7. &0 o N 3 B R &. Span: 500 ft In a similar manner. 5-10. t· 3 .330jp. such as Figs..15' IS curve after holding lood i hour :. ARC ELONGATION IN PER CENT OF SPAN H 3 2 1). the values for other temperatures are obtained to complete Table 5-5. 5·16 and data for templates for various sizes of conductors and conditions. VI (5.~ Initi~1 t~ns!o:n 2. Canna. Medium and Heavy loading provides everything necessary to com plete the sag-tension graphs that customarily wire and cable manufacturers supply to customers as a basis for their work as described in the early portion of this chap 5-18 ter. elastic . SO°F 30°f &oF -iO"F Fig. for ACSR the components differ as to elastic modulus. 5-14.. Final sag after creep for 10 years at 60°F 16.. 5-11.:1 120l>F 90·F 0. Completion of a similar series of values for other spans and for Light. but with considerable difference in details because the reinforcing wires have different physi cal properties from those of the 13S0-H19 wires (Fig. Sag-Tension Graphs for Composite Conductors The graphic method used for the preceding work simi larly can be employed for obtaining sag-tension graphs for ACSR and ACAR.~ 7QPS. Thus.270 psi bI 5~?~ ~~i .and Tension Graphs (similar to Figs. t>. The manufacturers also supply a wide variety of graphs. w 17.000 psi VI VI w o bl (11. 5-15.) 0 . but for 120°F without load.3122 sq in)..5 O.0. 5-2 and 5-3) at the 500-ft span ordinate..3 b finol stress-strain curve under maximum 0 tension after creep far 10 yea~s at ~~o F . In ACAR the creep rates and temperature coefficients are not significantly different. and allowable unit stress.installation practices ACSR THESE CURVES DIFFER SLIGHTLY DEPENDING ON TEMPERATURE - (/) Q. finding sag-tension data for ACSR at a specified temperature requires the use of three stress-strain graphs.2 0. Con- limit. 5-l0. (/) (/) 10000 w 3 0:: !i:i 0. The allowable unit stress in the two kinds suit cable manufacturer for accurate curves depending on reinforcement ratio. and one for each of the components (aluminum and steel). 20000 2 4 3 (/) (/) 5 w 0:: !i:i 10000 0.5 2 (/) Q. 5-16. The location of the break in curves 3 and 5 depends on this ratio. The designation numbers of the curves have the same meaning as those of Fig. For example. rate of long-time creep. Typical stress-strain curves for various kinds of composite conductors. but because of differences of elastic limit the elastic moduli differ greatly in the upper range of stress.5 ELONGATION PER CENT Fig. The graph for 5·19 .. one for the entire conductor. of wire also differs.1 ACAR-6201 THESE CURVES ARE SUITABLE FOR ANY OF THE USUAL CONDUCTOR TEMPERATURES ..4 0. 5-17). psi P Ib 14.05 14.910 2. 5-14 and 5-15 AFTER 10 YEARS FINAL i Temp. 5-17. 5-11) is used unchanged for composite-conductor analysis.15 11.45 15. are plotted on the same sheet (Fig. .270 the complete conductor (Fig.3 11.8 12.470 3.45 12. 1I". The process is tbus mOre complicated than what is used for AAC and AAAC.1 10. The preliminary sag-tension graph (such as Fig.4 16. but the basic principle is the same..5 9. The grapb for the 1350-H19 wires is obtained by difference.132 1. of Loading Sag i 0 -20 0 30 60 90 120 ~-.460 3.'jO- Fig.~.260 2. and also for the reinforcing alloy wires.5 II i I I T.78 14. Similarly for ACAR.080 979 i 895 803 759 709 i Sag ft T.430 2. but readily available ref erences provide full information.280 1. All three graphs. Because of the necessary space required for an ade quate explanation of the details of preparing sag-tension graphs for composite conductors. 5-16) is made by test in the usual manner.670 2. psi 10.0 15.0 13.000 4.100 2.bare aluminum wire and cable TABLE 5-5 Listing of values obtained from Figs.840 3. The effect of ratio of steel area to aluminum area is taken into account when preparing the graphs.385 i 1. ec.. Typical Stress~Strajn~Creep Curves for a 5-20 IM/l!) "CSA lleo_ol~" 1!!<6(P<~ ACSR conductor .7 10.440 1.. Stress-Strain Curves. A similar graph for the steel core is made by test The stress-strain graph for the aluminum is then obtained by subtracting the values for tbe steel from the values for the entire conductor.860 2."" $II/1~ S.018 907 834 772 the entire conductor. stress-strain graphs are made for ! INITIAL P Ib I 3.630 3.. it is only the superposed stress-strain curves that differ. a description of the method is not included herein. however.100 3. ! ! Heavy 0 0 0 0 L~ I I ft 14.570 2. Flat Armor Wire: used for wrapping around conductors to protect them from chafing. or bus structures often are of combination types that embody design features de scribed in Chapter 11 for insulated cables and Chapter 13 for bus conductors. Thus. tee. Tie Wires: attach the cable mechanically to the top of pin type insulators. lns/allalion is simi lar to A except that the filler sleeve is Inserted in one end before injecting compound. 5-21 . or the term may refer to a connector fitting used in such an as sembly (see Fig. c F. Connectors also are designated according to use. a jumper connector may refer to a short length of cable to which connectors are attached at each end. 5·19A). Suspension Clamps: support the conductor at tangent or light angle structures usually through suspension in sulators. Tubular Aluminum Compression Joints. 5-18 and 5-19. 5·18. Armor Rods: surround and reinforce cable near points of support. These are described in Chapter 6. E-For ACSR with extra large core. compound injected. Customarily. cables and terminals for a desig- nated use. Dead-Ends: hold the mechanical tension and provide an chorage to a strain insulator at end of a span. or where overhead lines connect to insu lated cables. as compared with those of EC grade. The aluminum sleeve is placed over one cable and run back. parallel or tee tap. A B AWM. A-For ACSR. and steel sleeve com pressed.installation practices Overhead Conductor Accessories and Fittings Wire and cable accessories for aluminum overhead lines are similar to those used for copper lines. Sometimes the term connector also is applied to a small assembly of connectors. to which reference should be made for details. The aluminum sleeve is then positioned. but it is essential that they be designed for aluminum because of differences of physical properties of aluminum and copper. ajter which the aluminum sleeve is compressed. Connectors carry full current. ~lEI!: PlUG Fig. Joints for line con ductors are made by compression of the conductor ends within a long sleeve or tube. and sometimes is used instead of armor rods in short spans. such as for terminal. Vibration Dampers: reduce resonant vibration. the fittings and accessories for overhead lines are classified as follows: Joints and Connectors Joints carry full current and withstand at least 95 per cent of the rated strength of the conductors. used to "jump" across the insulation-support struc ture where adjacent conductor spans are dead-ends. filler C-For al/-aluminum conductors. in such cases the filler compound must be injected into the ends of each sleeve before inserting the conductor. Connectors also may be of the compression type. underground lines. Sometimes filler plugs are omitted in joints used in distribution circuits. or may be bolted or welded. and filler plug driven in place. etc. and limited tension. cables joined. Fittings used at terminals. The aluminum wires are then cut away to provide room jar the steel sleeve which is then inserted. See Figs. Compression sleeves jar high-strength-alloy conductors should be suf ficiently large to matcn the increased tensile strength oj the conductors. A joint is sufficiently strong to develop a tensile strength equal to at least 95 percent of the strength of the con ductors it joins. The compression sleeve is welded or forged to a flat-bar pad drilled according to NEMA standard. B .. B-For Tee Taps. The direction of take-off may be straight or at an angle.~ I ill! .. but where the cable tension is comparatively low.ll:I: . In the open-run type the long sleeve is split longitudinally so it may be 5-22 placed sideways over an aIready-installed run conductor. .r ""'-7 : ~ -f. D-For Flat-Pad Side Terminals-The compression sleeve is usually of the open-run type. Used on short lengths of aU-aluminum conductors that join adjacent dead-ended conductors. C-For Flat-Pad End Terminals. It is of the split type.bare aluminum wire and cable ~'~ '-Y'. Conneclors are used for joining comparatively short lengths where full conductivity is required. 'dd lli8 c ~ D ~ ~( E - - - - - - - - - - :. A-For Jumpers. the long sleeve is placed on the conductor from irs end. In the closed-run type.4S Fig.--~ '':=:.:. IJ OPEN RUN ~"V. so the tap may be made from an installed conductor. 5-19. Or it may serve os a joint between conductors of the run. j .::. The same connector is used for ACSR as for all-a/uminum conductors because the added strength of the steel core is not required.. Tubular Aluminum Compression Connectors. . E-For Cable Repair (Repair Sleeve)--The repair sleeve is applied to strengthen a cable where strands have broken or local damage is suspected.'l-I - ~ \F= i . 5-20. 5-21A3. all-aluminum and Alumoweld conductors are shown in Fig. and -5. Bolted fittings are available in a wide variety of types. None of the bolted dead-end fittings differ for ASCR or all-aluminum con ductors. The use of additional clamp-bolt assemblies in series is another way of increasing holding power. Tubular aluminum compression dead ends for ACSR. 5-24. but also bind the armor rods to the conductor. Figs. The latter is used where maximum holding power is required. Fig. and the bodies may be of cast. the line may be looped downward. After preheating. welding of stranded cable to terminal pads should be a shop operation instead of being done in the field. and also for connecting or supporting bare aluminum cables at terminals or connecting them to other cables. a transmission line required hundreds of jumper cables to span the support towers where dead ends are located. by placing the pad fitting in a vertical clamp jig following suitable preparation of the cable wires. Figs. They are easy to install and offer little handicap to future circuit re-arrangement. -4. Tie Wires Aluminum tie wire for attaching cables to pin-type insulators comes in rolls. 5-21. it is possible to achieve such strength by employing the snubbing principle. and it is also used under hot· line conditions. Continua tion of the cable beyond a dead-end may be provided by a jumper cable with end connections suitable for at taching to the dead-end. For example. and continued through the opposite dead end to the next span. or may be run downward to a terminal. 5-26. and is available as regular strength wire in Nos. each somewhat larger in diameter than the conductor strand diameter. The ends are bell mouthed to avoid sharp bends. weld metal was puddled in by gravity. The rods are spirally twisted so they lie approximately parallel to the conductor strands.installation practices Dead-Ends and Dead-End Clamps Fig. 5·23 . Bolted Clamp Connectors Bolted aluminum clamp connectors are used extensively in bus structures. hence are mostly used for cables of moderate size. The advantages of welding cables to terminal pads are most evident for the sizes of cables for which com pression or bolted fittings are bulky and comparatively costly. after which the weld was completed to provide contact between the ends of all wires of the cable and the terminal pad. In the snubber dead-end. 5-25. So far as possible. and the tie wires not only tie the rod-and conductor assemhly to the insulator. and 2 AWG sizes and as Strong Aluminum Alloy Tie Wire in No. Although the usual damp-bolt connection of an ACSR or stranded aluminum cable will not withstand the full tensile strength of the cable. across. The method of application of tie wires for attaching a cable to a pin-type insulator is depicted in Fig. Thus. 6. Typical Cable Suspension Clamp tor support ing cable at boltom ot a suspension insulator. Both ends of the jumper cable were shop welded to a flat-pad bolt-type terminal. which in turn may be either bolted or welded to a matching flat pad or other fitting. The cable is not looped around an insulator or thimble but is gripped in a horizontal body by U-bolts and pres sure bar. the holding power of the fitting is increased a great deal. Armor Rods These are generally used on overhead lines to protect the strands from fatigue-effects of vibration near points of support. arranged around the conductor to form a complete protective shield. 4. Suspension Clamps Suspension clamps support the cable at the bottom of insulator strings. The greater ductility of the regular strength wire somewhat speeds completion of a tie. 5-21AI and A2. forged or extruded aluminum. 5-22. Dead-end fittings hold the cable against span tension and provide attachment to the strain insulator. Fig. They consist of an assembly of aluminum rods. by looping the cable around a semi-circular grooved body of a snubber-t~l'e dead-end fitting. 5-20. Fig. Added protection of the conductor at insulator supports usually is provided by armor rods. then allowed to cool. and providing a hump in the clamp between the two clamp bolts. Aluminum bolts (2024-T4) of the heavy series type or equivalent U-bolts are widely used. For city distribution where design tensions are relatively low straight-Jine dead-end clamp fittings are much used. if required. Normally the clamp has two U-bolts and a pressure bar that clamps the cable. 6 AWG. Other com pression-type and bolted-type dead-ends and dead-end clamps are also shown in Fig. Welded Conneclions Welding as a means of joining components of an alumi num connector fitting is recognized standard procedure but direct welding of stranded aluminum line cables is presently limited to welding cable strands to the body of an aluminum terminal fitting. no separate jumper con 5·24 nector is necessary. ~ . A--Snubbing-Type Dead-End (AI and A2). A4. The line cable is looped around the fitting and clamped below by the double-U bolt pressure joint. The clevis is attached to the strain insulator. Types A3.. run across to the adjacent dead-end and run upward and continued in the adjacent span.:. . In many cases. and AS are straight-line dead-end clamps for limited tensions. B-1 and B-2 are parallel-line clamps for making taps. B-Miscellaneous Clamp-Bolt Connections. the line conductor is merely looped down through the clamp filting. " j! . B-4 is similar.. B-3 is a typical tee tap in which the branch connection is bolted. Clamp-bolt connections. particularly for distribution circuits Or where there is likelihood of future clOnges.bare aluminum wire and cable ~A-1 8-3 A-2 ~A-6 ~ ~~ . :[ 1i ~ ~':J • A-3 8-1 8-5 Fig. Clamp-bolt connections are widely used. Applying bolted clamps to the two cable ends completes the dead-end connection. 5-21. Though single clamp connections usually are suitable for full conductivity. The hump between the bolts also aids holding power. The use of multiple connections as well as employ ing the snubbing principle enables bolted connectiOns to aluminum stranded cable to meet all usual requirements as to strength. special construction is re quired if the fuli tensile strength of the cable is to be with stood. except the branch is a compression fitling. 1 . B-S is a terminal-pad bolted connection. Type A6 is an aluminum thimble much used for connecting a looped-around cable to a clevis pin. ~!NAl WELO' CHAMfER Aluminum-to-Copper Connections ~ __ ~ Connecting aluminum cable to copper bushing studs and switch pads is often necessary. large compression·type lugs... In making such a connection (Figure 5-23) with other than aluminum bolts. St661 or Bronze Coppe.1 Washer Aluminum COI. .* ~ ~ . Stud Flat St.. Belleville spring washers and heavy flat washers in consecutive ar rangement as shown in Figure 11-11 must be used. bearing on the aluminum lug. For connecting large aluminum conductors (500 kcmi! and up) to heavy equipment having copper terminal studs and or pads...m Compression Lug Bron. Welded connection between stranded alumi num cable and terminal pad for transmission-line jumper cables.d. 5-23.._ I) I - ~I - --~/i I : I t INITIAL POODLE WElD IN STRANDS I I TAPE l I I RelIEVE EPGE J STEEL "8ANO-IT"-+ I DET/H '0' END CUT I Fig. 5-22. Equivalent Copper Or 'Alum.re ftad Fig.. and this form of con nection for the high current ratings has received ex tensive study to assure long-time reliability under normal and short-circuit conditions.·/ Contact Paste No-Ox-Id A Special 0. 01 _______ FTO '//"¥r... is necessary. should be used.. preferably with two holes..ct..installation pradices Straight and heHcally formed armor rods are avail able.. Each formed rod is essentially an open helix with a pitch length somewhat less than that of the '''lay'' of the outer strands of the cable .. 5-25 .nt'l. Method for connecting large aluminum conductors 10 equipment studs or terminal pads made of copper. If aluminum bolts and nuts are used only the heavy washer. If bolts are made of aluminum it is not necessary to provide the Belleville spring washer.inl. 5-26 B-For all-aluminum conductors. ~~~ 'ffl . After com pression of the steel sleeve. .bare aluminum wire and cable A NONMETALLIC AU. The attachment to the strain insulator may be of eye or clevis type. Tubular Aluminum Compression Dead Ends. BOLT$. A-For ACSR. The assembly comprises an inner steel dead end body and an outer aluminum dead end body. 5-24. The conductor is run through the aluminum body. and the tongue extension to the jumper may be single. DEAD END 80DY SUB-ASSEMBlY EYE DEAD END " ~ SEAL -. ALUM. The steel body includes steel sleeve which is first compressed on the entire con ductor. \ li'l"DIA. C-For Alumoweld conductors. The steel eye or clevis dead end has a comparatively short shank which is ribbed to iransfer the tensile stress from the aluminum compres sion sleeve to which is welded the flange and terminal pad jar the jumper. SUPPLIED AS PART OF JUMPER: TERMINAL FILLER PlUC NONMETALLIC SEAt c FILLER SLEEVE SLEEVE STEEl EYE DEAD END Fig. and the aluminum wires are Cut away to expose steel strands jor insertion in the sleeve of the steel body. . .or two-way. An aluminum filler sleeve is placed between the conductor and the aluminum body.M. the aluminum body is posi tioned so that ofter compression the aluminum body is clamped to the aluminum wires and also to the ridges around the steel body. after which the aluminum body is compressed over the ridges of the steel body and the conductor. The flange of the aluminum body extends outward jar bolting the terminal pad of a jumper connector. 5-25. and the plan views show actual configurations for single and double insulators. The conductor is shown protected by armor rods.installation practices Fig. Though the sketches show the conductor as ACSR. 5-26. For side lies be sure that the insulator has a large enough groove to hold three turns of the tie wire selected for use. Arrangement oj tie wires for aI/aching a cable The looping arrangements are shown schematically. Field as- 10 SlOE TIE pin-type insulator. 5-27 . Formed armor rods. SINGLE INSULATOR - DOUBLE TOP TIE SINGLE INSULATOR SIDE TIE DOUBLE INSULATOR _ DOUBLE TOP T! E DOU8LE INSULATOR - Fig. both jar side tie and across-top tie. sembly starts at points marked B and continues outwardly. the same ar rangement is used for all-aluminum conductors. Make ties as snug and tight as possible. twisting by hand except for the final two turns which should be made with pliers. . This temperature is frequently used for 1350-H19 conductors since the strands retain approximately 90 percent of rated strength after 10. Ref erence is also made to aeolian vibration and conductor galloping with a brief description of devices that reduce their effects. 6-1 A. Such matters as voltage drop'. Short-Circuit Performance The ampacity data in Chapter 3. all current values used in the discussion of overload conditions are in terms of rms symmetrical amperes. the dura tion of the 60 Hz fault current is usually only from 3 to 20 cycles for transmission circuits but may be longer for distribution lines. The critical voltage-drop limitations of the National Electrical Code relating to circuits under NECjurisdiction are mentioned in Sections 21O-19(a) and 21S-2(b) of the NEe. as temperature is not measured. the ex tent that emergency overloads may be carried without serious damage and the effects of arcing-burndown.) For ACSR the strength is even less affected because the steel core is essentially unaffected at these temperatures. accompanied by the heat effect of current. B. (See Fig. For ACSR or A WAC conductors with sizeable steel content (not the 18/1 or 36/1 strandings) an upper limit of 645'C represents the threshold of melting for aluminum with the sleel expected to supply the needed mechanical strength. the time in which the fault must be cleared can then be determined. a useful and practical alternative is to use the Fault-Current Burndown: Failure caused by overheating as a result of a current overload. The curves of Figs.000 hours at temperature. Short circuits in a power system can result in extremely large currents in conductors from the time of fault initia tion until its interruption by the protective device. 6-2 A. Figs. B. the total fault-current time will be the sum of the interrupting times. Only those re lated to the conductors themselves are considered herein. Figs. Heating will generally be more rapid than cooling. If the circuit is immediately re established by automatic reclosure and the fault has not cleared. system regulation. The terms used herein relating to overload matters are as follows: Thermal Limit (as associated with steady-state overload conditions): The maximum temperature at which a con ductor can operate continuously yet maintain the mini mum tensile properties established by the manufacturer or the user. such as circuit breaker or fuse. and C apply this criteria using an average specific heat and assume no heat loss from the aluminum strands during the short duration of the fault current. Fault-Current Limit: The current (temperature) and time combination which produces the maximum accep table loss in conductor mechanical strength. and the methods of computing drop or obtaining it from industry-supplied tables are described. Subjects covered' in this chapter include the ability of the conductor to withstand short circuits and their related mechanical forces. >I< Applying to bare transmission and distribution circuits only. 340'C has been selected as the maximum temperature for all-alumi Current Values: Unless otherwise stated. 6-3.Section II Bare Aluminum Wire and Cable Chapter 6 Operating Performance and Problems Operating problems occurring in installations of bare overhead conductors are of several kinds. 3-11 to 3-15. transi ents and calculation of probable short-circuit currents are in the province of the system electrical engineer and be yond the scope of this book. current-time product and neglect the temperature slopes. In establishing suitable fault-current limits. and C do the same for ACSR conductors. 6-1 . apply to steady-state normal operation for bare ACSR and all-aluminum conductors for temperatures up to 1000C (60 0C rise over 40 0C ambient). With modern relaying. However. and loss-of-strength estimates would require integration of the temperature-time curve for temperatures above the arbi trary "damage" level. When limits have been established. num conductors since momentary exposure to this tempera ture does not result in a significant loss of strength. applying to conductor sizes used mostly for interior circuits. Arc-Current Burndown: Rapid failure caused by the heat of an arc on the surface of the conductor. The conductor strength decreases sufficiently to cause tension failure. 2 percent lACS conductor. and change of color over a considerable area. 6-1 by For Upper Limit 3000C 250'C 200'C 1350-H19 6201.6 sec for that current.771 0. aluminum's resistance to and multiply time from Fig. For other conductors. 6·1 and 6. the total time of fault currents is usually very small relative to emergency oper ating time and is therefore igoored as an effeet on con. the ad vantage of aluminum in this respect aids measurably in reducing operating costs. From one group of tests. limit is advisable." AlEE Technical Paper No. Then for 6201~T81 it will be 2. slight roughen ing. thereby enabling the current-limiting devices to be properly set. but for lower distribution voltages in metropolitan environments consideration should be given to arcing burndown. whereas the jault·current limit time (there being no local arcing) is 1. apply these factors after applying those as listed in the preceding section.721 400"C 0.ordination on the basis of fault· current limit time usually is satisfactory. For the usual transmission line.903. for relay settings of protective devices on distribution lines that may be subject to arcing buro dovvn. there are conditions where a lower temperature.903 For ACAR conductor.691 0..J5) ~ 2. a /1. Clearances can. Table 6-1 contains representative data from arcing tests conducted with the conductor under tension. however. ductor strength. As this conductor size is not sh. or 2. However.2. "Power Arc-Over On Overhead Distribution Lines and New Developed Equipment for Protection Against Conductor Bumdown From That Cause.80 X 0. 4145.5 kcmH to 2.own by Fig. . 6.250 amp.80 sec for 1350 H19. For 241 13 ACAR. the time is obtained by interpolating between values for 417 kcmil and 566. A.' Loss of Strength The loss of conductor strength due to time at tempera ture is a cumulative effect. such as when the bare cable is confined in switchgear or in switching compartments.53 sec.65) + (2.51 X Q. lightning. particularly for the smaller sizes of ACSR. 1941. The temperature-time strength loss re lationship is covered in more detail in the section on emergency loading (Chapter 12). For example. such cases.80 x 0. Martens. 6~1.814 0.556 300°C For 6201-T81 and ACAR. Usually the value that is specified as the estimated fault current is the known quantity. Arcing Caution must be exercised in applying the fault-current times. relay co. When subjected to arc currents. 4/0 AWG 6/1 ACSR under 1700·1b tension has arcing burndown time of 10 to 14 cycles (. 6-2 by For ACSR Upper Limit 0. Arcing locally cuts into the conductor quickly in 6-2 . copper terminal pads.167 to . under assumptions applying to Fig.233 sec.) at 15. Multiplying factors for these conditions are as follows: Multiply time from Fig..903 0. While arcing failure times are so short that little if any change in tension can occur prior to failure. also may warrant a lower temperature limit.845 500'C 0. C.000 rIDS 60 Hz fault current. momentary contact with a tree limb. and the corresponding time is found that wiU cause the upper temperature limit to reach 340°C over 40'C ambient for 61. 6-1 may be adapted to 6201-T81 and ACAR conductors by applying suitable multiplying fac tors. and the like. multiply by 0. the aluminum conductor sUlface frequently shows only a removal of sheen. Other con.T81 0. or those at the higher distribution voltages. dilion" such as the use of soldered. The effect described applies to arcs of less intensity than those that produce arc-current burndown.559 Aluminum conductors resist damage by arcing better than conductors of other metals because the arc tends to cause less pitting and surface metal melting. see the applicable portion of the following example: Examples: Assume 500 kernil conductor and 20.2 are suitable for bare overhead conductors. high fault currents can heat the entire line. initiating an arcing problem.71 sec. be as sigoificant a constraint on maximum acceptable current as is conductor strength.0. The reSUlting increase in sag can establish contact with ground or other conduc tor. there fore. Also see Table 6. the time wiJt be (2. Arcing Effects Adjustmentjor Upper Temperature Limit Whereas the upper-limit temperatures specified in Figs. surface damage from such minor arcing was evident with arcs ranging up to about 78 cycles duration.bare aluminum wire and cable Adjustments for 6201-T81 and ACAR Conductors Values from Fig. as described. In actual practice.1. Heating due to short circuit occurrence should therefore be added to heating due to other circumstances to estimate the condition of the con ductor. in the many instances where small arcs result from flashovers.621 0. the time for the 1350-H 19 conductor is multiplied by factors as below: For 6201-T81 conductor. 01 7 6 2 100 3456789 1. rms 2 I z :IE 9 8 7 6 5 . cmils = amps. L~ I\: t 2 AWG en 0 0 4 Lil Y.0671m I L 4 Awtl . 6-1A.000 2 3 4 5 6 7 8 9 0.005 100. and C.<l ~ 4.1 I \ \ L&J L&J 6AWG \ \ z '-' 3 ~ ~ A \/ = ( O. 4 3 '\ '\ \ ~ r\ en 0. -. A. Maximum fault-current operating limit for stranded aluminum conductor.000 2 3456789 10. ~~ 8 7 6 5 1\ ~ 2 1\ 1\ 9 8 0.t m I \ \ \ = seconds.operating performance and problems 3 " r\ 1\ 2 1\\ l\ \ ~ _\ \ -" 1\ \ \ \ ~ \ 10 9 8 7 6 5 ~ 4 \ 3 1\ 1\ \ 2 1\1\ \ /\ \ 1\ 1. 6-1. ambient temperature 40°C. 2.l. B. Graphs asSUme there is no heat loss in the conductor.0 9 ~. BARE STRANDED ALUMINUM CONDUCTOR '-- I I/O AWGJ li. The curve for all aluminum conductors may be applied to alloy 6201-T81 and ACAR conductors by computing the equivalent 1350-H19 cross section. Time plotted is that required for a given rms fault current to cause conductor damage due to annealing.I2/0AWG ~ 1\ \ \ ~ \ \ \ 1\ 1\ 1\ 1\ / \ \/ 4. = area.000 CURRENT IN AMPERES Fig. Note 1.1 1'0\0 /\ )2. 6-3 . Upper temperature limit 340°C. The current may then be determined by extrapolating for the computed cross section USing Figs. Time plolted is that required for a given rms fault current to cause conductor damage due to annealing.0' / \ 1\'. t seconds I m = area.000 CURRENT IN AMPERES Fig. and C. cmils I = amps. rms / '/ / / / ~ 195. The curve for all aluminum conductors may be applied to alloy 6201-1'81 and ACAR conductors by computing the equivalent 1350-H19 cross seclion.400 emil V ~ " 3!Q AW 9 I I . 6-1 B.\ \\ \~\\ j\ j\\\' ~~ ~' 1\ t\"0~~ ~ a t 265. 4/0 AWG !x \/.000 emil I 411. A.000 emil I 556. ~ . i\ . 6-4 .0 9 B 7 \\\\ 6 5 \. 1. I I I I 11111 t = .\. Upper temperature limit 340°C.800 em . 2.\ \ 4 0 I \ I 1\ 7 0.067Jm ) 2 .\\' 4 0. 6-1. 7 \ 6 5 w 3 '" z 2 \ 1\ \ \." 3 '" • \ \ \\\ . \ l\ \ 1\\ ::E 01 I 9 B r\ 1\ 1\ 1\ . B. 6 5 2 IL / '~ i\ I\r'\ w > ~II / 954 000 em 115. \ 1 \ X\ \\\ . ambienltemperature 40°C.000 emil t 391.bare aluminum wire and cable 3 2 ~ \ \ 1\ \ i\ \ " \. \ 1\ \ 1/ ~/.000 2 2 3 4 6 789 10. Note: 1.000 1.005 • 1.000.500 emil I I \ \ 4 '-' / 1/ t\\\ • 9 B z / I \\\' r-. Graphs assume there is no heat loss in the conductor. The current may then be determined by extrapolating for the computed cross section using Figs.000 emil I 605.\\ \ \ \' ~~ 2 0 H \ \\.500 emil ~ i\/ / / K>(/ V 336.1\ BARE STRANDED ALUMINUM CONDUCTOR 3 J..0 . 7 ". Maximum fault-current operating limit for stranded aluminum conductor. I ( O. L.000 em'l t 636. I I . .vI ! '" <:> 5 1. The Curve for all aluminum conductors may be applied to alloy 620J-T81 and ACAR conductors by computing the equivalent 1350-HJ9 cross section. 6-5 .000 em. 2 ! t = ( O. Time plotted is that required for a given rms fault current to cause conductor damage due to annealing..431. I I z 0 4 I 1/1/ 1/(. Maximum fault-current operating limit for stranded aluminum conductor.}92. Note: 1.r 1/ i I 1.0 1. The current may then be determined by extrapolating for the computed cross section using Figs.033.SOIl cmll . 1. Graphs assume there is no heat loss in the conductor. B.351. I 9 0.. 1 I ! 2 ! 1:590. 6-1. 6-IC. A. 7 .. . .510. 9 8 .. cmils I = amps.3 2 ! 10 9 8 \\' \' 7 6 ! 5 : '\ 4 . t - 8 5 .272.01 9 8 1 . ambient temperature 40°C.r 1/ .1..500 em.. ::IE I I .000 emi 3 '" i. .000 emi.. Upper temperatllre limit 340°C. BARE STRANDED AlUMINUM CONDUCTOR 4 D 1 . 2.000 CURRENT IN AMPERES Fig.1 7 6 .. rms ! 0. -1 V .000 emi I / 1/ / /1 ! I 7 6 I = seconds m= area.OOll em.. and C. r / / 17 V [7 V I~ ! 1/ i <> 1. 5 6 I 6 4 5 9 1 4 100.500 emir 2 z I LlI).0671m ) 2 . " o Z o <.000 CUR R EN T IN AMP ERE S Fig. Time plotted is that required for a given rms fault current to bring aluminum strands to the threshOld o/melting.....00 3456189 ItOOO 23456789 10.....bare aluminum wire and cable (I) . . 2.> . Graphs assume there is no heat loss in the conductor.oo~ 2 . 6·6 Note: 1. Maximum Fault-Current Operating Limit for Bare Stranded ACSR conductor..000 2 3456789 100. ambient temperature4QoC. Upper temperature limit 645 0 C. 21--->- o.. 6-2A.. :E . . \ ~ ~ ~~ l\ 4 3 2 ~' 0. cmils amps.500 emil 1. ~ / \ \\ 1\\\ \ \ i\ 2 emil 1605. rms I I I 8 c\ 7 . am~ient temperature 400C. / I 631.500 emil ~ ~- i\ .000 emil / 1397 . \\' \ 6 5 \ \ \\ \'\\ ~\ 1\ !\\ \ \\ ~ ~ 1\ \\.0862m I m I 4 !IQOO ) 2 'I = seconds m = area.01 9 8 7 6 0005 5 S 789 00. 6·7 .000 L \\\ \\( ~ ~\ V '\ / / '\ \ \ \ \ \ \ \ \ \ 79! .000 emil..000 CURRENT IN AMPERES Fig.\.0 9 8 7 I 47: . Graphs assume there is no heat loss in the conductor.~ \ 4 I I / / \\' ~~ ~~ emil D( 6 5 en c Z 0 '" '" <J> 2&•.000 3 / ~~/ L ~~X / ~y. II .800 emil I z: 2 I 4/0 AWG II '" ::IE .000 emil I 556.1 I 9 X BARE STRANDED ACSR CONDUCTOR \ A. \_ ~/\ V \ 1\/\\ 1\ I = (O.operating performance and problems 3 2 ~\ \ i\\1\ ~i\ !\ 1. 3/0 AWG 0.500 emil 4 I 336.400 emil 3 / Y.\\ \' \ 1\ 5 \\ '\ . Note: 1.1\ L7. Upper temperature limit 645 0 C.\ \ .\ l\ \ \ \\ \\~ ~\ \ I 954. Time plotted is that required for a given rms fault current to oring aluminum strands to the threshold of melting. Maximum Fault·Current Operating Limit for Bare Stranded ACSR conductor. 6·2B.\ 10 9 8 7 6 '\ '\ '\ \ \ \ . 2. Maximum Fault-Current Operating Limit for Bare Stranded ACSR conductor.\ ~ u I . 7 6 5 ~ 4 I 3 2 V 9 6 en 0 6 z 5 0 "-' V 1500. cmils I amps. ~ I / 2 I I 3 4 100. . 6-2C.0862m ) 2 .01 9 8 .500 emil .000 cmil I 1.500 emil 7 6 7 I I 6 0.bare aluminum wire and cable 3 2 ~ ~\ ~ 10.35. BARE STRANDED ACSR CONDUCTOR K I I. 6·8 Note: I. Graphs assume there is no heat loss in the conductor..000 emil I I :IE /1/ 1.191.0 7 : . 8 I .000 emil ~\V :.1 .510.e': 3 en z V L. I. 9 . t '" seconds I m'" area. 2. . ~ i . ! ! ( O.1I3. I I.OQO 'mil 0 / "-' 0.431. I '\ 5 4 .000 cmil ~\ V V V. / V 2 V i I i. ambient temperature 400C.272.033.000 emil 1. Upper temperature limit 645 0C. rms ! I . I III! 2 t 6 f= '" I . 3 0.780.000 CURRENT IN AMPERES Fig.005 I .500 cmil 1. Time plotted is that required for a given rms fault current to bring aluminum strands to the threshold oJmelting. 5 8 10 10 9600 11.. as previously mentioned. i. some designers and test authorities consider that a suitable current value for computing maximum short--circuit force is the root-mean square value of current in the first current loop. the instantaneous peak value.m. for calculating the force between parallel conductors under fault conditions. The electro-magnetic lateral force between long par allel current-carrying conductors is proportional to the product of the instantaneQus values of current in each con ductor and inversely proportional to their distance apart. 5.4 kcmil·1811 ACSR 350kcmil·19stt. show the com· parative times for arc~current burndown and normal fault"'CUrrent limit when there is no arcing to conductor sides. the higher instantaneous value is normally used. because the inertia of the conductor prevents an instantaneous deflec tion response to the applied force.250 18. as a maximum. Amp ! I ! Min cycles . See Eq.500 15.). 6-1. 1965).828 I. this condition. 6-5) if the fault is initiated at a zero crossing of the voltage Wave. 6-5).750 18. the fault-current wave will be symmetrical if the fault is initiated at the peak of the voltage wave. but it wi!! be offset (similar to Fig. 6-1 and 6-2. spacing between conductors and lateral force. the high electro-magnetic forces of fault cur rents sometimes can be an important factor in line design and equipment selection.800 4.) for alternating current (shown in line CT in Fig. 10 14 21 12 9800 15.400 14 18. By similar analysis. with fallit current lagging nearly 900 . Amp cycles . tension Ib Description I Min cycles Amp : i ! .600 18. Ie (Eq. The following equation shows the relation between the short-circuit current expressed in various ways. 6·5 (at zero power factor = 1. Under TABLE 6-1 Arc-Current Burndown Times on 60 Hz Basis For Bare Conductors Under Tension From Tests· I Conductor. Oct. Gaertner (Edison Electric Institute. which for zero power factor ap proaches 2. However.5 15. B. Goode and G. approaches value OA.200 12 18. designated maximum rms asymmetrical current.732 X 1=.700 1 7 8 . are stated in terms of root-mean-square sym metrical amperes (I.m. However. H. 6-9 . The point of initiation of a fault is usually referred to the voltage wave because this is the non-variable: the current in both mag nitude and phase angle is dependent on the load while the voltage magnitude is practically constant and the phase angle is fixed in time.3 15. For a fully offset wave. 1350 I 1456 1326 1701 1701 1350 4550 4450 8425 26 53 25 1076 4800 19 1456 4800 42 : 3Jil I i i 4800 9100 8580 15. For three-phase circuits. which approaches the value represented by the line OR of Fig. 1350 500 kcmil·37 str.200 8 8800 22. equivalent values are obtained for currents that provide electro-magnetic forces between the conductors of a balanced three-phase circuit. However. The heat effects of short-circuit currents. with those obtained from Figs. i 2 AWG·7/1 ACSR 310 AWG·6/1 ACSR 410 AWG·611 ACSR 336. the vector direction of the three forces as well as their instantaneous values must be known.6·1) F=G--- dlO T Transmission-line faults are practically limited in magni tude only by the reactance of the faulted circuit. in a paper by W.200 ! Min Amp Min cycles 15.4 X 1.operating performance and problems Fault-Current Electro-Magnetic Forces Between Parallel Bare Wires and Cables Fault currents are more likely to cause thermal damage to bare overhead conductors than mechanical damage.450 11 ! ·The arC-<lUrrent burndown times are reported from tests at Baltimore Gas & Electric Co. These values. 7 Ib per It II 7 X 12 X !O. due to emer gency conditions. 1. 6-5). is different from the action of more rigid bus conductors described in Chapter 13.17 X 5. and side-sway friction? I ft -~ From table 6-2(d) the applicable multiplying factor G is 4.bare aluminum wire and cable where: F = Pounds per linear foot of conductor G = Multiplying factor.::: "" == .. elasticity. and I. subjected to a fault current of 20. Fig. IJ50-HI9 wire..4 X 20. if a conductor is heated under emergency loading for ten hours each year for a period of ten years. The curves permit estimates of the change in strength of conductors which have carried emergency overloads.000 = Spacing between centerlines of conductors in inches Example: Assume a flat 3-phase circuit of 210 AWG-6/1 ACSR on 7-ft spacing. shifting of additional loads to an already loaded conductor. and use of high loadings to prevent icing are some reasons for such overloads./ ~ / I I I L 10. The question of what maximum conductor tempera tures should be permitted for emergency operation de pends on how much loss of strength is allowable and how long the emergency-load temperature continues. The effect of heating is cumulative.. or in d-c amp d 10. 6-3. which usually have very long span distances compared to separation distances. the average force F during the first current loop. = Short-circuit current in each conductor a-c symmetrical rms amp..5 0. assuming zero power factor is 4. Time-temperature percent strength remaining in An example is cited. . oc... the mechanical action of stranded conductors.. As an example..1 . Applying Eq. as in Table 6-2 I. Tensile tests made at room temperature after wire exposure to the indicated temperatures. 6-1. Experience and testing have shown that this action is not damaging to the mechanical strength of conductors or insulators. but it must be carefully considered in the de sign and selection of spacers and dampers.000 500 / / / II I 100 50 / Emergency Loading "" == <= = 1 .. Under fault conditions. based on the following assumptions which should not be considered typical. 6-3 delineates the effect of time on 1350-H19 alu minum strand strength at three temperatures which are of interest to power engineers.000 I I ~/ r-:q . 6-10 I I 3 2 / '/ 100 90 80 70 60 PERCENT REMAINING OF INITIAL STRENGTH 1 0. 6-5) without allowing for mechanical damping. Coincidence of peak loads with high summer ambients.000 amp rms symmetrical (line CT of Fig.000 2 F =---------- 5. ::IE I II en 10 7 5 en <= " Transmission and distribution conductors are oc casionally subjected to current overloads. Fig..17. The conductors can slap together violent ly-especially the subconductors of bundled conductor lines-and traveling waves move longitudinally along the line.. which produce temperatures beyond the normal thermal limit. caused by inertia. the total effect is nearly the same as heating the conductor continuously at that tem perature for 100 hours. What is the average lateral force exerted on the center conductor caused by an rms symmetrical fully inductive fault current in the first offset loop (line OR of Fig. The cumulative effect of a succession of short-time fault-currents during short circuits where high temperatures are possible plus emer gency operation at lower temperature can cause conductor strength loss which is of concern..? z w .:. conductor emissivity and the resulting actual conductor temperatures is seldom very precise. 6-3 and 6-4. component stress levels and differing creep rates at elevated temperatures to determine the effect of high tem peratures on final sags is very complex. If the conductor were of the same size. 100 i 300 200 TEMPERATURE DEGREE C Fig. Breaking strength tests were made at room temperature after Vz hour exposure to elevated tempera tures.600 Ib-about a 24"1. loss. there is much less reduction in strength. ambient tempera· ture. Vibration and Fatigue of Overhead Conductors' An unprotected or improperly protected overhead con ductor may undergo wind-induced vibrations under cer tain conditions to such an extent that fatigue failures of strands will develop at points of restraint or support. ! At the end of 30 years. R.200 lb.6 kcmi!) ""AWG "\: I 2000 1350-H19 ~ ! 1000 I o .900 Ib would be re duced to approximately 10. The analysis of the interaction of the thermal expansion rates. ~ u. 13S0-H19 9000 ! ! \i 8000 7000 ! i ~ 246.operating performance and problems ( 3) Maximum temperature for emergency condition. High temperatures for time periods whleh may seem short in terms of the life 01 the conductor can result in significant changes in sag--especially for the conductor constructions which do not have significant proportions of steel. "'Wind Induced Conductor Motion. the creep rate used for predicting 10-year final sags and tensions is based on the creep rate at 60°F.9 kcmil 6201-T81 I : : ." Figs. (1) Emergency conditions exist for 24 hours each year. EPRI Handbook. 6-4 shows the effect of 112 hour of heat ing on similar conductors of three different aluminum alloys. are also drawn from data having inherent variability. 6-4. The "damage curves. or a 10 percent reduction. E. They therefore may be used only as a basis for a very approximate estimate of the actual condition of the conductor. Similar failures have been observed at or near splices and .. Short time exposure to even higher temperatures can occur. the strength would be reduced from 31. Larson. 'w" . i i 4000 I I 3000 ~i\ \ 1--0 (211. which is essentially unaffected by the temperature range considered for emergency overloads. As was noted in Chapter 5. Using Fig. Strength loss is rapid at temperatures above ISOoC." contains an excellent treatment of this subject. (2) The uselullife 01 the conductor is 30 years. Harvey and R.". I 5000 '"cow Z W I . 6·11 .. A t}'Pical practice is to limit emergency load tempera tures to a maximum of 125'C. '" '"'. but 2617 ACSR.. knowledge of the actual conditions-current. For momentary exposure to elevated temperature. 6-3 as a guide for the estimate. However. Reduction of breaking strength of aluminum and aluminum alloy stranded conductors of equivalent conductance. The creep rates at l50'C of the all-aluminum and aluminum alloy conductor are considerably higher than those of corresponding sizes of ACSR at the same tempera ture.500 Ib to 28. ISOoC (302 0 F) (4) Conductor: 795 kcmil-37 str. the strength of 13. wind velocity. '"" ~ 6000 : : J: I. The advantage for ACSR is due to the steel core. the conductor will have been heated to 1500 C for 720 hours. time. A method of practical calculations is presented in IEEE Paper TP 69-674-PWR by J. and Fig. 45 rms of first loop B 4. 6-12 .93 same Aor C 6. or of Symmetrical RMS Alternating Fault Current.bare aluminum wire and cable TABLE 6-2 Multiplying Factors for Maximum Short Circuit Lateral Force Acting Upon Suspended Parallel Wires and Cables in various Arrange ments Assuming Balanced Loading.93 3-phase a-<: rms of first loop A.89 Direct current* '-phase a-c symmetrical d (bl A 0 B 0 1-phase a-<: d A~ 0 (cl '< i /A'. See NEMA BU-' for adjustment factors if fault-current power factor differs from zero.m. in Terms of Direct.0 asymmetrical Aor B 8. or C 6.0 1·phase a·c rms of first loop Aor B 5. the transient and over·shoot at fault initiation renders it common practice to use a factor of 2. or resonance effects from support vibration. as determined by XlR ratio.0 is satisfactory.17 same Aor C 3.32 because it is usual practice to designate fault currents of apparatus and lines in terms of rms symmetrical amperes (I. B. 8.17 asymmetrical B 6. Type ot circuit and designation of location on current·wave of (al Arrangement of fault-producing circuit current d A 0 B 0 Conductor upon which force is applied Multiplying factor G Aor B 1_0 Aor B 2.m'). 6-51 = I.0.B'Y 0--. or C 4.-0 l-d~1 3-phase a-c (dl l_d_l_d_1 A B C 0 0 0 3-phase a-<: I • Although steady·state direct-current implies that a multiplying factor of 1. NOTES: All values assume a fully offset current wave in a fault of zero power factor without damping. Amp (Line CT. This arrangement of factors differs from that of ANSI (37.55 3-phase a-c asymmetrical A. Fig. other discontinuities. Sway or side swing is the most obvious and simplest form of conductor movement in an entire span. asymmetrical of ac component EF = Minimum peak current values Norc: A value slated as closely approaching a designated limit is considered as cOlnciding with that limit for computation pur poses. 2. The results of many years of sueh research have been made available to the utility industry by cooperating manufac turers and technical institutes and universities. the conductor will tend to vibrate in many loops in a vertical plane. An osciJloscope trace shows that the difference is slight in most cases. DQ. These phenomena have been extensively studied at out door test sites m which virtually any type of overhead conductor operating condition can be duplicated. Conductor vibration and oscillation may be divided into three general types. Aeolian vibration is a resonant vibration.- r~ -- f" T - 0 c \. It is the least readily observed and usually the most damaging type. vortices are detached at regular intervals on die lee side of the conductor-alternately from the top and bottom portions. the hardware.. Aeolian Vibration ot Conductors The accepted explanation of the wind-induced phe nomenon known as aeolian vibration is as follows: When a comparatively steady wind blows across an overhead conductor under tension. or components of the supports or towers.operating performance and problems A 1\ ~ Rr '-. as well as of moisture and temperature. The conductors vi brate in much the same way as any string under tension. Aeolian vibration and galloping present the most serious problems. is such that the conductor becomes eccentrically glazed or ice-coated. The envelope of mo tion usually is an inclined ellipse. l. the vortices tend to be detached in synchronism 6·13 . A movement pattern develops in which the entire span oscillates as a whole or in a few loops. - i ~" 1\0 V'-~ :. with amplitudes of several feet and at low frequency. Galloping is re ported to have been seen infrequently even with the conductors free of ice. It is caused by steady crosswinds. F F OS = I. - . r-- ~ I=:::'~' -===f> B _-1-' - - Distances represent comparative current values as follows: CT == It'lll" symmeticaJ~ CB = l lx'lll> symmetrical OR ::: I. limit to which value approaches OA I""" asymmetrical. If the frequency of the forces corresponds approxi mately to the frequency of a mode of resonant vibration of the span. Hmit to which value approaches OD = Peak of de component. Typical curve 01 alternating current wave during offset short-circuit (X/ R aboUl 15). 3. The most common types of damage are actual failures of the conductor. 6-5.-- - - I __ f-. and damage may also occur to sup porting structures and hardware. As the amplitude of vibration increases. Frequencies range from 2 to 200 Hz. largely in a vertical direction.. since either of them may lead to failure of eon d uctor strands at points of support or at other discon tinuities. Fig. limit to which value ap proaches T__ B I-J -- ."" asymmetrical.. In addition.. It is caused by crosswinds or short-circuit forces. The frequency of these forces increases with increasing wind velocity and with decreasing conductor diameter. The conductor is thus repeatedly subjected to forces that are alternately im pressed from above and below.. there might be damage and service interruptions caused by phase-te-phase or phase-to-ground contacts during severe galloping.. Gal/oping or dancing is the movement that sometimes results when the interrelation of wind direction and velocity.. S /\ 0 ~ ". and are nOw widely accepted. When movements between the strand surfaces are repeated a number of times. conductor vibration has been observed. in the form of in creased amplitude-the crest becoming higher and the trough deeper. and diameter of the conductor and . Further movement between strands. with one or more somewhat loose auxiliary conductors from 4 to 12 ft. When a wave reaches the end of an undamped span and is reflected. Each wave. thereby producing standing waves. In exposed areas with steady winds. The standing-wave loops thus formed have frequencies that are multiples of the fundamental frequency of the entire span. At the ends of the span the reflected traveling waves are superimposed on incoming traveling waves. of mechanical energy from interstrand friction. Vibration Dampers Perhaps the first device of any value for reducing 'ibra tion was the festoon damper. which. Fricke and Rawlins.he expected range of wind velocities. If the damper and conductor span can dissipate energy at a greater rate than that at which the wind imparts it. 6-14 rubbed repeatedly against each other or against an armor rod or clamp. long clamped to the tensioned conductor at each side of a suspension point. During its subsequent travel. and this causes flexure of the damper cable. one damper is installed near one span support point. The observed relative absence of vibrations at higher wind velocities can be attributed in part to wind turbu lence. a few lines with tensions as low as 11 percent of ultimate have suf fered damage. neither its amplitude nor the energy stored in it is significantly diminished by the reflection. the wave acquires more energy and greater amplitude until an equilibrium ampli tude is reached where dissipation in the conductor matches input energy. Cracks appear within the disturbed layer and-under the vibration stresses present in the conductor-may pene trate into the undisturbed metal below the fretted region. Another reason why vibration of significant amplitude does not generally occur at high wind velocities is that these cause high vibration frequencies. pp. is attached to the conductor by means of a clamp at the midpoint. In certain areas where local wind turbulence caused by broken terrain Or trees reduces the power input of wind. Tension is normally taken as that for "final condition" at about 60'F. :he vibration of the span is suppressed to harmless prop·.. It has been found that protection from damaging vibration is most evenly balanced over the range of ex pected frequencies of line vibration when the damper is spaced so it is approximately 70 percent of a free-loop . additional dampers may be required. each crest and trough. Conductor vibration is usually not observed at wind velocities above 15 mph. It was not until about J930 that successful damp' ing control was achieved by the introduction of the Stock bridge damper. the contact between metal surfaces is not a plane contact but rather a contact between asperities (minute projections). Because of the rela tively large mass of the damper weights..6. Hence. The probable explanation of the phenomenon of fret ting is as follows: Flexing of the conductor at the point of support results in a small amount of movement between adjacent strands in the conductor or between strands and adjacent members. No. The intimate contact between asperities. although where high tensions are used and where there are steady winds of up to about 30 mph. somewhat higher tensions have been used on otherwise unprotected spans without resultant vibration difficulties. stores part of the energy it receives from the wind during the course of its travel. Fatigue of Conductor Strands· Close inspection of fatigue failures has shown that cracks begin at fretted regions where the strands have $: IEEE Transaction on Power Apparatus and Systems. breaks these welds or the metal adjacent to the welds.. aided by the wiping action-which removes surface films-results in micro scopic welds between the asperities. i.bare aluminum wire and cable with the vibration to increase the amplitude. and a disturbed layer is formed on the strand surface. and the self-damping or internal dissipation of energy in a stranded conductor increases rapidly with frequency."·rj. PAS-87. the steel sup~ porting damper cable is not stiff enough to force them to follow accurately the motions of the cable clamp. Conductor vi bration is almost never observed at low stringing ten sions. No exact tension limit can be defined which will assure complete self-damping protection.e.e. June 1968. Vol. The forces impressed by the wind on the conductor produce traveling waves that move away from the points of application of the forces toward the ends of the span.1384. weight. With new efficient damper de signs and usual conductor tensions and span lengths. Cracks are graduallY opened in the disturbed surface layer by the forces involved.lS. For long spans. however. This device consists of two weights attached rigidly to the ends of a resilient steel cable. The selection of damper sizes and the best placement of them on the spans are determined by the tension. At the microscopic level. 1381. which results in slipping between its strands with consequent dissipatior. Debris produced by the fretting can be seen as a fine dust surroun<!jng the fretted area. Fig. however. limitations of 25 percent final tension and 33 percent of ultimate strength initial tension with no ice or wind at the design loading temperature were established for controlling aeolian vibra~ tion. Micrographic studies show that the surface layer of a strand is severely disturbed by the fretting.. even with dampers. The tendency of a conductor to vibrate increases rapidly as conductor tension is increased. less than about 10 to 12 percent of ultimate strength. i. in turn. many welds are made and broken. but only rarely has fatigue damage been observed when tensions have been 12 percent of rated strength or less. 6-7. ft Figs. weights. For other maximum stead y wind velocitie s.21 1. 6-8 for a maximum steady w ind velocity of 15 mph .4 Hz .3 = S. Ib g w = Conductor weight. 2 ft to allow fOT approximately one ·half lenglh of Ihe suspension clamp Or insulalOr groove.2f (Eq. Fig. mph d = Conductor diameter. the spacing is increased 0 . in FLL Other types of vibration dampers ha ve been used in cluding torsional . Ib per ft Example: Assume a span o f 795 kcmil·2617 ACSR at tension of 6250 Ib (20070 of rated strength) ("posed to a steady transverse wind of up to 10 mph . 6-2: f = 3. fac tor the spacing by multiplying the JS mph di sta nce by (IS/ prefe rred veloc it y in mph). The spherical configuration of the end clamps of spacer-dampers used on EHV lines reduces surface gradients.70 X 7. Fig.26 X 10/ 1.26 V/ d (Eq . They are popular on lines employing three or four subcon ductors per phase. 6-9 shows a s imil ar solution where armor rod s are used . Lawrence River. The most popular system. 6-3) f and where: f = Frequency of conductor vibration.000-voll line of aluminum across the St . 6-2) (Tg/w) y. Dimensions of Stockbridge-type dampers. 6-6.4 length (from crest 10 crest on the same side of conductor). When armor rods are used. = Acceleration of gravity.108 = 29. thereby avoiding corona. = Free-loop length between amplitude peaks of conductor vibration. spacing is measured from the mouth of the clamp . Stockbridge-type dampers are used on the individual conductors of a bundled line . designed to dissipate vibration energy. It has been confirmed that the leeward conductor of the pair usually vibrates at greater amplitude than the windward conductor. dash-pot. free loop 2 X 29. Determination of the free-loop length is as follows: = 3. and recommendations as to the number to be used for various span lengths are obtainable from the manufacturers. From Eq . spiral. A t dead end s. Armor rod s shorten the end loop by II percent. and provide vibration control as well as the spacing function. modified a s noted above . 6·) : FLL = = 7. is the one described. Installing a 735. and variations of the Stockbridge with extra weights and eccentric weights. cycles per sec v= Spacers and Dampers for Bundled Conductors Undamped horizontally bundled conductors used on long-span high-voltage lines with spacers at the customary 250. 32.operating performance and problems (6250 X 32. 6·15 . FLL=-. conductor vibration . th ey s hould be of such length that d a mpers can be mounted at proper s pacings ju st be yond th e rod end s . hence the spacing would be approximately 0 . impact. ll ft from suppon . Fig. Wind velocity. length from the fixed end of the span for the highest ex pected frequency. though this distance may vary with the design of the damper. A Stockbridge damper. are plot ted on Fig. however. Normally. Values from Eq. Precise data in th is regard should be obttti ned from the damper supplier. Spacer-dampers. 6-7. Substituting values from the conducto r tables. Allhough dam per spacings usually are given (rom the center or Ihe suspension clamp or ins ulalOr groove Ihe fixed end is more nearl y the point of tangency nea r the end of (he clamp or groove . visco-elastic.to 3oo-ft intervals typically vibrate with about half the amplitude of a single conductor of the same size under identical conditions.2 ft/sec' T = Conductor tension.094) Vl From EQ . 6-3.J ft . are also used frequently. 6-10 and 6-11 depict typical types of spacer dampers. . INCHES T = Conductor tension Ib at average temperature. Fig. \ 1\ \ 1\ \ '000 . \ \ \ \ "''' " \ \. \ ~\ . 6-11. Spacing between damper and tangent support center to center or to mouth oj dead end. ..IotO OAM~1l: .. 15 mph maxi· mum vibration· inducing wind velocity assumed. .0 CONO\J(TOP DIAMETeR .. 1..~ \\\~ 1\1\. 15 mph maxi· mum vibration·inducing wind velocity assumed. \ \ 1\ \ \ 1\ . 6·10. Fig. W = Conductor weight lb/ft.e \ 000 . EHV 21e bundle/phase spacer·damper. • .) T = Conductor tension Ib at average temperature. 6·9. lOOO ~ \ \ ~ lOOO5 ! lOOO I 0."" \ I "'" '" l '"'" i\ \ \ . 6·8. \\ \\ \ 1\ 1\ ~ 1\ \\~ \1\ \ ". SPACINC -INCHES •• • . EHV 3/e bundle/pnasespacer·damper.INCHES. \ \ \ 0000 \ \ \ (1)00 . Fig. .. \.. Fig. Spacing between damper and tangem suppOrt center 10 center or to mouth oj dead end.2 CO"-iDUcrOIl: OIAMliTEIl: (Use rhis graph when armor rods are not employed."0 \ \1 \ \ 1\ • \ \ \ \ \ '" \ \. 6-16 . \ 1\ 1\ \ \ I \ \ \ \ .) W Conductor weight Ib/rr.bare aluminum wire and cable • l'. • (Use this I(raph when armor rods are employed. . Gen erally in compact round construction. Bare and covered conductors generally have Class AA or A stranding. Com pact conductors. Where extreme flexibility is desired. with each succeeding layer of strands laid in the opposite direction and designed so the outer layer has left-hand lay_ The direction of lay is defined as the direction the strands diverge when the cable is viewed from the end. especially when used in overhead applications. are generally designed as single conductors for direct burial or use in raceways. (See Section 310-13) . Condudcm lor Use with Covered or Insulated Wires or Cables Aluminum conductors for insulated and covered power cables are most commonly 1350 aluminum. or H-19 temper. bare conductors have been described. (2) covered. as for portable cords. Concentric conductors for insulating are increasingly compressed or compacted. 7·' . In the preceding chapters. The hard-drawn. Insulated conductors are designed to confine electrical charge within the conductor at a predetermined maximum voltage gradient and operating temperature under wet or dry conditions. Added flexibility may be obtained by various strandings using a larger number of smaller wires for a given cable size. including bunched and rope lay.'s will deal with covered and insulated conductors. The number of strands varies with conductor size and Class of stranding. or (3) insulated. are contained in Chapter 3. Insulated conductor temperature ratings in the NEe are based on use in wet or dry locations. (See Table 4-8) Descriptions of stranding Classes. This and several following chapte. Also see definitions in i\rticle 100 of 1987 NEC. C or D stranding. ASTM B 231 specifies details of the various strandings for all common wire sizes. Bare and covered overhead cables are generally of concentric construction with right-hand lay. electrical conductors are designated as (I) bare. Insulated conductors are generally concentric stranded. Insulated conductors. or as components for multiple-conductor cables. looking along its axis. have diameters approximately nine percent less than those of standard concentric cables and are the result of fully compressing the successive strand layers and eliminating most voids within the conductor. is acceptable for most manded applications. For compressed stranding. The ratings of insulated conductors are determined by appropriate tests and established in ap plicable industry standards. conduc tors fabricated with an 8XXX series electrical grade alloy are now common among most building wire types in both AWG and kemil sizes. The Distinction Between Covered and Insulated Conductcm* It is important to distinguish between an insulated con ductOr and a covered conductor. with some cables designed for higher ratings dependent on the type of insulation used. However. the concentric strands are all helically applied in the same direction (unilay). except for portable cords with Class G or H. Temperature ratings of conductors range from 6()OC to 105 0 C. such as those used in most building wire types. The 8XXX series electrical grade alloys are a relatively new class of alloys notable for excellent thermal stability and creep strain resistance.Section III Covered and I nsulated Wire and Cable Chapter 7 Review of Types and Applications In their broadest application. The N ationaJ Electrical Safety Code defines covered condUctor as "a condUctor encased within material of composition or thickness that is not recognized by this code as electrical insulation. Details on the various sizes of this type of conductor in the bare stranding are given in Table 4-27. the concentric conductor strands are compressed to reduce the cable diameter by approximately three percent.. with intermediate tempers half and three-quarters hard also being employed for som~ applications." Insulated conductor is defined as "A conductor encased within material of composition and thickness that is recognized by this code as electrical insulation" ~ESC 1987). bunched or rope lay strandings are used. ASTM Stand ards B 800 and B 801 cover other details of this alloy group in both the bare wire and stranded condition. insulated power cables employ Class B. unjacketed assemblies of conductors. while utility companies are generally governed bv the National Elec tric Safety Code. Insulated conductors where ap proved for that use are suitable for direct burial in earth. and are generally available in sizes through 2000 kcmiL Conductors are selected On the basis of application considerations such as temperature rating as related to ampacity. Class A strandings. we will consider 600 volt wires and cables in three separate categories-single conducto~s. conduits or air.&00 Volts) The following brief descriptions of insulated aluminum for use on circuits not exceeding 600 volts. covered conductors are installed on insulators and other wise treated and respected as bare conductor. Spacer Cable Conductors described above as tree wires may be used as spacer cables by utilities though spacer cable does not require the heavy covering of abrasion-resistant compound used in tree wires.Volt Cables Aluminum conductors of this classification are em ployed in the circuits in buildings.8 AWG to 2000 kcmil. minimizing outages resulting from occasional tree contacts due to weather conditions. considerably thicker coverings. while utility companies are generally governed by the National Electrical Safety Code. and with or without metallic or non-metallic outer sheaths or armor. Testing is designed only 10 establish physical properties and continuity of coverings. where a's building wire products are manufactured to comply with specifications of testing laboratories such as Underwriters Laboratories. Plastic or ceramic spacers with provision for attachment to a messenger support maintain the conductors in a fixed relationship. distribution. The specification generally referenced for covered line wire is ANSI CS. in contrast to insulated con ductors. or as components of multiple-conductor cables. For the reader's convenience. reference should be made to the NEC and Chapter 10 of this book. type of raceway. (Covered in underground section. see succeeding chapters. The insulation required is governed by the specifiC application and will include both temperature and mois ture conditions. . Conductors used in line wire (as with tree and spacer cable) meet the relative ASTM specifications for the conductors used. spacers are usually placed 30 to 40 feet apart. THWN. allowing close spacings without shorts or flashovers. RHW. Conductors are required to be either direct buried in earth. Depending on conductor size and length of run. too. with non-conducting spacers to reduce the amount of space and hardware needed. are installed on insulators and treated as bare conductors. THHN. but designed with. The cover ings help reduce faults due to weather and wind where objects may comact the lines. Sin&le Conductors !O to 600 Vo/tsl Single conductors of standard insulation types in most cases must meet the requirements of the National Elec trical Code. Conductors of the first type are generally specified bv utilities to comply with an industry specification. Used by utilities as open secondary distribution cable. Ampacity ratings for a given cable of a particular voltage and construction will vary with type of insulation and installation conditions. 35. These conductors. Depending upon design. and covering is applied for weatherability. The conductors range from NO. and 2) those better known as premise-type wiring or building wire. THW. or armor.covered and insulated wire and cable Covered conductors. Tree wire and spacer cable are also in the same category as covered line wire. TW. page 74). alloy 6201. and feeder cables . except as permitted in specific NEC Articles. ACAR or ACSR. with thicker covering than line wires. trays. and other low-voltage distribution systems for which the previously described covered cables are not suitable. For more information on selection and use. are to provide a general overall review. Occasion ally high density polyethylene and gray coverings are applied. and mulltple-conductor cables surrounded by overall jacket. and installation location. yard. single conductors in unjacketed assemblies. with various kinds of insulation. In conductor selection. and XHHW. • Use and application of building wire is usually governed by NEC. c~:mductors 7·2 Cables of this category are of two types: I) conductors predominantly used by utility companies. are used to permit utility companies' secondary line installation without extensive tree trimming. Covered Aluminum line Wires and Cables Co"ered Line Wires Covered aluminum conductors are generally ali-alu minum 1350. or installed in conduits or other recognized raceways. or the lines come into close proximity with one another. Single 6OO-volt aluminum conductors are also widely used as underground service entrance. structures. Conductor cover ings have no associated voltage rating and are usually black polyethylene or crosslinked polyethylene. Insulated Conductors and Cables (0. sheath. The minimum requirements for building wire applications are given in the NEC. Conductors manufactured to comply with the require ments of testing laboratories such as UL include types RHH. Aluminum Power and Lighting Insulated WO. Tree Wire These conductors. are used mostly by the utility industry under conditions where insulation is not required. eIther as single conductors. they may be installed in duct. Spacer cables are installed. 10-4. or by a smooth or corrugated tube. are cabled together to make a round construction. SER and SEU cables are available in sizes No. Factory assemblies in sizes through 4/0 AWO are generally available. or Type SE-Style R (SER).) Service drop conductors are also used by utility companies and other users to power security light systems or distribute power overhead from one structure to another. and covered with a jacket. Metal-clad cable principally is used in lieu of cable in conduit and where significant labor savings. or three insulated phase conductors cabled around a bare neutral messenger. Aluminum armor is also particularly resistant to corrosion in many industrial atmospheres and is significantly lighter in weight. and one bare grounding conductor. trays. continuous. are rated at 600 volts phase-to-phase. The three-conductor type includes two insulated phase wires and an insulated grounded conductor that serves as the circuit neutral as well as an equipment grounding wire (where codes permit dual use). Reverse Twist Secondary Cables (RTS) RTS cable meets the same ICEA specifications for 600 volt phase-to-phase conductors as PAC (above). Its basic design of reverse-lay twisting of phase conductors about the neutral messenger builds in additional length and eases separation of phase conductors for "T" taps. such as in apartment buildings. Metal-clad cables are installed in racks. Aluminum Service-Entrance Cables (6()()-vo/t) The most commonly used service-entrance cables are designated Type SE-Style U (SEU). or baskets. 10-5. or are suspended from messengers. closely fitting tube of aluminum. Many UL-listed aluminum accessories are available for use with Type SE circuits. mechanical protection of the conductors. with two or three insu lated phase conductors assembled with a bare neutral messenger. provision for rearrangement. The four-conductor type includes two insulated phase wires. the characteristic use of aluminum armor is favorable in ampacity and voltage drop comparisons. manufactured to rCEA specifications. (See NEC Article 230.review of types and applicatiOns Six-hundred-volt aluminum-armored cables are also available in single conductor constructions and are dis cussed on page 7-4. The assembly is covered by a metallic armor of interlocking tape. Assemblies consist of one. etc. The conductors are spirally assembled. 7·3 . one insulated con ductor. Multiple Conductor Power Cables (0-600 Volts) Aluminum Interlocked or Seamless Armored Cables Metal-clad cable designated Type MC by the NEC (Article 334) consists ofone or more insulated conductors. Assemblies are either three. Both styles are recognized for service entrance circuits and also for sub-service and branch circuits within a building. Service drop cable is installed by and is generally within the jurisdiction of the utility company. where it is con nected to the service entrance conductors. and to equipment for which a three-wire service is required. Fig. Service Drop Cables Service drop cables. A layer of moisture-seal tape covers the concentric wrap. A protective thermosetting or thermospJastic outer covering may be added where corrosive or other condi tions warrant its use or for direct buried application. Because these cables are also approved for certain interior circuits. 8 AWO through 4/0 AWG. Fig. . are manufactured to meet the applicable requirements of ICEA specifications for neutral-supported service drop cables. plexed under a binder tape. Because of this. laundry-room appliances. weighing about one-third the weight of steel. one or two insulated conductors form the base around which bare aluminum strands are concentrically wrapped to make the uninsulated neutral conductor. (See also NEC Article 334) Aerial table Assemblies (0 to 600 Volts! Messenger-supported aerial cables may be field as sembled from single conductors. flexibility and installation. NEC-recognized for single-unit dwelling services through 200 amperes. they are used where many distribution panels and branch meters are connected to a single service entrance. In SEU cables. and small available space are factors. RHWor XHHW. sometimes referred to as multi plexed cable. and the entire assembly is protected by an overall jacket of polyvinyl chloride. thereby separating the circuit neutral from the equipment ground ing wire. troughs. neutral and phase. two. Parallel Aerial Cables (PAC) These cables. such as electric ranges. wrapped with moisture-seal tape. Phase conduc tors are commonly insulated with crosslinked poly ethylene or polyethylene. 6 through 1000 kcmi!.or four-conductor. They are used on circuits not exceeding 600 volts phase-to-phase to supply power from the utility source to the user's attachment point. The Type SE-Style SER cable differs from the oval style SEU in that all conductors. These conductors are used to supply power to a limited number of customers and provide for "Tn-type taps. Conductors used in service entrance cable are generally RHH. Type MC cable is generally available in sizes Nos. Aluminum sheathed cable consists of one or more insulated conductors enclosed in an imper vious. Aluminum armOr is nonmagnetic and thus does not add to the inductive reactance of the conductor as does galvanized steel. and covered overall with bare round or flat-ribbon copper wires. However. 2. NEC·designated Type MV (~1edium Voltage). plain Or corrugated. 10-12. Fig. '-'hile USE with an outer jacket may be installed as Type SE cable. 3. 4/0 A WG are used. 10-9C. semi·conducting strand shield. also applies to cables up to and including 2 kV. except for insulation thickness. desig· nated Type USE for service emrance and Type UF for underground feeders are available for this service. or as protected by interlocked or continuous armor. narrowing the margin between URD and conventional overhead con struction. as further noted in Chapter 10. Power Cables fabove 600 volts) The general description of cables rated 600 volts with rubber or thermoplastic insulation on page 10·5. The metallic shield may be used as part of a relaying circuit and occasionally as a neutral. The most commonly used insulated aluminum medium· voltage cables are in . 10·16. Conductors used in high voltage cable construction are generally Class B concentric or compressed stranded. All are suitable for direct earth burial to complete the circuit from the utility source to the customer's meter. Primary URD cable is generally available in solid dielectric design with extruded insulation shielding. The . Single conductors and multiple·conductor cables without jackets must be protected by conduit upon emerging from the earth.. Fig. These cables also are available preassembled in plastic pipe. or duct·bank. Chapter 8 of this book details types of insulation used in high and medium voltage cable constructions.th a solid or stranded insulated reduced·neutral conductor. Insulation and conductor shielding are used to create a uniform voltage gradient within the insulation about the conductor. However. for cables of the most·used types in the range 2001 V to 5 kV. A single insulated reduced·neutral conductor is centered between insulated phase conductors. A metallic shield. 115 kV and 138 k V (and all intermediate and lower voltages) has been in successful use for many years. and semi·conducting insulation shield) over which a bare concentric neutral is helically applied. . a layer of semi·conducting material known as conductor shielding is applied directly over the conductor and in contact with the inner surface of the insulation. which is to be suitably grounded. Both single conductors and preassembled cables.Type UF cable is similar to Type NMC cable. insula· tion. applied helically and of such size that they comprise the equivalent of a reduced neutral. is in Chapter 8. Fig. though some solid conductorS in the size range of ~o. two·or three-conductor cable. Insulated Conduct0!5-Above (GOO Volts) Although bare aluminum conductors are extensively used for transmission and distribution circuits at all voltages. and multiple oonductor with an outer jacket. 10·18. The most frequently used arrangement is made up of twO separately· insulated aluminum phase conductors twisted wi. Primary URD Cables for Underground Residential Distribution (5k V to 35 k V) In general. Special reference to their use as preassembled aerial cable. an additional insulation shield of semi· conducting material is applied directly over and in contact with the OUler surface of the insulation. 10·15 and 10-17. cabled conductors attached to a messenger. See Fig.covered ond insulated wire and cable Aluminum Cables For Underground Installation (GOO·Voll) Insulated 600·volt aluminum cables are widely used for both secondary distribution feeders and service emrance conductors. Underground feeders . Fig. 1O·9D. Two separately insulated aluminum phase con· ductors are laid parallel. A thin web of insulation is left between the conduclOrs The web is easily separated for making «rmimi! con· nections. The design is comprised of a standard medium voltage type cable (conductor. the two*conduclor. The insulation is extruded over the three conductors simultaneously. Figs.1ultiple·conductor 600·volt underground cable can· "ructions come in several forms. UF is available in single. Fig. The described customary shielding practice for the various voltages are subject to exceptions as described in NEC and lCEA standards. ]()"9B. with or without grounding. and it aids in handling and stringing.Type USE cables are available as single conductor. Among the most '~()mmon: I. but has additional jacket thickness making it suitable for direct burial. multiple conductor. Copper wires are used for the spiraled neutral bare conductors. 2 through No. installation in conduit as well as direct burial of insulated aluminum conductOr at 69 kV. and is approved for installation as under· ground feeders on circuits not exceeding 600 volts. For most cable rated 5 kV and higher. for duct installation. Cable constructions are sometimes tailored for specific use and the basic design modified to meet particular requirements. concemfJi>neutral rype is standard for primary URD cable..the range of 5 kV through 35 kV (phase·to·phase) for installation in air. Fig. 1O·9E. insulated aluminum conductOrs have nOt yet come into general use at transmission voltages 230 k V 7·4 and above. is always applied over a semi·conducting insulation shield. Underground services . as two-conductor or three-conductor cables. Developments by the aluminum industry of such spe· cialized conductors as those described have greatly aided the conversion to underground residential distribution by reducing conductor and installation costs.. in parallel or "ribbon" configuration. is a safety feature that facilitates removal of power from the circuit if the other grounding conductors become broken. 10-13. Preassembled Aerial Cables (to 35 k V) Preassembled self-supporting aerial aluminum COn ductors for primary distribution are available for voltage ratings through 35 kV. Aluminum Mine Power Cables The circuits in mines usually must be frequently re located as mining progresses. 10 kV and 15 kV. as required across a single fixture. and ol. 6 or No. wire-armored cables are used. Imerlocked-Armor Cables Cables of this class installed on racks or cable trays provide ease of installation and re~routing of circuits where necessary. used as aerial cable conductors. For long drops. are available with rubber or cross-linked polyethylene insulation as single or 3-conductor aluminum phase cable which includes three copper grounding conductors (one of which may be insulated). In contrast to the interlocking design. direc! ear:h burial. Today this design basically applies to cables with steel armor. 10-14. or dropped vertically through a bore hole. Individual phases are cabled together and bound to a supporting messenger. Armored-multiple conductor cables are available utiliz ing shielded conductors as described above. Three conductor cables of this type also are supplied with an armored outer covering of steel wires to resist abrasion when the cables are dragged over the ground. The cables may be damped without insulators to mine walls. Mine power cables.en as components in armored cable. Aluminum Insulated Conductors for Special Conditions In addition to the applications previously described. Cables with aluminum armor are now generally of corrugated design. 8 kV. usually galvanized steel. or between buildings where the cost of underground duct installation cannot be justified. because they differ in certain re spects from the usual permanently installed circuits for power and lighting. These cables are designed for aerial installation on poles. In general. and for direct burial. the corrugated armor seals the constructions from the ingress of moisture. where metallic strips were shaped and spirally applied about the cable in an interlocking design. 7-5 . Aluminum Pole-and-Bracket Cables for Series Slreet UghlinR Cables for this service are usually single-conductor solid. if used as a ground-check. with one-third neutrals common for larger sizes. Cables are available for installations overhead. in underground ducts or conduit. The insulated ground conductor. Shielded and jacketed conductors as described above are used in these constructions. there are other uses Oi' aluminum conductors that require speCial considera[ion. Medium. and are suitable for installation in underground duct. Aluminum single and preassembled 3-conductor properly jacketed cables are excellent for this service because they provide needed flexibility. Slzed to match the conductance of the phase conductor. though the individual conductors may be insulated only to 600 volts.Voltage Shielded Single-Conductor Power Cables (5k V to 35 k V) Cables of this ciass are used principally for relatively high-voltage power distribution. Some con~ structions are designed with grounding conductors placed in the cable interstices. for applications such as sub marine and bore-hole cables. Preassembled aluminum self. or where aerial space and safety does not permit bare overhead conductors. Fig. S kV. The overall jacket of this construction provides protec!ion for the metallic shielding and makes the cable suitable for a wide variety 01 uses. and the exterior jackets resist abrasion while being moved about. lackets of polyethylene or polyvinyl-chloride applied over both types of armor provide prOiection against corrosive environments and seal the interlocking type armor. The conductor size for aluminum usually is No. with individual-conductor and belt insulations suita ble for operation up to 9000 volts open circuit to ground. Aluminum strip is applied longitu dinally about the cable.review of types and applications helically applied concentric neutral is generally composed of coated or uncoated copper strip or wires. These con ductors are cabled together with the necessary components to construct a round cable over which is applied a moisrure barrier separator and the armor. light weight for ease of handling. The runs often are in cramped locations and also the supply often is through a vertical bored hole. Cable designs through 4/0 AWG often include a neutral. as previously described. suitable for permanent or temporary installations. Cables of this class are generally available in 5 kV through 15 kV ratings and may have either aluminum or steel armor. or cables in vertical risers where longitudinal stress is a factor. or where congestion overhead or underground prohibits conventional installations. Mechanical protection can also be provided by the use of concentrically applied round-wire armor. are often used for general supply on mining properties. towers. 8 A WG either as single conductor or parallel two conductor type. Fig. Cables may be preassembled in the factory or field spun using a binder applicator. for 600 V. run along the ground. continuously welded and corru gated to provide flexibility.supporting high-voltage aerial cables. cable armor in previous years was of the interlocked type. . hard drawn. also aids flexibility. often many within a single sheath. and river or tide currents. two. Special Applications Cables These cables usually consist of comparatively small conductors. jute bedding. sharp rocks. six times overall diameter for multi-conductor cables rated 5 kV and less. electrode holders (of welding cable).6 A WG to 4/0 for 6OO-volt three~ or four conductors (and into the kcmi! sizes for certain types). mining machinery. Also available are shielded portable cables to 5000 volts.covered and insulated wire and cable A luminum Portable Cables This highly specialized classification of electric conduc tors has heretofore mostly been available in copper. as used for some designs. These cables usually consist of three thermosetting or thermo plastic insulated conductors cabled together and protected by a tape. and galvanized-steel·wire armor. in addition to the welding-equipment use mentioned.and multi-conductor cables over 5 kY. and in and around shipyards. all strands spiral in the same direction regardless of which layer they are a pan. Special extra-flexi· ble light-weight portable single cables are also available for use with welding equipment. or fully annealed aluminum. but more recently aluminum portables have become available in the heavy-duty sizes No. recent years have seen increased use of alu· minum conductors in communications cables and auto· motive wiring harnesses. Insulated molded fittings and couplings are available for many of the sizes so that quick connections can be made to terminals. Flexibility is obtained by using Types G. magnetic hoists. The unidirectional method of stranding. However. that is. are those for locomotive reel equipment. 7·6 Aluminum Submarine Cables Submarine cables have moisture-resisting insulation and sometimes are protected by lead sheaths. or I stranding of '4-hard. The insulation and jackets are of materials that will withstand rough abuse when the cable is bent or dragged. where weight is an important factor. and between cable sections. plug-in power drops from busways. Aluminum conductor manufacturers should be consulted for further information On this subject. with single. dredges. Bending radii of eight times overall diameter are generally accepted for single. service. As current carrying requirements usually are small. depending on require ments. little economic advantage accrues from the use of aluminum. Some of the uses of aluminum portable cables. Heavy mechani· cal protection is required to prevent damage from ship anchors. motor leads. H. brittleness. emergency overload. resistance to abrasion. Assembly tape and fillers 7. that is. and sheaths than one for underground burial. 3. or arR'J. crushing. The strand and insulation shielding is normally an ex· truded layer of semi-conducting material. Assembly tape and fillers 4. and alkalies. Requirements in this category depend con siderably on voltage. This chapter provides summary data and the reader is advised to consult the referenced standards for further detail. Although details of cable construction and materials are supplied later in this chapter. the following represents a customary sequence of component layers if the insulation is of thermosetting or thermoplastic materials: Low-Voltage 6O()-2()()() V 1. For shielded cable. Strand shielding if required) 1. arc resistance. Jacket. Phase identij'lCtIti01l on non-shielded 600-5000 V cables is accomplished by a number of means. suulight. shields. Typical 3-Conductor Cable Assemblies The arrangement of layers of insulating and other ma~ terials around the bare conductors depends on voltage and the service application of the cable. com pressive. and short-circuit conductor temperatures. 8·1 . Conductor 2. Assembly tape and fillers 5. sheath. Mechanical: Toughness and flexibility. and oth· ers. Electrical: Dielectric constant. moisture absorption. Chemical: Stability of materials on exposure to oils. sheath. Bame. Inc. insulation power factor. the insulation is covered with an extruded semi-conducting layer. Jacket. and Insulated Cable Engineers Association (ICEA). Subject to such differences. tracking susceptibility. Phase-coded 3. ozone. the following briefly de scribes some of the items mentioned in the above tabula tion of cable components.. A different arrangement also is re quired in a cable for series lighting circuits. and others depending on application con ditions.or The directional control of static lines of force brought about by suitable strand and insulation shielding is de picted in Fig. charg ing current. jackets. Phase. Metallic shielding is normally composed of pure zinc or copper tape. a cable for aerial or in-condult installation may have a diflerent ar rangement of shields. tensile. or armor 4. Thermal: Softening or flow temperature. Underwriters Laboratories. including color coding and printing on the surface of the insulation. and moisture. Insulation shield~ ing-phase identification 5.Section III Covered and Insulated Wire and Cable Chapter 8 Insulation and Related Cable Components This chapter describes in further detail the insulation and coverings mentioned previously and also describes the jackets. 5. compatibility with ambient.:oded insulation 3. insulation resistance (ac and I-minute de). Conductor 2. operating. Insulation I. An explanation of some of the dielec tric terms is in Appendix 8A. Standards are specifications for cable insulation and coverings are developed and set forth in the publications of ASTM. acids. Jacket. expansion and contraction. 2. Conductor insulation 4. 5 k V and above. sheath. Code Requirements: Installation of cable in accor· dance with NEe and under the jurisdiction of separate electrical inspection authorities usually requires cable labeled by Underwriters Laboratories (UL). ozone resistance. metallic braid or metal wire shields. Strand shielding 3. (UL). and impact strengths. 4. 8-1. Uniformity of potential gradient is influenced by shielding. sheaths. and other materials used in the assembly of a cable. Selection of insulating and other materials that sur round the conductors is based on a number of performance factors: 1. MetaUic insulation shielding 6. or armor Non-Shielded 2001·5()()() V Shielded OVer S()()() V (01' as low as 3001 V 2. See page 8·10. Coverings for Uninsulated Conductors The distinction between insulated conductors and unin sulated covered conductors was mentioned in Chapter 7. except under special conditions. The diagrams show the condition at the instant when voltage is zero in one of the conductors of a three-phase circuil. however. Related to these. Various methods ofcable strandingfor reducing diameter and minimizing skin effect. assuming the latter is grounded. Similarly. 8-2. Additional layers are added in the same concentric manner. Ie) (d) (e) (e) Compact 120-deg sector for 3-conductor cable (dj Hollow or fibrous core for reducing skin effect (e) Segmental single conductor for reducing skin effect (Thin insulation is provided between segmentsj . (a) Compact round (b) Non-compact 120-deg sector for 3-conductor cable 8·2 The compacting of stranded conductors. high molecular weight polyethylene and polyvinyl chloride. (0) (b) Fig. used for decades have been superseded for power and lighting cables by thin extruded coverings of plastic-type materials. Cable has both strand and Insulation shielding. In this arrangement the individual uninsulated conductor is a concentric stranded group in itself. Diagrams that show direction of potential "lines of force" that extend radially from conductors within a grounded sheath: A. and hence used mostly for jackets to protect the insulation from en vironmental conditions. Cable has neither strand nor insula tion shielding. Some of these designs in round or sector form are shown by Fig. is increas ing in use because it provides the flexibility of a stranded conductor and the conductors approach the diameter of a s"lid conductor. characteristics of which are covered in Table 8-1. for the large sizes extra flexibility is ob tained by rope-concentric stranding. The cable with a COre of fibrous material (item d) Or the segmental cable (item e) provide reduced skin effect as compared with one of equal resistance of conventional construction. Insulating Materials and Performance By far the most used materials for insulating aluminum conductors are those of the extruded dielectric type. B.covered and insulated wire and cable Fig. are little used commercially. The item d and item e cables. Conductors for Insulated Cables As described in Chapter 7. the principal component being one of several materials such as ethylene-propylene rubber. where it was stated that braided weather-resistant cover ings. 8-1. A brief description of these materials appears later in this chapter. cross-linked polyethylene. are neoprene and special polyvinyl-chloride and polyethylene compounds. if the individual con ductor is a bunch stranded group of small wires (the wires placed without regard to any geometric arrangement) the conductor is said to have rope-bunch stranding. Thus. 8-2. and six of these groups around one will constitute an overall body of seven groups of seven strands each. made by com pressing the strands together to decrease voids. combination strandings are more likely to be used for insulated cables than in bare conductors. but of less insulating quality. % Q Dielectric Constant.13 Specific Grav ity 1400 300 min. psi Elongation %. % increase Good Very low Good 0. ANSI and UL The listed values for extruded coverings apply to the grades of mater:.35 (immersed) 0. volts (#6 soLI Resistance to: Age Crack ing Sunlight Ozone Acid. Cold Bend Abrasion Resistance Ice Forming Tendency Water Absorption. 8-3 and 8-4 for grades of similar materials used for insulation.in. 25°C.92 1. Tens!!e Strength. See Tables 8~2. Min.! used for' coverings.0 (immersed) 1017 (immersed) 10 16 (immersed) 24000 (immersedl 22000 (immersed) Excellent Good Unaffected Excellent Excerlent Excellent low Power Factor. {immersed} 2. 0. 8·3 . Alkalies Alcohol Gasoline Excellent Excellent Unaffected Excellent Excellent Excellent Oil Fair~swells slowly Poor-softens slowly Good Good (20°C) Salt Solut'on Excellent Excellent Test MethOds are from ASTM. 60 Hz 20°C. 25 C InsuL ResistIvity. 121'C _80°C -55'C Heat Distortion Brittle Temp.insulation and related cable components TABLE 8-1 Some Typical Comparison Data on Extruded Materials for Non-Voltage-Rated Covered Conductors Extruded Polyethylene Black Covering Cross-Linked Polyethylene Covering 0. 2600 300 ".08 (immersed} 5.8 0..2-0. ohm-em Breakdown strength.45 max.2 max. End of Period 7 Days 98% EPM or EPDMu %% Butyl 95% • Cross-linked polyethylene XLPE* .ng compound by bringing about a cross-linking of components after the material in its thermoplastic state has been extruded around the conductor.030%). The other thermosetting rubber-like compounds if properly compounded also show high retention of initial hardness at high operating tem peratures. tions in some respects far exceed the requirements of established standards. However. Thermoplastic compounds (polyvinyl chloride and polyethylenes . ihe test usually can be extended to 24 hours. a surface may be undesirable. The higher the operating temperature the greater the ampacity. Inc. reinforcing agents ihat improve strength. And from the above-mentioned values for air and oxygen aging and for retention of elongation it is evident that modem insula.8-3 and 8-4. The permissible temperature at which an insulated con ductor can operate for the expected life of ihe cable with out impairment of insulation Quality determines the am pacity (current-carrying capacity) of the conductor. stead are supplied on a performance specification. both as to permissible operating temperature and oiher electrical constants." and the sequence of letters of the NECType (such as RHW. etc. The effect on the elongation of an insulation (or jacket) under stress is also an acceptable measure of heat resist ance.) provides an approximate description of insulation performance. (UL). that is. or even 48 hours.. upon exposure to heat under suitable conditions a chemical reaction occurs and ihe compound becomes vulcanized into a tough.84% a% 77% (EPR) Further evidence of improvements in insulation perfor mance in these and other electrical and mechanical proper ties is evident from Tables 8-2. (ICEA). High operating temperatures imply high losses in the cable and despite the ability of an insulation to withstand certain temperature levels without losing its insulating properties.025-0. . but in. At this concentration.. The performance of a synthetic rubber or a sitnilar plastic insulation depends not only on ihe largest proportionate component of the compound (from which ihe insulation sometimes is named) but also on its formulation wiih modifying ingredients and on ihe meihod of manufacture. THWN. RHH. of the initial elongation must be retained after 7 days of exposure. and Insulated Cable Eugineers Assn. The air Oven test at 121°C provides a relatively quick method of grading insulation materials for use at high conductor temperatures or in hot-spot areas. ihey would age from exposure to oxygen in air. and abrasion resistance. Alihough polyethylene is classed as a thermo plastic. typically as follows: Air-oven aging at 121 cc Percent of Initial Elongation at Rupture.. accelerators. the earlier materials would fail in minutes... accord. insulations are not supplied to meet a component-and-process specification. Underwriters' Laboratories. ing to standards and meihod of testing of American So ciety for Testing and Materials (ASTM).010. representative modem insulations for high. The added ingredients are broadly grouped as vulcanizing agents or curatives. that is.0. it was originally called "GRS" (Government Rub ber-Styrene). * EthyJene propylene rubber 14 Days 95% 21 Days 91 % ~% ~% 90% 86% 28 Days . and was first made in government-owned plants. Although ihe official test time still remains at ihree hours. and plasti cizers ihat soften the compounds and provide control of flexibility. The early insulations for high-voltage cables also were required to pass an ozone test at 0. Wiih the advent of modem insulations this concentration was doubled (0. New improvements in manufacturing have resulted in compounds that are even more desirable in many re. Page 8-12 explains the usual meaning 0 f these NEC Type letters. in its cross-linked form it retains about 90% of its unaged property even at 121°C. comparisons of surface hardness at various temperatures may be misleading because the hard ness usually can be controlled by additives. The performance of thermosetting and thermoplastic insulations for power cables has improved remarkably in recent years. care must be exercised to determine economic conductor sizes to balance first cost and operating costs during the life of the installation. Thermosetting Insulating Materials Styrene-Butadiene Synthetic Rubber (SBR) This insulating compound was introduced after World War II. if the standards established for the earlier 60°C insulations are compared with those of later types for 75°C and up. Al though the ICEA 121·C air-oven test specifies that a minitnum of 75~. but also as to increase of useful life. In com parison.. and too hard . without failure. The National Electrical Code (NEC) refers to various kinds of insulation as "types. fillers such as carbon black. tear.. clay or talc. antioxidents that improve aging quality. Rubber compounds (natural and synthetic) are thermosetting. that speed the reaction.015% concentration for three hours.not cross-linked) soften upon exposure to heat. As ihe exact proportions of each of ihese ingredients and the conditions of preparation and mixing may differ among cable manufacturers. it may be converted to a ihermosett. modem insulations are compounded from ma terials ihat essentially are insensitive to oxygen. whereas polyethylene in its typical thermoplastic form has melted at approximately 105"C. elastic condition.voltage conductors actually show far better per 8·4 formance. Early insulations were oxygen-sensitive. Thus.covered and insulated wire and cable These materials are classified broadly as thermoplastic or thermosetting. The usual availability of cables with this insulation is No. Hence a flame-retardant jacket must be used unless this special compounding is used. oil and abra sion. there are applications. As usually compounded it has excellent flexibility. Similarly. XHHW) This insulation. Its high quali!y is evidenced by ICEA listings per Table 8-4 for wet and dry locations at 90 e C for normal operation. Butyl rubber has better electrical properties and greater heat and moisture resistance than either SBR or natural rubber. 8-5 . Type AVA has an asbestos-braid outer covering. SBR has good dielectric properties and relatively high dielectric strength. RHH. Asbestos Insulations (SA. and by change of modifying components they can be adapted to various conditions. The SBR compounds are suitable for many of the NEC Code rubber insulations of the RH. and is of ozone-resisting type. SBR can be compounded for high ozone resistance. and torsional stiffness requirements are severe. or 25 kV for ungrounded neutral (133"70 insulation level). hence it principally came into use for insulation at the higher volt ages. and has little resistance to flame propagation. place it in the 80°C class and as sultable for 15 kV (28 kV. grounded neutral) with ungrounded neutral. Fluorinated Ethylene Propylene Rubber (FEP) Commercially this insulation is sometimes referred to as Teflon. and particularly where a flexible jacket is required as on certain portable cables. The Type SA power cable is NEC listed to 2000 kcmil with an outer covering of asbestos or glass braid OVer silicone-rubber insulation. an oil-resistant jacket can be applied. listed in NEC as Type XHHW and also suitable for underground gorvice entrance (USE). NEe lists this insula tion as suitable for Type RHW conductors.insulation and related cable components spects than natural-rubber base insulation. brittleness. Type AVL has a lead sheath. The air-aging and elongation tests (see page 8-4) show that this insulation liberally exceeds ICEA miulmum requirements. Though normally used in the 0-600 volts range. Industry listS. Butyl Synthetic Rubber This compound is a copolymer of isoprene and iso butylene.2 AWG to 1000 kemil. special equipment is required for the final processing of XLPE. mostly for small size conductors. the manufacturer should be consulted. mostly in tbe smaller sizes up to No. However. References to "synthetic rubber" in Table 8-2 imply the use of SBR. The insulation is rCEA listed to 1000 kcmil for 125°C. If desired for chemical environments. SBR also is much used in jacket com pounds. A VL) Aluminum conductor is hetter suited for high-tempera ture operation than most metals because its oxide coating does not become thicker as a result of repeated applications of heat. It has excellent ozone-resistance. Ethylene-Propylene Rubber (EPR) This ozone-resisting rubber insulation is recognized as suitable for up to 35 kV at 90°C. a semi-organic polymer. The insulation is provided by a layer of varnished cloth between inner and outer walls of felted asbestos impregnated with a satu rant. AElC-5 recognizes higher voltages and considerable 46 kV cable is in service and smaller quantities of 69 and 115 kV cable have been furnished. The insulation consists substantially of ethylene-propylene copolymer (EPM) or ethylene-propylene terpolymer (EPDM). The lCEA listing of ozone-resisting butyl rubber specifies 85'C for 15 kV and 80°C for 28 kV (grounded neutral). though this property can be improved by special compounding. The insulation compound is heat cured fluorosilicon rubber. strength. in which neoprene will be used as insula tion because of its ability to withstand flame. Neoprene Synthetic Rubber Neoprene is described as a Jackel (page 8-9) because its relatively poor insulating quality limits its use as insula tion. and is inherently resistant to ozone. it wiD no longer soften at 100'C. thereby converting it to a thermosetting compound. Type AVA is used in dry locations and AVL where the cable may be submerged or subjected to excessive condenSl!tion. if desired. but in addition has high heat resistance. Types AVA and AVL contaln no rubber. however. Because of these properties it is possible to produce an ozone-resistant Insulation from butyl rub ber of a given thickness that is superior to that of ozone resistant SBR. Whne present lCEA standards only cover XLPE thru 35 kV. and heat-aging within its 90°C dry and 75°C wet ratings. and resistance to tear and abrasion. hence made suitable for cables to 15 kV.2 AWG for which it is UL approved. The insulation is principally used for medium-voltage cables. Cross-Linked Polyethylene Insulation (XLPE. from 75°C wet or dry to low-temperature (_55°C) service where cold-bend. and RHW types. A V A. The com pound is obtained by introdUCing what is known as a cross linking agent to low-density thermoplastic polyethylene. It has limited resistance to oils and hydrocarbon fuels. The resulting compound still has the original excellent characteristics of polyethylene. Because the cross-linking treatment is done at a higher temperature than that used for thermosetting most rubber compounds. it has UL ap proval and is recognized under the RHH -RHW type. The standard also lists it as suitable for l30'C for emergency-overload conditions and 250°C for short circuit conditions. is classi fied as thermosetting although its basic material is poly ethylene' which in usual form is thermoplastic. It is much used for control wiring. Sometimes it is better to use a thick coating of neoprene as an off$et to its poor insulating quality so as to obtain its other advantages without having to cover the conductor first with a high-quality insulation and follow it with a jacket of neoprene. Q ::..015 0..ler over the insulation. Corona level. min.J "1< 'IS used in the rollowing lorrnutiJ tor irHulntion fesistnnce: 1(l910 (Did). 1 to 14 days '8. The publications from which this lable is an ab-s. Power factor __ '1tHII_kV "- S).. hence this t.0 1. Q.ul. min.010. 26.. 3.0 20." NOTE:. 700 300 Rubber 75 75 75 2 2 ? 2 2 2 700 300 700 300 1500 400 700 300 2 24. 40 80 m .11 S3.. 8kV2BkV 8kV15kV 450 250 15kV2BkV 15kV15kV 2 2 5 600 700 800 3\)0 300 250 5 ~ ~.0 10.0 4.lisle.lt uw al t(!<I~t to35 kV. 25.025-0. 50 50 2000 2000 2000 1O.$ign requinK U5e of the complete speci![Ciiltions.(tIra cOlltaill el(Ceptioll$ ~riiilliot\$ of certain of Ihe values that af...0 10. 4000 10 a 3» 1. at rIlax.ler under thE! in. D '"' dlamr. min. R~n'lbjes Ul. wherr.16 are ~ubjecte-d 10 ~rl air-prenure te~1 ill~tcad '(..:ble should b& med only for {jeneral reference.-Ql(ygE!n.025·{LOJO (pereend rather thall "p&fCerlt of unll\le value. 127·20 127-20 50 .orp don.0 15. min. with url~rounded neutral 8..0 50 50 70-9S aO 168 w 80-168 1'17-20 127-20 50 00 aO-168 50 50 aO-168 70_1S8 4 400** 200"~ 70-48 100·1Sfl GO 60 air pressure 12/-40 1:>1·168 50 50 75 50 50 400"~ 50 50 76 200.0 3. Consult sp~~cificlltion5 i:llso for explar1atior1 of the villiou!\ items. unaged valun Tensile S!.0 5. 16.. Temp wet not excooding 0 C Max kV ph<l~e·W1Jh~w 6.0 20.' 21.0 O.0% abffile 35% ijbove 5kV bkV 0.0 28 kV 21. $3. 1tems !) and 7: fnsutiJtion~ specified for 15 kV Me in extensivtl comrfl6'rr:i. Aging requirements (air f. 9.. in. Rubber 12._kV 'Aif-Oven rest. No cracks after 3 hrs exposure 10 co"cttn!ra~ Han of not less than ~ % nor more than_% by volume Min. NEC. Insulation resi~lance Parameter K Accelerated water absorption EM60 Increase in capadyoce % max. Actual df'.14 53.0 3.and Synthetic-Rubber Insulations ~ Abstract from ICEA-NEMA Publication 8-19·81 LICEA $·19-81 Paragfllph No. (oxY(lenJ Test at ~oC for _hrs Valuas as .. 20.rar. Gravimelric method... s:uo Synthehr.0 11. mi!!lgrams/sq.(1. 2 10.15 53.15 .rtiol1.13 60 ._kV. Ten~ile strength. wilh grounded neutral "t 5 kV a115 kV $ilme.0 15. S' " ~ it Q. Oielectric constant at foom lemper31un.0 3. 11. Temp dry nN ej(cm~ding "c 5. R ~ resisti30ce in me!Johm~ for 1000 ft. The XLPE anO XLHHW in~ulatlons under90 B heal {listOft'Ofl test. IIlin. Q.hEttle Ruhhnr RH RHW Natural Synthelic Rubber Rubber 75 60 60 '" . Description 4. St~bility factor after 14 days 17. psi.0 3.0 ?BkV 21.-etlglh. " 15.b60 4000 2000 2OPOO 4000 10.su!"9 121-42 W 50 10..ln1ssure) Tast at~OC for_hrs Vf\lues as % unflged value Tensile slrenj:Jlh.0 4.12 Ali RU-RW Syn. m~x" ab!.0 1. min. "'''Oiscrete minimum IiClues for tenSilf) slrength {psi) and f~longatjon 500 H 125 B 60 air pres.5 5.0 • . S3Jl RW Syntheti(. Item 13: 'nsulalion~ 53.lnd 53. with grOlJl1ded I1Nltrnl 7. and (I = diamr.0 Ozone resistance.16 RHH SA Olone-Resisting Sy!1the~ic OzonB Rllsistl1)9 Butyl Rubber Rubber Silicone Rubhor (0 1000 Reml! "0 85 80 80 90 125 125 g Q.11 53. Ol()ne-Re~isting Natural or Syntfll!tic Ruhbnr 75 75 70 70 53. 2. 13. Specifications tor Natural. ElongatiOn. 710 14 days 19.030 4.0 200·16B" 60 75 65 21. Elongation. Thr.lply under speci~1 condition<.0 11.prt~sure teU.TABLE 8-2 00 • 0 n o ~ .. ElongatiOIl % ~t fUl)tUW.0 5.0 20. Aging requirements.0 1.0 4. absorption.8 Polyvinyl Chloride 60C Polyvinyl Chloride 75C S3.6 35. 15. Elongation %. 2. kV_kV 10. min. Temp wet not exceeding °c 60 60 75 75 Max. 19. unaged value 10. 8·7 . 1 to 14 days 7 to 14 days lB. max. Aging requirements (oil immersion) Test at °c for_hrs. min. 16.Parameter K 100-168 65 45 70-4 70-4 80 60 80 60 500 2000 50. with grounded neutral at 5 kV same. 21. in. Gravimetric method.6 0. Aging requirements (air-oven) Test at_OC for_hrs.0 4. of these materials. 20. kV phase-to-phase with grounded neutral 5. see Table 8-5" See also Note on Table 8-2.0 4 11 35 kV-26 Note: For information regarding jackelJ.0 20. min. See also AEIC-5 for thermoplastic primary cables._Max.000 Accelerated water absorption EM60 Increase in capacitance % max. Values as 0/. Values as % unaged value 13.insulation cnd related cable components TABLE 8-3 Specifications for Thermoplastic Insulations Abstract from ICEA-NEMA Standards 5-61-402 WC-5 1. Corona level. 12. at 15 kV same.0 5. Tensile strength. min. Insulation resistance . 17.0 25. (*1 The kV ratings for polyvinyl chloride insulation are increased to 1 kV for control circuits and to 5 kV for series lighting circuits. '0.7 S3. min.0 2. Tensile strength.0 10.6 0. Tensile strength. Strength and elongation aging values apply to AWG sizes No. 11. ICEA S-61-402 Paragraph No. with ungrounded neutral 6. milligrams/sq. Elongation % at rupture. pSI. Temp dry not exceeding °c S3.6 and larger. Description 3.9 Low Density Polyethylene HMWType I Classes A. min. 14. 8. Carbon-black pigmented polyethylene is not to be used On power cable rated over 5 kV.6 '0. Min. Elongation %. B or C 75 75 4.0 1500 100 2000 150 1400 350 121-168 100-48 80 50 75 75 7. 9. 0 above 5kV 4. Elongation %. 20.5 1.0 3. _same. XLPE XHHW& USE EPR Cross-Linked Thermosetting Polyethylene Cross-Linked Thermosetting Polyethylene Ozone Resisting Ethylene Propylene Rubber 90 90 90 90 90 90 35 25 2 2 35 25 800 250 1800 250 700 250 121-168 121-168 121-168 75 75 75 75 75 75 10. 14. Temp wet not exceeding °c Max kV phase-to-phase 7. ICEA S-68-516 Paragraph No.0 35 kV-26. min._max. 10.0 35 kV-26. 3.0 Min. NEC 4. with grounded neutral 8. Tensile strength.0 1. 18. Test at_DC for_hrs.0 3.Parameter K Accelerated water absorption EM60 increase in capacitance % max.0 11. Insulation resistance . kV_kV See also AEIC-5 for XLPE primary cables and AEIC-6 for EPR primary cables. Stability factor after 14 days Gravimetric method.6 3. with 21. Power factor_% at_kV 10. 1 to 14 days 16. same. Polyethylene and Ethylene-Propylene Rubber Insulations Abstract from ICEA-NEMA Standards Publications S-66-524 and S-68-516 1. Elongation % at rupture. Temp dry not exceeding °c 6. milligrams/sq. Values as % unaged value 12. max.0 3. 3. 13. Dielectric constant at room temp.0 11. Tensile strength.0% 6. 8-8 .covered and insulated wire and cable TABLE 8-4 Specifications for Cross-Linked Thermosetting. min.5 1. psi.0 Aging requirements (air-oven) 11. min. ICEA S-66-524 Paragraph No.000 20. min. with ungrounded neutral 9. Description 5. absorption.0 4.0 1.6 2.5 1.000 20. Corona Level. at 15 kV 23.0 1. Resembles UL.000 3.7 3.0% above 5kV 4. in. grounded neutral at 5 kV 22.0 2. 19. 7 to 14 days 17. 15.5 2. and flame. stabilizers. with only moderate dielectric properties. classified as polyvinyl chlorides and poly ethylenes (not cross-linked). is used as the base from which thermosetting cross linked polyethylene is made. and chemical environment.and muiti-conductor cables. Its electrical and moisture-resisting properties do not equal those of untreated PE. as is the cost of tree trimming. water. in its low density high-molecular weight grade. As r. These jackets provide toughness. for improvement in resistance to flame. It is used for jacketing single. The high-density low-molecular-weight polyethylene (black) is a compound used for insulation and cov ering on secondary line wire and service drops because of its exceilent resistance to abrasion. PVC loses from a third t{> half its hardness at 100°C and melts at about 140°C. thus. This PE grade is subject to the ill-effects of ultra violet lijiht (sunshine exposure). particularly when shielded. For this reason jackets may be of thermoplastic material. chemicals. consideration of which is beyond the scope of this book. oil will pass through the material.insulation and related cable components Thermoplastic Insulating Materials Unlike thermosetting compounds thermoplastic insula tions remain plastic regardless of temperature. fOr Type THW rated 75°C wet and dry. Neoprene lackets Neoprene is a polymer of chloroprene containing about 38 % of chlorine. although ingredients are added to the mixture for quality control and to facilitate extrusion on the conductor. and lubricants are added to meet ap plication conditions. and conse quently will soften or melt at temperatures that would not significantly affect thermosetting insulations. The properties of general-purpose neoprene and typical heavy-duty neoprene are listed in Table 8-5. direct-earth burial. Cables with PVC jackets are suitable for installation in conduit. Polyvinyl Chloride lackels The compound for polyvinyl chloride jackets closely re sembles that used for PVC-60 insulation (S3. and if specially compounded. There are numerous grades and classifications of poly ethylenes. It has comparatively high moisture ab sorption which. PVC insulating compounds are available for Type TW (NEC) insulation rated 60°C wet and dry. Poly ethylene of the same grade without cross-linking is speci fied by ICEA as suitable for insulation of conductors for rated voltages to 35 kV for up to 75°C in dry Or wet loca tions. limits its use mostly for jackets. particularly in oil or petroleum environments. Table 8-5 lists jacket properties according to ICEA. but the aging characteristics are excellent. The 2 percent black pigment prevents deterioration from ultra-violet rays of sunlight.egularly supplied. The effect of re peated rubbing of tree branches and leaves that often sur round such conductors is greatly reduced. Plasticizers. are suitable under oil conditions in the range -10°C to 90°C. or if not over 5 kV the pigment may be incorporated in the insulation. Jacket Materials As has been stated. PVC is often used for insulation and jackets. Basically it is a resin of high molecular weight polyvinyl chloride or the copolymer of vinyl chloride and vinyl acetate. Qils. resistance to moisture and oil. reSUlting in Hypawn. only a few of which are suitable for insuiations. either singly or in com bination. abrasion. Though the jacket may have moderate insulating quality its princi pal function is to protect the underlying cable components. see Table 8-3. as previously described. oil. It is generaUy resistant to mechanical abuse. fillers. Thus. General-purpose neoprene jackets are suitable for use On low-voltage cable or on high-voltage shielded cable when Ozone resistance is not required. No vulcanization is required. which can be compounded in a man ner similar to rubber. Because one side of the jacket is at ambient temperature and the other is one the outside of the insulation. The principal thermoplastic materials used for insulations have a resi nous base. Polyethylene can be treated with chloro-sulphonic acid. For some of its other physical and its electrical properties. a suitable jacket is extruded around the insulated conductor. the rated temperature for the jacket materials can be somewhat less than that of the insulation. low-molecular weight (high-density) and high molecular weight (low-density) polyethylenes are frequent ly used as jacketing material. extra protection against mechanical 8-9 . PE jackets have specific application where extreme resistance to moisture and abrasion is required. hence cable components under a neoprene jacket also must be oil resistant if that quality is required. high molecular weight low-density polyethylene. and have good low-temperature properties. trough or tray. Though oil resistant. Polyethylene lackets Black. as for mine cable. they withstand reel bending at installation temperatures of -lOoC. for THHN rated 90°C dry. which accounts for its excellent flame and oil resistance. which can be corrected by jacketing with a similar material containing not less than 2 % carbon black (PE-Black). and for higher temperatures as appliance wire. Table 8-3 lists the properties obtainable from Type I. Thermoplastic Polyvinyl Chloride (PVC) This compound is not a synthetic rubber. and overhead on messengers. Thermoplastic Polyethylene (PE) This material.7 of Table 8-3). The heavy-duty neoprene jackets may be for mulated to meet several conditions. underground ducts. often the most suitable insulation for resisting dielectric stress may not have an outer surface that is suitable for the conditions which the cable must meet in service. The desired requirements for a tape suitable for the insula tion body of a splice or terminal are as follows (I) dielec tric constant not over 3. braid. Metal-tape shields must be elec trically continuous. This process is only suit able if the insulation surface is satisfactory to meet in stallation conditions.0). Insulation shielding is sometimes used as part of a cir cuit for relaying or for locating fault position. (2) can be stretched to just short of its breaking point during application. a nominal increase of the insulation thickness over what is required for the voltage rating is regarded as the equivalent of a separate jacket. For singie-conductor cable. the shielding effect of tubular. and similar constructions. the latter having higher tensile strength and greater elongation at rupture (its tensile strength at 200 percent elongation is 500 psi).2. based on a fluxed blend of acrylonitrile-butadiene synthetic rubber and poly vinyl-chloride resin. short-circuited. wires. water. Nylon Jackets Nylon is a generic term for polyamide polymers. uUnipass" Jackets This construction is obtained merely by increasing the thickness of the insulation which is extruded by a single pass. Considera tion of such uses are beyond the scope of this book. Shielding Materials and Shielding Methods Insulation shields consist of metallic non-magnetic tape. Some of these conductors. or interlocked armor is supplemented by auxiiiary nonmetallic shielding in intimate contact with the insula tion and the metallic outer covering or sheath. the air will ionize . and they also are used for insulation at spikes and terminals. Tapes and Shielding Materials As outlined on page 8-1 the materials required to com plete a cable other than conductor. Semi-conducting and metallic tapes also are used for shielding and for splicing the shielding. No Jacket Requirements In this category are the single-conductor NEC Types TW and THW and the RHW-RHH and XHHW cross-linked polyethylene insulated cables. Polyvinyl chloride tape of lesser insulation quality (dielec tric constant up to 10. Conductor shieldS consist of conducting nonmetallic tape. require in stallation in conduit. and the auxiliary nonmetallic shield should be applied directly over the in sulating tape. Care must be taken to ensure that the tape is compatible with the components on which it is placed.covered and insulated wire and cable damage. and heat-resistant type for high temperatures. cor rugated. or on rigid supports to meet NEC requirements.or multi-conductor cables. and grounded. Nylon jackets are specified for several of the thermo plastic insulations listed in NEC. inSUlation. chemicals. if the finlt is conducting. when an insu lating tape is bonded to the insulation. and the insulation is not increased in thickness because of lack of jacket. the outer one also must be conducting. thereby improving its ability to with stand damage to insulation from mechanical abrasion and cold flow. It is made in two forms: general-pur pose and heavy duty. extruded compound. the tape is con sidered to be a part of the insulation. or flame. thereby enabling thinner insulation to be used with resulting reduction of size of conduit. is also used as a covering over the main insulation body of splices and terminals. but well suited for exterior use. and (3) bas a shelf life before use of at least 5 years without loss of quality. The normal insulation surface is considered sufficiently tough to resist normal conditions. 8-10 Insulating Tapes Insulating tapes of various kinds are sometimes used in the assembly of single. or sheaths. however. is applied over the insulation. arctic type for extremely low temperatures. either conducting or non-conducting. duct. These cables have no jacket over the insulation. However. Shielding of multiple-conductor cables is applied over the insulation of the individual conductors. hence well suited where bending is a requirement as in portable cables. A fibrous or other nonmetallic covering. and jacket depend on kV rating and whether or not the cable is to have conductor shielding and insulation shielding. Because of its poor electrical properties nylon is not used by itself as insulation. Nitrile-Butadiene/Polyvinyl-Chloride Jackets This jacket consists of a vulcanized acrylonitrile-buta diene/polyvinyl-chloride compound. and it is also used on control wire. as is description of the conditions under which the shield is open-circuited. An additional covering may be applied over the first one. The Effect of Corona on Insulation and Shielding As described in Chapter 3. or cement. They are applied over the surface of the conductor. This material is a tough abrasion-resistant thermoplastic which can be extruded as a thin protective covering over PVC or PE insulation. except that if the shielding is only for the purpose of reducing shock it may be applied over the whole conductor assembly. The various thicknesses of both insulation and conduc tor shields are specified by ICBA for the various types of cables and applications. whenever air is stressed electrically beyond its breakdown point. Similar insulation shielding may be of metal braid Or of concentric round wires. extra-heavy duty for portable cables. A separate metallic shield is not required. By virtue of the inherent toughness of the insulation surface. Minimum temper&u re* for cold weather app/iea tions 54. Dlscrete minimum values for tensile strength {psi) and elongation (percent) rather than "percent of unaged value.5 54. min. Values as 7. the minimum air temperature at which jacket cracking will not o<:cur is listed . 14. N NOTE: Some of these jacket materials also are used as wea.13. min.12. Test at "c for 70-168 100-'<. B. Elongation. Values as % unaged value 10. °c for 12.13. 1800 300 1800 300 1500 250 1500 100 1400 350 1800 500 1500 250 1800 300 Aging requirements ( air~oven) hr.3 I S4.13. Elongation. leEA S-19-81 Paragfaph No. Tensile strength.. min..insulation and relaled cable components TABLE 8-5 Specifications for Rubber Or Thermoplastic Jackets for Insulated Conductors and Cables Abstract from ICEA-NEMA Publication S-19-81-WC-3 i..therproof phases-to-Phase. semi~insulation coverings where conductor rating does not exceed 600 volts 8-11 .Irpose i PolyEthylene Heavy Duty 4. min.5 is omitted.min..8 54. and up. Description Synthetic Rubber 5BR Neoprene General Heavy Purpose Duty Black Black & Colors 3.ltY I Colors General Pl.13. Test at QC fOT hIs.. % Un<liged v alue Tensile strength.8 100-5 days 100-48 100-68 100-£8 100-68 1600" 250** 50 50 50 50 85 60 75 75 50 50 50 50 85 65 121-18 121-18 121-18 6. Elongation. min..030 in. ! ! 70-96 ! 1600** 250 .2 I 84. Values as % unaged value i I hr..13. NOTE.7 I Nitrile Butadiene PVCBrack & Neoprene 2.. Oil immersion at 13. min. psi.8 100-'<.. The oxygen test fOr 54. . Elongation % at rupt ure. See also NOTE on Table 8~2. but an oil-immersion test is made.13.6 54. I 121-18 121-18 70-4 60 60 60 80 I I 60 I 60 I 60 60 60 60 I 60 60 1 *Because the 'temperature gradientthrough insulation and jacket during operation assures a comparatively coo! jacket. 5." Appficable to materials having a nominal thickness of 0. Tensile strength. min. 54. Tensile strength. 11.9 Nitrile Chloro- Butadiene Sulph~ PVC- Black&' onate POly Colors Polyvinyl Chloride ethylene Black Heavy -10"'C -40"C -25"e -2S!>e Ol.13.4 1 54.13. The air 3ging tests for neoprene ~ackets for portable cables are based on 70"e for 168 hrs instead of 127"C for 20 hrs. Aging requirements (oxygen pressure) 9. for insulation described in Col. It is not only necessary that the insulation have suitable resistance to the chemical action of ozone.ground voltage. hence the insulation resistance will be one-half as much for a cable length of 2000 ft. and made after a constant dc potential has been applied for one minute. as compared with results of similar tests on other insulations. etc" are in ICEA and NEC publications. 8-3 and 8-4 list only tbe maximum temperature for normal operation. which with the explanatory footnotes provide data as a guide to insulation selection.to. Refer to NEC for full information. T = Thermoplastic. 8-3 and 8-4.henceinsulation thickness that meets this requirement is suitable. . measured after one-minute's applica 8·12 Tables 8-2. the increase in capaci tance ahove tbat of a dried block of insulating material when it is immersed and subjected to 60 Hz (EM 60 test) is an indication of the water absorption. Temperature Sheaths. NEC Designations The following summary of the most commonly used NEC letter-designations used for describing insulations and cable constructions may be helpful for understanding specifications that include NEC abbreviations. ICEA Performance Specifications As previously mentioned. Corona. R = Rubber (natural or synthetic). However. The corona-level requirement is listed as II.voJtage transmission lines. as used.level values listed in Tables 8-2. X = Cross-linked thermosetting polyethylene.IS of Table 8-2 a cable used in a three'phase 15 kV circuit has line-to neutral voltage of 15. pro vided the actual operating voltage is less than the rated corona-level voltage. 8-3 and 8-4 are to be considered in relation to phase. so the abbreviations must be used with caution.) The insulation resistance is obtained in megohms for a cable 1000 it long.2. or sheath enclosed cables are described in other chapters. This sum mary relates only to power cables of the usual kinds. overall jacketing. the elements of current are in parallel. Fillers and Binders The various kinds of metal-clad.discharge eflects are greatest in voids in the in sulation or between conductor and insulation Or shielding. as well as fillers.0/1.6°C. Further details are in the referenced ICEA publications. The following explanation of some of the terms used in the tables may aid their use. Waler Absorption By use of the electric method. Thus. There are limitations and exceptions. TA and TBS are not flame retardant. The ICEA standards contain adjustment factors for other temperatures. S3. but it also must withstand the tendency for burning that may occur as a result of corona~discharge current.2 was compil ed. A simpler form of insulation shielding is provided by the use of concentrically applied wires for potential-gradient control. The strand and insulation shields are so designed as to prevent ionization between the inner surface of the insula tion and the conductor and its outer surface and the metallic insulation shield. Or ten times as much for a cable 100 ft long. Insulation Materials. Additional details as to the sheath materials. This one-minute de value of insulation resistance principally is used for rough comparison of insulation quality. but they are purposely omitted from Table 8-2 because they are obsolete. Several early-type insulations stiD are listed in the ICEA publication from whlch Table 8. and binders. The visible manifestation of this ionization is corona. Because of occasional operation at a higher temperature (emergency-overload conditions) or for an extremely short time (short-<:ircuit conditions) additional data from the ICEA standards is supplied for some of the insulations in Table 9-7. The corona. By use of the gravimetric method. Similar information applying to jacket materials is in Table 8-5. and it is far from accurate because tests at other times than one minute may show wide differences and under ac conditions a different value is obtained. An abstract of the principal performance values applying to commercial insulations is in Tables 8-2. The test to determine one-minute dc insulation resistance by use of an immersed cable is at 15. See Appendix 8A for further discussion of insulation resistance R lac) under aC conditions. As the resistance is mea sured through the insulation to the outer surface.73 = 8. provided it is satisfactory otherwise. armored. though can be made so by suitable outer covering. usually flame-retardant polyvinyl chloride or polyethylene. insulation and related ma terials for cables are specified according to performance in stead of by composition and processing. Insulation Resistance (K (item 6) and formula in note to Table 8.covered and insulated wire and cable with the emission of ozone. FEP =Fluorinated ethylene propylene." XHHW. tion of constant dc potential. A "corona-level" test determines the absence of such voids that can cause local deterioration of the insulation. the actual increase in weight of the dried specimen of standard size after immersion for a specified time is divided by the total surface area of the specimen.7 kV. the characteristic bluish glow that sometimes can be seen at night along bare overhead high.OkV. in phase with the applied voltage. also suit able for direct burial. and for air it is 1. relative permittivity. when dry may be much increased because of water absorption or other factors. is an apparent indication of superior insulation qUality. and such variations are different in various materials. but with lead sheath. L = Lead sheath. also suitable for direct burial under certain conditions. Moisture and Oil-Resistant Quality SE Service-entrance cable (also suitable for interior wiring under certain conditions). Also designated specific inductive capacity (k). and applied volt age are the same.insulation and related cable components Heat-Resistant Quality ACL Same as AC. NM Nonmetallic sheathed cable. or THWN for dry or wet locations at 75'C XHHW for dry locations at 90°C and wet at 75'C APPENDIX 8A Elements of Dielectric Theory This appendix contains information that is generally understood by electrical engineers. B = Glass.. 8-13 . RW or TW for dry or wet locations at 60°C RH for dry locations at 75"C RHH Or THHN for dry locations at 90"C RHW. an insulator with a large <. mica. but must be fungus and corrosion resistant. and similar terms. W M Usually suitable for oily conditions (machine-tool circuits). the compound is principally synthetic or natural rubber. Charging Current and Leakage-Conduclion Current It is convenient to consider the current input into an insulator after voltage is applied as being in two parts: (I) a charging (or displacement) current Ic that serves to in crease the potential of the insulator by accumulating a quantity of electricity (coulombs Q) in the body of the insulator. THW. UF Underground feeder cable. Without "W" = Usually suitable for dry locations. and (2) a leakage-conduction current ie. but the moisture-resistant fibrous covering need only be on the i"dividual conductors. H = Usually suitable for 75'C. acquires a greater charge of electricity in coulombs Q for a given potential difference between its faces than will an insulator with a small". e. Dielectric Constant ("). with interlocking armor or close-fit ting corrugated tube. time.g. USE Underground service entrance cable. AC Armor-clad. The dielectric constant «.) of a substance is the ratio of the capacitance of a condenser with the substance as the dielec tric to the capacitance of the condenser with air as the dielectric. = I. the difference is neglected. NMC Same as NM. HH Usually suitable for 90'C (except XHHW only when dry). Do not confuse with "M" for metal as part of MC (metal-dad) for instance. it is a thermoplastic material: if it contains X. if it contains T. a low <. NEC Cable Constructions MC Metal-clad. usually meas ured in microfarads. = = Jackets and Sheaths (as part of a single conductor) Note: NEC does not use abbreviations for several jacketing materials (see Table 8-5). Usually suitable for wet and dry locations. Other letters are as previously indicated. Thus. ACT Same as AC.0006. A low <. N indicates nylon jacketing. hence for For a vacuum " engineering calculations. that supplies energy to heat the insulator (hecause of it' internal dielectric stresses) and to supply the energy losses associated with the current that passes through the insulator or across its sudace. Insulating Compounds designated by NEC symbols If the symbol contains R. but it may be helpful as a reference to some of the terms used in the tables and as the basis for calculation of charging current. BS Fibrous braid. or asbestos braid. is thus proportional to <" provided conditions of temperature. Not suitable for direct burial. However. Without "H" = Usually suitable for 60'C. it is a cross linked thermosetting material. ]\I Nylon. dryness. with flexible metal tape. The capacitance C of an insulator. 0. in wft. that is. are shown vcctorially in Fig. Dielectric Constant (") Under ac Conditions The calculation of dielectric constant hy measuring capacitance under conditions of steadily applied constant potential is not practicable for insulated-conductor studies. that is. the insulator (dielectric) is being charged and discharged at short intervals (l I 120 sec at 60 Hz). which is an abstract of Table 6-21 of lCEA Standard S-19-81. as follows: (Eq.e.5 % . however. Less than a full charge is acquired by the insulator at each voltage peak because the time is so short. assuming standard conditions (see page 8-12) of Chapter 8 and Tables 8-2 through 8-5). but it should be so stated.. Hence the tables in Chapter 4 for shunt capacitive reactance may be used for both bare and insulated conductors suspended com paratively far apart. When subjected to alternating potential. or by multiplying the charging current by the power factor that often is listed as a property of the insulation. 8A-2) X'c. . ac cording to ICEA standard). the power factor is usually designated as 0. where E = volts to neutral. The leakage-conduction current Ie represents energy loss. The latter value is a function of charging curtent Ie at the given frequency and insu~ation power f~. Dielectric Constant (") = 13 600 C 10g10 (Did) where (Eq. - 2 + • The total dielectric current/Il= (Ie Ie>". When a constant dc emf is applied. J{'c is obtained from tables.. SA-l) X'c = I I (2". and to compute the dielectric constant from the known relation that the capacitance of the air space occupied by the volume of insulation is 1. Hz. Then by geometry and suitable conversion of terms. R(fIC}= E/{1c x p. is practically the same as that of a bare conductor under the same con ditions. is slightly out of phase with Ic by angle 8. and R(ocJ that reflects the reduced capacitance under ac conditions. if Iellc is 0. 8A-3) C Capacity in microfarads of a 10-ft section of cable at 60 Hz. E (to neUIn>!) = 2". The power factor of the insulation is the ratio of Ie to Ie. it may take a half hour or more for equilibrium to be achieved so no further charging current flows.0 extends through such a small distance (the thickness of the insulation) that it does not significantly affect the capacity (or the capacitive reactance Xc) between the condl<ctors.}. C == capacitance in farads for the stated frequency Many tables only show X'c. ·It is important to distinguish between the insulation resistakce R. is greater than I. and voltage.covered and insvlated wire and cable The charging current Ic does not represent energy loss because after withdrawal of the voltage an equal current is discharged from the dielectric. an appreciable time is required for the insulation to acquire its full charge if its <. the rate of increase of charge Q within the insulator and the consequent rate of reduction of input current Ic will differ from what occurs when the emf is alternating. Capacitance of Insulated Aerial Cables The capacitance of an insulated 'Cable with ungrounded sheath. the usual practice is to find the capacitance of a cable of specified size and length under ac potential of specified frequency. nomogram.f.fX'c) The charging current Ic in amperes is as follows. or formula in a similar manner as described in Chapter 3 for bare conductors.ich E is volts to neutral (see the next section and example at end of this Appendix). The insulation resistance varies through a wide range depending on the dielectric and temperature as shown by Table 8A-I. i. Instead. = (Eq. Ele. measured at one minute after applying de potential according: to the leBA test method. D = Diameter over the insulation in any units d = Diameter under the insulation in the same units Capacitance of the cable also may be determined when frequency is 1000 Hz. greater than 1.f C Total Dielectric Current and Power Factor Under aC Conditions The charging current Ic depends on rate of change of applied voltage. hence its peak occurs when the voltage is changing at its most rapid rate. suspended in an overhead distribution line and well separated from the return conductor.005. I. The two currents. f C) where f = frequency. The corresponding value of C is readily determined by inverting the above equation to C= 1/ (2". The leakage-conduction current leis in phase with voltage. 8A-1. and it is usually expressed as a percent. The slight increase in capacity of the insulation caused hy an <. For some insulations. In practice. and the other terms are as previously defined. shown as I. when the voltage is at zero point of its wave. 8-14 The leakage-conduction current Ie may be calculated from data as to insulation resistance after correction for temperature. or as indicated by the relationship R = Ell. as is the usual condition. Charging and Leakage-Conduction CurrentS Under Direct and A /temating Potential Because insulation resistance is found by test under continuous application of potential (for one minute. in which R is the insulation resistance" as usually measured according to lCEA stan dard.. This effect under alternating potential is taken into account by the concept of Capaci tive Reactance X'" in ohms. closely equal to tan Ii. Usually Ie is so small with reference to Ic that it is neglected and the charging current Ic is considered to be the total dielectric Current 1. The resultant of Ic and Ie. Fe CO 1.48 1.05 50 55 60 65 70 75 80 85 10. or a curve may be draw".9 C (75'F) is 2.19 2.66 6.40 3.00 1.04 1. Leakage-Conduction Current Ie and Total Dielectric Current I in an insulator.87 5.80 2.22 1.74 0.16 1.84 4.75 1.97 2.9 X 10 13 ohms for 1000 ft.61 0.68 0.64 5. Ie/Ie == tan ~ Power Factor.56 0. Thus.86 1.00 1.09 0.43 1.17 4.00 1.00 1.06 0.09 0. and for 100ft is ten times as much.39 1.29 1.1 23.03 1.4 0.39 0.65 17.78 1.65 1.insula/ion and related cable components Fig.34 1.06.6 0. the ratio of insulation resistance at 61°F to its value at 60°F is noted.42 0.62 1.62 1.60 8.37 3.11 5.16 3.3 21. - TABLE 8A-1 Q Typical Temperature Corrections for Insulation Resistance at 15.34 1. the resistance at 23.59 1.08 2.3 X 10 13 = 31.56 1.82 1.00 1.21 4. 8·15 .3 X 10 13 ohms for 1000 ft.67 0.00 1.oF which is used to select which vertical column is used.8 0.76 3.SoC is 13.76 3.6°C (60 F) for Otller Temperatures.54 2.10 1.68 1.06 13.40 X 13.9 26.59 4.81 2.71 1.63 2.61 2.0 NOTE: Linear interpolation in the vertical columns is satisfactory.78 8. 8-AI.79 2.28 1. Vectorial Relationship of Charging Current Ie.00 1. the resistance of a 2000 it length is one-half of that of 1000 ft. An Abstract of Table 6-21 of ICEA 8-19-81 (1980) NOTE: From insulation test report.7 29.12 0.85 1. assuming the Coefficient is 1.8 15.47 9. and Q insulation resistance at 15.35 0.00 1.18 6.57 1. thereby obtaining Coefficient for .S9 2.47 2.65 3.32 0.0 12. in time-relationship with EMF vector E.00 1.00 lAO 1.6 18. 0 Coefficient for 1 F Temperatur.73 10.07 0. As the resistances for adjacent lengths are in parallel.08 OA6 0.11 1.51 0. 0.. is reduced to take into account that " of air is 1.g.... 8A-4 D = R - + 0.00736 X <. insulation thick ness. ac Resistance.7.f C (farads) The previously stated principles are the basis of the fol lowing computation: Given: :. and dielectric constant of the insulating material 'n as follows: C = (0.. a semi-conducting tape strand shield and 0. log". (Eq..1_3_13_ = 0.)/log.-0_. 0.Pe = (E1Rae) I (2'lT fC) = III (2 'IT fC Rae).1313 pfarad as farads ac - 2'lT X I 60 x 0. farads per 1000 ft.4 kV with grounded neutral..01 = I. transposing. 1..951 watts per 1000 ft. For this cable the dielectric constant " is 2.. microfarads per 1000 ft. in which C is in farads Substitutir.528" diameter.417.0686 amp per 1000 it.0686 X 2400 X O.01 Example of Dielectric Computation 2 020000 ohms for 1000 ft.. designated as Ie. (2. and expressing 0. • (Did).1313 . Did = 1. The following relationship is also known: Ian 8 = 0.0%..6 x 0.covered and insulated wire and cable Capacitance of Insulated Conductors With Grounded Sheath or Directly Buried Where the insulated conductor has a grounded sheath.. From Eq.02 megohms) E to neutral (volts) Charging current Ie = . in me tallic sheath.11 0" wall of cross-linked polyethylene insulation. Dielectric loss.--.X-. d = 0. watts per 1000 ft.417 0. 3" 0.-. 11 (2". amperes per loooft.7)/0.24_00--. megohms for 1000 ft.2_"-. or 1.01.528 2 (0.00736 X 2.528 in. and power factor tan 8 is .oI per conductor I. Charging current. 3 "X 1 000000 A #4/0 AWG aluminum single conductor. and substituting in Eq/8A-4.. .-60_X. designated as C. .1513 = 0. and '.1513. 60 Hz.748 in. applying to the space between the exterior of the conductor insulation and the metal duct..E= _. 19 strands. 8·16 Watts loss 0.110) = 0....8A-4) where C = Capacitance in f'farad per 1000 ft €r = Dielectric constant D = Outside diameter of insulated conductor d = Diameter of metallic conductor An approximation of C for an insulated conductor with out metallic grounded sheath but contained within a grounded metallic duct may be obtained from the above equation if an average D is estimated..1313 = X 10. designated as R(ac). C = (0. its capacitance is a function of diameter. in 3-phase circuit at 2..-X:.. Find: Capacitance. + + Example: What is Ihe minimum diameter of [he inside of the outer sheath of a 12~cQnductor ~o. short-circuit rating. It is assumed that he has available the latest National Electrical Code (NEe). applications and ampacity issued by ICEA-NEMA are also explained. are in Chapters 7 and 8. d 2T for single conductor cable (Eq. fiber. in the con ductors of the circuit. and a few are ab stracted. For twisted pairs (6 pairs. and of the various kinds of insulations. The design factors that inHuence the selection of a suitable aluminum cable are electrical. but it does cause eddy-current loss in metallic conduit.419 In . Duct. will not exactly bal ance because the conductors are not located at exactly the same position with reference to the conduit wall.55 in.(56) + 0. The eddy-current and hysteresis losses in conduit are reduced if the conduit contains the two Or three conductors that comprise a single circuit because their external fields tend to canceL The fields.155.155 (d 2T) 2t for 3-conductor cable (Eq. and also hysteresis loss if the conduit is of magnetic material.078io .9-3) Dr =2. sufficient to accommodate any distortion that may occur in the cable because of thermal expansion.1) D. am pacity. if any. thermal.• T O. Because the stray field surrounding a single conductor is not offset by an opposing field from an adjacent con ductor. The electro magnetic field surrounding a cable carrying alternating current does nOI induce stray currents in a non-metallic raceway. Tubular metallic raceways of steel or aluminum are generally designated "conduit.414 (d 2T) 2t for four-conductor cable (Eq.6010. = f (d where f the factor in Table 9-1. and operational-costs. Cable Diameter Most lists of cables show the outside diameter from which a suitable duct size or other support provision may be determined. Some of Ihese factors are con sidered in this chapter..080In:r Subsdtuting in Eq. = 4. 2. includ ing investment charges. 2/0 A WG aluminum cable when conductors are assembled in parallel and in (wisted pain.60): D. either as round conductors or as twisted pairs. as beyond the scope of this book.9. = 4.419 . mechanical." The cable is run loosely into the duct or conduit as distinct from having the metallic ouler covering closely fitting.160 = 2. 2(d 2T) 2t for round duplex cable(Eq. as~uming d = 0. Descriptions of cable components and their functions..· O. and also because of unbalanced loads.0. The important comprehensive tables relating to cable construction. and that the helpful supplementary tables prepared by wire and cable manufacturers to aid NEC applications are at hand. "f' = 4.155 (0.. it may be estimated from the dimension of its elements as follows: D. "f" D.Section III Insulated Aluminum Conductors Chapter 9 Engineering Design as Related to Cable Applications The data in this chapter provide the application engi neer with certain formulas and tables that can be used to advantage when selecting cable for ordinary uses. as with a lead sheath. 9-5 For single parallel conductors (for 12 conductors. The mathematical basis for some of these tables is described herein. 9-2) D. 1 . concrete or plastic. as follows: 2T) 21 (Eq.. Many equations and tables principally relating to cable design as distinct from applications are omitted..81 == 4. ability to withstand unusual environments. If the cable diameter is not known. however.9-4) Where D.419 + 0. Conduit and Raceway Inslallalions The terms "duct" and "conduit" may be used inter changeably to refer to non-metallic raceways made of such materials as transite.9·5) D. and other values are as above stated.156) + 0. = Inside diameter of sheath T Insulation thickness over the conductor d Conductor diameter Belt thickness (under outer sheath) + + + + + + + The diameters of cables of over four conductors con tained within a single circular oUler sheath are obtained.160 ~ 2. it is not customary to place a Single conductor in a metallic conduit by itself because of the resulting high 9-1 . Three conductors also are suitable for the usual 3-wire single-phase lighting circuit.414 2. it is sometimes advisable to divide a given load among several parallel circuits as a means of reducing losses.35 4.10 6.80 8.80 36 37 61 81 91 7.000 4. NEC and other Standards specify the maximum number of cables of a given size that can be installed within a raceway.0 2.30 10.155 4.60 4. losses.85 26 27 28 29 30 6.310 7. The three conductors may be parallel side-by-side or they may be triplexed as a spiraled assembly. providing this practice can be economically justi fied. 9·2 Also.000 5.70 6.000 3. A 3-phase circuit requires at least three conductors.550 6.000 10.240 4.240 6.000 9.10 8.50 9.25 6.85 4.15 9. it is usual practice to place the cables that comprise a complete circuit in one conduit.000 3. or nearly touch. The interior of a duct or conduit must be large enough to accommodate cable flexing and distortion because of thermal expansion.310 3. 9-1 <the overall ac/dc ratio) is seen to be 1. If the three-phase circuit includes a neutral.80 9. - - - 'Pairs cabled in the same direction of lay as the twist of the pairs.60 7.40 10.610 6.20 7.000 6.000 9. a fourth con ductor is required.550 6.610 5.35 9. Instead.240 6.000 10.000 7.50 11 12 13 14 15 16 17 18 19 20 .700 5.700 7. Spacing Be/ween Cables Calculation of series inductive reactance <and of shunt capacitive reactance of long high-voltage cables in duct) is usually on the basis that the outer surface of the cable insulation is at neutral potential.414 4. .35 21 22 23 24 25 5.550 11.40 6.75 5. because cable ac/dc resistance ratio increases with cable size.45 8.25 9. and that the cables in the duct touch each other.20 5.11 for 500 kcmil cable.000 7.95 10.000 6.000 8.610 4. The cable-loss ratio for the condition depicted in Fig.50 3.95 6 7 8 9 10 3.155 6.25 8.000 5.000 5.20 10.550 6.30 for 1000 kcmil cable and 1.155 2.insulated aluminum conductors TABLE 9-1 Factor "r'for Equation 9-5 for Use in Determining Cable Diameter Where Cable has More than Four Conductors Factor "f" Factor IIf" Conductors Single Round or Pairs Conductors Number of Number of Twisted Pairs Conductors or Pairs Single Round Conductors Twisted Pairs 1 2 3 4 5 1.50 7. 2.000 4.50 5.35 7.310 5.414 9.90 31 32 33 34 35 6.414· 3.70 4.700 2. The ac re sistance includes skin. sheath and conduit losses. shields. ICEA and AEIC publications should be consulted for more accurate values. The alternating current resistance ofClass B concentric stranded aluminum cables at the secondary distribution voltages at 60°C.engineering design as related to cable applications and Shielding (but not external metallic armor) as used for cables of various voltages and insulations. and 9(fC is listed in Table 9-3 for two typical conditions of installation.035. grounded-neutral. f2 R.29 I o I ~ 100 '" w ~ I ~u :g1J5 I o :::i ~ ~ LID I I I I I /\ AC/OC ~ to '50 I 100 I . 9-1. Illustration of change In overall resistance (Reff) and acldc 60 Hz ratio as conductor size increases for each conductor of a trlplexed 3-conductor assembly of Insulated cable.f. . If an aluminum conduit is used the resistance increase for conduit may be neglected for sizes 4/0 and smaller. Class B concentric stranded.05 '" !< :E RATiO 50 ill'" '" ~ :< '">w o // '" CABLE SIZE KCMIL Fig. and for computing energy losses.f!.15 150 I I I ~ o o I I 1.30 I I I I I 1. 2. that is. (l) that caused by skin effect and proximity effect in the conductor itself and (2) that caused by losses in the insulation. and for larger sizes the amount of increase above that of the nonmetallic-conduit condition is estimated in the manner shown on the table (see also Eq. page 9-8). shield. it is a conservative assumption that all heat generated in any part of the cable originates in the conductor. . in steel conduit at 25 k V. Regardless of this variation of point of heat origin it is customary to assume that for energy-loss computations.. with short-circuited shields and sheaths. 750 C conductor temperature.. Cable-Conductor ReSistance 300 1. heat generated from eddy current losses in a sheath or conduit does not affect con ductor temperature as much as will the same amount of heat generated in the conductor itself. Manu facturer's lists.t! is the resistance in the PR. and insulation losses. and sheaths. for example. such as skin and proximity effects. 75'C. for precise estimates of con ductor temperature and ampacity it is sometimes neces sary to separate the heat losses into two parts. The correspond ing direct current resistance also is shown. insulation p. in which R. Vol. However. and also the increase caused by use of steel conduit provided the two or three conductors of one circuit are contained within one conduit. An explanation of the various acldc ratios and their use follows: When determining ampacities. I I / V z . page 265. showing average outside diameter of typical cables of various kinds. as stated..and proximity-effects. Data from JCEA publication No. the resistance of a cable carrying alternating current is increased above its resistance measured by direct current by such· an amount as will reflect the above mentioned losses. depending on whether it is aluminum or steel.5 I 1. for a given condition the de resistance of the circuit is assumed to be increased by the acldc ratio so that when this ac resistance is multiplied by f2 the total energy losses are obtained.. term which includes all losses associated with the cable. 9-6. The usual measure of these energy-loss effects is the acl de ratio. = 0. 9·3 . To facilitate obtaining this spacing Table 9-2 is pro vided. and in the latter category is loss aris ing from circulating eddy currents and hysteresis losses in the surrounding metallic conduit. NEC. P46-426. JR.. This is not strictly true because. taking into account the usual jacketing The resistance of the conductor of a cable in ohms per unit length is required for computing voltage drop. Vol.50 0.95 2.40 1.30 2.56 1.681 0.00 1. sometimes a lead sheath 9-4 may be included without increase of diameter. the values are increased by 0.56 2.82 1.29 .94 0.40 1.60 1.73 1.292 Approx.ins"lated aluminum conductors TABLE 9-2 Comparison of Conductor Diameter and Approximate cable Outside Diameter of Typical Single.92 1.34 1.32 1.92 1.62 0. . For cables above 5 kV with ungrounded neutral or cables at 133% insulation level.22 1.75 0.67 0.43 0.07 1.72 1.45 2.184 0.33 1.68 1.66 0.26 1.24 0.51 0.40 1.00 1.17 1.89 1.92 1.27 Non·shielded 5kV'H 0.74 0.04 2.47 0.12 1. consult manufacturer's lists.24 2.08 1. The values in the other columns that are in regular type correspond closely with those listed in ICEA No.31 1.526 1.46 1. **The 5 kV non·shielded cable.29 0.89 1.71 0.26 1.93 1. Voltages are ac Line-to-Line with Grounded Neutral* Except as Stated (See explanation at bottom of table regarding values in italics) Size AWG or Conductor Diameter (inches) kcmil 6 4 2 1 1/0 2/0 0. Though the listed values are generally suitable for preliminary studies.15 1.63 1.77 1.83 1.72 1.90 0.528 0.26 2.09 1. 1962.57 0. imporant calculations should be made by use of actual diameter of the selected cable.62 3/0 0.34 0.71 0.18 1. have strand shielding.20 0.35 1.81 350 0.36 1.46 1.65 2.37 0.28 1.65 0. Outside Diameter of Cable (inches) Thermosetting or Thermoplastic Insulation 600V lkV 0.44 .998 1.04 1.30 1.94 1.85 0.632 1.60 0.13 *For voltages through 5 kV the diameters also apply If the neutral IS ungrounded.74 0.67 4/0 0.332 0.64 1.92 500 0.55 0.61 1.70 1. for I kV.03 1.38 2.58 2.20 0.87 1.16 0.18 1.02 in.58 1.25 1.42 1250 1500 1750 2000 1.06 0.77 1.55 1.44 1.06 1.96 3.79 1.84 1.412 1.73 2.61 1.14 2.02 2.38 1. when increased to allow for jackets. as well as all shielded cables.01 0.02 0.79 0.77 0.50 1.232 0.373 0.61 0.418 0.32 0. The listed overall diameters of 600 volt cables are from Column 4 of Table 5 of NEe (1981) and are fairly representative of Type THW and triple-rated RHW /RHH/USE unjacketed cable with XLPE insulation.84 1.22 2.15 2.57 0.76 2.88 1. These diameters do not apply to cable with metallic armor.97 2.65 1.07 1.42 0.96 1.61 0.94 1000 ~ 1. The values in italics for 5 kV and above are representative of cables with XLPE insulation and include the thickness of pVC jackets on shielded cables.98 0. II. By omitting the jacket.575 0.95 1.75 1.07 3.88 2.39 0.73 0.94 15kV Fully Shielded 25kV 35kV 46kV 0.82 1.05 750 0. 1.09 • 1.152 5kV 0.34 2.44 1.49 2. P-46-426.62 2.46 2.53 0.813 1.91 2.289 1.470 0. Class B Concentric-Stranded Aluminum Cables.79 0.92 1.96 1.13 2.85 1.45 0. 1.50 1.16 1.80 2.11 1.23 1.53 0.73 250 0.03 1. 0173 : ·Calculated from ICEA Resistance Tables for Class B stranding and corrected for temperature.0193 0.266 0.382 0.D15 0.0525 0. and for larger sizes is in the range %%-2% more than the resistance of the conductor in non·metallic conduit.0593 0.253 0.211 0.808 0.105 0. OneSingle Cable Conductor : or2or3 in Air.382 0.0406 0.0288 0.0186 0.335 0.151 0.211 0.0117 0.0638 0.0674 0.0353 0.058 0.151 0.240 0.132 0.0445 0.0101 • 60 Hz ac-60'C I Multi-Cond.072 0.0530 0.0317 0.0106 I * 60 Hz ac-!lO'C Mu Itl-Cond.159 0.0374 0.0578 0.102 0.D265 0.765 0.0954 0.0822 0. hence of lillie significance except in critical cases.085 0.119 0.0533 0.191 0.808 0.120 0.319 0.0623 0.253 0. For higher voltages or other installation conditions.0239 0.0472 0.0865 0.0207 0.0320 0.0892 0.765 0.0166 0.303 0.0635 0.126 0.0381 0.0448 0.211 0.253 0.040 0.101 0.0427 0. If aluminum is used.0744 0.0806 0.0608 0.0507 0.0556 0.0122 0.106 0.151 0.402 0.0273 0.0353 0.127 0.0808 0.422 0.0228 0.0124 0.0847 0.191 0.191 0.126 0.0141 0.0178 0.0135 0. Class B-concentric strands Ohms per 1000 feet • Class B ! AWGor kcmi! de at 60°C 6 4 3 2 1 I/O 2/0 310 410 250 300 350 400 500 600 700 750 1000 1250 1500 1750 2000 0.159 0.0296 0.0357 0.422 0.0177 0.201 0.0318 0.335 0.0253 0. see Table 9·4. i : de at 75°C 0.0303 0.101 0.0336 0.422 0.engineering design as related to cable applications TABLE 9-3* Resistance of Aluminum Cable with Thermosetting and Thermoplastic Insulation for Secondary Distribution Voltages (to 1 kV) at Various Temperatures and Typical Conditions of Installation Note: The metallic conduit is assumed to ba steel.335 0.848 0.0131 0.0201 0.0504 0.Q706 0.0203 0.0176 0.0605 0.0560 0.0302 0. 9·5 .0148 0.0307 0.0686 0.240 0. Buried.167 0.037 0.319 0.507 0.266 0.808 0.0672 0.0177 0.319 0.402 0.382 0.0424 0.483 0.240 0.0168 0. Single Buried. Cable or2or3 Single Conductors • or in in One in One Metallic Conduit de at 90°C orin ' Nonmetall ic Conduit Nonmetallic Conduit Metallic Conduit 0.0428 0.0908 0.0766 0.0269 0.107 0.0963 0.848 0.0222 0.0186 0.266 0.0218 0.0708 0.0111 0.201 0.0292 0.0302 0.0575 0.0322 0.045 0.132 0. One Single Cable or 2 or 3 Conductor Single in Air.507 0.0337 0.159 0. the efleclive resistance is about the same as for single conductor in nonmetallic conduit to 410 size.0169 0.0228 0.765 0.848 0.0370 0.0184 0.0137 0.0741 0.0212 0.0127 0.0143 0.303 0.0216 0.0115 0.201 0.0162 0.0953 0.0654 0.0340 0.507 0.0215 0.119 0.167 0.533 0.0158 r 60 Hz 8c-75'C One Single Conductor in Air.0403 0.0158 0.0288 0.0333 0. Buried.133 0.0111 0. Conductors or in in One •Nonmetallic Metallic Conduit Conduit 0.089 0.0282 0.483 0.402 0. Conductors Multi·Cond.0552 0.167 0.0121 0.483 0.533 0.303 0.533 0. 126. but are higher in conduit (aU for a given voltage). or thermoplastic materials as indicated in the -heading. Fig. 9-1 depicts a similar relationship for 25·kV cable.. 11.and proximity-effects ohms per 1000 ft* Hence ac/dc ratio for conductor alone is Q. higher than generally '1ccepted values.::. but the ICEA report speCifies it as representative of average 'conditions after many years of use. or direct burial.28 X 0. In any event the contribution of dielectric loss to the lotal heat loss is small at voltages through 25 kV. P-46-426. and some of these values are listed in Table 9-4-for I kV as typical of the low voltage field.02326 I. For a 60().035 power factor. Single-conductor cables with metallic sheaths or shields installed in air. The ac/dc ratios are the same for'in stallations in air. there is no magnetic effect hence no hysteresis loss in the conduit. though ampacity tables based on them are explained in Appendix 9A. and shields to loss in conductor is L 167*. though for the l-kV listing it may be ungrounded. Vol. These insulations are assumed to have 0. Other assumptions upon which the table is based are as follows: Maximum conductor temperature is 7S 0 C. Triplexed 3-conductor cables with short-circuited sheaths or shields. Fortunately ICEA as part of its extensive report on ampacitie. page 265. in steel conduit at 75"C.096 The ratio of sum of losses in conduit. II (1962). = Values are shown for air. based on PR. 60 Hz ac..02J2 1. The overall'se/de ratio is 1.L is justified.0271 ohms per 1000 ft (R. These ·are not shown herein in detail. 2. See also /CEA Pub. With aluminum conduit. (1958). in ducts. The ICEA tables also list values for 8 kV and 25 kV for thermosetting and thermoplastic insulations. of aluminum cables included data from which presently applicable acldc ratios may be obtained. Table 9-4 is based on these types. As present practice mostly applies for aluminum cables to those with thermosetting or thermoplastic insulations. The eddy current loss in aluminum conduit is also less than it is in a lead sheath because the conduit wall is farther from the conductor. class B concentric stranding. Three single-conductors arranged close together btlt not triplexed. rubber-like or thermosetting -materials. Losses in cable in air are based on no wind or solar radiation. aclde Ratios for Aluminum Cables Knowledge of ac/dc ratios applying to present-day types of aluminum insulated cables is essential for voltage drop 'and ampacity calculations. 30-in deep to cover. Nonmetallic jackets are included where required by cable design. Cables in Aluminum Conduit The lCEA tables list ampacities and acldc ratios for cables in steel conduit. volt 1000 kcmil cable.02326!O. The total heating effect." is the basis of thennal calculations to determine ampacity ratings.0212 = 0. The problem may further be aggravated by the low impedance shields on lie cables of the URD/UD styles in use. Extensive additional info~maljon regard ing ae/de ratios is in ICEA Publicalion Committee Report on AclDc Resistance Ratios 01 60 Cycles. duct. sh"eath. with short-circuited sheaths or shields. with insulation pf of 0. and for 15 kV as typical of moderate distribution voltages. Conduit grounded at end of run. all with open-circuit sheaths or spiral concentric neutral (if directly buried). hence an overly conservative value for p.. 1000 kcmil Triple-xed rubber or thermoplastic insulated cable. and for duct and direct-burial (values are the same for duct and direct-burial) for a = 0. Grounded neutral is assumed. which are sometimes used with aluminum. Strand and insulation shielding is assumed above 5 kV. designated by ICEA as the Qf ratio. in duct. 9-6 The cable constructions to which Table 9-4 applies are as follows: given voltage.) This example shows the high acldc ratio that may occur with cables of large diameter in steel conduit. though reference to the source" is required for accuracy.insulated aluminum conductors Example: A I5-kV. or directly buried with separation. and with short<ircuited sheaths and shields (conduit grounded at end of run) has the following aclde reslstance ratios for each cable: Dc resistance at 75<>C 0. and up to 69 kV for solid impregnated paper insulated cables. The values at a given voltage are the same for installation in air. if buried. and also for economic studies that compare investment and operating-cost factors. or directly buried.01. P-46·426 Vol. in separated duelS. 3.0212 ohms per 1000 ft Ac resistance including skin. the overall acldc ratio is only 1.. The increased loss because of eddy current in an alumi . Conductor is Class B concentric stranded. L28 The overaJ! effective resistance for estimating total heating effect is 1. P·53·416. The eddy current loss also is much smaller in aluminum conduit than in steel because there is no increase of the field due to permeability. but are higher for conduit. and for a 4/0 cable it is less than 1. 36-in depth to-cable axis.:. ·Values from ICEA Pub.096:.167 X 1.. General Conditions Applying to Table 9-4 The insulations are rubber. Values for the other standard cable voltages may be roughly estimated by extrapolation from the l-kV and 15·kV values in Table 9-4.035. UThe data in Table 9-4 are abstracted from [CEA Publication No. as ~.. x x x x x x x x x 4/0 100. 1.. The overall aclde ratio is 1.75 1.049 29.070 29.---- 10 .90 x 350 60.(){)2 1.93 1. 0 n o 0 m ~ ~ Q g .10'31. Factors listed under heading OE are ratios of the sum of all cable and conduit losses (in conductor._ x x x x x x x 100.74 1.16 1.96 )( x x 1750 12.o x U}21 1..010 x 1. 29. factors listed under the heading as are the ratios of the sum of all cables losses (in conductor. 201.27 60. sheaths and conduit) to losses in conductor alone (including skin-proximity effects). Q .029 for lhe conductor alone.conductors In Duct Of In Air.073 43.167 22.41 x 30.015 x 1. Duct In Steel Conduit Roc ~S In Air.019 x 1.017 85.52 x 84.S4 x QS 1. The ratio (from tablel is 1. I--'-=:-~~ Sinole Conductor I.005 x 1.07 x x x x x 2000 16.69 1. .8 750 QS 1.58 17.eAWG tanco of at 7SoC I.41 1. 4 507. • • x x x x x x x x x x x x x x x x 1.95 1.d~rlld~u"tol" InAir ~ ~~~~~ 3. x x x x x x x x x 2/0 159.13/28.10.conductors t~~ In Duct InAir or Buried komi! In Air.00 1.026 6104 1.4 42. If an "x" is rn any column headed Rac the factor is not significantly different from the corresponding dc resistance listed in the table. and sheaths) to losses in conductor alone (including skin-proximity effects).26 1.95 x 61. (Q " . Factors listed under heading Rac are alternating current resistance value!> in microhms per ft including skin and proximity effects.63 x 60.011 x 1.44 1.55 x 11.64 x 42. Faclors lor 5-kV.102 23. 8·kV.22 x 29.86 x 28. and 25·kV cable. PA6-426 Vol.14 42. x x x x x x x x x x x x x x x x x x x I/O :153. 21.8Il 1." .003 l( 28.001 22..67 )( 29. The listed factors are from ICEA PUb.009 1. 11.0212 ohms per 1000 ft.33 x 85. • • x • x • x x x x x x x 319.003 14.006 L_ 250 1000 R. .64 x LOBO a.070.16 x 43.043 43.96 21.09 L012 135.24 x 85.007 x 1.025 x L010 l00. Example: For each cable of a ~riple)(ed assembly of three 750kcmilcables at 15 kV in a non·magnetic non-metallic duct.3 Roc QE x 84.. Ambient temperatures a~e 20°C for duct or directly buried.64 1.000 may be used.62 x 60..2. ~~~ ~ 1 kV .2.69 )( x x Qf x 85.70 x R".003 84.95 x 13.049 29. (1962). InSteel Conduit or Buried or Buried Roc QS 3 Conductors QS QE 'QS R.001 29.90 21. insulation.90 x 28.62 x 60.004 x 1. for 1000 kcmil.96 1. and 40°C for air or conduit.002 17.13 microhms per ft. are also listed in the ICEA publication.67 1.018 85. per ft.86 x 14. and 3 (page 9-6) with Thermosetting and Thermoplastic Insulation* (See Section B for Asbestos Insulation) c :)nductor dc" Rois- S .031 28... shields.66 )( 43.08 x 6LSO x 60. To convert to ohms per 1000 ft.27 1..87 L019 61.57 x 17. " =: 0. Duct Buried or Buried Conduit or Buried ---- x 6 In Steel Conduit ..31 1.07 1.75 )( 22. aiD a.TABLE 9-4 Factors for Estimating 60-Cycle addc Ratios for 1-kV and 1S-kV Insulated Aluminum Cable at 75"C for Constructions Nos_ 1.005 13. If an "x" i~ in any column headed QS or QE the value 1...65 x JO. :/ 1 15 kV Single Conductor~ ·liriPleK.70 1. x x x x x x x x x JlO 126. The R.006 x 1. shields.02 L029 43.32 x 43..61 x 21.119 29.09 x 24.005 x 1.64 x 1500 14.1 12.070 = 1._ x x x R..112 85.014 x 1.." QS R" x x x x x x 1.001 21.3 X 1.. point off three places: thus.~..005 1.10 x 21.55 1. Duct Roc QS R~ Qf x x R.2 R" x 84.79 x 23.61 1.047 60.005 • All resistances are listed as microhms per ft. the RA~ (from table) is 29.41 x x x x x x x x x 1250 17.029 X 1.1 14.003 12.1 microhm. The corresponding acldc ratio i.c5' 14.6 11.30 x 61.8 x x x x x x x x x x 1.004 x x x x x x x x x x x x x 1.96 x 42.6 500 42.004 1.90 x 84.70 x 43.13 1. TriplOKed. No. ff = 28.89 x 23.3 =1.64 x 42.57 1.0 17. II.79 1.069 23.006 -----. Duc' In Steel In Air.5? 1.031 85.01? 1. x x x x x x x x x 808.6 60. insulation..006 11.u ohms/ft . 9-7. By reference to (Al it is noted that vector OE. In practice the Ix vector is usually smaller than the ir vector and the angle between OE. the induc tive reactance is about the same as that of bare conductors. using the R~e value for conduit from table (29. bearing out the weU known fact that inductive reactance does not significantly affect voltage drop in circuits of 100% load power factor. and (B) shows it when load power factor is 80% (cos e 0.070 + (0.4 microhm' per ft (0. the minimum circuit in ductance occurs when the inSUlation of both conductors touch. series inductive reactance in the supply conductors causes voltage drop at the load end. When cables are far apart. and particularly if the load power factor is low.08 The overall ac/dc ratio.13).0314 ohms per 1000 it)..insulated aluminum conductors num conduit is so small that ordinarily it can be neglected in computations of acldc ratio where cables of one circuit are contained within a single conduit and each cable is 410 size or smaller.3 x 1. = QE value from Table 9-4 for steel conduit Example: For the example appended to Table 9-4 the QS ratio at 75"C for duct is 1. say 10 miles in length or over. + (0. thus.08 = 1.80). The distance between the centers of the conductors then is twice the thickness of insulation and covering plus the diameter of the metal conductor. but for small spacings it is convenient to apply Eq. Series Inductive Reactance The effect of series inductive reactance of a cable in a circuit is depicted by Fig. The method of computing inductive reactance may be according to the X. = Voltage vector at supply end OEL = Voltage vector at load end 01 = Current vector ix = Voltage~drop vector due to inductive reactance "x" ir G = Voltage-drop vector due to resistance Hr" Angle of lag of Ctirrent vector in relation to OE L As voltage drop ir is in phase with 01. However.1I and R". is almost the same length as vector (EL ir). such as with certain electric furnaces.1. 9-2.119 .nan at the sending end. and ELl when the power factor is significantly different from 100 percent. for . ir will be parallel to 01. For larger cables. (Eq. applying Eq.070)) 1. is acide = (29.19. ix will be perpendicular to 01.13i28. a conservative esti mate of overall acldc ratio with aluminum conduit con taining a complete circuit is obtained by using a QE value obtained as follows: QE" where QS. Xd concept used in Chapter 3. The diagrams are drawn to accentuate the relationships. 9-6 is = QE" 1./.2 X (QE. from (B) it is evident that Ix considerably affects voltage drop (the difference between E.2) x 1. 9-2 (A and B) in which (A) shows volt-ampere vector relationship when the load power factor is almost 100%. as described in Chapter 3. In the usual circuit supplying non-inductive load or ono of lagging power factor. b~t if the load has leading power factor.. Since the inductive reactance decreases with reduction of spacing between a conductor and the return conductor of the circuit which may be a ground. Volt-Ampere Vector Relationship in Circuit Having Cable with Inductive Reactance: (AJ for almost /00% p. and OEL is smaller. = o I Fig. it becomes significant only for insulated long lines. 9·8 where OE.11 = 31. The similar shunt capacitive reactance in short lines of moderate Voltage usually may be neglected. the series inductive reactance may nat be large enough to compensate for the capacitive reae'm1ce and the voltage in the load end would be gt: at" ·.9-6) QE" = QE value for aluminum conduit QS. and as reactance drop ix is in quadrature with 01. Generally. (SJ for 80% pf.2 X (1. 28.070 and the QE ratio for steel conduit is 1. + Series-Inductive-Reactance Calculation The voltage-drop effect caused by series inductive re actance requires consideration for insulated cables in which the go-and-return conductors are close together as when triplexed or in duct or tray. The QE for aluminum conduit. = QS value from Table 9-4 for nonmetallic duct QE. 9-3. which because of the magnetic~armor effect is increased by the applicable factor 50% -20% (as there is nO random lay) or 30% to 1. equals the ix drop to neutral in volts for that con~ ductor. though in approximately equilateral arrangement. or 0. because the force fields around the con ductors in each cable tend to neutralize..0153 s + 0. X 10-3 (Eq. From the nomogram the reactance is found to be 0. ohms per lOOO ft.5 X 1. r Radius of metal portion of the conductor. 0. If this cable is in a magnetic conduit. in cluding strand shielding.or 3-conductors in non-magnetic duct or conduit: X = 2"f (0.00 in. each will have an average reactance to neutral which can be obtained from Fig.0362 ohms peT 1000 Ft. centers. The outside diameter of each conductor is 0.0315 X 1. If these conductors are in a magnetic conduit. Supplementary Table for Series Inductive Reactance For moderate insulation thicknesses. diameter (insulation 155 mils thick) in non-magnetic conduit. perhaps caused by thermal flexing.2 = 0.038 ohms per 1000 ft. 9-3.'mil. of one conductor. the term "sector" refers to a single conductor in which the strands are arranged approximately as a 1200 section of a circle (see Fig. in. Table 9·5 shows 0. if single conductors are alongside of each other.5 X 0. multiplied by rms amperes in the conductor. the reactance will be 0. Thus. the reactance per conductor to neutral is 0. nO ran~ dom~lay correction is necessary. The random*lay plus magnetic~conduit adjust ment is 1. 9~3. if any f = Frequency.26 X 4. 9-9 . A-I>I UC)U SYMMETRICAL FLAT ! = 1.1404log.0315 ohms per 1000 ft. but it is useful only for the particular condition stated in the table. hence the reactance per conductor is 1. s Spacing between centers of conductors. Example 2: Using the nomogram find reactance of each con· ductor of a 3-conductor 600~vo!t cable. 600~volt insulated steel~ armored conductors arranged symmetrically fiat on 4~in. approxi~ mateiy touching in equilateral arrangement. 8-2b).094 ohms per 1000 ft. The effective spacing from diagram on page 9-9 is 1. the adjustment factor is 1.890 in. Example..0377.89 in. Table 9-5 provides closer numerical values for Eq.890 in.engineering design as related to cable applications 2. which equals the spacing. A-+I . care must be taken in the use or tables or nomograms neglecting this factor when dealing with cables having low resistance shields. Draw line from 750 kcmil to 2.031.0473 ohms per 1000 ft. which is about average for a 15 kV cable~ thus the arrangement is equilat eral with outer jackets touching. diameter in nonmagnetic conduit. spacing distance.5 t and the reactance is increased to 0.. However. The increase for "random lay" in this instance is the result of unequal spacing of the conductor in the conduit.0315 ohms per 1000 ft..122A C) (9± I. 9~7. = Shunt Capacitive Reactance Although the capacitance of an insulated conductor be tween its outer grounded surface and its inner surface at * Source General Electric Company Data Book. From Fig. 9·3 find reactance of each of three single conductors in magnetic conduit. per 1000 ft. The designation "single conductor" refers to one of several single conductors of a single circuit that lie loosely together in one conduit. which adjusted for random lay is 0.0471.149. 9-7.o . and from notation on the nomogram. not bound to gether Or are closely adjacent on a support.30 X 0. the reactance is 0. in. 9-7 than obtainable from the nomogram. each 0. This value.. In the table of Corrections for Multi-Conductor Cables. Example 1: From Fig.00 in.072 ohms per 1000 ft. From Fig. The outside diameter of each cabJe is 2. Table 9-5 shows 0..0378 ohms per 1000 ft. Reactance of Conductors on Rigid Cable Supports If a multi-conductor cable is placed alongside another multi-conductor cable on a flat tray or other rigld Hat sup port. length.. concentric stranded. Hz (It is convenient to use 377 for 2" X 60) = = The distance s (assumed average effective) for various conductor arrangements is per following diagrams: 0\ OO~ G'f I4-A-+1 A EQUILATERAL TRIANGLE ~=A RIGHT ANGLE TRIANGLE ! = 1. each 250 kcmil. Fig.0 == 5. concentric stranded.OS7 ohms per 1000 ft.0 in.072 0. it crosses the reactance scale at 0. the inductive reactance of a conductor in that cable is not significantly increased by there being another similar adjacent cable. that the separate single coo ductol'S of one cireuit are loose in the conduit.* aids use of Eq.) r . Example. The presence or shield current in shielded cables alters the inductive reactance predicted by Eq. The conduc~ tors are bound with tape as an equilateral triangie (triplexed).038 = 0. 9-3.26A ! = {AxSxC)1/3 A usefUl nomogram.. Assume three 250 k\.5. each 7SO kcmH. so there is little mutual-inductance effect unless loads are unbalanced...9-7) where X Inductive reactance to neutral.or multi-conductor cables. namely. For any other of Ibe usual conditions applying to single. Three 250 kcmil conductorS. such as prevail in secondary distribution circuits. it is generally simpler to use the nomogram to gether with the adjustment factors noted upon it. 11 ~ -i . 1 .0 10. 400 .122 I...40 Sllil . Mog".04 _18 ~~j 1...8 I.230 \.. 6 .4 °1-1 .000 ! . Nomogram for Series Inductive Reactance of Conductors to Neutral (60 Hz) Based on Eq.10 1000 ..000 .15 .66 .940 1..000 ... 9-7. s..000 1. 4.970 1.210 1.c-USi! Volve 10..186 1.14 .095 SINGLE CONDUCTORS rN CONDUIT t<hlll·MognetJe-lnt.06 1500 1250 1.. CONDUCTOR CA8LES _--- IN CONDUIT MULTIPLE _..$ -- uoo DO .0 5..OB 750 .~-No Fig. Round co"u . 0 2 4 CQRa£(.insulated aluminum conductors SIZE CONDUCTOR c-c OIA.000 1. The dash examples in the text.3 .134 16 500 600 1..01 2. Mogfietic-llI()tll<:ue 50% for magnetic efllct onC r<:H'Idam lay..Illipl'finS 'adQ( 1.100 ... 9-3. ..r ROIJl!d So..j ". ~tou wj.l50 SOD "- .06 3D~ .000 ..000 ••60 1. .0 6 ..93' 1. ..10 .146 . I . Insulated Rel/nd kcmil ...05 18 20 . 4 .2 .." N¢n"'''Qgn~<: Ma9MI.TIQNS FOrt MULTI·CONDIJCTOR CAStES 8 10 Cond.20 .199 1.5 3.18 . M.ogrlOlk Bifld..0 8.191 1. 12 1I~ t<:! 300 14 "" as" LOOO .5fl Correction..973 9·10 24 U49 .4 . --':-=r.. IN AWG OR KCMIL INCHES 2.. '...~ Bil'l(hu Bind..925 7'" .16 ....0 1.05 .25 3 ..03 21 Ml... 300 ..tall/> 20% far randQm IQY.. DOOr- ___ •8 .. .225 1..._ ..9" L140 400 1..0 6.216 1.0 15 20 25 30 40 50 66 80 100 lines apply to the two .r.D .2~ 1.S SOliD SPACING IN INCHES STRANDED . No-n·MQ91'1i11. 350 .I. .h..... 250 " .! 11 1.950 1.116 2000 1m . 0429 .0386 .0380 x 0.0390 .0338 .0464 .0499 .0347 .0416 .0447 .0443 .0477 .0389 .0438 .0431 .0356 .0450 .0326 .0401 .0459 .0337 . or 4 Single Conductor in Same Conduit Ohms Per 1000 Feet-GO Hz_ NONMAGNETIC CONDUIT (ALUMINUM) Conductor Covering Thickness (Insulation WIRE SIZE AWG OR MILS kemil GO 6 4 2 1 1/0 2/0 3/0 4/0 250 300 350 400 500 600 700 750 MAGNETIC CONDUIT (STEEL) + Cover) Conductor Covering Thickness (Insulation + Cover) WIRE SIZE AWG OR 80 95 _0404 .0497 .0370 .0554 .0349 6 4 2 1 1/0 2/0 3/0 4/0 250 300 350 400 500 600 700 750 - MILS 60 80 95 .0336 .0349 . \() .0381 .0351 .0397 110 125 140 155 .0486 .0419 170 ..0335 170 .0373 .0414 .0388 .0505 . for a triplexed 250 kcmil cable with minimum 155 mils insulation' thickness of each conductor.0363 .0353 .0348 .0446 .0402 .0367 .0342 .0390 .0459 .0415 .0405 .0435 .0442 .0351 .0436 .0421 .0357 .0363 ohms per 1000 ft.833.0503 .0331 .0332 .0519 .0457 .0438 .0324 .0329 155 .0414 ..0338 .0318 110 .0342 190 kcmil .0467 .0520 .0344 .0422 .0537 .0436 The above tabular values include 20% adjustment for random lay of single conductors in a nonmagnetic conduit and a 50% adjustment for random-lay and magnetic effect in sleel conduit.0430 .0402 .0538 ..0488 .0363 .149 = 0.0380 .0399 .0333 .0456 .0428 .0405 .0367 .0424 .0530 .3.0387 .TABLE 9-5 Inductive Reactance to Neutral 2.0384 .0328 .0459 . ~ cO' => f.0439 . cBS· m ~ CO .0418 .0423 .0439' .0360 .0475 .0343 .0453 .0343 .0428 190 .0367 .0428 .0373 .0334 .0441 .0357 .0350 .0401 .0473 . For the right-hand section in such a case mulliply the adjusted left-hand section values by the magnetic-binder adjustment factors shown in Fig.0445 .0484 .0458 .0324 .0376 .0428 .0535 .0411 .0449 .0433 .0394 .0339 .0453 .0487 . the reactance when in non-magnetic conduitis 0.0427 .0420 .0364 .0431 .0500 .0342 .0397 .0501 .0411 .0378 .0350 .0410 .0415 .l Cil 0 it 0.0378 .0416 .0424 .0365 . and when in magnetic circuit is 0.0333 .0430 .0470 .0402 .0833 = 0.0398 .0487 .0353 .0321 . Thus. 9-3.0473 .0316 x 1. 0' 80 m 15" a .0372 .0345 .0447 .0480 .0322 140 .0455 .0502 .0503 .0329 .0358 .0416 .0359 .0517 .0473 .0466 .0475 .0359 .0382 . If the conductors are part of a multi-conductor cable with fixed spacing.0469 .0445 .0482 .0449 .0356 .0390 . multiply the tabular values in the left-hand section by 0.0400 .0403 .0375 .0366 .0568 .0453 .0315 125 .0316 ohms per 1000 ft.0475 .0379 .0317 .0407 . Whether or not the capacitive reactance is of such amount that it should be taken into account for calculation of voltage drop and regulation is readily detemlined by Eq. hen rys C = Shunt capacitance of the conductor to neutral. 9-10 will affect the results significantly. ampacity will govern.684 in.5.insulated aluminum conductors circuit potential is a factor that influences voliage drop and regulation in long runs of heavily insulated high-voltage cable. 0. As noted in Appendix 8-A. Fig. 9-3 and dividing by 377. however.528) = 0. Approximate methods of combining them for voltage-drop calculations are em ployedbased 'oii-lumpli1g the total capacitance at one or more points of the line.684/0.. conductor diam. The capacitance is obtained directly from the nomogram. A range of values for various insulations is in Tables 8-1. 0. and ~4. in· ductive reactance. (Eq.. noting however. X _ _ __ log. 19-str'ands. For high~molecular~weight polyethylene a value 2. that tlle microfarads so obtained must be converted to farads before use in Eq. they cannot directly be veotorially added (or subtracted). or nomogram Fig. Eo. is a distri buted shunt reactance. as follows: Coo 0.- [(2 IT f)' L C] (Eq.00736 x 6.o (D/d) (Eq.528 in: outside diam. after multiplying by dielectric con stant. and the corresponding inductive reactance is a series reactance.· No. 9-2). 9·12 Voltage-Drop The size of a conductor for a given installation is gov· erned by the permissible voltage drop or the permissible ampacity. Description of such methods is '" The value Er 6. the shunt capacitive reactance is obtained from the 60-Hz capacitance as follows: X'=- 2" I C". Eq. For most voltage-drop calculations only resistance. and for short runs and large currents. on 60-Hz basis Example. and load power factor have to be con sidered (see Fig. Hz The shunt capacitance C" of a round insulated con ductor with outer surface of the insulation (or shield) at ground potential is a function of dielectric constant and of insulation thickness. 9. voltage-drop often is the deciding factor.426 microfarads per 1000 It.3 is used for estimates and similarly 2. rms amp Z = Impedance to neutral.) I = Frequency.5 is typical of synthetic rubber RHW insulation.9-8) where X' shunt capacitive reactance for stated length of insulated conductor in ohms (it will be half as much for twice the length) C" = Capacitance on 60-Hz basis of the insulation in farads. hence for usual calculations at distribution voltages the capacitive re actance may be ignored. 9-9 eft 0. In long runs. 9-4.9-1O) where L = Series inductance of the conductor to neutral. Rules also are given in NEC for estimating loads where they are unknown at time of installation. as described. which is an approximation of its maximum effect In the large majority of circuits employing alumi num insulated conductors it will be found that no further analysis beyond that indicated by Eq. computed as follows: Vector X + X' = 2"IL -----. On 60-Hz basis.9-9) Dielectric constant of insulating material f D = Diameter over insulation or under beyond the scope of this book. From Eq. ~2.5 X log" (0. 9-10. 9-7. if any d == Diameter under the insulation C" Capacitance in microfarads per 1000 ft. The value. X' will be in meg ohms. 410 AWG aluminum single conductor. Because capacitive reactance.3 for cross-linked polyethylene. farads f= Hz The inductance in henrys is obtained from inductive re actance.9·1I) . The NEC (1981) voltage-drop limitation provides that the size of a conductor in either a feeder or branch circuit must be such that the voltage drop will not exceed 3 % from source to the last outlet in the feeder or branch cir cuit. will not exceed that represented by the combined vector re actance in ohms. "" 6. and that the combined voltage drop of feeder and branch in series will not exceed 5 % from source to the Jast outlet of the longest combination of feeder and branch. it is not often of significance for usual lengths of insulated conductor at moderate voltages.ro. The relation is as follows for a stated length of run (from source to load only): Volts drop where I = IZ = J (R cos 0 + X sin 0) Current per conductor. (If C" is in microfarads. ohms (Eq. and in most cases the capacitive re actance can be ignored.00736 X where E f. insulation grounded shield. they do not include provision for many of. the armor is closer to the con ductor than the conduit wall. . Percent voltage drop 7. From the adjustment factors and formulas of the table. 9-11 volts drop IZ 150 0. 752-72. H. thick (94 mils). Neher and M. These· differences tend to counteract each other in their effect on voltage drop. ohms Q = Angle of lag of current vector in relation to emf vector for load end The load power factor. The ampacity will differ un der other conditions. considera lion should be given to the cost of operating losses when selecling conductor size. Provision is made in both the NEC and ICEA publications for variations of ampacity with ambient temperature. The NEC anip_city ratings are on a simpler basis than those of ICEA. pp. .ot5 X 150 X 600 _ 2. Applying it to the preceding example. Ampocity Ratings 2. Although steel armJr is thinner than the walls of steel conduit.015. X 0.. cos 9 0. Example. f. for this conductor it will vary from 231 amp to 299 amp if it is one of three conductors each in a non-metallic duct bank in earth so arranged that the duct ambient temperature is 20°e.95/277 = 2. From TabJe 9-6 and applicable formula: "V" is 0.60) 13. With steel armors. Also. it is readily adapted to most other conditions. and substituting: Percent volts drop percent) = O. and sin 8 0. 95% pf. H.132 X 50 X 75 X 0. equals cos 9. the rated operating temperature of the insulatio. J. McGrath. pllIi (Power Apparatus and Systems) Yo!. From Table 9·5.085 X 0. them hy tests because this work has already been done for a large range of cable types and installation conditions by committees of lCEA and of the Insulated Conductor Committee of IEEE. For 80% p." 9·13 .95 volts. thus. SO amp.9% = = = + = Calculations of this kind are aided by tables in various forms supplied by wire and cable manufacturers.engineering design as related to cable applications R == Resistance. II contains over 300 pages of such arnpacity values" for aluminum conductors 1< The leading reference as to methods of computing ampacity under various conditions is Tire Calculation of the Temperature Rise and L(.085 ohms per 1000 ft. and percent drop at 7S<lC operating temperature? From Table 9-3. .f.132 Percent voltage drop 0. the ICEA ampacity rating of an isolated aluminum IS-kV. Table 9-6 is a typical short form supplied by The Aluminum Association applying to 3-phase 60-Hz circuits on basis of line-ta-line volts. the variations of environmental conditions.80 600 ft 7.80.= conductor can amun without long-time deterioration of the insulation. expressed as a decimal fraction.0338 X 0. at 75 0 C conductor temperature and 400 C ambient temperature of air is 265 amp. carrying ISO amp per con ductor at 80% load lagging power factor.25 volts per 1000 ft. The insulation is 6/64 in.0338 ohms per 1000 ft. What is voltage drop. 230·115 volt single-phase. when the conductor is suspended in air and there is no wind and no solar radiation. R = 0. No. 75 ft run. or computed from sin 9 = {I-cos:! g)!Ii . 1957.8 (as a 480 Another example of the use of Table 9-6 is below: Three~wire solidly grounded neutral..577 = ---------. A 3-phase 480 Y/277 volt 60-Hz feeder circuit 250 kcmil single conductors with grounded neutral is in aluminum nonmagnetic conduit of a 600·ft run. Thus. at 75°C. at stated temperature. 76 Oct. "V" factor == 0. . or for (0.ad Capability of Cabie Systems. yet not above. The ampacity rating of a conductor is the amount of current in amperes (rms) that·will cause the temperature of the conductor to rise from the stated ambient temperature to. being shown only as two values (I) for single conductors in free air.60. Ampadty Tables are qualified by the ::. The variation from 231 amp to 299 amp depends on the thermal conditions of the material surrounding the duct and the heat-sink effect of the bank in relation to the daily load factor of the circuit of which the conductor is a pari. Conductors for new installations should be selected so that their ampacity rating is sufficiently higher than the actual load to be carried at the start so that ample margin is provided for anticipated load growth. Below this range a 2% increase is a conservative adjustment and above this range a decrease of 5 % is justified.The ICEl. and (2) for not more than three conductors in raceway or cable or direct burial.48 115 Application engineers rarely find it necessary 10 com pute thc ompacity ratings of insulated cables or determine The voltage-drop values from Table 9-6 for aluminum conduit apply without significant error to cables in air or with any of the various kinds of non-metallic closc fitting sheaths or armors. from which sin e can be read from table.6 AWG in aluminum conduit. 4/0 A WG concentric stranded single cable having insulation of 0.035 p. AlEE Transactions. P-46-426 Vol.n under specified conditions that affect the rate of heat emmissivity. :he values for steel conduit of Table 9-6 also may be used for sizes 1/0 to 400 kcmi!.' The previously mentioned ICEA Publication No.. (the) current carrying capacities are in no Sense fixed standards or ratings. ohms X = Series inductive reactance. Then from Eq.Latemem Ampacity of Insulated Conductors The kind of insulation that surrounds a conductor de termines the maximum continuous temperature which the that they "re-present the conservative views of engineers based on operating experience and laboratory work and are intended as a guide to assist operating engineers in selecting cables for safety and reliability . 05 .~ d.94 0. I 003 D. 0.2 ?. Nomogram for 60-Hz capacitance across con ductor insulation for ]000 It length after immersion in water lor one hour at 25'C. The nomogram.-.E -".5 6 5 4 0.l w 15 10 !! 113 - 0.429 microfarads per 1000 ft. Note: The capacitance Cal.insulated aluminum conductors 10 Co -3 1.6 0 u 0.078 in.01 8 10 6 Fig.8 0 to 0z u aD. insulation thickness. ~ r 0 D. on w z II. intersection wi. is -'" 0.5 . if any. 0. above.-- -.10 8 -.06 0.) w -- ------- lOll ISO 10O )00 0.528 in.01 10 1l0) ).01 5 1] Q.1 QOi z 25 30 40 :l ::> on 0.S 114 D. . dielectric constant Er = 6.5 0.0 45 0.4 0'> . in microfarads per 1000 ft is obtained by multiplying tbe scale value of Cn x dielectric constant Er• 6O-H~ 9-14 Example: For 4/0~19 cable dia..--.5 0. 0. = . is a ready means offinding the capacitance C" when dielectric constant is known. not the thickness through an outer jacket or covering.'0 6 J I 9 10 118 .5..o.1Iti 4.Q2 •5 0.-- D.th middle line shows 66 X 1()-3. The insulation thickness used when applying the nomo gram is the thickness from conductor surface to the in sulation shield. 9-4.05 D. which multiplied by 6.. Multiplying factors are included for calculations of voltage drop in single·phase Circuits.042 .028 .023 .485 .0085 .014 .048 .012 . and for single·phase or 3·phase circuits to neutral.075 .0097 .016 .016 .012 .010 .099 .049 .054 .015 . NOTES: (a) For single-phase line-lo-line voltage drop.017 .380 .322 .0069 .204 .485 .018 .388 .054 .026 .034 .0081 95 ! ! I i . % VOLTS DROP X LINE TO LINE VOLTS RUN DISTANCE X AMPS.211 .0084 .135 . of Run ALUMINUM CONDUIT SIZE AWG LOAD % LAGGING POWER FACTOR Or kcmil 12 10 8 6 4 2 1 I/O 2/0 3/0 4/0 250 300 350 400 500 600 700 750 NON· MAGNETIC AND : MAGNETIC • : CONDUIT 70 80 90 .024 .032 .052 .176 .024 .011 . multiply the "V" factor from the table by 0.218 .030 .017 .084 .533 .0082 .029 .011 .0063 .053 .011 .022 .125 . 80 90 .036 .023 .022 .034 .010 .0095 .016 .323 .0064 .023 .433 .132 .051 .018 . (bl For single.0072 .or 3*phase line-to-neutral voltage drop.027 .013 .305 .012 .016 .041 .012 .043 .016 .015 .013 .101 .0078 .014 .0087 .0069 .027 .203 .0055 STEEL CONDUIT LOAD % LAGGING POWER FACTOR 70 .' I 9S 100 de .010 .0060 .014 . 9·15 .025 .243 .0091 .0078 .012 .013 .035 .0068 .0086 .044 .013 .012 .080 .022 017 .0072 .435 .065 . "V"-Volts Drop per Amp per 100 Ft.033 .085 .241 .533 .012 .0053 APPLICABLE FORMULAS: % VOLTS DRbp 'V' X AMPS.0056 .0094 .17'1 I .022 . Voltage drop requirements for feeders and branch circuits are given in NEe 1987 articles 21S-2(b) and 2J()·19(a) respec· tively.043 .014 .086 .028 .153 .336 .034 .274 .010 .0051 .113 .035 .081 .244 .102 .017 .0091 1.0087 .0068 .013 .211 .510 .062 .027 .084 .010 .010 .577 using line to neutral voltage.0076 .012 .engineering design as related to cable applications TABLE 9·6 "V" Factors for Calculation of Line·to·Line Voltage Drop for 3·Phase 60 Hz Circuits or Direct·Current Circuits.014 .047 .0076 .012 .0081 .018 .509 .0090 .0089 . 114 .014 .043 .043 .017 .0093 .035 .011 .035 .011 .039 .0094 .039 .053 .193 .066 .156 .0094 .0077 I .136 .020 .016 . X RUN DISTANCE(ft) LINE TO LINE VOLTS RUN DISTANCE "V" FACTOR % VOLTS DROP X LINE TO LINE VOLTS ·Y'XAMPS.040 .155 .018 .010 .195 .013 .072 .336 .155. multiply the "V" factor from the table by 1.132 .0075 ! i .011 . All voltage drops are valid up to and including conductor temperature of 75°C.0049 .023 .025 .381 .028 .125 .008 .031 .616 .0075 ! ! 100 .274 .018 .014 .013 .013 .027 .012 .0085 .015 .043 .0090 . Emergency ratings have come about through long time experience in cable operation. Among the special conditions relating to ampacity of insulated conductors are the following: I. Ampacities for primary underground residential dis tribution cables of two-conductor concentric-neutral type. Table 9·7 lists emergency overload tempera tures for the most-used insulations.). and about 12% higher at 15 kV. etc. A table similar to Table 10-9. This table also includes a section for such cables in air at 400C ambient. Appendix 9-A herein explains the lCEA tables and how to use them. Insulated conductors are often grouped in ducts so their insulated surfaces touch. A working knowledge of all of these lCEA ampacity publications is almost essential for proper selection of insulated cables of various kinds. Short-Circuit Ratings The subject of short-circuit currents in insulated cables thal flow thruugh metallk shields or sheaths if the insula tion rails or if the shield is used for relaying currents is treated in Chapter 12. except it is for 85'C and Butyl-rubber insulation (ICEA Pub. When cables are buried in earth or are in duct banks. The reason why it is not usually feasible to compute cable ampacities in the simple manner used for bare con ductors js because there are many more factors in the calculation than simply the ac rcsistance of the conductor and the rate of surface emissivity that determine ampacity of barc conductors. The adjustc ment factors differ by not to exceed "I" in last place. eddy currents in shields. the application engineer most likely will obtain ampacity rates from the lCEA P·53426. Ampacity tables for these have since been issued as follows: A. Heat originales outside of the conductor from energy losses in insulation. and this may differ for different layers (jackets. 4. unless the NEC or the supplementary ICEA tables are suitable.insulated aluminum conductors that have the usual types of insulation and that are installed as cables in the various kinds of environments found in today's power systems. which in turn depends on the daily load factor of the circuit and On the specific heat of the earth. the tabular values may be adjusted for variation of insulation power factor. and also the heat transfer rate depends on the heat-sink quality of the environment. and when in duct about 9% higher ampacity. II tables. for many applica tions of insulated conductors. 9·16 '5. This table shows values for buried cable of about 5 % higher ampacity than the values for PE insulation in Table 10-9. not only for directly tabulated values but also for variations from the conditions for which listed values are shown. They are subject to revision as better thermal performance is de veloped for insulating materials and more reliable field data are obtained. The Constants that are listed in the tables provide meanS for finding ampacity for any other ambient temperature. the ambient temperature differs from that of cablcs in air. there is no arc burn-down effect. Since most deteriorative reactions are enhanced by elevated temperature and are accumulative with time. or they touch a grounded metallic sheath. armor. Chapter 10 of this handbook contains ampacity tables. The values in this table relating to aluminum are shown in Tables 10-9 A and 10-9B E. The insulation has thermal resistance. so heat-transfer across an assembly of such conductors is not easy to evaluate. (also hysteresis in steel parts). are those that occur in apparatus Or switchgear. hence only the increased current resulting from the short circuit flows in the insulated conductor. largely based on these ICEA tables. also inductive and proximity effects often arc prominent because of close spacing. etc. For instance. sheaths. S-19 81. In similar manner. P-54-440 or the lCEA VoJ. 50 such may not be considered in NEC installations. A more recent publication addressing URD/UD Style Cables is ICEA P-53-426. For asbestos in sulations that have IIOOC operating limits (Types A VA and A VL) consult manufacturer. however. 3. 1966 revision). polyethylene insulated and XLPE in sulated. it is recognized that certain short periods of overloading are not only reasonably safe but inevitable in service. The values for air installation a<e about 15 % higher at 5 kV for cable only. for direct burial and for installation in duct at 20°C ambient. Note that the NEe does not recognize emergency over load operation. A few cable types do not have ampacities listed in the above-mentioned ICEA publications. sheaths. operating temperature. etc. For these reasons. The ICEA rated temperature limits (also noted in Table 9-7) that an insulation can anain during and im mediately after interruption of such a short-circuit cur rent are as follows: . Emergency loading periods are limited to values given in AEIC and lCEA Standards as applica ble. taken in part from ICEA Pub. daily load hctor. The radiation of heat from insulated conductors placed singly or as a multi-conductor cable within a duct or conduit is influenced by the distance between insulation surface and inner duct wall. 2. emergency overload ratings always specify both a tempera ture and d"ration limit and a limit on the total numbcr of emergency events. Emergency Overload Ratings While maximum conductor operating temperature limits are based on maintaining insulation stability indefinitely. S-61-402 2nd ed. the tabular ampacities are based on a 200C ambient for earth-burial or duct-bank installation and 400C ambient for suspension in air or in metal conduit. :\1any short-circuit currents in in sulated cables. Jan. The ampacity values for aluminum portable cables should be obtained from the manufacturers. after the fault has cleared and the conductor cools. and varnished cambric 200 c C Cross-linked polyethylene and EPR 250 c C account the rise in temperature of the insulation after the fault has been cleared and the heat conknt of the con ductor tr3nsfers to the insulation. and 250~C maxi mum -.(ircuit Normal Insulatmn load Temper Emergency-Load Temperature'" "1!'re . the basis is the some . 8-3 and 84 Short. Special analysis is required if the circuit is protected in part by current-limiting fuses. than 30 '5&. 9~5j the intersection of vertical line above 4/0 and diagonal line for 30 cycles is at 10.. 9-5. see lCEA P-45-482.7 to 53. if maximum operating temperatu:"e before fault is 75"C? By reference to Fig..17 60 70 75 85 85 95 90 95 105 100 130 (over SkV) (0-5kV) (5001. Or 250°C as the case may be). yet not so high that the insulation is damaged.900 amp for 250~C The diagrams are based . Polwlny! 60 chloride 75 iMrmoplastic polyethylene 75 95 90 (0-5kV) (SOOl·35kV) Rubber-insulated 53.onductor temperature. Example: Assume the maximum falllt-clcadng time is 30 cycles.I> that employed for short-circuit calculations of bare-con ductor as described in Chapter 6. 200 0 . but they also take into Q j TABLE 9-7 Abstract of ICEA Standards for Maximum Emergency-Load and Short-Circuit-Load Temperatures for Insulations Listed in Tables 8-2. on basis of 75 0 C operating temperature prior to the fault. including allowance for One reclose of the imerrupling device. Figs. rubber-like.engineering design as related to coble opplications For thermoplastic insulations (polyvinyl chlorides and plain polyethylenes) 150 c C Rubber.. What allowance for fauH current can be made for :1 single 4/0 cable insulated for 150°C. and 9-7 show the time in cycles (60 Hz basis) that a short-circuit current of stated value can be withstood. That is.:..) • 0 I I c 150 200 250 polyethylene and EPR "'For short circuit capability of c cable shields. 9~6 it is 12 500 amp for 200 C and for Fig 9~7 it is 14.skVI (over 15kVl (0·5kV) (5001-15kV) On Table 8-2 80 85 Thermosetting cross-linked 90 85 95 Temperature of Cable Conductor : (less.m the assumption that no heat is emitted from the conductor metal during the short time that the fault current flows. 200°C. the insulation slowJy increases in temperature to some point that is lower than the peak temperature of the conductor itself (150 0 . 9-17 . . 9-6. Also assome that the fault oCcurs sufficiently far from the con ductor being considered so there is no arcing burn-down effect or insulation breakdown that causes current to How through shield or sheath. The upper temperature limits established for the various insulations not only reflect the ahility of the insulation to withstand the high temperature. without its temperature exceeding the specified upper limit.400 amp for lS0"'C Aho for Fig. that is. <-c.J. SECONDS T. Short circuit currents for insulated cables (150·C maximum).2 10 CONDUCTOR: ALUMINUM INSULATION: THERMOPLASTIC [IJ Ii V/ / / d:l v CURVES BASED ON FORMULA .v..0125 Log V [T+228] T: +228 - I = SHORT CIRCUIT CURRENT. AMPERES /' 8 I WHERE A = CONDUCTOR AREA. c.4 V V / / V / /~(>.V".3 6 2 4 I/O 2/0 3/0 AWG 4/0250 350 500 KCMIL CONDUCTOR SIZE Fig.S / ~ "".v" ".. V / / " v" . 71c TI = MAXIMUM SHORT CIRCUIT TEMPERATURE.6 .5 .8 ./V ~ [% "/ ~ // / V/ /V V Ii // V/ t = 0. ". / //V "V V //V / / / 20 5 /' / / / 50 ~ V / / 750 I r- 1000 . / gJ 8 I f- 6 5 / '= o a: (3 2 f a: ~ (/) . 9-18 V V // / VV V /V / " / / ". 9-5.<-y / / / / V V V V/ / "V V / V' V V / / V (p~} / .CIRCULAR MILS t = TIME OF SHORT CIRCUIT.' / /~~~ V v"..b \) V "'0 /:V/ "/V/.insulated aluminum conductors SHORT CIRCUIT CURRENTS FOR INSULATED CABLES 100 80 / 60 / 40 / 30 (/) w w " ::..." / I !zw / / / V / V / / / VV ~// / /V v~//~V v~ _.Y t.<-c. a: « 10 o" ./ / VVV/ ~~v a: a: ::::J / V/ 4 13 3 V . 150·C .<-'. = MAXIMUM OPERATING TEMPERATURE. / /' / V/ /// / v""''> / V / / V / v' ". .8 ..OJ2S Lo tT2+228j A 9 T1+228 V/ // WHERE // I V/ = SHORT CIRCUIT CURRENT./ /' I ~ ~ // CONDUCTOR: ALUMINUM INSULATION.RUBBER.200·C - . / V// ~ / V / / VV/ / 20 ~ 5J: / V V y / V Y V V V / / V / / L V /' / / / / VV / Y V /' 40 . / . V /' / r V v 2 ~ (J) .0. / .3 .. ::.. T~/ / ./ //.I V /VvV (J) ill I V V V/ / /V i/'.. v~ 6 5 a / /. ~ o 10 ~ 8 !z 4 a:: 3 t: ::::J o a:: 13 .2 I 10 8 6 4 2 I/O 2/0 310 4/0 250 350 SOD 750 1000 KCMIL AWG CONDUCTOR SIZE Fig.I / / ...> ~<:) / t.6 .. 9-19 .0 ". 9-6. V <8 .. ~ V / / 1/ / V / .I / .AMPERES A: I : T1 : T2 = V CONDUCTOR AREA..J:.engineering design as related to cable applications SHORT CIRCUIT CURRENTS FOR INSULATED CABLES 100 80 I 60 50 i 30 a:: UJ c. 7S"<: MAXIMUM SHORT CIRCUIT TEMPERATURE. .. Short circuit currents for insulated cables (:WO·C maximum).CIRCULAR MILS TIME OF SHORT CIRCUIT. VARNISHED CLOTH CURVES BASED ON FORMULA / eJI:0. PAPER.5 ~ / / / / / V/ / V / V ! .". SECONDS MAXIMUM OPERATING TEMPERATURE.I..''V tP0 d ~ V/ ~VV~1 / v: V .b~f-'P 0"'~/ " 0" if> .. insulated aluminum conductors SHORT CIRCUIT CURRENTS FOR INSULATED CABLES f!]2 t = 0.6 // LA I [TI +228J [T. 9-20 750 1000 . CIRCULAR MILS TIME OF SHORT CIRCUIT.3~--+---+----r-----T-~-r--r-I-'--r-Ir-.~--+_--+_- A= t = TI= T2= CONDUCTOR AREA.5/ I = SHORT CIRCUIT CURRENT. SECONDS • MAXIMUM OPERATING TEMPERATURE.250C .-~r--r~-rrr~ . Short circuit currents for insulated cables (250·C maximum).2~ 10 ____ ~ ___L_ _ _ _ _ L ___ iii ~_~-L I __ I/O ~~~ __ ~L-~L-~-L-LU-~ 210 310 4/0 250 350 500 KCMIL CONDUCTOR SIZE Fig. +228 WHERE V / .4fof----.0125 log . 9-7.8 .AMPERES .75C MAXIMUM SHORT CIRCUIT TEMPERATURE. Ambient temperature: 20'C in duct or for direct burial. 40'C in air or exposed conduit. Also a two-conductor cable has the ratings of a triplexed cable if the conductor assembly has an overall sheath. the ampacity tables are grouped according to kind of insulation. Space does' not permit inclusion of the tables them·' selves. comprising three insulated conductors in equilateral ar rangement held in position by tape or by spiraling around a neutral. were reissued unchanged in 1978. 85. No. an abstract of the tables is included along with an explanation of their use. by a circular sheath which gives tbe assembly the appear ance of a round cable. 9-21 . 65. See also Note 1. and in duct-bank arrangements as described for single-con ductor cable with the addition that One cable can be in stalled in a single duct.25 kV Operating temperature: 60. The inclusion of a neutral conductor in triplexed or three-conductor cable does not affect the ampacity rating. 70. many of the l-kV ratings provide comparative values that are useful. etc. that contain abstracts from the tables are reproduced by permission of the C:OpyrigtH owner. Although most of the space in the book is devoted to cables above the 600-volt NEC range. six cables in a 6-duct bank. kV ratings. in conduit exposed to air. because some combinations are not practicable. and one or two cables may be directly buried. All ampacity ratings are those of One conductor of a triplexed or three-conductor assembly. originally pUblished in 1962. and 90'C where applicable. However.) Single conductor cable: in air. Insulated Cable Engineers Associalion (formerly IPCEA). 75. even where NEC requirements are mandatory. comprising three insu lated conductors in equilateral arrangement. These tables. three cables ciosely adjacent directly buried. the result of years of research by leading authorities (see footnote on page 9·13). method of instal lation. Cable types: Single-conductor cable. Installation Methods (See Figs. all surrounded "The description of the lCEA~IEEE tables herein. P·54-440. and conductor operating and ambient temperature. For aluminum conductors. 1979. ICEA. Aug. Three-conductor cable in same arrangements as listed above for triplexed cable.APPENDIX 9-A Explanation of ICEA·IEEE Tables of Ampacity of Insulated Aluminum Cables For Various Conditions of Installation Based on 1978 Edition. The tables for aluminum cables comprise 317 pages.·· Triplexed cable: in air. six cables in two-circuits directly buried. IEEE Pub. Notes: L ICEA-NEMA has since published additional ampactty tables for N'o*conductor concentric-neutral aluminum cable for URD •• Ampacities for cables in open-top cable uays are found in ICEA Pub.8. three cables in a 3-or 4-duct bank. Sets of constants are provided that enable adjustment of the ampaciry rating for conditions differing from those for which the table is compiled. This cable is not expected to be installed singly in a steel conduit. P~46·426. Not every classification is inciuded in every group. 80. and the originating bodies control their distribu· tion. triplexed cable. Illustrations of many cable types are in Cbapter 10. The following are princi pal groups for thermosetting or thermoplastic insula tions. three-conductor cable. S-t35'" A working knowledge of these tables is almost essential for economic studies of alternative proposals of cable se lection because they embody comprehensive ampacity temperature ratings for most of the types of cables and methods of installation currently used. No. 15. nine cables in a 9-duct bank. Voltage: 1. 9A-1 and 9A-2 for spacing. and elsewhere in this publication. Pub. See also the ampacity tables in Chapter 10. Arrangements of buried cables. (as well as for air installation). and 9 cables in underground duct.covered and insulated wire and cable 19"X 19"DUCT BANK ( bJ (c) 33. or 3. This type of cable has spiral bare e~terior round~wire copper neutral.4" DUCT BANK NOTE -H INDICATES THE HOTTEST CABLE (d) Fig. 6. as basis for ampacity calculations. 3. 9A-2.-wire or three-wire single-phase circuit. with or wIthout an extra.4" X 33.and high-pressure gas-fiHed and oil~fmed cables of the kinds in limited commercial or ex~rimental use with aluminum conductors. suitable for direct earth burial (see Table 10-9). . 9A-1. as basis forampacily calculations. ~i&W~ 36 11 0i '0 24 BURIED 3 CONDUCTOR CABLES OR PIPES BURIED SINGLE CONDUCTOR CABLES 101 BURIED TRIPLEX CABLES lei Ibl NOTE-H INDICATES THE HOTTEST CABLE Fig. 2. 9·22 three-wire 3~phase circuit. The term "one-cir¢uit" refers to two or three cooducfors of a single circuit.conductor for neutral. The ICEA-IEEE set of tables also includes ampacity ratings for low. 3. that comprise a two. Arrangements of 1. earth of RHo. 9A-2 and substituting: /' = 1--------------- + 70 252 X ~ I 55 . When ambient temperature only is changed.035 X 4. 9A-l becomes /' IT.79 228.7.Delta TD (Eq. and LF differ from those used in 9·23 . and 120C°--centimeters per watt (CO-em/watt). RHo. thus. DeltaID amperes T. Thus..15 . consideration must be given to futnre load factors during the expected life of the cable. T. = Conductor T.79 X = 0. CO as listed. that is. .1 + 55 232 amperes Interpolation Cham jor Variation of RHO and Load Factor If the values of RHO. . TD' = 0. values or for load factors. initial conditions may indicate that the am pacity corresponding to 30LF is satisfactory. These adjustments are obtained by use of the curves of Figs.Delta TO' 228.-60.-. The in creased ampacity for low load factors is the result of the heat-sink property of the earth surrounding the conduc tors or the duct block. these values vary in direct proportion to insulation power factor. the ratio of average load to peak load according to customary practice of electric power utilities when determining average load factor.035 power factor (of insulation).1 + T. 0. 75LF.-60 thermal resistivity transmits a given amount of heat at a lower temperature than will RHo-l20 earth. Delta TD factor is as listed. If the PR loss for one day is obtained from such a curve.020? 0.20 0. Associated with load factor is a Loss Factor... The lining of the duct is non metallic.90. For cables of equal dielectric constant. 90'.= 225 amperes 2. 75LF.. it probably will be about 33 percent of the 12R loss if the load were constant Empirical loss factors corresponding to the various assumed LF's are 0. and T' c is same. a typical load curve of 50LF will have peaks and Valleys. Examples: L The 4/0 ampacity under RHO-90 and 75LF conditions for 70 e C conductor temperature and 20"C ambient. Thus. 9A-l) AmpaCity under new condition... What is it a~ 30"C ambient? Here apply Eq. 9A-2) It will be noted that Eqs. but perhaps the cable should be selected on the basis of 75LF or lOOLF because during the period of load growth. 1'=252 X i -.00 loss factors for 30LF. The three right-hand columns of Table 9A-1 are head ed DELTA TD for 0.0.-. Eq.-60. and the duct bank is be low ground as shown.-90 and RHo-120 signify Earth Thermal Resistivity in terms of 60°. under new conditions. 9A-l(b). T. and l' = (Eq. The three cables in duct bank are ar ranged and spaced according to Fig.1 'V 70 .engineering design as related to cable applications Description of Typical Section of IeEA-IEEE Ampacity Table For explanation of these tables. from Table 9A-l. . = Ambient temperature. and -120 conditions. V------ -~ amperes X Where I = Ampacity as listed. and JOOLF sig nify Load Factor.33.15.9A-2. if dielectric constant is 5.. a typical section is re produced as Table 9A-l from top of page 167 of Vol. is temperature. 9A-3 and 9A-4. . The designations 30LF. The cable of example 1 (before adjustment for change of ambient) has an insulation power factor of 0. T. 0. Thus. in which the cables in each duct are Single. II on aluminum conductors. suitable load dispatching may tend to flatten any peaks that exist early in the life of the cable. same. T'.53 X 228. = I . respectively.02 X 5. In selecting the LF value.:. The designations RHo. Where the earth thermal resistivity is unknown. 7'..035 and insulation dielectric constant of 4. and lOOLF values.7 Applying Eq.1 T'. as described on the curve sheets. 9A-I and 9A-2 contain no provision for adjustment for variation of RHO.5 and power factor is 0.Delta TD 228. 50LF. ICEA suggestS using the RHo. hence a cable in a duct buried in aggregate or earth of RHO 60 resistivity will have a higher ampacity tban if the duct were buried in earth of higher thermal resistivity.-90 values. Load factor variations of ampacity are not shown in the tables that apply to cables suspended in air or are in conduit exposed to air (see Table 9A-2). Any value of ampacity I appearing in the table may be corrected for a change of operating or ambient temperature or of insula tion power factor by use of the following expression in which the prime mark indicates the desired new values: l' = I IT'. and T'.53 0. . The Delta TD values signify dielectric-loss temperature rise. as load increases to a peak. applying to RHo. 50LF. and 1.625. under new conditions. and Delta TD' is same under new conditions (Delta TD varies ouly when there is a change of dielectric constant or power factor of the insulation). the temperature of the conductor does not rise as rapidly as if it were exposed to air.T. accQrding to the data accompanying the ICEA tables for rubber and plastic insulation. Co as listed. What is the ampacity at 55~C for conductor. is 252 amperes.5 The adjusted Delt. with lS"C ambient.... 222/277 LF~l00%. and those of Fig.68 0. 9A·3 at RHO·140 and LF-60. Trip/exeQ vs Three-Conductor Cable: A triplexed cable. RHO·SO eOND.72 0. from table = 222 0.66 0.90 0.63 0.79 0.0350 PF AND RHO 90 120 60 I I ALUMINUM CONDUCTOR CONCENTRIC STRANO I I 3 CASLES IN DUCT SANK 15 KV . 837 1 .10 0. or directly buried. the ampacity table is in simpler form than the one used for Table 9A-1. The desired ampacity for RHO-J40 and LF-60 is 0.91.49 1.84 0. Ampacities for all listed voltages are in a single section of the table for ~ given temperature. FoUowing the value vertically to the upper family of curves at intersection of 9-24 805 891 969 1040 585 860 816 : 725 885 1 784 ..71 0. SIZE 30LF I50LF 175LF 1100LF RHO·90 30lF I 50LF 175LF l'OOLF RHO·12O 30lF 150LF ! 75LF Ii00LF DELTA TO FOR .70 0. the charts of Fig.04 I 0.41 = ¥-HO-50 and lr:. Example: 3.37 1.60 and LF-50.80 Enter lower section of Fig.57 0.. 739 L~J 448 523 588 645 695 740 1.26 1. the assembly may be taped to a messenger or grounded neutral as a preassembled aerial cable or in duct.02 1.80. the ampacity rating of the triplex cable is the . 9A-2(c) comprises three single conductors arranged equiJaterally as shown. For both sets of charts the upper family of curves shows variation of ampacity for LF-lOO in terms of I" the ampacity for RHO-60 and LF 50. is the ampacity at RHO-120 and LF-IOO.19 1.93 1. 9A-3 may be used for inter polation Or extrapolation for values of RHO and LF for cables installed in duct banks.20 1.01 1. The base values and ratio are as follows: 11 = ampacity at RH0.70 C CONDUCTOR 20 C AMSIENT EARTH 2 144 165 140 160 134 153 127 145 143 153 137 157 129 • 121 138 148 I/O 2/0 3/0 4/0 190 218 250 287 184 210 241 277 175 200 229 263 166 189 216 247 188 215 247 284 180 206 236 271 169 193 220 252 250 350 500 750 317 389 463 617 306 374 463 289 272 330 404 509 313 384 476 607 298 364 449 570 277 337 : 414 522 1000 1250 1500 1750 2000 734 536 927 1010 1086 697 793 877 598 675 743 804 858 720 820 908 989 1062 674 765 845 918 614 557 694 : 628 764 689 744 827 793 884 589 353 434 549 954 648 734 810 878 1023 940 963 141 162 134 154 125 143 116 132 0. : : : : .29 1. The intersection lies on curve for RHO-50 at lOOLF.79 0.15 1. Fig. the tables.insulated aluminum conductors TABLE 9A-' Ampacities of Single Conductor Concentric Stranded Rubber Insulated Cable in Ducts . The lower family of curves shows the relationship between RHO and LF which will give substantially the same ampacity as the indicated value of RHO at LF-IOO.95 708 653 1 See text for explanation of Delta TO values.36 1.10 1.99 1.55 0.60 0.75 0. as when cables are in duct bank or directly buried.//" where I. Because the radiating insulating surface exposed to ambient temperature is greater in a triplex cable.79 0. Each curve is designated for a particular ratio 1. A thrce-conductor cable.83 0. the corresponding value of F (at left) 0.91 x 277 = 252 amperes IS Tables tor Installation in Air or in Conduit Exposed 10 Air If there is no heat-sink effect..68 0. The sample shown as Table 9A-2 is for Triplexed rubber-insulated cable in air. except that the assembly of three conductors is surrounded by a jacket or sheath to form a cylindrical exterior. Fig.56 1.71 158 180 205 234 186 213 244 280 I 176 201 230 264 164 186 213 243 151 171 195 222 0. 9A-2(a) is similar.22 1. Assume that it is desired to :find the ampacity of tbe 4/0 cable of Table 9A-l at RHO-J40 and LF-60.61 0.41 1. 9A--4 may be used for directly buried cables.!ll 0.64 0.53 1. 277 am peres 1'1 = ampacity at RHO-120 and amperes Ratio l.86 0.75 0.12 1..89 256 311 380 476 309 379 469 597 291 355 437 553 267 324 397 499 244 294 359 0./!.. from table. 98 65 85 I 350 500 750 254 315 392 502 595 202 :::.19 0.23 0. These relations following comparison: AmpaciJy for 1 kV 4/Q AWG cable at 60f>C are shown by the WD RI = Dielectric loss. including skin and proximity effects only.13 I I ~~: 395 504 594 318 394 500 589 .81 155 178 204 235 0.87 0. The increased am pacity for directly buried installations is a factur that should be evaluated when the economics of URD for a given installation are considered. and include the following values: PD greater. thermal ohm- Amperes Triplex 3-CoruJucror it = Rl Ca&le RSD = Thermal resistance between cable and duct IVall.23 0. 9A-2.24 0.52 0. An average 40·C ambient for air is suitable for initial ampacity estimates. A lower power factor may be expected with new cables. if any.engineering design as related 10 cable applications TABLE 9A:2 Triplexed Concentric Stranded Rubber Insulated Cable In Air-Isolated Circuit 40 C Ambient Air CONDo SIZE . if used. are assumed for each conductor of triplexed cables with rubber and thermoplastic insulations. These are all for 75°C.05 The Delta TD factors are used for adjustments when there is a change of dielectric constant. thermal ohm-feet Cable 20"C ambient In duct bank Outside diameter. This assumed power factur applies to this insulation after some years of use under average conditions. 9A-1. and this value also applies to cables with neoprene or plastic jackets. inches Directly buried 191 240 173 227 40"C ambient In air In conduit. Short-circuited sheaths or shields. or pipe (R. Supplementary Constants The set of ampacity tables also includes supplementary tables of design constants that can be used for computing ampacity for non-tabulated conditions.03 1. A similar average for under ground duct bank is 20°C ambient.26 0.44 0. sheath or shield. subject to adjust ment by applying Eq. See text for further explanation.50 0.83 0.94 0.46 0. are as sumed with rubber.5. The insulation power factor for rubber and thermoplastic insulations is taken as 0. are available in ICEA Pub.). Construction oj Cables Used as Basis jar A mpacity Tables: Metallic insulation shielding is a part of rubber and the""oplastic cables listed as 8-kV and above.61 0.91 0.16 0. including the effect of circulating current losses.0350 8 6 4 2 44 59 78 106 112 115 1 123 129 133 I/O 2/0 3/0 143 165 192 149 153 175 4/0 250 172 198 229 224 251 312 392 512 1000 1612 135 0. = Thermal resistance of insulation.89 260 0.19 0. Depth for direct burial and duct banks are as in FIg.54 0. They 9-25 . Open-circuit sheath operation is assumed for single-conductor cables with metallic sheaths. An average Dielectric Con stant for the rubber and thermoplastic insulation after years of use is assumed as 4. installed in separated ducts or directly buried with separation.45 0. Note: The Symbol resistance ' R with line over top designates thermal The values in these tables of constants are helpful in more ways than merely for computing ampacity values. or air for cable in air (R.). Rae = ac resistance of the conductor. and pipe to losses in the conductors.26 0.85 0. Ampacity values for short circuit sheath operation of single-conductor cables.22 0. and asbestus (AVA) insulations.035 (3Vi %).17 0.48 0.21 0.56 0. microhms per foot. but use of the higher value is recommended for estimates. QS Ratio of sum of the losses in the conductors and sheaths or shields to the losses in the conductors OE = Ratio of the sum of the losses in the conducturs.20 0. The insulation thick nesses for cables with rubber and thermoplastic insulations are according to ICEA S-19-81 (Fourth Edition revised) and S-61-402 (Second Edition revised). 1.49 0. watts per conductor foot = W.59 0. Nonmetallic jackets. in air 174 144 149 133 Ambient Temperature: It is assumed that there is no wind and no solar radiation. thermoplastic. Ampacities for lead-sheathed rubber and thermoplastic cables assume metallic shielding. but adjustment for other values may be made by applying Eq. 1 VOLTAGE kV 8 15 VOLTAGE kV 8 15 25 25 AMPACITV DELTA TO ALUMINUM CONDUCTOR CONCENTRIC STRAND CONDUCTOR TEMPERATURE 75°C INSULATION P F . 9A-j and 9A-2. P-53426.21 0. Interpolation chart jor cables in a duel bank. 50 LF. = ampacit . desired ampacity = F X Ii' 9·26 = ampacity jor RHO-90. 100 LF.' I. 9A-3.insulated aluminum conductors :I : i i I ~ _ __ -_~ I n '0 20 30 no 60 10 ro iO 10 10 HO iO iO 11 :: In dO RHO Fig. RHO-nO. I. .. .. i" " '" "" ''" " " "l '"I" r-...... l"'l"" . ......""'... " ..". .....i · I ••5 .i o.... ... r......... t'-........ "" " I : 60 '. .. ... ..... 9A-4."' ...0... ....... o.... l" r-. --r- - - 1... -.....'---l~ ...... --.. 50 LF....... 190 100 Fig............ 10 20' 30 40 50 0 . .. r- i ...... 1\ ....I 0 j .. \ 1\ 1 5 0 i"--.. .... " " r.. ~ .."' "... :--.. -..".....00 1 i .. --... 1\ ........... "'-...['-. -........ 5.. .... ... """..5 0 ........'...\ \ 5 1\\ 0 ~ \ 5 \ o! \ \ \ 1 \ !\\ \' 1\ 5 \ .. i'-" ~ ~ 10 ...''" " "............. \ ~\ :\ 90 -1"' 11ZO 130 I 140 - 150 GO I 10 ~ Q:......-......."............~".. . interpolation chart for pipe-type and directly buried cables h = ampacity for RH0-60. ..l"'... . \ o......" " ... .."". ~ \..r- r .... I ..... ~ 1 10 0 : ~ I 0 OJS -~ i"--......... 1... \ 0 ... 130 "0 150 " " . ii\.. r-.95 : T- ... .. .... ''1-- " 160 110 -- 1 180 . " i'.. .-' r--: i.... ! 10 IfJO \ !\ \\ :-..... ....... 80 90 100 110 RHO 110 .. .J.............. 100 LF... '"\1. '\...."" "" "" " "" .. -."' 0 ' '\ .... ".................. ~ --..0.i'- r-..... desired ampacity = F XII' 9-27 ...\ ~ ~ o.'\. --. ~ \ \ \ \ 1\ '\._1 r---.......J.50 180 1'90 200 5 " 30 '0 " '"\ ". 5 I .. .. "--.. "-.... i'- " " ..Q65 ...engineering design as related to cable applications 5 1..... • 5 10. I 1 110 '\ ~..... i'-" :--....1.60 O. - I ... r- I I 60' 10 • 80 " 1\ 1\ \\ 1\ [\ i\......5 ~ 0 I 5... I 0 0.90 1--.... i 10 0.. r---.....t'- i \l 50 "" ..85 .. : I I .."" r- ......... 30 !l0 .00 ! -- - "" -- -- r--.. '\..10 .. ...." "' "" r. - .." I I 1 ~~ I .. .. \ . r- - .... -. \ \ 5! r-.....1S --r--..... 1'\... ..::: ~ " "' --.. = am pacity for RHO-l20.... i'- " -.. 1 \ \ : 5~ to 0 : ~ I ~ .. I" I" !' " I ...... '\. ~ ~ .. '\.. conduc!or.58 1.78 .71 .77 0.91 . operating temperature.65 0. From values such as the above.94 .72 .76 0. in air 2l..87 0.74 .71 .63 0.50 "These factors include the effects of Load diversity . For conduits. in steel conduit* 22.70 .70 0. apply the appropriate factor from Table 9A-5 to the ampacity of the identical cable given in the tables for cables in air.41 22. in air same. The ac resistance.75 .63 0.89 0.180 watts per conductor foot for 15 kV.70 0. TABLE 9A-5 ICEA Derating Factors for Cables Where Set _ _ _ _----'S:..79 .. .102 1. * The QE value for conductor in aluminum conduit as an ave' age will be only 0.69 .00 .87 .80 .80 . 9-28 Where cables are installed on ladder supports or in expanded metal troughs. for 1 kV it is 0. in steel conduit * 22.70 .80 0.83 0.87 .72 . of Conduits Vertical 1 2 3 4 5 6 No. (b) For 3-conductor non-shielded cables. of Conduits~Horizonta~ 1.64 0.67 0. this covers groups of conduits in free air.167 3.66 0.insulated aluminum conductors represent the results of research.92 .74 0.102 1. the application engineer oblains useful relationships that might not be evident from a direct comparison of ampacities under the respective conditions.70 0.61 23. both experimental and analytical. (b) For 3-conductor cables apply the appropriate factor from the table below to the ampacity of the identical cable in isolated conduit in air.78 .70 1.72 0. TABLE 9A-3 ICEA Derating Factors for Cables in Metal Conduit or with Armor and Set Spacing No.069 1.00 0.61 1 Coble Spacing Not Maintained Where cables are installed on ladder supports or in expanded metal troughs and where spacing is not main tained: (a) For single conductor shielded or unshielded 3 conductor triplex-shielded.75 0.85 . TABLE 9A-4 ICEA Derating Factors for Cables in Ladder Supports or Metal Troughs with Set Spacing Number Vertically 1 2 3 4 5 6 Number of Cables Horizontalll! 2 4 5 6 3 1.41 23. Example: A lOO)-kcmil 1350-HJ9 aluminum cable of 61-s:trands has de resistance at 20"C of 17.84 0. in duct or buried same.73 .64 0.82 0.66 0.70 0. the ICEA standards pennit derating in accordance with Table 9A-3.112 The dielectric loss in the insulation for all of the above con~ ditions is 0. Condition R~ QS orQE mic:rohms/fl ratio Single condUctor in duct or buried same.001 1. ICEA Ampacity Grouping Factors Where cables or conduit that conlain not more than three current-carrying conductors with neutral are main tained at more than one cable or conduit diameter apart (from surface to surface) no correction of ampacity ratings need be made.34 microhms per ft.B3 0. at 7S"C it is 19. mounted on ladder type supports or supported on hangers.:) and the ratio of total losses to conductor losses (QS or QE) for a cable insulated with rubber or thenno~ plastic for 15 k V.26 1.68 Note: Multiply the .74 0.ampacity of the cable in isolated aluminum or steel conduit by the above adjustment factors.75 21. including skin and proximity effects <R.72 .60 0.61 22. and voltage rating given in the tables for cables in air. relating to single as well as closely adjacent con ductors. values that are difficUlt to find in usual sources.00 0.75 0..76 .62 0.74 . Cable Spacing Maintained Where cables are in metal conduit or are armored and mainlained at between one-quarter to one cable diameter apart under the above noted conditions in air.!::p8cing Is Not Maintained Total Number of Conductors 3 4-6 7-9 10·24' 25·42" 43 and up" Factor 1.93 0.002 Triplexed.70 . is as follows for various methods of installation: lnstallalion.72 0. at a maintained spacing of from 114 to I cable diameter. Where cables are installed in solid metal trays: (a) For single-conductor 9A-5 cables apply the appro priate factor from Table 9A-5 below to the ampacity for three identical single-conductor cables in isolated conduit in air.69 0.68 0.80 0.B1 .69 0. and 3-conductor shielded ca bles. apply the appropriate factor from the ICEA Table 9A-5 below to the ampacity of a 3-conductor shielded cable of the same conductor size. apply the appropriate factors from the ICEA as shown in Table 9A-4.44 microhms per ft.65 0. This covers cables in free air installed in expanded metal troughs and trays.75 .069 1. in duct or buried same.88 .79 . and for cabkli 4/0 Or smaHer even less (see Page 9-8).86 .001 watts per conductor ft.84 .76 0.82 .76 . in air same.68 0.79 0.81 .01 more than the QS value in air. -22 -26 to-31 4 thru 6 80 70 7mru 24 251hru 42 43 and above Exceptions to the table above are provlded In 60 the above-referenced NEe Articles and should be adhered to when installations fall under NEe jurisdiction. the ampacity shall be as given in Tables 310-16. -22. Note No.8 of Article 310 states: Where the number of conductors in a raceway or cable exceeds three. but the maximum allowable load current of each conductor shall be reduced as shown in the following table: TABLE 9A-6 NEC Derating Factors Where Conductors in Raceway or Cable Exceed Three Number of Conductors Percent of Values in Tables 310-16. -18. -26 to -31.engineering design as related to cable applications Articles 310 and 318 of the 1987 edition of the NEC impose more restrictive regulations than those provided by the rCEA. -18. 9-29 . . Details of the various sizes of this conductor are listed in Table 4-26... and particularly as to sizes available in each category. For ease of reference some Chapter 7 descriptions of cable types are repeated in part. however. The cable construction consists of a bare neutral-messenger support member. engineering design. which serves as a neutral. are tabulated in Table 10-1. do not imply lack of use or demand. Conductor Ba".Generally all constructions are avail able in sizes No. (utility) for both secondary runs and service drops. Service-drop and secondary cable are commonly manufactured to comply with the appropriate ICEA Specification S-66-524 for crosslinked polyethylene (XLPE) insulated conductors rated at 900 C maximum. 10-7. no wind or sun. and 10-9. Other varieties of insulation including those mentioned in Chapter 8 may be available upon inquiry. and insulation is in previous chapters. Based on the referenced guide below Table 10-1. The following are typical sizes and insulation thicknesse1 for phase conductors: Conductor size AWG orkcmil 8 through 2 1 through 4/0 250 through 500 Thickness mils millimeters 45 1.. and temperature. communications..Section III Covered and Insulated Aluminum Wire and Cable Chapter 10 Product Classification and Technical Data This chapter deals with cable types available for power distribution. only a few of the available insulations are listed as a part of the description of each type of cable. Omissions. Service-Drop and Secondary Cable (Duplex. insulation. two or three insulated conductors. The product classifications in this chapter follow the plan of previous chapters by proceeding from the low voltage cables to those of high-voltage. To save space. ACSRlAW and Alu minum Alloy (6201) neutral-messengers. Insulated Phase . cabled with one.52 2. See Appendix 9A of this Handbook for discussion of ampacity ratings as listed by lCEA." is now available as described in ASTM B 786 in its uninsulated form. ACSR. The usual table of ampacity ratings is omitted in the descriptions of each style of conductor. In addition. First to be considered are the service cables. Triplex and Quadruplexj (Figure 10·1) This cable ordinarily is installed by the power supplier Fig. Cables of this type are suitable for applications where phase-to phase voltage does not exceed 600 volts. including related user applications.03 Available sizes . a modified type of stranding. and except for utility installations. with large sizes through 500 kcmil available upon special inquiry. 1 .. Neutral Messenger Service and Secondary Cables Class 10-1 Messenger-Supported. Neutral-Messengers-Constructions are available with full Or reduced sizes AAC. 10-1. Neutral-supported duplex secondary cable with solid Or stranded po wer conductor and bare. Considerable information regarding applications. Tables 310-16 to 310-31. the NEC is the governing docu ment. 19 wire combination "Unilay. and protection are not described. Installation practices and con nector selection are covered in Chapter II. in which typical ampacity ratings are listed for the applicable conductor size. and S-61402 for polyethylene (PE) insulated conductors rated at 75 0 C maximum.14 60 80 1. Instead. 10. stranded neutral. 6 through 410. ampacities at a fixed condition of 40'C ambient.. reference is made to a specified vertical column of Tables 10. Manufacturers' cata'logs should be consulted for de tailed specifications. not all available sizes are included in the description of each classification. Insulated conductors for instrumentation. 1. Ampacity listings for installations to 35 kV are found in NEC Article 310. Similarly. Application is governed by local building codes which generally reference the NEe. Ampacities for these constructions are listed in Table IO·\. Ampacities are the same as those for duplex· triplex Class 10·1. Three-conductor cables consist of two insulated conductors paralleled. ex· cept it is used more for secondary runs than for service drops. high density polyethylene (HDPE) and conventional polyethylene (PE) rated 75'C of the same thicknesses as listed for Class IO·\. The assembly is compacted. The conductors are bound to the messenger with an aluminum flat strap binder. R efe renee Flat Insulated Phase Binder 3 4 Crosslinked Polyethylene Duplex. SER cables are suitable for voltages not exceeding . 10·3) This cable is similar to Class 10·1 and the introductory comments also apply. RTS cable is generally used as secondary distribution cable and occasionally used for service drops. The usually available insulations are cross· linked polyethylene (XLPE) rated 90'C. SEU cable is manufactured to comply with the UL standard for service entrance cables (UL 854). 10-4) Cable construction includes two or three insulated conductors with a bare concentric neutral considered as a conductor. either full size or reduced size. Cable construction consists of two or three insulated phase conductors cabled about a straight neutral· messenger with direction of lay reversed at regular specified intervals throughout the length of the cable. protected and strengthened by a reinforcement tape. This cable is particularly useful in secondary distributions and where T·taps are required since "slack" can be obtained by untwisting the cable conductors. Preassembled parallel secondary cable. The introductory comments for Class 10·1 also apply to it. plus a cabled bare equipment-grounding conductor). It is employed as service entrance from the attachment point of the service drop cable down through the meter socket and then to the service panel. SE cables are recognized in Article 338 'of the NEC for use as feeder and branch circuit conductors with certain limitations. 10-2 Bare Neutral Messenger Fil!. and an extruded polyvinyl chloride (PVC) jacket applied overall. 10-5) SER cables meet all of the requirements of Class 10-4 above for SEU cables. The neutral messenger used with cables of Class 10·2 is the same as those specified for Class 10·1 cables. Triplex Quadruplex 1 2 Class 10·2 Preassembled Parallel Secondary Cable (Fig. Style SER cables differ from SEU in that the neutral conductor is insulated and cabled with the phase conductors. Triplex Quadruplex Table 10·1 Col. 10-2. according to the kind of insulation. The two or three insulated power conductors are laid parallel and are secured to a bare neutral messenger by means of flat aluminum·alloy binder ribbon applied helically about the assembly. Flat Binder Wire Bare Neutral Messenger Fig. about which is applied a bare concentric conductor. Avail able constructions are: three-conductor cable (two in sulated phase conductors cabled with an insulated neutral conductor). Preassembled reverse lay twist cable. Class 10-5 Type SE-Style SER Service Entrance Cable (Fig. This difference produces a round configuration for three-and four-conductor cables.covered and insulated aluminum wire and cable Type insulation and construction Polyethylene Duplex. 10·2) This cable serves a similar purpose as Class 10·1. Typical applications include range and dryer circuits. Class 10·3 Reverse Twist Secondary Cable (RTS) (Fig. 10·3. and four-conductor cable (the same as three conductor. Phase conductors in service entrance cable are usually NEC types XHHW and RHW. Class 10·4 Type SE-Style U Service Entrance Cable (Fig.. Three-conductor SE-Style "U" (SEU) cable is the more widely used construction. Adjustment of ampaeity values for cables closely adjacent in rigid cable supports.. hence the rounding to nearest I) amperes is allowable.-L~" 68 50 76 65 102 87 122 104 139 119 159 137 189 162 217 186 249 213 303 259 3Bl 326 4SB 417 578 493 150 190 220 250 280 315 365 400 480 580 135 175 200 225 255 290 330 360 435 530 175 200 225 250 285 325 350 415 105 135 130 16..x in Concentric in Buried 3/e in (.IC and Neutral RibbOn not triplex Neutral) abfe Conduit NM in Conduit Duct Air 110) 1111 112)11'31 I 114)iI15) (1. ~ . lit 6'"0 ° CoLNo. t:e... - . ~04l:" ' . . The listed ampacitiei for Clauss 104..a O• . Some ratings are in even figures.1(}.. (ml_ ~1I1= ~. hence the difference is ignored in the tables... 110 90 190 125 110 201 215 145 125 229 245 170 145 260 275 195 165 296 315 225 190 338 345 250 215 370 448 3BO 543 617 17... and 200 C ambient for cables in buried duct or direct earth burial. and -8... 262 292 364 466 45B 606 59B 730 716 840 944 1039 1103 1216 1321 1128 . i( AWG 90-. and may differ from ratings in NEe 310 tables as qualified by footnotes.~t. l'I •• 6 .i. T. Class 10-9 10-1(. but only to supply information as a supplement to the Clan Descriptions which should be consulted first. I 75 190 ~. 110-8 1.5 Insulatfll T%mp Conductors C I. should be rriade according to factors in Appendix 9A. Except for Classes 10-4. assuming 100% load factor and RHO-gO earth thermal resistivity...u 75 l2 15 Triplexod in Air in Air (8) 16) I (7) (9) 90 15 90 75 I 90 75 I 90 . 15160190 I 75 I 90 or 75 I 90 15 InDuct 90 151 75 Tripl$x 100% IF 3. I (11 (2) Q.- "ICI. 96 123 160 182 206 235 266 303 331 39S 481 50 65 90 100 115 135 150 170 550 _--'_ . use adjusted NEC values when NEe conditions must be met. x.--· Cla$$10·7 _ Class 1(). and -8 are based an 300e ambient.l/e ~ zlC 31C Pl. and others are roundad to nearest 6·ampere values. ~ ~ (31 (4) 15) III ·1...~ 12 10 8 6 4 2 1 I/O 2/0 3/0 4/0 250 350 15 25 70 95 130 90 125 60 BO 110 185 175 150 215 200 175 250 235 205 295 275 240 40 50 75 65 105 #100 #110 140 #125 165 '150 195 fl175 230 #200 64 B5 116 150 174 201 232 269 312 347 431 500 544 750 1000 1250 1500 1750 707 853 982 2000 55 73 97 128 149 172 199 230 26S 297 370 61 69 91 123 144 161 193 22.. -5.l!Hpa: kemU ..1-4-75 . o w 1 l a' ::> i ! ::> s'a t) .:es occur.. and after adjustment for difference of ambient tempera tures. the listed ampacitie$ afe based on 400C ambient for cable in air or 1n conduits in air. # Ampacities are from the NEe for throe-wire. -The listed ampacities generally are from ICEA tables.. This lack of uniformity Is e:xp!alnod by noting that ampacity ratings of suecea:sive batches may show a variation'·of ±2%.TABLE 10-1 Typical Ampacities for Various Sizes and Types of Stranded Conductors in Cables of the Class Descriptions Mentioned in the Text* (600 Volts or Less) NOiE: It is suggeued that this table not be used diractly.. . Some listings from industrY sources are based on 62% tACS elumlnum conductivity.111~(1. but most tabulated values are bas.. or where there is no maintained spacing..6 . slngte-phase residential services.7) Triplex ron. troughs. 10-2..1. -6.IH (25) 11261 (.. The effact on ampacity is only 8/10 of 1% in favor of the 62% aluminum. 44 59 78 106 123 143 165 192 224 251 312 392 512 612 43 58 76 102 122 139 159 189 217 249 303 381 488 578 37 50 65 87 104 119 137 162 186 213 259 326 417 493 50 66 86 45 60 131 150 172 196 78 103 119 136 156 178 226 205 II. 250 227 304 276 372 338 4B8 425 546 494 30 65 S5 115 135 155 lBO 205 240 265 330 410 530 625 53 70 92 108 125 144 166 192 214 265 330 424 500 .ed on 61% conductivity.. If dif1erenr..ipl. 10-3and"l 10-6 10. large fluorescent lighting installations. SER cable is primarily used in residential wiring to subfeed distribution panels in multi-unit dwellings. NEC describes the 6OO-'\'0It class completely for code applications. duct. and its Art. '-------- Insulated Neutral Conductor Fig. Cable is sized per NEC requirements. This classification includes insulated single or multiplexed cables for installation in air.Jacket----. 710 refers to requirements for "over 600 volts. cable ratings are based on the type of conductor insulation within the cable . Some manufacturers include the II)(J()-volt cables in a group specified for 6Ol-21)(J() volts.e Sa".for example. the (I)(J()-volt cables mostly are applied for certain circuits related to 10-4 industrial processes. The Aluminum Building Wire Installation Manual and Design Guide of The Aluminum Association lists sizes of the 600-volt class and NEC designations of insulation for various iemper atures and environments. motor loads. 10-4. cable tray. Where cables are used as branch circuit conductors. Cables of the 6OO-voh class sometimes are referred to as building wires because of the extensive use of single conductors for interior circuits. 10-5. It does not include multi-conductor cables (an assembly of several conductors under one jacket or sheath) nor cables designed especially for underground direct burial. The four-conductor cable provides an insulated neutral required by the NEC for feeders and branch circuits. hence they are not repeated in this handbook.-----.covered and insulated aluminum wire and cable Un insulated Insulated . Class 10-6 600-11)(J() Volt Power and Lighting Cable (not especially designed jor direct burial) (Fig. metallic or non-metallic conduit. Type SE-style U three-conductor service-entrance cable. 600 volts. Insulated Pha. though some cables of this class may be suitable for direct burial. Grounding Conductor . and sometimes where ungrounded neutrals are used. or suspended from messenger. XHHW for 900 C dry locations at the applicable ampacity caned for in NEC tables.e Conductors Fig. as well as an equipment-grounding conductor.-Pha." Under NEC conditions. Typical type SE-styte SER cable. 10-6) Cables of the 600-volt and lOOO-volt class are similar except for a slight difference of insulation thickness. Table 10-2 shows the usual range of sizes and kinds . etc.product classification and technical data of insulation generally used for the 600-volt class on the basis of 100 percent insulation level. 13 Each conductor in iripEexed assembly A in nonmetallic duct. as usually defined. and the entire assembly is enclosed in a Close-fitting tubular jacket or sheath which may contain fillers to round out its circular shape. with flexible neoprene or plastic jackets. have an outer protective covering of corrugated or interlocked design.. sembly in buried duct at 20°·C ambient is listed in columns of Table 10-1 as below: 9O'C 7S'C Cot 12 Col. Armored aluminum multi-conductor power cables. 6 Co!.. 10..conductor cable. C--Comparatively thin jacket. represents the formulation used for 1000 volts or less of the EPR ozone-resistant insulation listed in Table 8-2. neoprene. Many portable power cables are three. If the thickness is shown as a double number. with grounded neutral.---l. The EPM-EPDM insulation. the right-hand value applies to the jacket only. of two phase conductors and neutral B Insufion Jacket L c -'1_ _ _ _ _. 1: Single conductor. The Types NM and NMC also are three-conductor cables.. 10 Col. but because of availability only in small sizes for branch circuits they are separately considered as Class 10-8. 9 Col. available as Type MC (metal clad) with NEC conductors No. in air Each conductor of a triple. etc. has two or more phase conductors. D-Assembled aerial cable. buried. It is characteristic of three-conductor cables that the outer jacket must fit closely... It may also have an insulating jacket under the sheath. but because of its special application it is listed as Class 10-5. A multi-conductor cable.. 10-6. The insulation thickness for 1000 volts is slightly mOre than for 600 volts. Ampacity ratings' for these conductors in air at 40'C ambient (not buried or in underground duct) are listed in the following deSignated columns of Table 10. The Type SER service-entrance 6OO. hence pre-assembled cables in a comparatively large duct are not included. nylon.-( Flat Bare Binder o Phase Conductors Fig. Another style of Type Me aluminum corrugated cable has the tube formed around the assembly of insulated conductors. Typical 600-voll insulated power and light cables. P~46-462 10. A modification in branch-circuit and feeder sizes. B--Comparative!y thick jacket. it was included in Class 10-6 because essentially it is comprised of three closely spaced single conductor cables and is not designated as a multi. Sector stranded conductors are sometimes used in three-conductor cable as a means of reducing diameter. 7 Cel. 10-7J Although a triplexed cable has three cunductors. on the other hand. usually cabled. either cabled or layed up with reverse lay twist to facilitate side taps. (1962) as described in Chapter 9.7.x:ed assembly in air Each conductor of a triplexed assemhly in steel conduit in air 90'C Col. has an internal bonding strip of aluminum in intimate contact with the armor for its entire length. 5 . Type AC (armor clad). with the longitudinal seam closed . Fig. 8 Co!. A-No outer covering required. phase conductors.volt cable qualifies as a three-conductor cable.. Ampacity ratings for this class are from leRA Pub. listed in Table 10-2.conductor cables. Class 10-7 Three-Conductor Cable (600-1000 Volts) (Fig. 11 7S'C Ampacity rating of each conductor of a triplexed as. 12 AWG and larger. 6·2..16·1.38 mml.52-. "For No. No.03 110 1001-2000 95 2.14·.76·..4 and No. #For sizes No.38 60-30 1.65 65·65 1.52·. for No. Typical Insulation Thicknesses· of Power and Lighting Secondary Cables (600 volts) Q' iii' Q..02·.78-.14·.65 80-65 2...41 125 125 70-9 110·65 *100% insulation may also be used with ungrounded neutrals provided the fault-clearing devices clear the fault in less than one minute and completely de-energize the faulted section.79·1.8 and No.76·.65 2.14 45 1.52 •• •• •• .mil jacket is required for aerial instal1ation. If this condition cannot be met.38·.14 55-45 1.65 110·65 2.2.65 3. 12. 80 2.14 60 1.411 60·8 1.'"r Q a.) --------.13 mml.791110 2. for No.031 50·7 95 . for size. for No.51·.. value.23 2. are 45-30 mil~ (1. 0 Q TABLE 10-2 ~.14 8-2 45 1.65-1.03 213-600 65 1.79 1.41 501-1000 80 2.. o• la. § .52·.15 mm).7. Ilf thickness is shown as a double number..03·1.79·1.38 30·15 0.6.18 12-10 30 0.14·. 10. 16·1. Thickness of Insulation in Mils (1/1000 in.65 95-65 2. are 40·6 mils (1. value. Butyl SBR Rubber 750 C Wet Neoprene Jacket RHW·USE Mils OOOC Dry 750 C Wet Neoprene Jacket RHH-RHW·USE++ Mils mm mm -------+~ EPM·EPDM Ethylene Propylene Rubber 900C Dry 750C Wet Syn-Rubber Jacket RHH-RHW-USE++ Mils mm 45-15**· 1.52 60 1-4/0 55 1..38 45-15'" 1. but ICEA and industry ratings allow 900 C wet or dry for cables having these insulation thicknesses.40 80 2. Linked Polyethylene Conductor 1 900C Dry Size 75 0 C Wet 900C Dry USE-RHW 75 0 C Wet AWG-kcmil RHH++ Cia.76 60-30 1.76 45 1. B XHHW Mils mm Mils mm Stranded 750C Wet THW Mils mm Nylon Jacket THHN++ gooC Dry THWN 75 0 C Wet Mils mm 1.---------- I _ Polyvinyl Chloride Cro.65 95 2. values are 45-15 mils (1. ++NEC limits wet·location rating to 750 C.10 mml. values are 30·5 mils (.14 2. are 20-4 mils {.14 80·45 2. right·hand number indicates thickness of jacketl.27. 8a ii> .03·1. it may -be necessary to use insulation for 133 percent level (see manufacturer).76 # # 1.76 mml. values are 15·4 mils (. tOmml.18 3.14·.40·1. ~ 3 :. value.8 and No. 18180-45 2.65 2. ···A 3Q.03-1.20 195. This cable has a smooth tubular aluminum sheath surrounding three or more NEC con· ductors of branch-circuit size with ampacity ratings from 2(). If installed in underground duct at 200C ambient. three and four conductor cables are cabled into a round configuration. they are placed in trays or on other rigid suppons in power stations. Generally. and Ihe corrugations roll-formed to provide flexibility. though some types are suitable for embedded or under ground use. Colored PVC jackets are commonly used for this purpose. Class 10-'8 Types NM and NMC Nonmetallic Sheathed Cable (Fig. 15 for 75 0 C and Col. such as when pulling through a duct or after installation on supports. by welding. industrial plants and commercial installations. 12 for 900C may be used. Typical three-conductor impervious-corrugated or interlocked.amp to 90·amp. 15 of Table 10-1 and at 90°C per Col. formerly Type ALS. Three-conductor non-metallic-iacketed cable This cable is similar to Type MC armored or sheathed cable exrept that the protective covering is a round plastic jacket instead of a metallic sheath or armor. 2 for aluminum. using those for aluminum conduit for cables with alu minum armor. For three single-conductor cables in steel conduit. 16 for 90°C. The exterior surface of metal clad cables must be additionally protected by a suitable jacketing material when exposed to destructive corrosive conditions. par ticularly in wet locations. the factors of Table 9-6 may be applied. In any of these MC types. In wet locations. The equivalent of a separate bare or covered grounding conductor may be included as one or more conductors in the interstices of the cable arrangement. There are moderate NEC limitations as to where Type MC and similar cables may be installed. 14 for 900 C of Table 10-1 may be used. the ampacity is as shown in Col. The grounding conductors for Type MC cables are tabulated in Section 7. The range of available sizes of cables with welded tube corrugated armor differs from that of cable with inter locked armor.9 of ICEA Standard 5·66·524 and Section 7. If the cable is in air at 4QoC ambient. The protective sheath or armor is not designed for use as a neutral conductor and for interlocked metal strip design is not recognized as a grounding conductor. The three-insulated conductor round style is suitable for 3-wire circuits with one insulated conductor serving as neutral. For further information consult manufac turers' lists. The outer jacket is usually of neoprene or polyvinyl chloride. It is listed by UL for sizes No. armor. This design is used where it is desired to maintain a fixed configura tion of the conductors along with moderate protection against crushing and abrasion. 13 for 75 0 C and Col. a fourth insulated conductor can be included for three-phase.or four-conductor cable is used ex· tensively for interior wiring of branch circuits through the 75-amp ratings. The insulation of individual con· ductors used in this cable type may be any listed for Class 10·6 cables. Still another MC type is aluminum sheathed cable. but since it is closer to the conductors. Assemblies are enclosed in a moisture and abrasion resistant extruded PVC jacket. Y ·connected applications. the insulation should be selected for wet conditions.product classification and technical data Coding Tape Insulation Conductor Armor (Interlocking) Tape Grounding Conductors For calculating voltage drop in 6OO-volt three-conductor armored cable.. 12 and No. though the conductors usuallY do not require additional jackeling. three. The insulated conductors in the usual sizes of No. 17 for 75°C and Col. Its use eliminates cost of conduit installa tion and wire pulling. its inductive effect is about the same.10 of 5-19-81. The ampacity of the three-conductor unarmored or aluminum-armored cables in air at 75°C with 40°C ambi ent is per Col. 14. NM and NMC cable is satisfactory for use in circuits nO! exceeding 600 volts and where conductor temperatures 10·7 . or Corrugated Fillers Fig. 12 through No. 10-7. These plastic-jacketed three-conductor cables may be installed in the same manner as single power cables (Class 10-6). 10·8) This two·. the ampacity rating of Col. where provision for growth is not necessary. The armor is thinner Ihan the wall of standard conduit. Col. 10 are arranged in parallel for two·conductor cables. and those for steel conduit for cables with steel. The insulation of the individual conductors may be any listed for Class 10-6 cables. These cables are particularly useful in control circuit wiring. corrugated armored cable. NEC cables designated Type UF (underground feeder) are included to 4/0. Cable construclions are available wilh or without a bare grounding conductor. The Type I'M cable is approved for installation in both exposed and concealed work in normally dry locations. Fig. Still another form is the ribbon 3 (A) Two-Conductor Concentric Neutral Type (e) (8) Three-Conductor Triplex Type Concentric Neutral Type Plain or Corugaled Pla. to size or smaller are solid. A less frequently used form has a copper-wire neutral spiraled closely around one or two paralleled insulated conductors. Conductors of No. and annealed for flexibility. Bare aluminum neutrals are usually not permitted for URD cables because of the possibility of corrosion in wet earth. Fig. Installation in moist or corrosive locations is approved and under certain conditions it may be used where Type NM is prohibited.tic Duct (D) Ribbon Type IE) Trlplexed Plasllc Conduit Typo Note: A concentric-neutral cable may be used instead of the triplexed as shown for installation in plastic conduit (El. Ampacities. with Ground. Neither type is approved for service entrance use.covered and insulated aluminum wire and cable Type NM (2·Cdr. Oval Section) (Can be obtatned without gfOuodlng conductor. or plaster. (Fig. 10-9) Although these cables are usually designated as for URD. Some sizes are available in both solid and concentric stranded aluminum conductors. Type NMC cable resembles type NM but has an integral jacket which is fungus. nor for locations as limited in NEC Section 336-3. Certain other conductors in Class 10-6 are also suitable for direct burial. 10-9: Typical600-volt cables lor direct burial. concrete. do not exceed 600 C. because an advantage of this type of cable is that it readily may be bent into place. 18. Type NM (3 Conductor. are in Col. nor may it be run in masonry. Type NM branch-wiring cables. they are of course suitable for any other direct burial use within their ratings. Round Section) (Also available with bare grounding conducfor) Fig. A popular cable is a triplexed assembly of which one conductor is an insulated neutral.or Three-Conductor Cables for Underground Residential Distribution (URD) 600 Volts (Fig. Class 10-9 Secondary-Distribution Single. 1O-9C. the solid type is an intermediate temper. 1O-9A & 9B) Copper is used for the earth contact because of its resistance to corrosion under buried conditions. 10·8 . but not for exposure to corrosive conditions. such as USE or the combination Type USE-RHW -RHH available in several insulations. Table 10-1.and corrosion-resistant. based on 300C ambient. 10-8. or (5) (4) (3) Cross· Linked Polyethylene Triplexed 75°C mm Mils 60 80 95 1. after installation. *The thicknesses shown include 30 mils for jacket.41 - - Sizes are concentric stranded -conductors. This ampacities of triplexed buried cables are listed in Cols. Two or three conductor cables. may be sized to allow for some degree of enlargement on the system as installed. that is. 12 to 4/0 AWG. 10-10) Portable aluminum cables. 8 to 1000 kcmi!.cting web between the conductors. respectively. 22.41 Plastic Conduit Type 75°C Mils mm Mils mm 95 125 2. Flat constructions are also available with conductors arranged parallel to one another and with a common overall jacket. cable in which two parallel insulated phase conductors have an insulated neutral between them. Fig. Ampacity ratings are usually approximately as follows for 75 0 C 10·9 . special applications where flexibility is a requirement due to installation handling or vibration is a consideration. Care should be taken by the purchaser to assure that the product offered is UL-Iabeled for these applications where required. The ribbon type has ampacities according to in dustry sOurces and tests as listed in Col.91 2. are constructed to yield a high degree of flexibility. 24.ous operation.03 2.product classificatIon and technical data TABLE 10-3 Typical Insulation Thicknesses of Secondary Cables (600V) for Direct Burial or Underground in Duct Thickness of Insulation in Mils (1/1000 in_). 10-9D. 25 and 26. Use of this product provides for conductor replacement The ampacity ratings of the cables pre-assembled in plastic ducts for the 90 0 C ratings are in Col. Portable aluminum cables possess a lighter weight than other constructions. or Triplexed 90°C Mils mm Mils mm 1. Duct sizes are compatible with existing accessories and. Available constructions include cable in a duct. If the cables are for three-phase (3 or 4 conductors). Millimeters (2) (1 ) Conductor Size A WG-kcmil 4-2 1-4/0 225-500 Parallel Ribbon Type' 75°C Concentric Neutral. Single-conductor portable cables are available for should be reduced. 19 and 20 of Table 10-1 list ampacities of 600 volt buried cables of the concentric-neutral type (having spiraled bare copper neutrals) at 20 0 C ambient for in sulation suitable for 900 C and 75 0 C. Special inquiry also is required for availability of sizes for Column 2 for sizes above 300 kernil. for solid-conductor sizes (except for Column 5) refer to manufacturer. Table 10-3 shows the usual range of sizes and kinds of insulation generally used for the 6oo-volt cables of the types described and Table 10-1. In all cases of direct burial Or duct installation an earth thermal resistance of RHO-90 is assumed with a load factor of 100 percent. The Single-conductor portable cables usually are available from No.41 60 80 95 (6) Polyvinyl Chloride or Low-Density Polyethylene Parallel Ribbon Type' 90°C Concentric Neutral. either single or multiple conductoc.16 2.52 2. The threeCconductor URD cables for 600 volts in the arrangements shown in Fig.52 2. and to local codes requiring that underground secondary service cables leading directly to the home be UL-listed. the cables will withstand construction consists of two or more conductors pre these ampacity ratings for continu. These conductors are phase-identified for circuit applications. The web is easily torn away during installatio~. The insulated conductors in any of the above-described cable assemblies can be any of the conductors of Class 10-6 listed by NEC as suitable for direct burial. which facilitates their use.03 2. Cols. The insulation is extruded over the three conductors simultaneous1y so there is a thin conne. Cols. 23 and for the 75 0 C ratings in Col. Consult suppliers. with or without equipment grounding conductors.41 75 85 95 1. or the web may be only a part of a jacket.18 60 80 95 1.03 2.41 3. are ·cabled together with the necessary fillers to construct a round cable and employ an overall jacket of thermoplastic or synthetic rubber. 10-9 are for three-wire single-phase circuits. through supplier inquiry. 21 for 90 0 C and for 75 0 C as in Col. and multiple conductor portable cables from No.52 2. the ampacities shown in Table 10-1 Class 10-10 Portable Aluminum Cables (600 Volts or less) (Fig. assembled at the factory in a plastic duct (Figure 10-9E). 19 to 26 sum marizes ampacities that conform to ICEA requirements. Flexible cables usually employ an intermediate tempered aluminum conductor which is insulated with a synthetic rubber or thermoplastic material. insulation. 25-. 10-11) Aluminum Con. Where the application environment is severe. and 35·kV all with grounded neutral. 15-. . municipal.trol Cables (for 600 Volts or less) Because of the wide variety of multi·conductor cables used for control and signal circuits and the generally small size of the individual conductors. com prising aluminum conductors. constructions are available with reinforced overall jackets or armoring. and overall jacketing. operating temperatures and 400C ambient temperatures: Single-conductor cables Col. The individual conductors (either stranded or solid) are insulated with compounds that best meet conditions. 27 in Table 10·1 Often a long portable cable is partly held on a gather ing reel. or jor aerial suspension jrom messenger. suitable jor installation in ducts.be consulted. no detailed descriptive listing of them is attempted for this book. Typical aluminum multi·conductor control and signal cable. The 3-kV and 8-kV ratings sometimes are listed. even though the actual increase from the lower circuit levels may be long delayed. A WG 9 to 14. 3 in Table 10·1 Two-conductor parallel or round type Three-condllctor. W-ll.covered and insulated aluminum wire and cable A {AI Two~conductor D C S (S) Two·sonductor With Flat EquipmentGround Conductor Fig. available with 2 to 18 conductors. and the whole. but are less used because the trend is toward the next higher voltage in anticipation of load growth. The automatic control of machine· tool operations is a recent application for which control cables of oil-resistant type are used. direct burial. and railroad installations for control and· signal purposes. 10·10 Fig. web-tape cushion. These control cables have wide application in utilities. Those with rubber or thermoplastic insula· tions mostly are for 5·. The above ampacity values are reduced for such cases by multiplying by the foUowing correction factors: One layer on roll Two layers on roll Three layers on roll Four layers on roll 0. 10-10. round Col.65 0. assembly is contained within a round thick overall jacket of neoprene or thermoplastic material. (C) Two~conductor (D) With Stranded Equipment~ Ground Conductor Three~c(JOductor With Stranded Equipment· Ground Conductor Note: The web-tape cushion prevents longitudinal sep aration of insulation and jacket durin.85 0.35 Class JO·ll (Fig. 4 in Table 10·1 Col.45 0. industrial. Cables For Primary Distribution Voltages The types and voltage range of primary distribution cables with aluminum conductors were briefly described in Chapter 7. Manufacturers' lists should .g bending oj the cable. Typical cross-sections oj portable cables. Thus. Also they may be used when additional insulation strength over the 100 percent level category is desirable. While these cables are applicable to the great majority of cable installations which are on grounded systems. Jacket Thickness The insulation of unshielded cables may be of such quality that it will withstand all environmental conditions likely to be encountered. since excessively high voltages may be encountered in the case of ground faults. but as protection for the insulation shield ing. based on diameter. that there are other conditions than lack of neutral ground that may make a thicker insulation desirable. Jacket thicknesses have subsfantially become standardized as shown in Tables 10-5 and 10-6. no jacket has to be added. The individual conductors of a multi-conductor cable that has a jacket surrounding all conductors may have thinner jackets than those specified in Table 10-6. Shielded cables. and usually it is a different compound than that of the insulation. For a direct-current system up to and including 2000 volts consider it the same as a single-phase alternating-current system of the same rms voltage. require a jacket. Cables it! this category may be applied in situations where the clearing time requirements of the 100 percent levei category cannot be met. the latter requiring thicker insulation. If so. it shall be the same as for the 133 percent insulation level The AElC reference to the preceding statement re garding insulation levels also includes the following: In common with other electrical equipment.4 kV. and abrasion in handling. Consideration of this requirement is in the province of the system electrical engineer. and yet there is adequate assurance that the faulted section will be de-energized in a time not exceeding one hour. however.Insulation Thickness For three-phase systems with grounded or ungrounded neutral the thickness values are those given in the respec tive columns of Table 10-4. but often a slight increase in insulation thickness is used to provide for expected surface wear and to equal other advantages obtained by a jacket. not necessarily for improving surface quality. the use of cables is not recommended on systems where the ratio of zero to positive sequence reactance of the system at the point of cable application lies between -I and -40. oil. The jacket material selected is the most suitable to meet conditions.product classification and technical data Customarily. Table 310-13). but the thick ness also depends on diameter of the cable and voltage. It is recognized. consult the 173 percent insulation level referenced above.' 133 Percent Level-This insulation level corresponds to that formerly designated for ungrounded systems. unless protected by armor. • Where additional insulation thickness is desired. on tbe other hand.and two-phase grounded systems. they may be used also on other systems for which the applica tion of cables is acceptable provided ·the above clearing requirements are met in completely de-energizing the faulted section.above is 30 mils. Con sult the manufacturer far insulation thicknesses. The relative suitability of jackets of various materials can be determined from Table 8-4. Column 4 lists thickness of the overall jacket. such as moisture. For single. The minimum thickness that qualifies a coating as a jacket on cables 2 kV and. It is necessary to distinguish between an overall jacket 10·11 . The selection of the cable insulation level to be used in a particular installation shall be made on the basis of the applicable phase-to-phase voltage and the general system category as outlined below: 100 Percent Level-Cables in this category may be ap plied where the system is provided with relay protec tion such that ground faults will be cleared as rapidly as possible. Their use is recommended also for resonant grotindedsystems. I nstead the insulation thicknesses are assigned based on insulation level (AEIC #5 and 1987 NEC. an insulated conductor of a single-phase branch circuit including a phase wire and a ground wire that is con nected to the wye ground of a 25-kV three-phase wye grounded circuit is still rated 25 kV although the actual rms kV of the single-phase circuit is only 251\13 or 14. Jacket thicknesses generally conform to those listed in Table 10-5. Several of the modem insulations meet this requirement. but in any case within one minute. For three-phase delta systems where one leg may be grounded for periods of over one hour. or would be a part if the three-phase circuit were complete. Cable descriptions in this book and in the literature dis tinguish between the insulation thicknesses required for high-voltage cables in circuits with grounded neutral and those with ungrounded neutral. Tabular Voltages for Determining . and conform to column 3 of Table 10-5.73 and select thickness for that voltage in the grounded neutral column. 173 Percent Level--Cables in this category should be applied on systems where the time required to de energize a grounded section is indefinite. based on AWG-kcmil size. This notation applies principally to the single insu lated primary conductor of the two-conductor cable that supplies the single-phase transformer that feeds the sec ondary three-wire circuits. multiply the voltage to ground by 1. and in Table 10-6 for single conductor cables. sunlight. To meet this condition the concept of grounded and ungrounded neutral is in the process of being eliminated as a sole criterion. primary-distribution insulated cables are voltage-rated on the basis on the phase-to-phase voltage of a three-phase circuit of which they are a part.. covered and insulated aluminum wire and coble and a band of belt insulation, as found in some kinds of cable, such as for series-lighting circuits. Primary Unshielded Cables 3 kV and 5 kV The 5 k V rating is the most used of this type, Fig. 10-12. If the insulation does not have a satisfactory surface for withstanding eilvironmental conditions a jackel is added. The usual cable construction without jacket comprises a Class-B stranded conductor (or it may be solid round in small sizes). a resistive conductor-shield and insulation of the thickness listed in Table 10-4. The' insulation must be ozone and corona discharge-resistant, suitable for wet or dry locations, flame retardant, and suitable for sunlight exposure, although the latter two qualities may be obtained by jacketing, if nOt a characteristic of the insulation. The jacket, if used, must also be corona discharge resistant. Primary Cables with Insulation Shielding (to 35 k V) The conditions that require shielding at 5 kV are stated in ICEA' and pertain principally to single con ductors at 133 percent insulation level or where cables are installed underground directly buried, in ducts or in wet locations. The shields are also required if the insulation or jacket is not one that protects against OzOne or its effects. Insulation thicknesses are listed in Table 10-4. Generally, except for the shielding, the same construction applies as for nonshielded cables. Fig. t 0-13 is typical. Triplexed preas sembled cable, or three-conductor cable, either jacketed or in metallic armor of constructions pre viously described is often used in the 5-kV-and-above ratings, Figs. 10-14 to -16. For ampacities see Table 10-7. Primary Interlocked-Armor Cables (Fig. /0-16) The description of interlocked corrugated armor used on cables for 600 volts (page 10-5) applies to cables for the primary voltages except for strand and insulation shielding requirements. Howe,,'er. the impenrious seamless corrugated armor is not as yet available in as many voltage ratings or sizes as the interlocked armor. Three conductor armored cables are the most used. Single conductor cables are available for special applications with non-magnetic aluminum armor. The cables are available both with and without an ex truded outer covering under the armor. Either aluminum or steel armor is available. Voltage drop at circuit power factors less than 100 percent is increased if steel armor is used, but is negligibly affected by aluminum armor. The ampacity rating of a three-conductor cable with aluminum corrugated armor is substantially the same and may be somewhat more than that of the insulated three-conductor cable in air; the increase in area because of the corrugations and the closeness of the conductors to the armor both serve to increase the rate of heat transfer. For ampacities, see Table 10-7. Insulalion Sirand Jacket Separator Tape Metallic Wire Shietd Fig. /0-12. Typical unshielded aluminum insulated pri mary cable 5 k V with jacket. 'ICEA S-61-402 Table 4. 10-12 Fig. 10-13. Typical 5 kV to 35 kV shielded insulated primary cable. Note: The metallic shielding may be tape as shown, or helically applied closely spaced small wires. produ,ct classification and technical data TABLE 10-4 Insulation Thickness Inot including jackets) for High·Voltage Conductors in Three·Phase Systems with 100% and 133% Insulation Levels, (or Grounded Neutral and Ungrounded Neutral, respectively). Thickness in Mils (=1/1000 in.) Note: The values in this table are obtained from ICEA or industry designations of thickness for the insulations named. However, because of variations of dates at which the values were issued, and because of lack of uniformity of the size~steps, slight variations occur. Also some cable manufacturers issue specifications that in some respects show more favorable values. The insulations are those used for ozone-resistant conditions. In the 5OOO-volt class certain other insulations listed in Table 8-2 and 8~3 may be used but not necessarily at the listed thickness. Voltage and Size AWG and kcmit L,. . (21 Grounded Neutral mils mm I EPR XLPE or PE(1) Un· Grounded Neutral mm mils Grounded Neutral mils Grounded Neutral Un· Grounded Neutral mils mm mm Butyl mm mils Silicone (SAl Un· ! Neutral mm mils : UNSHIELDED 2OO1·5000V(31 8·4/0 225·500 525-1000 SHIELDED 2oo1-5000v 8-410 225·500 525·1000 5OO1·8000V 6·500 525-1000 8001·150ooV 2·1000 1·1000 15001·25000V 1·1000 25OO1-28000V 1·1000 28001·350ooV 110-1000 110 120 130 2,79 3.05 3.30 110 120 130 2.79 3.05 3.30 "90 *So *90 2.29 2.29 2.29 "90 *90 "90 90 90 90 2.29 2.29 2,29 90 90 90 2.29 2.29 2.29 90 90 90 2.29 2.29 2.29 90 90 90 XLPE 90 2,29 "155 3,94 **155 3.94 2.29 "170 4,32 "'70 4.32 2.29 **170 4.32 **170 4.32 155 3,94 170 4,32 170 4.32 2.29 2.29 2.29 : 115 2,92 115 2.92 175 140 140 3.56 3.56 4.45 ! 115 115 2.92 • 140 2.92 • 140 175 4.45 215 5.46 345 8.76 260 6.60 345 8.76 45511.56 5001 12 .70 7.11 420 7.11 280 7.11 420 7,11 345 8.761 420 7.11 345 8.76 420 7.11 260 345 345 NOTE: The difference of thickness between unshielded and shielded 5 kV cables using XLPE or PE insulations reflects the fact that the unshielded cable has a potential distribution not as even as that of. the shielded cable. See page 10-15 for additional notes. ! 5.46 280 260 155 3.94 170 4,32 170 4.32 250 4.83 250 4.83 I 6.60 175 3.94 4,32 4.32 295 7.49 260 175 190 4.83 . 190 4,83 3.56 3.56 215 HPE 90 ! 155 170 170 I , 2·Conductor Concentrid41 Helical Bare Grounded Neutral 5kV #4·350 15 kV #4·350 25kV #2-350 35 kV 1/0-350 Grounded or Ungrounded Neutral mm mils Grounded ! 420 10.67 * Required by specification to have an outer jacket; maxi mum 3.phase voltage for 133% insulation level 3000V JACKET AWG or kcmil 8·6 4-210 3/0-1000 THICKNESS Mils mm 30 45 0,76 1.14 1.65 65 **Required by specification to have an outer jacket JACKET AWG or kcmil 8-1 1/0-4/0 225-750 1000 THICKNESS Mils 45 65 65 95 mm 1,14 1.65 1.65 2.41 10·13 covered and insulated aluminum wire and cable TABLE 1()'5 Jacket Thicknesses for Single- and Multiple-Conductor Power cables According to Diameter Under Jacket For all uses; Conduit, Tray. Trough, Underground Duct, Aerial, and Oirect Burialt but does not include Communication' or Portable Cables Jacket Thickness Multiple-cQtlductor Cables" (41 (31 Sing1c-conductor Cable ill (21 Individual Calculated Diameter of Cable Undef Jacket inche$ mm 0.250 or I... 0.251·0.425 0.426-0.700 0.701·1.500 1.501·2.500 2.501 and larger + 6.35 or less 6.38-10.80 10.82·17.78 17.71·38.10 38.13-63.50 63.53 ond lorger Shielded"· Noll$hielded mm mils mils mm 15 30 45 65 95 125 45 45 60 60 110 140 1.14 1.52 2.03 2.79 3.56 0.38 0.76 1.14 1.65 2.41 3.18 1.14 Conduct.... t mils mm 15 25 30 60 60 0.38 0.64 0.76 1.27 2.03 Overall mils mm 45 45 60 60 110 140 1.14 1.14 1.52 2.03 2.79 3.56 Under common jacket. t These thicknesses apply to jackets only and do not apply to colored coatings used for the purpose of circuit identification on the individual conductors of multiple-conduClor cables. +Single-conductor cables in sizes 9 AWG and smaller shall not be used for direct earth burial. _. In calculating the diameter under the jacket of single-conductor shielded conductors that are part of a multi-conductor cable, add 45 mils to the insulation thickness to allow for thickness of the inSUlation shield. Also add the thlckness of the separator and strand tapes. Eqs. 9-3, 9-4, and 9-5 provide a means for calculation of diameter, provided Di is the inside diameter of the jacket instead of the outer sheath. Two-conductor cables for direct burial having helical bare copper wire ground conductors have an outer protective covering of conducting material that also serves as an insulation shield. The layer is not less than 30 mils thick. NOTE-For flat twin cable, use the calculated major core diameter under the jacket to determine the jacket thickness from Column 4. Source: ICEA 5-61-402 TABLE 1()'6 Jacket Thicknesses for Single-Conductor Power Cables, According to AWG·kcmil Sizes For all uses; Conduit. Trays. Troughs. Underground Duct. Aerial and Direct Surial. not including Communication or Portable Cables. It is assumed that the jacket material is compatible with the insulation for the designated kV ratings. These thicknesses also apply to single-conductor cables if they are triplexed, but they do not necessarily apply to the cables that are a part of a three-conductor cable. for which the thickness may be according to column (3) of Table l()..S Percent Insulation Level Thickness of Jacket, Mils (= 111 000 In.), (mm) 60 (152) 80 (2.03) 110 (2.79) 3/0 • 1000 2/0 • 1000 #1 • 750 #2 • 750 #1 · 800 1000 1000 750 • 1000 133% #1 · 500 #1 ·350 600 • 1000 400 • 1000 25001 • 28000 100% #1 • 500 800 . 1000 28001 • 35000 100% I/O . 350 400 • 1000 Volts 30 (0.761 45 (1.14) #8· #6 #4 • 210 65 (1.65) UNSHIELDED 2001 . 5000 100 & 133% 310 • 1000 SHIELDED 2001 . 5000 5001 . 8000 8001 • 15000 15001 • 25000 Source.. ICEA S-61-402 10-14 100 & 133% 100% 133% 100% 133% #8 #6 • 2/0 #6 - I/O #6 • 2 100% I produd c:lassification and technical data TABLE 10-4 NOTES (2) The characteristics for the kinds of insulation shown are listed in Tables 8-2, 8-3, and 84. for which also see rated temperatures. If insulation is rated acoording to "percent insulation level," use column "grounded neutral" for 100% level. and column for (3) "ungrounded neutral" for 133% level. Solid dielearlc insulated conductors operated above 2000 volts generally f"equlre shielding under the NEe. Conditions under which (1) shielding is not required in the 2000-8(100 volts range are detailed in NEe Section (41 310~6. The cables listed in the main body of the table are generally available in the sizes shown as single conductors or cabled for aerial messenger support, or in tray or duct~ and with some insulations are suitable for direct burial. The two-conductor concentric neutral cables are mostly used for direct burial, but they also may be used in duct or be aerial-supported. The insulation thickness tOt coaxial cables (in which the neutral is tubular) are Similar, 80 ... Messenger Shlald Fig. 10-14. Typical pre-assembled triplexed 5-k V to 25· kV shielded primary cable bound to composite aluminum steel (ACSR or A CSR lAW) or aluminum-alloy messenger with aluminum tape. A fourth insulated neutral may be in~luded if required. The construction of each conductor is similar to that de picted in Fig. 10-13. Also available with one, or two phase conductors. For certain sizes reverse-lay may be obtained (see Fig. 10-3). Also for parallel lay (not Iriplexed) field-spinning equipment is available' so that the assembly with lashing wire may be performed at the site. Similar pre-assembled triplexed (or parallel) cables are available without insulation shielding to 5 k V. Primary Cables for Underground Residential Distribution-URD Directly buried URD/U D style cables are increasingly being used as "main-line" three·phase distribution feeders. However. by far the most used primary cables for URD are those thaI supply single· phase primary voltage to the single·phase 1ransformers supplying 120·240 V three-wire circuits to the residences or other use.poims in the area. These single·phase primary cables are of Fig. 10·15. Typical three-conductor 5-kV to 35-kV shielded primary cable in jacket, The construction of each conductor is similar to tfuJt de picted in Fig. }0·}3. Triangular fillers in the interstices aid in forming a cylindrical exterior that still will withstand bending from reel. Bare grounding conductors may be used in the interstices if required. the two-conductor type. One conductor is an insulated phase wire. The other is either a copper-wire concentric neutral conductor of equal conductivity to that of the aluminum insulated conductor, Fig. 10-17, or a concentric. flat strap neutral, Fig. 10-18, particularly adapted to con ditions where substantially full metallic coverage is desired. These copper neutrals are directly in contact with the ground when buried. The phase conductors of these cables have semi· conducting strand shielding and semi'conducting com pound undernea1h the concentric wires or "raps to serve as an insulation shield. The insulation thickness around the phase conductor is generally the same as listed in Table 10-4. For am· pacities see Tables 1O·9A and 10·9B. 10·15 covered and insulated aluminum wire and cable High Voltage Primary Cables Aluminum cables are commonly 115 kV levels, Advances in materials expertise have resulted in available higher voltage levels, While previous available through and manufacturing cables in this and cable constructions Bare Coated Copper Neutral Insulation Strand Shield employed paper insulation, with some gas-filled designs. today's market offers some cables of this type with solid dielectric insulations. Polyethylene and crosslinked poly. ethylene and similar materials are being employed in cable designs. Information concerning availability and design should be directed to individual cable manu facturers. As typical of such construction, a IIS·kV, 500·kcmil aluminum cable for direct burial, with strand and insulation shielding has 0.740 in. XLPE insulation thick ness (0.525-in. for 69 kV), with a 0.140·in. thick PVC jacket, and 2.90·in, overall diameter (2.37 in. for 69-kV). Ampacity of High Voltage Aluminum Cables The ampacity values listed in Table 10-7A, -B, and -C for the designated cable types and installation conditions mostly are those listed in ICEP. Pub. 46-426 Vol. II for aluminum, as explained in Chapter 9, applying to rubber or thermoplastic-insulated cables. The insulation is as sumed to have a power factor of 0.035, dielectric constant of 4.5, and thicknesses for the various voltages that were listed in ICEA Standards in 1962 when the ampacity values were published. Cables directly buried or in under- Fig. ]()"17. Typical 5 to 35 kV two-conductor concentric wire neutral primary cable for direct burial, duct or aerial application. Bare Coated Copper Neutral Insulation Strand Shield Conductor Insulation Shield Conductor c~;"~~~~orl'nSlu.ai~~;nd Tape Shield (OPliOr 1 (Inlerlocklng) Armor 1 1 Fillers Tape Fig. 1().16. Three-conductor shielded cable 5 kV to 15 k V with interlocked or impervious corrugated steel or aluminum armor. 10·16 Fig. ]()'18. Typical 15·35 kV two-conductor concentric flnt-strap neutral primary cable for direct burial or duct. ground ducts are assumed to be in circuits of 100% load factor and RHO-90 earth resistivity. For 75% load factor, direct burial, increase ampacity by 6%, or for duct 3%; and for 50% ],f, by 14% and 6% respectively. Table 10 7 is based on 40'C ambient for cables in air, and 20'C ambient if underground, Adjustment factors for other ambients are in Table 10-8. Separate tables 10-9A and JO-9B list the arnpacities of concentric-neutral primary cables for direct burial in duct, at 200 C ambient, and also for installation of the cables in air, or in duct in air, at 400C ambient, as necessary for leads into air from an underground installation. Table JO·9A also includes ampacities for 35 kV cable when buried directly or in duct. Inasmuch as ICEA and industry standards now allow some reduction of thickness of certain kinds of insulations as compared with the values that prevailed in 1962, and also because most insulations have a luwer p.f. than 0.035, product classification and technical data TABLE 10-7A Typical Ampacities of 5 kV Cables with Aluminum Conductors of Various Types and for Various Installation Conditions 5 kV in Duct 20"'C 5 kV in Air 4o"C Grounded or Conductor Ie in Ai, Size AWG kernil Neutral ~~'of ;u ] 7~ • 19o"C !7SoC 55 6 73 4 ........ 97 129 2 64 : 44 59 78 : 85 113 ~, , 210 3in 410 - 2681 =i ~ 3101 466 606 73{J 840 -1~ 9 'ii) 39 9 192 224 224 262 31 ""2 458 166 19: 214 265 330 """, 716 i 499 '.3 ", 43 544 70 8531 : 364 : (5)' -: 46 61 54 63 81 71 :..... 8: 108 95 12. 113 131 145 131 150, 168 174 153 194 .224 256 1 '50 I 21. 309 I 21 320 385 I 335 398 4"5 ' 43' .....51. 584 .515 605 62 45: 1 60 78 56 96 125 ; 1 269 321 401 .05 59 : 103 131 15e 17: --¥50~ I 73 79 85" I 42 296 22 360. 276 304 4421338 . _~ 556 425 546 65' 49. I leof 3 (8)' 84 9B ____ 108' 72 80 127 14U : 163, 180 94 -'~ 109 120 184 20, . 231 1:151 138 143 156 : -.. ,26' 272 '299 164 -- 180 ,.7 206 307 20 228 335 25: 278 444 403 490 540 308. 340 386, 426 605 667 447 : 495 i 706 , 778 ' 781 g;: 90. 930 990 1094 8801 ~.~~ : loo'C 65 72 94 92 lU8 119 139 158 180 . j1E~ ; :;~fi 349 424 525: 579 5"" b72 , " 9401 notes l"t'Iay be found under Table: 10-7C j 19) n 46 61 55 119, 136 205,_ 156 , 143 163 187 Triplexed lC I .: 75" 90°C 75°C 'WC 7S;'C !90'C i 7S'C 9O'C 73 m' (6) :~ i~-~:~;:l·~ 42, 9"" 1103 10391 1216 1128 1321 2000 1 53, 12: 144 167 < 26' 3' (4)" Three Condo lof3C : Triplexed , lC of 3 lC - 51 69 N.u".' j WC 175"C 190'C75'C loo'c :'SoC 14" 110 (3)' (Z) 100 LF : : ! (1)' RHO-go : Th~ ~nd. ! Interlocked : lof3C : Armor 1 of 3C 5 kV Directly Buried 20"'C Ambienl Onshieldedt RHO-SO '00 IF 1No.".1 Source: ICEA P-46-425 TABLE 10-7B Typical Ampacities of 15 kV Cables with Aluminum Conductors of Various Types and for Various Installation Conditions I 15 kV in Duct 20°C Ambrent-Shielded 15 leV in Air 40°C Ambient RH~90 Shiekted : 15 leV Directly Buried 20°C ' Ambjent·Shidded RHO·90 100 LF 10 LF Grounded Neutta' Grounded Neutral Grounded Neutral I Ilnwrlocked ! , Size AWG kcmil 1e in Air TripMxed leof3 t 1)" (2) go'c 75°C 7SoC Armor TareeCond. Thne Condo 1 of 3C 1 of 3C i (51· (4)44 (31 a 75°C: 90°C i 75°C 90 C 75°C 9(l°C Triplexed 1C of3 Ie ThreeCond, 1 of 3C lC i1I 18)· 161 Triplexed 1C of 3 90 °C:, 7SoC ;~¢C 75°C: 90°C: 7SoC! SOoC 139 ' 110 159 125 142 181 ,., ;rob 23. 184 106 1121 :38 120 ,157 : 137 191 oooe "/Soc i 1/1 10 10 2'>0 350 =ii 1500 1750 2000 130 152 170 199, 229 ' 2Q2 "3 232 268 175 202 """. ',u 293 343 115 128 • 95 109 125 ' 143 I , •• 121 178 205 164 192 146 237 : 189 : 221 168 I 135 302 240 363~=i ~. 312 294 344 587 591 459 639, 687 258 . '=i 216 158 126 144 164 183 181 119 208 213 1 I. 1203 • 1"" 117 117 133 101 149 .70 154 187 • 213 :'<44 1 12 2"" 2/. 196 : 250 ''''' LLL . : 26, . 2.1 332 323 29' 35, 395 541 .~~ i~ 412 221 : :l44 • " , 266 322 294 378 '"1 44U "14 529j 810 "'"' 905 I 1060 994 - 1165 lUlb : "'"' , : , Applicable nOtes may be found under Table lO-7C. : 776 I 827 I •• ' "20 859 917 : 945 887 """ 417 ."" "'967 U_ 133 ; 147 152 : 167 'I. '"' .211 ''''' 220 24. LOU u. 1 CJtJI 335 369 405 : 447 4"" • ""2 I 1047 Source: lCEA P-46-426 10·17 covered and insulated aluminum wire and cable the ampacity listings of Table 10-7 are conservative for some applications, and cable manufacturers may offer moderately larger ampacities. However, as previously stated. the 0.035 p.f. value is an ICEA estimate of what the p.f. may become after many years of exposure and use. high-voltage cables are not used in rigid conduit to the extent formerly (cables in interlocked armor have largely superseded them), ampacities for high-voltage conduit in stallations are not listed. Ampacities to 35 kV conduit installations are listed in NEC Article 310· Tables, along The ampacity ratings of the types shown in Table 10-7 for 35 kV and 46 kV are practically the same as those of 25 kV for installations in air, and only up to about 2 per cent less for direct burial, hence values for 35 kV and 46 kV are omitted from Table 10-7. Also inasmUCh as with ampacities for cables in :fiee air, direct burial and un<.!erground ducts. For both underground duct and direct burial special attention must be paid to the number of circuits and/or ducts. TABLE 10-7C Typical Ampacities of 25 kV Cables with Aluminum Conductors of Various Types and for Various Installation Conditions Shielded Grounded Neutral $i:I'!e 1C in Air i I Triplaxed lC al3 Three Cond. 1of3C 12) 131 (1)* : - - 148 170 '95 173 198 228 135 t55 178 ~{U 22' 4/0 . 259 """3 _30 204 2'" 350 500 750 1000 • . """ 353 440 567 m 'Tti lEiS , i - - iii: _208 ..!' 235 1 276 &>4 20U I 412 514 318 , 373 394 . 463 i 589 . 692 OW - 158 , 127 182 240 1! I """ 004 ~ -"00 1203 gooC - - 149 143 163 185 --= t57 170 195 ,203 211 240 263 292 ~ 318 359 . 22 3S8 454. • • .., 532 i 625 587. I 639 . 701 240 I . I 1Soc: 217 ~55 ;,uti RHO-90 100 LF Grounded Neutral I Triplexed 1Cof 3 2~2 I 757 I 806 Three Cond. 1 of 3C 7SQC - 90°C I _ i 1SeC • _ Triptexed: lC al3 1C m 16) 151" 7SoC 90°C 75°C 19ooc 2 1 lIU 210 lC i i gooC 175°C AmbientShielded ! Grounded Neutral Conductor AWG kem" 1 25 kV Directfy Buried 20°C 25 kV in Ouct 20°C Ambient-Shielded RHO-90 100 LF 25 xV in Air 40°C Ambient (9) IS)" gooC -= 1S"'C: 9O'C 75°C - - - i go'C I _ 139 . 12: I 134 , t6' 177 148 I t63 180 _tss L 1 8 152 Ull4 203 ' 168 _'86 H)I) 191 1,211. 2M 172 ~. 231 .6 233 204 196 217 240 239 264 265 211 232 2 222 300 241 273 253 220 . 243 I 298 270 291 i 329 298 2S4 292 304 360 325 360 • 35t I 428· 367 319 353 439 435 394 537 i 40B 392 433 . 537 450 I 626 I 467. 5t6 498 541 708 558 617 706 720 796 n4 790 873 852 , 942 i~ I 907 L 1000 L 126 143 163 18. 2tO 229 275 332 , ... """ :i ..., SOurce: JCEA P-45-426. FOOTNOTES FOR TABLES lo-7A. ·7B, and ·7C. Allowable ampacities are the maximum continuous ampacities under stated conditions, All ampacity values, except as noted, are from ICEA Publication No. P46-426 Vol. II for the nearest comparable cables. See Tabte 10-9A and 9B for ampacity values of two conductor concentrlc~neutf81 cables for direct burial# in duct and in air, Additional ampacity ratings and information on ampacitY calculations are available from leEA P-53-426 (NEMA WCSO) and Tables in NEe Article 310. *The Ampacity listing for single-conductor (lIe) cables assume$ they are $paced 7.5 in. ~nter·to-c:enter. or at lea$t one cable diameter apart, surface~to-$Urface, that shield is grounded at only one point With negligible $hield losse$ . ....These values are taken from an industry $OUf'Ce. The armor is of aluminum. tFor ampaeities of shielded 5 kV cables refer to cable manufacturer. Shielded cables usually have slightly more ampacity becau$e the metallic $hielding tend$ to increase the radial therma1 hat trensfer from the conductor. 10·18 25 1.89 1.00 0. -Table factors are derived from the following equation: MF= TC-TA. 400 C 200 C 200C 400C New Ambient Temperature MUltiply by the indicated factor to obtain the new ampacity for the new ambient temperature: acc IOOC 200C 300c 400C 500C Multiplication Factor (MF) 1.46 1.00 0. 75 0 C 9()OC 750 C Ambient Temperatur.89 For example: A cable may have . 89 amps.09 1.13 1.(MF) where: II 12 TC ~ ampacity from tables at ambient TAl = ampacity at desired ambient TA2 conductor temperature in degrees C TA1 = ambient from tables in degrees C TA2 = desired ambient in degrees C 10·19 .00 0.26 l.07 1.17 1. The same cable operated at 900c conductor temperature in a 3QoC has an ampacity of 109 amps.34 1. ambient.09 1.00 0..e5 1. 12 = I.produd c1(>ssification and technical data TABLE 10-8 Adjustment Factors for Ampacity Values in Table 10-7 for Variations of Ambient Temperature The following factors· may be used to adjust ampacities for various ambient temperatures: If me ampacity is known for: Conductor Temperature 900(.1e 1.13 1.36 1. known ampacity of 100 amps when operating at a 9()OC conductor temperature in a 400c ambient. while in a 500(.93 1. 16 ilL 1. The left-hand entries of any pair are ampacities when directly buried.16 1. - 90OC _ • 190-135 215·155 245·170 280-200 I 210-150 240·170 275-195 315-225 Ampacity v. J i_ 14~~105T The right-hand entries are ampacities when in duct.09 1. 1. 75 percent Load Factor Cable Cable in Buried Duct 1. *Multiplying Correction· Factors for Load Factors of 75 and 50 percent Cable Rating kV 5kV 15 kV 25kV L --. 15 kV 9O'C 35 kV 0 O 75'C 90 C 75 C -~ 132-88 I 174-115 ..covered and insulated aluminum wire and coble TABLE 10-9A Ampacities of Two·Conductor Concentric·Neutral +Underground Distribution Cable for Direct Burial and for Installation in Buried Duct (see Figs.. 10-20 .04 50 percent Load Factor Cable Cable in Buried Duct 1.04 1. those 25 kV and 35 kV are from other industry sources. Conductor Size AWG or kcmil 4 2 1 110 2/0 3/0 4/0 250 300 I 5 kV 75'C • 120-80 158-104 181-120 205-136 232-156 264·177 304·205 336-229 379-260 I 90'C 75'C 2Sk~ .08 1.08 ~~- I .. ..lues for 5 kV and 15 kV cables are from ICEA tables.04 1..07 +Refer to The Aluminum Association's Aluminum Underground Distribution Reference Book for additional typical information. 10·17 and 10·18) Ambient Temperature 20°C Load Factor 100 Percent" The 7S'C ratings apply to cable with Hi-Mol Polyethylene Insulation.16 1.. The 90'C ratings apply to cables with Cross-Linked Polyethylene Insulation. 199-132 I 226-150 256-172 291-195 335-226 370-252 418·287 128-91 168-119 193-137 218-155 248-177 284-201 324-230 360-257 403·291 116-83 152-108 175-124 198-141 225-161 258·182 294·209 327-233 366·264 . i 165-120 190-135 215-155 245·170 280-200 310·220 350-250 165-115 190-135 210-150 240-170 275-195 315·225 350·250 395-280 ..07 1. 10·21 . in air. AWG/kcmil 4 2 1 110 2/0 3/0 4/0 250 300 5kV 75¢C 75-65 103-86 119-99 137-112 159·128 181-146 212-169 238-188 273·214 90°C 90·76 120·100 139·116 160·131 186·149 211·170 247-197 278·219 319·250 15kV gooC 75'C 81·68 95·79 107-88 125·103 124·102 145·119 142·116 166-135 163-132 190·154 187·151 : 218·176 217-172 i 253·201 244-1931285. to cable with Cross· Linked The left-hand entries of any pair are ampacities for cable only in air.product classification and technical data TABLE 10-9B Ampacities of Two-Conductor Concentric-Neutral Underground Distribution Cable when Installed in Air or in Duct in Air (usually as leads from an underground buried or duct installation) (see Figs. The right·hand entries are ampacities when cable is in duct.225 278·218 324·254 Ampa. 10-17 and 10-18) Ambient Temperature 40° C The 75'C ratings apply to cable with Hi-Mol Polyethylene I nsu lation. The 90°C ratings apply Polyethylene Insulation. Cond.lty values are from ICEA tables. . most of the problems encountered in the field are at connections. seq. However. Therefore. In the joining process. A· similar record can be attained with insulated alu minum conductors if there is proper attention to the connecting methods. several differences in installation practices must be fol lowed. in Table 11-1. . Aluminum wire and cable are available in sizes to meet all needs and with the same types of insulation as copper (See Table lI-l). the type of connector.. In this respect the use of joint compound is most important. Aluminum Conductor Connectioll$ The electrical conductor has no functional value until it has been properly connected to complete the electrical circuit. the dimensions for a wide range of sizes and various types of insulation are listed. This fissured contact surface must be entrapped and collapsed against the adjoining contact member to establish metal-to-metal conducting areas. The method of '" FOr further infonnation On the installation of aJuminum building wire see the AA bookIet "Aluminum Building Wire Instailation Manual and Design Guide. Experience indicates that. and connectors designated "AL7CU" or "AL9CU" are available as stock merchandise in leading supply houses. Aluminum building wire installation procedures are basically the same as those for copper. inside build ing walls. application of added protection. Connectors for all types and sizes of aluminum conductors and equipment with suitable ter minals are available. service drop. under some circumstances." connecting** a single wire or cable (or the individual conductors of a multi-conductor cable) to other conduc tors or to switch-gear depends on the size of the con ductor. because aluminum is a different metal "ith different properties. Connectors tested and approved for aluminum conductors must be employed and equipment to which aluminum conductors are to be connected must have terminals intended for use with aluminum conductors. and whether the compo nents to be joined are both aluminum or one is of another metal such as copper. apart from damage due to faulty installation or operation. it is apparent that care taken in making a proper termination or splice is time well spent. page 11-11 et. The performance record of aluminum on overhead transmission lines led to its use in conductors of other types so that today most overhead distribution. splicing and terminating will refer to conductors in circuits above 1000 volts which require not only connecting the separate conductor elements. Splicing and terminating are described separately. for convenience. insulated aluminum cable has corne into wide spread use in underground distribution and building wire applications. Its main function is to prevent the entry of moisture. More recently. Or in cable trays or conduit. The types and electrical properties of wires and cables used in secondary distribution and interior wiring circuits are listed in previous chapters. However. . but also the restoration of sometimes complex installation systems over tbe splice or terminal and. the joining process must protect these conducting areas against the degrading effects of service. Electrical connections are particularly vulnerable to this when the $>/I For purposes oftbis discussion. In addition. Today virtually all overhead transmission lines have conductors of aluminum or alu minum reinforced with steel (ACSR). the oxide film on the contact surface of the aluminum must be ruptured to expose base metal.-. The basic function of extending the conducting path is the same whether the conductor is bare or insulated. Such equipment. overhead or underground. UL-listed and designated for use with aluminum or copper conductor (ALlCU).Section III Covered and Insulated Aluminum Wire and Cable Chapter 11 Installation Practices* Aluminum was first used on an overhead transmission line more than 85 years ago. and service entrance cables are aluminum. 060 .590 .8659 . In.050 1. .360 .725 .423 .060 1000 TypeTHW Approx.) In this. Area I Inches Sq.390 .0730 .3267 .0394 .877 700 61 . Pressure connectors are of two basic types--mechan ical screw type and compression type applied with a tool and die.4128 .050 .260 .2733 .224 . Inches Sq.670 . Aluminum Building Wire (Taken From 1987 NEe) Bare Conductor*" Number Size Oiam.335 .1017 . The con nectors are usually plated to avoid the formation of oxide and to resist corrosion.4536 . the reader is referred to the bibliography at the end of Chapter 13.985 1. power is off and the conductors are cool. Various styles are available.268 2 7 19 . Diam.1590 . Oiam. 11-1.6151 . UL 486B.1924 . Area Oiam.590 .1963 .775 .4015 .659 500 . To the extent these are accomplished. Approx.1590 . has been revised.465 .720 . Artide 310-14 of the 1987 NEe calls for AA 8000 series electfical grade aluminum aHoy conductor material.2332 .169 6 .1698 .5281 .685 .736 37 .940 . Building Wire Connectors Only pressure-type connectors marked AL7CU or AL9CU to indicate they have been tested and are listed by UL for aluminum.500 .9076 1.213 4 7 . AWGor of Strands Inches KCMIL .2780 . Connectors for every conceivable need are available.475 410 19 250 .305 . Area Inches Sq.134 7 8 7 .1352 . the connection will have low and stable contact resistance during its service life.9331 1.0510 .595 .865 . follow the mannfacturer's instructions carefully.820 .230 1.6082 . 11-2 UL Slandard 486.960 1.415 . copper.305 .800 .4656 .0660 .450 .613 61 600 61 .255 .660 . Installers are also advised to contact conductor manufacturers for recommendations concern ing specific connectors for use with their products.0452 .9676 1.616 400 37 .760 . along with special tools.5026 .450 .5876 .6859 1.0730 . Some typical connectors are shown in Fig. A number ofconnectors have already been tested under the more stringent re quirements of the new standard. In.545 .376 3/0 19 .075 1. Compression connectors similar to those used for bare conductors (see Chapter 5) arc widely used for con necting insulated conductors (Fig.570 37 350 37 . Approx.3525 .285 1.2733 . and are currently available.5216 .0881 .520 37 300 . covering connectors for use with aluminum wire. although many contractors believe that compression con nectors are less susceptible to installation error.6939 1. as in preceding chapters.0530 .240 . 11-1).1352 .1194 . Both basic types are suitable for usc with aluminum.3421 .110 1.8659 .1885 .715 .1682 Size AWGor KCMIL 8 6 4 2 1 liD 210 310 4/0 250 300 350 400 600 600 700 750 1000 'Ou'l'lensioos are from industry $OUrces uCompact conductor per ASTM B 400.2968 TypeTHHN Approx. Both types are designed to apply sufficient pressure to shatter the brittle aluminum oxide from the strand sur faces and provide low resistance metal to metal eontact.815 . or aluminum to copper connections interchangeably should be used.1017 . Which ever type you use.0386 1.2290 .770 . Depending on .540 .2370 I TypeXHHW Approx.540 .908 750 61 1. representing the "system" of a particular manufacturer.050 .4717 .7542 . we will first consider conductors for secondary circuits (0 to 1000 volts) and the installation practices associates with them.645 . Installers are cautioned to avoid mechanical pressure connectors with too wide a range of wire sizes because the screw may not adequately engage the strands of the smaller conductors.255 - .490 . Compression Connectors Aluminum conductors are particularly suitable for con necting to each other or to an equipment terminal by use of solderless compression type sleeves because the con ductor strands tend to weld together as a result of high compression pressure. Approx.336 2/0 19 .360 .495 .299 1 110 19 . .860 .covered and insulated aluminum Wire and cable TABLE 11-1 Nominal Dimensions· and Areas. (For more information on electrical contact theory.7620 . In.290 .2290 . .4071 .150 1.415 . 4. Mechanical connectors should be tightened to manufac turer's recommended torque levels.2. The setscrews are of the Allen head type and tightening of screws or bolts by wrench compresses the aluminum conductor strands against the side wall of the Building Wire Terminations UL-listed terminal lugs marked AL7CU or AL9CU are used to connect aluminum conductors to transformers. 2. 11-l. 11-2. compression is obtained by use of hand tools Or from hydraulic pressure. values in Table JI-2 should be followed. The following procedures should be used: I. also provide a rapid means of making connections particularly where space is limited and where many taps are taken from a main as in panel boards or junction boxes. Fig. Scratching the plated surface is likely to remove the plating. Mechanical terminal lugs that are copper bodied and tin plated should not be used with aluminum conductors larger than #6 unless they have passed the 500-cycle requirements of new UL Standard 486B. Like connectors. It should be noted that zinc plated connectors have an adverse effect on aluminum and should never be used on systems where aluminum wire is used. switches. Alumi num terminals are usually plated and plated connectors should not be scratch-brushed or abraided. In the absence of manufacturer's recommended torque levels. Aluminum connector bodies are ma chined from extruded high-strength aluminum. sluds. Mechanical Connectors Pressure connectors of the setscrew or bolted mechan ical type. Type A plain. TEE OF! PARALLEL TAP Fig." All equipment should be furnished with CL-listed. causing the strands to intermingle. Nuts should be aluminum alloy 606I-T6 or 6262-T9 and conform to ANSI B 18. bus bar. 3. all aluminum terminals. standard wide series conforming to ANSI B27. 11-1 Connectors have been de signed and manufactured for every conceivable contingency.installation practices Compression Connectors r!Es SPLICE recess. 11-3 . IJ-3.2. they are of two basic types-me chanical screw type and compression type applied by tool and die.2. Care should be taken that the conductor temperature and ampacity ratings are compatible with the terminals and equipment to which they are to be connected. 11-2. Connector Plating UL standards require that connectors for use with aluminum conductors be plated with tin or some other suitable contact metal and the face of any pad or lug that is plated should not be scratch-brushed but merely cleaned with a suitable solvent cleaner. Washers should be fiat aluminum alloy Alclad 2024 T4. Aluminum bolts should be anodized alloy 2024-T4 and conform to ANSI BI8. They are applied to the conductor ends in the same manner as described under "Connectors.1 specifications and to ASTM B 211 or B 221 chemical and mechanical property limits. Make sure connector is UL listed for alumi num. such as 6061-T6.2 SAE or narrow series washers should not be used. the size of the conductors. motors and other equipment. When all components are aluminum (bus. Hardware should be assembled as shown in Fig. Some typical terminal lugs are shown in Fig. lugs) only aluminum bolts should be used to make the con nections. Fig. MECHANICAL COHH£CTOR$ TAPS TfES CROSSOVER. use the highest torQue value associated with the different tightening means. For slot lengths of intermediate values. select torQues pertajn~ ing to next shorter slot length. 11-4 . select the largest torque value associated with conductor size. The same values apply to pressure connectors tor both copper (UL Standard 486A) and aluminum conductors.gofl. for a slotted hexagonal head screw.UGS 1f? ~ ~ ~ ~ p. e COMPRESSION TERMINAL L.L Inder"lted CompreSSIOI'I Versa·Crirnp Fig. 1 Q and Lar98rb Hexagonal Head· External Drive Slot Width-Inches Socket Wrench Over 3/64 To 3164 Split-Bolt Othsr Sfo~length-Inches To 1 4 Over 1/4 Connectors Connectors 75 20 35 60 75 40 60 25 110 45 165 35 110 45 165 275 150 50 275 150 60 275 150 50 160 385 50 160 385 50 250 50 500 50 500 250 325 650 50 325 650 50 325 50 650 325 50 625 625 375 50 1000 375 50 375 50 1000 375 1000 50 500 1100 50 500 1100 50 500 1100 50 500 1100 1100 600 1100 600 1100 600 : - - ----- - - - Note: The torque :ab!es presented here are taken from UL Standard 4868. Pound-lnehe$ Slotted Head No. 8 6 4 3 2 1 1/0 210 310 410 250 komi! 300 350 - 400 500 500 700 750 600 900 1000 1250 1500 1750 2000 Toraue. :~': 18·10 AWG Torque For Slotted Head Screws. but are representative of Ihose pL. 10 For Use With No 10 AWG or Smaller Conductol"$ Torque-Lb·lnches Screw Slot LongthInchesc To 5132 5132 3116 7132 114 9132 9/32 + Screww$lot Wklth-lnche5 Less Than 3164 More Than ·3/64 7 7 7 7 9 9 12 12 12 12 15 20 -- Torque For Socket Head Screws'" Socket Flats~ Torque. b. Typical plated aluminum terminal lugs corne in variety of styles. Pound- 'nehss Inches 1/8 5132 3/16 7132 114 5116 318 112 9/16 45 100 120 150 200 275 375 500 600 Size Across a. in NEMA equipment installation instruction publications. Smatter Than No. For values of slot width or length other than those specified.. and In the Canadian Electrical Code. c" ~ DiaMond eire um1erefltl a: He/ll.covered and insulated aluminum wire and cable Terminals SCREW·TVPE: TERMINAL LUGS o ~ ® ! . c. Clamping screws with mu!tiple tightening means: for example.bllshed in other UL Standards. 11-2. TABLE 11-2 STANDARD PRESSURE-CONNECTOR TORQUE TABLES Tightening Torque For Scrsws. torque values listed in UL 486 Standards should be used. SAE or narrow series washers should not be used.installation practices TABLE 11-3 Lug Bolting Torque. Actual installation conditiQns will vary considerably. then a steel bolt should be used with a Belleville spring washer to allow for the differing rates of thermal expansion of the mate rials. li4 11/16 5/16 13/16 3/8 15/16 1/2 1·3/. In the absence of such recommendations. class 28. Belleville conical spring washers come in sizes for use with bolts ranging in sizes indicated in Table 11-4. The steel bolt should be plated or galvanized. 2. The following procedures should be used: 1. Type A plain standard wide series. quenched and tempered equal to ASTM A 325 or SAE grade 5. 6 11 30 40 55 'From Ut 4S6 Standards. conforming to ANSI B27.0. 11-5. bolts should be tightened sufficiently to flatten the spirng washer and left in that position. Flat washers should be steel. threads to be unified coarse series (UNC). no torque wrench is required and washer will be flaHened.070 .16 5/8 1·1/2 Thick ness Lb. torques may 'fary widely atld resu!! . 11-3. 7. con forming to ANSI BI8. In-Ibs. All hardware should be suitably lubricated before tightening. AlumllHJm 6 Alumit'lum Bolt Washer 5/16 318 7116 Bus tug Wbshel 19 112 5/8 or more Nut Fig. 11-5 . medium carbon steel heat treated. 4.' Bolt Diameter 'nth Tightening Torque Pound·Feet 1/4 or less 1 AlumInum 2 Alummum 3 Aluminum 4 A!ommum 5.2.I'> high (lon-tacl resistance <1. When all components are aluminum. All hardware should be suitably lubricated before tightening. 3. Hardware should be assembled as shown in Fig. In this manner.1 joinls. Nuts should be heavy semi-finished hexagon. 5. 6. Bolts securing lugs should be tightened to the manu facturer-s recommended torque. nom. 6. Bolt should be tightened until a sudden increase in torque 1$ felt.20C 222·250 Note: Torque valueS to be used as guides only. 5. TABLE 11-4 BELLEVILLE SPRING WASHERS Bolt size 0. In the absence of specific manufacturer's instructions. HOTE: Ii bOilS are nOllubricaled with sUiton spray Cf clner suitable lubricant.2.2. aluminum hardware should be used and installed as above. Materia!: Hardened Steel Table Courtesy of Thomas & Betts Co. (See Table 1I-3) If adding to an existing installation containing copper bus or studs or if it is impossible to obtain the required equipment with aluminum terminations.085 100 1400 2700 4000 125-150 150·175 175. load torque to flat to flat 050 060 800 50·75 WOO . large compression type lugs. Where possible. 11-8. preferably with two holes. 11-6. Belleville washer is used to make an aluminum-ta-copper or steel joint. Aluminum IY ~ BlI$ (or stud) 2 Sfe1'l:1 or CQPper St"". An AL7CU or AL9CU compression type connector is used to make the splice. Fig. With other than aluminum bolts.covered and insulated aluminum wire and cable ~lO @@~ 5\ t 2 3 . must employ short copper stub spliced to aluminum cable. The aluminum bolts should be of alloy 2024-T4 and the nuts compatible. 11-6 L___~~~~~:. Belleville spring washers and heavy flat washers in consecutive arrangement as shO\m in Fig. Because of the differing rates of thermal expansion of aluminum and other conducting or support metals. bearing on the aluminum lug. St~iJl Flat Washef Fig. 11-7. 5. Steel Selleville 6. NC (coarse) threads are preferred for the 2024-T4 aluminum bolts. Gutter splice is used when terminal lugs are not removable and are approved for copper cable connection only. 5-2). though preferably not of identical alloy and temper. fi \ Crown Facu "ut t. 11-6). Fig. current transformer terminals should be re placed with compression type (B). There are a number of UL-listed adaptor jittings available for use with terminals not suitable for direct connection of aluminum conductors. it is preferable to have all parts of the circuit. 11-5 must be used. is necessary. a "gutter splice" may be used to connect the aluminum conductor. section of copper cable should be spliced to aluminum (AJ. Fig. 11-4). With equipment having terminals that will accommo date only copper conductors. For connecting large aluminum conductors (500 kcmil and up) to heavy equipment having copper terminal studs and/or pads. If not possible /0 remove. More information about aluminum bolted connections will be found in Chapter 13. onc of the many UL-listed AL7CU or AL9CU adaptor fittings specifically designed for this purpose may be used (Fig. 11-5. and the copper conductor stub is then connected to the equipment terminal (Fig. should be used in making such a connection (Fig. including studs and clamp bolts.. Note: Crown of Belle ville washer should be under the nut. 11-9. If aluminum bolts and nuts are used. The aluminum conductor is spliced to a short length ofcopper conductor. Bolts and nuts should be of heavy series design to reduce stress beneath the head. JI-4. Sleel Nut Fig. Figures 11-7 to 11-12 show some typical connections of aluminum conductors to equipment terminals. Power transformer ter-: minals.:::!:=-_J . Components should be assembled as shown in Fig. only the heavy washer. Instead of a gutter splice. 3. if copper. of aluminum. AI"minvM Lug 4. Care must be taken not to nick the wires when removing insulation in order to avoid broken strands in installation or service. Where bolt is steel or copper. but not from the joint itself where it will serve to prevent air from entering. or the setscrew of a mechanical connector tightened. and the smaller sizes may be fastened under a binding head screw* (without joint compound) after looping in a clockwise direction. However the equipment in which they are installed must indicate suitability for use with aluminum and connector tightening torques. Making Connections Preparation of aluminum conductors for connection to an equipment terminal or another conductor requires stripping of the insulation and rupture and dispersal of the nonconducting oxide film that appears quickly on a fresh aluminum surface exposed to air. If the connector does not come factory-filled with an acceptable joint compound. easy removal of insulation. Excess com pound should be removed from the conductor insulation. 11-16. 11-12. is shown in Fig. Belleville washer is nec essary (B). Basic Installation Techniques 1. Abrading the conductor strands with a wire brush or other appropriate tool will serve to clean the conductor and disperse the oxide coating prior to application of joint compound. All terminals are pref erably aluminum.n in Fig. a fiat washer. Stripping Insulation Never use a knife or pliers to ring a conductor when stripping insulation. such paste should be applied to the conductor end before insertion into the connector. Fig. The conductor end is then inserted into a compression sleeve of adequate thickness or a suitable mechanical type pressure connector. (Some manufacturers' con nectors may not require the use of compound but it should be used in the absence of specific instructions to the contrary. Another method is to skin the insulation back from the cut end of the conductor and then cut outward (Fig. Several types of insulation stripper are available for quick. One type is shov. When connecting alu minum conductors to a unit sub stalion with copper bus. in a manner prescribed by the connector manufacturer. 11-7 . Belleville washer is used with cop per or steel studs. 11-15. 11-14).) The compression sleeve should then be compressed with a hydraulic compression device. and a Belleville washer (B).tl types of insulation stripper are available for quick. Copper primary leads on trans former are connected to aluminum feeders in aluminum connectors and bolted back-to-back using a steel bolt. 11-10. useful for small size conductors. Three methods of mak ing motor connections are shown in detail A. use compression type aluminum lugs attached with a steel bolt. 11-13). Copper lug connections on switchgear are rep/aced with equivalent aluminum connectors. a fiat washer. 11-9. easy penciling or square-cut removal of insulation. Fig. One way to avoid this is to pencil or whittle the insulation (Fig. 2. and a Belleville washer (A). Solid aluminum wires are prepared in a similar manner. Sevel". * Note: The ALiCU or AL9CU marking is not required on equipment connectors.installation practices Fig. One of these. Pulling Conductors in Conduit or Electrical Tubing The following procedures are applicable to conduit of all types including aluminum: a. Attach the pull line to the conductor or conductors. Penciling tool for removal of insulation in bevel configuration by rotation.covered and insulated aluminum wire and cable Fig. In making connections. which have comparatively thick insulation. If the connector is a mechanical screw type. Use wire stripper for removing insulation from smaller wire sizes. Insulation should be removed as one would sharpen a pencil. Run a "fish" line through the conduit. Attach a clean-out brush to the fish line and behind it attach the pull line. c. Then tape the joint as instructed under Section BZ Or apply the inSUlating enclosure that comes with some types of connectors. which by proper selection ofbushing are applicable to all usual sizes of cables. 11-17). 11-19). Another safe way of removing insulation from conduc tor is to peel the insulation back and then cut outward. Then apply joint compound if it is not already contained in the connector. Polyethylene fish tapes may be used for shorter runs up to about 100 feet. crimp it as recommended by the manufacturer (Fig. Another method is to push a round flexible speedometer type steel wire through the conduit. Fig. first strip the insulation as instructed heretofore. This may be done by attaching the line to a piston-type device which is propelled through the conduit by compressed air. Wipe off any excess compound. 11·13. use UL 468B torque values shown in Table II-I. 11-14. Several sizes are avail able. . then pull both through the conduit by means of the fish line. 11-8 b. A basket grip over the insulation may be used for this purpose (Fig. This tool is particularly suitable for primary cables. Be sure to select the correct size die and close the tool completely for full compression. Never ring a cable-it may lead to a break. 3. 11-15. Fig. 11-18). Match stripper notch to wire size. appJy the manufacturer's recommended torque (Fig. In absence of specific torque recommendations. Fig. 11-16. Ifacompression type. to reduce coefficient of friction and required pulling tension. Proper torque is impor tant-over-tightening may sever the wires Or break the filling. 11-20). Where conductors are pulled with a rope. 11-18. Failure to close crimp ing 1001 will lead to an unsatisfac tory and weak joint. stagger reels. Basket grip.installation practices Fig. plus those appli cable to conduit: a. do not ring cut the insulation. Installation of Cables in Trays Where aluminum cable is to be pulled in trays or cable racks. cover them with rubber-like or plastic tapes to prevent scoring of the trays and installation sheaves during a conductor pull. Follow all NEC requirements. To avoid this. to allow gravity to assist in pulling with reduced tension. 4. Fora detailed description ofcalculating pulling tensions. 11-20. Crimping tool must be fully closed. Cables installed in trays should follow the require ments of NEC Article 318 for the aUowable number of cables permitted in trays and their respective ampacities. When conductor ends are prepared for pUlling. one behind the other. skin the cable ends and stagger them after locking with tape. to reduce the required pulling tensions and to prevent damage to stranded conductors or insulations. 11·9 . to maintain equal pulling tensions and prevent conductors from "crossing over" and jamming in the conduit. be sure straps or other cable anchoring devices do not cut into the insulation. Use large-radius sheaves around bends and smaller sheaves on the straight sections of cable support trays to facilitate cable installations. Fig. pencil the insulation for removal. to reduce pulling tension. j. see the example given on page 11-11 on underground installations. Fig. This will hold tie to a minimum cross section. 11-19. c. £. d. See Chapter 17 for a complete treatment of aluminum conductors in conduit. Where cables are anchored on trays. . 11-17. k. Have pulling equipment with adequate power available to make a steady pull on the cables without "jerks" during the pulling operations. Damaged strands can reduce the pulling tension capabilities of the conductor. as described above. take the following precautions. I. while feeding in conduit. pull conductors in a downward direction. Use pulling compound compatible with the conductor insulation as the conductors are fed into the conduit. Fig. stagger the conductor ends and anchor in position with tape. Try to feed conductors into conduit end closest to the sharpest bend. g. to provide maximum lIexibility around bends (Fig. e.) d. be sUre not to nick the stranded aluminum conductor during insulation removal. (See Table 11-2. h. For single conductors on a reel. under tightening may lead to overheating and failure. b. When a rope pull has to be used. Wherever possible. Where pulling attachments are used on the conductors. 000 2. 11-20). SOme lubricating materials have been found to adversely affect cable insulations or outer jackets. by placing a basket grip around the conductors' insulation (Fig. Hard pulls can be eased if the reel if hand controlled and slack cable is guided into the conduit. Such bends should be made before the terminal is applied to minimize electrical contact distortion. Be sure tray supports are capable of handling maxi mum weight of conductors and planned conductor additions in the future. Conductors in Vertical Raceways The NEC under section 3()()"19 stipulates that conduc tors in vertical raceways shall be supported. Table 11-5 indicates the mini mum bending radius as a multiple of the overall cable diameter. 6. (b) Flat Tape and Wire Armored Cables The minimum recommended bending radius for all flat tape armored and all wire armored cables is 12 times the overall diameter of cable. except as noted below (c) for tape shielded cable. As a general rule one cable support shall be provided at the top of the vertical raceway or as close to the top as is practical plus an additional support for each interval of spacing as shown in Table 11-6. Steel pull cables used to pull conductors around bends in aluminum conduit runs may damage the conduit at the bend. An exception to this rule is that if the vertical riser is less than 25% of the spacing listed in the Table. or by tying the line to a loop in the uninsulated part of the conductor (Fig.001 and over 155 and less 170 to 310 325 and over 4 5 5 6 7 6 7 8 I POWER CABLES WITH METALLIC SHIELDING OR ARMOR (a) Interlocked Armored Cables The minimum recommended bending radius for all interlocked armored cables is in accordance with table above but not less than 7 times the overall diameter of the cable. Minimum Training Radii Where permanent bends are made at terminations using aluminum building wire. Minimum Training Radius Thickness of as multiple of cable diameter Conductor Insulation Overall Diameter of CAble-Inches mils 1. 11-21). nO cable support shall be required. Aepfi:'lted loon ICEA 5-66-524. 5. (c) Tape Chielded Cables For ali cables having metallic shielding tapes the minimum recommended bending radius is 12 times 1I1e overall diameter of the completed cable. Installing Cable in Conduit or Duct Theprocedures forinsertinga "fish" line or tape through a conduit or duct.001 to 2. 11-10 N£WA WC-7 .000 and Less 1. followed by a pull line andlor cable as required for the pull.covered and insulated aluminum wire and cable e. are well known and established as field practice and do not need extensive description here. The minimum recommended bending radii as muHiplies of 1I1e overall cable diameter given in the following tabulation are for both single and multi-conductor cable with or without lead sheath and without metallic shielding or armor. Straight cable tray runs may often be installed by simply laying thelightweight aluminum cables in place. f. on Sheaves or While Under Tension POWER CABLES WITHOUT METALLIC SHIELDING ON ARMOR. Pulling tensions may be reduced by lubricating the cable surface. this TABLE 11-5 TRAINING RADII For 600 V Cable Not in Conduit. This is often avoided by using steel elbows with aluminum conduit or by use of a pull line that will not damage aluminum elbows. In addition to cable pulling compounds. Aluminum conductors may be attached to pull line or cable by means of a factory-installed pulling eye. (d) Wire Shielded Cables Wire Shielded Cables should have the same bending radius as power cables without metallic shielding tape. Pulls should be accomplished with steady tension and pulling speeds not exceeding 50 feet per minute. However. according to the arrangement in Fig.718) f = Coefficient of friction = L The maximum aJ~owable pulling tension. The ma. Coefficietlt of friction=O. lb per ft Coefficient of friction Note: For a wen constructed conduit or duct with a lubricated cable.87 Ib per ft Cable diameter.!=L w The following formulas can be used to calculate the maximum allowable tension that should be applied to the cables. Ib = + Example: Determine the maximum pulling tension required to install three single-conductor cables in a duct. eta.690 in. Ib PI =:: Tension for straight section at feeding end. or duct bends (to prevent cable damage becallse of rubbing on sides of bend) must not exceed the following: I'b where Pt> r = = = 100 r (Eq. A number of proprietary wire puUing lubricants and compounds are UL-listed and labeled to indicate the compound's compatibility with conductor coverings. 4. The maximum allowable pulling tension (Pm) cannot exceed 1000 Ib where cables are pulled with a basket grip. 11-22. however. It should be kept in mind that tension developed for straight runs per unit length is less than that for the portion of the cable in bends. For less favorable conditions or with considerable curvature. (Eq. 1'. 18 to No. compatibility of materials foreign to the insulation should be cleared through the cable manufac· turer. H·l) Maximum allowable tension. hard aluminum.OOS ·K 3. where p~ L (Eq. the tension per Eqs. For straight section of conduit or duct.Q. the pulling tension (lb) likely to be developed can be determined as follows: I'c 1'. the pulling tension (lb) likely to be developed can be determined as follows: Allowable Pulling Tension P!. Note that these allowable tensions assume the pull ing eye is attached to the conductor. the manufacturers' instructions should be ob· served. if the pulling eye is aHached to the conductor t = Pulling tension in straight section. B Not greater than 100 feet 100 feet NO. ~"\o ""'5 :. H·2) Maximum allowable bend tension. adhesives. ft Weight of cable (or cables). add the individ ual NA values) K Conductor stress factor = 2. CEq. 11-11 .6 to No 0 Not greater than 200 feel 100 feel No. If in doubt.>\iFf. In all cases. Ib Radius of curvature of the conduit or duct bend.5. 11-1 or 1 t-2 should nOL be exceeded.!:R " .instollation practices TABLE 11-6 SUPPORTING CONDUCTORS IN VERTICAL RACEWAYS From 1987 NEe Table 300·19 (a) Conduelors Copper Aluminum No. 00 to No.004 for Y2 or J.. "f" approximates 0. Circular mil area of each conductor (If conductors are of various sizes. The cable specifications are: Three single conductor #4/0 AWG 600-volt aluminum cables with cross-linked PE insulation = Weight. 3 @ 290 Ib/M It 0. etc.75.6 kernil to 350 kernil Not greater than 135 feet 60 feet 350 kernil to 500 kernil Not greater than 120 feet 50 feet 500 kernil to 750 kernil Not greater than 95 feet 40 feet Above 750 kernil Not greater than 85 feet 35 feet applies to potting and joint compounds. Ib '" = Angle of bend in radians (I radian = 57. ft Note: The maximum aIIowable tension determined from Eqs. = t = '1' 5. 0000 Not greater than 180 feel 80 feet 211. Ib P::s = Tension for straight section at pulling end.5. "f" may approximate 0. Where the pulling line is attached to a basket grip that surrounds the insulation.imum allowable pulling tension for cable in conduit iI''. the pulling tension should not exceed 1000 100.:II 0. K value::::. For curved sections of conduit or duct.3 deg) e = Base of Naperian logarithms (2. 1l-4) where Pc Total pulling tension.4. lb where Pm Number of conductors being pulled simultaneously N A :::.008 for ~ hard aluminum conductors. 11-1 or 1l~2 should not be exceeded.t. tapes. H·3) Length of conduit or duct straight section. each 0. or 0. 5 f 0: 05 X 1.87 X 0.87 X 0.4 + (SO X 0. Dec.1 0.C. 11·3: At box (2) p. Using a single pulling eye attached to the three conductors and apply ing Eq.571 114: At box (5) p.5) = 263. and the tension at each bend is far below the 11-12 Installing Directly Buried Power Cables' If cable placement can be started Defore sidewalks and other obstructions are installed.llb recommendation per Eq.008 X 3 X 211.600=5078 Ib per Sq. Kellems Grip C.. II· I For the entire run from pull-box (I) to pull box (6). if the pull started at box (6). = 11·3: At box (6) P..S71 11-4: At box (3) p.5) = )J 7. X w X tJ == 95.2 X 2. Ib == L. == 117.tj~ or Doct Ckan. the final tension would be about half the above-found value. 11·21.5 X e 43. the plowing-in method usually is the most economical method of burying power cable. . 11~1.87 X 0.covered and insulated aluminum wire and cable A.2 • = 117. 95. 11-2 of 100 x 10. the reader is referred to R. == P. the *See also Aluminum Underground Distribution Reference Book.194=95. X w X t == 100 X 0.194 = 257.4 + (4. In this instance.5 == 43. Condt.2 Ib 0. or 1000 lb. Pulling cable in duct. Rifenberg. 1953. Study of such examples shows that there is an advantage in puning cables from the pull box or manhole closest to the first bend. X e = 43. This aids in reducing tension on the installed cable.7 Ib + (4. For a more complete treatment of cable puning in con duit. If soil conditions are unsuitable for plowing. 257. the tension increments are as follows: Sq../)Ot Brush B. "Job Famianed"' Pulling BlUk'et Fig. the maximum allowable pulling tension is Pm=0..1 + (15 X The total puning tension of 254 lb is far below the 5080 Ib limitation.5 x 2. AlEE Tran· sactions. Pulling cable between junction boxes of conduit installations is similar.4 11·3: At box (4) P. X w X f) = 257.$ X 1. of which special types are available for use in URD systems. to service entrances. even where moisture has gained entry into the conductor is some manner. If the soil is rocky. Joint use of trenches requires close collaboration on installation schedules but offers substantial economies to the sharing utilities. • See also IEEE Conference Record 31C35 Specia. Initially. Depth of burial ranges from about 30 to 48 inches for primary cable and from about 24 to 42 inches for sec ondary cable when buried separately.l Technical Conference on Underground Distribution. 3. Make sure that end seals are intact both while the cable is stored and installed to avoid entrance of water into the strands. under certain conditions describ ed in NESC Section 35.3 kV phase to phase. they apply equally to cable and cable in pipe: 1. a separation of one foot was required between primary power and communication cables and many com panies still require this separation. and bonded to the lightning arrester to avoid transient potentials. and also as an allowance for future repair.installation practices PULL BOX 50' PULL BOX Fig. Cable transitions between overhead and underground usually employ the conventional factory-molded pothead. Int is not sufficiently fine to closely cover the cable surface. Diagram o/circuit layout to illustrate method of computing pulling tension. and should extend at least 12 inches below ground. Article 354. or carefully laid in the trench from stationary reels. if at all possible. however. it should be screened to prevent cable damage. the trenches are shared jointly with other utilities. The trench should not be dug before final grading is determined. Care exercised in handling the cable during installation will help to avoid trouble later. Many of these precautions have to do with making sure there is no insulation damage. and tap connections in junction boxes and vaults are described in industry manuals. An amendment to the NESC. On many systems.' Practice is gradually becoming stand ardized in the direction of increasing reliability and lower ing installation and maintenance costs in this most im portant segment of power distribution. 11-22. so cable will not be exposed or be too close to the surface. should be payed out along the side of the trench from moving reels. both primary and secondary cables are buried in the same trench with no separation. Boards or slabs placed over the cable for mechanical protection should not be directly in contact with the cable but should be laid on an earth fill over the cable. Migra tion of moisture through damaged insulation in the presence of ac potential concentrates ions and promotes ac electrolysis. however. use of trenchers. The cable is not susceptible to corrosion failure when insulation is unbroken. Duct Or conduit also should be used under streets or where access by digging to a buried cable is not practicable. frost. if the insulated aerial cable is also suitable for direct burial. 11-13 . joint use with very long single-phase primary circuits is not recom mended because of the inductive pickUp of harmonics by the communication cables from the power cables. Such a cable can be carried directly down the pole. back hoes. The riser shield must be solidly grounded to the system neutral. a four-inch thickness of sandy loam placed under and over the cable will improve the heat radiating quality of the soil. In many areas. cables. If plowing is not used. 27~29. for damage sustained by the cable during installation has proved to be a major cause of subsequent cable failure. However. notably communi cations-both telephone and television cables. Many other practices relating to buried cables and their connection to transformers. Sufficient cable slack should be provided at risers and terminals to permit earth movement that may occur because of conductor thermal expansion. this fact has been determined in cable manufac turer laboratory tests and from research by utilities. 1966. The following suggestions will help to avoid failures from this cause. Riser shields or conduit should be used to protect the cable on the riser pole to a point at least eight feet above ground level. Sept. Or manual digging is custo mary. 2. A termination is not reqnired. permits random-lay (no deliberate separation) installation of communication and power cables in the same trenches with grounded wye power systems operating at voltages not in excess of 22 leV to ground ordelta systems operating at voltages not in excess of 5. To keep the cable pulling tension within safe limits. 11.. 6. Minimum bending radius for cables with metallic shielding tape is 12 Urnes the completed cable 00. but there should be a minimum cover of about 4 inches. DO. bearing pressure limitation may require larger bending radii for cable tension. a lubricant approved for use with the specific insulation and insulation shield should be used. Double check to make sure proper backfilling is done. to avoid shearing action when the soil settles. 8. the use of a pulling grip over the cable is common rather than a pulling eye or other attachment con nected directly to the conductor. 9. Aluminum connectors and terminating devices should be used with aluminum conductors so as to avoid differ ential thermal expansion and contraction upon heating and cooling that could result from the use of connectors of dissimilar metals. Make sure splices and other connections are made in accordance with manufacturers' recommenda tions.157 to 0. also to wire-shielded cable. Inch•• I Tlllcimess of Insulation. The National Elec trical Code Section 300-34 requires 8 times fot non-Shielded and 12 times for shielded medium voltage cable bending radiI. 10. The ob jective here has been to reduce the amount of skill and time required in the field so as to reduce the installation costs. risers. The conductor in 600 volt cables is not susceptible to corrosion failure when insulation is unbroken and moisture has not gained entry into the conductor. Check the cable visually for damage before burial or installation in duct. Compression type connectors and lugs applied with a tool and die are widely used. etc. however. ** Data apply to single and multiple conductor cable. If boards.001 and OYer 4 5 6 7 6 5 - i ! 7 S • Only applicable for cable training. 4. connections. Many of these precautions have to do with making sure there is nO insulation damage. (The bedding and cover can be omitted when duct in conduit is used). A 2-inch bedding is sufficient below. When moisture enters a break in insulation. Make sure boards are treated with pre servatives that will not harm the cable's insulation.000 2. and the need for heating and pouring of insulating compounds or extensive taping in the field has been greatly reduced. duct bend. When primaries are pulled into ducts or open trenches. Make every effort to provide more radius than these values at reel payout.000 and less 1. ac electrolysis begins. they should not be in direct contact. When doing permanent training make sure that the minimum bending radii are observed (see Table 11-7). (See Table 11-8).156 and Ie. 12. and air spaces minimized.313 and over I 1. plow guides. It is . Splicing and Terminating in Underground Systems The revolution in underground distribution system design has included the devices and methods used for making splices. Rock fill should be kept away from the cables to 11-14 prevent damage.. Inch i I 0. Don't overfuse the cable. many utilities prefer to use one-shot fuses as an added protective measure for the cable. In rocky soil areas. Compacting should be carefully done. Proof test the cable after installation to insure integ rity of insulation and splices. use screened backfill Or sand to protect direct buried cable. Duct should be carefully cleaned by pulling a plug through it to remove all burrs and obstructions. and terminations.covered and insulated aluminum wire and cable TABLE 11·7 I ICEA MINIMUM BENDING RADII' FOR POWER CABLES WlTHOtIT METAlliC SHIELDING'· I Minimum Bendine RHii as a Multiple of Cable Diameter cabl. 0. etc. 5.001 tD 2. are used above the cable for mechanical protection.312 0. Because of the paucity of failures. 7. More prefabrication is being done under factory controlled conditions. concrete slabs. which proved to be one of the most tedious and time-consuming jobs for the field man. Primary Circuits Termination of primary underground cables requires some type of stress relief. Step B Strip correct length of conductor insulation for the splice connector being used. Wipe away all excess oxide inhibitor. (a) Underground Direct Burial Splice 600 volt insulated cable splices are available for conductor sizes #6 A WG stranded through 1000 kcmil and can be completely installed and sealed without taping or compound filling.d cables : Rated Circuit Voltage Insulation Thicllnm (Mils) Proof·Test Voltage 1m 90 25 115 175 260 280 345 55 80 85 100 Installation . Their installation is straightforward and re quires no field cutting or hand taping for insulation or environmental sealing. below grade vaults. 11-24 shows a representative group of these fittings which are designed to accommodate a wide range of conductors. There are far too many types to describe them all in this handbook. Typical installation procedure is (Fig. Continue crimping to ends of splice. (b) Secondary 600 V Underground Terminations. pedestal or pad mounted equipment. They supply the needs of connectors required for residential or commercial use.insto/lation practices TABLE 11·8 ICEA RECOMMENDED de PRooF·TEST VOLTAGES (15 Minute Test) Polyethylene or Cross·Linked Polyethylene Insulat. bolted or compression fittings. Step C Wire brush exposed cable ends and then immediately 35 insert cables into connector. which can be installed in a fraction of the time. and in any combination. i : 2001· 5000 5001· 8000 8001·15000 15001 ·25000 25001 ·28000 28001· 35000 : important in installing these devices that a die of the correct size be used and full pressure be applied in order to obtain permanently sound connections. 11-15 . Fig. Start crimping splice onto conductor as per manufacturer's instructions. Then place the proper caps over each conductor end. Place splice housing over end of conductor and assemble one cap to housing. a couple of examples are given below to indicate the types of pre· molded splices and terminations that are currently avail· able for this type of service. Today most utilities use some form of preshaped Or prefabricated stress cone. the large ends should cover the knurled lines on both ends of the housing body. When caps are correctly installed. There are several different designs of connector products which are approved for use in underground 600 V electric power systems. For easier assembly of the insulating caps to the con ductor. direct burial. The threaded stud connector for transformers is such that the connector can be detached from the transformer without disconnecting the conduc· tors. 11·23) as follows: Step A Lubricate both insulating splice caps by applying a small amount of the supplied lubricant to the inside diameter of the cap at both the housing end and also to the inside diameter at the conductor hole end. these were made up by taping a stress cone. overlapping crimps 118 inch minimum. Step D Place housing with the assembled cap over splice connection and snap remaining cap in place on housing to complete the sealed splice. jt is recommended that the insulation at the end of the conductor be penciled before stripping. However. Large end of cap should cover the knurled line of the housing body. Initially. 600 Voll Secondary Clrcuils In this regard connector manufacturers have made important advances in the design of connection devices for secondary circuits. E--- . with designs for 15 kV and 25 kV following in 1985.. and porcelain types are used indoors while porcelain units are most often used outdoors.-H.HH+ SPUCE HOUSING ~~~-"~~'. One of the most significant developments in primary cable terminations has been the introduction of plug·in con· nectors for joining the cables to equipment or other cables. . and reliable method of connecting or terminating high voltage cables. Power cable loadbreak elbows in the 35 kV class were introduced to the industry in 1983. . LINES D.ATlNG CAP • rNO PENCILING ( REQUIRED .. l__________________________________________________________~c~ou_n_e~ .8~la~Ok~b_ria~n~. -~I~ ~ L STRIP lENGTH :os KNURLED LINES -----------. Secondary 600 V Underground Splice Kit showing sequence of assembly steps. KNURLEO :. INSU!. With these devices it is almost as easy to conncct a primary cable as to plug in or remove an appliance cord from a convenience outlet. 11·16 The concept of premolded stress relief takes the fab rication of a stress relief COre away from the field and into the factory with its controlled environment._ ----. Elastomeric con nections form a very convenient. __ .~-" $PUCE CONNECTOR INSULATING CAP • -.:i CAP IN4f¥SUI.C~O~_J Fig. Typical terminations for primary cables indicate that molded.ATIN. precut tape. leaving just the assembly to the field installer.covered and insulated aluminum wire and coble B. 11·23.:c. -f --. inexpensive. o ve seme Adepter cavit y 1. t ud of bllshing : "'Iat" side 01 Adapter mUSt be oriented to receive sel I c rews seu connector slips o ver Ad apUlr : All Adapters ha ve ~ 0-ring5 In Sealing Cep seal aro"nd Bushing Nec k and seu connector sam e 0 . Thr eaded Stud Sec ondar y Bush ing l \ Adapter Scr6W5 on threaded . there is avail abte today an array of premolded products that exhibit a high degree of safety . Fitzhugh's paper. and cable to cable connections. all seu con neclors h. Through the combined efforts of the connector and apparatus manufacturers and the utilities. 11-17 .0 . reliability. All of these com ponents are designed and tested to be in compliance with ANSUIEEE Standard 386-1985 Separable Insulated Connectors for Power Distribution Systems above 600 Volts . 0 . Fig . and flexibility.installation practices Set screw s In seu connector are light ened do w n on flat side 01 Adapter : pressure deforms Adapter to loc k CAP for porcelain bushings Ad~pter and threaded stud : b8 C k~d seu conneCtor to un screws can be -ofl Adapter and seu conn eCt o r removed from transformer without remo ving conductor from connector . //-24. Som e typical 600 V underground termination fillings.' ·See James W . "Exploring the Application of Premolded Products for High Voltage Power Sy stems:' Some typical applications of premolded products are at pulling or junction boxes. cable to equipment connec tons. The cloverleaf design allows the joint to operate at lower temperatures. Development work in s plicing . 11-26.345" Connector length '" 7" 5. Study splice drawing and instructions: 2. and ter mina ting devices is still proceeding. All splices and te rminations should be made by a qualified cable splicer in accordance with the manufacturer's instructions and recommendations. making sure th~t the insulation is not damaged during the re moval operation. Though recent trends have been toward the use of premolded splicing a nd terminating devices. 11-25 . Because of this the details of making a ha nd-taped . They are for a typical hand-taped primary cable splice . conditions ma y vary depending on the device . concentric neutral. it is still necessary or desirable in some circumstances to make hand-taped joint s by traditional methods. making sure that the conductor is not nicked durin g the removal operation. The following are the in struction s to be generally based in making the joint illustrated in Fig 11-27. connections.covered and insulated aluminum WIre and cable Prlo(o counesy 01 ELASTIMQLO Fig. st raight splice are given below.. Additional typical designs are shown in Fig. full instructions will be provided a nd should be follo wed . 11-18 3. being sure not to damage or kink them./'Iall Connector Z· 4% " 2A oj. TABLE "-9 Recommending Taping Dimensions Inlull- Ok.. Cut off excess cable at splice centerine.220" One. 6. While installation of premolded devices are si milar. Details of the joint are shown in Fig. Primal'( Voltage Circuits A cutaway view of an up-to-date power cable j0i nt is shown in Fig. In all cases. the cable. 4. Tem porarily wrap a number of turn s of tape over the outer concentric wires at least 18 inche s from the centerline of the splice.. Power cable joint for use af 15 k V or 25 k V. Train cables into final position and overlap for 18 inc hes to afford enough excess concentric wire for final jointing. and the manufacturer of the splice or termination. Remove the insulation from each conductor for a dista nce of (A + I) inches. a nd terminations. 11 -27. All traces of the semiconducting jacket must be removed by a nonconductive abrasive or rasp. connecting .. . Users thus are ad vised to keep posted on the latest designs being offered by the connector manufacturers in order to achieve greatest economie s in making cable splices.14'~ 3/8" lenglh 25KV One-tlall . Carefully unwrap outer concent ric wires and tem porarily remove them out of the splice area. / /-25 . 7.u A B 0 C K 15KV 175 P '" .2so" Connecl0r length 2W 5\14" 2A + 11\12" 7/ 16' 2A + 22" 9/ 16~ 35KV One-hall . I. Thk:k· . Remove outer semiconducting jacket for a di stance of (A + I + B + C) inches from each cable . 11-19 .installation practices Assembly of Tee Splice and Tap Devices • : : Straight Line Splice Disconnectible Straight Line Splice "'. Some typical primary voltage premolded splicing and terminating devices. 11-26. Loadbreak Elbow Connectors Modular Cable Terminator Fig. 11·27. 8. Remove all sharp edges from compressed connector. Apply one half-lapped layer of semiconducting tape (Bishop Tape No. Buff the insulation pencils if they are not smooth with a nonconductive abrasive or rasp. Friction Tape Half·lapped layer Seml·Conducting Self·Fusing Tape One Half·lapped layer Self-Vulcanizing Tape 10 "K" Thickn. fill the indents with a pliable insulation putty. Clean all exposed surfaces with a nontoxic and nonflammable solvent and allow to dry. If an indented type is used. Note: It is recommended that a smooth surface type connector be used--not an indented type. Tinned Copper Mesh Braid Two Half-Lapped layers Self-Fusing Rubber-Like Tape ·A = One·Half Connector length Fig. Details of a taped primary cable joint. Pencil the ends of the polyethylene insulation for a distance of (B) inches.) II. The tinned copper mesh braid . Apply the required compression connector on each cable. straight splice (conventional or cross·linked polyethylene insulated. Penciling tools will remove the insulation. starting at connector centerline and building up to the level of !be connector in areas between insulation pencil and connector by evenly wrapping tape back and forth across the connector.covered and insulated aluminum wire and cable Splicing*-15kV-25kV-35kV Primary Cables-Hand Taped Splice Single conductor with concentriC neutral. Apply one half-lapped layer of tinned copper mesh braid over the semiconducting tape and extend I inch at each end of splice. 17 or equivalent) over the exposed conductor and connector. Tape should just contact the edge of the cable insulation and be applied with enough tension to conform to the connector. (See Step 7 above. 9. Apply one hulf-Iapped layer of self·fusing semicon ducting tape over insulating tape buildup. tapering at the ends. Apply splice tape buildup to a thickness of "K" inches over the connector and for a longitudinal distance of "D" inches. Apply half. 13. solid or stranded) for grounded neutral service. since this may smear over the insulation surface. extending I inch beyond insulating tape onto !be semiconducting jacket on each side of splice.lf·lapped Laye. using a file Or heavy abrasive cloth. This step would be completed with a penciling tool.. Concentric Wires TwiSled & Spliced in Connector One H. The semiconducting tape should be applied with adequate tension. following the connector manufacturer's rec· ommended procedure. 14. Care must be taken in wiping the black conductingjackets. 10.. 11-20 12. Be sure not to cut into the insulation or damage the conductor during the pen ciling procedure.lapped layer of high voltage. as well as provide smooth penciled surface. self·fusing tape with manufacturer's recommended tension. 15. 14 AWG tinned or bare copper wire and tack solder in place... s'. 11-28). 20..--Stress-Re lie .. altbough porcelain potheads and semi-assembled. using two portions of tinned copper mesh braid. following the connector manufacturer's recommended procedure. indoor. making sure that the heat does not remian in one spot too long to damage the cable insulation or tapes. 11-28.. Both types provide extra insulation close to the actual termination ofthe conductor to provide protection against the extra voltage at these locations.-Insula. built-ut. 19. Primarily..0 Coble Insulo'lion o Ilir":--Conductor It-lt. Terminating Detail The construction details of secondary or primary cable terminations depend on whether the termination is out door. Single conductor outdoor termination B. ll-16) Stress-relief cones are also required in cable splices Terminal Lug o Terminal Lug o Insuloling Tope --IO!'~" Conduclor --+.installation practices should be wrapped as tight as possible. Apply two half-lapped layers of a self-fusing high voltage tape OVer the outer braid with minimum tension. Cone Mesh Shielding Braid Friction Tope Coble Shielding Tope --Hi:!c1--\J +----Jackel Jacket A. Twist the concentric wires together and cut off excess length.. Tie the concentric outer wires in place using wraps of No. Apply two solder lines 180 degrees apart for the full length of the mesh braid.ng Tope --1~ Insulating Tope Insuloling Tope Fflction Tape Friclion Tope Rain Rain Shield S~ield Mesh Shielding Braid Bios-Cui Insuloting Tope r-. Place the formed wires into the proper sized mechanical (or compression) connector and splice in place to form low resistance joint. 3-Conductor outdoor termination Fig.bj:. Apply one half-lapped layer of jacket tape over tbe mesb braid to the edge of the concentric wires at each end of the splice. or from underground and wbether it is horizontal for connection to an equipment terminal or ver tical for connection to another conductor..ess relief cones (or kits that facilitate tbeir qllick assemt:) _. and taping should be started at the centerline of tbe splice.. potheads of plastic insulating materials are used with primary and secondary URD systems. 11-21 . Terminations usually are either of the pothead type or the built-up stress-relief type.. 16.:--Insulaling Tope Melol Grounding Strap 1t1. 18. Typical terminations S-lSkV. (Fig.h~/. 17.e still used for this application. Trifurcating assemblies are also used for terminating a three-conductor cable so the urunsulated terminals are well separated (Fig. Fig. INTERFERENCE FIT Molded insulating EPDM exerts unffonn con centric pressure on insulation of cable to provide required creep·patl1 length and wa terseat 7. 5. 11-29. and if the installation is outdoor and vertical the addition of a rain shield to shed water from the cable insulation is customary. subject to such changes as appear in manufacturer's instructional manuals. Mter proper cable preparation. illustrating the component part ofa connector designed for conductors up to 25 kV. 3. Courtesy Amerace Corp. Actual creep distance is 18" (45. It is suitable for uSe on solid dielectric cables and can be applied directly on cables with extruded semi-conductive shields including full neutral concentric. 1. TERMINATOR HOUSING Molded of special EPDM compounds lor func tional reliability and long life. Typical single conductor molded pothead for cable termination. RETAINING WASHER Mechanically prevents any cable slippage within terminator. the variation of current density in the adjacent conductors creates dielectric stress variations that occur when a cable is terminated. CABLE INSULATION Primary insulation is provided since cable insulation carries through the terminator. 11-22 . The detailed methods of terminating shielded and non shielded cables closely resemble those used for splicing. Elastimold Div. MOLDED STRESS RELIEF Factory-tested molded stress relief assures proper stress relief for terminating cable. 4.115". 8. the terminal connector is slid down over the bared cable insulation until it bottoms On the cable shield.covered and insulated aluminum WIre and cable where there is a change of conductor size. The accom panying illustrations list the successive operations. TERMINAL CONNECTOR The universal rod connector attaches to the power source. GROUND STRAP Provides a convenient point to connet a ground wire to the molded conductive shield and places the molded shield at ground potential. 6. It will accom modate aluminum conductors in the range of No. Descriptive details are supplied by cable and accessory manufacturers with dimensions for various sizes and voltages.. 6 to 410 AWG with an insulation thickness of 0. No special tools or potting compounds are required for the assembly of this type of fitting.7 em). The cross-section of a molded terminal connector is shown in Fig. The precautionary recommendations mentioned in relation to cable splicing also apply to terminating procedure. except that the termination process requires the inclusion of a stress-relief cone or a pothead. 2. 11-29. MOLDED RUBBER CAP Presses over top of tenninator with an inter ference fit to provide complete wsterseal in~ tegrity. A patented Elastimold feature.495 to 1. and as an auxiliary to a common-neutral.installation practices Installing Aerial Insulated Cables Single insulated or covered overhead primary aluminum conductors suspended from insulators sometimes are used in tree areas or similar locations. except that for single-phase pri mary circuits (No. 125. These messenger sizes conform to the ICBA recommendation that the initial sag be such that the final sag be not less than 1. 2 A WG or smaller) where the mes senger also serves as a neutral conductor. adjustment must be made for reduction of strength. however. Their installation is simi lar to that of bare conductors. For the installer of the cable the most useful tabular values are those for initial sag and tension. in most instances the spans are of moderate length so suitable sag-tension values may be obtained directly or interpolated from manu faeturer-supplied tables that Jist initial and final values for 100. and its maximum tension will not exceed 50% of its rated strength at the fully loaded condition. 1350 aluminum. as described 10 Chapter 7. Stringing sag and tension charts are supplied by cable manufacturers as an aid to circuit design for light. The combination of strength and moderate electrical resistance requirements of such non-neutral mes sengers has led to wide acceptance of composites of aluminum and of steel (Alumoweld) for the make-up of the messenger. see Table 5-1) for use as described in Chapter 5. as a part of the grounding circuit for the insulation shielding. and high-strength alloy aluminum are often used for primary aerial messengers. Primary Aerial Cables The messenger size for primary cables is determined by the required strength. as well as combinations of 6201 aluminum with steel reinforcement (AACSR). The messengers for preassembled primary cables are not neutral conduc tors. and 150 ft spans. but a correction factor is applied if the installation temperature differs from 60'F. 4-12 (6201-T81) and 4-14 (ACSR). the conductance of the messenger must equal that of the insulated con ductor. sag-tension charts can be com puted or are available from conductor suppliers. the triplex form (two insulated conductors preassembled with a bare neu tral) supplies the usual single-phase three-wire circuits. Physical details of the cables used for the messengers listed in Tables 11-10 and II-II can be found in Tables 4-5 (1350-Hl9). Bare messengers not used as neutral conductors are often used also as a part of relaying circuits. The final sag and tension values for the various NESC loading districts then will meet requirements as to the percent that messenger tension bears to its ultimate breaking strength. Initial sag-and-tension data for preassembled triplex aluminum cables with full. How ever. Chap ter 10 describes various types ofcables. other messengers are similarly used of high strength ACSR. most overhead spans of insulated power conductors are in the form of preas sembled or field-assembled multi-conductor cables sus pended from a bare messenger. some of which also apply to preassembled secondary and service-drop cables. Insulator support is not required and space is saved by using a single-multi-con ductor cable. data regarding bare neutral messengers for such cables. For economic reasons. but high conductance is useful for grounding or signal purposes. Messenger supported cables are in two groups: Preassembled aerial cables (to 35 kV) Aerial cable assemblies (0 to 600 volts). and the manufac turer's table will confirm this if required. The span lengths usually are moderate so that sag and tension values generally are obtained from tables. medium. 11-31 depicts installation details for usual conditions of installation of the secondary cable and the service-drop taps extending from it. Messenger sizes are such that the normal initial sagging tension at 60'F will not exceed 30% of its rated strength. either with conduc tivity equal to that ofa phase conductor or as a "reduced" neutral having conductivity not less than one-half that of a phase conductor.and reduced-size neu trals are in Table 11-11 for the various NESC loadings for 125 ft spans. usually for 60°F. or heavy loading conditions (NESC. Although this table shows use of a combination messenger made of 1350 aluminum strands assembled with strands of aluminum-clad steel. Neutral-Supported Secondary and Service-Drop Cables Preassembled aluminum insulated multi-conductor cables supported by bare neutral messenger conductors have practically become standard for secondary aerial cir cuits and service drops. hence the equivalent conductor rating is usually listed for the messenger. However. for unusual spans. Table 11-10 is extracted from more complete tables in order to show the form in which such tables are supplied. For this reason various combina tions of steel. Fig. depending on service requirements. For these reasons specifications for multi-conductor primary cables with bare messengers usually specify the ohmic resistance of the messenger. For aluminum 1350 conductors or less than hard tempers. The neutral messengers of such cables are selected on basis of strength and conductivity. Subject to the NEC limitation of 300 volts to ground for bare neutrals. The conductors may be spiraled around the messenger or arranged paraliel to it. Fig. 11-30 depicts several kinds of fittings and acces sories used when installing messengers and preassembled aerial cables. Tables in Chapter 4 show. as described in Chapter 5. 11-23 . as mentioned above.667% of the span length. Similar quadruplex cables (three insulated conductors) if conneeted to a three-phase Y source supplies low-voltage three-phase loads. However. When fully loaded according to NESC values the sag and tension both will increase.covered and insulated aluminum wire and cable The notation on Table 1I-1I with regard to initial sag values for other spans than 125 ft is based on Eq.-1955 Ib (see Chapter 5). for 2/0-2/0 cable with aluminum-alloy 6201 me. which is the subject considered in this chapter. . and guy wires on poles. the initial stringing sag-tension of 13 in.imilar to Table H-ll for initial stringing conditions are us~d as a basis for installation. messengers. and as temperature drops to OCF under Heavy-Loading conditions the sag decreases and tension increase~. The sag eventually will in crease to the final value and the tension correspondingly will decrease as a result of long-time creep. and also verify that there is the specified margin between actual tension and the rated breaking strength of the messenger. 11-30. tables . Typical details for supporting and dead-ending cables.:nger. 5-2. The sag-tension values under conditions of maximum NESC loading are useful for circuit design because they indicate minimum clearances under the cable. The sag-tension values of Table 11-11 are for initial un loaded conditions at 60'F. hence it is available to obtain correct values from the cable manufacturer. 11-24 . 865 Ib becomes 24 in. Thus. o B c 3 Bolt Guy Clamp :3 Bolt GUY Clamp F 2 Bott Uni"€rsal GUY CHp Oval Eye Bolt E Split Bolt Connector Vise Type Connectors: 2 Bolt Universal GUY Clip Strand Connector Fig. but it is only approximate. shuwing also application of service drop span clamp. A. Typical installation details for secondary triplex cables. E-Dead-end support at pole for directional change of mOre than 45°. 'vv" Insulated Clev!s ToPIt o A Prelcftl'lel! De<ld"Eno tor EQuol) . C--Service-drop "T" tap near pole. neutral-messenger-supported.g) Plastic Guard ! Messenger Plastic Suspension Guard /Clomp C(lmp(e$$:iO_~'. even though not so shuwn."ger Suspe"sion CI. Notes: Compression connections are to be taped.A ! : ""V.installation praclices ~ .mp B Tope or Clip Connector (Before T. See Chapter 5 for additional details of armor rods and the like.rmor rods are used where abraSion is likely. 11-31.h~~'" Connettor_ I I I . B-Double service-drop taps at service-drop span clamp. Pref.pi.1 I! !I Mess. and messenger suspension clamp at pole.armed Oeoo~End (or EquOI ) c Fig. D-Clevis support at pole for directional change of less than 45°. Poles are to be suitably guyed to resist unbalanced forces. showing service-drop taps and other details. A-Dead-end at pole. 11-25 . XLPE insulation.827 1.504 3. cross-linked polyethylene insulation) UbI 6 1 2/0 4/0 350 500 750 1000 #3-3/4 7700 " " #3·2/5 #2·215 # 1/0-2/5 11300 13500 19500 .006 2." 4. Weight 100 125 : 150 100 125 150 Strength in.667 percent of span length.covered and insulated aluminum wire and cable TABLE 11-10 Representative Values extracted from Tables Supplied by Cable Manufacturer for Initial Sag-and-Tension Values at 60'F. Initial sag is such that final sag approximately conforms to ICEA recommendation of 1.618 1. extruded semi·con PE.390 " 23 27 28 " 27 28 31 1122 1306 1801 2500 3005 4032 5031 11418 1645 2269 1739 2024 2679 3720 3151 3787 4659 5040.379 19 2. Includes weight of messenger and binder tape.007 2.374 2. semi-con tape. 22 AWG copper concentric.575 5. Initial tension lS such that the final temiion will not exceed 25 percent of rated strength at 60°F for I light or Heavy NESC loading districts.158 3.215 " 3. 6048 J64()()~ 1. 5000 Volt Unshielded (Class B concentric stranded aluminum. 11-26 .421 0.251: 1.693 3.645 0.100 1. Ibltt! Sa!tinches (3) (11 Tension·lb I Size I i I .075 3.175 in. suitable for Light or Heavy NESC District> For Preassembled Primary AerialS·I/C Cables with AWAC Messenger Conductor Size AWG or Kcmi! I ! I I Cal>l. Mylar tape.789 3.606 3. PVC jacket) 2 110 4/0 350 500 750 1000 #3-3/4 7700 " #3·2/5 #1/0-215 11300 19500 " 556.()(J(} Volt Shielded. 1.600 2.039 " 5_079 6.575 1.50()j30!7) 26900 2. Span Length in Feet Messenger : Assembly (2) Rated Diam. strand shield.215 3.770 2. 3.053 ! 19 I" 23 28 " " 19 23 " " " " 27 337 516 662 428 655 840 880 1118 1280 1626 2193 1726 3126 2461 3242 I 4119 i 509 780 1000 1364 1983 2675 3813 5024 15.696 . No.695 0. Grounded Neutral (Class B concentric stranded aluminum. 2.076 4.459' 1. 0. instollation practices TABLE 11-11 Typical Initial Stringing Sag and Tension Values for Three-Conductor Sell-Supported Polyethylene Service-Drop and Secondary Cable (Triplexl.. These jnitial sag-tension values are based on NESC loading limits for REA systems.45 for 150-ft span.. are obtainable from cable manufacturer. final stringing tension is not to exceed 25%1 Of rated strength: and initial stringing tension is not to exceed 33~1!3% Of rated strength. I Neutral I Messenger I Conductor Size AWG Size AWG (or EquivJ NESC Light-Loading Oistrict Rated Strellgth Ib r Initial Sag N:i:SC Medium-Loading District Initial Sag Inital Tension Initial Tension NESC Heavy-loading District Initial Sag Initial Tension 410 680 1060 1255 16 12 1I 13 250 553 875 865 305 415 575 865 1070 29 11 1I 12 13 98 375 600 840 975 350 435 600 730 34 105 330 655 755 ALUMINUM ALLOY 6201 NEUTRAL MESSENGER 4 2 1/0 2/0 4 2 I/O 2/0 1760 2800 4460 5390 8 8 8 8 467 750 1195 1415 10 10 8 10 ACSR NEUTRAL MESSENGER 6 4 2 6 4 2 1/0 I/O 2/0 2/0 1190 1860 2850 4380 5310 10 10 10 10 10 290 445 660 1005 1255 10 8 11 12 12 REDUCED ACSR NEUTRAL MESSENGER 4 2 110 2/0 6 4 2 1190 1860 2850 3550 I 12 13 13 13 295 445 670 835 I 12 13 14 16 17 13 14 ALUMINUM NEUTRAL MESSENGER (Aluminum 1350) 6 4 2 1/0 6 4 2 110 560 881 1350 1990 26 19 17 19 91 195 385 485 54 19 19 23 44 104 195 72 295 49 410 40 23 53 115 230 . retaining the initial tension values for 125 ft span. that is.64 for l00. loaded tension is not to exceed 500/0 of messenger rated strength. multiply the initial sag values for 125 ft span by 0.ft span and by 1. for spans of 100 ft and 150 ft. lor 125 ft span at 60°F lor Various NESC Loading Districts (see Table 5-1'* Note: For roughly approximate value.. These approximations are less accurate for the Heavy Loading District. 11-27 . More accu rate values for spans other than for 125 ft.. . ulation. Shorl-Circuit loading Short circuits.s in Chapter 9 (see Fi~s_ 9-5. Emergency Overloads The conditions that permit the cable to be subjected to temporary emergency overloads. It is important to consider the worst case "limiting factor" when deciding the load carrying capability of a circuit. 220. A discussion of short-circuit currents in aluminum con ductors insulated with various materials . Fig. kW and kVA factors in the usual power circuit are well understood by designers and operating employees but. I' . except for differences of electrical properties of the conductors. either between the conductors of a power cable or from the conductors to ground or occurring in some part of the load being served by the cable. The problem of system fault-current is beyond the scope of this publication.. he is supplied with the ammeter readings that correspond to the emergency-load temperatures.. etc. Instead. It lists equations for two-phase systems that are frequently encountered. whereas bare conductors fail because of loss of strength of the conductor caused by high-temperature annealing.1. can cause a rapid rise of current values. Additional information apply ing to bare conductors is in Chapter 6. ampere.. 12-1 . as a reminder. de pcnJing on the kind of msulation. = 233 9A~1 :90 ~400.50. applying to elementary circuits and to average earth resistance.. does not measure insulation temperature to indicate that the emergency-overload limit has been reached.50 228. and relays. Circuit fuses." For the probable approximate ampacity loading of branch and main circuits for residential and light industrial uses. 15 kV From Table 9A~2. as required.0 =272 amp " 75 . A load factor of 100 percent is used for circuits in air or conduit in air. however. Reference data in previous chapters (mostly Chapter 9) cnable the desIgner and user to predict voltage drop as a function of load and to specify the maximum current to be carried per conductor (at 100% or reduced load factors) on a thermal limitation basis.Section III Covered and Insulated Aluminum Wire and Cable Chapter 12 Operation and Operating Problems Operation of power cables under their normal conditions of intended use seldom presents major problems. refer to NEC Articles Nos. operating temperature 751>C. as much as 100 limes normal or more. Precomputing of these ampacity values for the emergency-overload temperature is an operating problem solved by applying the constants from the leEA-IEEE Ampacity Tables. 200°C. and signal circuits en able the load dispatcher to maintain the load within op erating: limits or control its extension into the emergency load range. The allowable temperatures under short-circuit conditions for insulated aluminum conductors are 150°C. The basic relationship of kV. The reference to zero-sequence im pedance of bare aluminum conductors in Chapter 3.. What is the corresponding emergency-load ampacity if the emergency-!oad temperature of the insUlation is 90"C? Applying Eq. The load factors and corresponding loss factors that apply to typical daily load curves are explained in Chapter 9. and properties of the ins. The load despatcher. These factors are related to the heat-sink effect of the surrounding earth on conductors that are directly buried or are in underground ducts. and 250'C. and the emergency-load temperatures that the insulation can sus tain are listed in Table 9-7. circuit breakers. were outlined in Chapter 9. 9A-1. rated ampadty is 233 amp and Delta TD is 0. X ApPI!ntlix 9A describes further adjustments of the above rew lations-hip (or variations of ambient temperature. limiters. 230 and 430.50 228. The designation "star" is used instead of the term "Y-connected.40 . as listed in Table 9-7. The essential difference is that insulated conductors fail under short-circuit condi tions because of loss of insulation value. and much of it is applicablc to insulated conductors. may aid such calculations. but for network analysis and where terminal impedances must be con sidered.0. within recognized limits of good practice. 12-1 is included. are usually selected or adjusted to limIt the current in the cable to its design short-circuit capability.0 The Delta Tn value is unchanged because it is assumed that the dielectric constant and insulation pf are the same at both temperatures. -6. described in Appendix 9A. 90.1 + 75.~. cut-outs. prinCipally Eq. Example: 410 triplexed concentric standard rubber insulated cable in air: 40"'C ambient. the method of computation is the same for alu minum as for copper. and -7). regulators. uctor ""1. Volts pI . KiI~1. Some of the operating conditions that bring about short circuits of various kinds are considered herein as a guide to what is to be avoided.. Line--tQ<Line VOltage...I Hp .. fQUf'"-Wire* I T.covered and insulated aluminum wire and cable Two-phase.73XeffXpf 746 746 tt!f"~wi(i$. (see Tables 12-4 and 12-5) copper is by far the most commonly used.... 1000 IXEX 1.--. Three-wire Si ng le-phose¥Three.. . Power FactO!'. Star = I Line current Voltage.ER:.41X ~~t in either of the othet two. KILOWATTS AND KILOVO=:::. that is. ~imat$ eft Stngle-Phase ! 746H.... 12·2 The increasing use of solid dielectric power cable on electric utility distribution systems with higher available fault currents underlines the importance of proper shield size for the expected fault duty. Cable shielded with these helically applied copper tapes or concentric servings of fine (20-24 AWG) copper wires have generally perfdrmed satisfactorily in the past because of relatively low fault currents and because these circuits were often installed in ducts in three-conductor groups with a bare ground conductor. Amper(!$ e .LT-.85.When=-""'"·-----'-- To find Value 1ju> Below Is Known Vatue Am"". an efficiency of 85% is used in the formula as 0.Three -wire..73 circuits. tnt amper1lS in common coru. Two-wire Two-phose. decimals I Two·Phase. Four-wire fir r rrr E=ffi cS[]hl ~ ~ tE0f 6& g~j I. if possible. 2 Three-phoserThree-wire. HO/1oePower 746Hp I i 2XEXeffXpf lOOOkW =-- 2XEXpf I ! I 1000 kVA kW = I I i " I = I 1000 kVA = 1.Star Three.:E:cS~_ _ _ _ _ _ __ --. OutpUt. . . Amperes IkVAI III ..-AM=P:::. Note: The expression "decimals" refers to notation as a decimal fraction. line to line E = 1n= l. 12-1. j Direct Current SYSTEM I lXE kW= 1000 I kW =IXEXpf lOCO I kVA=~ ! i 1000 IX EXe!f i EXeffXpf 1000 kVA Hp=-- 746 Hp IXEXeffXpf 746 kW " Input. I Kilovolt Am"".. Delta Three-phcse~ Four-wire. Fig..---.wire Single-phose. FORMULAS I ! /46Hp EXeff 1000 kW 1=-- E I ~--- I loookW ---EXpf I " -E. Diagrams and formulas showing relationships between electrical and power quantities in various types of circuits. (11 Horsepower (Hpl Amperes Kilowatts (kWI III Kilowatts Input (kWI Kilovolt- Amperes IkVAI Horsepower Output (Hpl LIM OJ.73Xpf (kWI 1000 1000 IXEX2 kVA---· 1000 kVA· ____ L _ _ _ _ _ _ _ _ _ lXEX2XeffXpf Hp "" ·For two-pha"_ Hp . ba!a<'IC~d IXEX1.73XeXeffXpf 1000 kW 1. Short Circuits in Shields and Sheaths Consideration should be given to the performance of the cable metallic shield under the influence of a line-to ground fault.. HORSEPOWER... Though several other metals are sometimes employed as sheath/shielf material..J I2 I3 Neutral current All of the above based on balanced circuit E CURRENT.yen.. Input. Kilowetbl tVA".phase. '" Efficiencv..73E : 2E I IXEX2Xpf 746 Hp I 1..73XEXpf 1XEX1.. the shield normal operating temperature and the maximum allowable transient temperature of the shield. shield or sheath. mils. Tubular sheath 1. Tape overlap. w = Width of tape. Frorn Table 12-2: Tl = 850 C Step 2 Determine the maxirnum allowable shield transient ternperature for the cable materials in contact with the shield. which in this case is therrnoplastic. "'From leEA publication P-4S-482 t 2nd Edition. Table 12-1 shows the corresponding forrnulae for cal culating the effective cross-sectional area of various types of sheaths/shields. Thickness of tape. Table 12-2 shows the approxirnate shield normal operating temperature for various steady-state conductor operating temperatures for cables rated 5 kV through 69kV. Approximate Shield or Sheath Operating Temperature. 5 15 25 35 46 69 90 90 90 85 85 60 85 85 85 60 80 75 75 75 70 70 65 80 80 80 75 75 70 70 70 70 65 65 60 65 60 65 60 65 60 60 55 55 50 60 55 • NOTE: The maxImum conductor temperature should not exceed the normal temperature rating of the insulation used. mils. Under these conditions. As shown by the tables. Voltage.operation and operating problems Equation 12-1* gives the mInImum effective cross sectional area of metallic shield required for a given fault time period. From Table 12-4: M = 0. L = Overlap ot tape. TABLE 12-2 Values of T1. Helically applied flat tape. n = Number of serving or braid wires or tapes.27 [. Wires applied either helically. or longitudinally with corrugations 2. NOTE 3: The effective area of thin. Helically applied tape. mils. The user is cautioned to read this publication in order to fully uuderstand the derivation and basiS for this calculatiou and the associated parameters.063 12-3 . mils. helically applied overlapped tapes depends also upon the degree of electrical contact resistance of the overlaps. the "M" values are constants and depend upon the shield rnaterial.(dis+50)+8] b NOTE A = e = b = dis = dm = ds = 1: Meaning of Symbols Effective cross-secHona! area. as a braid or serving. percent. Diameter ovet semiconducting [nsulation shIeld. Corrugated tape. at Various Conductor Temperatures Rated Shield or Sheath Temp. NOTE 2: The effective area of composite shields is the sum of the effective areas of the components. oC.27 nwb 4bdm I . From Table 12-3: Step 3 Determine the "M" value for a copper shield with TI equal to 85 0 C and T2 equal to 2()()OC. the contact resistance may approach infinity where Formula 2 could apply. mils (usually 375). not overlapped 3. Formula 3 may be used to calculate the effective cross-sectional area of the shield for new cable. Step I Determine the approximate shield operating tempera ture for 900 C conductor temperature (which is the maximurn temperature for normal operation of XLP insulated cables). TABLE 12-1 Formula for Calculating of Shield T or Sheath 1. Table 12-3 shows the maxirnum allowable transient ternperature for shields in contact with various materials. longitudinally applied 5. For example: the effective area of a composite shield consisting of a helically applied tape and a wire seI'Ving would be the sum of the areas calculated from Formula 2 (or 3) and Formula 1. 1919. 1 and 2' 1.j 100 see 2<100. Tables 12-4 and 12-5 give the <OM" values for use in Equation 12-1. kV 950C 900 C 850 C 800C 750C 700C 65 oC. overlapped A (See note.L) note 3 4. An increase In contact resistance may occur after cable in· stallation during service exposed to moisture and heat.. mils. Diameter of wires. 0C at Conductor Temp. Example calculation: Determine the size copper wire shield required to carry a fault current of 10000 amperes for 10 cycles for a 15 kV XLP cable having a semi conducting thermoplastic insulation shield and a thermo plastic overall jacket. Mean diameter of shield or sheath. contaminants _ _ _ _ _ _ _T~ABLE 12-3=--_ _ _~ Values of T2* Maximum Allowable Shield or Sheath Transient Temperature.03310.0511 0. amperes t = time of short-circuit.06010. a cable having a crosslinked semi-conducting shield under the metallic shield and a crosslinked jacket over the metallic shield would have a maximum allowable shield temgerature of 350oC.032 0.07110. 0.. 12-1) Causes of IlISulation Failure The majority of cable failures occur unexpectedly. The reasons for insulation failures which are not obviously'the result of physical damage may be found during laboratory investigation by electrically testing cable samples to destruction.p.::ath:::.::e':..021.7 .48 : r-- .043 0.09] i St.0528 I . They are often found as voids.027 10. 3500 Thermoplastic Impregna ted Paper 2000 2000 Varnished Cloth 2000 NOTE: ------------------~--- The temperature of the shield Or sheath shall be limited by the material in contact with it. Most often. it would be 200 C. The number required for any specific wire size is simply the total cross-section calculated in step 4 divided by the individual wire circular mil area and rounded up to the nearest whole number: Number of 14 AWG wires 64866 -.070.065 0.' the Limiting Condition Where T 2 = 200 0 C i.:ie.Q13: 0.nze 0.02Oj0.069 0.8 or 16 Similarly..03410.057 0.024 0.ll46 0.1""rO. °C Alu· minum Steel StepS Determine the number and size of the wires necessary to equal or exceed 64866 circular mils.065 0. A brief review of the most frequent causes found by this method is found in the following para graphs.092 0.01410.019 -~--~. Inspection of Table 12-1 shows that the effective cross-sectional area of a wire shield is equal to nds2 or the number of wires multiplied by the circular mil area of each wire.::l. I10. 0.044 0.0.03310.:1T:.012 10.1· 0.071 0.050 0.0.ot21 0. With a thermoplastic jacket.035: 0.026! 0.049 1 Com mercial 0.034 ' : 1. Step 4 Calculate the required shield cross-section for a fault duration of 10 cycles (0.06810.0460. Copper Load .027.063 = 64866 cIrcular mils TABLE 12-4 Values of M '". Zinc 1 1 0..03210.044 0.046: 0.031' 1 .Terdal L~~n~ where: I = short-circuit current in shield. .048: 0. the number of any other wire size may be determined: i.094 0.0. ./S::h.028 .093 0.:::.036J .03sl 0.089.091.047 0.03310.:.1.Q36.049 0.070 0.048 0. 12·4 85 'i 80 90 15 r--- 10 65 60 sol 55 0..:e.§!:9.::O".05110.03410. the power dissipated in the failed area burns the insulation to the extent that the cause is destroyed.Ot410..046! 0. Imperfections in extruded insulations are a major cause of failure.096' 0.063 0.021 0.046 0.0.. 65 I 60 55 50 I I .0.OSS 0.063.01210. 4110 = 15.167) seconds...0..018! 0. II' J' .031rI•0.070 0.pe::. Zinc Cupro- Nickel ....044 0.062 10.-:S::h:.012 O.m". 0.06610. seconds M = constant.047 0.08810.' " 1 " :o.__ ~~~ Copper 10.I0.073 0.tu=te:. ac Cable Material in Contact with Shield or Sheath Crosslinked (thermoset.-"" TABLE 12-5 Value. -+__-+_-+__-+__ ~. ~.'.ra::.068 0.:ati:.. of M for the Limiting Condition r-__~-.045 0.035: 1 J 10.0190. '~~J Shield/Sheath Operating Temperatu..012 .030. Shield! Sheath Material I A = pIT ~ (Eq.0241 0.014 .C'--j Material 90 85 80 i 75 ' 10 .I ' O... .047i 0. . Applying Equation 12-1: 10000 VOJ]. I J !.I •AluO.074.0251 0.041 0.e::. see Tables 12-4 and 12-5 .06310.02~021 : 0. For example.e ITll.covered and insulated aluminum wire and cable Examination of the areas near the fault and the external appearance of the cable'may also provide evidence which helps determine the apparent cause of failure.09010.0261 0.06010. -For lead sheaths this temperatur-e IS limited to 200°C.068 0.035.059 0.w'-Chere = 3500_C~_ _~--i T2 Shieldl Sheath f.0461 0.03410.on: 0.064.. .042 0.022' : --r-E i : 0.047 0.Q13: 0. A= 0.1". O . 0. . ..045 0.::d:.062! 0.:·:::n"g_T. Such trees can be seen by optical examination when suitably stained and magnified. Humidity. in adequate short-circuit protection and contact with harmful chemicals. as follows: 12·5 . It may occur at cable terminations where the insulation is exposed. Serious discharge can also develop on non-shielded cable. However. comparison from one year to previous years will indicate any deterioration. For these conditions. In each of these instances. a short time test can only detect gross defects or damage. sharp rock may pierce the insulation. If cables without a moisture-proof barrier are operated in a wet environment. High voltage cable is usually carefully installed and protected. Occasionally. the current will erode and char the insulation.operation ond operating problems or sharp projections into the insulation at the conductor shield or insulation shield interface. The presence of some voids is inevitable due to the chemical reaction and medium used to vulcanize insulation. only requiring the cable to withstand the voltage for a period of minutes. "Dig-ins" do occur. however. Thus. the core can contract away from the sheath leaving voided areas. little attention is paid to the quality of the fill used to cover the cable. Often. placed in service. specialized crews. Cable manufacturers have introduced compounds which retard tree growth and much research is taking place to develop improved tree-resistant insulating materials." Treeing of two types is known to occur in solid dielectric cables water or electrochemical and electrical. The wax may fill the voids and retard further ionization. FaIlH Location The necessity of developing good cable-fault locating techniques is· probably more important today than ever before. Digging into the cable occurs quite frequently. Other trouble may occur from poor connections. Ionization of the voids can polymerize the oil. When tamped. Unfortunately. water trees will likely form at high stress points in the insulation since moisture can easily penetrate the insulation. dif ferences in voltage gradient on the insulation surface produces current flow. they may also be introduced through inadequate quality control procedures and poor handling techniques at the cable manufacturing plant. Table 12-6 lists the present industry-recommended voltages after installation and for subsequent maintenance evaluation. Also. multiple cables may be laid across each other or in such close contact that poor heat dissipation results in insulation embrittlement. water may enter the conductor from inadequate or non-existent sealing.. The growing direct-buried residential distribution system has dramatized the need for reliable techniques to pinpoint cable faults as quickly as possible to minimize downtime and unnecessary excavating. much has been learned about deteriora tion of insulation known as "treeing. The major cause of failure in paper insulated cable is sheath deterioration or rupture. Voids occur in such cable due to expansion of the cable core under electrical load. The following material outlines in general the types of equipment commercially available for the many different kinds of fault conditions. Often. The test is quick and simple. mechanical damage is less prevalent. Surface discharge or tracking will deteriorate cable insulation. Cables that are plowed in are susceptable to damage unless care is taken to feed them into the equipment smoothly. External Causes of Cable Failure Failures of 600 volt cable are most often caused by mechanical damage. cleanliness and the leakage distance all permit wide variations which may be mistaken for insulation deterioration. without jerking. Installation and Maintenance Proof-Testing Proof-testing is an accepted procedure by which higher than normal operating voltage is applied to cable. forming wax. the readings can vary greatly since leakage is readily influenced by the condition of the terminations. Sharp projections into the insulation may be formed as a cable is extruded. The failure mechanism is not completely understood. However. leaving tracks. Normally. some inevitably passes through into the cable insulation. no one piece of apparatus is sufficient in itself. In this way. they are divided into two general categories. rodents attack buried high voltage cable. particularly in aluminum cable. special metal protected cables are often used. leakage current is r~ad and recorded . In some areas of the counlry. Contaminants are found in the raw materials purchased from reputable compound suppliers. In recent years. Screens are used in the insulation extruders to help filter out solid contamination. It is believed that these trees will ultimately lead to cable failure. However. trained in the methods for locating faults. However. Treeing sites are usually at high stress points at the insulation/shielding interface or at voids or contaminants which cause discontinuities in the insulation. This permits water or other harmful liquids to penetrate the laminates! insula tion. To a lesser extent. Most often this is done On high yoltage cable after installation and before the cable is. d-c voltage is applied because such equipment can be made lightweight and portable. Leakage current is of value if a record is maintained over a long period of time. The cables are often directly buried at a shallow depth. Conductor cor rosion can result. Over long periods of time. These create points of high electrical stress which can lead to premature cable failure. Upon cooling. Many power utilities are now staffed with well equipped. The signal is traced to tbe fault by patrol ling the cable with some form of detector used as a signal sensor. therefore. RadiIr Radar transmits a series of bigh frequency pulses along the cable and observes the reflections from changes or discontinuities. tbe reiative magnitude of resistance determines the type of equipment to be used to acbieve good results.5 46 69 During After Installation Maintenance (15 minute ~uratiofl' . the fault resistance should be less tban 2000 ohms. motors. Pulse and tone generators witb companion detectors (Acoustic. 12·6 In many cases. Locations better than I percent of tbe range are possible for circuits up to 80. Ground connections may be left intact. For all of the locating tecbniques discussed bere. it would be advi$able to contact the equJpment manu facturer before testing. Tracer Equipment . locate power cable breakdowns. it takes an electronic picture of tbe cable under test and displays it on an oscilloscope. In essence. The voltages in the table are 80 percent and percent respectively. The tracer methods apply an input signal to either end of the faulted cable. The faulted conductor is normally joined to a similar unfaulted conductor and the bridge measurement made On the resulting loop at tbe opposite open end. conductor to-sheath or conductor-to-ground) or a series or open fault (open circuit or excess resistance in series).Conductor-to-conductor (grounded) Conductor-to-sheatb Conductor-to-ground Series Fault Open circuit (open) Open sbeath Fault Resistance The types of equipment described below are among those commercially available which can. no limitation is placed on open drcuits. limitations of such equipment may require the use of lower values. are connected to the cable circuit voltage. The fault resistance can be measured with an ohm meter or megohmeter and tben classified as a parallel or grounded fault (conductor-to-conductor. 25 35 40 20 25 30 55 40 60 65 75 80 85 100 120 170 90 125 NOTE' When equipment such as cable terminals. several important factors are determined: Parallel Fault . The longer the length. Higher sensitivity is possible in a high voltage adaptation of the bridge where fault resistance can be as high as 5 megohms. High resistance sometimes requires reduction of the fault resistance by "burning.is employed wbere some form of electrical signal is injected into tbe cable at one of its terminations.0 8. TABLE 12-6 de Proof Test Voltage (kV) System Lo~tage 2. In such instances. Having meggered the affected circuit. It is recommended the rate of increase of the voltage to the desired value be done uniformly. additional equipment is usually required to pinpoint the exact fault location.. transformers. For parallel faults.is employed wbere tbe entire test and determination of tbe fault location is made at one or more terminals of tbe cable. converted to feet and shown on a digital display. . Electromagnetic. eo Identify and Isolate The faulted section in any branch circuit should be clearly identified. if desired. of the factory dc test voltages applied to the cable prior to shipment. Bridge and Capacitance Instruments are classified as terminal instruments since they provide an approximate location as a percentage of circuit length. The voltage level should be reached within 60 seconds but not sooner than 10 seconds. Bridge Tbe Murray-Loop Bridge with numerous variations has been used for many years to calculate parallel fault locations. the greater the actual error.000 feet. fault resistance and equipment available. The signal is then physically traced along the cable route until a change is detected which will reveal the location of the fault. Tbe Cable Radar Test. loose connections or series type faults. etc. The time required for the generated pulse to reach a dis continuity and return is measured. individually or in combination.5 5. de-energized and isolated. The fault resistance should be relatively low. it is necessary to dis connect and free all terminals.7 15 25 28 34. However." Location The method of locating a fault is influenced by such variables as type of cable. Eartb Gradient) are known as tracer metbods and tbese function without knowledge of the circuit length.covered and insulated aluminum wire and coble Terminal Equipment . there is a change of signal strength and if a d< impulse is used there will be a change in the signal direction. an acoustic pickup detector is applied along the surface to amplify a weak thump and thus locate the fault at the point of maximum intensity. On direct-buried non-shielded cable.operation and operotlng problems A low voltage version inverted Murray-Loop Bridge having electronic null indicator can provide good results with fault resistance as high as 200 megohms. open-circuit faults. the same pickup coil can be used for earth gradient fault location. Fault resistance may be reduced by burning the insulation at the fault with a repeated are. a low voltage audio frequency (e. Capacitance A capacitance bridge is useful on very high series resistance.can be very successfully located with any of the voltage gradient devices available. The impulse energy in the form of a traveling wave will either dissipate noiselessly at a low resistance fault or spark-over (break down) at a high resistance fault. can then be applied to pin point the exact fault location.:curacy with this method of detection is extremely high. A continuous d<. The a. interrupted d< Or audio tone is applied at one end of the faulted cable. Low voltage. Acoustic Detection The sharp report of the periodic discharging from a high-resistance fault reveals the location when exposed. shielded conductor faults in a trench lay system . The capacitance of con ductor-to-shield fault is measured from one end of the de-energized circuit. insulated neutral cable fault . Ac without resonance would lose considerable effect in capacitive charging current. or con tinuous ac or de current. either electromagnetic or acoustical. High voltage. Faults can be located quickly with excellent accuracy. Earth Gradient Detection This detector system is used to pinpoint high and low resistance faults on direct-buried non-shielded cable. This location can be verified by repeating the procedure from the remote end.g. the location can be detected by an electromagnetic or earth gradient device. thereby creating a voltage gradient. A selectively tuned pickup coil and amplifier is used to trace the signal which can indicate a nuU or peak over the cable route. however. Low voltage trench lay. similar to the impulse generator but is usuaily limited to 1000 volts. Burndown The level of fault resistance must sometimes be reduced to enable pinpoint location with some methods. The probes are applied as a pair 0' er the surface route in football chain fashion.Ienerator may be used to initiate the lowering of fault resistance. Audio Tone As a preliminary step of fault locating. non-shielded cable faults In a conduit can usually be located with a bridge. Accuracies within ± 3 percent are possible. For the high resistance discharge. However. The spark-over results in an explosive release of sound. However. high energy impulses generated from a capacitor bank are applied to one end of a faulted circuit. the impulse generator with detector is usually sufficient in most instances. 1000 Hz) is sometimes matched to one end of the cable in order to transmit a signal. Accuracies within 0. Electromagnetic Detection The field generated by any transmitted impulse aiong a cable is sensed by means of an electromagnetic pickup coil and detector. most repairs on this kind of system can be more economicalIy performed by replacing the faulted cable section. 12·7 .01 percent.should first be generally located with radar. RecommendatiOllS Generally most faults can be detected successfully by selecting a limited number of methods and equipmenL Recommendations: High voltage. light and current at the fault location. The electromagnetic surface coil can also be used to trace the cable route and a sheath pickup coil can be used to find faults on dueted cable. The electromagnetic and earth gradient devices may also be used for the high resistance discharge. Knowing the capacitance per unit length. impulse or a< resonant !. Some tracers aiso respond to energized 60 Hz current and incorporate filters for dual operations. Impulse Generator (Thumper) High Voltage. For the low resistance discharge. A compatible detector measures the gradient between two movpable earth probes. A high voltage d<. An impulse generator with the appropriate detector. Often. This is true for radar.should be located with a radar set and impulse generator as with trench lay systems. shielded. the location can be detected as an audible thump or an amplified thump "'1th the aid of the acoustical detector.conductor faults in a conduit system . the distance to the open circuit can be calculated. Murray-Loop Bridge and some signal generators.5 percent of the loop length are possible with resolution to 0. at the fault. non-shielded. On direct-buried cable this can be heard as a dull thump on the surface through several feet of earth. The current through the fault will travel back to the generator ground connection via the earth. . 17. occasionally combined with some cold work. After World War II. FIgures 13-1. an aluminum bus bar will weigh about half as much as copper for equal con ductance. 9. Other aluminum alloys may be used for bus conductors. 13-5 m and n). 13. In recent years its use is primarily for power rails for rapid transit systems and overhead electrical cranes. Aluminum 1350 is a commercial high-purity aluminum with 61 percent conductivity. a new conductor alloy. aluminum and iron. However. Minimum proper ties for various aluminum product forms. sizes and methods of manufacture are available in the Aluminum Assoeiation's Aluminum Standards and Data. The service record was ex cellent but costs prohibit peacetime use of silver for such applications. copper. and numbered references in the text relate to this bibliography. however. Many standard works on bus <. bus system designers have used the low cost of aluminum as the basis for optimum economic cur rent density. Copper has excellent mechanical and electrical characteristics and for many years was the metal of choice for use as bus conductor. The purpose of this chapter is to provide technical data on numerous bus conductor shapes and alloys as well as answers to basic questions on design and joining. 2. 18 and Tables 13-9. 6101. 12. -H112 for sawed rolled plate. was developed wbich had considerably higher yield strength and better creep resistance than 1350. They are intend ed for general information only and should not be specified as engineering requirements.7 from the Kaiser Aluminum Bus Conductor Technical ManUal.<>nductor are listed at the end of this chapter. 14. AlIOJS and Tempers Pure aluminum has a conductivity of about 65 percent of the International Annealed Copper Standard (lACS). Where high conductivity is reqnired. it was used as a bus conductor only during World War II when millions of pounds (mostly 14" x 9" bars) were used at various aluminum smelters.99 percent pure. this purity is costly to achieve and the mechanical proper ties are low.10. Although silver has the highest volume conductivity. listed in order of volume conductivity. Iron in various forms was also used in large volume for bus conductors during World War II. Aluminum has less than one-third the density of copper and.10. Today. The alloy contained magnesium and silicon for high mechanical strength without significant reduction in conductivity.Section IV Bus Conductors Chapter 13 Bus Conductor Design and Applications The selection of material for bus conductors is usually based on a balance of mechanical and electrical characteristics. and availability. 23 have been reprinted with permission from the Alcoa Aluminum Bus Conductor Handbook (1957) and other Alcoa Tecltnical Publications. The tensile strength of each 1350 temper is determined by the amount of work given the metal during fabrication. making allowance for conductivity. The materials that have been used for bus conductors in large quantity. Alloy 6063 has been widely used for outdoor high voltage substation buses because of its excellent mechanical and electrical properties and its availability and economy. they should be used with care since conductivity and mechanical properties can be greatly affected by small 13-1 . are: silver. Where high strength is desirable and conductivi ty requirements are lower. However. Typical physical properties given in figures and tables are not guaranteed and may not be exact. even for these applications its use is declining due to the advantages of aluminum and aluminum-steel combinations (Fig. economics. Figures 13-4. However. For large installations requiring millions of pounds of metal. alloy 6101 is used in a variety of shapes. The strength of this alloy (6101) is obtained by suitable heat treaunents. alloy 6061-T6 bus is used. 11. the trend has been toward wider use of aluminum for all types of bus installa tion. 16. Aluminum can be produced 99. and -F for cast bars. with a minimum sacrifice in mechanical properties. II.28 and Tables 13-3. most 1350 aluminum bus conductors are of -Hlli temper for extrusions. 0 25.001-3.' I I' I i .0 min 10.0 35. some employ a softer alloy having about 12. 1350-H III .0 10.0 min 22. (e) The lower elongation value~pplies to the thinnest sheet.0 18.0 6.0 9. Values apply to ASTM B 429 structural pipe and ASTM B 241 seamless pipe.5 and 4.0 4.2.0 8.0 12.125 1350-H18 ' Bolts Ib) 2024-T4 1/2-5/8-3/4 NC Cast Alloy 1350-F 1 in.0 15. (f) Several casting alloys are suitable for aluminum sand.0 B.l.bus conductors TABLE 13-1 Mechanical Properties of Aluminum Bus Conductor and Related Alloys (The Aluminum Association.0 14.!. B 241.6 ksi minimum ultimate and yield strengths. pipe i 1.0 8.000 and shapes 6101·T63 10. and up for Bus id) 1050 Cast Alloy I for Fittings if I . i 6101-T61 ~ 0.0 8.0 14.500.0 min 20·30 min i.0 min 8. Values apply to ANSI net stress are.0 8. or4 Dial r .or die-casting of connector fittings. or continuous run-out through an orifice.125-0.125·0.0 18. 13·2 .500 0. all Rolled bar 1350-H12 0.0 35.1.--"'-----'----- Elongation values apply to specimens of sizes related to product uses. where considerable water may be held in the fitting and freeze.0 20.0-T6 (an Aluminum Association registered number). and Manufacturer's Listings) l I Ten.5 i.000 .5 25. respectively. There is no registered Association number for this alloy.499 bar tube.0 IS.000 Rolled .0 Typical Yield 32.020-O. and B 429.0 11. ! I 22. 1350 .000 6101·T64 0.0 12.125·1. suitable both for bolted and welded connections.0 11.0 . 35.0 40.0 45.5 10.749 Extruded pipe 6061·T6 .0 IS.499 or sheet 1350-H 112 0. Pipe size 1.) 4-9 min 3.0 3.5 29.0 15.0 3.6min 2-4 min tel 24 min 40. (for shearing i 1350-H 12 !0.000 Sawed'plate bar .749 Extruded rod. ASTM B 236.5 37.0 16.heet .0 percent or better elongation.125-0.0 25.249 or forming) c!-350-H 14 • 1350-HI6!0. and 35.0 i Typical (a) Elongation (Percent in 2 in.. The designations 1350-F and 1050 are often used in the trade for designating cast bus bars made by run~out into sand molds.0 62. of reguiar or semi-finished bolts.ile Strength Alloy Product i and Temper! Thickness in Inches . but in the trade it is often referred to as A·l00. 12.0 15.0 10.0 31.000 6101·T65 0.500 6101·HIII i 0.0 35.0 Ie) i & over 6063-TS Pipe size.0 12.020-0.250-2.0 8.125-0.0 14.0 5. For special shapes and unusual conditions of installation.0 28.0 15.125·1.A35S.0 38.0 14.0 I Ultimate Minimum! Typical Ultimate 27.750-1.0 4.0 18. The most frequently used for n«mal conditions is A356.125-0. B 311.0 30.0 12.0 i 3.0 20.0 14.O I.0 11.5QO.0·TSI (a) (b) (e) (d) I (lui) at 20° C (68° F) Minimum Yield 8. 0.0 12. 6101·T6 All 0.0 min 16. 46 0.70 Modulus of Elasticity. per NEMA Standard.4-! .00393-0.5·60. cal/gmtC or BTU/lb/oF 0. Typical.220 for 6101 1c! Coefficient of thermal expansion (line./inl'C Volume electrical conductivity at I 59.42-14.29· ·14.39 I 15. the less favorable is designated "minimum" provided a higher value is favorable.9-6. in. Up to 2% higher in compression Note: If two values are shown.69-13.5-5. --- 1350 ~ I 6101'~~416101-T65 Any Temper 6101·T6 6101·T61 6101·T63 Thermal conductivity at 20°C 5. Aller Of and Temper Property .5 I 56. W • W S 3 t ~ <g' ! lf' .7-5. in.81· ·14.7-5.o.TABLE 13·2 Physical and Electrical Properties of Aluminum Wrought Bus Conductor Alloys (ASTM B 236. (dj The higher of a pair of coettlclents corresponds to the higher vafue of the pair of conductivity values. and The Aluminum Association) Applying to all alloys and tempers afwroughtalloys.00380 19.000023 Specific gravity . Ib/cu in. (roundedl 0. .9 5. (c) Increasing by 0.3·5.5 61-62 55·56 57-58 56·! 7 13.5· ·14.00373-0. Otherwise the term "guaranteed" is sometimes used.35·13.lft(bl Temperature coefficient of electrical resistance at 20·CrC id ) 0. the more favorable is I'typical".00377.rltC 0.55 14.8 6061-T6 6063-T6 Typical Typical 3.8 15.1 watts/sq.17 0.00363· 0.94 0.0. Ib) To obtain de resistance at 20"'C in microhms multiply table value by length in feet and divide by cross sectional area in sq.00403· -0.Q0383 -0.! .0 5.% lACS for current ratings.0 0284 10.00 70.018 for each 100"C above 70'C (specific heat).5·57. psi 10 x 10".2.6 5.00 377 13.5 I 42-43 I 53101 20°C percent lACS") 0 Electrical resistivity (del at 20·C (68°FI microhms/sq.04 14. 9 5. typical values Weight.00370 .00410 0.37 18.14 14. The conductivity of 6063·T6 alloy pipe for outdoor service may be taken as 55. B 317.00400__ 14.098 Specific heat.00350 o n0277 t~ (sl Typical conductivities of 6101 alloys from Standards of The Aluminum Association. in.4 5.214 at 70°C for 1350 and 0.o. 00223 .00357 .. Formula for Temperature Coefficient of Resistance: Example: the de resistance of an extruded channel section of aluminum alloy 6063-T6 is 8.00363 .00356 .00393 .r .00354 .00415' .00313 ..003011 . 55% conductivity is much used as design basis for 6063· T6 alloys for tubes.00363 ..00362 .00369 ..00370 ..64 microhms per foot Q Q 13-4 .00257 .00446 .00382 .00390 .- o 10 .00347 .00307 .-_ _ .00340 ..00328 .00350 .00334 70 80 90 100 . headed 55%.t .00385 .00332 .00358 .003181 .00381 .00387 .00305.002991 ..00427 .35 microhms per foot at 20'(.00344 . and interpolate from the listed values.00378 30 40 50 60 .00406 . resistance at 30'(..00327 ..00388 .00431 .. R30'C (8.00274: .00338 . .00401 . .:.3.00337 . [1 + 0.00367 .00438 .003291 ..00393 .00384 .00379 .00420 I .00312 .'+----i-.00344 . cal Representative Value Commercial j mum Copper Bus -t---t--L-J--+-r--~--r--\-~B_ar 1 1 Temp.00264 i .00318 . .f .:.00350 .00289 .003951 .00365 .00331.00290 I .00377 .00303 .00308 .00298i .00363 .00409 .00327 ..00373 .00307 .00377 .00342 .00285 ..00392 .00~1. (b) Per note on Table 1.t .00352 .00423 .00401 .00251 .00303 .35.00403 .003351 .00375 .00333 .00233 . .2.00281 .00345 .00338 .00316 ..--t--.00326 .00427 ..00371 ..002821.00363 .00340 .00317 .002281.00376 .00377 .0041 (j ..00289 .00349 ..00351 .00322 . .35 (1.00391 . and Conductivity % (lACS) fa) % lACS I 1 6061· 6063· T6 Typi· T6 Typi· cal cal I 40% 6101· T63 6101· T61 Mini~ Mini~ Mini~ 6101.00325.00309.00294 .bus conductors TABLE 13-3 Temperature Coefficients of Resistance (dc) for Bus-conductor Aluminum Alloys and Representative Value for Commercial Copper Bus Bar Aluminum Alloys and Tempers.00329 .00306.C.00370 .00245 .J.00302' .00364 .00261 i .00316 .00396 .00344 .00383 .00239 ..00271 . obtain conductivities from Table 13·2..00357 .00417 ..00413 .00312 :..00_2_94_ I fa) For alloys not shown.00298 . hence coefficients should be taken from the column.0035 {30-201! 8..00339 ...0029ili~~~ 1 ...00323 .003201 ..+ .00279 .00386 .00352' .00298 ...00400 .00407 .\ . Find the same channel'.00322 .00307 .00360 .035) = 8.003141 .00378 .00398 ..00317 .. 6101· T6 55% -I~ -!-I-!~!~ ~ ~ 20 25 . T61 Typi· mum mum cal mum 53% (b) 1 i i 6101· 1350 T64 Mini~ mum Mlni~ I 1350 Typ.00310: . . . effects of Heating The generally accepted maximum continuous operating temperature (see UL 857) for open electrical buses is 70°C (30° rise over 40°C ambient) to prevent heat flowing from bus to connected apparatus which is generally limited to 70°C at terminals. Fig.... Tensile strength _ ___ Yield strength A B C D 0. "'...... " '" H ...bus conductor design and applications ----~~----~~---... Temperatures of 90°C (50°C rise over 40°C ambient) are acceptable for switchgear assemblies and metal-enclosed bus. 85°C H 2OO'C 125. 13-2 for Aluminum 1350-HI2..... 13-1... .r:!':11~ C D .. Tensile and yield strength of 6101·T6 bus conductor at rOOm temperature after heating.. govern the selection.. .. It also lists their temperature coefficients of resistance for 20°C and Table 13·3 shows them for other temperatures in the range normally occurr ing in bus design. ...000 hours on the tensile and yield strength is shown in Fig.. short circuits or pr..... 13-3 depicts stress-strain curves for the listed alloys and tempers..!in.. For outdoor high voltage substation buses.. mechanical considerations rather than electrical. high electrical conductivity alloys are the best choice for heavy duty buses for the electrochemical industry where cost of power is an important consideration. it is desirable to have a generous spread between yield strength and tensile strength (see Bending and Forming. hased on minimum values from Table 13-1.{..000 . 13·1 for Alloy 6iOl-T6. 85'C F 15O'C 125'<: G 175'C 65'C...-• ..002 in. For example. Where bending and forming characteristics are important.. E .. The effect of heating up to 200°C for as long as 10. Stress-strain and Creep Factors Fig.. However. .....=-----~_1A 30. page 13-7).. Table 13·1 lists mechanical properties and Table 13-2. The designer is offered a broad range of properties from which to select the alloy and temper best suited for his particular application. strain line that is 13·5 . amounts of alloying elements.. Mechanical Properties The mechanical properties of the different aluminum alloys and tempers commonly used for bus conductors are shown in Table 13-1.. The intersection of the 0. The effects of these temperatures on the mechanical properties of aluminum bus conductors are negligible...olonged overloads may generate temperatures high enough to re· quire consideration of the effects of heating on the bus properties. the physical and electrical properties of the aluminum alloys commonly used for bus conductors......I ' . I 175°C E 150.000 B ...... J 200"C 1 G .. 65'C.1 F J 10 HEATING PERIOD (hour) Fig.. Legend 10.{. Table 13-2 gives the percent volume conductivity (lACS) and resistivity for the common bus bar alloys. ~ Ii>" w :. i ~ ~ - ~ ~ KL ~ 0' 0." 1 I" 10 IIJII 100 lit! 1. • 0..000 HEATING PERIOD.000 . TYPICAL TENSILE 1350-H12 .. III 10... i a ~ LEGEND ~ i'" Iii 65°C 8S"C 12S·C l5O"C 17S·C 2OO·C A B C D E F G H J K L & TENSILE Y I E L D . . Typical/ensile and yield strengths oj aillminllm 1350-H12 at room temperatures after heating. HOURS Fig.. 13-2.TYPICAL TENSILE AND TENSILE YIELD AT ROOM TEMPERATURE AFTER HEATING..1 ". Bending and Forming 30. The elastic limit (EL) of an alloy is represented as the stress value of the point of tengency of the curved part of the stress-strain line and the straight part of the line.000 13-7 . (2) the size and shape of the conductor.000 6. (Average stress required during a 10~year period to produce 1. according to ASTM designa tion. Table 13-4 lists to-year estimated creep factors for various bus conductor alloys. dlam. and (4) the bending equipment used. 2024-T4 bolts. Another factor that governs bending is the size and shape of the bus conductor. 13-3.500 5.000 606:!-f6 (6101-f61$ SIMilAR) 25. Elastic limit is estimated as point ot tangency (EL). especially if thermal cycling as the result of varia tions in electrical loading is involved. The ratio of yield strength to tensile strength must also be taken into ac count. elongation alone is not a complete criterion for ductility.000 1350-H13 103M) 1350-H12 !6101. For example.000 25.bus conductor design ond applications YS 2OZ. The most important factors governing the bending of bus conductors are: (I) the ductility of the conductor. but also on the ratio of wall thickness to diameter.) Alloy and Temper Estimated Average Stres$ PSI 1350-Hlll 1350-H12 1350-H17 and 6101-T61 6101-T6 6063-T6 6061-T6 2.500 18.000 15. However.2% ott set per ASTM Standard.000 --<.0% creep at 100°C. (3) the method of bend ing.-- Aluminum bus conductors can be formed by the same procedures and practices that are used for other metals.000 parallel to the initial straight diagonal line denotes the yield strength (YS) of the alloy.000 24. A metal must be ductile enough to permit both stret ching and compression to take place. Yield strength (YS) is arbitrary at 0. but the EL values are believed to be conservative. In the case of edgewise bends of rectangular 1350-H1l1 TABLE 13-4 o 0-002 Creep Factors for Aluminum Bus Conductors Fig. thickness bus bars and '/1 in. Note: The shape of the curve between EL and YS is not always consistent. Creep resistance and compressive yield strength are both impcrtant factors to be considered in the design of bolted joints..Hill IS SIMilAR) 1350-HU2 5. the sharpness of a bend depeods not only on the diameter of the tube. in the case of a tube. Approximate tension stress-strain curves at 70"C on guaranteed minimum basis tor aluminum bus conduc tor alloys-'/1 in.4-U eons 6061-16 35. A combination of a high elongation value and a low ratio of yield strength to tensile strength provides the most satisfactory ductility. assuming well-designed bolted connections. . For shop work. For best forming capability. Bend Properties of Bus Bar Extruded. H111 MANORU RADIUS in. TABLE 13·5 Flatwise Bending Radii AllO'( AND TYPE Of BAR in..000 1 x thickness 1'h x thickness .hlckness 0. Bend radii for greater widths are subject to inquiry. 1.000 1. as in industrial and chemical plants and seacoast en vironments. Edgewise bending radii are shown in Table 13-6. This can be done readily by applying a torch for short time to the opposite sides.125·0. min.376-0. rolled.501·0.500 0. Fig.501-3.000 I 1. the supplier should be advised and specifications written to require seamless pipe made by the hollow ingot process (ASTM B241).3. .751·1.749 0. are often bent to form turns and offsets.000 1 x thickness 6101·T65 0. 13-4.~Ol·2.001. and sawed-plated bus bars are capable of being bent flatwise at room temperature through an 13·8 Resistance to Corrosion Aluminum bus is highly resistant to corrosion.bus conductors angle of 90 degrees to minimum inside radii as shown in Table 13-5.750 0. For installations where considerable bending is required.751·1.500 0 . inside radii of five to seven times the nominal pipe size for ASA schedules 40 and 80 pipe of alloys 6063-T6 and 6061-T6 should prove satisfac tory with most types of conventional bending tools.250·0. For substation construction.500 The need for lubrication depends on the bending method and technique used. More generous radii may be used for appearance. T63 and T65 tempers and to widths up through 12 inches for all other listed tempers.000 2 x thickness ! 6101-T61 I : 6101-T63 ! .125·0.000 3. Benders having formed hubs andlor followers provide minimum bending radius for 6063-T6. When doing this.000 bar.85.501-4. However. therefore. care must be taken to avoid overheating.500 Bending Tubular Conductors Tubular conductors.375 0.501-1.• 2Yzx . including operating voltage.750 0. Producers do not normally control to such ratios so it is important to specify that critical.749 1 x thickness 2 x thickness Rolled 1350·H12 All 1 Sowed plo1e 1350·H112 All 1 x thickness ! 2 x thickness x 1hickness CDAppticable to wldtM up through 6 inches in the T6. .125·0. Lubrication is seldom required when bending with roll or ram type benders. 1350·Hll All .750-1. A calibrated crayon type indicator is recommended. . 1'. Best results are obtained if lubrication is provided wherever a relative motion or sliding action occurs between the work and the tools. Heating to 2OQ°C (392 F) will cause little loss of strength.501 .001·2. tests have shown that the radius (in terms of width of bar) around which a bar can he bent satisfactorily depends not only on the ductility of the bar but also on its ratio of width to thickness.001·1.~00 3 .500 0. as well as in some compression and stretch-bending techni ques. 6061·T6.001·1. severe fornting will be encountered and optimum heat treatments are required. the ratio of tensile yield to tensile ultimate should not be greater than about . alloys 6063-T6 and 6061-T6. a forming-roll bender should be con sidered. Tbl. 6101·T64 iJ) 1 x thickness ! 0.625 1 x thickness 2 x thickness 3 x thickness 4 x thickness 0.500 2 x thickness 21h x thickness 0-125-0. y. Its uses are. it may be necessary to apply heat. x thickness 6101·Hll 0. ampacity requirements.000 Q Lubrication WIDTH OF BAR 1.501-0.' 2 2.n~ Up thru 0. Bus Conductor Shapes and Shape SeIedioI1 Choice of a bus conductor shape for a given installation is dependent on a number of factors. available short circuit cur . particularly widespread in applications where strong aonospheric corrosive factors are at work.125·0. 2 .500 0. For the occasional problem job where material of high yield to tensile strength ratio is used.376-0. and 6101-T6 tubes. TABLE 13-6 Edgewise Bending Radii 1350-H12.375 6101·T6 i Exiruded RADIUS TEMPER I ! THICKNESS 0. lubrica tion is essential in fully tooled draw-bending operations. store. Off-sets and 90-degree bends are easily made. mechanical strength requirements. 13-Se) has low skin-effect ratio. and at slower speed. the capacity of a bus constructed of flat bar can be controlled by merely varying the size of bars or number of bars in parallel.) Internal cooling of the tube by forc ed air or circulating coolants overcomes this handicap. The electrical characteristics of round tubular bus have led to its use for heavy-duty generator and switching buses in central stations. however. IARE'j No. available space. If requirements are less severe. as compared with that of flat bar. however. and has the advantage of re quiring comparatively simple adapter plates for mounting the bus On pedestal insulators and the other flat sides facilitate attaching pads for taps. Joints and taps are readily made by either bolting or welding. wind.2 No. the smooth surface finish (industry class IV) should be specified. 13-Sa) This shape is in herently easy to fabricate. similar to that of round tubes. / '/ / AREA No. I-No Mandrel or Wiper Die Area No. supports must be more closely spaced to resist load and short-circuit forces that are applied perpendicular to the wider surface.4 ~ -t_ O . to reduce corona and radio-TV interference. the higher-strength aluminum alloys are used. often in protective enclosures. special arrangements of laminations are used (See ac Applications. for op timum wall thickness.3 7 I II 8 I 6 1/ 7 / / / AREA No. 4--Two Ball Mandrel and Wiper Die Area No.5-Not Practical Fig. Where tubular bus is to be used for high voltage circuits (230 kV and higher). Tube bending chart (with modern equipment). ice. page 13-12). ambient conditions of sun. For high-amperage alternating current. I I I I V I. Square tubular bus (Fig. Tubes oj alloy 6061-T6 also can be bent but more care must be exercised. Showing limits oj cold-bending radius jor 90° bends oj usual sizes oj aluminum tubes oj alloys 6063-T6 and 6101-T61. (See "Skin Effect.bus conductor design and applications rents. Since strength is a primary requirement of tubular bus. For maximum uniformity of mechanical properties at all points of the circumference.2-Plug Mandrel and Wiper Die Area No.. is not often commercially practical except for electric fur naces.3-One Ball Mandrel Area No.5 RATIO. Aluminum 13S0 is preferred because of its high con ductivity. The following review of the most common shapes and their typical characteristics is intended as a guide to bus shape selection and an introduction to bus system design. as well as the forces of short circuits. 6061-T6 tubular conductors are used where particularly high strength is desired and conductivity requirements are lower. 6063-T6 alloy in ANSI Schedule 40 pipe is used widely for outdoor tubular buses because of excellent mechanical and electrical properties and availability. \/~~~ 1\' ~'-~ / I 4 """ ~ AREA I) I 0 Rectangular Bar The most common form of bus conductor is bar stock of rectangular cross section. tubes are produced from hol low ingot and extruded by use of the die and mandrel method (ASTM B24I).D. For direct current. because of the smaller ratio of heat-dissipating surface area to volume. but AREA No. 6101-T61 and 6063-T6 alloys are principally used. and staggered ventilation holes often are provided in top and bottom surfaces.1 2 I I /I I - . etc. 134. Because bars are mare rigid in the direction of the large cross-sectional axis." page 13-12. "structural" tubes made by the bridge-die process are often used (ASTM B429). D. THICKNESS OF lUBe WALL TK Area No. The in herent rigidity of a tubular shape in all directions resists wind and ice loads. For this reason it is used for generator-phase and station bus. 6 4 Tubular Conductors Round tubular bus conductors (Fig. 13-Sh) are used primarily for outdoor substations and switching structures where long spans between supports are required. A relatively large surface area can be provided for the dissipation of heat by the use of multiple-bar buses. Integral Web Channel Bus (IWCB) The integral web channel bus conductor (Fig. Since the design of modern isolated phase buses is such that short circuit forces are not a prob lem. (Fig. 13-Sf and g) is extruded in the form of two channel-shaped conduc 13-9 . The round tubular bus is the most efficient electrical shape for an a-c bus conductor because it has the lowest skin-effect ratio of the commonly used types. The current rating is limited. OUTSIDE DIAMETER OF TUBE = o. as well as for alternating current up to certain limits. handle and erect. .------- Steel shae~1 I \.). or full rounded edge... .189 to Looo in.. slightly indented grooves can be ex~ truded horizomally along the outer surface to provide centers for drilling or punching holes for attachment of supports or take-offs.... Notes: (1) If extruded.I (n) Fig. (3) Lugs that facilitate attachments as well as add conductivity may be included as an integral part of the eX trusion. Typical bus conductor shapes. radius.. nominal for 0. 13-5. radius for thicknesses to 1 in. rounded corners (1116 in.bus condudors DO 01 ) Rounded Corners 1 Vents (d) (e) (b) (0) Full Rounded Edge I I t Vent I I t Vent V (nl (e) Steel Face \ ". thickness). (4) Flat bars may have squared corners (up to 1132 in. (2) Shapes such as band d may have equal thickness along any element of the section. . Of if roned as a structural shape the thick- 13·10 ness will vary to correspond to the slight bevel of structural I-beams and L's.. . 13-5c and d) provide excellent transverse rigidity and ampacity. is not recommended for large alternating current because of the tendency of the current to flow only near the "skin" (outer surface) of tbe rod. space available. These buses have narrow shallow grooves extruded on tbe surfaces for convenience in locating centers of drilled or punched holes for attachment of taps and base plates. Such a con ductor is very efficient and practical for high-amperage direct or alternating current. may require round rod bus conductors. commonly called UABC (Universal Angle Bus Conductor) is a bus form used for moderate-size outdoor substations at distribution voltages. between tbe webs of tbe two channels. Crane-runway bus shapes (Fig. especiaily in the high-voltage field. Because of the various bus shapes available to the designer and their possible physical arrangement. A flow diagram illustrative of this iterative design process for outdoor substation bus is shown in IEEE "Guide for Design of Substation Rigid-Bus Structures" (I). but the transverse strength is greater.Structural Shape and Uniform Thickness Special Shapes Structural shape aluminum channels consist of a pair of channels forming a hollow. Channels . steel facing is fitted to the aluminum bar against which the collector shoe slides. 13-5k) has more transverse strength. Approaching the electrical efficiency of a split tube. Factors Affecting Bus Design It is important to start with a tabulation of the factors that may affect bus design. 13-5b) may be desirable for enclosed station buses where the space oc cupied by the conductor is critical. The continuous web eliminates the need for spacer clamps or welded tie-bars that are normally required across the two channels between between insulator supports. This results in uneconomical use of the metal in the central portion of the conductor. corona. open or enclosed. aluminum channels are sometimes placed back-to-back tbat is. Angles The face-to-face paired angles (Fig. The extrusion process provides the designer of aluminum bus conductors with the means of making special shapes when none of the previously described shapes is wholly suitable. Convection air flow is less than that of the face-to-face channel arrangement. Their use has largely been supplanted by the uniform thickness angle. In some applications. Uniform thickness angle.' Temperature Rise Effect of Conductivity The ratio of currents tbat will produce the same ·Num~ references in the text relate tv bibliography at the end of tbis chapter. Channel shapes of uniform thickness (Fig. For outdoor substations. (Fig. maximum ex pected icing conditions. The shape is used for station bus. the design problem may result in successive calculations involving all the factors affecting. 6101-T6 alloy is principally used for these angle shapes. taps and connections required. maximum possible short circuit cur rents. Direct application of pads and. (2) voltage drop. ventilated square. and for the high-current buses of out door substations for distribution voltages. Where large currents are involved tbe factors that affect the economic current density should also be tabulated. operating voltage. Such an arrangement may be more convenient to support than a hollow square. An adaptor plate is sometimes used for expansion moun tings and to accommodate vari9US bolt-circle diameters. and since both legs are of equal thickness at all points. the bus may be mounted directly on insulator caps. colUleclOr plates is aided by the uniform thickness of the legs. allowable voltage drop. ampacity required. but require special spacer fittings. otber factors should be tabulated.bus condudor design and applications tors held together by a ventilated web. and also for 600-volt bus for industrial plants_ Round Rod Some installations. fre quency. I3-5n and p) are illus trative of how low-cost extrusions can be produced for special needs. and the upper flange does not extend far enough to interfere with hole drilling. The aluminum body of these bus conductors is shaped to combine ampacity and structural adequacy. Angles are commonly used as singles. properly spaced. For de circuits. however. tbis bus has tbe added conve nience of flat surfaces for making taps and connections. witb flanges pointing outward-to form a con ductor. The semi-channd form (Fig. This type of channel has a small inside radius and provides the maximum flat surface inside for connections. Center-line grooves facilitate location of bolt holes. Structural shape angles witb slightly beveled legs. etc. such as: doc or a-c current. (3) power loss economics. similar to the type used for steel structural shapes are sometimes used. where skin effect is not a factor. 13-5m). such as: maximum anticipated wind speeds.000 amperes per circuit. IWCB combines some of the advantages of tbe double-channel bus and the square tubular bus. This type of con ductor. Fittings used are similar to· those on tubular buses. the design. especially above 2. 13·11 . Additional capacity is readily obtained by merely adding one or more flat bars. For industrial bus the decisive factors are generally: (I) ampacity for allowable temperature rise. copper bus bar sizes can be converted to aluminum sizes for equal temperature rise by either of the following two methods: l. equally applicable to all conductor materials. A 4" x 3/8" aluminum bar is equivalent to a 4" x ~. Energy savings due to lower current densities are. a 5" x .I copper bar. such use is generally limited to swit chgear assemblies and metal enclosed bus (IEEE Standard No. the skin effect ratio may be taken from the curve tid =0.50 in Fig. 13-1) __ /61. 6063 and 6061."" aluminum bar is equivalent toa4" x . Increase the thickness of the aluminum bar about 50 percent. A change in thickness of a rectangular bar does not ap preciably affect the amount of exposed surface area. ac Applications In addition to the factors that affect the design of a de bus. and to squares made up of angles. Designers of heavy-current bus systems are ad vised to factor in the cost of energy. Increase the width of the aluminum bar 27 percent.9 percent for 1350 alloy 98. 13-7. bar by changing the width from 4 in. bar from !!.61. For example. once to produce the heat and again for air conditioning to remove the heat. for instance. may be operated at 90°C continuously. 13-6 applies to a single rectangular bar per circuit. of course. increases the capacity by only about 45 per cent. 13-8. ASA C37. 13-7 app!\es to square tubular conductor. The skin effect ratio depends not only on the size. increases the capacity by about 87 percent. For example. to squares made up of four bars. Interlacing of the bars or the paired-phase arrangement of fers an excellent solution to the unequal distribution of alternating current in low voltage bus systems. Operation at 100°C for emergency conditions causes very little loss of strength for alloys 6101.0 = V157 9s = 76. the skin effect ratio is approximately the same as would apply for a sine. However.. Skin Fjject The ratio of effective ac resistance of an isolated conductor to its de resistance is called" skin-effect ratio. but increasing the thickness of a 4-in. Temperature Rise . In such cases. Perhaps the most useful work for an engineer are the curves developed by Dwight as shown in Figs. Lewis developed formulas applicable for com puter studies (5). 2.i-in. Increasing the cross-sectional area by increasing the width not only reduces the resistance heating but also substantially increases the area for heat dissipation. hysteresis losses. Many in dustrial and utility bus systems are designed according to this practice. it becomes progressively more difficult to maintain good bolted joints as the temperature increases.0 = 78.. 13-8 (4).Ampacity Tables The ampacity for popular shapes and sizes is shown in Tables 13-25 through 13-32 for 30°C rise over 40°C am bient or a maximum of 70°C. .62) The cost of energy lost through resistance is important in the case of bus installations where heavy currents are used as. Skin effect takes place not only in single conductors. Fig. 13-6. to 8 in.bus conductors temperature rise in aluminum and commercial copper bars of same size and same surface conditions can be determin ed from the following formulas: (Eq. but also in buses made of several bars. In some cases the user may pay for these losses twice. but also on frequency of the current and the resistance and magnetic properties of the material. both of an experimental and a thcoretical nature has been done on skin effect of conduc tors (3. proximity effect. 27. Although aluminum conductor. to squares made up of two channels in box form. induced circulating currents. increasing the area of a . the design of an ac bus is also influenced by such factors as skin effect.""copperbar. to liz-in. it may pay to use larger conductors than those used in the ampacity tables.26 percent for 6101-T61 alloy Ejject oj Dimensions Tests show that for practical purposes. Flat bars can be arrang ed to minimize skin effect to some extent by the use of hollow square and modified hollow square arrangements.le bar equal in size to the two bars plus air space but of Rdc the same as that of the two bars.. in the electrochemical industry. For two bars in paraUel."-in. Considerable work. Fig.4). 13-12 Energy Loss (2. and mutual heating effect. separated by an air space. I2R losses associated with bus-size choices. and the probable "pay-back" time for the additional expense of larger conductors. the designer should hot overlook the fact that the I2R losses are higher for the higher temperatures. Experience has shown that designs using these temperatures have good service records. shape and configuration of the conductor.20). For three or more bars in parallel. " The 60 Hz Rae/Rdc ratios at 70°C for the commonly used shapes are shown in Tables 13-25 through 13-32. Also. lrht.::- I I /I I Tj 1// i i / I . "Elt'ctnc"l C\lil~ nod Ctmtln<.!/ ~i ":'1 ~ I i 1.5 I / If . ...bus conduc1or design and applications 1. Curves for skin effect of isolated flat rectangular conductors./' 1..4 fi : I I w I I / I . \' J i / J 'J 1. Fig.. 13-13 .tOI)l.0 .1 . Dwi./' o 20 \J f. j.3 I J I ~ ~ r I :. II V I I... J3-6./ I iL1. ..2 'I If J I V J/ I J 'J ! /.. / / i V i i/ ... H." McGraw-Hill Book Co.l03 80 40 100 120 \40 160 180 Rde IN MICROIIMS PEl FOOT 11. / i I 1/ 1/ i 1. / / / -II . 2 200 ~ . S.. Curves for skin ef1ect of isoluted square rod and square tubular conductors.~ Rdc 2$0 300 IN MICROHMS PER 'DOT H." McGraw-Hili 'Buok Co.'1cctnooi Coils and ConC:uctors. 13-7. ·'f.bus conductors D-t 2.8 1. Fig. 13·14 .0 1.tht.4 1.. O!ll"JJ.9 1. '_a:t ® 100 .2 .w. 1.6 ~o. 13·15 . W.0 . I 1.7 . J .: .. +~i 1.9 f- . :~ 1.bus conductor design and applications 2. . ~ . ." McGraw-Hill Book Co. 1.0 .:0 2® Vko~ Relc IN MICROHMS PER fOOT H. Ii. tN 2. 1. . l. . . Fig. . . Curves for skin effect of isolated round rod (md tubutar conductors. 1.4 . B.1 .50 Rdc 200 .. 1 o . "Electrical Coils and Contluctors. V1Ji . . . 13-8. I .5 If .Wl :mtt ::11 f .~ ffi i . . lid =0.3 • 11 1. .:io . l.~. "I .)widtt. . . . BI C. 182 1C2 C. the increase is negligible. B IOB.3 C Paired Phase Arrangement 1C3 I nterlacixl Bars Note cross ties from A toA. B. conductor shape. Dwight (4) states that the skin effect ratio is verY low for interlaced construction where bars are close together in parallel planes and where neighboring bars have currents that are always either 180° or 120° out of phase. proximity effects are negligible for phase spacings of more than three or four times the largest dimension of the cross-section. known as "proximity effect. cross·section dimensions.20 of ac resistance. the proximity-effect factor will not be more than 1. The magnitude of skin effect increases with wall thickness. These ar rangements have lew reactance and greatly reduced skin effect and proximity effect. Here. Proximity Effect (4. Curves plotted for a-c ampacity (lac) and Rac at 70 0 e ver sus wall thickness (all sizes of tube) show that Rae will be a minimum and lac a maximum at about 0.IGse arrangements in common use. The proximity of A-A and C-C bars serves to reduce crowding of current into the middle pair of bars (A-C). IAl iSI 8 B. The essence of paired-phase perfor mance is that the currents in each closely spaced pairs of bars are essentially equal and opposite (8). frequency of current and de resistance. C2 IA3 I £.. With spacings of about five times the diameter. 13-9. There are several other paired J. 13-16 . The amount of distortion depends on a number of factors-the spacing and arrange ment of conductors.6. Interlaced and Paired Phase Arrangements The usual frequency found in industrial work in North America is 60 hz.7). a distorHon of cur rent density results from the interaction of the magnetic fields of the conductors.8 inch for 6101 alloy. when isolated. As a rule. The interlacing of bars and paired phase arrangements (Fig." causeS an in crease in the effective resistance.. More accurate proxintity effect calculations are available (4. The paired-phase arrangements (8) are widely used by AI (. Paired-phase feeder busway (left) showing end-connections for AS AC BC arrangement. 1<. C. 6. 13-8 applies to isolated tubular conductors.bus condudors Fig. This distortion of current distribution. for round tubes whose distance between centers is twice their diameters. This makes for an efficient use of bus bar materiaJ in that the ac ampacity approaches the dc ampacity. I< ICl IA2 B. 7) When conductors are close together. the approximations should not be used. 13-9) offer an excellent solution to the unequal distribution of currents in low voltage systems.7 inch for Aluminum 1350 and about 0.anti CloC Fig.. For fre quencies higher than 50 or 60 Hz. The designer should check the notes of the ampacity tables to ensure that the values given apply to his design conditions. it is first necessary to determine the Rd. If there are steel members in the field of an ac bus. Induced Circulating Currents (12. The inductive reactance per pair at 60 Hz is as follows: 13-17 . together with other characteristics such as resistance. Example: Assume a three-phase symmetrical flat bus arrange ment in which each conductor comprises a pair of 8-in. Values of Xjj which are functions of GMD for various distances are given in Table 13-7. at 60 Hz is ex pressed: (Eq. 14. there is no loss in the steel since the magnetic field for a non-pulsating de bus is static. then Rae "" R.3-in. current capacity and weight. vertical or horizontal ar rangement. nO magnetic losses or induced cur rent losses. Mutual heating occurs for both ac and dc current flow. and sun effect for outdoor installations. Temperature Rise . Arnold. Heating Due to Magnetic Materials Near the Buses (J J) A bus carrying high current creates a magnetic field of considerable magnitude.13) Induced circulating currents in nearby metal items re quire energy which must be supplied from the inducing cir cuit. and open or enclosed bus. for conductors that are normally used as a unit. Lewis suggested break ing the total reactance of conductors into two parts so they could be tabulated as a convenience to engineers (16).375-ln. are sometimes designed so that the bus assembly is divided into several sections where the in dividual conductors. This problem is en countered chiefly in the design of switchgear isolated phase bus. formulas for calculation have been developed for conduc tors of simple shapes (6). For close spacings. Reactance (4. '13-8.Ampacity Tables The a-c ratings of commonly used shapes included in Tables I}-25 through -32 have been determined for 30°C rise over 40°C ambient in still but unconfined air. 13-6. Calculation of ac Resistance The calculation of ac resistance is based on the assump tion the Rae is affected only by skin effect and possibly proximity effect. The total reactance in microhms per ft. and at spacings where proximity effect is negligible. relative to the size of the bus bars. Having determined the skin effect ratio and the proximity-effect ratio. tables and charts for the determination of reactance for many conductor shapes and arrangements. the basic calculation 'of reactance is a complex mathematical pro blem. The mutual heating varies with bar spacing. Figs. at the design temperature. insulated from each other. each individual conductor of the hus assembly can be made to share the current equally. Mutual Heating (10) Mutual heating is due to the interference of one conduc tor on the heat dissipation of the other. Although Xjj is actually based on the GMD between the conductors.:lc x skin-effect ratio x proximity-effect ratio.26 x 36 .. In the case of dc buses. other air conditions.:urrent conductors can usually be made if GMD is taken as the distance between center lines of the conductors. are transposed so that each individual conductor runs for an equal distance in each of the available positions -thereby making the mutually induced voltages equal. such pieces will be heated not only by the current induced in them but also by hysteresis. Lewis and others have developed equations. Allowance must be made for proximity effect where applicable. altitude. the magnetic fields of the flat bus arrange ment do not cancel out and undue heating results unless preventative measures are taken. apart (center-to-center). The effect is an increse of the Rae for the circuit. The magnitude of the "skin-effect ratio can be conveniently determined from the tables for electrical characteristics of commonly used shapes or from Dwight's curves.in. Welded connec tions are preferred for both mechanical and electrical reasons. corrections for GMD must be taken into account.J5) Maxwell. other temperatures. Because the physical shapes of bus conduc tors do not lend themselves to simple formulas. Schurig. Where proximity-effect may be a factor. Transposition High current a-c buses. resistance for other alloys and tempers. other surface finish. Dwight. The equivalent GMD spacing is 1. Higgins. 13-7. a sufficiently accurate approximation for heavy. In order to simplify the problem. such as "side bars" for carbon baking furnaces.bus conductor design and applications manufacturers of prefabricated bus systems.g. To find the ac resistance. By this means. x g. the conductance of the metal item. Interlaced ar rangements are used primarily in high current electric fur nace installations (9).. and the distance of the bus to the metal item.. The frame in the wall of a building for the passage of the bus should either be of non-magnetic materials throughout or constructed so there is no complete magnetic ring. x 0. e. The magnitude of the loss is a function of the amount of induc ed current. 45. Even though all of the three phase conductors pass through the same opening. Aluminum channel and IWCB shapes provide structural stiffness needed for the portable single-phase bus assembly. face-to-face equal thickness channels spaced 36-ln. 13-2) Xa vafues are given in Tables 13-25 and 13-27 through 13-32. 77 26.86 23. Spacings less than 12-in.60 31.39 35.32 11.88 32.87 25.88 35. have minus sign.67 33.40 39.61 19.55 50. For usual distance.14 38.50 5 4 -25. the value.----- Feet 1 0 1 2 3 4 5 6 7 8 2 -57.26 4B.93 30. and Feet per Left·Hand Column .86 35.81 29. and the associated voltag.11 42.37 41.06 49.93 23.47 27.38 36.88 47. (1 ft radius value) obtained from tables of conductor properties. single~phase • • bus circuits the spacing to be used is the center~to-center distance between conductors.26 -31.86 44. for 50 Hz.separation component) Xd from the above table represents the inductance of a cQnductor at 60 Hz caused by flux that is more than l·ft distant from the conductor.61 12.18 44.79 3 -41.47 42.18 7 -12.19 13.99 39.00 14.13 18. to 107·in.74 22.60 46.18 3.73 -20.60 40.31 49.: ~ Separation .93 9.99 48.28 50.18 43. are per conductor.72 46. B <----C • • Unsymmetrical Flat GMD ~ AxBxC ~ C Symmetrical Triangle GMD = A or B or C For voltage drop calculations the X.99 41.56 49.63 -6.06 28.32 21.84 16.86 35.86 43.07 '- -The inducHve reactance spacing factor (also called.25 31.49 44.26 38.53 48.21 40. the value i. 50/60 of the value of 60 Hz. GMD Spacing . is that to neutral.72 47.52 43.Inches.24 34.96 6 -15.57 39.80 37.31 46.12 4&.71 1.56 21.33 37. For 3-phase circuits the spacing is the GMO A • C B • Symmet~ical Flat GMD = 1.44 47.28 28. .81 49.79 48..64 29.81 40.17 47.55 44.83 42.00 20.33 34. For other than 60 Hz.09 33.79 34.41 8 9 10 11 -9.25 30.05 48.93 26.30 -2.03 0 1&.42 45. as these represent deductions from the X.86 5.95 24.54 17.20 43.81 45. plus Xd value. are in proportion to H~: that is.49 32.26 6.85 -4.~ 0 • Iii GO TABLE 13-7 i Inducti•• Reactance Spacing Facto" Xd ' Microhms per foot at 60 Hz for I-in.12 8.74 41.39 10.02 46.70 38.26 A • • A.64 27. and lower. Corona and Radio-Influence Voltage (RIVI Corona forms when Ihe vollage gradient at Ihe surface of a conduclor exceeds the dielectric strength of the sur rounding air and ionizes the air molecules. size or arrangement.::I 3. square tubes and round tubes (4).:. The most recent extensive test work that led to general equations for calculating bus ampadty is by House and Tuttle.. Ampacily of Aluminum Bus Conductors The subject of ampacity or "current carrying capacity" has intrigued engineers from the beginning of electrical power usage. 13-10. 13-19 . the equations tend to be on the conservative side. radius at 69 kV.i &1 lil a 2. However.. Their report gave the first experimentally determined formulas for calculating the ampacity of bus conductors based on temperature rise. early engineers tended to use the "rule-of-thumb" of 1000 amperes per square inch for copper and 600 amperes per square inch for aluminum for any conductor shape. Although this work was a big step for ward. The four basic factors that delermine voltage gradient are: (1) conductor diameter (or shape). ~ 1 2 3 4 5 6 7 8 9 10 11 12 NUMBER OF BARS Fig.bus conductor design and applications I. Corona rings are also used to shield fittings and flexible connections. Dwight's formulas give values for a single bar with a dull paint surface that closely approximates Melson and Booth's values. 13-29). The shape of Ihe bus conductor is probably the most critical factor in reducing corona.0 microhms per ft 30. RIV is caused exclusively by corona. for large buses. (2) distance from ground. Xa (from Table 13-30) Xd (from Table 13-7) Total reactance' X 22.000 [-r-'rT-r-'-~=~:::::!:::I::~::. Corona usually is not a factor in rigid-bus design at 115 kV. such as bars wilh separalion equal 10 the bar Ihickness. (3) phase spacing. additional work was done on bus conductors using the same fundamental heat balance equa tions (19).Reactance When there are Iwo or more closely spaced bars per phase. To avoid corona and RIV. by a single solid bar occupying the space taken up by Ihe group (15). and (4) voltage_ A smooth surface condition may be important if operating near the critical voltage gradient. With little to guide them. particularly buses composed of a large number of bars (Fig. Ihe group may be replaced. The industry's need for scientific ampacity information led to the first extensive tests toward developing ampacity data and formulas for calculating ampacity for both cop per and aluminum bus conductors by Melson and Booth. Circular shapes will generally give the best performance. the limitations of the formulas led 10 many specific tests.000 ~ II! '" 1. Dwight's work was another big step for ward in that the scope of conductors tested was expanded and also gave engineers formulas that check test results closely for the range of conductor sizes tested. Current capacity not increased proportionately to number oj bars in parallel. for rough calcula tions. Although the published work is for current carry ing capacity of ACSR. and 10 larger radii al higher voltages. but only about 25 proved of interest to their study (17). The next extensive experimental work leading to for mulas for calculating ampadty was done under Dwight and covered multiple bars.J <. bus shapes and fittings should have corners rounded to at least 1116 in.4 microhms per ft 52. Carlson and Van Nostrand made an exten sive search of the literature and found more than 1500 titles.000 . British National Physical Laboratory (18).4 microhms per fl Consolidation oj Multiple Bars . (..] - Convected heat loss Watt/It Radiated heat loss .. e M Conductor temperature °c Ambient temperature °c t -t c • 0 Conductor temperature K Ambient temperature I> K Emissivity is<la Tabla 13-11) Lxw = L+w [(.:. .0720°·75 • ftc _ \)1.. L Pc :::0 . < w 0.026 Pc 2N (L+w) Pc ~ ( ~.25 2 (L+w) . p 0 w N !:: 0. Radiated Heat Watt/It "'' ' .Indoor Bus n o. 12/1 \ Kc K. W. .- 0 w S.!:.0275 Pc P c ~ ( f5 ~t ~I[] OT 01 to. ~w~ ~ I Configuration ~+- Wc Convected He.138D • e P.:~ )4] .~ )4 (.-1 \--w--j ~~ W ------ • • At 0..95) ~Equation must be modified if .~)' -(. • ~ TABLE 13-8 S " :} Heat Loss Equations -.t Watt/ft 0.Watt/ft tc Height in inches Perimeter for convection in inches At :: Perimeter for radiation in inches Conductor diameter in inches Bar width in inches Number of flat b. . = 2 (L+w) = 0.35) ''''''. = 2(L + NW) (Bars) ie = 2(N .: Bu. ·[(.." .::. )"25 • At 0.l)W (Spaces) (e We == W.·[( ..:~ i] p... Shape IWCBor Hollow Square Channel Flat Bar Round Tubular ----- A2 B2 C2 . several investigators have conducted tests on a limited scale. Under steady-state conditions of wind velocity. Fig.Ws I = Reff The ampacity values of the most commonly used large tube conductors are shown in Table 13-28 for a-c current. the effect of painting a single I" x 10" bar is to increase the ampacity about 15 percent. Papst conducted a great number of tests on various ar rangements of bars in efforts to find the most economical ones (18). the following general equation is valid. the ef ficient use of Ilat bars for aC buses (60 Hz) in conventional same plane arrangement is limited to about four liz in. 13-10 illustrates the decrease in value for each bar ad ded from 1 to 12 bars (3 x V. using 30'C rise over 4O'C ambient in still alr. However. using 30°C rise over 4(fC ambient in still air. (Eq.23). cu. Table 13-9 lists approximate emissivity constants for typical conditions. Pemberton. using 30"C rise over 40'C ambient in still air. ambient and conductor temperature. amperes For indoor locations where Ws = 0 and Wcond = 0: I = YWc + Wr Reff Equations for use in calculating convection and radia tion heat losses have been developed by House and Tuttle and are summarized in Table 13-8.OOO) and the formulas given in a paper by Prager. Ampacity (IWCB) 12Reff + Ws = We + Wr + Wcond The ampacity values for standard sizes of IWCB are shown in Table 13-32 for dc and ac current. Where: Ampacity for Outdoors Bus Conductors We = Convected heat loss. aluminum bars per phase. The formulas and computation methods used are similar to indoor. The curve shows that four hars will carry about 70 percent as much current as 12 bars. 60 Hz) for the same plane arrangement. taking into account different ¢oefficients for outdoor convection losses and in cluding solar heat gain. 13·21 . the same rigorous combina tion of tests and theoretical study that was done on stan dard conductors by House and Tuttle (19) has not been done for tubular bus and shape conductors outdoors. The most extensive tests of tubular bus conductors for outdoor service were done by Schurig and Frick in 1930 (21). solar radiation and electric current. Watts/ft Wrond = Conductive heat loss. However. Craig and Bleshman (22). the percen tage drops off since the effect of improved emissivity ap plies only to the outside surfaces.bus conductor design and applications Heat-Balance Equation of Electrical Conductors (General) (20) shapes. Watts/ft Reff = Effective resistance I = Current. but the difference is so small that for Or dinary calculations they may be taken as equal. Emissivity and Absorptivity Ampacity (Vertical Bars) The ampacity values for standard sizes of bar and com monly used bar arrangements are shown in Table 13-26 for ac and de current. Watts/ft Wr = Radiated heat loss. For example. Painting of the outer bars very closely equalizes the temperature differential for four bar ac buses. The closest agreement of theoretical work with tests for pipe sizes shown in the tables appears to be the formulas listed in the House and Tuttle paper (using McAdams formula for convection for Reynolds numbers 1000 to SO. in. The emissivity coefficient varies with the surface condi tion of the conductor. A$ multiple bars are added. This leads one to con sider that it is more desirable to paint the outside bars of multiple ac bar buses than dc buses since the outer bars in an ac system tend to run hotter than the inner bars because of skin effect. Since then. Watts/ft Ws = Solar heat gain. the sUPPCrts are more costly and must b~ spaced closer together than for square tubing Or box channel Emissivity (heat radiating characteristic) and absorptivi ty are not precisely the same since they apply to different energy spectra. apart. 13-3) Ampacity (Round Tubular Bar) -yWe + Wr + Wrond . Effect of Painting The ampacity of bus conductors can be increased for a given temperature rise indoors by painting with a dull finish paint of non-metallic pigment. One arrangement.• 3/8 in. has a low skin effect ratio similar to a square tubular conductor. the hollow square arrangement. The ampacity of a single conductor can be increased by 15 to 25 percent for the same temperature rise (-18. Multiple Bar Arrangements For direct current the capacity of a bus constructed of rectangular bar can be controlled by merely varying the size or number oflaminations in parallel. However. . . . . . . .95 4 ••••• . . . . .50 Painted surfaces (dull finish) . . .. . .45 Normally Oxidized 0. . . . . . 13-4) wbere I = amperes T Papst = Temperature Rise in °e (17) also found that wben the hot-spot . . . . . the metal of the enclosure is chosen for heat conductivity. . . . . . . . . . .30 ____________L __ _ _ _ _ _ _ _ _ _ ~_ For calculations. . . . The conductors. it is necessary to use the proper value of emissivity for the conductor.20 Polished Shiny Slightly Oxidized Old Bar-2 Vear Indoors 0. . . . . • .Radiation Emissivity Coefficient New Bar-Extruded New Bar-Cold Rolled New Bar-Hot Rolled 0.. states tbat with today's emphasis on energy conservation tbe economic effect of losses in any conductor system should be carefully considered (17). because of space limitations and high beat concentrations.15 0. . . . . . .bus conductors TABLE 13·9 Radiation Emissivity Aluminum and Copper Surfaces T ~. . An exception is the table on flat arrangement of bars which is based on limited test data. . ••••••••••••• . .. 0.10-0. 0.20 0. . . . . . . Unavoidable varia tions show up in test values because of tbe physical im possibility of exactly duplicating every test condition. .90-0.70-(MIS Flat Paint 0. . . This arrangement has not Fugill (24) derived the formula which sbows that the temperature rise varies. . ' . . . Ampacity Tables Current vs.50 Old Bar-2 Vear 0. . . . Agreement within the range of test accuracy has been obtained bet ween test values and calculated values. . . . .90 Openings between members of built-up bars . . . . 0. . .. . .as the 1. . .95 (non-metallic base) ____________________-L________ ____ ~ Radiation EmiHivity Coefficient Copper Surface ~L_" 0. •• Isolated phase bus. . in comments on Carlson and Van Norstrand's paper. . . . .35 Outdoor current ratings (normally oxidized surface) . . the following emissivity values are assumed to be representative: New Bus . . . . . . . . . . . . The beat loss wiU vary considerably witb various surface conditions. • ..05-0. . . . . .50-0. . . usually tubes or structural shapes. Craig. . . The designer sbould remember that ampacity tables are based on thermal conditions for the conductor and may not represent tbe most economical overall design. . . . . are painted for maximum emissivity. .03 om 0.10 Indoor current ratings (partially oxidized surface) . 1350 Aluminum Surface . 0. been given tbe rigorous study that vertical bar ar rangements bave received. . is a particularly good application for painted conductors. . . the outside of the enclosure is painted for maximum emissivi ty. . .90 Heavily Oxidized 0. . . .05-0. . Temperature Rise The ampacities shown in the tables are based on calcula· tions using modern heat transfer technology. . . .7 power of the current: 13·22 (Eq. . .95 I ' Outdoors Flat Paint 0. When calculating temperature rise. . . the inside of the enclosure is painted for absorptivity. . 0. .24-0. . . . 4 / V u V / 1 1/ V V j / I ] . as a result of induced currents in the metal enclosure may be encountered as well as hysteresis losses in frame of enclosure. I. 13-11 shows the relationship in terms of load ratio in amperes to temperature rise as a convenient means of estimating cur rent for a different temperature rise than that shown in the ampacity tables (indoors) for various conductor shapes.7. Space limitations mean closer bus arrangements where proximity effect is a factor. Such proprietary data rarely is reported in the literature.Tent were plotted on log-log paper that the curves were straight lines having the same positive slope of 1. 1945 McGraw-Hili Book Co. when such buses are enclosed in reasonably large nonmagnetic enclosures. page 13-22). . Fig. Note: Based on calculations for de current using formulas from Chapter 9. Fig. the ampacity rating may be reduced to between 55 and 60 percent of open-air rating. other factors such as dimensions. shape and arrangement of conductors. test cu. finish of housing all have their effects on arnpacity of enclosed buses. ! . Calculations based on Dwight's work (4) show essentially the same relationship. Temperature rise vs.bus conductor design and applications . (See Eq.f \I 51 . some general comments may be helpful. However. The greatest reduction in arnpacity occurs with enclosed buses that depend mainly on free circulation of air for cooling. The current-carrying capacity of single tubes and bars is 13·23 . Enclosed Bus Conductors The design of enclosed bus conductors is considerably more complicated than open buses. temperatures of test bars vs. In addition. These effects are such that calculation is impossible except from test data on pro totypes. Additionall 2R losses.1 / / 1/ L . 13-11. load ratio curve for aluminum bus conductors. Checks approximately formula by Fugill. finish of conductors. 13-4. "Heat Transfer" of Electrical Coils and Conductors. " . 13-12.. Isolated Phase Bus Isolated phase bus. '911 . because of its use in connecting the output of generators to step-up transformers. the inspection period may be spread Over a longer interval.-'--"-+-+-I-+-i 1UI ~~ I . H. least affected by enclosure. Swerdlow and Buchta (11) give data for estimating temperature rise due to hysteresis and 13-24 eddy currents in steel members in proximity to unenclosed buses carrying large currents and include rules for applica tion to isolated phase buses. is a key ele ment in It power station and therefore deserves special at tention by utility engineers. E.-f+-I-'-. Shape correction factor K for the calculation of electromagnetic force.. Vol 70.'M!../_ V j j/ " Iu ro --t"r- l /.. The ratings of enclosed buses of this type may be reduced to between 70 and 75 percent of the ratings in still but confined air for standard temperature 'rises (24). 1. Short-Circuit Conditions The electromagnetic forces between conductors are pro . Continuity of service is of primary imponance for isolated phase generator buses.' i/ • I I I I Fig. By using welded aluminum conductors. ' .bus conducfors ~: Dw1GHT.• .' I I • .11I-1/+-1f+.ledtiall Wood.! VI V/ 1-/*''-i--V'''t--I:7'''l--7''+-++-+-+-HH-+-+-++-I . 8. IUPMls.. D ~ U i_Ii •. Power losses in the bus system are covered ill detail in IEEE Guide For Calculating Losses in Isolated Phase Bus (25). The design of modem isolated phase bus with its dust-tight and weather-tight aluminum covers has already reduced the frequency of periodic inspections.b>IJ Bt!IWUII StIVllJl CO".-L'-'I-L-L. Conductors subjected to such forces.2 . 13-5) where i l and i2 are instantaneous currents in amperes. F=Jb!ft of oondu<:tot 4".29. and supporting insulators and structures. Generally. The effect of this de compa nent is included in the formulas for maximum force.9/' L / ' d". elasticity and damping.4/' A Single Phase A Three Phase Asymmetrical B A orB Single !'base SymrretricaI Asymmetrical TMtantanl':Qus Maximum Forot on Conductort$ Conductor Arran. Formulas have been develOped which show the maximum possible instantaneous force on con ductors under various conditions (4.ement I_d-I B I-d-I A B B lOrd ! C C IO'd lO'd _d_CI IO'd lO'd I Q)"J"M ¢u. and d is the distance between conductors in inches. 13-12). d = 54 10-7 pounds per foot (Eq. B orC F=37. In asymmetrical faults. Table 13-11 lists the relative value of the components of electromagnetic force for Short-circuit. the repulsive force between positive and negative buses may be expressed as follows: {2 F = K5. round conductors can be found from the classic equation (4): conductors are relatively large compared to the distance between conductors. The in stantaneous force between two long. form dynamic systems that contain mass. If they flow in opposite direc tions.27). 13-5a) where K is the shape correction factor (Fig. the force will be one of attraction. Application 0/ Formulas (28.26. conductor spacing in inches N~te: In computina short-circuit CUlTcnU in networks... a force of repulsion is created.81' A or B F= 43. portional to the currents flowing in the conductors.2/' I_d_l---'i-I B F=37. Such 13-25 .4/' A I--I-d-I AorC F=34. Alternating Current (ac) F i1.7 pounds per foot (Eq. a de component also is present.rrent (I) 1$ In terms of RMS Symmc::cral. and in versely proportional to the distance between tbem.4 d 10. for practical purposes. parallel. The value of current (I) in the formulas in Table 13-10 is the initial rms value in amperes of the alternating or symmetrical portion of the current.30) The use of the formulas in Table 13-10 results in values of maximum possible instantaneous magnetic force bet ween conductors.bus conductor design and applications TABLE 13-10 Maximum Instantaneous Electromagnetic Forces Between ac Bus Conductors Type of Fault F= 10. If the two currents flow in the same direction. on the point in the voltage wave at which the fault occurs and on the conduc tOr arrangement. Direct Current For direct current. for high capacity buses. the shape of the conductors and the distances between them are such that the shape factor can be considered as unity. A. NOTE: The shape correction factor is useful for adjusting the formula In cases where the dimensions of the The maximum force on conductors carrying alternating current depends. 'he 5llbuansien[ l'UI:tanee ofTOtatinl machinery IS used. straight. however. I""" span in inches (The value of minimum yield strength is com E=modulus of elastici1)'. lb /sq in. M=O.1' -384EI D-~- Maximum Deflection Continuous Beam Beam Fhed at Both Ends D=~ 384EI More Than 2 Spans 2 Spans wi' D= 185EI wl 2 \Il M=T:f Maximum Moment wl 2 wi'/.667 0..333 Totally Displaced Sine Current 1. inChes::!) ><:: fiber stress in Ib !sq in.370 I ~3 . of suppOrt.: Ratio of Average to Instantaneous 1.bus conductors TABLE 13-11 Components of Electromagnetic Force ac Bus Conductors-Relative Values I Curr.-m./12[5 Maximum Span ~ I '" I=V!{J 1_ . Symmetrical Sine Current Instantaneous . funy displaced short-circuit current has the same amplitude as the sym~ metrical current. inches''.t .er f1) _ 13-26 r .' j) See Tabli: 13~lO for values of maximurn instantaneous force. Current decrement neglected.107".p.1' ".500 2. The ac component of th(. lilMaximum moment and fiber Slress (or continuous beams occur at the second support (rOm each end. Note: Comparison of electromagnetic-force components for fully displaced and for symmetrieal short-CIrcuit currents. (ilMaximum moment and fiber stress for beams fixed at both ends occur . ~ Fiber Stress •['=85 [ = I2S ['= 8S ['_0. manly used. @lMaximum moment an'd fiber stress for simple beams occur at the center o( the span. W_8[S I I w= 12[S _ 8iS W..107w 1 ""'moment ()f inertia. D =defl:ecti9n in inches )II:::::: load In ib lin.1 is W=o:J. S Maximum'Load . of length (Lb~.107wl' " {1) I 1= . W::::::total uniform load in pounds (wI) f=maximum allowable fiber stress in Ibfsq in.667 0. IS . ! 0. lH <= bending moment in pound-inches S=section modulus.000 MalCimum Second Harmonie First Harmonic Direct CornponenlCD Elcctro~ magnetic Force® Maximum Force\!) 0. Wave-shape sinusoidal in both cases.072 i w/ 2 I€ .'oJ 0.333 i 0A verage value of total electromagnetic foree • . for two~wjTe short circuit.t the points.333 0. See Table 13~L) I€ Maximum deflection occurs in the end spans and is only slightly mQre than that (or a continuous: beam of 2 spans. TABLE 13-12 Deflection and Stress Formulas Bus Conductors Simple Beam 5". The following formula should be sufficiently 13·27 .:ircuit current. being more pronounced for flexible conductors where lateral movement is greater than for stiffer conductors (34). are given in Fig. Direct Current Buses Short circuit forces can be appreciable for large de bus systems. Torsional Forces Torsional forces are encountered in the end support of a bus. reso nant vibration can occur." acts as a fault to the rectifier transformer and to the de bus. the short. known as "backfire. The standard does not require the diode Or diode fuse to be designed to withstand a positive to negative fault. once in common use in the electro.. the force F can be further reduced.. Heating Caused by Short-circuit Currents The time during which a short . Longitudinal Forces Longitudinal forces may be encountered during short circuit for long span flexible conductors. Low·voltage Alternating Current Buses (31) Predictions of possible short-circuit currents for high voltage circuits.612 . 10-7 = 1)2' 10-7 d pounds per foot (Eq.6 as the current offset. needlessly high expenses for bus structures may be incurred. However. ANSI StandardS specify tbat the diode diode fuse coordination be capable of interrupting a diode failure if the fault is fed from its own rectifier transformer. the greater will be this force tending to pull the insulator sup ports together (34).. High speed breakers are used to limit current to mercury arc rectifiers and protect connected equipment. the effect of fault resistance and circuit reactance is such that the actual current resulting from a fault is usually much smaller than that calculated. The conductor may be analyzed as a uniformly loaded beam. 10-7 d (Eq.bus conductor design and applications systems have resonant frequencies. Low-voltage buses with short spans and relatively rigid supports may have natural frequencies that coincide with the natural frequency of the current.33). and (4) damping in the dynamic system. can be made fairly accurately. 13-13.4 (1.. The rates of current rise through a rectifier and its transformer windings for a large system could be as high as three to six million amperes per second. The stresses resulting therefrom could be several times greater than those calculated on the basis of the maximum force applied to a static system (32.61 2 . than the assumed value of 1. (See page 13-28). This type of rectifier failure.13-7) Values of k. Stresses Caused by Short-Circuit Currents The forces acting on a conductor that carries current are uniformly distributed along the length of the conductor. The Guide recognizes the presence of reactance in the system and sug gests using a value of 1.:ircuit current flows is usually so short tbat for all practical purposes it can be assumed that no heat loss occurs by convection and radia tion. If this difference is not recognized. The deflections of con· ductors. High-voltage Substations The IEEE "Guide for Design of Substation Rigid Bus Structures" (l) suggests that the interrupting capability of the substation equlpment be considered as the maximum symmetrical RMS short .6 V2 d 27.:hemical industry. in ac circuits operating at low voltages (440 volts or less). (2) the relation ship between the frequency of the current and the natural frequencies of the dynamic system (3) the duration and variation of the magnetic forces. the size of the conductor and the heat input.. The bus designer may wish to consult with the supplier of the rec tifier equipment regarding a comprehensive study of regulation curves and current transients during dc fault since a system analysis is quite complicated.:ircuit forces can be further reduced as follows: 27. the bus structure and support stands are capable of absorbing kinetic energy during a fault. ks is usually assumed to be unity for three-phase bus sup ports. The greater the lateral deflection of the bus during short-circuit. Depending on the type of support structures and their height. The temperature rise is then determined by only the specific heat of the metal. The classical general equation then becomes: F 5. However. Mercury arc rectifiers. insulators and structures under short·drcuit con ditions depend on (I) the magnetic forces. The probability of damage from a short-circuit in solid state rectifiers is much less than for mercury arc rectifiers. A knowledge ofthe short circuit characteristics of the power rectifier is essential for the design of the de bus. Because of flexibility. even though the power source is large.:ircuits bave occurred and can not be ignored. 13-6) If a system's maximum current offset is less.6. damaging short. were subject to failure of the rectifying action of the tube. In such cases. where arcs are of a sustained character. Short-circuit forces and elec tromagnetic vibration are usually not a major factor in design. Also. the maximum span may be calculated from the conventional formulas in Table 13-12 or the formulas for particular end conditions as shown in IEEE Guide. After the minimum size that will satisfy the current carrying requirements has bccn determined. in. lACS t ~ duration of fault (seconds) Tf ~ allowable final conductor temperature (C) Ti ~ conductor temperature at fault initiation (C) Mechanical Design A bus installation must be designed as a structure with enough stiffness and strength to support its own weight without excessive sag and to withstand those external forces...bus conductors 1... 0. electromagnetic vibration should receive careful study since buses with short spans and relatively rigid supports may have natural frequencies that coincide with the natural frequency or a harmonic of the current..0 . For aluminum conductors (40 to 64 percent lACS conduc tivity)... Tables 13-13 and 13-14 are useful in selecting pipe size conductors. T f ..6 o 5 10 15 20 2S 30 35 40 45 BUS HEIGHT (FT) Fig. The mechanical design of outdoor buses is covered in considerable detall in IEEE "Guide for Design of Substa tion Rigid Bus Structures" (!). weight of conductor. Vibration Electro-magnetic (Resonance) (32. for the same power.. ksfor various types of bus supports. (A) lattice and tubular aluminum. 0.. wind and ice loads.g. Increase in resistance with temperature rise has been taken into consideration. OJ. the mechanical 13·28 design will generally be determined by the total mechanical load. Here. ...7 0.9 k.....1 1... Low voltage buses..20 + (I5150/G»)Vz Tj .. A 0... ]3-13.. 13-8) where: ~ Is<: A + ~ the rms value of fault current (amperes) conductor cross-sectional area (sq. However.. have higher cur rents and generally smaller spacings.. which may act upon it. rigidity of sup ports. and wood pole.. ice. short-circuit forces are more likely to be a major factor in the mechanical design. The spans should be checked for suscep tability to electromagnetic and aeolian vibration. degree of damping and flexibility of the conductor ... e.. aeolian vibration should receive careful consideration for outdoor buses. (C) lattice steel.8 ~ t=::: ~ ..........) G ~ conductivity. damping material. (B) tubular and wide flange steel.20 (15150/G) (Eq.. and any concentrated loads.33) A bus conductor installation will have a frequency of vibration depending upon the span length... such as short circuits. ~~ ~ c " 0 .. Thus. accurate for practical (I).. .... (D) concrete... High voltage buses have relatively large spacing and usually relatively low currents. 06 2<l " ..40 I. ..03 0.83 4. .07 0.63 2. ...3i 0. 18. ..21 0.....01 0.58 3. 2 Zy. ..' . ... . .93 2..19 0..S3 2... .30 4.... . .. .48 0. • T' • '" 4.10 0.20 8...15 0..40 1. 2 2V.08 0.30 1.15 0. . .11 0.4 I ~ in.' .06 0.12 0.Q7 0. .41 1. -...02 4.. .46 2.. .10 0.91 1. ...37 3.87 2.43 0.15 0. In mebes (or a simple beam Wllh umfortnly dlStnbuted load. . -. .08 0.. ..04 0. .91 3...36 . ...12 0.44 2. . ..80 .. · .30 0.16 3.S7 1. .. ..06 2. . .34 0.25 ... ..69 II . .. -.89 3. . .01 0..39 0.15 ..16 0.01 0..51 9. . . . . .90 0.' ' .. .05 3. .03 0.76 0..% 3. .. . . .04 2. ..31 8... .". . 3.. • 'T' 6.10 1. .... ...89 3.....06 9.. . . .58 0. ~ y.4 Bare IV. V....09 0.14 8.61 0. .. .01 0. 3 3'h 4 5 6 V. ..03 0.10 L:l9 10. .18 0.86 L13 0....16 5.. . 9....03 1.34 2. .. .76 0.. .74 8. .27 0. 4 5 6 V. · . .. 18... .81 0. .. . ..41 0.21 1. .61 0.. . .52 0.. . ......21 0... .76 3. .79 . 41b Wind 1'4 IV.63 l...04 0. . .01 7. .09 0....24 1.09 0... . .11 . 3l .. ..32 4. ..06 13.17 6.31 0.34 . ~ I 11.. .30 4. .. .. ...56 0. .00 2.. -..50 0.67 1.. 3. ..21 " 5.17 0. .19 5.06 0.72 3.96 1. . '" ". .. .55 2.% 1. ..91 1. ... Ice. ...02 0..62 5. . .10 0...... . 14 .60 13.. . .58 1. .20 1.20 0.20 0.01 17..32 9. '" 6.. .. .% 0.05 . . .53 4... . . ..71 LOS 0. .. 76 0...08 3. .62 6. 15 0..97 0.12 0. .46 8. ..04 0.45 2. .49 8.23 0. ....64 1.. .. .19 11..47 0.' . .14 0.12 2. .19 0.93 1..65 1.75 7... .60 0. . 2 2V.38 8...01 0.... .56 11.75 . 2. ..30 0.97 3... .21 0. .46 0.... ... 15. ...... ..05 5.15 0. ' 20.12 0.. 3 3V.. .26 14. -. 2 "2'11 Plus Constant 3 3'h 4 5 6 Y. .22 2.92 4..42 3.. . . '.49 0. .28 . 12. .. .. . .81 8.14 .. . . . . ... •• IS 5.. ... . . .29 0..... .22 0. . .89 2.. .... .67 0..09 3..04 0. .37 1. .31 0.07 0.91 1.24 0. . .81 5. .47 5...19 0. " 9. 1.92 0. .. . . 15..38 1. ..... ..28 ·.. . ..22 0. ..45 0...35 0. .4 I in..20 . ...03 0. For beams fixed at both ends the dcftccuon will be one-fifth of Deftection til for any Other span Lt may be obtained from the relation: ~ -d (~) 13-29 ....02 0. . .47 1.49 13.. . Ice 1 11. .94 0.24 0..02 0.02 0.01 10. . . .. .45 1.85 1. .88 2.20 6.40 2..55 0.69 0.. . . 11... . ' • _T' ..83 051 0..37 . .69 3.88 0. . . .02 0.76 050 .49 .80 1...06 0.. 0 ••• 8:3i.. 14...bus conductor design and applications TABLE 13-13 Deflection Values Schedule 40 Aluminwn Pipe Conditions Nominal Pipe Sjzc in..53 1. ..10 0. . 4 5 6 .37 0.44 0. . '...10 0..72 5. 4. . .. 70 1.. .... . ' . . .65 1. . o. .26 4. · .03 4.. 4...42 9. . ..24 0.4 IV. . .....78 2. .17 1.63 0. .35 2. .15 5..76 7.52 o.. . ...88 0...95 1..68 0.. ..01 1... . .. .00 3...34 0.21 0.37 I.84 3..49 3...34 0. in. ..43 5. .n . . . . ..... · . .03 7. .39 1.....04 0. . . ..04 9. .. ...02 i N¢~: These are maxullum deflection values tbe values given. ..08 2.08 0..07 4.73 5...51 4. 74 1... Ice I 1'4 IY. 3 3V.12 0..34 •. ..10 2.92 .07 7. . .15 ....57 2.95 8. 10.59 0. . . 7..03 2.96 12.02 0..94 0..45 5... 4 5 6 'h...80 0. " (~I:) .47 11. ... '" .40 0. .40 ' ...65 2.09 .67 '" 0.56 l. ..13 0. .55 0. 15. .98 0.80 2.33 0.09 0.. . .... · 15. . .73 0. . 35 Deflection In InclK-s -... ..50 4.15 0. " .42 0...05 I'h. .81 0. in.69 7.01 0.97 3.49 0..80 10. . . .88 0.02 0... . . 2." 15. .25 2. . .34 3. .89 I. TItese atiC maJumvrt:i <k:ftct:tlon ¥alUC$ the values given. .04 1.." ..34 0. 3 3'h. 2 2'h. .89 3. . ...00 5.38 0.10 0..01 1. . .01 0. ... • '0' 23.08 0.20 8. .51 2. ' 17.. . . ..01 15..24 1. .67 3. " .08 2.98 0. . .50 l.. ... . . 23. .56 0.53 1. 15.34 13.... .09 13...93 6. . " 9.03 0. . ..09 0.44 0. . 78 1. -.95 1.-..96 4.08 12.36 4..46 ! I ..20 0...40 0..36 7. ....95 3..04 II!... .32 1.04 0.66 4...04 .11 ].60 7.. .. .01 I.. .50 0'.1.. . .42 4.46 0. IJz in.10 0. . . .09 " .34 0.01 0. . 22. .4O 14. . .....17 0.. 2..01 0.65 6... ... ...42 . .60 0.40 4.. 35 0.19 0...19 ' 6. •• • ..06 2. . ..84 .....06 0.64 3.15 I.97 0..." Bare I'h.16 0.. .49 0.46 i . .87 15.54 6." > .53 9.03 0. · . ' . .. to 0. .. " . ...47 7. . . ...46 0. ..54 2.76 0.67 15. ...28 0.45 0.30 10.49 0.. .82 1.97 . .33 5. .92 5. ....24 4.82 12. ... 'h. 2..89 3. ... ).51 0..19 0.. ..39 4.76 1.36 0..... . .46 2.77 0. be obtained from. -.07 0..01 0..14 7. 12. .93 5.88 .66 7.26 1. .21 . .52 11. . -. . .. .23 0.21 1. .24 3.07 0.97 1. .10 7..04 'h.65 17. .94 3.01 0.65 9.... 0.02 0.10 ..31 0.. . .. . . .25 3.. .16 0.. . Ice O. In i .81 0. .44 .86 2..10 7. .60 0.44 0. 4 5 6 2..86 0. ....96 0....... . (il for any other $plltl Lima).85 3.58 4. .. .99 0. . I .. .. 6..19 0..60 0..59 10.99 4. 21. .bus conducfors TABLE 13-14 Deflection Values Schedule 80 Aluminum Pipe Conditioos I Span in F«tt Nominal Pipe SI%C in..20 2. .02 0. 29 0. 6.44 6.. . .21 0.. ...04 3.47 0. S. .37 2.. . . . .. ...88 7.. 41b Wind II. Ice 0.66 1..25 0.64 13.. .21 225 .40 0... . .45 0.31 0. 8. ...76 4. 2 2'h... .17 5.46 4.. 1* 11)4 I'h.19 0.13 I.17 .. '.29 0. .43 1.19 0.28 0..01 9.... 3 3'h.61 . -.72 . . .25 0..16 0.11 2.. .. .. ...67 1.04 0.40 0..66 0.. . .33 0. · . .05 1. 8.. ..75 0. .. ..04 " 6.13 ..15 .. . 3.44 4. . . . .... .. . .26 .. 4 1 in. 1* ]I.60 9.10 0.12 3. 2 21'2 3 3'h.13 8... .24 2.06 2. 14.06 0.03 0. .80 2.13 3.79 0. .06 0.. .. . 10.01 U 1 2. . . ....85 Hi . . .15 0. . .17 0.75 •• 0 ..81 5.28 3. ' " 7. I NQIC.82 1.22 0. 1. . 35 0.72 Inthes for a :mnplrt beam With uniformly dlstnbvte4 load.05 0. .. ... .53 0. .12 0..31 0." 2 Plus Coostant 2'h. ..16 4. ...48 1.79 5.02 0.23 3.Jl 3... 'A I II!.98 1...10 I..".. . .47 1. .65 0. 21 8. .06 0.32 . .Q3 0. .42 2.04 0. .05 0.21 6. . ....38 . the relation: 41-4 13·30 ..27 0.26 0..01 'h.51 1.02 1. . 7.77 2.92 2.61 4. .98 3. . ...63 0..03 0. .14 0. .....99 4. 4.... ... ..43 '" . Ice.75 2.. . .... . i . . ..10 0.19 2.09 0.31 . .. For biCaffi$ flud at tmth end$ the deftectu:m Will be (me-fifth of Oeftoctk'('..... 4 5 6 5 6 1. . . . 0.... 3 3'h.54 1.72 0. " . . .25 0.OS i 6.39 1.. 000 1. (2} Since any bus system has some damping capacity.0 (EI) N 2n{L2) (Eq.3" 25' .zo 12' 0" 15' .0" 14' . Span LenQthillf2l 14' 6" 20' .500 795. (4) Lengths apply to both Schedule 40 and Schedule 80 tubular bus. Fatigue breaks have occurred. Tubular Bus Nominaf Pipe Size i Maximum Safe Span Lengtfl (ol 1 5' -0" 1 1/4 1 112 6'. in. The design fuctol'$.4 6x5 6x6 7x7 8x5 . Similar sizes of ACSR may be LlSed depending upon the damping character istics of the particular installation.9" 18' -6" 3 lI4 x 3 1/4 • 1/4 4x4xl/4 4. Here.800 266.000 1.4. Curves. 13-9) where: f = frequency in cycles per second L = span length in inches E = modulus of elasticity (107 for aluminum).0" (1) Lengths based on one loop of vibration.3" 15' 3" 19' -0" 19' . (2~ lengths can be increased approximately 20 percent with reasonable certainty there wrll be nO vibration.3" 29' . = -=. instaHa tion. 13-14 as a guide to avoid critical lengths for bars.800 397.3" Integral Web Channel Bus 4x4 6. based on Eq.590. The general formula (33) for "clamped-clamped" (rigid support) uniform beam vibration in the transverse or ben ding mode is as follows for single loop: f = 22.for conductor g 386 Electro-magnetic vibration has been observed chiefly on buses for electric furnaces. The span and depth in the plane of vi bration are the major factors in determining the frequency.9" 26' . and cost favor consideration of dampers. 13-9.3" 21' .000 (1) ACSR should have a multi-strand core.3/8 5x5x318 7' -0" 9' .4 W Ib/in. TABLE 13-16 Recommended Sizes of ACSR-to Be Inserted in TU bu lar Bus to Prevent Vibration Based on No Energy Absorption by Supports Nominal PJpe Size Inches 2 21/2 3 31/2 4 5 6 Recommended Min. the buses experience the equivalent of a short-circuit repeatedly in normal opera tion. in the plane of vibration.bus conductor design and applications TABLE 13-15 Maximum Vibration-Free Span Length .318 4112 x4 1/2.9" 16' . are shown in Fig.800 266.431. psi I = moment of inertia of conductor in plane of vibra tion.9" 21' .3" 2 2112 3 31/2 4 4 lI2 5 6 i Universal Angle Bus Conductor i UABCSize Maximum Safe Span Length!ll!2113l Maximum Safe IWCBS.0" 10' -9" 13' . (3) Ooes not apply for double angles in back-to-back configurations.0" 21' . Size of ACSR emil 266. 13-31 . rectangular aluminum bars clamped at each end.) <I> ~ <. CRITICAL THEORETICAL SPAN IS 29 IN...203.5 IN.. 13-14. SPAN LENGTHS THAT RESONATE AT 120 CYCLES SHOULD BE AVOIDEO ... i .. (BY TEST 27. SlMPLIFIEO FORMULA BASED ON GENERAL FORMULA FOR UNIFORM BEAMS "CLAMPEO-CLAMPEO" (33) 2.. w Ir l. Resonant frequencies .' 100 1000 CRITICAL lENGTH OF SPAN IN INCHES Fig. EXAMPLE: W' BAR...831 o L2 f • FREQUENCY IN CPS 0= BAR THICKNESS (INCHES) IN PLANE OF VIBRATION L = SPAN LENGTH IN INCHES NOTES: 1. • w ~ § k ('i ( • \ i \ 'it' ~ DEPTH DIMENSIONS IN PLANE OF VIBRATION f ...> §L 2' 10 BAR THICKNESS IN INCHES BAR THICKNESS IN INCHES 114 2 3/8 4 112 6 5/8 8 314 10 1 12 II AI1I1')')' \". pedestal-type insulators. A favored expansion con nection is the straddle-type (Fig. A short circuit normal ly could not excite a long span bus system with flexible sup ports in one of its natural frequencies. Furthermore. Aeolian Vibration Bus vibration is caused by a low steady wind blowing across the bus at approximately right angles to the span. Expansion Joints for Bus Conductors When the temperature of a bus conductor changes. wall thicknesses and alloys showed that internal damping of the conductor itself caused only minor devia tions from the theoretical formula. high voltage substations are generally designed with relatively long spans. supports and structures) have a marked degree of flexibility. which limits the run to about 100 ft. For reasons of clearance and economy.ing of the conductor. At section points either an expansion connector can be used. it is commOn practice to neglect any special consideration of expansion. 13-33 . Tubular Runs of considerable length require expansion jOints. dampers may be install ed in an existing station where vibration problems have oc curred. Such high-voltage "bus SYStems" (which in clude bus. Usually the max imum slip on such a support is about one inch. Rectangular BaTS (Eq. Expansion calculations are covered in detail in the lEE Guide (1) and are applicable to both in door and outdoor bus. as in a valley. because structural shapes have much greater lateral stiffness than flat bars. or the section is anchored at a central point of a long run. the force exerted on the in sulating supports may be higher than advisable. The possibility of For flat-bar construction where the continuous length of bus is not mOre than 50 to 75 ft. particularly if the tube terminates at both ends in electrical equipment that should not be highly stressed. particularly in the short lengths required for damping purposes. This shelter can be caused by trees around the station. and where the bus is sub ject to only normal variations in temperature. the natural frequencies of such high-voltage bus systems are normally much lower than the frequency of the current in the bus. 13-16) that is mounted On an insulator cap.bus condudor design and applications The width of the bar in the commonly used sizes has little effect on ly_y and on the natural frequency. A span that is "sheltered" from the wind will not be as prone to vibrate as an exposed span. there is a change in length due to thermal expansion. only that due to the fact of its length it has the potential to vibrate. Tests and experience show that all shapes of bus will vibrate provided the following conditions are present: (I) suitable winds are present. Support clamps are installed tight. otherwise. Winds causing vibration are low steady winds under 15 mph. There are too many variables involved to definitely state that a given span will vibrate. eddies will break off alternately from the top and bottom surfaces causing the bus to vibrateJn a vertical plane. (2) span lengths are long enough to vibrate and (3) support losses are less than input by wind. continuous buses should be provided with expan sion joints at intervals. The classical formula for frequency of vibration of round con ductors by wind is as follows: f = 3. each way from a mid-anchor point for usual temperature variation. with slip-supports on far distant insulators. Long. winds over 15 mph are generally too turbulent to in duce vibration. and relatively flexible structures. specially designed bus dampers have found increasing use for vibration protection. 13-10) where: f = aeolian vibration frequency in cps. In recent years. As a result. the most commonly used damping method was by inserting flexible cable in the bus. are not always available or practical to acquire.26V -- d vibration should be considered if the span lengths are greater than lengths listed in Table 13-15. The size and type of cable was determined by trial and error for each installation and there was little consistency (Table 13-16). and changes in length are not so easily abosrbed by lateral bo". Structural SluJpe Buses designed with structural shape conductors should be allowed freedom of longitudinal movement except at anchor points. Specific sizes of flexible conductor. This is necessary. Under certain low velocity wind conditions. V = wind velocity (miles per hour) d = conductor diameter (inches) Tests by Alcoa on tubular conductors of various diameters. The conductors were suspended on piano wires to eliminate damping effect of supports (Table 13·15). Until recently. and the small change in length of bus is absorbed by the lateral flexibility of the flat bars. equip ment in the station or by the location of the station. The bus will vibrate at its natural frequency provided that this frequen cy is within the range that can be excited by the wind. Standard supports are satisfactory for cables. Fixed Supports in Center Only TAP H SliDE t H SliDE -zil FIXED H H SliDE SliDE Fixed Supports at One End Only ~ FIXED TAP H SLIDE H H SLIDE SLIDE T H SLIDE Fixed Supports at Both Ends -s1 FIXED TAP H SliDE T? H EXPANSION SUPPORT SLIDE ~ FIXED Fixed Supports at Intermediate Points H SliDE 5! FIXED TAP T"i? EXPANSION SUPPORT 5! FIXED H SLIDE Bus Supports Bus supports should have a cantilever strength equal to or greater than the strength of the NEMA station post in sulators used with the supports. however. 13-15. Papst (36) conducted ex tensive tests that showed when the bus is used with spring mounted supports the reduction in stress is substantial. for a sustained short circuit. 13-15. If greater flexibility is required woven braid is suitable. Swinging suspension jor high-current bus. This swing principle also sometimes is employed for indoor bus in industrial plants where short-circuit forces otherwise would make it necessary to provide more supports (37). thick and for heavy. High strength aluminum alloy bodies with aluminum alloy bolts (never bronze) is the best combination of materials. However. makes the assembly somewhat bulky because of the large number of fme strands that may be needed. thereby reducing ten sion on the insulator. designed to accommodate bus expansion without placing undue stress on fixed supports or other components under various installation conditions (35).016 in.bus conductors Positioning Expansion Joints . 13-16. The gauge of aluminum sheets is 0. Fig. They generally consist of terminal lugs joined by flexible thin sheet of 1350 aluminum laminations or rope lay cable welded or compressed to the lugs at each end. flat bar and flexible tubes since the movement of the conductors largely absorbs suddenly developed forces of short-circuit currents. the bus swing stops at such a position that the balance of forces. Shock stress from short circuits is partly absorbed by the inertial swing of the bus and. including tension in the insuiator links. Typical expansion joints for different kinds of aluminum buses are illustrated in Fig. ANSI C119.Continuous Spons The following are some common arrangements for plac ing expansion and slide supports in continuous bus spans. 13·34 Clearances and Phase Spocings There are no industry standards for all aspects of clearances and phase spacings. Copper braids should not be used for outdoor ser vice on aluminum since copper salts from weathering of copper are corrosive to aluminum. channel· conductors.010 in. The springs may be mounted between the bus and its in sulator or between the insulator and its supporting struc ture. Slip-fit supports that have a rocker pin may be a problem for spans prone to aeolian vibration. to 0. Rigid bus swing-suspended from insulators is sometimes used where Short-circuit forces are high.3 lists industry standards for heights of supports. offsets the short circuit force. stiff buses. . The latter type. Fixed Supports at Center and Both Ends --2 FIXED TAP T'?S' EXPANSION SUPPORT ~ FIXED "2? EXPANSION SUPPORT ~ FIXED Expansion Joint Types There are many variations in the design of expansion joints. thicker laminations may be used. Support bumpers sometimes are provided in to which the bus enters at full swing. stiff tubes and flat bars mounted edgewise to the c1irection of force convey the total impact to the support. However. many are covered by National Electrical Code and the various Fig. Bolted Expansion Coupler Connector --1). 13-16._-" b. Welded ExpansioD Connectors for IWCB Fig.b/. Welded Expansion Terminal Connector e. Welded Expansion Coupler Connector c. 13·35 . Typical expansion connectors. Welded ExpansioD Support - d. _.ls cond/.lctor design and applications a. (2). Minimum Spacing Between Bottom of Enclosure and Bus Bars. Bolting and clamping are also used where welding equipment and trained welders are not available. 'For spacing between live parn and doors of cabinets. Resistance measurements of completed connections reveal the degree to which these bridges are effective in providing a low resistance path (38). Their Supports.:: 25. nominal ____ NNot _o_t_o_ve_r_2_5_0_v_o_ln_. If tbe increase in joint resistance causes a significant increase in temperature tbe deterioration may be cumulative until the circuit opens or high temperature provides more conducting areas at the in . The installing force on a connection disrupts the natural oxide film on the contact surface. 13·36 The natural oxide films on both copper and aluminum.c15nsists of innumerable microscopic hills and valleys.4 millimeters. nominal._n_o_m_i_n_a_I___ 12_1_/2 __ in_c_h______-l________3_1_4_i_nc_h _h_____ over 600 volts.. are poor electrical conductors. or welded bus bar connections provide equally satisfactory service. They must be ruptured or otherwise penetrated to bring about the required conducting path. Jointing and Connecting Properly designed bolted. or Other Obstructions (Inches) (NEC Sect. clamp-fitted. allowing metal·to-metal contact for low contact resistance. the initial con tact of two mating surfaces occurs at only three points. The surface of a piece of metal . 384-1Q) Conductor Inches tnsulated bus bars. and (3). When increasing pressure is applied. Nature of Contact Interface There are similarities in the contact interfaces between any two conductors. Theoretically. Photomicrographs of contact surfaces have shown how metal is extruded into the fissures in the oxide surface dur ing interfacial collapse to provide the bridges by which cur rent can traverse the interface.no matter how well polished . The quality of con ducting path across the contact interface must approach that of the continuous conductor if significant resistance concentrations are to be avoided. their supports. see Section 373-11(0) (1).l:_________ inches 1 inch _ _______L-____l_f_2_i_nc 1 inch _ For SI units: one inch . Welding is generally preferred for permanent connections and bolting is used where connections may be periodically broken. Contact resistance may be sensitive to subsequent micro-movement from creep or differentia! thermal expansion. 13-18 and 13-19). the initial points are broken down and multiple points of contact are establish ed.bus conductors TABLE 13-17 Minimum Spacing Between Bare Metal Parts (NEC Table 384-26) Opposite Polarity Where Mounted On the Same Surface Opposite Polarity Where Held Free in Air Live Parts* to Grouod 3/4 inch 1/2 inch 1/2 inch Not over 125 volts. particularly aluminum. or other obstructions Non-insulated bus bars 6 (2Q3 mm) 10 (254 mm) manufacturers have their own standards (Tables 13-17. 0 115.0 Phase-to-Phase Indoors 46. (1) The values given are the minimum clearance for rigid parts and bare conductors under favorable service conditions.0 7 7 12 12 15 15 18 18 21 21 31 53 53 63 63 72 72 3. Constriction Resistance The distribution of de current in a long thin rod is uniform. Al-Cu bolted interfaces between flat bus may ex hibit this characteristic (39). the latter is by far the most important.0 4.0 10. i 89 105 17 17 25 42 42 50 50 58 58 71 83 For 81 units: one inch =. 2. and (2) film resistance caused by random areas of less perfect contact. (2) ANSI C 37.0 34.0 .0 Minimum Clearance of live Parts in Inches Impulse Withstand.4 23.5 12} 7.5 Ph3se-to-Ground Outdoors Indoors Outdoors Indoors Outdoors 60 75 95 110 125 150 200 95 95 110 110 150 150 200 200 250 250 350 550 550 650 650 750 750 900 1050 4.5 12.46 lists 6 in.16 7.4 millimeters. kV I .5 13.4-4. or wherever space limitations permit.0 6 6 7 7 10 10 13 13 69.5 9.bus conductor design and applications TABLE 13-18 Minimum Clearance of Live Parts(1) (NEG Table 710-33) I Nominal Voltage Rating kV ! .25.0 6. for 8. 25 kV. Although the contact resistance consists of film resistance in parallel with the constriction resistance.L. They shall be increased for conductor movement or under unfavorable service conditions. and tested in accordance with accepted national standards.0 138. These values shall not appty to interior portions or exterior terminals of equipment designed.2 13.5 5. manufactured.5 7. The selection of the associated impulse withstand voltage for a particular system voltage is determined by the characteristics of the surge protective equipment.5 9. The resistance of such rod can be calculated by 13-37 . Contact resistance of two metallic surfaces appears to consist of two parts: (I) the constriction resistance caused by non-uniform flow of current in the body of the conduc tors as the result of the constrictive nature of the small metal extrusion contacts at points of oxide fracture. B.0 I 161. 230.8 14. terface.I.0 5.5 18. Transmission snbsratiofl Sub committee:.G9) S( .26) 105(2.tors _Inch~~_~ 30 45 7( 12{ Hi( 18( ZI( 31( Ill) SO 100 145 230 275 315 G3{ 1.57) 16(4.64). I1V Recommended 159 144(3.3)"1 ~ Inches Meters T-. page 1924) which is a report of lhe.05) liO( 1.66) 13(3. No. Vertical nrk.80) 83(2. see fhe NFMA Standard. HQrizontal Disc. Crest kV 11(3.Q7) 50(1.arance Between Over~ head Conductor and Ground wit~t<mz! rot Penonal Safety IS( AG} 24( .10) 84 104(2.18) .(4. Publication for High voltage insulators. NEMA $10 SG 6) r~ r---.49) Cle. Recommended phase Spacing Rated Withstand Voltage I ImpUlse 1>0 Hz !<V rms I n Rated 1.91) 9(2.Basic Parameters (Table 1.83) 89(2.~82 I ! insulalot data.5.93) 7(.19) 47 52-1/2(1.66)0:'.6Z} S~ S.79) 53( 1.05) 48(1.44) $( .19) 10 (.88) r- Minimum Feet (M cters) 300{'1.5 121 145 109 242 242 362 362 550 550 800 _kV Crest 95 110 150 200 250 351) 550 GSO 150 900 1050 1060 1300 1551) 1800 2050 Wet ErJergizoo 10 Second.47) 1 IG8(4.13) 25( .22) 10( .4) 120(3.18) 36( ..Bu·s Supper1s.5 25~3 38.:': i I I i I I (2.(1) 30( .9G) 192(4. Gr(lund clearance for voltages 3G2 kV and ab(we are selected on the premise that at tllis level.30) 15 18 '29 (. No.6G) 58(1. Volt Wave No.27) 1b(4.25) 13( .30} .83) lQ8(2..88} 71(1.35) 156(3. :.74) 132(3.'16) 3C( . system.38) {AS} {.GO) 72{ 1.- • r w w t 00 S TABLE 13-19 Ol Electrical Clearances Outdoor Substations .52) 84(2.43) 84(2.35) 1M(:l:. 90-1/2(2-)lO) 106 (2.(1.22) 10(3.1l Ri!~jdly Suppou€(] 1-197:~. IG(. Vases Rccommcndetll Minimum 7-112( .52) 72(1.96) 192(4.7(.74) (1.11) 216(5. For additional switching surge vailies refer to the above noted paper.33) • HOC 1.35) 385 455 455 525 620 Cenrer to Center Minimum M elat-to~M ell! 1 Dtst3nce Betwee.G7) 119(3.0 48.(.15) 7 ( .'if') 30( .us Line iMa~..s.05) 10 (~i.88) 18(5.49) 240(6.83) 17( .02) i -- Hom Gap Switch /{ (.38) AG) .49) R08 898 CLI" .ptmz!s on switching surge levels of tile.25 2 3 4 5 6 1 8 9 10 n 12 13 14 15 16 15.53) .96) 14(4.13) 96(2A4} lQ8(2/14) 132(3.35) 12(3. condu(.91) 41:)(1.found Clearance rnches(Metets.2'1) 192{4. selection of the insulation de.91) 3S( .SfJ} (l.22) CO (1.88) 21G (5.25) 12 (.05) 42(1.3 72.52) 72(1. JxpuJdon Type.. The values wete selected from Table 1 of IEEE Transaction paper T-l?-J31-6 (Vol.) 8(2.:l3} G1-1/?.2'2)*! 710 830 j Rigid Conductors lZ4(3.91) 48(1.2 x 5O. Switches 30( . I kV tms 8.15)'~ n! ~--For . Pub.27) 144(~i. .74) 10(3. Switch~ Power Fuses Break Non-expuhiofl Type Disc. Ja. - . Thus with a large number of small paths through a surface film. W. --- --- ---1--~}1 --1--------1--- ~ 1". 13·39 .l? 2Jo ~Ia. The distortion of the lines of current flow results in an increase in resistance. the self-resistance term in the constriction resistance at asperities becomes very small. B.L. the total resistance may be almost as low as with no film. Vol. --- --- r----\~ iY-.. where <l is the resistivity. the current flow is no longer uniform. JJ.S • • / / V / V "" V V 0 0 . R = (lLIA.bus conductor design and applications Source: XOOW£NHOtJEN..sta~~The ComrilHtJitm f1{ Non-Viii/arm Vol 1Q. i I. 10. AlEE Trans..CK. called "constriction resistance... '" Greenwood (40) showed mathematically that..." ~/ .. --- --- '--- -- \ I Fig.... 21 Fig.)(. (Bottom) Spreading resistance ojflat strips. Soutt::e: Km!w£KHOUEN. 1951..tnd s.~!' ...." of Hot IItips. La ~ .' f I ". u f- " • . COfflIWt RHl. T. AlEE Trans J --- --- r-- \ -I -..-- ~ I MtawrH MlItfi (okItIattcl 'taIu1S V • II . (Top) Equipotential and flow lines on flat strip with constrictions. 51I-Spreadmg re. L is the length and A the cross-sectional area. CCltltKt Rt!si5uura-Thr ContrlbutitPt of NOIf-Uh/fomt Cwnmt Flaw. and SACX£'lT. 13-17. T.. 13-17) is interposed in such rod or strip. 1951 CUIW" Flow. a . W.IETI.isto. W.. w. with a large number of small contacts. When a constriction (Fig. The area and distribu tion of the conducting spots are generally determined by the magnitude of the clamping force and the manner in which it is applied. (2) contact pressure....bus conductors \ 'I'1\ - - - wrenn!l pr_iltt Dec:. Contact Resistance-Clamping Force The initial contact resistance in clean contacts depends on (I) the resistivity of the contact members.~ .. Film Resistance The natural oxide film... calculated on the basis of total area of overlap. switchgear..ere ifI[h Fig. page 13-41). i\.. According to Molt's application of quantum mechanics (42). in. (3) contact surface preparation. -- " -- 0. and means of assembly-that minimize differential thermal expan sion. and (2) the area and distribution of the conducting spots in the inter face between the contact members. 1. relaxation. (4) characteristics of the metals involved (both mechanical and relative thermal expansion)... Contact Surface Area (Overlap) Melsom and Booth (43) in their extensive work in 1922 presented practical recommendations regarding size of overlap. where joints are electro-plated and tested. and other stress changes. Ciampi. in aira may be said to have a thickness ranging from 10 to lOOA (one angstrom unit = 1 x 1O-7mm). is permissible (UL 857). sulfides and others. and use of petroleum jelly as a valuable guide for both aluminum and copper conduc tors.r::. contact surfaces. surface preparation. (6) sealing the joint against possible oxidizing or corrosive agents. such as oxides. a current density of 200 amp. conduction through very thin films depends upon the fact that electrons in the metal can penetrate a distance of a few angstrom units into an insulating layer without receiv ing energy of excitation. For factory fabricated apparatus.' . Thick films in the order of lOA may be regarded as barrier films. can as a rule be regard ed as insulating..... (5) jOinting hardware. sq. For example. . creep. (7) operating temperature and (8) possible hot 13·40 spots due to short-circuit currents. '" '" . .. 13-18.DOD . such as busways. Design Factors Of Bolted And Clamped Joints Research on the nature of the contact interface points out the importance of those combination of connection elements-contact members. and isolated phase bus. 13-18 shows the relative change of resistance with increasing and decreasing . Mean contact resistance of various clamping forces in stacks of !4" by I" 1350-H12 bus bar with contact surfaces abraded through an electrical joint compound. Thin films pass electric current practically without perceptible resistance (41).. when the overlap equals the width of the bar for field fabricated bus.'" I'" Pfonurtl_~ds pet \. Therefore. ". considera tion should be given to: (J) contact area.eaWlIJ pre5$UUI \ \. Thick films (multimolecular) without fissures. in the design of bolted connections. .. i"' r.. F' \I8D . Fig. Experience has shown that good performance is obtain ed if the current density for bare contact surface is in the order of 90 to 100 amperes per square inch. (See contact surface preporation. >.. Therefore. where plated connections are used. (4) use of thick flat washers in conjunc tion with steel bolts designed to operate as elastic members. or a combination. An area of more concern is the problem of bolting nonplated aluminum to silver or tin plated surfaces. Therefore. (2) Bolt Size-For a given thickness of material. the joint resistance is definitely decreased. Plating is re quired where plug-in contacts are used.against nonplated aluminum. have given satisfac tory performance under normal operating conditions. the problem of adequate clamp ing force for a joint of satisfactorily low initial resistance can be simplified by considering the clamping force as uniformly distributed over the apparent contact area. the joint resistance for bolt sizes between 3/8 in.2 mil has been considered the limit of plating thickness below which special precautions are not required in properly designed connections to non plated AI. If One has a thick-plate silver or tin contact member that must be electrically connected to nonplated aluminum by bolting.45) show that heavier silver and tin plated surfaces had poor capability for interfacial fillty while nickel was quite good. The chemical ac tion not only reduces the thickness of the film. plating thickness is a factor in determining whether Or not fixity will be maintained. resistance increases have been experienc ed in certain connections. data indicate that interfacial shear strain-strain resulting from the shear component of contact force-is by far the more important cause (38). the additional increase in joint efficiency is 13-41 . Plating thicknesses in excess of 0. generally in excess of 100°C. rule-of-thumb limits of unit pressure can be ap plied to serve as guides when making joims. (3) Number of Bolts-As the number of bolts is increas ed. Contact Surface Preparation A flat. Reasonably constant clamping force can be maintained with anyone. however. the possibility of trouble can be reduced by inter posing a bi-metal wafer. Higher average clamping pressures may be used for 6101 and other strong alloy con ductors. but also im parts lubricity which assists in the seating of the contact members_ Plated bus is normally used in industrial equipment to avoid the necessity of field joint preparation. UL specifications permit 15°C higher temperature rating. When five Or six bolts are used. 0.bus conductor design and applications pressure. overlap and bolting remain the same. Where operating temperatures have been high. Bond's tests (44. Such increases are greatest where the AI is soft and the Al contact surface is not severely deformed_ Although these increases are frequently at tributed to a lack of spring follow-up in the fastening system. the resistance is more. installed with joint com pound in accordance with instructions. Silver plating was once generally specific but tin plating has largely taken its place. the joints are heated. the different thicknesses of material commonly used do not appreciably affect the j oint efficiency. diameter may be lower for the larger bolts. hence increased ampacity. The work of Shand and Valentine (46) on the effects resulting from the use of different quantities and sizes of bolts and of different thicknesses of bars disclosed some interesting facts: (I) Thickness of Bar-Provided that surface prepara tion. The most effective treatment is to abrade the aluminum to disrupt the oxide film and immediately coat with an electrical joint com pound containing an active chemical that attacks and disperses the oxide fllm on the aluminum. unplated. One solution is to inter pose a bi-metal wafer (AI-Cu) to establish AI-AI and Cu Cu contact surfaces. and 3/4 in. stable. For practical purposes. In this way. With harder AI or thinner plating. Bolts-Size and Number The size and number of bolts in electric joints are of par ticular importance. aluminum contact surface for a bolted connection requires some treatment prior to assembly to reduce the contact surface resistance. of the following methods: (1) use of aluminum alloy bolts. Bolted Joints and Jointing Hardware When the electric load on a bus increases in the course of normal load cycles. A practical design range for average clamping pressures is 800 to 1200 psi for 1350 alloy conductors. Characteristics of Dissimilar Metal Interfaces Different contact materials have different capabilities for malntaining interfacial fixity-lack of relative movement. (3) use of clamps with built-in elasticity. where joint surface preparation and the number of bolts remaln constant. Another method is to plate the aluminum contact surface. since the bolting pressure must be ade quate to establish a high initial joint efficiency without subjecting the bolts to stresses beyond their yield strengths. Bolted AI-Cu connections. (2) use of Belleville spring washers with quality steel bolts. Joint effi ciency increases most sharply as the number of bolts is in creased from one to four.2 mil have shown significant resistance increases in joints with nonplated soft AI. The connection would then be in stalled in accordance with standard recommendations. the aluminum tends to expand more than the steel bolts and looseness of the joint may result for certain conditions. With increased plating thickness the creep and expan sion properties of the plated contact surface become more like those of the plating material than the substrate. or an allowable temperature rise of 55°C above 30°C ambient. 1. Bar Width. Inche. ' coated. 1 2 tl+ + T "'I II++-t 0 -s_T ASTM-A325 ANSI 818·2 heavy finished hexagon \ nut and bolt.. • 4 E I-. 8 8' 2 2 2 1 I 1 2 . I 5/8 i Bolts Aluminum Steel -0/.bus conductors TABLE 13-20 Bolting Schedule for Field Erected Buses Inch•• Arrangement A B 2 2 2 1 1 1/2 2 3 3 3 3 1 1 1/2 2 3 4 4 4 2 3 4 5 5 5 5 2 3 4 5 6 6 6 6 6 3 4 5 6 i 8 i 8 .1. 4 5 6 3/8 3/8 3/8 5/16 5/16 5/16 1 1/2 2 2 2 4 3/8 318 3/8 3/8 5/16 3/8 3/8 3/8 314 1 1 1/2 2 2 4 4 1/2 3/8 1/2 1/2 318 1/2 3/4 1 1 114 1 112 2 21/2 2 4 4 4 1/2 3/8 112 1/2 1/2 3/8 1/2 1/2 314 1 1 1/4 1 112 1 112 2 2 4 4 112 1/2 112 518 5/8 1/2 3/8 112 112 518 1/2 1/2 518 1/2 1/2 5/8 5/8 1/2 1/2 1/2 1 1 1 1 1 1 2 3/4 3/4 314 314 1 1/2 1 1/2 1 112 1 1/2 3/4 1 2 1 1 1 2 2 2 i 1 2 2 2 1 1/4 1 1/4 1 1/4 1 1/4 2 112 2 112 2112 21/2 1 1/2 I 112 1 1/2 1 1/2 1 1/2 3 3 I I 2 2 2 2 3 1 1/4 I 1/4 1 1/4 1 1/4 i I 2 . . of Bolts Bolt Spacing. Steel D i I 3 3 4 8 i I 3 3 3 2 3/4 2 3/4 23/4 23/4 I F ! ! I ! ...''''1.. 1 1 1/4 1 1/2 1 1/4 2112 3 i I 2 2 1/2 . 3 23/4 Tangent or Right-Angle Joint. I Locknut Of Patrmt. No~Ox-kI steet bott.1--. + +t + + 1+ + 3 '" + -! _s-T 13-42 Aluminum flat washom. No. Bolt Size Aluminum E C .-j E r-. . 4 ! 4 6 6 6 9 . if S8C"riCe conditions nlIquire* . in root area. o . Aluminum alloy bolts. and under the bolt head : The torque necessary to produce these bolt loadings is. The brighlareas around Ihe boll holes are Ihe only areas 0/ intimale coniaci when bars are /aslened wilh slandard bolt and /1. 13-19. Sleel Bolls and Belleville Spring Washers (4 7) Another method of avoiding a potential problem as a result of differential expansion . the greatest single concern should be relative movement at the film -coated surface of the aluminum. Since the compressive stress in a bolted joint is con centrated under the head and nut of the boIt . the contact resistance is increased. it should be left in flattened position and the normal relax ation of the metals will restore some crown to the washer (See Chapter II). alloy bolt s liS-inch larger than the equivalent steel bolts are sometimes used. or permanent deformation (creep. Most of the cur . Many factors are relevant to the performance of bolted overlap bus joints involving aluminum and other metals.'sulting stresses in shank.---'-' ·0 rent transfer occurs in the area of high pressure under the bolt heads (Fig . wide-series flat washers under the bolt heads.1 sleel washers. and Table 13-22 lists the recommended loadings of the usual sizes of aluminum 2024-T4 bolt s for bu s connec Fig. etc . Bolts.. are somewhat lower in torsional strength than mild steel. Whether this movement is caused by differential thermal expan sion . and the nut should be tightened until the spring washer is in a completely flattened posi tion. 13·19). therefore. serves to distribute the high contact pressures over a larger area. However. therefore. while the intermediate ones have no practical influence on the current distribution over the can · tact. if it shears the current-<:arrying spots by which the current traverses the inlerface. 13-20. tions together with the n. Aluminum alloy bolts are non-magnetic and . is offered as a guide for heavy-duty service. Hence. therefore loosening of the joint because of temperature cycling will never result from thermal expan sion. . elastic deformation. also shown. assuming suitable lubrication on threads. Sleel Bolts and Pressure Plales Stainless steel pressure plates have been used successful 1)-43 . . Donati's work (62) shows that. Clamping Pressure The relation between tightening torque and clamping pressure in a bolted joint is greatly dependent on the finish and lubrication of the threads and other bearing surfaces. The series of designs of boIted joints for bars. Aluminum alloy 2024-T4 bolts have the tensile strength of mild steel. of liltle electrical value to use the in termediate bolts. nuts and Belleville washers.). The large r bearing area is helpful in reducing stress concentrations and in inc reasing elTective contact area. not s ubject to heating due to hysteresi s losses in ac field s. The use of thick. the current will traverse the c Oniac l surface only in (he vicinity of the two outer boIts. Table 13-21 shows dimensions of he a vy-series aluminum bolts. the same clamping force can be achieved with the same size bolt. The average relation between tightening torque and clamp ing forces for specified conditions is shown in Fig.Torque vs. shown in Table 13-20. In the absence of specific instructions to the contrary. flat washers are recommended to increase the bearing area . Aluminum Alloy Bolts Aluminum bolts have the same thermal expansion as the aluminum bus.bus condudor design and applications small.of bolts and conductors is the use of Belleville washers under the nut of a steel bolt. for bolted joints using multiple through bolts inline with the axis of the bus . It is. The flat washer should be larger than the spring washer. To offset the lower torsional strength. under bolt and nut bearing surfaces. Experience over many years in North America and France has shown that very sinisfactory results can be obtained by using Belleville spring washers : A flat washer should be us ed under the Belleville. however. are from AlEE Conference Paper CP-59~930 which exhaustively analyzes tbe torque-load relationsbips of aluminum and steel bolts. * Product of Dearborn Chemical Co. Steel Bolts and Standard Flat Washers ALUMINUM BOLTS BEST RESULTS AVO.010 1.-/3 bolts oj various materials and lubrication. but the thin oil film that is on the bolts when packaged is retained.) National Coarse Thread (Dimensions in inches: F and G are maximum. H is nominal) A-ANSI B18.. Head ' Head 13 11 10 -- '/2 5/. Dimensions of Heavy-Series Aluminum Bolts 2024-T4 Aluminum Alloy. It. ' .STEEL BOLTS WITH FILM LUBRICATION AS RECEIVED 1 1 lDO 20D ! 30D 1 1 !D lD 400 LB-IN . 1. 1. • UM1NlSHfD HeAD o F G I: I:· J nmlThreads._ OF FOUR TESTS The higher yield strength and better creep characteristics of 6101 alloy make it easier to obtain stable electric joints with this alloy than with aluminum 1350. and similar curves for %-in. andjresh lubrication). straight shank.2-1 heavy-series semi-finished anodized 2024-T4 aluminum bolts with overall No-Ox-Jd XX" or equal. inhibitor lubrication under favorable Con ditions (no side friction in bolt hole. 13·44 . 17l.C.227 1.z 51a 13/ 32 '/z '9/. Tests and field experience show that as a rule-of-thumb Belleville spring washers are not necessary to the satisfactory performance of bolted overlap joints secured with quality steel fasteners if the tensile strength of the aluminum bus is in excess of 20 ksi and provided the contact surfaces have been properly prepared..: Diam. Nominal ACI'OiS Across iFinishediFinished Pitch I Diam. It is assumed that the inhibitor lubricant is as applied before the bolt is sealed in a plastic bag.bus conductors Iy for bolted joints. (N. Note: Curves A and B. and the quality of the lubricant and its application may not be up to full standards. e-Industry curve long used jor unlubricated sleel bolts. If the bolts have rolled threads. Per In. Torque-clamping jorce jor 'A-in. 10. '/. the shank diameter D erosely equals pitch diameter J. aluminum bolts.. These plates. accurate threading. The corrosion resistance of these unanodized nuts is compatible with that of anodized 2024-T4 bolts. This curve also is suitable for heavy-series bolts under similar conditions. Bolts should be anodized with adequate thick~ ness and seal to impart suitable corrosion resistance for the application. /3-20. Dimensions of flat washers are shown in Table 6DOO 13-23.443 'I. 1 i 1. It is recommended that unanodized nuts of 6061-TS or 62S2~T9 alloy be used. drHled to conform to the bolting layout. Chicago. ~"--l I t~ B-ANSI regular-series aluminum bolt of same specifica tions as above under average conditions.4!500 0 5660 1 . Ill. Flats Corners. '0. expand the pressure area around the bolts. It is the basis jor the loadings and stresses shown in Table 13-13.'- 3D TABLE 13-21 LB~FT TORQUE Fig.1 I.. Note: The unthreaded shank length and overal! length of the bolt should be selected so that there is little excess of thread length above nut thick¥ ness:. 7/. and %Min.6850 . 800 39.25 1..4"_10 0. Torque and stress under average conditions-with stresses suitable for optimum creep conditions.2256 0.. in sq. the thiekness 01 a washer should be increased with increased washer diameter.3/4 0.313 .083 . larger than bolt diameter. of A/l..) If bolt has rolled threads the shank area is reduced. but for heavy-series bolt. "Extra-thick washers of Heavy Or Extra-Heavy series of aluminum often are available on special order.165 1) 11 0. ::l/s. not only because of their conductivi ty.273 0..637 Nominal Bolt Size Quality Steel Bolts Bolts.7854 Sire. it is desirable to use bolts that have a known elastic proof load.148 2-'1.3/ 4 0.' 14 0.. in.462 0.800 13.000 80lt Size Medium Heavy Extra Thick Extra Heavy (Aluminum 0I'I1y) Stress in thread area.307 0.1 stress tronsfer thc:rt is ehoroeteristic of ANSI thre-qdt. if "medium" wastlet'5 are used. 0. unless purchased to a specification.)*** Load on boll. psi ----• Fn aocotdan<6 with ANSI ...400 "Medium" washers are specified in NEMA SG1. Special Clamps Fairly uniform pressure may be obtained over a wide range of operating temperatures by the use of special clamps. 1/4 0. Standord~ the nilrl' stress area is slightly Iorger than the oreo of Q circle of Sllme diol'lUtter en thread root. sq. 0.0. Thk.lseJ# 0 report of Working Group 57.109 1.3 Is 0.or Heavy-Series Aluminum Bolts under Recommended Application Conditions. psi 28. Ill-In. Thk..000 39.0.finish. reeommends 25 1O-ft 01.in. thereby ollow ing for the slight spit". 'which is same as NEMA Std.UJIinum in SuJuratjon Ih.134 1.318 0. The in hibitor lubricant is assumed 10 be No-Ox-Id XX. Aluminum·To-Copper Connection Aluminum and copper are both ideally suited for use as electrical conductors. torque for 1/2-13 HC boht.. Thickness of Flat Washen-Inches Torque.109 1.4. Note: As bolt holes usually are 1/16 in.. Grade BD) are recom mended for thick packs of bars where it is customary to use fewer bolts and larger Belleville washers. psi** Stress under heavy-series head. Recommended for con· neeting aluminum bus bars with either regular or heavy series TABLE 13-23 aluminum boilS. 0..0625)' I The rim effect of washers applied to aluminum that is not stressed above its elastic limit Is sometimes taken into account. but also because both metals have an excellent inherent resistance to atmospheric weathering. $'''''' .148 2 0.083 0. Outside Diameter &. 0."-11 3.412 0. 13·45 .umed that the nuts are semi·flnished and of same or a compatible aluminum alloy.'65 . Assembly of bus using clamp joints is relatively simple because pre·drilling and aligning of bolt holes is not required.500 17.100 28.0.442 Area under regular bolt head and nut (semi-finished)" 0. a . Because these two metals are almost exclusively used as electrical conductors.' -IS. Generally. 0. Thk.. bV assuming that the effective bearing area under the washer is the same as that of an area the diameter of which equals the outside diameter of the washer pius twice the washer thickness:. IEEE poper 63·280. and that nut ar.300 19.600 29.100 20. Ib·ff (approx..400 33. designed so that the convex faces will be parallel when the bolts are drawn down to the rated capacity of the clamp. Same.. Net stress area under thread* ANSI Std.. 1 l. 3/4. OM 40 Ib ft for 5/8-11 He bohs.109 1.shank. min.1O for joining power connectors to flat contact surla¢e'S.in . U.1~ Substotion Committee. CC1 Table 4-2'fOf aluminum bolts that fasten connectors to flat conducting swi'aces. 0. +0.."Is 0.bus conductor design and applications TABLE 13-22 Initial Tightening Torque and Probable Resulting Stresses in New Inhibitor-Lubricated 2024-T 4 UNC Anodized Regular.o is same en heed oteo. such as those meeting ASTM A 325. in. under regUlar heod.0.500 8.0.. larger in diameter than the nominal bolt size.083 'Is 0. Ib (proboble) 5. A. sq. (It i.200 31.134 2-3/s 0. is 0. and the stress in the shonk may be as much as 25% greater than the stresses listed as in the shank.164 0. l-!t"·13 %. High-strength bolts such as SAE Grades 7 or 8 (ASTM A 354. psi 38. Areas: under head and are based on hole 1/16·in.: 0. the bearing area of the washer.375 Sis-in. or equal.. 0. in. 10. .3/4 0.3340 Shonk area. Thk.1416 0. Power Division. 0.under bolt heads in this tuble ore computed an the basis of minimum widtb across Rat (If Q sem. aod larger outside diameters similarly are usually obtainable.000 Stress in .cI boJt. vary widely in mechanical properties. have given satisfactory service. For bus bar joints..500 32. The "curved back" clamp.196 0. Welded connections are an ideal solution to both problems. and manipulation of the torch are described in specialized publications of aluminum producers and welding equip ment manufacturers. When the bead is not ground off. there is an essentially homogeneous union that gives a per manent stable connection. aluminum is anodic to copper. the criterion of "mechanically satisfactory" means "electrically satisfac tory" is applicable.0 ksi 4043 4043 4043 ! 4. This can be observ ed from Fig. If possible.bus conductors connections between the two metals have to be made fre quently. It must be remembered. 13-17.0 ksi 7. There are bus connections where it is important to insure a resistance ratio of unity with the conductor itself. when properly made with well designed fittings of good quality. The value for 6101-T6 is about the Same as for 6063-T6. however alloy 4043 is easier and faster to use. As a conse quence. With welded connections. For protection of instaUations in en vironments that are known or expected to have severe galvanic action. They are covered in Chapter 2. The accumulation of films or corrosion products on the contact surfaces may adversely affect the electrical resistance of the joint. Both GTAW and GMAW processes employ inen gas shielding (argon. Such connections can be made by foDowing pro cedures outlined in The American Welding Society Hand book "Welding Aluminum".50) give considerable data on design features and test information.4 k5i 25. the average yield strength in the TABLE 13-24 Typical Alloy Strength Values As Welded . Some of the earlier papers (48. protec tive grease-type compounds are effective and suitable for controlling corrosion and maintaining low resistance in direct aluminum-to-copper electric connections. and the gas metal-arc welding m~thod (GMAW) in which the filler wire is power-fed con tinuously through the torch. Such compounds are also used to minimize the formation of oxide films on the contact surfaces. For outdoor substation applications.0 k5i 8. Average strength values are shown in Table 13-24. Substations using these design features have given trouble free service for over 25 years.5 11. helium. Small differences in resistance can affect the current distribution in some bus systems.. the joint in the presence of an electrolyte will be susceptible to galvanic corrosion. speed of welding.0 .s mechanically and electrically sound joints requiring no flux or special surface preparation other than the cleaning of the surface to be welded. both outdoor and indoors. Basic joint designs and welding procedures are shown in "Weldlng Aluminum". For bus work 4043 and llOO alloy filler wires are commonly used with GMA W. A welded connection that is mechanically satisfactory is also electrically satisfactory. Details of GMAW and GTAW welding as to shaping of the edges to be welded. however.0 k5i 35. thereby constituting a con sumable electrode. or a mixture of these) that keeps air away from the arc and the molten weld pool.• Alloy and Temper 1350-H1 1 1 6063-T6 6061-T6 Minimum Expected Tensile Yield Strength As Welded ksi I Minimum .0 ksi 4. size and kind of fmer wire. the copper side of the joint should be placed on the bottom for outdoor applications to prevent copper salts washing over the aluminum. Such joints. Welded Aluminum-lo-Aluminum Connecliom Weldlng of aluminum in electrical construction offers a superior and economical means of joining conductors. For ordinary applications (normal conductor temperatures of 70°C). It is not necessary to try to pro duce a connection with the same resistance as bus itself in order to have a stable permanent joint. current density. Some bus systems require equalizia tion bars. Strength of Aluminum in Weld-Heat Zone Bolted joints lose strength because of bolt holes. Proper ly made GMAW and GTAW welded joints also lose strength in the heat-affected zone that extends about two or three times the metal's thickness from the center of the weld.i Typical Yield Strength Yield ! Fully Strength of Parent: Annealed Filler 110" Temper"j Metal Metal 3. the result is a welded joint that usually has a lower resistance than an equal length of conductor for the recom mended riller metal. have given satisfactory outdoor service for many years. Welding Processes The most used welding processes for joining bus are the gas lungsten-arc welding method (GTAW) which employs a non-consumable tungsten electrode with filler metal fed by hand Or automatically.49. thereby eliminating need for welding flux. that because of the electrochemical relation of the two metals. The factors that influence the degree or the severity of the galvanic action are numerous and complex. the joint should be thoroughly sealed with a suitable grease-type compound to prevent the entrance of moisture into the contact surfaces. Electric arc welding using an inen gas shield produc. 13·46 There are a number of excellent papers on designs using welded aluminum bus for outdoor substations. If the weld bead is left on.0 15. l.One in which all phases are in a common metal enclQsure. Generator and Station Bus The generator in a large power station will generally be rated at 23 kV or higher with current rating up to 4D. The descriptions of bus installations in this section are only sufficient to enable recognition of the various types. Welded Branch for Bottom of A-Frame Assembly heat-affected zone is about 75 percent of minimum yield strength of the parent metal. resistance (flash) butt welding. (See ref.L'fW:~ :ill> I I I Usually one of these welds may be a shop weld at reduced cost. The bus runs from the generator terminals to the main transformer terminals are generally metal enclosed buses of the isolated phase bus construction. Typical welded tubular bus connections. diffusion bonding. exothermic welding. the bus may be of segregated or non-segregated phase construction.) or 50 Hz.J. distributed and utilized. three phase.20 contains the following defini tions for various types of bus construction. 13-21) may be used. explosion welding. capacitor discharge welding. but are segregated by metal bar riers between phases (Fig. resistance spot welding. reinforcing inserts (Fig. The various types of installations are considered in the order in which they occur as the energy is generated. with emphasis on the conductors. Bus Installations Direct weld after upper tube is cut to shape by means of special cutting template. Static bending tests of such joints show developed stresses as high as 28. Other Welding and Bonding Methods Other less often used welding and bonding techniques for joining aluminum bus are available for special cir cumstances and applications. Insert tube held by plug welds provides back-up for the butt weld and also reinforces tube strength. ANSI Standard C37. Isolated Phase Bus . transmitted.!J. Locate slot in region of lowest tensile stress of conductor tube. 13-22b). brazing and soldering. Among these methods are: GMA W spot welding.bus conductor design and applications Welded Straight Connector Slotted insert tube next smaller pipe size. gas welding. 48 and 50).One in which all phase con ductors are in a common metal enclosure without barriers between the phases (Fig.000 amperes.One in which each phase conductor is enclosed by an individual metal housing separated from adjacent conductor liousings by an air space (Fig. pressure welding. 60 (N. 13-21. American std. 13-22a). Another configuration has triangular bus arrangement in a circular enclosure. and with supports and protective housings only incidentally described. Welding to Intermediate Aluminum Connector Fitting 1"'!'-'. In cases where lower current ratings are involved. For situations where locating the weld in a region of moderate stress is not prac tical for tubular conductors. I I I I " I I I LL-<S-:2! Fig. Non-Segregated Phase Bus . Locating the weld in the region of moderate stress is a usual method of offsetting the effect of partial weld annealing.000 to 32. 13-47 .500 psi without failure for 6063-T6 tubing. To cover all these methods in detail is beyond the scope of this chapter and the reader is advised to consult the American Welding Society's Welding Handbook for fur ther information. 13-23). ultrasonic welding. Segregated Phase Bus . system voltage and test requirements. Fig. The typical arrangement of isolated phase bus as used in a generating station is shown in Fig. They are used for transmitting power in industrial and commercial buildings where concealment of circuits is not necessary.b.5 mm (0. the insulators are designed to fit the requirements for momentary condi tions.8 kV distribution.12. and in machine shops where current-using equipment is likely to be relocated with process changes. High voltages require better surface conditions.2 mm (0. -f.025) 0. 13-25). Figs.e. refer to references (11. but provide for plug-in at· tachment of power takeoffs at spaced intervals by insertion of grip contacts or "stabs".ting of side taps and reduce fitting costs.53).004) Standard Mill High Voltage High Voltage High Voltage Defects should be smoothed to a height not exceeding the appropriate value based on the operating voltage. in which a COm mon wall separates phases.In the case of the isolated phase bus. but there is no wall between phases. (b) Segregated three-phase bus. prefabricated bus-bar assemblies with associated fittings for distribution of ac Or de power at 600 volts or less in ratings of 100 amp or mOre.conductors. although IWCB or angles also are used. i.bus conductors ICg ~ 9 I. Protective or indicating . There are a number of technical papers that give con siderable detail On design of substations using tubular aluminum bus.6 mm (0. For a more detailed discussion of isolated phase bus design and application.52. Round tubular bus is mostly used. but repaired area should be blended into the remaining surface and should not exceed 250 micro-inch (AA).1 mm (0. and the take-offs are similarly tubular. one of three different support insulator arrangements may be used (Fig. Feeder busways supply power to a distribution center. Isolated Phase Bus . Gas Insulated Bus (58) Compressed gas insulated bus is becoming popular for switchyard installations where space is at a premium. as illustrated (54). !3·5k. They are particularly advantageous for vertical risers of large buildings. and (2) Massey's paper (55) using bolted con struction for 6" x 4" IWCB at 230 kV.51. Round tubular bus also may be mounted on inverted insulators. In each case. are to be used in substa tions over 230 kV so that "High Voltage Finish" can be supplied. 13-26 is typical for 13. nps for 132 kV bus. (a) Unsegregated bus in which the enclosure surrounds the assembly. and -g. l3-23a.062) 1. All buses have provision for expansion and contraction of the conductors and enclosures due to thermal changes.c). 13·48 Distribution switch yards that serve local areas at moderate voltages also use rigid bus for principal circuits. The supplier should be advised when tubular bus . 3 in. (0) i[gJQQ][g] \b) Fig. A typical method of providing for two levels is the A-frame. 13-22. Switchyard Bus The trend in switchyard design for 230 kV and below favors the flat-type of switchyard in which aU bus is on one or two levels. The maximum allowable height of a sharp protrusion is controlled to some extent by operating voltage. special attention given to the exterior surface finish to avoid sharP protrusions.57). High voltage substations require special care in regard to corona. Complete removal is not necessary. also are widely used in distribution switchyards because the flat surfaces aid the conne. Detailed information on design of moderate voltage substation using UABC and IWBC are given in a number of technical papers (56. sec tionalized. 13-24." busways are enclosed. as shown: Operating Voltage Maximum Height Finish Specification 230 kV or lower 230 kV to 345 RV 345 kV to 500 kV SOOkV 1. particularly for distribution voltages. Plug-in busways are similar. Angle bus and double-channel web bus. though connections between the low-voltage breakers and the disconnects may be of flexible cable. Two papers giving unusual information are: (I) Quick's paper (49) on welded construction using II" x II" IWCB for low voltage bus and 4-1/2 in. nps and larger.047) 0. supported by insulators (Fig. Busways Often called "bus duct. typical support arrangement.. Isolated phase bus . .Conductor (Typ.) .) Fig.bus conductor design and applications (A) (8) Pbase Pbase Spacing Spacing - Melal Enclosure (1)p..) (C) L Suppon Insulator (Typ. 13-49 . /3-23. II : " rI II I 1 Fig.:. Schematic ofground-type outdoor switchyardfor high-voltage transmission..:==---==[[j~I--'I. 1 \\ bus It "fl : II I (I It II .. I tpst . d.bus conductors Generator bU'~ phase Grounding ~=:-:.l.WitChyard r.'se loeb I. 13-25. 13-24. 13-50 .~ l-~ 0. Typical isolated-phase bus commonly used in generating station.JL N"utlral Reactor and excitation Transformer To potential transformers and instrumentation Fig.r===:. d m.t.-<.:~. Lower level bus tower I I I I I I Y I Welded A-frame of aluminum tubing for two-level 5witchyord \ l ~ Tubular bus ccrnductors ____ c:=::J~~""-. ~~~ Main " "~ u--'i1. Upper' level bus insert to clo. A swilchyardfor distribution voltage may be on same level and supplied through transformers from the high voltage main bus.e 011 open ends Transmission Line A \ ~~~~. Fig. 13-28.. Section through fully insulated feeder busway-cooled by conduction only. Typicalswitchyardfor 14. The molded plastic plug-in blocks open alternately On opposite sides so con nection can be made to any pair.J I WEEP HOLES Fig. 13-27. Another much-used form of feeder bus provides air ven tilation between the vertical bars. Types fond g. The bus conductors are Types k and m ofFig.4 kVsubstation. 13-26. The aluminum phase and neutral bars are solidly encased in laminated insulation. Weep holes in bottom channel prevent water accumulation. and the assembly housed in an aI/ aluminum wealhertight enclosure. which is held between top and boltom steel channels. They are paired to reduce reactance AB BC CA.. Typical plug-in busway. 13-51 . The arrangement shown is suitable for three-phase delta. The bars are immersion insulated between plug-in blocks and terminals. 13-3 either single or back-to-back. There are many varieties of plug-in busways for each of which advantages are claimed. 11r-r L_ _ _ _. By adding a neutral bar three-phase wye loads can be supplied.bus conductor design and applications fJ% 1 lMwllf Fig. or other flat-face types are equally suitable. Feeder busways often have bars paired or interlaced to reduce reactance. Buses for the Chlor·Alkaii Indust!)' (59) In large chlor-alkali plants. they may be unplated between contact areas but must be suitably plated at bolted joints or at plug-ins. The type of cell and the plant layout are major factors influencing the bus design.000 amperes. The housings may be ventilated or fully enclosed. the bus amperages involved are such tltat the I2R losses in the bus system can amount to appreciable cost. Sawed plate or extruded bar. an Fig.ZO. However. sawed plate and extruded bar in relatively thin wide sizes are used. ·27. NEMA BU-l and UL 857. Busway bars may be arranged flat or on edge. Switchgear standards are covered by NEMA No. Industry standards applying to busways are NEC Art. but others having important and valuable features also are available from manufacturers literature. connec tion requirements usually require moderate size bars of extruded 1350-HIlI or sawed plate. A few designs are shown in Figs. . Here the change in cross section from copper to larger cross section for aluminum should always be in the width dimension to gain the added benefit of lower reactance.62) Buses for electric furnaces present a different problem from buses for electrolytic installations since alternating current is involved and reactance of the bus system must be kept low. Standard operating temperature for plated busways is SS·C rise above 30°C ambierit. Aluminum "log" bus (rectangles in the order of 14" x 16") 1350 aluminum appears to be the favorite bus shape (61). Designers of bus systems for such plants should consider itn economic design based on a balance of cost of power losses with bus investment (I). Buses for Eledric Furnaces (9. Aluminum. some of the larger installations use from 15 to 22 million pounds of aluminum bus. 13-9. The larger installations use primarily very large thick cast bars of 1350 aluminum and some sawed plate. Capacity can readily be varied by multiple bar arrangements. and -28. some are purposely designed for high reactance to reduce short-circuit currents. Bars are interlaced to obtain low reactance (Fig. 13-29. In the stepped-paralled design Fig. optimize the conductor cross section on the basis of economics. The bus system is phase isolated/insulated to preclude accidental contact with live bus. Switchgear Rectangular bar is the most commonly used shape for switchgear bus because this shape is inherently easy to fabricate and lends itself to connector and space ro 13·52 Buses for the Aluminum Indust!)' (60J Although aluminum smelters vary in type of installation and size. 13-9). Although the total bus current may be quite large. Multi-bar stepped parallel arrangement for large de bus for electrolytic supply. Some designs use silver or tin plated joints while other designs utilize welded joints. with 85°C hot-spot temperature. are used for connec tions.blls condllctors quirements of switchgear. like the aluminum in dustry. 13-29 the individual bars extend far enough to reach the cell group they supply. The buses for these large installations may carry as much as 225. S05 and ANSI C37. and also are available in weather-reSistant construction for outdoor runs. 364. The major switchgear manufacturers use aluminum bus as a standard conductor material. devices also may be plugged in or permanently connected. Buses for the Magnesium Indust!)' Buses for the magnesium industry. Welded joints are used wherever possible. Aluminum bars are welded as an assembly by means oftop and bottom cross members. 1350-H1I2. mostly 1350 aluminum. 0004120 0.55 84.0001221 0.849 5.368 0.145 1.06 87.184 0.16 45.00 1.05 1.63 63.45 82.94 22.04069 0.6 152.26 71.031 1.147 0.002604 3/4 1 1% 1% 2 0.01318 0.0006510 0.221 0.58 1.792 69.906 2.46 76.604 6 1.441 0.00 4.21 1.18 60.4 101.02 16.23 8.74 100.006592 0.0000 1.292 54. 3 0.147 0.8750 1.4588 0.00 1.98 23.007812 0.01 < 1.33 64. Ibltt i 1 x-x 1 y-y crOhms per t! I at 70°C i mlcrohms per t! pert! 0.003255 0.001302 0.91 23.03125 0.01 < 181.55 12.682 0.02 < 1.07 1.0005493 0.00 1.003906 0.0938 3/16 271.00130 0.7 90.3750 0.84 14.1055 0.763 3.47 68.55 73.13 74.006510 0.2500 0.892 3/8 x 2% 0.6250 0.38 94.42 77.19 91.98 45.410 31.005208 0.615 4.029 0.1250 0. 0.15 54.846 6.82 33.0625 3/4 0.93 19.57 73.500 8 2.527 7.65 88.97 50.3 91.0003255 228.26 80.1250 3/4 0.4863 1.755 6.45 10.794 2. tance at i lance 60 Hz 1 t! spacing i in.441 1/4 x Vz 0.02063 0.331 0.470 2. 0.005493 0.1 120.750 3.009888 0.0008240 0.001099 0.5625 3% 0.133 5 1.04395 0.01758 0.528 16.0000814 0.02637 0.0002441 0.1875 0.362 10.01 < 1.07031 0.95 31.49 61.86 19.05 16.00 1.6563 0.3 76.176 1.26 78.6000 1.8750 6 2.2344 0.0713 1.527 7.73 38.43 9.3750 2 0.8 108.72 72.76 0.1 135.1250 4 1.11 1.0916 1.33 53.03516 0.49 25. x- + --x I I I Single Bar i I I Y Size In.04 1.24 79.86 45.93 49.00440 0.38 17.103 0.86 43.0002035 0.19 93.04 45.22 57.00195 0.01 < 1.0009766 0.0000 2.47 49.0079 1.01 < 1.662 10/4 0.29 11. (Continued) 13-53 .4 114. in.74 36.4 Area i :ZOOC mi : Rac/Rdc at 7O'C microhms Wt i Sq.6 76.750 12 4.08104 0.01 < 1.02197 0.2500 1.D1099 0.735 0.81 38.01 < 1.0002747 0.1675 0.2500 1V4 0.00659 0.294 1 11' 11/2 2 X.772 2 0.16 x V.01 < 1.24 1.02035 0.59 114.588 1/4 x 2'10 0.2813 0.0505 1.221 0.176 1.205 3.165 0. .22 57.26 80.3750 0.2500 0.04 < 1.58 86.0142 137.15 12.1875 1 0.27 20.5000 5 1.2 91.2500 8 3.622 6.527 16.992 0.276 0.1408 0.03516 0.0104 .5000 0.03< 1.03< 1.01 42.00879 0.66 52.8932 4 1.001628 0.05273 0.004557 0.01563 0.0938 0.3125 11/2 0.7500 0.26 152.94 15.9375 3 1.11 30. 1/8 x v.74 37.40 67.7500 0.70 0.bus conductor design and applications y I TABLE 13-25 I I Aluminum Rectangular Square-Corner Bus Bars Physical and Electrical Properties(l) 6101-T61 Alloy 57% lACS Min.13 1.1250 0.20 58.221 0.441 1% 0.250 5.62 57.70 9.87 84.8438 1.03052 0.24 12.08 0.5625 0.42 74.1563 0.351 4.08333 0.09 26.16 1.44 98.33 14.004395 0.10 1.31 63.00 i 1.11 28.57 68.294 0.7 3/8 x 1 0.1875 0.008789 38.41 21..01042 0.00 1.00260 0.1667 0.552 11/2 0.60 102.110 0.811 3.000 10 3.22 60.3560 1.0006666 0.58 68.007690 0.01 0.8438 2'12 0.64 34.784 4.00 1.78 19.0001628 0.001953 0.074 0.7 181.000 2.110 0.3255 . dc(2) ac Inductive I(See diagram at left) ResisResls reactance Moment of inertia .36 9.34 20.00 1.05< 1.8 90.05 1.1268 27.500 0.00 1.323 0. 1017 0.23 8.27 33.584 : 1-irCh bar not used fpr A-C I (Continued) 13-54 .38 47.716 4.464 228.34 1.17 1.351 4.858 2.7883 1.029 1.382 1.98 23.2813 0.145 5.397 10.500 3.362 1.176 0.7939 314 x 3 4: 5: 6 8 10 12 2.01823 0.11 1.bus conductors TABLE 13-25 (Continued) Single Bar !.73 37.1250 3.860 7.18 1.260 65.820 0.Q15 6.31 1.000 14 14.681 8.33 62.820 9.08 1.53 518 x 2.738 5.01563 0.67 13.847 5.786 2.858 2.0000 21.08 1 x 8 8.830 6.' 0.1758 0.4 20"C mi a170'C microhms Area WI RaC/Rdc 1 x-x 1 y-y Icrohms per ft al70'C microhms per It per ft Sq.906 5.01 52.2034 0.7500 4.2109 0.250 7.56 42.704 21.811 3. Iblft 112)(1.2233 0.735 0.344 4. dc(2) Inductive II<: : (See diagram at left) I : reactance ResisResisI I Moment of inertia ' lance at lance 60 Hz :1 ft spacing ' in.056 72.40 48.675 4.764 66.408 42.667 10 10.0000 18.058 1.0000 3.86 19.64 27.3515 0.5000 5.528 9.43 9.79 59.6510 1.16.72 75.333 18:18.716 4.51 8.306 2.39 61.08138 0.250 1.1909 1.0207 0.000 1.146 7. ! y I I I (- + --x I I I Y Size in.0951 .003 6.667 2.750 2.528 3.12 42.962 3.166 7.20 55.2500: 2.1408 0.10410 0.0000 1.125 11.796 5.02083 28.02604 0.50 108.01042 0.5000 1%! 0.573 2.72 57.880 41.551 3.000 5.00 62.77 51.25 26.588 0.646 3.08250 0.00 33.868 9.470 0.811 2.03646 0.04167 0.0000 0.02 1.8750 2 1.8932 0.588 1.01302 0.805 1.00 0.13 1.667 16.410 4.292 6.0000 7. in.05 1.06 10. 0.125 2.0000 11.777 3.1055 0.1408 0.04 1.905 1.52 1/2 x 2% 3 3'1.29 .000 6.940 3.763 3. 1.40 37.333 12 12. .2951 1.69 41.1402 1.1221 0.50 32.208 3.862 1.0 0.176 2.940 5.763 3.0000 16.406 3. 1.98 56.08333 0.688 4.46 1.67 52.06104 0.05086 0.03 1.410 5.083 90.24 1.58 22.000 2.28 1.06 34.352 2.622 5.510 11.2441 9.00 83.5000 8.4290 1.0000 9.06 37.94 70. 1°·6666 '0.65 72.560 8.168486.0 0.120 1.816 341. .5625 1.422 6.5000 1.000 7.000 4.34 1.88 48.3333 1.330 14.03125 0.44 12.057 3.760 83.33 5.0000 10.000 4.1782 1.849 61.500 1.813 13.333 6.8333 1.36 51.796 4.08138 0.500 1.05 16.05208 0.54 33.6250 1l~ 0.7500 5.838 2.8138 1.527 8.000014. 4 5 6 8 10 12 1.286 1.667 7.8750 2.5000 3. x.205 2./.38 18.2097 1.7500 10/.000 6.112 144.2587 1.40 1.04167 0.058 7.55 20.39 1.28 1.1626 0.000 . 3 4 5 6 8 10 12 1.764 1.1666 1.26 78.3333 0.22 1.33 14.573 3.398 3. 45 12.68 1.94 2.TABLE 13·25 (Continued) ------- Two Bars Three Bars ~"'---r--- de ae X.83 2..13 1.36 1.02 63. Resls· Resls- Inductive tance at 70°C mi· crohms per It Size in.18 1.92 4.76 45.35 4.42 1.61 67.68 6.53 3.34 34.13 1.05 5.64 23.64 15. r if ~- 8.10 63.83 3.591 6.36 22.70 55.76 11.42 38.89 2.226 1.51 1.09 11.55 5.64 38.89 1.17 2.83 40.70 4..00 2.69 1.13 34.31 36.55 5.83 2.05 53.33 8. 1/4 x 1 1 1/2 2 114 x 3 4 5 6 6 3/6 x 2 3 4 5 6 8 10 1/2 x 2 1/2 3 4 5 6 8 10 33.21 49.94 5.83 1.51 1.76 5.77 1.03 3.40 54.25 3.77 2. elc.97 54.67 59.77 51.10 23.16 54. Induetl.27 3.10 4.63 47.41 43.43 1.52 1.89 3.14 11.21 41.64 5.75 4.83 2.578 1.66 4.06 50.26 1.04 32.455 1.00 12.26 1.247 1.04 1.66 4.97 3.06 5.08 2.30 4.20 2.95 46.70 1.69 50.06 41.45 1.96 22.40 2.14 39.26 2.00 77.38 2.64 47.27 1.) are also suitable for bars having rounded edge within accuracy limils thai are regarded .67 2.11 ~~-- ~ (1) Struclural properties (moment of Inertia.98 5.20 2.64 32.22 45.77 8.26 1.82 7.15 18. ~ 8' g- iii .66 4.68 3.32 8.72 1.01 3.10 1.05 0.13 46.00 7.92 39.54 67.72 7.83 2.82 47.19 5. '"• UI UI as satisfactory for bus-conductor applications.32 1.40 2.72 1.79 1.92 5.43 59.]9 7.70 2.13 4. tance 60 Hz a170°C Inductiv~ mJcrohms par It reactance 1 ae Reals de Resis 1 It spacing tanee at microhm.66 4.45 8.06 34.93 5.26 1.690 1.849 1.26 55.07 1.61 3.64 16.140 1.35 49.16 50.91 6.536 1.33 9.98 1.91 5.63 4.16 1.26 35.12 1.: See also pages 13-6310 13-67 for addillonallnformalion regarding Tables 13-25 through 13-32.83 2.15 12.55 5.45 71.89 1.09 49. Real.56 3.77 3.91 7.307 1.32 1.19 5.12 1.04 43.16 30.06 1.45 43.55 16.25 1.58 1.98 11.70 1.83 2.399 1.04 1.40 2.19 44.326 1.55 18.166 1.66 4.06 39.60 7.70 31.39 71.418 1.26 12.414 6. at 71l"C per It per It rohms per ft at 70°C at X.89 1.25 3. i 71l"C mlc Rae/Rde par It rohms par It at 70°C X.36 1.]9 5.47 3. de tance 60 Hz reactance Resis at 70"C 1 It spacing tance at Rae/Rde microhms mlcrohms 70°C mle Rae/Rd.45 9.41 16. Nol.77 2.22 49.40 4.76 67..069 1.02 3.42 1.95 47.87 4.78 2.26 1.53 3.25 5.93 38.91 2. (2) dc resistance at 20'C Is based On minimum conductivity of 57% lACS for 6101-T61 alloys.49 6.12 1.28 64.12 3.352 1.42 1.31 60.31 1.67 42.183 1.02 1.49 1.43 38.96 34.33 1.32 7.02 2.e tance 60 Hz reactance at lOOC 1 It spacing mfcrohms mlcrohms per It per It c .00 56..13 5.51 1.10 1.42 1.57 3.21 58.22 1.77 2.04 6.66 37.38 44.34 2.63 1. Four Bars .66 4.88 45.51 1. For other temperature rise values see Fig.02. 3. 4. Horirontal bar ampacitv from industry sources. Vertical bar ampacity ba~ on work by House and Tuttle. Space between bars is assumed equal to bar thickness.35). 13-56 . correspondIng to usual Indoor temperature. x 3 1/4 4 1 Sa. i 585 BOO 1010 1380 1720 2000 2220 2640 1230 1680 2080 2420 2710 3240 1870 2290 2680 3050 3640 ae de 775 1060 1340 1850 2300 2670 2970 3410 1620 2250 2800 3250 3680 4210 2560 3150 3630 580 785 980 1310 1800 1830 2010 2320 1170 1550 1860 2110 2330 2700 1650 1960 2240 2490 2900 4060 4790 3 Bars 60Hz ae 887 1194 1480 2000 2462 2905 3338 4183 1831 2384 2893 3367 3857 4774 5632 2742 3264 3778 4284 5276 6256 3B.bus conductors TABLE 13-26 Current Rating of Rectangular Aluminum Bus-Bar Arrangement. ~ For 1350. FOr de ratings of other alloys. 6101-T65.035. in air with no attachments. Ratings based on 3O!lC nse OWi' 40 C ambient in still but unconfined air (e ::::: 0. Amperes . 60 Hz at 765 1020 1280 1700 2050 2330 2540 2840 1490 1980 2340 2650 2940 3270 2080 2470 2780 3050 3490 c 0000 de 1203 1637 2053 2851 3619 4355 5095 6517 2636 3620 4563 5479 6375 8119 9817 4324 5417 6477 7514 9531 11493 ~ de 905 1240 1560 2180 2740 3160 3440 3900 1920 2730 3360 3850 4280 4820 3070 3800 4370 4800 i 5610 4 Ban. 6101-T64..an allowance tor proximity effect must be made. the use of these multipliers IS conservative.6101-T6.982. 5. 0. RatinQ$ ate based on horizontal mounting. 2. 60 Hz de x1 1 'h 2 3 4 5 6 8 $/~ x 2 3 4 5 6 8 tt.992. For a-c phase spacings less than 1S-ln..998. for 6101-T61 Alloy 57% lACS Conductivity (see footnotes I 0 Size de (InehesJ 1/4 x1 1 I/: 308 430 549 760 1005 1225 1443 1870 691 974 1249 1519 1785 2308 2822 1145 1462 1774 : 2081 2885 ! 3278 i 2 3 4 5 6 7 ~J'$ x2 3 4 5 6 8 10 t/: x 3 4 5 6 8 10 = Sire (lnchesJ 00 60 Hz de ae 308 429 545 768 980 1184 1351 1760 678 941 1191 1429 1657 2098 2534 1074 1369 1634 1892 2393 2880 . 60 Hz ae 1168 1561 1915 2530 3081 3625 4146 5152 2332 2946 3574 4178 4765 5875 6841 3297 3940 4580 5210 6246 7579 4 Bars 60 Hz ae 880 1180 1460 1940 2330 2610 2800 3080 1700 2220 2630 2940 3200 3490 2340 2750 3690 3330 3720 1. 607 833 1051 1472 1878 2275 2665 3427 1340 1857 2356 2842 3320 4253 5165 i 2205 2782 3345 3867 4975 6209 = = lB. 6101-T63. 13-11... ! : I 300 420 535 750 955 1180 1320 1620 670 935 1190 1420 1630 2000 1100 1390 1650 1890 2310 000 60Hz de ae 601 817 1021 1410 1760 2092 2413 3034 1278 1709 2099 2483 2847 3569 4289 1991 2416 2828 3230 4014 4779 905 1235 1552 2162 2749 3321 3861 4974 1969 2739 3460 4162 4848 6160 7493 3265 4100 4912 5706 7255 8763 = = = 2 Bars 60 Hz de ae 300 415 530 735 930 1120 1270 1520 660 905 1130 1340 1520 1820 1050 1300 1520 1710 2050 2 San. multiply b y : " . For 60 Hz. 0. 1. 1. 0. 247 470 590 774 985 1137 1446 1907 2363 2735 3118 3505 3948 4891 58. W O.264 2.49 17.900 2.2503 0.016 3..40 6.93 33. 22 O.725 8.940 1.135 4. Inductive Reactance 1 It spacing Area Weight 60 Hz-Xa Ibilt microhm/It sq. lance at 20·C microhm. per It ac Curren! Reslalance Ratings at 10"C Amp a! 60Hz 80 Hz microhmsl (1)(2)(3)(4) It Outdoor 6( H R.58 48.95 38.166 3.598 2.405 0.678 4.315 1.05 1.44 65.0039 1.326 5. ------ .14 12. Wall of Thick Tube In.737 2.3326 0.625 O.39 10.56 50.0057 1.733 4. 45 54.0139 1..229 3.091 6.00031 1.574 2. (4) NEMA Standard 8GI-3.050 4. Dlam.24 1 00:32 1 00 39 1 00 46 1 00 55 1 00 5 1 00 B 1 002 2 1 10: 7 1 o3 1 o 0 1 0' 4 86.22 14. 24 O. ~ <0' " g Q.4939 0.58 27..0047 1. Nominal oxidized surface (9 3831 4532 (3) Current ratings for direct current are close to those of altemating currents for all except the larger sizes.004 2.45 24.00075 1.61 37.0095 1.923 4.28 14.897 5..63 30.40 46.0038 1..875 3. even after adjustment for the 53% lACS conductivity of 6063·T6 alloy (and 43% for 6061 T6 alloy).183 6. 25 O. 01 73.754 1. generally assumed not to be significant If spacing is 18-in.786 0.281 5.318 0.375 2.875 3.65 21.23 45.500 5.13 34. R • rt 71 10(.12 8.14 66.38 28.99 19.0260 1. but without stated emissivity factors.581 0. -- 6 003-T6· 6061-T6 --------- Outside Nominal SIze In.iS- ac 10·C at 100(.563 6.20 31.765 5.180 6.16 54.254 3.112 8. currenl ralings for tub•• of 57"/0-61% lACS conductivity.ln.001 5. 19 42 04 39.6338 0.558 3.0095 72.71 9.03 22.684 5.0049 1.842 4.300 5. However.00053 1.0021 1. 23 O.000 4.0010 1.510 0..7995 1. O.179 0..81 63.0103 1.31 36.208 5.150 4.60 16_82 10.547 4.717 4.300 0. neas In.55 42.736 4.500 5.168 3.07 20. de R.63 11.621 3.147 0.0075 1.62 49.834 5.05 1.80 34.294 0. li1.099 2.376 0.12 22.5 percent. .68 56.375 0.89 24. 60Hz mlcrohmsl It Current Ratings Amp a' 60 Hz (1)(2)(3)(4) Outdoor Resistance lance 60Hz at 2O"C R.075 1.34 23.82 32.TABLE 13-27 Physical and Electrical Properties of Aluminum Standard Pipe-Size Conductors at Typical Conductivities 53% lACS for 6063-T6 and 43% for G061-T6 - ---------- ..581 0.0014 1.487 2. 0.394 1 0017 1 00. (2) Conductors outdoors with a 0.4335 0. 15 O.44 14.375 2.50).0058 1. 14.52 16.037 1.30 20.298 3..897 380 473 622 705 900 1128 1520 1865 2145 2436 2728 3063 3719 79.0072 1.228 2.828 429 539 707 901 1039 1322 1746 2166 2507 2862 3221 SCHEDULE 80 PIPE 1/2 314 1 1114 I 1/2 2 21/2 3 31/2 4 4112 5 6 0. the ratings differ somewhat from Ihose of this Table.337 0.05 43.00062 1.500 4.84 1.06 17.3200 0.37 27.218 0.657 3.884 (1) Current ratings listed in the Tables are based on 30"C temperature rise over 40"C ambient horizontally mounted conductors.650 3.41/2 5 6 0.068 1.178 3.0005 1. 14 O.00074 1.256 1.174 3. U1 affect the ratings.092 7.69 28.00063 1.14 89.477 2.977 4.432 0.563 6.500 4.829 1.00038 1.I.254 1.0028 1.62 8.019 6.968 5.128 6. 55 88..84 1.00024 1.000 5.660 1.820 5.000 4.73 12.46 41.02 (7113160) lisl.38 39.680 3.857 2.070 5. or over. 29 62.26 8.660 1.191 0.'t' . 0 :.90 2.82 6.2 8 36.94 12.0210 1.0171 1.8815 1.032 2.02 35.151 3. and for them the increase ror de bus is about 1..68 9.69 17.154 0..500 7.625 0..391 0.cIRdQ mtcrohms per It at SCHEDULE 40 PIPE 1/2 314 1 1 1/4 1 1/2 2 21/2 3 3112 4 .057 6.00064 1.689 4...751 1.0020 1.19 43. 1 O.85 45..00039 1.0212 67.200 0.188 9..0030 1.0015 1. } [.704 2. 2~ftlsec crosswind. de R.051 3. 15 49.266 16 17 81 59 84 1 34 1 63 20 40 2 4'1 2 64 2 84 3 48 4' 64 75.955 4.925 4. 13: O.89 54.407 5.236 3.338 5..57 20. .0116 1.70 29.0022 1.6685 0.. Conduction or heat by supporting structures and taps can appreciably . 31 30 23 61.315 1.00105 1.276 0.0457 56.515 1.072 6. 20 O.356 0.096 4. with spacing sufficient to eliminate proximity effects..0165 1.30 9.564 79..406 6.66 74. 68 59.406 3. 2 O.637 7. 006 1.088 2.260 0.3 12.33 17.721 1.0 23.8 630.34 24.815 1.006 1.7_61_0_~.079 1.312 0..091 1.486 1.140 1.01 14.654 1.41 0..27 195.7 20.95 15.573 1.3_99. 2.2 362.08 11.55 6.831 1.504 1.7 1.813 1.3 23.375 0.7 121.75 65.03 0.014 1.8 33.16 12.3 16.9 21.791 0.20 99.043 0.7 12. I Out· side diam.222 2.027 0.500 0..32 483.312 0. 6 7 8 9 10 12 Weight lb/ft Moment of Inertia 1 in. in.241 1.34 14.94 33.63 8.247 4255 5100 5650 5980 5245 6285 6965 7370 11.092 1.44 63.2_2-L_3_6_.8 94.1 33.500 0.389 1. Area sq.65 111.2 25..2 29.72 0.030 1.987 1. 3846 0_.7 2.33 13.70 19.015 1.406 1. and 3 of Table 13-27.50 11.375 0.278 1.63 0." 5.659 1.591 1.563 2.5 168.5 131.64 10.21 12.640 1.677 I .142 1..sis as per Notes 1.674 0.250 0.2 26.090 1.tlngs are on same b.116 5185 5635 6255 6640 6355 6910 7670 8140 11.58 6.94~E _ _'--0_.46 13.l1_31_.015 1.504 1.030 1.79 10.500 0..348 1.6 32.55 21.375 0.8 26.375 0.639 2...35 16.1 20.18 12.2 64.11 21.92 18..776 1.3 16.0 1.625 I Inductive dc Reactance Resistance 1 ft spacing 60 Hz-xa a120'C mlcrohmsift ! mlcrohmslft 14 R.156 1.3_-'--_1_3_.(.958 0.2 23.85 17.L_68_7_.5 2.312 0.264 0.9 29.09 8.250 0.2 28.7695 8570 9160 10345 11059 ! I 1.56 7.24 26.400 1.696 1.006 1.213 0.7_50.208 2.bus conductors TABLE 13-28 Physical and Electrical Properties of Large-Diameter Round-Tube Bus Conductors 6101-T61 Aluminum Alloy 57% lACS Conductivity (Minimum)(1j .414 3805 4555 5045 5190 4720 5646 6250 6435 65.0 145.354 1.031 1. 0.625 6.78 14._458 _ _"--1.23 43.4 ! i 0.6 299.931 3195 3465 4070 4020 4360 4840 5125 30.0 26.23 9.210 1.80 10.505 1.625 Wall thickness in.500 0..030 1.206 2.98 11.9222 6155 6685 7415 7850 7480 8125 9015 9545 21.8 231.8 203.094 1. Current r.62 26.632 3360 4015 4465 4635 4190 5010 5575 5785 45.089 1.070 0.500 0.52 6.7_1-.30 7.947 1.030 1.200 3.247 1.87 10.l_ _ 13-58 Current Rating 60 Hz Amp 32.092 1.375 0.56 13.34 0.500 0.807 1.70 18.544 1.21 28.6 2.4 23.031 1.16 10.8761 0.44 8..41 22.16 13.625 5.48 7.375 0. In.203 3.500 0.94 38.0 54.4 16.243 1.0_---'_ _ 0.17 13.093 1.47 16.6 20.625 9.33 39.625 6..250 0.6 16.5 29.lRdo: i at 70'C ac Resistance at 70'C 60Hz mlcrohms/ft Indoor Outdoor 2.9 0.213 1.06 22. tube. Add 15 percenl to current ratings of ventilated tubes having staggered ventilating holes spaced 4-in.18 6. The e 0.. The e == 0.482 8.352 3... Ibift 3 3 3 ¥e % V.729 2. in.016 2.4 microhmslfl (e) I sq. for 6-in lube.271 7..575 8.04 1..667 1..918 2.108 4.158 7.21 4. 447 1 29.. For temperature ri•• of 500C above 4O'C ambient.056 3540 4170 4570 4420 5200 5640 112 5 5 5 ¥4 V.215 4.7 39.0 39. 13·11).272 4.394 5.189 2. condUctors horizontally mounted and spaced sufficiently to eliminate proximity effects.643 3. 1V.43 ! 52..90 rating applies similarly but with surface painted with fta! i1Of1metallic paint.6 2.4 29.727 8.127 2450 2880 3040 3020 3550 3760 5.733 10. Ventilated lubes have about 8 percent less weight.36 9.11 1. (S•• Fig. ..954 4.683 4.571 6 6 6 % % % V.35 29.173 1. for 5-in.06 1.571 4.825 3.05 1.407 3.76 28. V.982 2.- For 6101·T61 i Inehes (a) Square Size (b) Outside Comer Radius (c) Web Thicl<ness (a) (b) InductiVe Reactance ! Moment 1 fI spacing i Area Weight of Inertia 60Hz-X. 1o/e in.6 3.1 46.175 1.32 33. Current ratings are based on 30"C rise over 40"'C ambient.736 4.571 3.bus conductor design and applications TABLE 13-29 Physical and Electrical Properties of Square Aluminum Tubular Conductors 6101-T61 Alloy 57% lACS Conductivity (minlmuim) I. 1 jO.418 2.-. increase ratings by about 30 p.08 I 1.607 1.1 3.35 rating applies to tubes tn still but unconfined air (usual indoor condition) with normal Oxidized surface.600 3.9 5.375 3.. 1V. tube.13 1.968 3..26 22.90 V.06 38.497 : 41.236 6.221 6.rcent. for 4-in.1 29. ¥< % 4 4 4 'h de Resistance at 20°C mierohmslfl R~/Rde ! al 70°C 60 Hz I 1 ae Current Ralings 60 Hz Amp (1) (2) Resistance i of 70°C 60Hz i mierohmsift ! e = 0.126 1. % ¥e ¥.346 2.. lube.8 34.215 11.5 33. i V2 5.457 2980 3490 3610 3700 4340 4730 6. 1¥.384 1880 2170 2250 2300 2640 2760 % % ¥. apart longitudinally with hole diameters as follows: For 3-in. in. V2 3.57 I ac I ! I ! I 1. ¥.770 1. 4.28 I I 1. in.24 4. 2.08 16.35 e = 0.a T Tabulated values apply 10 unventilated tubes.09 1.482 6.075 10. in.589 5. --l I~ b a ~ .30 13.598 45..5 46.59 12.15 1. 13-59 . 15 2300 2910 3660 4760 5800 2760 3500 4400 5700 6950 4.500 0.562 11.44 109.397 0. 13·11. 5.13 91.02 1.8 29.437 3.602 1.11 1.2 33.500 0. Wt.~ ! I I _ _~_L_~ 1.8 25.687 0.11 13.187 7 3.4 47.47 1.27 198.60 2. R"JR&: .04 1.500 0.35 .13 1.16 1.0 16. and for 2 ft/sec cross wind for usual outdoor conditions (e -= 0.9 6.893 0. 5.21 1.32 1.75 1. microhmsfft microhmslft 60 Hz : miaonmSlft: • = 0.32 11.375 0.7 29.68 S.07 49.794 46.15 6.) 13-60 .687 0.34 5.562 0. I 12.812 12 5.125 0.66 6140 6790 6820 7350 8150 8450 8.44 i 99 1.L __ __ 1.91 8. electrical properties are for two channel'S in face-to-face arranqement.625 7.38 7. 8 3.21 1.4 74. 9.18 0. 7.0 1. e = 0.7 ____ 1.49 3.187 2.13 7.315 12.60 119.627 0.50 Moment of Distance Inductive Reactance I I 5.327 1.37 1.S32 1.3 0.75 6.05 2.28 1. 5.625 0.60 1. 6.25 0.3 14.83 0.312 0.bus conductors TABLE 13-30 y Properties of Uniform Thickness Aluminum Channel Bus Conductors W Physical pt'opertles are for single channels.933 4.33 10.812 12: 5.25 0.15 1. 5.250 11.935 0.64 11.35 1.687 8 3.4 1.812 0. 7." Y T ~6_1 • Face. 1 Corner Radius Web Thick- A ness .3_ _:_ _ 1. 1/2 518 3/4 0. 0.35}.625 9.t 70°C at 20"( at 70'<: I 60 Hz Indoor Outdoor X i 60 Hz-X.5 19.03 8.40 1.375 0. 8.87 8.188 4.8 13.S 1.375 5.11 i 288.59 6.375 0.4 17.46 0.57 45.71 128.54 1.67 4.07 1.71 1.36 1.73 7.84 4.44 2.732 1367 1.49 11.2 40.29 1.82 4.63 6.631 1.2 14.7 5.69 7.50). For temperature rise of SO"C above 40"C ambient.18 1.1 22.946 1A75 1. in.625: 12. see sketch J .2 39.21 3.973 1.25 in.9 14.33 6.7 44.2 25.312 10.S 7. 6101·T61 alloy S7.61 33.4 12.0 22.70 3. 1.67 __ 12. Ix·x Iy-y in.1 14.4 14.687 8 3.5 1.248 0.7 0.102 0.1 1. Ratings are based on 3ifC rise over 40"'( ambient temperature in stW but unconfined air for usual indoor conditions (e == O. I 60 Hz Amp Neutral : 1 ft spacing Resistance . 2.4 1.80 1. 1. 1 ~30 ~~I~ ~ I .08 8610 8100 8940 10400 10500 9750 10800 12400 5.74 1.72 13.41 1.72 0.70 1.187 0.23 1.5 21.017 0.51 19. 8.43 7.25 12.542 1. an increase of about 30 percent of current rating indoors is generally in accordance with tests.187 7 3.10 22.44 1.35 6240 6560 7900 7500 7900 9400 4.068 0.40.53 27.625 -x i I I Dimensions in.21 1.625 0.625 3 4 4 5 6 9 11 11 11 : Sq. 186.75 2.997 1..04 1.31 8.35 12 5.56 1.23 6.0% lACS Conductivity {minimum) Outside Corner Radius in.2 6.5 8.750 0.9 63.. 0.toKFace Pair .7 4.989 24.79 6. 0.312 1.38 2.312 ·0.312 11. Area B T W 1.23 1.77 5. (See Fig.42 1.46 7 3. Ibift ac ac Current Ratings to de Resistance Inertia in'" .945 __ __ ~ 8980 10800 10500 12100 13700 _11550 _ _.19 5.t'~ Single Channel 1 I 3/8 in. 024 .875 1. ratings are based similarly. 5.375 2. the Z~Z radius of gyration is increased 20 percent.79 1.86 de ! RaiR.313 1. 11< or y 1.50 1.875 2. I (3) I T Area in.42 4.83 1. 1.LIN. 13-Sk} has a lug at top that does not interfere with bolting.75 1.96 i Resistance ! 60 Hz-X.175 ! 11.045 1.93 41.75 1.09 1.1t.36 ' 3. Craig.54 Kory. '!Is 3/.50 9. Alignment grooves are extruded to facilitate centering of holes according to NEMA standard spacings. '!Is I ! I wt Iblft . A modification of this design {see Fig. Indoor current ratings are based on 30"'( rise over 4(Y>C ambient in still but unconfined air.14 1. yet it strengthens the shape against tenden<:y to roll-over to the z-z axis in long spans subjected to large lateral short c1rcuit fortes. Angle 3'/4 X '/4 4 x '/.30 3.06 6.75 1.28 1./( I at 70'C i at Resistance at 71Y'C 60 Hz : microhmslft I 1.60 4.02 D 2.SO e ! I 1902 2236 2654 2885 3130 1. 3V41 4 4 I I 4'h : 5 v. 0.70 Am~OHz i e Indoor ~ 0.00 2. See page 13-66 for additional information regarding this table.56 1.62 43.50). Notching Dimensions A B C 1.20 5.651 1. 4.. I 1.24 I 8.91 1.0% lACS Conductivity (minimum)<4l I See Sketch inertia in. in.84 6. Back-to~bac:k.187 2.145 1. The stress that causes rotl~over is thereby increased about 40 percent.27 I 3.. 3.35 1300 1550 1850 2050 2250 Outdoor ~ O.06 :: Detail L Sol'ft" Not(hing on Other leg 13-61 .93 I Distance I Moment of Size wi Minimum (2) V. angles are to be considered as separate members.39 1. Indoor ratings based on work by House and Tuttle. Pemberton. 4'/2"/' 5x 'I. Outdoor 2.75 1.006 3.75 2.52 11.23 3.04 2. generally assumed to be 18-in.22. Bleshman (22).IN..77 2.74 I.00 -l x I.60 2.55 1. 4 x' I.26 1. but with 2 ft/sec crosswind (e == 0. I Sq.13 5.115 1. For equal weight of shape.23 9. 0.80 I 6.35). in. normally oxidized surface (e = 0. I ! I ac (1) Current Ratings ! I Reactance 1 ft spacing I i i Inductive i I I I 1.36 4. Horizontal mounting is assumed with spacing sufficient to eliminate proximity effects.00 2.46 6. or over.55 3. I W " 0.85 3.41 46.60 46.813 2.. 4 to Neutral Axis . Outdoor ratings from IEEE paper by Prager.256 r. microhmstft at 7fY'C microhmslft i 51.61 1.00 2. not as a composite.813 3.bus conductor design and applications TABLE 13-31 Properties of Uniform Thickness Angle Bus Conductors 6101-T6 Alloy 55. z 0. 4 2.59 46.11 1.94 10.6 362 4 .09 1.60 8.000 4.375 0.82 3400 3760 4020 4320 4760 5190 64.49 3480 3900 4200 4500 5020 5730 34.9 1.50) Horizontal mounting is assumed with spacinfl sufficient to eliminate proximity effects.11 1.12 1..87 1.21 6 10. consult suppliers. Indoors 60 Hz-X.788 6.28 1.500 12.156 4 0.94 2240 2276 2980 2520 3115 3360 3.50 2.05 16.064 1.--.95 1.96 9 9 0.5 .25 3. For standard vent diameter and spacing.08 8.1 0.10 8 5 0.. More test work is needed for outdoor.43 0.84 15.05 12.625 32.0 I 0. -.68 3. except 2: ft/sec cross wind le=0.84 9060 21.. .21 3 9.79 10490 11330 I 8 Outdoor ""ler T 1 11 11 0.28 37. Wall Moment of Inertia.74 14.64 1653.46 dc Current Rating Resistance de Rd<70-C mlcrohms per ft 1)'-'1' ~ '" Induc.41 2.375 0.0 17.375 0.8 1.82 1..37 1. generally assumed to be 18~i"" (U over.7 12 12 0.. 13-11 J Q Indoor ratings (dc and ac) calculated by computer and verified by tests.15 13.02 6. in.75 2260 2810 3050 39. 152. For 6101-T6 reduce rating by 2 pe(cent. 451.45 5.14 7740 8450 27.78 45.04 10 10 0.12 10.0~ 11260 12980. ness T in.- 0 CoO c: • 0- '" 8 t-) t TABLE 13-32 Properties of Integral-Web Channel Bus Conductors 6101-T61 Alloy (lACS 58% typical) .625 23.3 240.16 30. Wt Ib/ft Ix..1 30." 2.8 36.5 27. L See also page 13-67 fm additional information regarding this table. 2'.." Thick· c-------.3 1.-.75 16.375 0.57 162.44 2.500 8 0.6 1..04 5350 6090 7740 29. ----r---- SIze (See Sketch) A in.98 60.53 0.71 10260 19.581 3.050 1. (See Fif!. Area sq. Outuoor ratings are calculations only. For temperature rise of 500.) C abolle 40° C ambient.20 1. rounded.35 14. and notch~groove arrange ments.67 66.500 9.01 8610 9350 16. normally oxidized surface (R""0.22 5.. size is a composite of two symmetric extrusions bolted together.94 6.83 95.78 2.45 29.. ..96 312.tlve Reactance 1 ft spacing ac 60 Hz Resistance Current Rating ac-60 Hz R. microhms per ft 71l'C 60 Hz R".22 2.250 0.91 9390 10170 15.50 6.86 3.!R.625 26.76 281.82 18.5 22..876 5.31 5060 5380 6890 5560 5910 7550 23.6 1.6 1.42 3.08 8 8 11.--------.30 6530 27.--------. The 12 in. 1.78 6.95 7.21 1.035 1.35 e -- ~I 0.6 31.87 4.16 1. .781 4.0 24.. x 12 in.19 7 7 0.020 1.64 255.1 lA2 1." .91 25.17 8.00 3780 4180 4470 4800 5270 5740 70"C e = 0.02 39.68 13.42 1. .76 40.60 11.892 4 4 4 4 0. The sketch onlv approximates a typical outline.250 4 0.550 4. Current ratings an: based on 6101~ T61 alloy with standard vent wholes in web. The interior perimeter varies according lO the washer diameters that are to be accommodated. In.62 7. 5 6 6 0.62 32.84 103.88 4.312 6 6 6 6 6 6 4 4 4 .. 8 In.35 Indoor e 0. For vent and notch amm!Jements consult $upplier.08 1.84 1.8 0. .7 1. and <)s to their location per NEMA SP3Cing.19 29. Indoor ratings are based on 30 C rise over 40" C ambient in still but unconfined air.58 5940 6540 52. the indoor ratings for 30" C rise may be increased about 30 percent.73 40.625 20.70"C microhms per ft 7...375 5 0.35) and similarly for outdoor ratin9'l.439 3.50 2.26 2.B 1.88 37. bus conductor design and applications APPENDIX 13A Notes To Tables 13·25 Through 13·32 General Table 13-25 I. Aluminum weights are computed on basis of 0.098 lb. per cu. in. 2. Elements of sections for rectangles, tubes and equal angles calculated from following relationships. Aluminum Rectangular Square Corner Bus Bars 1. Direct current (de) ampacity values calculated from House·Tuttle formulas for vertical arrangements RECTANGLE Am I)f momenta thnro.a:h center A 11"'1 -W- = bd' ,-. , L j .Jl2" = 0.288676d -. :II' A ,- = 0. <'H>"''''98 dJ dll ~ 'R'6:* = 0.G490S7 d. = 0.098175 d a Rac/Rdc and xa values from Mak and Lewis paper (5) for some sizes, X. for other sizes from tables by W.A. Lewis for Alcoa. Other RaciRdc values from Dwight's Charts (4). Table 13·26 Current Rating oj Rectangular Aluminum Bus Bar Arrangements 1. Direct current (de) ampacity values calculated from House-Tuttle formulas for vertical arrangements 2. Example (Refer to Ampacity discussion) 4·1/4 in. x 4 in. 6101·T61 bars, vertical arrangement with 1/4 in. spacing .-.. ··~--'·-~--~·"·f--t ~ = b2 +ct : y x b + 4S" t(b-x)3+bxLa (x-t}* , t i :, • 4 Il~l = 12-2 =. :-T*.t Il}-a I ...... = 8 It-1 0.35, Ta = 4O'C, Te. =_70'C, Rdc at 70°C = 4.245 x 10-6 ohms ~ , }"-h.-_-,··t : "'-·l~·· .. ·~a----." ;,...- --2 .-M~b.d ---; .•..; e t (b+c) A .,J t"l : ~_o./"3 3. EQUAL ANGLE rJ' • , as a conven· d ,".1 _---b····'" x Rae at 70°C is listed for 2, 3 and 4 bars ience for doC applications. bd ~ x 1'- ·R·, 1 1x = 2. 1. r;t3+C'IIH~(b-u+2t;)II+t'+6tp(!b:-t)'J 1~\0.25 We = 0.0275 P e I: L / where Pc = 4 x 8.5 = 34 in. L = 4 in. etA+Cllt+3ctba+tL 12 Fig. 13A·1. = 30)°·25 (30) 0.0275 x 34 ( 4' Source: Carnegie Steel Company, Pocket Companion, 1920, = 46.419 watt/ft. 13·63 bus conductors Kf .00864 (from Table 13A-I) Ie = 70'C where P rm = 10 in. ta = 40'C e = .35 bars /4.5 x .0672 Wc = 0.1695 = .95 openings = 0.0439 x 10 ft(343) 4 x .35~ 100 t· X 7200)°·6 0.0478 x .00864 (7(}4Q) = (4.5)°·6 11.1165 = 27.409 watls/ft. = 6.520 watt/ft. for metal surfaces Wr = 0.1380 e [(~) 4 _ (~) 4J where 0 = 4.5" where ProI = 2 x 3 x .25 = 1.5 in. e = 0.5 = 0.0439 x 1.5 x .95 (42.33) = 2.655 wattlft. for open bar spacing values of K from Table 13A-1. Wr = 0.138 x 4.5 x 0.5 (138.41 - 95.98] W = 46.419 + 6.520 + 2.655 = 55.594 = 13.1745 'EW I = ( Rdc at 70°C )1'2 = ( 55.594 ) \1 \4.245 x 10-6 'i.W = 27.409 + 13.1745 = 40.5835 = 3,619 amperes Table 13-27 Physical and Electrical Properties of Aluminum Standard Pipe Size Conductors at Typical Conductivities 1. Ampacity values calculated from House-Tuttle for mulas 2. Example (Refer to Ampacity discussion): 4 in. Schd. 40 6063-T6 Pipe Conductor Outdoor Ser vices, e = 0.5, wind 2 ftlsee., no sun. 0 We = 0.1695 ( V)0.6 !~ whole D = 4.5 in. pf = .0672 (from Table 13A-I) V = 2 x 3600 (for 2 ftlsee wind) I'f = .0478 (from Table 13A-I) 13-64 = ( )0.5 40.5835 5.717 x 10-6 = 2,664 amperes bus conductor design and applications TABLE 13A-1 Viscosity, Density at Sea Level to 15,000 Ft, and Thermal Conductivity of Air Temperatu re F" C K (1~ 32 41 50 59 68 0 5 10 15 20 273 278 283 288 293 77 86 95 104 113 25 30 35 40 45 122 131 140 149 158 Absolute Vi,cO<Iity, Thermal Conductivity Oensity,Pf f.'t Se. Level 5,000 ft 10.000 ft 15.000 ft ~ 55.55 59.73 64.14 68.80 73.70 0.0415 0.0421 0.0427 0.0433 0.0439 0.0807 0.0793 0.0779 0.0765 0.0752 0.0671 0.0660 0.0648 0.0636 0.0626 0.0554 0.0545 0.0535 0.0526 0.0517 0.0455 0.0447 0.0439 0.0431 0.0424 0.00739 0.00750 0.00762 0.00773 0.00784 298 303 308 313 318 78.86 84.29 89.99 95.98 102.26 0.0444 0.0450 0.0456 0.0461 0.0467 0.0740 0.0728 0.0716 0.0704 0.0693 0.0616 0.0606 0.0596 0.0586 0.0577 0.0508 0.0500 0.0492 0.0484 0.0476 0.0417 0.0411 0.0404 0.0397 0.0391 0.00795 0.00807 0.00818 0.00830 0.00841 50 55 60 65 70 323 328 333 338 343 108.85 115.74 122.96 130.52 138.41 0.0473 0.0478 0.0484 0.0489 0.0494 0.0683 0.0672 0.0661 0.0652 0.0643 0.0568 0.0559 0.0550 0.0542 0.0535 0.0469 0.0462 0.0454 0.0448 0.0442 0.0385 0.0379 0.0373 0.0367 0.0363 0.00852 0.00864 0.00875 0.00886 0.00898 167 176 185 194 203 75 80 85 90 95 348 353 358 363 368 146.66 155.27 16426 173.63 183.40 0.0500 0.0505 0.0510 0.0515 0.0521 0.0634 0.0627 0.0616 0.0608 0.0599 0.0527 0.0522 0.0513 0.0606 0.0498 0.0436 0.0431 0.0423 0.0418 0.0412 0.0358 0.0354 0.0347 0.0343 0.0338 0.00909 0.00921 0.00932 0.00943 0.00952 212 100 373 193.57 0.0526 0.0591 0.0492 0.0406 0.0333 0.00966 *Degrees Fahrenheit. absolutt! viscosity, Ib/(hrl(ftl. Pf = density. Ib of air/ftl. '" = thermal conductivity of air. watt,/{sq ft)(C) at 'ta ambient temperature C. tc "'" conductor temperature C. IJj = ~ = (" + t,)/2. Source: "Current Carrying Capacity of ACSR." H.E. House-P.O. Tuttle, AlEE Transactions, Paper 58-41, 1958. 13-65 bus conductors Table 13-28 ( I1t)0.25 Physical and Electrical Propenies of urge Diameter Round-Tube Bus Conductors, 6l01-T61 1. Ampacity values calculated from House-Tuttle for We = 0.027 Pc \L Po = LHI + LVI + LV2 = 6.75 in. mulas. 2. Example (Refer to Ampacity discussion) 8 in. 0.0. by 0.500 in. wall. 6101·T61 indoor service. e = .35 LV2 where 0 = 8 in .• te = 70°C, ta = 4O'C We = 0.072 x (8)0.75 x (70 - 40)1.25 = 24.046 1 Wr = 0.138 x 0 x e r(K L\IO~ T )4 LW + 1.685 313° K, e = 0.35 95.98J t. = 40·C 30 ) 0.25 We = 0.027 x 6.75 ( 1.685 x (70·40) = 16.395 1= ( LV 1 +LV2 = I1t = 30 where 0 = 8 in., Kc - 343° K, Ka Wr = 0.138 x 8 x .35 [138.41 1 = )112 11.23 watts/ft. Rae at 70'C Rac 70°C from table = 1.59 x 10"-6 1= 40.441 y!2 ( 1.59 x IfJ6) 5.043 amperes P r = total exposed perimeter (13 in.) Wr = 0.0439 x 13 x .35 (138.41 - 95.98) = 8.48 wattslft. Table 13-31 1. Xa values from work by W.A. "'i.W = 11.23 + 8.48 = 19.71 Lewis for Alcoa. 2. Outdoor ampacity from IEEE paper by Prager. Pemberton, Craig. Bleshman (22) 1= 3. Indoor ampacity based on formulas developed by House·Tuttle and verified by extensive tests. = Example: 3-114 in. x 3-1/4 in. x 1/4 in. UABC, 6101·T6 Indoor service, e = .35, Rae at 70·C = 11.47 13-66 ( = 1.311 rounded to 1,300 19.71 y!2 \1l.47 x IfJ6) bus conductor design and applications Table 13-32 Convection Loss (Free Air) Properties oj Integral - Web Channel Bus Conductors l. Xa values from work by W.A. Lewis for Alcoa 2. Ampacity based on formulas developed by House Tuttle. Indoor values based on tests data. Typical con ductivity used because of better correlation with test points. Test work needed for outdoor values since it is not known how wind would affect this shape. How ever, it appears from theoretical studies that the results may have an accuracy of ± 100/•. J( 6 in. x .0550 in., ventilated, 30°C rise over 40°C tL At = te - ta in degrees C = 70 - 40 = 30 L Example: 6 in. (At) 0.25 We = 0.026 Pc L= Radiated Heat = + height HxW H+W = - width 36. - . = 3.00 12 eo 1°. 25 Wc 0.026 x 24 3.001 x (30) where Pc = nominal perimeter-inches where: P r exposed perimeter in inches 33.29 watts/ft. = (2 x heights + 2 J( width) e = emissivity Test showed value of 0.47, combination of surface and slots for new bus. . ~W )112 I = (Rac at 700C 0.35 is conservative. where Rae at 70°C = 15.65 watts/ft. 1.82, typical (15.65 + 33.29) 112 1.82 J( 10-6 = 5,186 rounded to 5,190 amperes bus conductors APPENDIX 138 Bibliography General Design for the Chlor-A1kali Industry," Electrochemical Technology, Vol. 5, No. 3-4, March, April 1967. A1ean Aluminum Bus Conductors, Design Manual Aluminum Company of Canada, Ltd. Alcoa Aluminum Bus Conductor -Aluminum Company of America. Handbook Kaiser Aluminum Bus Conductor Manual - Kaiser Aluminum & Chemical Sales, Inc. Reynolds Aluminum Bus Conductors, Brochure Reynolds Metals Company. Aluminum Busbar, Thomas, A.G. and Rata, P.J_H. -Northern Aluminum Company Ltd., London. L'Aluminium Dans Les Postes Exteriurs de Transfor mation - L'Aluminium Fran~is, Paris. Aluminum Busbars - Swiss Aluminum Ltd., Zurich Aluminum in Busbars and Connections, The British Aluminum Company, Ltd., London. Aluminum Electrical Conductor Handbook. 1982 - The Aluminum Association, Washington, D.C. Higgins, Thomas James, "The Design of Busbar In dustrial Distribution Systems: An Epitomization of Available Data," 1945, Technical Paper 45-25. Deans, W., "Electrical Buses and Bus Structures," Bulletin 4211 of ITE Circuit Breaker Company, 1942. "Use of Aluminum for Substation Buses," IEEE Trans. Vol. 5-82, pp. 72-79. 3. Arnold, A.H.M., "The Alternating-Current Resistance of Hollow, Square Conductors," JIEE Vol. 78, 1936, pp. 580-593. 4. Dwight, H.B., "Electrical Coils and Conductors," McGraw-Hill Book Company, 1945. 5. Mak, S.T. and Lewis, W.A., "Alternating Current Distribution in Parallel Conductors of Arbitrary Cross Sectional Shape," 1973, IEEE Conference Paper C70169.0. 6. Arnold, A.H.M., "Proximity Effects in Solid and Hollow Round Conductors", JIEEE Vol. 88, 1948, pp. 349-359. 7. Sigg, Hans-Jurg and Strutt, Max J.O., "Skin Effect and Proximity Effect in Polyphase Systems of Rectangular Conductors Calculated on an RC Network." IEEE Trans. Vol. Pas-89, No.3, 1970, pp. 470-477. 8. Fisher, L.E. and Frank, R.L.. "Paired-Phase Bus Bars for Large Polyphase Circuits," AlEE Trans. Vol. 62 (1943) pp. 71-77. 9. Paschkis, V. and Persson, J., "Industrial Electric Furnaces and Appliances," (book), Interscience Publica tions (1960). 10. Perry, John H., "Chemical Engineers Handbook", McGraw-Hill Book: Company, 1950, Chapter-Heat Transmission by Conduction and Convection. Numbered RelerenteS II. Swerdlow, Nathan and Buchta, Marion, "Practical Solutions of Inductive Heating Problems Resulting from High Current Buses," AlEE Trans. Vol. 78, pp. 1. IEEE, "Guide for Design of Substation Rigid-Bus Structures." . 1736-1746, 1959. 2. Guess, L.T. and Crow, C.K., "Advances in Bus 13-68 12. Skeats, W.F. and SwerdlOW, Nathan, "Minimizing the Magnetic Field Surrounding the Isolated Phase Bus by bus conductor design and applications Electrically Continuous Enclosures," AIEE Power Ap paratus and Systems, Feb. 1963, pp. 655-666. 13. Killian, S.C. "Induced Currents in High-Capacity Bus Enclosures," AlEE Trans. Vol. 69, 1950, pp. 1388-1395. 14. Maxwell, J.C. "A Treatise on Electricity and Magnetism," (book) 3rd Ed. Clarendon Press, Oxford, England, 1892. 15. Schurig, O.R., "Engineering Calculation of In ductance and Reactance for Rectangular Bar Conductors," General Electric Review, Vol. 36, No.5 (May 1933). 16. Lewis, W .A., "Transmission of Electric Power," Litho Ed., Chicago, Ill., Illinois Institute of Technology, 1948. 17. Carlson, C.L. and Van Nostrand, R., "Ampacities of Copper and Aluminum Bus Bars," IEEE Paper F 76-()8()..2, January, 1976. 18. Melsom, S.W. and Booth, H.C., "Current Carrying Capacity of Solid Bare Copper and Aluminum Conduc tors," JIEE Vol. 62, pp. 909-915. 19. House, H.E. and Tuttle, P.O., "Current-Carrying Capacity of ACSR, " AlEE Trans. Paper 58-41, February, 1958. 20. McAdams, W.H .. "Heat Transmission," (book) McGraw-Hill Book Company, New York, 1954. 21. Schurig, O.R. and Frick, C.W., "Heating and Current-Carrying Capacity of Bare Conductors for Out door Service," General Electric Review, Vol. 33, No.3, March 1930, pp. 141-157. 22. Prager, M., Pemberton, D.L., Craig, A.G., and Bleshman, N., "Thermal Considerations for Outdoor Bus Conductor Design," IEEE Trans. Power Apparatus and Systems, Vol. Pas 90, No.4, pp. 1361-1368, July/August 1976. 23. "Busbar Current Capacity, Paint Treatment and Its Effects on Cooling," Electrician, Vol. 126 (March 21, 1941) pp. 178. 28. Taylor, D.W. and StuehJer, C.M., "Short Circuit Tests on 138 kV Buses," AlEE Trans. Vol. 75, 1956, pp. 739-741. 29. Milton, R.M. and Chambers, Fred, "Behavior of High-Voltage Buses and Insulators During Short Circuits," AlEE Trans. Vol. 75, 1956, pp. 741-749. 30. Moorer, S.D., "115()"230 kV Bus Design Practices with Emphasis on Short Circuit Requirements," Trans. & Substa. Committee, Southeast Electric Exchange, October 21, 1965. 31. Schurig, O.R., "Fault Voltage Drop and Impedance at Short Circuit Currents in Low Voltage Circuits," AlEE Trans. Vol. 60 (1941), pp. 478-486. 32. Woodruff, t.F., "Discussion on the Natural Fre quency of Bus Bars," AlEE Trans. 1923, p. 568. 33. Den Hartog, J.P., "Mechanical Vibrations," (book) 3rd Ed., McGraw-Hili Book Company. 34. Tanberg, R., "Stresses in Bus Supports," Electrical Journal, Vol. 24 (October 1972), pp. 517-524. 35. Brenner, M., "Basic Principles to Support Aluminum and Copper Buses," Electrical World, July 1953, pp. 118-119. 36. Papst, H.W., "Stresses in Bus Bars and Design Features to Meet These Stresses-the Spring Mounted Bus," Westinghouse Electric Corp. Bulletin, 1933. 37. Grier, L.N. and Guess, L.T., "Suspended Buses Carry Heavy Current," Electrical World, Vol. 116 (1941) p. 1889. 38. N.T. Bond, "Aluminum Contact Surfaces in Elec trical Transition Interfaces." Proceedings of the Holm Seminar on Electrical Contacts 1968, pp. 13-25. 39. N.T. Bond, D.L. Robinson, and M. Mohajery, "Fundamental Consideration of Aluminum Electrical Contact Interfaces," Electrical Contacts 1977 Proceedings of the Annual Holm Conference on Electrical Contacts, pp. 213-222. 40. J. R. Greenwood, "Area of Contact Between Rough Surfaces and FaIts." 24. Fugill, A.P., "Carrying Capacities of Enclosed Buses," Electrical World, Vol. 99 (1932), pp. 539-540. 41. Holm, Ragnar, "Electric Contact Handbook," 3rd Ed., 1958, Springer-Verlag, Berlin. 25. IEEE Committee Report, "A Guide for Calculating Losses in Isolated Phase Bus," presented IEEE New York Meeting, 1968. 42. N.F. Mott, "Theory of the Formation of Protective Oxide Films on Metals-II," Transaction oj the Faraday Society, Vol. 36 (1940) pp. 472. 26. Tripp, W .A., "Forces on Conductors During Short Circuits," Electric Journal, Vol. 34, (Dec. 1937), pp. 493-497. 27. Killian, S.C., "Forces Due (0 Short Circuit Oments," Delta-Star Magazine (January-February 1943). 43. S.W. Melsom and H.C. Booth, "The Efficiency of Overlapping Joints in Copper and Aluminum Bus Bar Conductors," Journal ojInstitute ojElectrical Engineers, Vol. 60, No. 312 (1922). 13-69 and Calhoun. 59. Nathan. 1724-1730. "Development of a Welded Aluminum Bus for Substations. April 1967. AlEE (March. 1968. Asbury. "Aluminum Conductors in Electrolysis Installations and Electric Furnaces.1. Massey." IEEE Trans. Weber. "Design and Specification Considera tions for Construction of Large Industrial Rectifiers and Their Associated Facilities.H." L'Aluminum Fran cais. Vol. 4-9. IA-11.C. Donati. Wilhoite. McGeary." Vol.L.B.." AlEE Paper 63-101. 9-14. Amado and Harris.M. "Aluminum Angle Substation Bus Conductor. "Bibliography of Gas Insulated Substations. W. on Industry Ap plications. December 1978. C.. D. pp.. S.93-98. pp. Shand. F. Roanoke. 57... lohn R.5 47.J. 48. Vol. ANSI Standard C37. H. 1622-1628.K.C. pp.. Pas 87.. No. "Isolated Bus Enclosure Loss Factors.B.. and Large Substa...7. "Design Criteria for Integral Web and Universal Angle Buses. 99. L. C.E.M." Ref: IEEE PCI-76-52. 58-63. p. E. 375-387. 46. Bond. 63." IEEE Conference Paper T&S pp. Paris. Milton. . 51. pp.M.. "Electrical Transition Interfaces at Aluminum Terminations.23 52. No." Proceedings of the Conference on Electrical Utilization of Aluminum. a." Fasteners. 27 (December 1949). R. Vol. E. a. and Valentine. St.8. March-April 1975. "Improving the Capacity of a High Current D-C Bus. Interscience. H. 2. "Nickel Plating for Improved Electrical Contact to Aluminum.T. 61. 62.B.C. 49.. Pas 87. Fossum. and Swerdlow. N." Proceedings of the Conference on the Electrical Utilization of Aluminum AlEE (March 1955) pp.. 1963." IEEE Pas Vol. "Integral Web Channel Bus Con struction IEEE Trans." Elec tric Light and Power. 55. Hagemoen. Elgar. Christensen. 397-380. 53. 33.2.T. Con ference Record 76CHlI09 8-1A. "Belleville Spring Washers. T. Frothro.H. A. 433-440. "Measured Losses in Isolated-Phase Bus and Comparison d-70 with Calculated Values." L'Energie E1ectrica. N. No.6 (June 1935) pp. Rene. "Welded Aluminum Bus in Outdoor Transfer Yard of the Sewaren Generating Station. I. pp.W. 9. No." IEEE Vo. 389. Gerald.. Vol. 60... 1955) pp. "Overlapping Joints in Electric Furnace Circuits. No. 1963. 12. "Bolting of Busbar Joints. 54." Electric 10urnal (September 1933). R... E.J. Committee Paper. Ray. Rois.bus conductors 44. VA. "Extractive Metallurgy of Aluminum. Clair. 1968. and Hartmann. 45." Conference Record of the 1968 Second Annual Meeting of the IEEE Industry and General Applications Group. 1. Bond and F." IEEE Vol. Stewart. Conangla. No. 58." AlEE Conference Paper CP-58-1286. I. C. 1958. "Rigid Bus A-Frames. Rehder." Electrical Contacts 1978 Ninth International Conference on Electric Contact Phenomena. Quick. "Aluminum Bus in High Voltage Substations on the Philadelphia Electric Company System. 56. 50.. R. pp. Because vibration from dynamic imbalance is 14-1 . 4 through No.000 psi for annealed copper. especially coils. and motors in portable equipment or in air-borne. However. taped conductor can have a higher temper which results in much higher tensile and yield strengths. in order to achieve better space factors. the first use of aluminum mag net wire was as a filtn-insulated round wire. but there is a substantial demand for commercially available alloys possessing higher yield strength whlle maintaining con ductivity of 61 percent as a minimum. Taped conductors also have greater resistance to mechan ical stresses and abuse.703 grams per cubic centimeter' at 20 0 C has less than on'e-third the density of copper and weighs one-half as much as a copper conductor of equal resistance and equal length. designed now exclusiv~ly with round aluminum insulated wire. an anodized film was used as turn insulation. fractional horsepower motors. On balance. started to evaluate aluminum in the insulated cable field. Many of these applica tions can be served by 1350 aluminum. have about 3"l.Section V Electromagnetic and Other Electrical Applications of Aluminum Chapter 14 Aluminum Magnet Conductor During the 1950-1960 period when aluminum conduc tors began to displace copper in overhead transmission and distribution and a large effort was. are. T~pe-lnsulaiedalufninum. usually has a higher tensile strength due to the tape. with a density of 2. Certain small. Rectangular! As previously indicated. This is because the eddy current losses are an inverse function of resistivity of the conductor. the greatest increase in growth has been in the use of rectaIl>JUlar al1d square >~uminum magnet wire in distribu tion. class 130. class 155 and class 200. low mass simplifies dynamic balancing. In transformer practice. The lower mass of aluminum designs results in lower inertia~improving performance of a wide variety of equipment. thermaUy upgraded paper and crepe paper. The lighter -weight conductor is of advantage in most electrical equipment for transformers. In rotary equipment. Film-insulated conductors must be processed through a curing oven which results in total or partial anneal of the wire. Conventional aluminum magnet wire possesses a num ber of advantages over copper in both economic and tech nical aspects. at almost this same time it became apparent that thin aluminum strip conductor in the form of anodized foil or foil interleaved with a suit able insulating film would eliminate many of the magnet wire problems previously experienced. mainly in the was~er and dryer appliance field. lower stray losses. This advantage for aluminum is offset by the fact that larger conductor sizes are needed for equal resistances. aluminum conductors have lower stray losses than copper conductors for a given size. missile. However. Results from an eco nomic viewpoint were only moderately successful and. This type of conductor is now available in virtually all AWG sizes as it is for copper magnet wire (No. both bare and tape insulated with Aramid. alu minum windings. size and shape. Since annealed 1350 aluminum has a tensile strength of 12. 26 or finer AWG) and with all conventional insulation including class 105. Square. Light Weight Aluminum. small power and dry type transformers•. coil winding operations must be modified some what but once the necessary adjustments have been made aluminum magnet wire may be handled readily and rapidly. in comparison to film-insulated aluminum of the same temper. making them easier to wind and more resistant to the effects of electrical short circuit forces at elevated temperatures. Generally superior performance can be expect<:4· when aluminum magnet wire is used for rotating anli other moving windings. with resistances equal to copper wind ings of similar design. Therefore.000 psi as compared to 35. Aluminum Magnet Wire (Round. The subsequent de velopment of aluminum foil or strip magnet conductor has successfully achieved a new order of improvement in electromagnetic coil design. some attention was also directed to aluminum magnet wire. or space-vehicle applications where reduced component weight allows vital additional payload. These early efforts were confined to round 1350 aluminum wire in the fully annealed or partly annealed condition using conventional and new magnet wire insulations. manufacturers can realize sig nificant improvements in product cost control. aluminum film-insulated round magnet wire costs less per unit of length than its equivalent copper conductor. In changing from copper to aluminum. In the size range No. redesign of transformers and similar apparatus using scrapless laminations will usually involve one or two kinds of changes. rather than the rule-of-Ihe-thumb two sizes.. The mechanical properties of insulation on thermally aged magnet wire show a marked advantage for aluminum. Apparatus with Wound Cores: For apparatus using wound rores the procedure is nearly the same as for scrapless lamination. designers have used these advantages (higher temperature operation and good mech anical properties after aging) for both economic and space reasons by using aluminum magnet wire only one or one-and-a-half sizes larger than copper. The most striking aspect of this lower spring back is re duction in winding tension. Economic Factors Through lower initial cost and other savings due to aluminum's advantages. Because aluminum has a lower conductivity than copper. Fig. developed an entirely new design.1 Principles for Temperature Limits in the Rating of Electric Equip. little strain energy is required to conform it to an arbor. it is discovered that an existing unit allows sufficient space to accommodate the larger aluminum coil without any major revisions. considering the moderate increase in cost for special core deSigns." 14-2 Insulations applied to aluminum have longer life at the same operating temperature than the same insulation ap plied to copper. but some allowances do have to be made. Coil Design Engineering with aluminum magnet wire is not different fundamentally from engineering with copper wire.electromagnetic and other electrical applications of aluminum TABLE 14-1 Springback Comparison Chart Wire Size (AWG) AWG 18 AWG16 AWG14 1 Degree of Angular Springback* (Typical figures) Copper I Aluminum 38° 54° I 46° 32° 3S" 26° I I I I *' In '''degrees per turn" when tested per NEMA publication MW-lOOO!l961 Part 3. Significant weight reductions of coils can also lower shipping and handling costs. Table 14-1 presents some comparative springback data provided by a manufacturer of maguet wire. These savings run from 15 to 25 percent and more in the heavy gauges. a class 105 insula tion for copper can be used as class 130 insulation for aluminum. where electrical losses are not a problem. April 1969. Lower mass also results in higher sensitivity and re sponse in moving coil applications.g. Operators have no problem threading machines or advancing the wire. 2."Gener.5. 24 AWG. Even though aluminum wire may be two gauges larger than copper. Dramatically lower spool weights reduce operator fatigue by making it easier to load the winding machines. this family of electrical de vices yields the greatest return when completely new de signs are used_ Optimum desigus for aluminum wire require different . designers often must find space to increase the wire gauge by two sizes. some engineers may prefer to develop an entirely new coil design. Par. Thermal Characteristics Tests indicate that insulations applied to aluminum can be expected to operate one IEEE temperature classifica tion' higher than the same insulation applied to copper. reduced. for example. and they readily handle aluminum wire four sizes larger than the largest copper gauge they can han dle. If the designer must change lamination size. all coils are more compact.8 AWG through No. 14-1 was provided by a manufacturer of aluminum magnet wire and gives data on the aging of aluminum vs. aluminum construction contributes to longer operating life of rotary apparatus.rds Pub. however. end turns on a motor stator are shorter.1. No. distribution transformer primaries). Sometimes modification of existing designs will be sufficient.2. Windability Because annealed aluminum magnet wire has a low yield strength (approximately 4000 psi). Usually. Manufacturers can take advantage of this characteristic in the design of electrical instruments and acoustical devices. in effect. and op erator fatigue is reduced in hand winding operations. In certain applications. for optimum re sults it is necessary to redesign the unit (e. This quality is noticeable in practice: rectangular coil sides have less bow than similar copper coils. Some times. machines run faster. Apparatus with Stamped Laminations: When there is in sufficient space for an easy substitution of aluminum for copper. However. and still have equal life. copper magnet wire insulated with a variety of materials. It may be necessary to increase stack height to accommodate an aluminum coil of fewer turns of large wire. • IEEE Stand. or a different lamination may be necessary. he has. As with transformers. the designer can employ previously wasted space to accommodate windings even though it may alter the basic shape of the coil. Sometimes. Motors: Many classes of motors lend themselves readily to redesign with aluminum magnet wire. aluminum coils still have longer life than copper coils. Bars in gray indicate aluminum life. Such a design. is most practical with tape-wound cores. Means of Minimizing Coil Size: In copper-wound electro magnets. and a window length 1Y. if only slightly. Coils can be precision wound instead of random wound. times window width. Bobbins can be made smaller-some times they can be eliminated altogether. Often overlooked are the opportunities to modify exist ing windings. to take advantage of alumi num magnet wire's economic benefits. which constitutes a complete departure from standard practice. it must he provided by modification or redesign on the entire device. stack height 2 to 2Vl times core width and the window length 2 to 2Y. There are various measures available for minimizing size of wound coils. as a result of a thoroughgoing redesign par ticularly of an older item in a product line. and the pole-piece diameter can safely he reduced by 10 to 15 percent. In the finished product. shaded pole types often have sufficient space for an easy substitu tion of aluminum. the same information applies to all other magnetic devices which a designer wishes to con vert to aluminum windings.. aluminum-coil weight would be approximately 40 % of the total. the new device and its aluminum coil may operate cooler. Coil operating temperatures can be raised--with moderate temperature increases. This approach of reducing the inside diameter of the coil is better than increasing the outside coil diameter because it lowers the mean turn length while it provides the extra space required for larger gauge wire. coil weight is about 33 % of the total. 300f~- Fig. the window area is approximately 75% greater than core area. stack length can be increased or a larger lamination can he used.. Induction motors may have space for a change in wire size of one or one-and-a-half gauges. In the finished product.aluminum magnet conductor '" ~ 700~--------------i----- ~ ~600~-------------1---567 . This change together with shortened end turns may be sufficient for a simple substitution. Other Devices: In general. 14-1. core dimensions than are used with copper. the design flux density of the pole piece is often conservative. But for aluminum. Thermal aging of 1350 aluminum and copper magnet wires with various enamels. only one additional tum per layer or special contouring of the winding to fit special cavities will use a space for maxi 14-3 . In particular. stack height I Y. times core width. SOOt-------1-t ~ : t:! 400r---- ::. Finally. A typical cop per design has a window area one-half of its central core area. Such a design probably is very close tQ minimum material costs. times window width. If the necessary extra space does not already exist. Through close at tention to coil confignration. inelastic and highly insulating film in the order of three ten-thousandths of an inch thick. technical data are included for both alloys and are compared to electrolytic copper. Aluminum can be soldered using the same tools and techniques as copper. A satisfactory film was obtained on straight conductor but bending sometimes resulted in crazing at . Early work was directed at anodizing round aluminum conductors. Top quality terminatiOns and splices are exceptionally re producible-and the resulting low rejection rate helps in crease output while reducing scrap costs. Aluminum Strip Magnet Conductor Strip conductor by definition is a fiat. A one-step. or by the deposition and bonding of in sulating coatings. by interleaved (wider) films of a variety of high grade in sulting materials. This mechanical connection has numerous features that make it more efficient and more economical than conven tional joining and termination methods. this thin layer can be expand ed into a hard. but requires special procedures and solder and flux. This anodic film is desirable in many applications because of its hardness. it is done in everyday production. Top quality terminations and splices are exceptionally reproducible. There's no damage to insula tion from heat. have proved this method to he highly reliable. stripper residues. All of these methods require some special treatment of the strip surfaces and edges. de veloped by the manufacturers.magnet conductor may be insulated:. 14-2. ma chine-applied process combines low labor costs with high production speeds of up to 4000 terminations per hour.by 14-4 Fig. Since cases of redesign for aluminum wire are highly individual. machine-applied process combines law labor costs with speeds 01 up to 4000 terminations per hour. Aluminum strip magnet conductor is usually made from either I3S0 grade aluminum or 1235 aluminum alloy. Al though 13S0 grade metal will be principally discussed in what follows. By the use of anodizing techniques. These methods employ machine applied compression terminals with serrated barrels. A one-step.electromagnetic and other electrical applications of aluminum mum ampere turns. high dielectric strength anodized films. Soldering: A secondary method of splicing and terminat ing is by soldering. Anodized Films: Early developments by the aluminum in dustry clearly recognized the possibilities of using anodic films for the electrical insulation of aluminum conductors. Strip Magnet Conductor Insulation Aluminum strip. The joining and termination of insulated aluminum wire-which has been a source of concern to many coil makers-can be easily done with mechanical connectors. Aluminum oxide exists to some extent on all aluminum in the form of a microscopically thin layer and provides aluminum with its excellent corrosion resistance. Information about pro cedures for soldering aluminum is available from various manufacturers on request. Millivolt drops and temperature rise are essentially the same as the hest of connections made carefully by other methods. Compression terminals for aluminum wire. some manufacturers maintain a coil-prototype laboratory to help customers with aluminum application designs by winding experimental coils and demonstrating techniques of joining. This mechanical connection has features that make it more e/ficient and economical thaJI conventiom!l joining and termination methods. A considerable number of environmental tests. Mechanical Termination: Mechanical termination and splicing methods have been developed which are highly effective and low in cost. or soldering fiuxes. abrasion resistance and high breakdown po tential for a given thickness and high temperature rating. a broad range of widths and thickneses are available. lIexible metal strip usually produced by slitting a supply roll of proper gage metal into required widths for the finished product. Coil Connections Joining aluminum coils to lead wires is not a laboratory curiosity. extremely thin. such as those shown in Fig_ 14-2. The resulting conductor has a rectangular cross-section with a large width to thickness ratio. Inferleaved In sulation: The thermal. The transition pieces are usually made by cold or flash welding. Teflon: Teflon has a thermal rating of 200 0 C per MIL-W-16878 . non-uniform edges. Of course. 155°C). Develop ments were directed toward anodizing a relativel y wid e and thin strip of aluminum having the same cross-sectional area as the round conductor. polyvinyl formal (Class A. It is used where dependability is an important factor. 14-5 . Paper : Paper has a thermal rating of 90 °C (Class 0) and I05 °C (Class A) or better when submerged in oil or impregnated. The width of the interleave is usuall y about 0. It is sometimes used without a binder. Polyester : Polyester interleaving materials have a thermal rating of app roximately 150°C which is between Class B. It has good abras ion re sistance and can be wound on automatic equipment. chemical and electric'a l requirements must be defined before an in terleaving material can be selected. 14-3. They have excellent dielectric strengt h. polyesters (Class F. It acts as a posi tive spacer and varnish absorbent." has a thermal rating of 200°C (Class K ).0005 inch have been used as turn insulation in electromagnetic coils wound with edge-conditioned strip con duc tor . The major limitation is its poor space factor. The bending problem was overcome by going 10 a strip. it is usually the interl eaving material used in oil-filled trans formers and in coils that do not operate above i05 °C. Epoxy (Class B. Teflon is more expensive Fig .) The use of this interleaving material is limited because it is a bulky insulation . this dimension may vary cons idera bly-depending on the interleaving material . Glass: Glass has a thermal rating of 2200 C (Class C) . but normall y it is impregnated with silicone or other resins which may limit the temperature classification . Glass is sometimes used as a backing for other interleaving materials to provide tensile strength . than most other interleaving materials which limits its major application to aircraft and missile wo rk. By utilizing a chemical and me chanical treatment of the ragged. polyester. Epoxy and polyamide-imide appear 10 be growing in favor. Mica: Mica has a thermal rating of 2200 C (Class C). It also depends on binder th erm al rating for its rating. M ica has good electrical properties but its tensile strength is low and it is bulky. The res ults of th e fabrication process for anodized strip are considerably improved insulation efficiency and overall strength. Polyester films are not compatible with some varnishes and are not gen erally recommended for use in oil-filled equipment. resistance to most chemica ls and sol vents and very hi gh tensile strength . mechanical. Paper and polyester interleaves as th in as . It has excellent thermal endurance. actS as a positive spacer an d is able to withstand the elements that deteriorate other insulations. Silicone. An aluminum to copper lronsiaon piece may be used to make aluminum to aluminum connection at the strip and /0 make a copper connection to a lead or termi nal. Because it is able to withsta nd large com pressive forces and has good dielectric strength . It is available in thicknesses of 2 mils and over.) It is very resistant to abrasion and has good chemica l resistance and good dielectric strength. Coated Strip: Coated aluminum strip has also been de veloped for use in commercially available distribution transformers. 155°C. (Teflon backed up by glass cloth to prevent cut-through has a much higher rating tha n 2OO 0 C. but the edges were almost impossible to anod ize. 135 0 C). Under certain electrostat ic condi tions they have a tendency to attract foreign matter whi le being wound.aluminum magnet conductor the outside radius of the bend and an actual extrusion of metal throu gh similar cracks on the inside radius . (Lower thermal varnishes like epoxy bring the thermal rating down. 130°C and Class F . 105 0 C). such as DuPont " Nomex . the coil and the equipment used to wind th e coil. Asbestos : Asbestos treat ed with silicone or other high temperature varnish has a thermal rating of 2200 C (Class H) . a surface that could be anodized adequatel y was obtained.125 inch wider than the strip. Aramid : Polyamide. epoxy and other varnis hes are ge nerall y used to treat the asbestos fibers. and the amid-imide polymer enamel coatings (2000 C +) are used. Coil Design with Aluminum Strip Magnet Conductor Aluminum strip magnet conductor can be designed into most electromagnetic devices when all of the parameters of the device as weI! as the characteristics of aluminum are taken into consideration. Betler short-circuit performance in transformer since each tum is centered in the magnetic field. It is noted that.aluminum magnet conaudar layer Insulation Core Insulation Magnet Wire Insulatian COPPER WIRE Conductor Conductor Space Fodor -approximately 60% Interleaved Insulation of window opening EDGE-CONDITIONED ALUMINUM STRIP CONDUCTOR Conductor Conductor Spoce Insulotion Faclor up to 90% of window opening Insulation Between Windings Fig. 5. 14-4. Strip made of electrical conductor grade aluminum 1350 has a guaranteed conductivity from 61 to 62 percent lACS. This is graphically shown in Fig. This. 14-4. 3. the aluminum strip conductor will utilize more of the allocated coil space than the equivalent round wire. Elimination of hot spots. Because of its geometric shape. for the same coil "window" 14·6 opening the utilization of space by the conductor is much greater in the foil or strip form than for the usual insulated round shape. Therefore. therefore. In addition to better space utilization. Lower voltage stress between turns-tum voltage gradient is layer voltage gradient. More rigid construction results in greater strength. . 7. 1350 aluminum strip conductors designed for equal direct current (DC) resistance compared to a copper conductor must. Better heat dissipation-each tum is exposed to the outside and in fiat surface contact with insulation of the next tum. Space comparison of coil wound with round mog71etwire and strip conductor. Less supplementary insulation necessary. have a larger cross-section area. No side supports are necessary for the strip wound coil. in large part. Easier windinrno traverse guiding necessary. space conserva tion must be employed in designs where dimensions are critical. is due to the elimination of need for the wire insulation. 6. 4. strip conductor offers the following advantages: I. This meanS that the aluminum strip condUctor will re quire about 60 percent more space than is needed for an equivalent copper conductor. 2. These are but a few techniques the designer has at his disposal to arrive at the proper coil design. at lO°C Wxt (Eq. Coils containing two or more windings that must be bal anced in impedance can be wound bOOar. 14-5 provides a ready means for determining strip dimensions and also the corresponding dc resislance per 1000 ft. at 20'C.25947 dc resistance. is placed to the outside of the coil. Coils can be wound on a round mandrel then formed into rectangular shape. The per unit cost of conductor increases as the size decreases. This ability to post-form coils after winding allows the designer more flexibility. the conversion to aluminum strip conductor for an approxi mate equiValent coil is simple.omsat W xt (Eq. The cores can then be electrically paralleled with the same results as obtained with a coil of thinner.3 A 2. wider strip conductor. ohms 11. Ib per 1000 ft 1173 X A 3854 X A Length. If the round copper wire size used in a coil is known. These formulae generally yield accuracies between -4"1. which is the lower cost. The following example illustrates tbe ease with which aluminum strip conductor can be sized for an equivalent round copper wire wound coil: *RevJre Genera/e de I'Elecln"dte. therefore. The smaller winding of the primary con taining many turns can be located next to the core where the mean turn length will be minimized. Since they are for approximation of inductance. I 38(MLT)N x 10. are now wound with strip conductor and used in many different types and sizes of motors and generators. This is ad vantageous because round coils are more easily adapted to winding on automatic high speed machines than are rectangular coils. This area of aluminum conductor is then dimensioned to obtain the required thickness and width. with the conductors of each winding physically paralleled and wound together with proper insulation between. depending on the coil dimensions. advantageous to control the amount of smaller conductor used on a coil assembly. 14-2) Ohms per 1000 feet is calculated as: 3 RlOOO = 13.138 X 10.ohms/lOOO ft.to adapt strip con ductor to coils previously wound oniy with round insu lated wire. The higher cost thin gauge conductors can sometimes be economically replaced by strip of heavier gauge and nar rower width.1455 X 10. Fig. 14-7 .6 A A2 per Ib A 8. 14-1) A 0 Where: P = microhm-inches resistivity of 1350 P = 1. Determination of Foil Size and Coil Challlcteristics Direct current (dc) resistance of the aluminum strip magnet conductor coil can be determined by using the following fonnula: = Px 12(MLTJN x 10-6 hms (Eq. 99. Coils for field windings of rotating equipment. 6 h lOoC R w= 13. It is. Pg. that is. 14-3) Inductance values for strip magnet conductor coils can be determined approximately by using conventional formulae for round wire wound coils.3 dc resistance. Tests performed to date indicate that inductance values for coils of the same number of turns and of the same shape and size will be approximately equal regardless of conductor shape. for example.85336 A 0.138x 10.212 X 10. The cross sectional area of the round copper conductor is increased by 64% to ob lain the required cross sectional area of aluminum for equal dc resistance in a coil having equal length. This approach also decreases the amount of insulation required. Tome LXUl No. The amount of smaller conductor is kept to a minimum and the larger conductor of the secondary. Bunet> gives formulae for round and rectangular shaped coils of round wire Which are beyond the scope of this work. ohms per 1000 It 13.7"1. and + 4. they suffice for engineering needs and can be used for strip wound coils as mentioned above. The close coupling of the flat conductors results in the best possible balance in impedance between these windings.alvminvm magnet condvctor Winding Design Techniques With Strip Magnet Conductors Many techniques can be employed. January 22.4. Bunet. ft per Ib 0.1135X A2 to·6 'Based on alumin~m at 62% conductivity where: A=nominal CrO$s~sectionaj area of the wire in square inches. 1938. The narrower coils can be wound and placed side by side on the core to utilize the available space. A transformer is an assembly where this design technique can be utilized. previously considered oniy for winding with round wire because of shape.09483 microhm-inches at 20 0 e ML T = mean lengih turn in feet N = number ofturns A = cross sectional area of strip in square inches = W x t (width times thickness) R w Then the winding resistance is: TABLE 14-2 Formulas For Calculating Weights And Resistances at 20" C I Aluminum' Copper Weight. . ....~" / V V V .2 V / _ ~..~O 0 10 -+ ~lUIMr'NI 1M I STRIIP C... LI-~ I I. !j1 '"....0 ..'lAU. v ~ /V /VJ':L7 ~/'V V L r 03 AIlEA SQ / V ~4~ . 1-1 ~~ ~ r< c--& - .<JI' II / V j( .5 ~ 1-- '1i 'r< r--C' r- II ~.:.. .6 0 0 -_ .~7 J V 1 01 . r[. "'". '~" v !'o/ / / ~:..l . " / 11 ~. . (Notes and data on Fig.~ K " 06 --6' .~ .--.c-1: 4 ..]' Lo . 7' / ~ . I I I I I·j-+!~l: = I I I I I . . 2 '> ---r" ~ 10t-100-t-:.... I II I I 34I I 32I I 30Io. ... .......++++++ U .. vt. .) 1. ~ III ..01 BI I 6I I 4I I 2I 36 AWG SIZES !.opOi28I I 26I I 24I I 22I I 20I 040' IBI I 16I I 14I I 12I I 10I 0.8 40 .. ...v o· v 1.' U / P Lt". ND. v vv It" v~ / I~ SHEET I I II I I 1-11. I COMPUTATION CHART I --l---+-I---I-+ -. 1 i ~'. 14-5.._~ is'' 1120 i 10 '" AO / V7 V ffl'\v VI VV JI I''/ / 7 / V / 'v __ __ .r I I I 1 I I I j _L 11 . v "" 7 _ Ii¥VI. I ~ ~ ...{..O.o/t..II - 0 .. L.Hrrrr ri T V/7 v. \)'. v v .. / V V / V V / V V __. 14-5 may be found on page following. <f>'V L..." 6<l r r I I..0 . 40 40 (".00001 .. - ~ "1'¥l- ~o . Aluminum strip conductor application...of}..y .0 I 06 I GAUGES ~ RES'STANCE-...( / V "H 015 INCHES / / "~' " &'.f4Lf vv !I'm~ v V I> I I I ~ /... 1-'" ..0~10 I :il 1..G'Skll '" 01 I 0)0 40I 0 2/0 Fig.. ~ It--+-J """"'0 Vv lty ."'hk' . "!j! 61-60-1. -"'0-" vV kXi~V "Offi" vV 7 7 ~~"'. UCTO~.APPLICATIONDIATfA. y _ • Htf11 ~±Bd t25< "o1~.- ~ • 011 100 1000 00001 0001 ao . '" 3 . - 7':)t:. in. the intersection of the lines corre sponding to a 3-inch width and a . per 1000 ft.1022 sq.08 ohms per 1000 feet by locating the inter section of the . = = normally used.. electrically equivalent to No. (r) (MLT) (N) 5. Resistance is determined by intersection of the . = number of turns of coil T = thickness of strip conductor in inches t = thickness of layer insulation in inches k winding space factor 0. As noted.. 17 AWG). the equivalent aluminum strip conductor will have an area of. 14·. Cooling ducts may be eliminated under certain conditions with significant cost savings.0033 thickness. Weight of Coil of N Turns W 1000 In the above formulas: r = resistivity in ohms/lOOO feet A = cross section areas in sq. 1648 square inch (. Two or more strips multiple wound may result in lower cost coils.. Density w= 1200A (Notes and data on Fig. From the chart a strip width of 1Jl inch requires a . The excellent heat transfer characteristics of strip wound coils result in lower average operating temperatures and in much lower hot-spot temperatures. FORMULAS FOR STRIP WOUND COILS 1. must have an area of . Resistance of Coil of N TUrns R=----:- 1000 Example. 14-5 computation chan. (w) (MLT) (N) A small solenoid coU is wound with 100 turns of No. Mean Length Turn of Coil MLT 12 N (T 4.handle two coils. approx. 110 AWO* square copper wire (.) and is 3 inches wide. conductor location for an actual case amply demonstrates this principle. Fig. since the lower cost of thicker strips and the elimination of almost 5007./lOOO feet = inside diameter of coil in inches d = winding depth of coil in inches D = MLT mean length turn of coil in feet r.1022/.1648 sq. in. Weight calculated by formula 2 is found to be 2 lbs. Common methods of joining such leads to the aluminum strip and for making aluminum to alumi num splices are: Coldwelding: Pressure welding at room temperature is an accepted method of joining aluminum strip conductor 14-9 .. The result is a compact coil with no air voids and a minimum of insulation.97 for typical foil wound coils with interleaved insulation R = resistance of coil in ohms at 25 cc W = weight of coil in Ibs. This resistance is found LO be 7.1648 square inch area gives a thickness of . area line and the resistivity line. inches w = density in Ib.00167 area line and the appropriate resistance line. Aluminum Strip. These leads usually are round copper wire or flat copper strip. -3. Joining Electrical connection of an aluminum strip wound coil to external circuits requires that a suitable lead be attached to the strip which can then be soldered or bolted into the external circuit. These reductions may be significant when the choice of insulating materials is considered. Based on an aluminum conductivity of 62 percent lACS.aluminum mognet conductor Strip Conductor Equivalents 2. d) used for obtaining approximate data useful Since the electrical conductivity of J 350 aluminum in this chart is 610]0 of copper. Dielectric and Thermal A dvantages of Strip Magnet Conductor Since a strip wound coil consists of a number of turns of film-insulated aluminum strip or strip interleaved with thin layers of strip insulation. the number of layers is equal to the number of turns and the layer to layer voltage is equal to the turn to turn voltage.62).. !9 AWG copper.00167 sq.imately 64% more aluminum by volume is re 3. of the insulation may more than offset the slitting costs and the additional labor to . and 3 wire sizes larger than square copper. This e1iininates the high !ayer to layer voltage common on cop per magnet wire coils and the expensive layer insulation >I< See ASTM-B324 for additional information on rectangular and square wires of aluminum.8 ohms per 1000 ft. The resistivity is found to be .5 preceding) The computation chart in coii design. 14-6 showing temperatures vs.055 inch. 6. Resistivity r= .(D .013118 A (Example continued from page 14-7) A coil is wound with 100 turns of No. J9A WG-enameJed round copper on a coil width of Vz inch. A useful rule of thumb is: for equal conductivity-use 2 wire sizes larger than round copper. Winding Depth of CoH of N Turns + t) K quired. -4 and -5 provide additional data and formulas which are useful in strip conductor wound coil design calculations. Tables 14-2. Slight adjustments may be necessary for choosing exact dimensions. From the Fig. The system is flexible since many arrangements of strip width and thicknesses may be used. inches (approximately No. average op erating temperature is reduced in this instance about 120 C and hot-spot temperatures are reduced approximately 40 0 C. )$ . Two methods are most commonly used: 1..electromagnetic and other electrical applications of aluminum 150 100 __ 8 50 --------------------------------------. C is a strip slit in four equal widths folded out individually-one on top of the other. or coated witb conventional film insulations and special high temperature types including anodized strip. Mechanical con nectors are available for joining solid or stranded wire leads to strip conductor. 14-3) may be used to make aluminum to alu minum connection at the strip and to make a copper connection to a lead or terminal. Abrasive means must be employed in pre-tinning the surfaces of the metals for subsequent soldering without fluxes. This is a particu larly fast method and is used for automatic set-ups. AMBIENT TEMP. (MIG) High Temperature Solder: Effective solder joints can be made without the use of corrosive fluxes. Com mercial equipment is available for joining a wide range of thicknesses and widths of strip conductor. o C (90) -Max. In Fig. operating temperature--copper B (96) -Normal operating temperature--copper Fig. both bare and insulated. 14-7. Cold-welding anodized aluminum to anodized aluminum. It is supplied bare for use with interleaving materials. (TIG) 14·10 2.008 inch and heavier can be supplied with a fully contoured round edge. Fold Out Parent Metal: The end of the strip may be slit or folded by various techniques and brought out at 90 0 to form a narrow laminated lead A flexible lead can then be attached by welding. by mechanical connectors. A tungsten electrode with the filler rod being fed by hand as in gas welding.. Mechanical loints: Use of mechanical joints in alumi num and copper has been successful when joints have been properly designed. The transition pieces are usually made by cold or flash welding. Ultra-Sonic Welding: Lap joints may be made between aluminum to aluminum and to copper by a vibrating tech nique to result in a metallurgical bond without the appli cation of heat. operating temperature--aluminum D (34) -Normal operating temperature-aluminum A (l30~Max.0959 inches. Magnet strip conductor is supplied insu . Transition Pieces: An aluminum to copper transition piece (Fig. Or by bolted connections. Riveted joints have been successfully used for years in the small strip conductor wound hom coil and the targer welder reactor coils..- ------~--~ to aluminum or copper in production..001 inches to . Heat transfer characteristics of aluminum strip conductor. Tests have proven that the joints formed by this method have high conductance and high strength. Magnet strip conductor from . The weld has 80-90% of the original strength of the parent metal. Shielded Inert Arc Welding: All types of inert gas shield ed arc welding which do not require a flux are acceptable for joining aluminum to aluminum. A consumable electrode of aluminum welding wire fed through the inert gas envelope. -_ . Strip Magnet Conductor Types Magnet strip is available in gauges ranging from . 14-6.. bare aluminum or copper requires no wire brushing of the aluminum sur face. 00161 .000322 .00647 .00407 .00129 . COPPER AWG WIRE SIZE 100% lACS 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 .that when a magnetic field varies within a turn or turns 14·11 .00264 .er gauge materials are edge treated by contouring process.000636 .00208 .000400 . Bare strip in thickness from . Adding turns also in creases the magnetic field.92680 .00132 .00656 .013138 Lll000A M=1.172XLXA L= N X MLT MLT=P+lTD/12 D = N(T + tf /. a magnetic field is set up within and around the turn. as speci fied by the customer.975 Strip width in inches T Strip thickness in inches t Interleave thickness in tnches N = Number of turns P :::.0759 inches. IN.00128 .01635 . Some Basic Considerations Relating to Aluminum Magnetic Wire When a current passes through a loop or turn of the electrical conductor.00259 .'. and the lighter gauges by electro~hemical means.01315 .000802 .00529 .00413 .00419 .00203 .000252 . IN.001 inches through .003 inches can be fabricated on special equip ment so that contouring is usually unnecessary for many applications.000620 .02091 . The magnetic field increases and decreas es directly as the current varies. SO.000627 .008155 .000645 . 1350-0 1235-0 62% lACS 61% lACS . .01659 . In this range.00256 .000317 .01686 .01060 .03380 .00323 . IN.01043 .00101 .001 to approx.00667 .00333 .02062 . aluminum strip magnet conductor is sup plied in widths ranging from 1 inch to 36 inches.000612 .00827 .000406 .000666 . the hea. The reverse of Ihis process is .000413 .000505 .00521 .01297 .00513 .00104 .00206 .Q1028 .000200 TABLE 14-4 Useful Formulas for Aluminum Strip Wound Coils Area Resistance @ 20' C Weight Length Mean Length Turn Winding Depth W A=WXT R = . Perimeter of core insulation in feet Square Inches Ohms Pounds Feet feet Inches ALUMINUM EOUIVALENT SO.000614 .00103 . In general.00166 .aluminum magnet conductor TABLE 14-3 Comparative Cross Section Area-Equal Volume Conductance SO.000327 lated only in gauges from .00841 .03325 .00327 .00163 .02637 .02126 .01337 . Fold out parent metal. by mechanical connectors. .. Coldwelding anodized aluminum to anodized aluminum. e = Ndq. Mechanical jOints. A flexible lead can then be at/ached by welding.the sharing of a resistor .. This action forms the basis of a fundamental law of electricity. there is induced in the conduc tor an electromagnetic force which will cause current to now if the turn is connected to a load . Commercial equipment is available for joining a wide range of thick ness and widths of strip conductor. Riveted joints have been successfully used for years in the small strip conductor wound horn coil and the larger welder . Tests have proven that the ioints formed by this method have high conductance and high strength.r'" " " I. inductor or capacitor. 14-4) N = number of turns d¢ time rate of change of nux (the magnetic field) di and e = L (Eq..-. C.N (Eq. Use 0/ mechanical joints in aluminum and copper has been successful when joints have been properly designed. dt where: (Eq. Electrical energy may be transformed from one circuit to another with possible change of voltage and isolation of the two circuitS by sharing of a magnetic field in which one component forms the magnetic field (must be alter nating) and the other has induced in it the electromagnetic force from the changing magnetic field. c Fig. A second . as follows: 14-12 I ( per requires no wiFe brushing 0/ the aluminum surface. The end of the strip may be slit or folded by various techniques and brought out at 90° to form a narrOw laminated lead. the applica tion of which underlies the design and operation of most electrical apparatus and circuitry. 14·7. ". Shown is a strip slit in Jour equal widths folded out individually-one on lOp of the other. The magnitude of the induced emf ( e) depends on two fundamental factors. ~ o0 I! C C C C & 0 C COG 0 nco 0 (l 0 [: 0 iI 0 II 0 ODD 0 C 0 a0 ~ j C 0 00 0 0 0 0 0 0 0 t O O t 0 Various methods of applying terminals to aluminum strip conductor. B. Mechanical con nectors are available for joining solid or stranded wire leads to strip conductor.electromagnetic and other electrical applications of aluminum ". Coldwelding. - . '..method of transforming energy is by direct coupling . ' ~ A B ... bare aluminum or cop of an electrical conductor. 14-5) dt dt L= coefficient of self inductance di time rate of change of current dt From (4) and (5) it is seen that: where: '" _ . -.11..(for a non-magnetic core coil) . Pressure welding at roam temperature is an accepted method 0/ joining aluminum strip conductor to aluminum or copper in production..eactor coils. or by bolted connections. A. 14-6) ." . This is known as mutual coupling. 225 0.8 x 10-6 = current in conductor For a coil with a magnetic core (iron) with permeability and reluctance R: and </> = -N R R = I _1_ pA Therefore: ¢ = N I pA I (Eq. 23.8x 10-6 To achieve a coil with high magnetic field capability and low cost. Improvements over the years have been (1) lamination of the iron to reduce losses.00410 0.09765 0.57 0. high current.6 x 10-6 16. amorphous internal structure (glass-like) promise a drastic reduction in iron losses for next generation coils and transformers.39 Temperature co-eff. (6) improved thermal dissipation for cooler operation. stability of the magnet wire insulation to allow more current to flow at higher temperatures. (4) improving the thermal. (5) use of rectangular wire and strip (interleaved) to gain in space factor.934 Co-efficient of thermal conductivityeal/seel CM2/CM/"C Co-efflcient of linear expansion per (> C Where: ¢ = flux or field I p.11277 0. 14-J3 . Other more recent advances in rapid-chilled iron with The conditions for a strong field are large number of turns. 1. (2) increasing the permeability of the iron. 2 15. weight.3 0.32117 Volume resistivity microhm in. Electromagnetic coils consist of coils of many turns of magnet wire (insulated conductor) wound around soft iron cores whose ends are connected in loops. 14-7) (Eq.214 0.00393 Specific heat ca!/gramt'c 0.55 0.092 0.65 31. no air gaps in iron path. 14-8) (Eq.Physical Constants at 200 C A1uminum 135~ Volume electrical conductivity minimum percent lACS 62 Copper 1235-0 61 Electrolytic 100 Density Ib. size.00403 0.67879 Weight resistivity microhm -lb.09765 0.!ft.aluminum magnet conductor TABLE 14-5 Strip Conductor Alloys .09482 1. if design permits.iin. and energy consumption has been the goal of designers since the time of Faraday who did fundamental work in the area of electromagnetic induction in the last century. 14-9) Where: A area of flux path in iron I = length of flux path in iron 23.40 15. (3) reducing the thickness of the magnet wire insulation and layer insulation to permit more turns per unit space.eient of resistance ohmfC 0. and use of high permeability iron. . Usually the induc tance is negligibly small as compared to the other factors.. a-c low voltage. the inductance is approximately the same as a wire loop equal in area to that formed by the two leads and the capacitor unit itself. unrolled foil capaci tor and its equivalent electrical circuits. All elec trical components used specifically as capacitors are looked upon as providing lumped capacitance. the charges are con centrated and this is termed a lumped capacitance.f fin Hz ginmhos Cin farads Lin becrys r in ohms or since g2 is usually very small compared to "PC'. The overall impedance of the equivalent network shown in Fig. Aluminum has been and is the preferred metal for capacitor electrodes whether used in rigid plate form or in varying thicknesses of foil for d-.. Equivalent Network of a Capacitor All capacitors possess a certain amount of series resist ance and inductance as well as shunt capacitance and con ductance. of course. elevators and x-ray apparatus and so on. How far one can go in these directions depends upon the circuit voltage to be withstood. impulse discharge.2 C' g2 +w'C' (Eq. Any arrangement of electrodes whatsoever upon which electric cbarges accumulate or move will exhibit the inci dence of capacitance.C -~~-+jwL g2 +. 15-2) 15-1 . physical and en vironmental factors. Actually. Where the electrode geometry is extensive in space such as a wire or cable.. The equations for capacitance relating to a wide variety of electrode geometries were given and the nature of the dielectric polarization of the insulation discussed. the conductance and!or dielectric loss that can be tolerated and the stability of the assembly under the operating conditions. Chapter 8. a capacitor may be called upon to pro vide a precise amount of capacitance. high frequency. The selection of electrode and insulation materials and the design of their electrical and mechanical arrangements can be optimized to produce an economical capacitoI" that will perform properly in its intended service. shape and extent. the charges are distributed likewise and we speak of such a structure as being a distributed capacitance.Section V Electromagnetic and Other Applications of Aluminum Chapter 15 Capacitor Foil Capacitors both fixed and variable are used today in almost every electrical system. All of this is applicable to capacitor design. 15-1) where: w=2". g j(w'CL-I) Z~(r+---) wC (Eq. A common economic consideration in capacitor design is to obtain the largest amount of capacitance per unit vol ume of material used. This is. a required time constant of charge and discharge (with proper circuit re sistance) or a specified impulse release of stored energy. the general conditions gov erning the relation of potential and charge to capacitance were discussed as well as the influence of the dielectric medium. 15-1 (c) is: + . The foil electrodes appear as a uniformly distributed series resistance. Capacitor Design Considerations Under given conditions of electrical. high or low power. When the electrodes are deliberately concentrated in space. obtained by using the thinnest electrodes and the thinnest insulating material possessing the highest dielectric constant. the use of a capacitor almost always is a fundamental necessity. high voltage. The series impe dance (r jwL) is made up of the resistance and in ductance of the capacitor leads plus those inherent in the electrode material. From great power generating and distributing networks to electric organs. including telephone and radio systems. computers and motors. Fig. etc. 15-1 shows a simple. In Section Ill. the transmission loss is ideally zero over the pass-band and rises sharply be yond the edge or edges. if not adequately reduced or carried off by thermal conduction. 15-1. . .. This is because resistance may add appreciably to the desired low impedance at the resonance frequency or reduce the desired high impedance at the anti-resonant frequency.. as frequency increases. LEAD INDUCTANCE IL) LEAD INDUCTANCE III lEAD RESISTANCE PLUS EFFECTIVE FOIL RESISTANCE ld lEAD RESISTANCE IDEAL CAPACiTANCE 1<1 Fig. For low frequencies it will be equal to C. in radio trans mitting capacitors. 15-3) Where: E = volts w = 2". Above the resonant frequency. in carrier-telephone systems where the cumu lative loss of many filters in tandem may result in con siderable distortion which must be compensated for by means of attenuation-equalizing networks.. the capacitor engineer is usually primarily concerned with the effect of frequency on series and shunt resistance. EQUiVALENT PARALlel RESISTANCE CORRESPONDING TO CONDUCTANCE (g) OF DIELECTRIC Equivalent electrical circuit of a capaciror.C tan B (Eq. Fig. In his efforts to limit the losses in capacitors required to pass alternating current in telephone and electronic cir cuits. This sOurce of loss is generally objectionable.. At a frequency where resonance occurs (usually very high). 15-2 shows the reactance vs. frequency effect for a waxed paper insulated capacitor designed for audio frequency circuits.f (frequency in Hz) tan B = dissipation factor S = Joss angie 15-2 D. as the ohmic loss is almost always insignificant it is usually ignored in commerCial practice and power Joss is com puted with the following formula: W = E'". effective resistance becomes important in series coil and capacitor combinations required to.. In capacitors carrying heavy currents. the energy loss is a source of heating which. it is always possible to arrange the electrode and terminal wires to obtain the effect of a low impedance. long transmission line free of apparent resonance over a wide high-frequency band. can cause rapid deterioration and failure of the insulation. Parasitic loss in the reactive ele ments is unwanted loss which varies over the pass-!Jand and reaches a maximum . From the above it is obvious that the effective capacl C tance seen across the terminals of a capacitor is ( ) w'CL-l and that this will vary with frequency. the overall impedance is en tirely made up of the effective resistance of the leads and the foil electrodes at that frequency. the dissipated watt loss in a capacitor is oc casioned by both the ohmic loss in the foils and leads and the dielectric loss in the insulating materiaL However.. have low impedance at the resonance frequencies or parallel combinations required to have high impedance at the anti-resonance frequency. at high frequencies. the effect of the inductance increasingly reduces the capacitance and the capacitive reactance. In electric wave filters intended to pass a single band of frequencies and suppress others. In radio frequency circuits. ''''". Although theoretically every practical capacitor will exhibit resonance at some high frequency.at the edges resulting in distorted transmission.electromagnetic and other applications of aluminum FO'l elECTRODES lEADS "". Effective Resistance and Loss of a Capacitor: At fre quencies below which parasitiC inductance becomes sig nificant. the capacitor acts as an inductance coil with some series capacitance. for example. Control of heat loss enters into the design and use of capacitors for low frequency operation in connection with power factor correction and.elECTRIC Reduction of losses in a capacitor is quite important from the standpoints of both adequate performance and stable life. and the current flowing at points remote from the lead-in wires may be only a small fraction of the entering current.H 10 SERIES INDUCTIVE REACTA~C \1 EFFECT I IVE RESISjANi E . the terminals are laid-in at approximately the middle of the foil electrodes.000 Fig.p.~c. :1. RESONANCE "fREQUENCY . 15-2. the total effective resistance becomes R/12. In addition.' :x: o ~ ~\"'.6P <... ~'tV. Where. In general. With this arrangement. With reference to Fig. with each end terminal located L/2n from the end of the foil. it is seen that the heat loss in the foil and leads increases as the square of the frequency for constant applied voltage. 15-3 .\°V c.. it may be shown that the lowest resistance is obtained by spacing the terminals at intervals of L/n. 15-3 shows the effect of several laid-in terminals in reducing effective foil resistance especiaUy at the higher frequencies.capacitor foil This is because the effective resistance undergoes large changes with changing frequency and because of the wide frequency-range which circuits are often required to cover. impedance increases due to eddy-current and other losses including skin effect where only the outer portion of the metallic components carry the current.l =0.\. In other words.2)J. as is more usual in practice. narrow 100 electrodes of wound paper capacitors the effective foil resistance is approximately equal to 1/3 of the loop dc resistance obtained by adding the dc resistance values of the two foils. it is clear that alternating current entering the foil electrodes at the lead-in wires decreases as it spreads or distributes along the foil./ ~i-" ~ '7 ... EIJeClive Resistance of Foil Electrodes In the case of wound paper capacitors. by providing an efficient ~APACITANCE. Loss in Foil and Leads: At a first approximation. The effective resistance of the loop in each direction is then R/6 and. 1 C.~ .. In the limiting case.\. due to current attenuation along the foils only 33 percent of the total doc foil re sistance is effective with respect to alternating current.'p. gives the lowest attainable effective foil resistance for a foil of given ma terial and dimensions. Fig.~'" III w > ii S 100 t -~ /" ZIOOO 05 . since the two loops are in parallel. At higher frequencies. When "n" terminals are laid-in on a foil of length "L".\'n as "extended foil" or "overlapped foil" construction. there is a simple relationship between the effective resistance of the foil electrodes and their de resistance. 15-3) above. C =1MF ! INDUCTANCE.... this condition applies over the operating frequency-range of many capacitors. ..1 V) ~ o. It may be shown theoretically and demonstrated experimentally that for the long. From the watt loss (Eq.I I ~y. the current spreads in opposite directions along the foils.. This. the effective impedance of the foil and leads of a capacitor ap pears as a straight-line factor over a wide range of fre quency. Impedance versus frequency of paper capacitors at audio frequencies. o. I I .. the effec tive resistance is inversely proportional to the square of the number of terminals. I \Q<'. 15-1.'1-0 ". I I I 2 5 10 20 SO 100 200 fREQUENCY IN kHz SOO 1000 5000 10. the edge of the foil is connected to gether along its entire length. w U Z ~ u -< 10 c. kno. . Pri marilya filtering capacitor. \\ AT 1 kHz EFFECTIVE RESISTANCE \\ .':. '-'. The high capacitance per unit votume of electrolytic capacitors comes from the extreme thinness of the dielec tric which is an anodic oxide film previously built up by an electrolytic process on one of the foil electrodes. . 15-4. the film behaves like a relatively low resistance and. One capacitor absorbs the applied voltage on one half of the ac cycle and the other capacitor comes into ANODE C ATHODE ~ h . AT 3~ kHz de RESISTANCE OF FOIL ELECTRODES -----... 15-5 illustrates the relation between heat loss and fre quency in a waxed paper capacitor.. 15-3.. at low voltage.... ElectrOlytic capacitors are used extensively in low voltage ac applications. Etching the anode in creases the effective area so as to increase the capacitance as much as 7 to 30 times. . the film has a high resistance to the flow of current and behaves like a dielectric. . "f' . conduction path for heat from the inside to the outside of the unit.. if the voltage is high enough.. c FOIL PAPER Fig. Fig. Impedance at high frequency is reduced by adding terminals. The thick ness of this insulating film is but a few millionths of an inch and the working voltage gradient can be of the order of 10 million volts per inch.. \~ \\. 'i ~ .. Because of this unidirectional property.J.. .electromagnetic and other applications of aluminum 0 w 10 ~ U z ~ 20 '"u. Cross-sectional view oj a typical capacitor. J' ? •!. With the voltage reversed. Fig.1--.. the film is 15·4 suitable only for direct voltage in a single direction and the anode terminal is usually marked "positive" to indicate in which direction the voltage shall be applied.______ 2 3 4 5 NUMBER Of LAID. . k. With the voltage applied in one direction. One type consists virtually of two capacitors with their cathodes connected together so that the two capacitors operate in series but in opposite directions.'.w 30 Z 40 a: Z 0 50 i= u :::l 0 60 w a: 70 I Z w 80 U a: w " 90 \\ -. heats 1!tp and soon breaks down.. extended foil construction is advantageous in high-power capacitors having large heat dissipation.. this type is largely used in con nection with de circuits at working voltages less than 500 volts.IN TERMINALS PER FOIL ELECTRODE Fig. known as the anode (capacitance per cubic inch is inversely pro portional to the thickness of the dielectric). . Electrolytic Capacitors The electrolytic capacitor provides the most capacitance in a given space at the lowest cost per microfarad.. it passes large currents.. \ -- CAPACITANCE = lMf ----- . .'. . several thousand microfarads may be contained in a one cubic inch elec trolytic capacitor using etched aluminum foil electrodes. 15-4 shows a typical eleCtrolytic capacitor design... For example. I2r..35% to 99. Foil is produced either in the dry condition. I 0. Precision processing assures control of impurities....f) ... <..J2lTC) 2 .. 1. as motor-starting capaci tors when the fuil voltage is of short duration. allow for the manufacture of high reli ability capacitors with extended life and temperature characteristics and long.. A full range of purities are available-from 99..5. for example.... - .1 . J: ... Common usage today is in the telecom munications industries.02 1.. to filter audio frequencies in radio sets.. Capacitor Foil Availability Precise capacitor design begins with high-purity alumi num capacitor foil of precise thickness and desired sur- face and edge treatment... ..- .... .. ~ z <.... or with a so-called slick finish. Such capacitors are used extensively on low ac voltages.-.5-. . Where the voltage is very low...f) <..« w ..99% pure aluminum.. foil uni formity and continuity.1 0.. Improvements made in the design and manufacture of aluminum electrolytic capacitors allow for use in a wide variety of commercial and industrial precision circuit applications...... A thor oughly wet surface will show no droplet formations in dicative of oil residue. Heat loss versus frequency at constant current in paper capacitor play during the succeeding half-cycle when the voltage reverses.. The highest aluminum purities....'-..5 1 2 5 10 20 50 100 FREQUeNCY IN KILOCYCLES PER SECOND 200 500 1000 Fig.f) 0. for example 1199. and tightly wound compact coils.. High purity aluminum capacitor foil is produced by a number of manufacturers and is available in a wide range of thicknesses.. I" DIELECTRIC lOSS 12 90 fn-2 ~.. "" .........capacitor foil 10 I.2 -_.IAMP N =1. perfectly slit burr-free edges. excellent gauge control. or etched and anodized.... ~ 2 r.05 ...01 0.2 0. widths and alloys... The most common type is a capacitor wound as a non-polar capacitor utilizing two anodes instead of an anode and a cathode. Dry Foil: Specialized annealing technique provides a surface free from residual oil contamination. 0... they can be used continuously......5 0. but will not con taminate the dielectric. In general. - !'-.... they are limited on ac with respect to voltage because of the high power factor. 0.. stable storage life.. Slick Foil: A slightly lubricated surface developed in combination with annealing practices overcomes fric tion generated by winding equipment....... freedom of sticking during un winding. 0.-:s.... - - --. . for example..35 C= lMF 5 ! I . FOil lOSS. 01 99. A typical group of product data tables of one aluminum foil manufacturer is reproduced here. in this connection.006 .electromagnetic and other applications of aluminum TABLE 15-1 Chemical Composition-Maximum Allowable Impurities in Weight Percent Alloy ! Iron & I Iron Silicon Silicon Copper Manganese r Magnesium Titanium i Zinc Minimum Other Aluminum i 1235 I ! 1145 .88 .05 .06 .006 I 99.002 99. Table 15~3 gives thickness and width limitations. that the addition of other metals to aluminum usually lowers its electrical conductivity.05 1180 .65 .09 .35 .01 99. TabJe 15-4 gives welght-area conversion factors. Table 15~5 gives typical splice data. Also that heat treatment putting other metals in solid solution with the aluminum also lowers con~ ductivity.03 99.99 .01 . Table l5·6 gives foil toll sizes and weights.55 .45 . This film acts as a dielectric and results in high capaci tance as compared to paper capacitors.93 .02 .01 .02 99.05 .005 1193 . It is to be recalled. .006 1199 .05 .02 .006 .80 .006 . Table 15-2 gives typical properties.04 .01 i . thereby pro viding even greater capacitance in a given volume. 15-6 .04 .06 .01 i Anodized Foil: High purity aluminum foil is specially treated to provide a very thin oxide film on its surface.01 .09 1188 .006 Table 15~1 gives chemical composition of the aluminum alloys most used in condenser foil production. It can be etched to increase the surface area 1 to 30 times. 50 12.0015"·.15 .78 16.667 94.0 .61 .000 3.16 1193 .003" 8.00065 15.0045 2.500 142..0004" 23 Maximum Knurl .300 356.35 147.0015" All Widths Foil Tape .83 189.00035 29. 1145 . in.400 79. (Ultrasonic Splice) 15-7 .44 .001 .3 /g "~50u MIS 3Iau~64° 1235.003" 6.07 .100 6.25 . 0015.00017"-.058 83.2SB 1/4 N. 2SB 1/4 "·36" 1193.75 .32 .00060 17.73 TABLE 15-3 Thickness And Width Limitations Alloy Gauge Finish" Widths 1235.72 10.17 37.47 14.00045"·.250 71.0059" 2SB 1/4 u·36" 1235.789 74.74 .25 8..00090 11.00085 12..800 156.0025 4. lin.00017 60.00025 41.75 7. TABLE 15-5 Splices (Annealed Foil-Dry or Slick) GaB~ Width Splice u .000311 MIS .17 23.00025" MIS 3/.000 7.600 101.800 88.00017"-.600 309.95 .00040 25.78 168..43 63.00060 12.47 105.00045 22. 1145 . MIS 3/8 tI~26t1 1235.75 .0002 . 1145 .00023 44.001" MIS 3/8"~72" 1235.000 264.830 47...83 .050 14.39 29.00075 13. 1188 .000 Sq In.OO3 tt 6.0030 3.·.21_ .74 35.130 35..0020 5./lb I Sq Ftllb ! lb/432.34 .capacitor foil TABLE 15-2 Typical Physical Properties-O Temper TABLE 15-4 Weight·Area Conversion Factors I Sq In..0015" MIS 3/s ". 72" 1235.930 20.0004"-.69 1180 .04 .6 .00050 20.18 42.7 .26 ·432.280 15.91 31.OO5" All Widths (Electric Weld) t1 (Electrolytic Foil) .26 .0002 51.89 .300 418.tes Matte one side.003" 10.47 ..100 28.1145 .200 237.2 .75 126.000 sq.0055 1. 119~ .003" 10.003" 5.0059" MIS.0050 2.300 5. 1145 ..·.100 118.0010 10.0059 .0002"-.63 84..36" 1180.0035 2.88 . signifies one ream (500 sh••ts) of 24 in.420 23.23 . 1199 . 2SB designates Two sides bright.0059" 2SB I /4 "~52" 1180.92 40.) 1199 .002.00055 18.42 1188 .92 232.600 177.0 .36 21. MIS 3/8 "·36'* 1193.560 17.1 .00000f~_.00030 34. 1145 .002 .75 25.24 210.0015 6.37 .33 18.500 6.59 .860 12.63 1235 .0007 14..002 -. 1145 .89 33.1145 ..54 1145 .·43" 1235. x 36 in. sheets.002"·." Alloy Gauge Tensile-psi % Elongation Thickne.00095 10.500 8.600 129.72 27.00023" MIS 3/8u~31u 1235.72 9. 1188 !.OOO4·~ "MIS des.800 109.300 203.0040 2.00017 .gn. 5 6.9 7. For approximate net weight of Foil per roll.6 4.1 I 1.3 15.2 12.5 3.7 5.5 0.1 6.5 8..1 4.5 3.9 17.2 11.1 4.7 1..1 6.2 11.7 2.0 1.4 0.1 2.6 2. The above figures are approximate and do not include core weight. 15·8 .4 17.3 10.2 7.4 0.21b 0.5 17.2 I ! i i 0.0 10.4 10.4 6.3 10.3 13.0 2.8 13." 12" ~ 12%" 131"1 1314" 14n 14%U 15" 15%U NOTES: 10-1-5/16" 7" 10%U .3 0.5 9.0 7.5 4. of the metal COre.31b 0.4 16.5 4.electromagnetic and other applications of aluminum TABLE 15-6(a) Roll Size Maximum 00 6" 1 SII.2 14..31b 0.0 2.7 8.3 14.1 2.1 4.0 6.8 5.' Aluminum 5 12H 1 / 16 Aluminum Type of Core Width 114 11 _ 311 n 3 -311# 1/4 "_3 #1 81 3"_72## 171i_72u 3" Aluminum 8" 3"" Aluminum 13" 3 Iron 30" U TABLE 15·6(b) Roll Weight Data-Unmounted Foil SPOOLED ROLL Outside WEIGHT OF FOIL PER INCH OF WIOTH-(POUNOSI ~iameter ALUMINUM CORE (lnehes) 2" 2%'" 3" 3%" 4" 4%U 5" 5%" 6" 6%" ! 10-3" 10-2·1/2" 10-3" 00-1·1/2" 00-3-3116" 00-3" 00-3-1/4" - - 0.1 3.8 15.7 1.8 14.2 4.5 2.2 15.7 7.6 3.3 1.6 9. multiply the figure under the applicable roll 00 and type of core by the inches of roll width." 11 Y.7 8.2 12. respectively.6 3.7 5.7 1.1 1.4 11. exclusive of core weight.7 0.8 12.9 7.1 3.21b 0.2 15.2 14.3 6.3 16. IRON CORE .8 1.5 0.3 16.6 7%" 8" 8y"" 9" 9%" 4.6 10 and 00 dimensions represent the Inside and Outside Diameter.3 11.2 1.3 lOU 1. 10.5 9.2 13.7 5.3 12.4 6.0 3.2 13..6 - - - 0.8 8.0 3.5 2.9 11.0 18. the shaft. The laminations may have either open or closed slots (See Fig. Casting rotors in aluminum makes it possible to fill all the conductor bar slots. aluminum has lower conductivity than cop per. 16-3 shows a typical cast rotorfrom which all of the iron laminations have been eaten away by acid in order Electrical Conductivity: In an induction motor. the elosed-slot design is much more commonly used. Weight: Because of the relative densities of the two metals the weight of an aluminum conductor is half that of an equivalent copper conductor. Because of this. a cast rotor should maintain its balance indefinitely whereas a welded. on a volume basis. These are the punched iron disks or laminations containing the holes for the conducting bars. however in recent years. Thermal Conductivity: The higher the thermal conduc . the greater the effiCiency of the motor under normal load. A and B). in which the conductors do not fill the slots completely. On the other hand. Squirrel cage induction motors are the most popular form of motor design for both household appliances and heavy industrial equipment. 16-2. the diameter and height of which are determined by the motor design. The overall dimensions remain approximately the same. It gives motor designers greater latitude and makes better use of the slots by filling them completely.Section V Electromagnetic and Other Electrical Applications of Aluminum Chapter 16 Cast Aluminum Rotors and Switchgear to reveal the interior construction. the higher the electrical conductivity of the rotor. Since. and the aluminum which is used in integrally cast ing the conductor bars and collcctor rings. The resultant cast rotor is shown in Fig. less starting inertia. bind the entire assembly together. The stack of laminations is placed in a permanent mold or die-casting die containing a space at the top and bottom for the simultaneous casting of end-rings. Experimental work with aluminum castings conducted in the 1930's focused serious attention on the lower cost and engineering advantages of making an integrally cast aluminum/iron lamination squirrel cage rotor. may lose its balance in time. Pound for pound aluminum has more than twice the heat capacity of copper but. This means that an aluminum rotor is subject to less stress from centrifugal forces. 16-1. The use to which the motor will be subjected determines motor design and selection of alloy for a desired conductivity. The resultant assembly is sturdier and less noisy than a copper-cage rotor. depending on the succeeding finishing steps required and the particular manufacturing process being used. brazed or wound cage. since its weight in a rotor is about half that of an equivalent copper-cage. the required conductivity in a cast aluminum rotor is achieved simply by increasing the size of the slots and of the . If this particular rotor were of the closed-slot type. heat capacity remains on an equivalent basis. The Cast Rotor The cast rotor has two essential components. and produce the end-rings and cooling fan vanes in a single economical operation. the lower the conductivity the higher the starting torque and the lower the starting current. The mold is clamped together and the selected molten aluminum alloy is poured or forced into the mold.end rings over that required by an equivalent copper cage. The greater the heat capacity of the rotor the cooler it remains during temporary overloads. Comparative Performance of Cast Aluminum Rotors Before the advent of present aluminum die casting tech niques. Fig. The rotor shaft mayor may not be inserted in the rotor bore at this point. the flash would not be in evidence. The particular rotor shown is of the open-slot type. These end-rings serve to connect electrically all of the rotor bars. and any cooling holes or vents. Heat Capacity: Temperature rise is one of the limiting factors in motor design. rotors for squirrel cage motors were built up in a step by step fashion using iron laminations and wound copper wire conductors or conducting rods of copper or bronze alloys welded to end-rings of copper or bronze. A stack of lami nations is assembled for a particular rotor. less vibration while running and is more portable than an equivalent copper rotor. electromagnetic and other electrical applications of aluminum Fig. The higher alloy content is controlled carefully and pro. 16-1(a). Alloy Selection Rotor casting demands relatively high conductivity for most applications. therefore. For most applica tions rotor manufacturers strive for maximum conductivity but as the size and complexity of the rotor increases some sacrifice is unavoidable if the needed castability and strength are to be secured. On the other hand an equivalent aluminum cage has a relatively larger volume and better heat transmission conditions between conductor and core. it is preferable to melt and flux in one unit and transfer the molten metal to a second furnace for casting. The use of a single furnace for melting and casting does not provide good temperature control since ingot and gates charged into the melt drop the temperature of the metal making it impossible to maintain a uniform . therefore. Although it is possible to use the same crucible furnace for both the melting and casting processes. For a listing of rotor alloys and their chemical compo 16·2 Fig. For larger rotors a greater amount of alloyed silicon and iron is provided so that the conductivity may be from 54 to 57% lACS. Manufac turers recommend the use of the higher iron/silicon alloy when one or more dimensions of the rotor is greater than five inches. Unfortunately not all of these factors are opti mized by the same alloy composition. Manufacture of Cast Aluminum Rotors Melling and Melal Preparation Equipment Fuel fired. castability. in cast rotor alloy se lection are: conductivity. A typical closed-slot rotor punching. induction and electric resistance furnaces are used to melt and hold aluminum for the casting of motor rotors. greater freedom from hot cracking and shrinkage during casting. Rotor Ingot: Manufacturers of aluminum rotor alloys supply such metal in ingot form to specifications for composition and conductivity. Yet rotor manufacturers need a means for identifying consistent electrical characteristics in the rotor metal they purchase.slot rotor punching. In this respect. Aluminum has half the thermal conductivity of copper. Manufacturers generally provide several recommended aluminum rotor alloys wbose USe depends upon 'the size of the rotor. The aluminum must solidify without cracks or excessive porosity to provide the necessary elec trical circuits. 16-1(b). equivalent performance is attained. The important factors. and develop adequate strength to bind tbe entire unit together. This is accomplished by specifying the chemical composition limits and a range or the mini mum electrical conductivity of the ingot. The rotor alloys are particularly free from non-metallic and barmful oxide inclusions resulting in better fluidity and improved casta bility than commercial grades of unalloyed aluminum. Conductivity from Composition: Conductivity meas urements on the ingot itself are not a reliable measure of the conductivity of connector bars arid collector rin!\S be cause rotor casting processes affect such conductivity measurements. A typical open. The follOwing types of furnace equipment ClIn be used to melt and hold aluminum for motor rotors: Crucible Furnaces: Underfired crucible furnaces are available witb capacities that range from just a few pounds to 1500 pounds. cleanliness and strength. The choice of melting equipment will depend on the type and volume of rotors to he cast and on the cost of fuel for any given locality. For smaller rotor sizes the aluminum content is higher and the conductivity approaches 59 to 60% lACS. see Table 16-1 on page 16-5.ides greater castability. exceptionally dean metal that will completely fill the conductor-bar slots and form sound end-rings and fan vanes around the assembled core of steel laminations. ttvlty the greater the ability of the rotor to dissipate heat. sitions. The die casting process provides a good quality rotor casting at a low unit cost. "INhere fluxing is deemed necessary. The reverberatory furnace is usually employed as a "breakdown" furnace with the molten metal transferred to crucible type or induction holding furnaces at the casting machine. The non-metallic deposit in the channels of an induction fur nace consists of the oxides and nitrides of aluminum and other elements which are formed during continuous melt ing and holding. With rotor grade ingots. Proprietary salt fluxes are used to dry the surface skim on the melt and remove build up from crucibles. Fig. 16-3 . Successful operation of core-type induction furnaces requires regular maintenance of the inductor channels. The charging of gates and the biseuits from the shot chamber may necessitate fluxing of the melt at times to cleanse the metal and the channels. at one time. Conventional die casting practices are used to produce rotors. Iron surrounding the cast-aluminum squirrel cage has been removed to reveal construction. Induction furnaces provide a high quality melt with uniform composition and excellent temperature control. Casting Methods Employed for Aluminum Rotors The horizontal cold chamber die-casting method is reC ommended for high volume production of fractional horse power motor rotors. The proprietary fluxing compounds required to clean crucible and reverberatory furnaces in induction fumaces have been shown to promote channel plugging. Multiple cavity dies are usually employed to cast several rotors of the same or different design. The non-metallics are concentrated in the channels by the electromagnetic field and form a hard deposit.000 pounds. In volume production the high original investment cost of the die casting machine. Reverberatory furnaces with a dipping well or wells are also employed as combination melt and hold furnaces. The combination of rotor grades of ingot and clean furnaces provides optimum metal quality. The advantage of the dip well type of furnace is in the elimination of molten metal transfer and a low cost for melting and holding. A single furnace for melting and holding also complicates the fluxing of the melt for cleaning the metal. These channels usually require "rodding out" at regular intervals to prevent the channel from plugging up. dies and suitable metal melting and holding equipment is justified. aside from its higher original cost. the steel lamination stack is usually loaded into the die without preheating. Complex intermetallie compounds of iron and impurities may also settle in the furnace channels if the 0 riginal rotor alloy is contaminated with impurity elements. SOme variation in metal temperature and oxide content can be expected. A typical die-cast rolor of the open-slot type. they must be kept coated with a re fractory pot wash to minimize iron pickup since iron is readily soluble in molten aluminum and reduces the elec trical conductivity of aluminum. the degree of cleanliness of the melting and holding furnaces is an important factor in preventing low or variable conductivity and casting prob lems due to the occurrence of oxide inclusions in the rotor castings. Where cast iron cruci bles are employed. 16-2. In the die-east ing process. Fig. The principal disadvantage of this type of furnace. The metal salts in fluxing compounds form oxides which are de posited On the walls of the inductor channels. however. The process lends itself to automation providing further production economics.cast aluminum rotors and switchgear pouring or casting temperature. it is not neces sary to flux the melt when 100% ingot is charged. Reverberatory Furnaces: Reverberatory furnaces may be built in sizes varying from about 1000 pounds capacity to as high as 100. In all rotor casting work. is that salt fluxing and cleaning of the furnace is more difficult than with the crucible type. 16-3. where ingot and scrap are charged into a single chamber induction furnace. The use of a refractory crucible such as silicon carbide or clay graphite is recommended as iron pickup can result from the use of cast iron crucibles. a degassing flux of the hexa chloroethane type or chlorine-nitrogen gas mixture is recommended. Induction Furnaces: Electric induction furnaces are employed by a number of motor rotor manufacturers for the melting and holding of aluminum. it is desirable to preheat the lamination stack to a temperature of from 400 0 -1000° F. This type of defect reduces the conduc tance of the rotor and the electrical efficiency of the motor. Since it is impractical to supply molten metal to feed or make up for this volume change in most designs of cast rotors. The optimum metal injection rate must be determined by the producer as it will vary depending on the type of casting equipment. In large rotors.80 or 99. Dies should be preheated to 250-300°C (48()"570°F). Some porosity of this type is experienced in varying degrees in all of the casting methods employed for rotors. If asbestos paper is used to line the mold (vertical pressure die casting of larger rotors) it should be thor oughly furnace dried just before use to eliminate this source of gas pick-up. The original investment is lower than die casting equipment. Steel Laminations: In the stamping of laminations the formation of burrs at the slot edges should be kept to a minimum by proper maintenance of punches and dies. is mOre prone to cracks and shrinks than the rotor alloys. Once casting tempera ture is established it should be held within ± lOoC. To assist in the casting of sound conductor bars and end rings (whether by gravity. The rotor mold and the lamination stack are mounted on the upper platen. For pressure die cast rotors.0 alloy rotors. The sump may be lined with mica and/or asbestos paper to prevent excessive metal temperature loss or is sometimes sprayed with an aqueous graphite or similar type coating to prevent the metal from sticking. The rate of metal injection into the die can also influence the occurrence of this type of defect. Casting Problems Problems usually show up as low conductance or high starting torque of the rotors. Cracks in the end rings or in the conductor bars are extremely detrimental to the service of the rotor. uniform casting cycles should be maintained so as to properly control die and mold temperatures. Preheating the laminations also oxidizes freshly sheared edges of the slots thereby re ducing the tendency for metallurgical bonding to occur between the steel and aluminum. Thermal Treatment: Two considerations are impor tant for the efficient electrical operation of a squirrel cage motor. some internal shrinkage porosity may occur. This is due to a large differential in thermal expansion of the two metals. The second item is particularly important and even a partial separation of aluminum from iron immediately results in noticeably bet ter performance. it may be possible to provide excess metal in the form of risers to aid in overcoming 16-4 the shrinkage tendency in the top ring. Excessive burring can contribute to metallurgical bond ing with the aluminum during casting. This type of defect may be reduced by providing adequate venting of the die or mold during the casting cycle and by avoiding excessive use of die or mold lubricants. centrifugal or pressure die casting) it is recommended that the steel lamination stacks be preheated. Unalloyed aluminum. In this process the lower platen of the press usually contains a round well Or sump into which the molten metal is poured. 99. Careful control of the metal temperature and mold temperature is neces sary in minimizing cracks and poor fill in 380. mold design and design of rotor being cast. particularly in large integral rotors with heavy end rings. The molten metal is forced by the stroke of the press through a series of small gates into the rotor die. Casting: Casting temperatures for rotor metal may lie anywhere in the range 700-800°C (129()"1470°F) depending upon individual foundry practices.85. The dross defect can be the result of poor metal melting and handling practice and is discussed un der the previous section on melting.0 are prone to cracking in rotor casting because of their relatively long solidifica tion range. Other casting alloys such as 380.electromagnetic and other electrical applicatians of aluminum The vertical press method of pressure casting aluminum rotors has been used for many years to cast both fractional and large integral horsepower motor rotors. In this casting method. The major casting problem in the production of aluminum rotors is the presence of entrapped air and/or gas from the die lubricant. In pressure die-casting an important factor in the pro duction of sound rotors is adequate venting of the cavity. This type of defect manifests itself as a number of smooth rounded (or slightly elongated) gas holes within the end rings and conductor bars. Aluminum alloys undergo a 5 to 6 percent volume decrease in solidifying from the liquid state. This greatly facilitates metal flow and the filling of intricate passages. The gates into the rotor usually consist of a number of tapered holes through the base plate of the mold into the collector ring part of the cavity. Thermal treatment of rotor castings. and lead to loss of motor efficiency. cracks and poor fill (usually in con ductor bars). 1-2 hours at 300 450°C (57()"840°F). Excessive use of die lubricants can lead to venting prob lems. In production. prior to loading the stack into the casting die. is helpful in breaking metallurgical bonds between steel laminations and the aluminum con ductor bars. Other casting defects encountered in rotors are dross or oxide films. shrinkage. The required preheat temperature of the laminations will vary depending on the size of the rotor to be cast and the size of the slots in the laminations. Iron is readilv soluble in molten aluminum and iron contamination in the melt is quite often the cause of low conductivity and poor fill or cold shuts. . Preheating at 250-350°C for 1-2 hours is usually adequate though bulky lamination stacks may require higher temperatures for a somewhat longer period. These are (I) there should be a reasonably high inter-laminar resistance and (2) there should be a high resistance between the iron laminations and the die-cast aluminum conductors and end rings. Cold dies are the cause of scrap which can be reduced by maintaining uniform and continuous production cycling. Loss of conductivity and poor casting characteristics may occur if the rotor alloy becomes contaminated with other metals. 0 (Nominal 5. 16·5 .1 130. ratio is 2. The heating also tends to introduce some further oxide film between the aluminum and iron thus assisting electrical isolation further.05 0. 100. non magnetic properties and superb fabrication capability are some of the most important characteristics favoring the use of aluminum.15 (bl (el (d) 0. the standard foundry alloy 380.1 99. "In judging the rotor alloy to be used.03 0.5 minimum.1 170. Fig. 16-4 shows an example of modern switchgear using aluminum in various forms.00% 99. the lessor purity 100..10 0.50% 54 55 57 99. 8.6-0.05 0.10 0.1) is the most difficult to cast and is subject to a greater degree of shrink cracking. excellent corrosion resistance.30% 150.1 130. High electrical and thermal conductivity.1 170.0 minimum. Aluminum in Power Switchgear Aluminum and its alloys have become increasingly important in the manufacture of all types of electrical switchgear. it should be noted that the highest purity alloy (170.03 0.1 99.cast aluminum rotors and swilchgear TABLE 16-1 Rotor Metal Alloys Alloy" Aluminum Grade Min.10 0.1 alloy is easier to cast with a minimum of cracks.05 (al (al tal lal (al (al (a) (al 0. sheet metal enclosures and hardware to important current-carrying and structural parts.03 (al (al lal la) Total 0.8 (bl (el Id) (al (b) Ie) Id) Manga· nta- Copper nese Chro· mium Zinc nium 0.0 (Nominal 3. For high torque rotors 137% lACS typical) the standard foundry alloy 443.2% Sil is applicable. Also for high torque 30% lACS conductivity.Min. ratio is 2.5 minimum.025% max. Its applications in switchgear vary from small rivets. Purity" Rated Conductivity % lACS .03 0. high strength to-weight ratio.1 150.70% 59 Chemical Composition of Rotor Alloys 1 AHoy Silicon Iron 100.10 0.5% Sil is applicable. By contrast.10 chromium plus titanium plus vanadium is 0.10 0.5% cu.1 0. ratio is 1.05 (al (al (a) -- Manganese plus Iron to silicon Iron to silicon Iron to silicon (0) Othe. Each 0. treatment temperatures at the lower end of the indicated range are less likely to cause blistering.05 0. Modern aluminum switch gear capable of handling 5 0.electromagnetic and other electrical applications of aluminum • i Figure 16-4. 16-6 .000 ampere short circUit current. the allowable currents are to be reduced to 70% of the tabulated value. burr-free interior. unions. in order to qualify for UL Labels. A very high order of mechanical and flame protection for the enclosed cables. since they only carry the unbalanced currents in normally balanced circuits. the Code specifies maximum allowable fill areas for given conduit sizes. For example. round. Table 17-6 gives comparative weights for the three types of metallic conduit. is the number of loaded conductors in a given conduit. Development of a compatible line of accessories. Table 17-4 converts these area limitations to the number of typical conductor sizes permitted in one conduit based on both thermosetting and thermoplastic insulations. andIMC. If there are 7 to 24 conductors in the conduit. in the building foundations or the sub grade is the use of rigid conduit. Tables 9-3. many-turned run. built-in cable runways in cast concrete structures. smooth.Section VI Related Structural Applications of Aluminum Chapter 17 Rigid Aluminum Conduct One of the earliest. Adequate strength in relation to size for self-support over reasonable lengths. Freedom from destructive corrosion in the working environment. methods of installing concealed electrical cable within the structure of a building. are not to be considered in determining '" Table 17~2 shows the maximum number of compact conductors allowable in conduit or tubing:. (The neutral conductors. Tables 17 Sa and 17-5b give dimensions of rigid aluminum. Permanent. The factors involved in NEC rigid conduit specifications relate to installation and operating requirements. galvan ized steel. Metallic conduits can contribute a small amount of heating due to hysteresis (if the conduit is magnetic) and eddy current losses. An easy means for replacing conductors or pulling in additional ones. An easy pulling. These include rigid aluminum. tees. Provision and maintenance of good electrical conduc tivity through the conduit proper and across all threaded joints. In Chapter 9 of this book. Provision for expansion fittings for long lengths oper ating under widely varying temperature conditions. conduit bodies and boxes in aluminum. galvanized steel. The tables referenced above give ampacity data for the case of not more than three loaded conductors per conduit. Pull-boxes to enable straight pulls as required. Elements of Conduit Design Important elements in the design of electrical conduit He related to. snag-free pathway for the cables through an otherwise intricate. The NEC also recognizes the effect of the conduit or raceway on temperature rise of the encased conductor. however. shows the allowable fill area for each conduit trade size. Capability of being cut and threaded readily and bent smoothly (no flattening) with normal field methods and tools. Table 17-1. 17-1 . galvanized steel and PVC. 9-5. IMC (intermediate metal conduit) and nonmetallic conduit. as well as conduit fittings. abstracted from the 1987 NEC. such as elbows. * Table 17-3 gives cross-sectional areas for typical conductor sizes insulated with both thermosetting and thermoplastic materials. When the number of conductors increases to from 4 to 6 the ampacity values are reduced to 80% of the tabulated value. Smooth. Of greatest importance in its effect on ampacity. couplings. The many advantages rigid conduit provides include. installation and construction requirements for electrical conduit are set by the National Electrical Code (NEC). pull and junction boxes. and still most effective. 9-6 and 9-7 show characteristics of wires and feeders in magnetic and non-magnetic conduit or raceways. 9-4. A high order of safety to personnel who might otherwise accidentally come in contact with the ungrounded portion of the electrical system. Individual product lines must be manufactured to conform to the standards set forth by Underwriters Laboratories. 04 1.31 09 . 2-Cond.92 2.95 3.T T X 'T HIH H H H H H H W H H W N W ~IW N T i 3 in.46 2.91 5.29 3.86 1.72 20.54 3. ! 15 15 11 11 15 18 18 8 8 11 13 13 6 8 10 10 11 14 14 6 5 5 7 8 8 9 12 12 7 8 10 10 4 4 5 7 5 6 6 7 8 8 3 3 7 6 7 3 3 4 5 5 3 4 4 4 5 5 3 3 3 3 4 4 3 3 3 3 4 3 3 ~I X..20 8.12 14 14 7 8 B 9 11 11 6 7 7 8 9 10 10 12 12 5 6 6 7 8 8 9 11 11 5 5 6 6 7 8 8 9 10 4 4 5 5 6 6 7 8 8 4 4 5 5 5 6 7 3 4 4 6 6 6 3 3 3 4 4 3 3 3 4 4 4 5 5 5 3 3 3 4 4 4 . I TABLE 17·2 Maximum Number of Compact Conductors in Trade Sizes of Conduit or Tubing l:.09 8. 53% 31% 40% 16 .74 10.78 2.07 3.60 15. W H Wi N W N W N Conduit Trade Size 2 in.28 .38 9.96 5.50 2.79 7. 12 .00 28.W N eml i 1 In. i .46 .80 1.34 .90 12. 3112 in.53 . 4 in. 6 4 2 1 110 210 3/0 I I 410 250 300 350 400 500 600 700 750 1000 17·2 5 4 3 7 11/4 4 6 4 3 3 9 7 5 3 3 XIT T HIH H W W' H H in~ 13 11 12 9 8 8 7 6 6 4 4 5 4 3 3 3 3 3 3 N 1112 In. 3 or more Inches Area Sq.94 6. 2112 In.60 .T T X I I T T Hi H H H'H H H I H H H! W H H W H H .63 1.82 1..96 % 1 1% 1% 2 2% 3 3% 4 5 6 I I I I i 30 .!TTX!TT Conductor H 'H H Size ~ AWGor W H H W H I k 'l N .16 .25 6.27 .56 i .47 ... 12 15 15 10 13 13 9 10 10.89.l Insulation Type ! . X'T T X.08 1.related strudural applications of aluminum TABLE 17-1 Conduit-Allowable Fill Area Square Inches Conduit Trade Size Internal Total 1·Cond.21 . i I i ! i . In.34 1.00 11.04 3. ---~~ .36 4. 364 593 . relatively high electrical and thermal conductivity.026 1. "'RHH and RHW without outer covering are the same as THW.053 .031 .126 .017 062 027 .983 1.245 1.659 2.592 . with couplings.275 2.109 . Protective Capability: In a conduit/cable system when a phase-to-ground fault occurs.767 1. The larger the conduit size.173 . 124 . uniform interior surface.062 1.291 1. This dif ference in weight is reflected in substantially greater ease and cost savings in installation.099 . the wiring system neutral is grounded at one point.478 1.548 1.182 .272 . it is to act as a mechanical protection and carry current only in the case of a fault.421 1. and one-half that of steellMC. Chapter 9.904 .593 2. the greater the savings in labor.018 .118 . if accidental continuities are found to exist between the neutral and the conduit.084 .046 .203 .953 2. 6063-Tl alloy.rigid aluminum conduit TABLE 17-3 Conductor Cross-Sectional Areas (Based on Table 5. This separation of neutral ground current *1987 National Electrical Code. and if the installation is properly made will maintain its high value. Rigid Aluminum Conduit Aluminum rigid conduit has been widely used during the past five decades due to recognition that lightweight aluminum conduit offers several advantages over steel" including reduced costs of installation.118 . protective oxide Electrical Characteristics Aluminum conduit alloy 6063 has about 1I4 the elec trical resistance of the usual galvanized mild steel conduit.012 .226 .730 1.890 3.208 .150 .305 2.084 .933 1. For example.520 . I/O 2/0 310 4/0 250 300 350 400 836 50O 600 700 750 900 900 1000 1250 1500 1750 2000 .408 1. the conduit will normally carry most of the fault current-which can be quite high in value.237 .716 .362 Type XHHW' BARE .226 .I Types Type AWG. SQUARE INCHES INSULATED CONDUCTOR ' WIRE ~-----------------1 SIZE.: kemil RHH & RHW' Type THW THHN THWN 12 10 8 6 4 3 2 1 .467 .271 .158 1.328 A03 .267 . Section 250-21 17·3 .161 . It must be understood that rigid electrical conduit as installed per NEC requirements is normally not supposed to carry any ground currents.. .568 .025 .260 .189 .194 1.484 .901 -=~~~--~~~~ .467 . The same size aluminum conduit weighs only 34 pounds and is handled easily by one man. The conduit may be grounded at many points.561 2. though other alloys can be used which meet UL requirements. the der'dting amounts given above.147 .531 593 .206 2.219 . 1987 NEC) film. extruded pipe provides a smooth. aluminum conduit is completely moisture-and vapor-tight.531 . increased cor rosion resistance and improved ground path.833 1.061 1.008 .488 .022 .829 2.159 .312 .046 .094 . elbows and boxes. . The following material examines in some detail how these plus factors compare with steel.629 697 .039 1.087 .137 .099 . Usually. In any event.271 .042 .030 . and excellent ductility and machinability are basic factors in its present wide acceptance. Advantages of Aluminum Conduit Aluminum's combination of light weight. .378 1.225 1.189 .782 1. The Code specifically· indicates that any neutral wires shall not be instailed in electrical continuity wi th the conduit and.159 . the fault current flowing in the conduit raises its potential above ground by an amount equal to the impedance drop to ground. and in this respect the advantage of aluminum conduit is obvious. Weight Comparison: Aluminum conduit with aluminum couplings weighs approximately one-third of its galvanized steel counterpart.005 . .753 2.207 . a IO-foot standard length of 4-inch steel conduit weighs over 98 pounds and requires two men or a hoist to place it.087 i Composition and Manufacture: Rigid aluminum con duit is usually extruded from the magnesium-silicide. APPROXIMATE AREA.415 .336 1.123 1. Also.329 .762 .038 . such neutral faults shall be cleared.416 _ .390 .626 1.017 .358 .311 . a run of aluminum conduit will show about 4-112 times greater electrical conductivity. Note 10 to NEC Tables 310-16 to 310-31 specifies when the neutral must be counted as a current-carrying conductor).548 2.617 1..276 .832 1.879 1.085 . In the installed condition.060 082 .716 . The lower the installed conduit impedance to ground the less danger there is from fault! ground shocks.067 . The lower resistance of aluminum conduit also means that ground current fault relaying is more reliable.684 .328 .403 . Being an extrusion.001 1.037 052 .389 1.109 . 1 1 1' 2 6: 13 ! 4: 10 I i ! 4/0 250 300 350 400 500 600 700 750 800 900 1000 ..related structural applications of aluminum TABLE 17-4 Typical Number of Conductors Allowable in Trade Sizes of Conduit or Tubing ----------~---- Maximum Number of Conductors in Conduit" Wire Size AWG or kernil 14 12 10 8 6 4 3 2 1 1/0 2/0 3/0 ! I '!f. being non magnetic. 1960. 8 10 12 15 16.)Tl~ and interference with communi cation circuits. 21 21 7 8 10 13 14:I 17 18: 6 9 11 l2! 14 15 5 7 9.1 4 4 4 72 61 51 42 35 28 24 21 19 16 13 11 11 10 9 8 A . The net effect is that voltage drop in a typical three-phase feeder or branch circuit in aluminum conduit may be from 10 percent to as much as 20 percent lower than with a corresponding steel conduit.THWN and THHN. 2 3 3 4 1 1 1: 2 3 3 4 1 1 3 1 1 3 3 1 1 2 1 1 2 3 1: 1 1 2 1 1 1 1 1 1 1 1 . Fig. 1 1 3 3 1 . 10 12 13 7 8 10 10 6 4' 3 4' 5 61 7 8 9. 1 1 1 1 1 7i ~I 32 27: 22 16 15 12 11 9 8 7 5 5 4 4 39 33 29 24 4! 5 3.164117 : 43 73 61 104: 95 160127 1631 i 22 36 32 51! 49 79. 5 5 1 9 3: 3 4. The steel couplings all smoked profusely and showed thread damage. this overall reduced voltage drop may permit the use of conductors one size . F. time of 2-inch aluminum and steel conduits joined in series and subjected to a short circuit current flow of 22. The steel conduit at the end of 10 seconds was buckling and dully glowing and its temperature rise was about 4-112 times as great as that of the aluminum -AlEE Paper DP 60-652. I A B 3%:11 BA : 4" B: A B A 5" B 6" B A I 1 6' 5i 1 1 A : I 2 1 1 1 1 1 1 1 3" 2%/' 65 154 9~ 192 143 ! 157 53 114 76.66 106 85' 136:133 16 26 23 37 36 5~148 76 62 98 97 154 141 12 16 17 22 27! 35 36 47 47 60 73 94 106 137 10 13 15 19 23 29 31 39 40 51 63 80 91 116 9 11 13 16 20 25' 27 33 34 43 54 67 78: 97 94 70 44 22 15 9 8 7 5 4 3 3 1! ! 2" A B l"ht A B I i 5 4 3 2 2 1 1 1 1 1 1 1 4 3 3 2! 1! 1' ! I I 8.THW. L. the aluminum con duits still retained their gummed labels and showed no signs of the heavy current passage after the test. 6 5 I . ~.r A B 1250 1500 1750 2000 B A 1" A B 10: 24 16 39 8' 18' 13 29 4 6 6: 11 11 18 . 3! 4 3 7 8: 5 6 2 4 3 5 5'I 6 7: 4 41 5 6 1 2i 3 1 1 3 4 5 3 4 1 1 2 4 4 3 3 1 1 2.. flow from the conduit is very helpful in minimizing ac electrolytic corro:. its ability to carry short circuit currents is greatly superior to galvanized steeL Circuit Voltage Drop: Aluminum conduit. 1%10 A B 69 40: 51 : 32 32 26 16 13 11 10 7 7 6 6 5 5 29 24 19 10 7 5 4 4 1! 3 1 2 1: 1 1 1 3 3 2 1 4 3 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 ! I i . Roehman. despite the considerably lower melt-point of aluminum conduit. B .. 2 1 4i 6' 1 ! 1 1 2! 3. Short Circuit Capability: Comparative short circuit tests' on aluminum and galvanized steel conduits have been made to determine their relative behavior under heavy fault conditions. 4 1 1. 7. RHW (Without outer covering). Chapter 9. For con ductor sizes 250 kcmil and higher.."" I . 6 5' 1 1 1 1 1 1 1 1 9 12' 14 18 19! 25. Thus. 5 20 16 14 12 11 9 7 7 6 6 50' 42 35 29 24 20' 17 15 13 11 9 8 7 57 49 41 35 29 23 20' lSi 16 14 11 7i 10 9 9 6 7 6! 8 3. Table 3 lor other sizes and types.. 17-4 conduit. 2 1 . exhibits no hysteresis losses from alternating current fields. (XHHW in sizes #4 AWG through 500 kemil) see NEC. ~I 1 1 1• 1 1' 1 ! 1: I 1 1 1' 1i 1 1 1 . 25. RHH.. In contrast. 17-1 shows the temperature rise vs.200 amperes RMS. '" 31.130 .029 1.5 . Broad Industrial Application: Installations of rigid alu minum conduit usually require no maintenance painting 17-5 ." I 9#-11 %" 9'-11" 9'-11" 9'-11" Threads Per Inch 14 14 11% 11 YzI 11% 9'-11%" 11 Y.6 4.080 .203 .875 3.900 2. has an industry maximum limit of 0. inches II Wall Thickn." been demonstrated repeatedly by tests and research stud ies.988 4. This tough.597 3. according to Paper CP 58-1072 of the American Institute of Electrical Engineers..095 .130 .548 4.168 ...06'::5~.. there appeared no significant effects on yield and tensile strengths.677 2...085 .653 1. 1..10S . which is commonly used for rigid aluminum conduit.226 .660 1." On the other hand. protective skin automatically renews itself whenever the bare metal becomes exposed. Some of the results: No signs of corrosion were evident on rigid aluminum conduit when inspected 5 years after it was installed on cooling towers.050 1.120 1. I Inches II 1.S57 3. 3.145 ..rigid olum.879 1.130 .35 percent for iron (Table 17-7).160 .553 3.090 .315 1.105 .0. Atmospheric corrosion rates of four solid metals.178 3. aluminum quickly builds up its refractory oxide layer which is relatively inert to most chemicals except strong alkalies and acids.160 or in some cases two sizes smaller is the governing concern.622 . are shown in Table 17-8. Inches .6~2.0.140 .466 .258 : Length WID Coupling 9'_11%" 9'-11%.L_--'S"--_ _ TABLE 17-5b Dimensions-!MC Conduit Types I & II Trade Size y.043 1.133 .4 and 5 years.2:. 2.308 1. Inches Thickness .026 5.108 . After exposures of I. as deter mined by a IO-year study project of an ASTM committee.070 .155 .833 1..380 1.375 2.ze ." 9'-11" 9'-11" Threads Per Inch . The galvanizing on a steel conduit acts as an anodic sacrificial metal coating and is continuously uwearing out.216 .0. 0.673 .638 1.154 .4S8 .155 . Aluminum alloy 6063 was exposed to marine.075 .468 1.047 .476 3.152 2.971 4.815 1.824 1.::8~0_ _. I I II ..109 .000~' 9 -IOV.130 . Aluminum conduit has been used successfully for more than 50 years in many marine and corrosive industrial installations under conditions where galvanized steel coo duit should not be used. Severe combinations of moisture and chemical-laden atmospheres at the installation had reo quired frequent replacement of rigid galvanized conduit.~6.703 2.206 .0. % 1 1% 1% 2 2% 3 3% 4 0.068 3.:!.067 2. industrial and rural atmospheres. Aluminum's resistance to atmospheric corrosion has ! Length WID Coupling 9'-11%.873 1098 1.1 percent copper coment and 0.S63 3.469 3.108 .085 .840 'h -Y.668 4.igid Aluminum and Galvanized Steel Conduit Trade S.216 3.113 . 14 14 11 'h 11% 11'V2 1% 9'_11># 1'12 9'-11" 111.num conduit TABLE 17-5a Dimensions-ll.237 .500 9'-10%" 8 4 5 5.085 .468 3. 8 8 8 9'-11%" 8 9'-11'~ 9'-10Y2" 9'-1OY.L_-.290 1.500 I Wan 1. where voltage drop Corrosion Charaderislits 01 Rigid Aluminum Conduil Alloy 6063.711 4.893 2.049 1.563 ~10" 8 6 _ _-'--_-'6~.6 2 9'-10'hu 2'12 8 ! 9'-10%" 8 3 .360 2.170 2. 8 4.437 1.368 2. 9'-1()':_..610 2..675 .883 2. it is the choice for many severely corrosive in dustrial environments such as: sewerage plants.0 837. neat cuts. easy cuts are handled well by standard cutting tools.. can be easily accomplished by conventional means. max. Inc.0 i I Copper Silicon Iron Magnesium Manganese Chromium Titanium Zinc Others Aluminum *Nominal 0.6 88.10 0. Exposure to Galvanic or Electrolytic A ttack: Aluminum conduit should not be direct-buried in earth due to un predictable soil conditions of moisture. Reaming.. as required by the NEC.0 1823. used according to accepted good practices. safer workability adds to the many advantages of rigid aluminum conduit at every step of installation.0 625. max.5 187.0 1343.0 144. aluminum conduit should not be embedded in con crete without approved protection because of the possibil ity of galvanic or electrolytic corrosion. Conduit Embedded in Concrete: In accordance with the NEe. Stray alternating or direct currents can aggravate the galvanic action. it should be given the same protection recom mended for direct·earth burial.10 0.4 1 1% 11. in accordance with the NEC.7 251. to 0. Galvanic attack can occur when the aluminum forms the anode of a battery created by twO dissimilar metals in contact with an electrolytic medium.15 max.20 0. The conduit should not carry any of the ground currents associated with normal operation. Such chlorides can originate from concrete addi See also ChapleT 11 sections describing methods of installing cable in conduit and calculations of pulling tension.45 0.1 4 5 6 ! I Galvanized Steel 80. A tow resistance conduit run should be maintained. which are generally used.10 0.5 203.0 IMe Type I Percentage Limits per Industry 57.0 235.0 Standards 78. use of sea or brackish water. 17·6 Threading: Standard dies.10 0.0 697. for smaller sizes (as for smaller steel con duit). Remainder • Alloys with up to 0.5 246.related structural applications of aluminum TABLE 17·1 TABLE 17-6 Composition of Aluminum Conduit Alloy (6063) Weight Comparison per Hundred Feet* Trade Size I Rigid Aluminum Y. water treatment stations. If it is necessary to embed aluminum conduit in concrete.4 154. If it is necessary to bury aluminum conduit.0 393. 3 . or protective treatment. as may be required on steel cOn duit.35 0.5 71. Additionally. Also.9 630. an IS-tooth hacksaw is recommended for easy. to 0.4 54.7 118.6 max.0 112. I. use of unwashed beach sand or other saline aggregate and similar materials.1 % 37.40% copper are ac· ceptab!e to Underwriters' laboratories. Hazardous Locations: Requirements of Article 500 of the NEC covering conduit installations in hazardous locations can be easily met with properly installed rigid aluminum conduit. factory-applied PVC coatings are commercially available.0 541. eventually destroying the buried or embedded conduit.0 483. tives (to speed setting time). Because its resistance to corrosion is greater than steel's. The characteristics of aluminum conduit facilitate the installation of a tight explosion-proof system. 2. max. for use in rigid aluminum conduit and fittings.0 338. The circuit neutral should be grounded at one point and be insulated from and have no electrical contact with the conduit.3 106. filtration plants and chemical plants. to mitigate the corrosion of all metallic conduit embedded in concrete: Cutting: Fast.9 max.0 176. possible presence of strong electrolytes and stray electrical currents. 3.0 1003. Stray currents can aggravate the corrosion. severely damaging the con duit. Power saws and cutting wheels work fast and neatly on I-II2-inch and larger conduit. 3. it should be thoroughly coated with coal-tar epoxy Or given a layer of half-tapped approved tape. 28. thread aluminum rigid conduit faster than (j .2 478. The concrete should contain no extraneously added chloride. max. Installation 01 Aluminum Conduit" Easier.6 305.2 2 2.3 295.10 0.0 561. however. Standard cutting oils of known good quality are recommended for uniform threads. To simplify field joining. Measured temperature rise vs time for aluminum and steel conduit under shari circuit conditions. steel and with less effort. and a permanent. Propelled Lines: C02 or air propelled lines of nylon or other plastic shoot through all sizes or rigid aluminum conduit. a system that can be easily dismantled. 17-1.up to 100 feet . speedometer-type steel cables. Hand threaders produce good threading on smaller sizes.polyethylene fish tapes can be used effectively. if not used carefully. both threads of every length of rigid aluminum conduit should be lubricated in the field if not lubricated at the factory. low-resistant electrical ground path. Small Conduit: In sizes up to i-il2-inch and on shorter runs . " 500 ~ ~ '" n E ~ 800 400 600 300 100 400 Aluminum 100 200 0 0 I ! I ( 2- 4 ! I 5 6 ! 10 Seconds inch conduit . dies with 300 to 350 rake angles should be used. 17. (On field-cut threads. Bending: Sweeps. cross-overs. Also recommended are round.rigid aluminum conduit C F Steel 1600 BOO 1400 100 1100 600 '" 1000 . elbows.7 . can be used on all sizes and operated at maximum drive speeds.!!1 tr '" .. When using top drive speeds. Mechanical or power benders can be used on all sizes. Use an EMT bender one size larger than the conduit. provided they have shoes and action similar to those of an EMT bender. safer techniques that work well with aluminum conduit have been intro duced for fishing and pulling through all types of wire ways. a reliable quality lubricant containing zinc or graphite should be used). scrape and cut conduit walls. of course.22. and for longer !oollife. flexible. Stan· dard hand and power benders produce smooth and exact bends in all conduit sizes. Standard EMT benders can be used on I-inch or smaller aluminum conduit for one-shot bends. Proper lubri cation aids in assuming tight joints. offsets-every type of bend is easily made in rigid aluminum conduit. Pulling: Modern equipment and faster.200 amperes) Fig. Use of flat steel tapes should be avoided' since they tend to jam in the bends or. Joining: Adequate electrical conductance in a conduit sys tern requires tight joints. Power threaders. Aluminum conduit is usually made from aluminum alloy 6063.020 0.related structural applications of aluminum TABLE 17-8 Atmospheric Corrosion of Solid Metals over a 10 Year Period Atmosphere ~ Desert Rural Coastal Location Aluminum* ___. Expansion loints: Linear expansion of rigid aluminum conduit is not a factor in most installations.068 0.047 0.028 0. La Jolla. expansion fittings might be needed. **Prime western zinc.001 0. good aluminum fittings result in a superior installation.190 0.000 0. New York. (Degree-feet is the length of the run in feet mUltiplied by the temperture rise.005 0. OF.031 0. Pa..046 0. Table based on ASTM data (Committee report).. N. Lead 0. Larger Conduit: For pulling large conductors through larger conduit or longer runs.016 0.004 0.025 0. reduces ground current losses and voltage drops. in fittings as well as conduit.190 0. Pa. Arizona Industrial State College. Key West. * Aluminum 1100.052 0.017 0.042 0.Y.) .022 0.009 0.. Cal if.000.________ 1 Zinc ._ j. A good general rule: use an expansion joint if the degree-feet of a run may exceed 10. Fla. Steel pulling cables. Industrial Altoona. especially when old or frayed. Coastal ____L_ Copper I Corrosion rate shown in average mils per year.023 0. polypropylene rope is recommended. Fittings for Rigid Aluminum Conduit: Although galvan ized or plated steel fittings are permitted by the 1987 NEC and can be safely used with rigid aluminum conduit. generally considered to be equivalent in corrosion resistance to aluminum 1100. If a straight run is unusually long or subjected to extremes of tempera ture.019 0.010 0.021 0. And aluminum's 17-8 non-magnetic property. An all-aluminum conduit run has better conductivity and provides safer ground protection. can damage steel or aluminum conduit.027 Phoenix. high strength-to-weight ratio possibilities and high corrosion resistance has been accepted as an ideal material for street and highway lighting poles. Aluminum lighting standards are available for mounting luminaires up to 50 reet above the roadway with various arm configurations. On interstate highways it must be safe enough that its base breaks away when hit by a subcompact car at 20 mph. This is based on very sound COn siderations. It must resist the effects of industrial and traffic induced corrosion for 25 years at least. The former is fabricated by spin tapering extruded 6063-T4 tubes about 1/8" per foot and then artificially aging to the T6 temper. I! must be strong enough to resist high winds. It must be designed to provide inherent concealment for transformer and wires or protective components and for easy cleaning of lenses and replacement lamps. and Station Structures This book would be incomplete without a brief mention of the specialized structures related to the everyday use of aluminum electrical conductors. chemically or electro chemically. taking advantage of its good looks. Research programs have led to the develop ment of high strength aluminum alloys. extruded and cast alloy sections. bases and arm holders may be 356 casting alloy (Fig. light weight. Although aluminum has a pleasing appearance in its natural state. I! must be low in installation and maintenance costs. aluminum lighting standards form an as sembly that is rugged enough for the severest service. We will discuss just a few of these in this chapter. coupled with aluminum's traditionally known high resistance to corrosion. 18-1). or Christmas street decorations mounted from special brackets or used for a number of other accessories. new effective structural designs and strong. buffed or electro brightened to give a wide range of interesting and attractive appearances. It must be graceful in appearance and at the same time unobtrusive and uncluttered. It must be versatile in that signs (either permanent or not) may be hung on the standard or flag poles provided at the top. The surface can be polished. Recent years have witnessed a steady gain in the use of aluminum for many types of structures required by the electrical industry. Shafts are usually 6063-T6 or 6005-T6 extrusions Or 5086-H34 sheet. yet light enough for installation crews to handle without special equipment. Transmission Towers. Uniform cross sectional lighting standards can be made in any cross sectional geometry with extrusions or press forming of sheet. With the high strength-to-weight ratios provided by these alloys. hard refractory coating not only providing a very high degree of corrosion resistance but a surface that can also be impregnated with permanent coloring dyes. luminaire arms are 6061-T6 or 6063-T6 extrusions. it can be made to take on a variety of finishes applied mechanically. I! must be tall enough to cast its light from the luminaire it carries above any normal eye level and the angle of sighting along the thoroughfare. economical fastening and joining methods. Aluminum lighting standards may be of a tapered or uniform crOSS section. 18·1 . Aluminum Lighling Standarns A lighting standard is many things to many people. account for the wide use of aluminum structures today. This has been a steadily growing application of aluminum since the 1940's. Modern aluminum lighting standards are a combination of sheet. The profile may also be fabricated from trapezoidal sheet sections pressformed and longitudinally welded into a tapered shaft. (See Table 18-1).Section VI Related Structural Applications of Aluminum Chapter 18 Street-Lighting Poles. Aluminum lighting standards can be designed with classic simplicity so that they may complement virtually every type of architectural or landscape background. Aluminum. These factors. Through the anodizing process the natural surface oxide film can be deepened and strengthened to a substantial. Aluminum lighting standards extend their versatility into highway safety by reducing vehicular damage and driver injury in collisions either as an intrinsic aspect of their design or by the simple installation of accessory breakaway devices. c 15...):: '" .=-'~~'- ---~linaire J Luminaire support arm \ Luminaire support arm attachment ..c'"c :J 0 .:::::::.l. AHoy..... . ..relafed structural applications of aluminum I.: --Shaft /Handhole I IO~Bas.:::::::.... 18·2 ..r:.2! " . Typical street lighting standard using aluminum. 18·1.. tI) :. and Temper Spun Aluminum Welded Tapered Sheet Standard 6063-T6 6005-T6 Aluminum Standard 5086-H34 Fig._ ~:!::~.---Arm length---j -. _"-..c . '" .c '"' . 01 x 0.5 x 7.156 8)(6)(0. 592 x 0.188 9 x 4.Q1 x 0.6 ! 10 x 6 x 0.59 )( 0.5 x 12 x 6 12 x 6 13.76 x D.76 x O. 5112 x 6 x 0. Still more time can be saved by using helicopters to transport components or even fully assembled towers.219 12 x 6 x 0.219 8)(6)(0...170 9. 13. The two factors of (1) dramatic reduction of installation costs and (2) virtual elimination of mainte nance costs account in large part for the present serious consideration given to aluminum towers_ Surfaces of alu minum transmission tower structures can be treated with various coatings to meet "non-glare" requirements often specified.. 10 )( 6 )( 0.188 a J( 6 )( 0. Dangers of repainting "hot line" towers (or the expense of de-energizing to make them safe) is avoided.219 .135'.135" 10 :. With the many advantages of aluminum's light weight..5)( 6.18B 10 x 6 )( 0.219 i3.135 6063 i B )( 6 I 30 i 3' ! i r 2S 40 1I 600S : 5006 6063 6{JOS 30 3S 45 40 50 45 5006 6063 ' i ! : : : 6005 ' 5086 Ii S063 \ 6005: 5086 ' I 6063 i I i '6005 I .250 .'BS 8 x 6 x 0.188 i 9. 10 x 6 x 0. Arm 8 ft. Arm 12 ft. Structural angles in sizes from 2" x 2" x 3/16" to 10" x 10" x 1'14" and plates in thicknesses from 14" to 34" were employed using the excellent structural alloy 6061-T6_ Since pound for pound. the advantages of special component shapes over conventional structural shapes became apparent_ More opportunities in design in novation and economy are made available to the designer of transmission towers by aluminum than by any other material.5 :.156 : S x 6 x 0.59 )( 0.48 x 0.34 x 0. then transported easily and quickly to erection sites.250 .34 )( 0. maximum tor sional rigidity and radii of gyration can be realized_ And. Thus.312 10)( 6 x 0.1:35 . would require highly expensive rolling equipment and operations.188 10 x 6 )( 0.5 )( 6. Even without expensive painting and repainting. can be fully offset in some cases because of lower field erection costs plus credit from much lower maintenance over the life of the structure_ Also there are circumstances where interruptions of serv ice for maintenance work cannot be tolerated. I "'All dimenSIonS" are for poles designed for 90 mph wind IMd..312 x 0.TABLE 18-1 Typical Aluminum Highway light Standard Dimensions jMoUriting 1 $h.It IS x 0.219 .06 x 0.. Although aluminum cross-arms had been used in com bination with steel towers for a complete transmission sys tem before 1950.18$ 9 )( 4.5 x liL01 x 0.1$6 9 x 4.te .312 12 x 6 x 0. it is to be ex pected that the shop-fabricated cost of an aluminum tower will be higher than for a comparable loading design in steel. Bx6xO.312 8x6)(0.135! 13.156 10 )( 6 )( 0.170 13. Weight Reduction: Aluminum tower structures afford weight reductions of 50 to 75% from steel structures having equivalent capabilities.. however.135 x 0. high corrosion resist ance.188 8 )( 6 )( 0. 6 x 0.17 x 0.188 10 )( 6 )( 0.135 12 x 6 x 0.312 10 x 6 x 0.219 13. corrosion-resistant aluminum retains its good looks and remains structurally dependable longer than any other metal.5 x 7.219 : 12 x 6 :.35 9. Length Alloy : Height ARM OUTREACH f-- ! Singl" Double x 0.U : 13.135 10 )( 6)( (USB 10 )( 6 )( (UBS 10 )( 6 x 0.59 x 0.5 x 7. Lighter. on the other hand.17 x 0.135 Double S x 6 x 0.156 12x6xO. conventional erection equipment can be used.250 :10x6xO.250 10)(6xO.5 x 6.170 i 10 x 6 x 0. Aluminum Transmission TowelS Use of prefabricated metal towers for 138 kV and higher transmission is widespread today_However the traditional place held by steel in tower construction due to its high strength and relatively low cost is now be ing effectively challenged by selected high-strength alu minum alloys such as 6061-Tu_ The keys to this challenge are high strength-to--weight ratio.135 : 10 x 6 x 0..156 13.. multi-form shape extrudability and reasonably low.11 x 0.04 x O. With extruded aluminum structurais.52 x 0.92 x 0. except those marked ". --~ ! I 15 ft..17 x 0.!35 13. 10 x 6 )( 0.5 x 6.59)( 0. 5086 : Slng.1 x 5.5 x 6.5 x 7.219 7.250 13.135" Sin9le B )( 6]( 0.135 8 x 6 )( 0.5 x 8.--~.135 i 13.11O)(6xo.5 x 8..135 8 .:th asterisk whie!'! are deSIgned for 80 mph load.219 9.250 10 x 6 x 0.375 8 x 6 x 0.94 x 0.1 x 5.219 8 x 6 x 0. .219 13.188 9.375.312 ! 10 )( 6 x 0.156 9 x 4.1 x 4. 12 x 6 x 0..135 Doubl~ 8 x 6 J( 0. as well as faster methods_ Lightweight alumi num structurals can be assembled into components Or complete towers at convenient locations.17 )( 0.156 9 x 4.375 10 x 6 )( 0.94 )( 0.1a8 I 10 x 6 )( 0.170 i 12x6:<0.5)( .135 . . aluminum represents a sig nificantly higher metal cost than steel. A.01 )( 0. stable prices. however. transmission lines can be designed more 18·3 .1. These coatings need little or no maintenance in service.135: 13.59)( 0. This increase.135 10 x 6 x 0.1 x 4.t!.188 13.156 13.135 12 x 6 x 0.1SB" . Extrusion DeSign Capabilities: As designers and users gained experience with aluminum towers.5 >: 5. since both assembly and erection are Simpler with alumi num structurals.34 x 0.25 a )( 10)(6/(0.250 12 x 6 x 0.15. shorter schedules are easily met when installing any type of transmission line_ Corrosum Resistance: Pre-painting inspections.375 10 )( 6 x 0. 10 x 6 x 0.250 6 )( 0. .219 10 x 6 x 0.312 8)(6)(0.188 10 x 6 x 0.135". initial painting and subsequent upkeep repaintings are unneces sary when aluminum structurals are used to build trans mission towers.156 I I 9 x 4.219 13. 7. the unique structural shapes into which aluminum can be extruded can be designed for optimum efficiency_ Extrusion dies made to design specifications add ouly negligible amounts to the cost of the line system_ Made-to-order steel members.m 10 ]( 6 x 0.219 13.188 9 x 4. 0.04 x 0.1 )( 4.52 )( 0. This weight advantage of aluminum works as an im portant cost reduction factor in the construction of trans mission towers. the first all-aluminum tower lines were placed into operation in 1959 by several utilities_ These early aluminum towers were of the self-supporting type similar to existing steel tower designs.5)( S.. this factor alone justifies the use of aluminum. it is a very economical structure to assemble.V mounted On a guyed verti ca l mast. Guyed-Y towers built with extruded aluminum struc turals wei gh only 25 %. Design of a guyed. This spread. of self-supporting steel towers designed to same performance specifications. The " Delta " configura tion has an electrical and lower noise advantage over the naf and vertical configurations . 18-2): A guyed-V tower is basically two guy-supported vertical masts ha ving a co mmon footing and supponing a horizontal section for carrying electrical conduc tors and overhead ground wires. 18-2. the 3-pole design provides a separate pole to su pport each phase of the line system. For tall towers. Because aluminum guy-supponed line towers use guy wires as tension members. These 4 lower. and for towers which will have to withstand heavy wind loads. (A nd the weight which has 10 be carried by the tower masts is reduced as the spread between the vertical mast s and guy wires is increased . ca n be made as wide as the right-of-way will allow. And a guyed-V. the only shear load remaining on the tower foundation is that of the wind load on the slim vertical mast. But is also has 4 guys stabili zing its lower. it has less column length-and the effect of wind on a long. Guyed "V" aluminum s/ruc/ure on Indiana & Michigan Elec/ric Company 765 kV line. 18-3): A guyed-Y tra nsmission tower can be described as a guyed.Y transm ission tower weigbs con siderably less th an an eq uivalent guyed-V towe r. 18-5) : This design is similar to the guyed "Delta" with further advantages in the unique design '. has fewer members than a guyed-V. 18-4): This design has all the advantages inherent in the gu ye d "V " and "Y". Guyed "Della" Towers (Fig. Aluminum Transmission Tower Designs Guyed "V " Towers (Fig. eac h conductor on a 3-pole guyed alumi num transmission tower traverses the angle in the line supported by its own pole. they wei gh substantially less than equivalent aluminum self-supporting towers . As with other 3-pole towers. increasing the spread of the guy wire attachments.V towers built with extruded aluminum struc turals average approximately 30'10 of the weight of self-supporting sleel structures designed to the same performance speci ficat ions. . 18·4 Introduc tion of aluminum guyed "pole" transmission towers further refined this proven design.Y lower is such that overturning moments are resisted by guy wires serving as tension members. Three-Pole Guyed Towers (Fig. inside guys tak e shear from a gu yed-Y tower at the junction point where the ve rtica l mast meets the upper V section. Having a single mast requiring fewer pieces . and by latticed masts serving as compression members. on an approximate average. fo r reaso ns noted on earlier pages.Y tower. Furthe r. which represents the arm of the resisting moment. unsup ported column varies as the squa re of the length of the column. An aluminum guyed. 18-6): Sharp angles in direction of a power transmission line pose problems best solved by the 3-pole tower. Thus. therefore.related structural applications of aluminum easily and with less risk of problems in the field . Like the V lOwer.) Guyed "Y" Towers (Fig. Guy wi re s for the poles ca n be placed easily at tbose points where they will most effectively ove rcome the tange ntial forces created by the angles in the line . minimizing the torsional forces and reducing guy tensions. Fig. Guyed. Recommended for lines having changes of direction greater than 150.V tower. the guyed-Y de sign will satisfy performance requirements at co nsiderably lower cost than a guyed. vertical section . weighs less than an equivalent self-sup porting tower. Guyed "Gull Wing" Towers (Fig. the guyed-Y has 4 guy wires serving as tension members of its upper sectio n. because of its unique geometry. The guyed. 18-5 . Guyed "Y " aluminum structure on Louisiana Po wer & Light Company 500 k V line. / 8-4. towe rs. /8-3.street lighting . Fig . Guyed "Della " aluminum structure on South western Electric Power Company 345 k V line. station structures Fig. 18-6 Fig. This holds true with any design of guyed tower and regardless of whether the con ductors are strung by V-strings or by Single-string. the guyed tower-with its small footing and easily placed guy anchors-ean be installed with relative ease. therefore. Three-Pole guyed 345 kV aluminum tOwer on Southwestern Electric Power Company line. Substantial savings in foundation costs are possible with guyed transmission towers. An aluminum 3-pole guyed angle tower weighs approx imately 20"10 of a self-supporting steel angle tower. requires costly multi-purpose founda tions. In terrain too difficult for locating conventional towers. Since each can be installed with little concern for the others. than self-supporti ng towers. Guy-supported transmission towers have radically smaller bas". designed for both compression and uplift. however. time and effort are saved and costs reduced. The central footing for a guyed tower need be designed for compression only. 18-5. in addition. guy anchors. for uplift only. Fig. piles and noating bases are also used . on the other hand. Guyed "Gull Wing" being set with "Flying Crane" on the Northern States Power Company 500 kV line interconnecting with Canada. pre-cast concrete and poured in-place concrete .related structural applications of aluminum On a guyed tower. Guyed transmission towers require no more right-of way than equivalent self-supporting towers. Three types of foundations are generally used for guyed towers. Screw anchors. A self-supporting tower.galvani zed grillage. . Foundations on a self-supporting tower. free swinging insulators. 18-6. are precisely interrelated-to each other and to the tower legs-and must be designed and installed with a high de gree of exactness to avoid unnecessary stresses. easily adjusted guys serve as tension members so that anchor points and central footing are not dependent on one another. since the towers' supporting guy wires require no greater width along the right-of-way-usually less than needed for mid span blow-out of the conductors. hard-to reach locations. towers. Fig. Semi/lexible lower of aluminum deflecls under load. thus is able to denect under longitudinal loads produced al (he conductor and ground wire a1l3chmem levels . easily installed crOSs-arm . 3/ 16 to 3/ 8 in. since tall wooden poles are continually becoming scarcer and more and more costly. Two types of alu minum cross-arms are being used for this purpose.street lighting. in thickness. Semi·Flexible Towers (Fig. The alu minum version is similar in outline to X-braced wood pole structures but has columns and cross-arm assemblies that make maximum use of extruded shapes designed specifically for this application. but particularly at difficult. 18-8. this permits greater movement under given loading conditions than with steel. of extruded 6061-T6 alloy makes a simple. aluminum has far greater elasticity and flexibility than steel. station structures In H-frame towers. self-supporting types of transmission towers. for any given length of line. When the design of a system calls for self-supporting !owers--<oither 3-or 4-legged-the light weight of alumi num provides installation advantages at any tower site. 18·8): The "old reliable" H-frame transmission tower takes on new uselulness when con structed with extruded aluminum structurals . It is built with a transverse side as slender as stresses allow. Thjs is especially so with line voltages through 345 kV. Variations of the all·aluminum H·frame include wooden poles with aluminum cross-arms and aluminum pole structures with wooden cross-arms . In a semi·flexible trans mission tower. \. And fewer towers mean fewer sets of hardware in installation costs and fewer insulators to service and replace. Fewer towers 3re needed. 8 to 10 inches in diameter. For the heaviest load· ings. Such denection allows a portion of the unbalanced load to be carried by the other conductors or ground wires. 18·7 . strong. It can be built not only taller than usual wooden pole H · frame towers but also stronger. As a structural material . ~ " I ~ • • • Fig. latticed cross-arms of extruded struclural shapes in aluminum alloys are available. 18-8 is of a typical aluminum self-supported transmission tower (also called free-standing) . Economies in tower weight result as well as substantial savings in erection. Conventional Self-Supporting Towers: Overall weight re ductions averaging 55 to 60 percent can be made by using extruded aluminum structurals instead of steel in building conventional. H-Frame Towers (Fig. Fig. A single tube. therefore. 18·7): The semi·nexible trans· mission tower reflects a unique basic tower geometry . the economies inherent in alumi num because of its light weight and minimal main· tenance needs are added to by generally lower material costs. 18·7. Helicopter leaving assembly yard wilh "H" frame on Public Service Company of Indiana 345 k V line. Thereafter the virtual elimination of mainte nance costs for aluminum structures is an important bonus factor.related structural applications of aluminum Savings realized from aluminum's minimal need for maintenance are especiaJly pronounced on lines using self-supporting towers."e dna aluminum top. 250 ± D-C line crossing North Dakota. where tower installations virtually impossible by ordinary meth ods have been completed with relative ease by the versa tile aircraft. 18-8 than steel. Station structures fully designed in aluminum will have the following economic and performance advantages: Light Weight : The use of aluminum can mean a reduction in weight of up to 70% over a steel structure. Even the erection crews on tower jobs can be trans ported by helicopter-Io and from Ihe lower siles and from site to site-fasl. Components of aluminum transmission towers bundled or partly assembled-can be lifted. a comparable aluminum structure can oft ~n be completely erected at a cost equal to or somcwhat less Aluminum lowers can be assembled on the ground al installalion sites and the. shifted or moved by helicopter. Square Bulle Electric Coop. The internal guys act as structural members. Under minimal unbalanced longitudinal loads a pattern of bolts shears. Like an all aluminum tower. This has been most dramatic in rough country. 18-10): This structure satisfies conditions where external guy wires cannot be used. Self-Supporting Composite Towers (Fig. it requires no maintenance in Ihe dangerous and high-cost vicinity of the conductors. Use of 'copters is especially helpful when running power lines Ihrough rough country. In all types of country. When guyed. 18-9): This Slructure. The structure is designed using a rotating crossarm. helicopters have proven highly economical. . first.. 18-11): The self-supporting (('wer of conventional design can be built with steel b. however. has all the ad· vantages inherent in an aluminum structure. no mailer how inaccessible Ihe sile might be. and aluminum tower crews are using them in many different operations. Single Mast Self-Supporting Towers (Fig. Des pile a higher cost per unit weight. 18-9.Y towers are being installed. reduction without loss of structural inlegrity. a weight The weight advantage of aluminum can represent a major saving in erection costs. Aluminum allows a greater amount of sub-assembly prior to shipment and . allowing Ihe arm 10 rOlale reducing Ihe longitudinal and torsional load on Ihe mas I and minimizing any domino effect due 10 structural failure. This composite variation minimizes the cost premium. designed for simplicity and Iimiled right-of-way widths through urban or farm areas. Towers assembled on pipe racks in marshaling areas reduce heavy equipment needs and dramatically increase pro ductivily.. efficiently in any terrain. a 'copter can be used. Helicopters and Aluminum Towers: The transmission line industry has developed ingenious and valuable short-<:uts in its use of helicopters to transport and erect lightweight aluminum transmission towers and components.l a helicopter can be used to tilt the towers easi ly and quickly to vertical positions. Assembled lowers can be carried by 'copter from assembly points directly 10 tower sites and set. increasing transverse strength with a consider able reduction in structural members. Fig. Aluminum Station Structures Most of what has been presented above on the ad vantages of aluminum transmission line towers is directly applicable to aluminum supporting structures used in out door electrical substations. to erecI Ihe vertical mast of Ihe Y. The upper part of Ihe Y can then be lifted by helicopter and a((ached wilh perfect alignment to the vertical mas!. Internally Guyed Self-Supporting Towers (Fig. however. /8-11.street lighting. where one man can lift an aluminum section. The relative ease of extruding aluminum makes it possible to offer special as well as standard structural shapes and sizes. equip ment and shipping costs are possible with aluminum. Appearance: Because of their excellent corrosion resist ance and freedom from rust. aluminum substations stay attractive without major maintenance. And unlike steel that eventually rusts and requires painting. there is no need to run the risk of having paint ers climb or work in proximity to energized parts . Properly designed with the new. salt air and indus trial fumes and does not require protective coatings. low silhouette. Aluminum tOP on sleel body eliminales costly Fort Worth. Since aluminum never requires painting. station structures construction site erection . they offer improved appearance to metro politan and suburban areas. The need for high cost heavy equipment also may be drastically reduced or often eliminated. A further cost reduction is possible because aluminum's exceptionally high conductivity can simplify stn. Assembled sections that would be difficult to handle in steel are easily handled in aluminum. Fabrication. Thus faster erection times and reduced labor . Costly and inconvenient shutdowns in the interest of safety for painting purposes are unnecessary. /8-/0. More work can be done in the shop. Texas. Safety Factors: Safety is a very important advantage of aluminum substations.ctural grounding and may eliminate a ground wire system. maintenance on 230 kV double circuit tower. thereby reducing the number of man hours in the field. Pacific Cas & Electric Company 500 k V "inter nally" guyed structure in Ihe lest rack al Adelphon. Fig. This means aluminum can i· -rr '-'~ Fig. The savings by not having to repaint the structure with attendant costly shutdowns may more than pay for the cost of the aluminum substation structure over a period of years. 18-9 . For example. Corrosion Resistance: The economy of aluminum's cor rosion resistance should also be considered. Inc. aluminum substations re main modern looking year-in and year-out with a mini mum of maintenance. Aluminum re sists chemically corrosive atmospheres. towers. a similar steel section would require two or three men. l8-/3. 18-10 .related structural applications of aluminum Fig. All-aluminum s ubstation designed 10 operate at 75U kV. 18-12 shows some of the structural shapes readily extruded. A tungsten electrode with the filler rod being fed by hand as in gas welding. 18·12. depending on the alloy and temper. the rivet alloy selected should have equal or greater corrosion resistance than the alloys being jOined. These rivets are cold driven as received. This is a fast method and is used also for automatic set-ups. Aluminum coated steel bolts. aluminum bolts of high strength alloy 2024-T4. towers. when cutting and drilling operations are required. The rivet allOY should also be somewhat softer. See Specifications jor Aluminum Structures and Engi neering Data jor Aluminum Structures. High Scrap Value: An important economic factor to con sider is aluminum's recognized high scrap value. anodized and either chromate or nickel acetate sealed. 18·11 . be tailored to fit many different design requirements that utilize sizes. Rivets offer the advantage of an approximate 15 % shear advantage over aluminum bolts. stotion structures H Fig. shop riveted sub-assemblies eliminate defiections caused by bolt slippage. Butt seams offer the highest efficiency. They are available in sizes ranging up to I" shank diameter. A consumable electrode of aluminum welding wire fed through the inert gas envelope. To avoid corrosion. Alloy 6063-T6 has iess strength and finds principal use in redundant structural members. shapes. a more efficient use can be made of the metal. two methods are most commonly used: I. When a structure has fulfilled its useful life. Alloy 6061-T6 is a high strength metal used for tension and compression members. and galvanized steel bolts may have applications under certain conditions. aluminum is a much easier metal tn work with than steel. Structural Design: Fabricators of aluminum structural components and assemblies maintain complete engineer· ing design information which is available on request. Since there is no galvanizing. Tables 18-2 and 18-3 contain condensed but rather complete technical and availability information on the above two structural alloys. no special precau tions are necessary tn prevent corrosion after field cutting or drilling. However. The Aluminum Association. and it is easier to handle because of its light weight. Welding: All types of inert gas shielded arc welding (not requiring a ffux) are acceptable for aluminum. Additionally. (GMA W) The strength of the weld generally varies from 60·90 percent of the original strength of the parent metal.street lighting. Structural design handbooks for aluminum have been prepared and published by several manufacturers and by the Aluminum Association. aluminum lock bolts. and these may be obtained by writing to them. aluminum will bring a much higher scrap return than other structural materials. In the field. In many cases. Recessed nuts preclude the need for washers. Fig. Extruded aluminum structural shapes. are used with recessed nuts of alloy 6061-T6 lubricated with a wax coating to prevent galling. (GTAW) 2. Riveting: In substation construction alloy 6061-T6 rivets are recommended because of their high shear value. Aluminum Structural Alloys: The two most commonly used aluminum substation alloys are 6061-T6 and 6063 T6. Normally. It is accepted practice to restrict bolts to one size in a given structure. 5/8" and 3/4" diameter bolts are recommended. Fastening Metlwds: Bolting-Where bolting is the de sired method of fastening. proper arrangement of the seams may compensate for possible loss of strength. and lengths unobtainable with steeL As a result. C = limited Weldobility bc«uJse of crock 5en.000 All up thru 8.t otmospheres without protection.999 over 0. \vELDABllITY4 ~.nstonce of failure in service or in loboratory tests.yt 0. T451. aM r~Otive foting$ in det:reosing order (If merit.:eM ~ ~::2 ~ '3~u ~ Ii ~ 0 ~ .010-4. ** Val1Jes (11$0 apply to -T6511 temper.Q25·0.(lmmonly uwd welding methods hove been developed.100 10. g TYPICAL APPLICATIONS ' " V) V) B A A Heavy-Duty Structures Requiring Good Corrosion Resistance.100 10. limited foillJres in loboro tory testt of lang tronsver$8 Specll'l1enS.100 10. T4510.itMty or lou in resistance ttl corr(lsion and mechonicol properties. O'her stt9ngth properties: are corresponding minimum ex pected volues. t For deflection ca!c:ulotlons an average modulus of elosticity is used. 2 Stre.. limited foilures in lobora. T6510. tory testt of short ttansverse spetime"s. direetlon relative tc groin structure. t Flu Typical Characteristics and Applications r RESISTANCE TO CORROSION ALLOY AND TEMPER " ~ ~ c " .i 35 35 35 35 35 i 27 27 24 i BEARING I ! 80 88 88 88 80 56 56 ~I '" Most product. F"." Il :cu u C " ~ u ~ ~ « D C A A A C ~ ~_e 'j &. . = 18·12 ~ ].100 10.~ 00 ciiuu :J:. Truck and Marine. A B A A B C 1 Ratings A through E Ole relative rotings in decreasing order of merii. Weldoble with speciol techl'liqlles cr for specifU! oppli<otlon5 which 8 jU$fify preliminary trials or testing to develop welding procedure ond weld performance.100 ksi SHEAR k. = . F".999 42 38 42 42 42 38 35 35 35 35 35 35 Product*' ! Compressive . ond A through E for Mochineobiliry. . 4 R(ltings A thrallS" 0 for Weldobiljty and Bcczeobility ore relotiw toting$ del1ned os ~ollow'.i ksi ksi 35 27 24 27 20 20 20 20 20 20 88 58 56 10.!. vere stress. T651 -T6 ·T6 -T6 Sheet 8. T652. Railroad Cars~ Furni~ ture# Pipelines 0= limited 5erYice foifl1re5 wah $u:ttoined longitudinal or long tran'. & No known instQf'!(e of failure in setvice. T651.related structural applications of aluminum TABLE 18-2 Alloy 6061 Minimum Mechanical Properties-Values Are Given in Units of ksi (1000 Ibjip') Alloy And Temper 6061.000 0. 0 6061-0 T4.T6.md thkkness ranges are taken from The Aluminum Assodatlon's "Aluminum Standards and Data.PRESSION I Modulus of F" F".5% sodbm chloride otternate immersjan test.T6./ are minimum $p«ifled values of ultimate (uJ end yield {y) tensile (r) strengths. 3 Rotings A through 0 far Workability (cold). F•• Elostidtyi E ksi ksi k. C = Service foifutes with substained ten. based on exposures 1'0 lCdium chloride solution by interml1tent sproying or lmmersIon.worrosion crocking rotings are based on service experience and On lobo(otary tests of spedmen$ e)(~ to the 3.100 10.." alld FtJ. A = No known . Alloys with A and 8 foting. numerically this is 100 k$i lower than the values in this column. T4511 T6. T6510" . 0 and E ratings generally should he protected ot leo.5OO up thru 0.COM. FtuT ksi F. Alloys with C.sio" nrc" acting in .h(ltt ttOt'lt vene. Sa r Drawn Tube Pipe Pipe i TENSION Thickness Range* in. can be used in indU$frial ond seo~oo. T651 ·T6. T6511 B B B c~ o '" . A = Generally weldoble by all commercial procedures: and methods.!. Plate Extrusions Rolled Rod 8. o N(I (.t on foying surfaces. .kness ranges ate taken from The Aluminum Association's "Aluminum Standards and Data..column... F.Imerieolfy this is 100 bE lower thon the yalues in this . 18·13 .5 13 12 19 9 46 44 63 26 24 40 ]0.i 16 1. station structures TABLE 18-3 Alloy 6063 Minimum Mechanical Properties-Values Are Given in Units of !lsi (1000 Ibjin2 ) Range* Alloy And Temper 6063-T5 ·T5 ·T6 TENSION Thickness Prodvct* Extrusions Extrusions Extrusions COM· PRES· SION Ftut Fwt ksi ksi 22 21 30 up thru 0. .0'_ kWABILlTY4 I A A A A A 0 ~og '" a.uu ~~ ~ 0-" " 5e ~ ~ ~ A A A A A -t~ o 0 B B B C C " " . Typical Characteristics and Applications RESISTANCE TO CORROSION ALLOY AND TEMPER o~ '0 Q. towers.500 All SHEAR F" F.]00 10. 1832 A A A A A ~ ~ :. other strength properties are corresponding minimum expected volue$.i 16 15 2.5 iCompressive : Modulus of BEARING Ela. Fb• E ksi kSf ksi ksi k. t For deflection calwlotion$ on QVerog(! modolus of eloitic:ity is l.100 k. . * Most product and thu." t flu and Ftv or~ minimum specified values..100 10..S v «" 0 ~ D D C C C TYPICAL APPLICATIONS "'" a0 0 ~"-. c " (!) 6063·11 T4 15.5 14 ..IlCily* Pipe 8. T831 . l'u.11.street lighting.5 2. ~ 0 '0" . " '""'''' A A Pipe Railing A A A Architectural Extrusions Furniture See footnob» below Table 18·2 on poge 18. F. ~~ .s.0500 over 0. V:..152 16 183.I$ed.. H19 with 6021-TSI reinfOt'CElmenl ASTM B 524 S\ltlS. 6-2n Transactions ?aper. 13-1 alkalis.-10 alums. 11·1 all-aluminum 1350 of various hardnesses in Class B. aoo 0 stranding. 3-15 anode. 7-2. 14-4 anodized foil. 3·.'4 aluminum Chloride.8 angies. 3-3 13so. tab4e 9-4 seide ratio for triplexec! s. 3-9 $!rand!ng arrangements. 13-63. 3~ M tiass of bare concentric-lay stranded conductors. 9-13 Schoo. physical and electrical prop erties. 13-34 . 3-19 bus conductor.. 7·5 primary. 12-7 acryIOOitfile-butadience!poiyvinyl-¢hloride compound.ldc ratio.conductor assembly." 2-3 non-heat-treatable 1·4. 1-4 1350 aluminum. strength of. 3-6 gro'J~ing. 3·21. 10-7 alternating Cl. 10-4. 3-20 6201-T81 and AGAR conductors. table 1-2 heat-treatable 1·4. 11-11 alloy 6061. 1-S-6 ANSI starldan:! ca-35. solid-round. mechanicar and electrical properties. 3-1 amid-imide pofymer enamel coating. tabk!: 1s. 11~12n aluminum. tables 13·26 to 13-32. tables i0-7A. 13~2j. effect of. 14~5 ampaci1y. 17·2 weight.. direct burial and buried duct table 10-9A insta!ed in air or in duct in air.. 9-3 conductOl cable. comparative cross-section for equal volume conductance. tensile and yield strength. 11-23 initial sag·tension values. 3-5 accessories for o>lerhead conductor. 1344n Tecllnical Paper No. Current-Carrying CaoacltY oi ACSR. ~ig. 7-2 installing.9·13n air-oven teSt. 5-26. table 4-4 1350-F. 13-2 13SO-H19. alum. table 4w24 aluminum conductor alloy.1W physical and electnce: prooerties. 15-4 anodi2:OO films. 3-4 strength raMg faclors. tabie 1(). suffix notations. 3-2 resistance multiplying factors.2O. table 4-12 in even AWG and kern. table 1. 13-11 paired. 34 alurrnnum to copper Connections. 3-15 alumina. 17":. 10-16 high-voltage cables with aluminum conducttn. GMR of. ~able 4-17 ACSFI. ~24_ 3-25 derating faclin on metal conduit. 11·5 aI\JI'l"IirIom 'IS. 1-' aluminiZed inner-core wires lor ACSR. table 4-25 aillminum wire. 13-46.Jflix nolations. 10-4 alumil"lJm cable aUoy. 17·1 1350 Me and standatd·strength ACSR conductOrS. 9-1 aciclc ratios for aluminum cabfe. 4-22 advantages of aluminum as a conductor. 11~23. 9-3 &:.3-19n Alcoa Aluminum Bus Conductor Handbook.1-5 alloy selection for caS! rotors. table 3-2 aluminum conductors stranded wiih aluminum cJad steel (AW} conductors.. 1347. table 4-6 physical properties.13-33 aerial eabIe assemblies. fig. table 3-BA underground distribution cable. 3·1. 3-19. a-l0 ACSR. iig. C37. remaining. 7~3 service drop. 1-4.ctor cable. lable 10-1 current-temperatur~rise gtaph. flg_ 6-3 composite conductor. adVantages. 3-22. 1-5. 7·3 aging of aluminum vs. Power Apparatus and Systems. electrical characteristies. physical and electrical propert\e$:.2 American Vlelding Society Ha'ldbook. 1953. 3-2 AAC. 13-27 alternating polen1ial. 7-4 aU-aluminum alloy 620. 13-22. 9-27 ratings for varying buS bar arrangements. comparative. 14-4 Aluminum Standards &. table 1-1 Aluminum Association. 17-2 aluminum magn&twire'lS.index A A Class of bare concentrIC-lay stranded corduclors. factots lor SDaCing adjacent cables.11 alloy 6061-T6. table ~1S composIte conductors. diarne1ers.3-1 compact-found. 15·-. table 10-21 value adjustment factors lor variatiOn Of alTlbient lem perature. iable 4-5 allowable pulling tension. pipe. steel. 14·2 technical advantages. 5·21 acoustiC fault deOOCtron.Te.-5 alloy oomposition 01 aluminum conduit. 2·1 alloys for ous coru1uC1ors. fig. iabte 4·8 all-allumlnum 135o-H19 Class AA and Class A stranded conductors. 3-3 properties compared Wt1h similar conductors. table 1~ alumifltlm wrought bus conductor alloys:. 9-2& high-VOltage aiumtn-. 40 and Schad. VIJ!¢anizoo. 17-5 Paper 59-897. C. copper.' electrical condUc1Ors in percent. table 13-2 a1uminum-t1>-alummum connect:iOns. 3-21 bare con(!uctors. Dec. B. 9-$.1. table 13-27 single-layer high-strEiflgth ACSR conductors. 13-1 Aluminum Underground Dr$tribution Reference Book. pt III (Power Appatatus and Syslems). 14-2 aluminum oxide. copper magnet wire. 3-6 mechanical properties of galvanized A. 9-13. 3-8n Paper. table 4·5 electrical properties of single·layer sizes.. Oct. fig 14-1 AlEE Paper S8-4i. 13-21 fig. 13-47 American Wire Gage.{o~ connection.4-13 aJl-aJuminum aIIoy-condUctors. emisswlty. 5-23 Alumowe!d conductors. 11·23 parallel (PAC). sun. 5-25. 13· 23 ratings. 9-13. fig. at. table 16-~ "marine.11-10 Transacbon$ Paper. economic advantages. v. f'9. laoles 4-19. 6063. 13-66 conductor. 13-19. CP 59-930 00 boll torque-load relationships. Data.Jffi cables. fig. 2·1 structural. chemical compo sitton limits (maximum) lor wrought aluminum. 10·7B. :. 9-26 for pipe-type and directly buried cables. 80 std.3-1 AAAC. 4-1. electrical properties. estimating. Class M and A S'lrandings. 3·4 aluminum condUCior steel-reinforced. structural. 1350. tesis1ance. 17-2 vs. bus bars carrying a·c at 60 Hz. two-conductor concen tric-neutral. 10-7C Insulated conductors. ohysica: and electrical propert-oes. (AW). heaHreatable . &4 Alcoa Aluminum Overhead Conductor Engineering Data Book. abOVe 600 vollS.t. 3-1 all-aluminum connection. 1-5. 2-1 aeolian vibration. 1-1 aluminum clad stool conductors. table SA-S derating factors NEC more 1ttan lhree conductors. 3-7 annular rings. 4-2 1350 alurnil'lum wires. -. 3-4 aluminum (den 1·4 aluminum alloy (det). table 4-25 aiuminJm conductor connections.. 3-an Paper CP 58-1072 on corrosion. welded. 6-1.-U1 concenlnc-Jay stranded bare conductors. 3-3 aluminum conductors (~350-H19) stranded with alumr num clad steel (AWAC) conductors. 8-1 ac ~rotysis corrosion. 3-3. table 4-14 modifications. 9-13 !l'lterpolatlon chart tor ducl bank cables. 11-1 aluminum conduit. loW voltage. multiPlying lactor for various conditions of. insulated cables. table 9A·4 derating ractors. 34 composite conductors.reinforced.3. ohysical and electrical properties. 13-2. 9-6 AGAR. 13-46 aluminum. table 4-15 electrical resistance at aluminum wires in. 1957 on temperature rise and load of cable systems. 9-25 effect of temperature. physical properties ct. table 4-23 strength. 3·~ 6201·T81 strande<:t ACSR diameters. 7·3 preassembled. 3-1. tabies 4-12. 1350-1-119.. copper. 1·4 alloy-number. 13-52 C119. 3-9 $kin effect in. 3-4 wittl6201-T81 core. 76. 6-13 altitude. caustic.. 4-2 ACSAfAW. 4-21. table 3013 electrical properties Of mulh-layer sizas. 13-64. taOie 3-3 rated strength. table 3-48 IYPlcal stranding arrangements. 4145. lable 11·10 reverse twist. 4-20. table 9A-6 design constants.-reinforced Slranding arrangements. table 4-13 abrasion resistance. fig. 13-1 altoy 6201. uniform thickness. 9-26 ASTM.7-4 installation ease. 17-6 anodic oxide film. 1~1 ambienl temperature. lJ. 13·1 to. table 17-7 altoy listing. 6-13. tensile and yield strength.rrent busses.17-4 table 18-3 aUoy 6Of53. fl9. fig. 58-4'. 16·11 altoy 6iOl-Te. 3-4 s'. and C core and aluminized A cote. 1$-8 alloy 60$3. table 3-4A expanded. alUminum conductors. 13-1. 2-1 for induction motor rotors. 3·3 curren! ratings.2 1350-H12. 1-1 alumine. 3-23. calculation 01 3-8 acidc ratios. ohysical and electrical properties. physical and electrical properties. 3-1 aU-aluminum conductors. fig. time-temperature percent Slrength. 1-4. 13·11 annealed copper standard.13-3 Aluminum Build/ng Wi~ InstallatkJn ManUal. unequal spacing.18-10 ALS type thtee-condl. methOd 01. 60 cyde. i-i. 13-12 Transactions. 16-2 alloying. 14·2. 3-4 physical and electrical properties. table 9A·3 derating facttn on troughs. index ANS! ioontinued) H35.1-197S. 1~S net stress area, 13·2 wiring, 10-4 appearance, station structure, 18-9 appliance cable. 10-2 arc length, 5-1 apartment·ho~ arc resist3nce. S-1 arc welding, shielded inert, 14-10 arc-current bwmdown. 6-1, &-2 times, table &1 arCing, 6-2 arcing bumdown, 6-2 arcing effects, &2 .a:rmor, round-wire, 7-5 armor rods, 5-21, 5-25, &15 installation, fig. 5-2{I preformed, 5-27 armor wire, flat, 5-21 armored cable, 7oJ inter1ocked, 7-5 arraogemenl of lO$Uleling layers. $-1 MA, C37-20. 13-12 asbestos insulations, 6-5. 14~5 ASTM, 4-3, 7·2 ASTM A 325, 13-45 ASTM A 354, 13-45 ASTM B ,231, 3-2, 7·1 A8Th! B 232, 34 ASm B 238,13·2,13-3 ASTM B 241, 13-2, 13-8, 13-9 ASTM 317,13·2.13-3 a ASTM B 429,13-2.1;)..9 ASTM B 524, 3-4, 3-7 ASTM OOt1OSioo tes1ing, 17·5 Specifications. 4-2 Standards, strength ratings. &-1 audio tone lau!t locating. 12-7 AWG,3·1 AWG-size wire, cross-sections of solid round, 3-1 B B ctass of stranded conductors, 3·2 e&S gage, 3-1 Baltimore Gas &: Electric Co., 8-9 bM:'l aluminum condlctors ampacity of, 3,.19 composite deSigns of, 4-1 homogenoous designs of, +-1 prOOuct classification. 4-1 service classification, 4-1 titles and num::mrs of ASiM specifications, table 4-4 bauxite, 1-1 Bayer process, 1·; BelleWle spring washer, 5-25, l' ·5,11-$, 13-43, 13-44, tabie 11-4, fig. 11-5 bending. 2-3. jig. 13·4 bending properties, bus condUctor mechanical, 13-7, 13-8 bending radii, bus, tables 13-5,13-6 bend'ing rigid conduit, 17·7 bibliography, bus conductor, 13--6$ thru 13-70 bifilar winding, 14·7 bi-metallic pads itt lIal-pad connections, 13·41 binderS,8-12 OObbins, 14-3 bolt clamp connections for bus bars, 13-45 bolt creep factors, 13--6. table 13-7 joint design, 13-40 spacing, 13-41 stresses, 1345 !OtQUe vs. clamping load, 1343 torque clamping forces. fig. 13-20 ii bolted bus COfIMOOOns, 13-40 to 13-45 bolted damo conne<:ter, S~23 clamp bolt connections, fig. 5·21 su~ preparation lor, 13-41 bolted connections, 11-3 bolting. station structures~ 1&10 bolts, 2024-T4, 2·2, 13-43 bolls, heavy serles, torque and stresses in, table 13-45 Bond, N.T" 1341 braided cOWflngs, 8-2 braling, 13-47 "breakdown" furnace, 16-3 bridge-loop methods, 12·7 btituenfiS, 8-1 brnru:e alloys, 2-3 Brown & Sharpe gage, 3-1 Brown, J, R, 3- i building wire, 7·2, 10-4, 11-1 Building Wire installation MafluaJ, Aluminum, t04, "bunched" S1rand~ conduclots, 3--2 "bundled" conductor, 3--3, 3-12 capaci:live reactance ot 3--19 inductive reactance of, 3~19 spaceffl and dampers for. 6-15 Bunet 14·7 burial deolt! 01 caole-, iH2 buried cable ampacity interpolatkin chart, 9-27 outied cables, arrangements 01, for ampaclty calculations. fig, 9A-2 bUrndown are-current, 6·1. 6-2 arcing, 6-2 fault-current,6-1 limes, arc-current, Iable 6·1 "bUm-off~ chaf'actenstics, 2-4 burring, 154 1'-' ",s alternating CUJTent, low voltage, 13-27 Channel, 13-11 connections. oofied, 13-40 thru 13-45 oonneclOrs, expansion. fig. 13-35 design, 13-11,13-40,13-41 expansion joints, 13-34 flal, 13-9 gas-insulated, 13-48 generator, 13·47 high-current, swit'lgillg suspension for, lig. 13-15 installations, 1:.l-47 mtegral web Channel, 13-9 interlaced and paire-d phase, 8ITangemenls oi, 13-16 isolated phase. 13-24,13·50, fig. 13-23 mechanical design, 13·28 norrsegregated three phase. 1347, fig. 13-22 pair~. arrangement of, fig. 13·9 rectangular, 13-$ resonant frequencies, jig. 13~14 rigid, 13·34 round rod, 13-11 round lubular, 13-9 segregated, 13-47 shape selection, 13--8 shapes, 'tYpical, lig. 13--5 special shapes, 13--11 square tubular, 13-9 station, 13"';7 supports, 13·34 switchyard, 13-48, fig- 1.3-25 tubular, 13-9 tubular, expansion support for, fig. 13·16 unilorm thickness angle, 13-11 bus assemblies, inter;aced. 13·16 bus assembly lor heavy short ctrcuil conditions, 13-34 bus bar arrangement, 13-21 currenl ratings, table 13--26 for electrOlytic SUpply, fig, 13-29 bOlted olamp connactions. 13·45 bus bar (continued) clearances, 13-34, tables 13·18, 13-t9 effeets of healing, 13·5 housing, 13-50. 13-51 mechanical prooerties, 13-5 spacing, 13-34, lanle 13-17 bus bars bolted, intertace compressive stress, 13-40, 13-41 extruded,1-1 heating due to magnetlo materiais. 13-17 in parallel, fig. 13-19 square-comer, physical and electrical properties, table 1J..25 transposition, 13-17 bus conductor absorptivity, 13·21 alleys, temperalufe coellic:enls of resistance- tor, table 13-3 ampaci1y, 13-12 corona. 13·19 corrOSion, 13-8 effect of painting, 13-21 electrical properties, table 13·2 emissivlty,13-2! formability reqUirements, 13-7 heat balance equation, 13-21 heat loss equations, table 13-8 mechanical properties, table 13-1 mutual healing, 13-17 proximity ef~t, 13-17 radio influence voltage. 13-19 reactance, 13-17 selection. 13-8 shapes. .3-8, 13-9, 13-11, fg, 13-5 short circuit forces on, 13-24 thtu 13-2a Skin effect, 13-12, figs, 13--S. 13-7, 13·8 vibration, 13-28 electromagnetic, 13·27, 13-28 aeoli,an, 13--33 bus COnductor. 13--5 bibliography, 13-68 Ihru 13--70 deflection and stress forrrrulas, table 13-12 enclosed, 13-23 imegraleweb channel, physical and electrical proper lies, table 13-32 internal damping of tubular, 13-33, tabl& 13--16 parallel. lateral short circuit forces in, ;3-24 thru 13-27 PfO~rties. table 13-32 rouoo..futie:, physical and electriCal properties, table 13-28 short circuit currents, 13-27 longitudinal forces, 13-27 torsional forces, 13-27 heating, 13-27 Span length, vibration free, table 13-15 sqUate-lube, physical aod electrical properties, lable 13~29 temperature rise, lJ..11 effect 01 conductivity, 13-11 elleel of Oimensions, 13-12 uniform thiCkness aluminum Channel, physical and electrical prop&r!ies, table 13-30 uniform-thickness angle, Ohysical and electrical prop erties. lable 13-31 'bUs duct," 13-48 bus expansion, 13·33 joints. 13-33, 13·34 joints positioning, 13-34 rectangular, 13-33 sltuc!vfal shap&, 13·33 tubular, 13-33 bus swing, 13-34 _.s fer aluminum industry, 13-52 for chlof-alkali industry, 13-52 for electric furnaces. 13-52 index busses (continued) tor magnesium indUstry, 13-52 bus.ways, 13-48 feeder, cross section, 13~16 plUg-in. fl9. 13-28 butt weld, 13-46, lig. 13·21 butyl synthetiC rubber, a-s c C class of stranded conductors. 3-2 cable a-cid~ ratios, !J..6 aluminum sheathed, 74 a~o~,3-~Ud~,~1 burial deplt\, 11~12 covered aluminum, 7-2 deslgrI, 9-1 diame1er. 9-1 determination ot, laDle 9·1 outside, and conductor diameter compared, lable 1>2 economic study of, !}.6 laflure, external causes, 12-5 in aluminum conduit. 9-6 installation, d!.lct, fig, 1H'!1 pulling in conduit, 17·7 maintenance inspection, 12-4 mechanical damage to, 12005 selection, eoonornics of, 9~21 spa~9·2 stranding, methods oj, 119. 8-2 supports, rigid, reaclance of conductors on. 9-10 underground instaila1ion. insUlated, (600 v), 7-4 cabIe-conductor resistance, 9-3 CalcUlarkm orrhe Temperature A/seand Load Capability of caOle systems. The, 9-13 -""" across conductor insulation, nomogram, 9-14 insulated aerial cables, 8-14 insulated conductors directly buried, 8-1 B with grounded sheath, 8-1 B capaci1ive and inductive reactance, 3-12 capacmve reacta.nce, 8-14, 9-9 bundled conductors, 3-19 busbar,13·r~ separation component of, al60 Hl megohm-miles per conductor, table 3-12 capacitor design, 15~1 electrolytiC, 15..4 equivalent electrical circuit, fig. 1&-2 equivalent network of a, 15-1 lJteting, 15-4 lo.sseS, 1S.2 paper, heat loss ¥s. frequency, fig. 15-5 impedence \is. frequency, fig. 15·2 waxed paper, 1$·4 wound paper, 15-3 Carnegie Steel Co., PQckfNCompanlon, 13-63n cast allOy lOr bus 1050, 13-2 cast iron crucibles, 16·3 casl rotors, oomparaUve performance, 16-1 casting. 1-4 methods. aluminum rotors, 16·3 problems, 16-4 temperalUre, rotor, 16-4 them'lallreatmen! Of rolor, 16-4 catalog information and technical data, 4-2 catenary constants for horizontal spans. lable 5-4 <:atenary CUM! and preliminary sag-tenslon graph, 5·10 chanrwl Plugging, furnace, 16-3 chemical composi1JQn limits (maXimum) for wrought alu minum alloys for eleclrical oonductors in percent. table '·2 chemical factOfS In selecting cable co.;erlng, &'1 inSIJlatiof), 6·i charging current, a.1, a.13 chloride. in concrete, 17-6 oolOl1ne, 7-4 chloro-suiphonic acid, Chronlum, 2·2 cireuil breaker, 6-1 circuli vOltage drop, rigid oonduit, 17·4 circuits, diagrams and fonnulas of electrical and power quantity relationships, fig. 12·1 city-distribution lines. 5-23 damp·boltconnoctors, fig. 5-24, 11~1 mechanical compression, 11-5 Clamps, dead-end, 5-23 $USP8l'iSion, 5-23, fig. S·2Q Class A bare oonoentr1c-lay stranded conductors, 3·2 Class AA bare oonoentric·lay stranded conductors, 3·2 Class B stranded oondUCIors, 3-2 Class C stranded conductors, :3-2 Class 0 stranded conductors, 3-2 clearance between live parts or bare conductors in alr, table 13·17,13-18 clearances, ln oo1door substations, tabfe 13-19 clevls support at pole, fig, 11·31 coated strip, 14-5 code word, 4-1 Code Words for Aluminum Efectricai ConduetolS, 4-1 a-9 con characteristics, 14-7 connections, 14-4 design, 14--2 oornputaoon chart, 14-8 strip magnet conduClor, 14-6 sile, 14-3 slrip wound, useful formulae, table 14-11 wound with aluminum and copper. space comparison, fig_ 14-6 coJdWeiding aluminum strips, 14-9 cold working. 1-4, 2"1 cold-beOd characteristics Of tat bus bars, table , 3-8 compact concenlric stranded conductor, fig. 3-3 compaC1l stranding, 7·1 compacting 01 stranded conductors, 8--2 composite conductors, 3-3 sag-tension graphs for, &18 composite towers. 18-8 composition, rigid conduit, 17-2 oompressed stranding, 7-1 compreSSiOn connector fittings, fig, "~2 compression conneClors, 5-21. 11-4 tubular, fiS, &19 compression joints, 5-21 t\lbular, Ilg, 5-~a compression terminals tor magnet wire, fig, 14-2 compressive stress, 13--41, 13-43 ooocentrIc-flat·ribbon neutral, fig. 10-9b ooncentfic..1ay conductors, examPleS o( fig, 3-2 concentriC-lay stranding, 3-2 concrete, embedding rigid condwt in, 17-(1 conductivity, 2·1, 2-2 bus conductor, table 13-2 of high-purity metals tor eteetrical oonduC1ors, c0m parative, table 2~1 thermal, 2-1. 2-3 conductor cable ampacity, table 1G-1 oondUCIor croSSwsectional areas, table 17,.,a conductor metal, physical and electrical constants, table 4-2 conductor shields, 8-10 conductors bare uninsulated, 3-1 ""bundled," 3-3, 3-12 capacitive reactance 01, 3-19 inductive reactanC& of, 3·16 building wire dimenSions, table 11·1 ron;posi1e, a-3 constructions, special. 3-3 designation, 4-2 dIameter andCabie outside diameter compared, lable 9·2 "exoanded" core concentric-lay, 3-3 insutated, 2-3, 7·' in vertical raceways. , 1-1 a Shapes, cross-sections Of, special, 3-3 spacing, H stranded,a-1 stranded and solid. differences between. ~2 symbols tor type$ Of, 3-1 conduit (del.), &1 alloy composition, !able 17-7 alumlnum VS. steel, dimensiOns and comparative wetgi:1ts, table 17-6 cables in. H installing, 1HJ. fig. 11-20 staggering ends of, fig. 11-2{) circuit voltage drop, 17-4 concrete, embedded in, 17-6 corrosion characteristics, 17-4 design, 17-1 electrolytic attack. exposure to, 17-6 expansion joints, 17·7 fault protection capability, 17-3 fill area. 17·1, taple 17·1 fittings, 17-7 galvanic attack, exposure to, 17-6 industrial applications, 17--6 installation, 9'1, 17~1, 17-(1 labor, aluminum vs. steei, 17·2 max no. Of compact conductcrs in conduit or tuPing, table 17~2 numbet' of conductors allowable in different sizes of, table 17-4 resistance, 17--3 short·circuit capability, 17·4 si:/:e,17·7 connecting procedures, 11·1, 11-3 to 11·7 OOf\OeCung Single-conductor, secondary wires and cables, 11-1, n-3 to 11·7 connection aluminum-ti;M)Opper, 5"25, fig" 5-23 boiled, surtaoo preparations for, 1&41 bus conduClor, 13-36 copper~afuminum, 13-15 expansion, bus, fig. 13-$5 making, 11~7 welded aluminum"to-alumlnum. 13-46 connections, typical 5-15 kV. fig. 11·28 connectors:, 5-21 bolted clamp, 5·23 buHding wlre, i 1-2 Clamp-bolt. fig. 5·24 compression, 11-2, fig. 11-1 jumPer,5-21 rnecimnical, 11-3, fig. 11-1 plating, '1·3 splice kit, fig, 11-23 constants, physical and electrical, conductor meta!, lable 4-2 oonstric1iOn resistance, 13-37. fig. i 3-17 constmctions. power cable, NEe deStgMtions fur, 8-12 rope-lay, 3·3 special conductor, 3-3 consumable electrode, 13-46 continuous casting, 1-4 contact interface, nature of, ~3--36 contact resistance, 13-40, fig. 13-18 contact surface area, 13-40 control wiling. 6-0 convection heat loss, J.19. 3-20 copper, 2~2, 2-3, 5-21,5-2$, 10-9 copper bus bar, temperature coefficients of resistance for bus conductor alloys and representative values for iii index copper bus. bar (continued) commercial, table 1~3 copper conductors, 7-S hard drawn, 3-3 copper magnet wire, 14-1 copper standard, if'ltel'national annealed, 3-7 copper lIS. aluminum: comparative cross.section for equal VOlume conductance. labIa 14-3 copper-aluminum ~s,I3-45 cores, wound, 14-2 oorona. 3-12, 13-19 insulation, eHect on, 8-10 shielding, effect on, 8-10 "corona laver test, &12 corrosion a-celectrolysis,17..J atmospheric, of solid metals over 10 years, table 17·7 galvaniC, 13-45, 13·46 reduC1ioo of, 3-4 reststance" 2-1, 2-3 station structures, 18·10 transmission tower, 18-$ covered condl,lC1or (det), 7·1 covered wires or cables, conduCtors for use with, 7·1 Davy, Sir Humphrey, H dc resistance calculation of, 3~7 change wl1h temperature, 3·8 temperature coeffiCients, table 13-3 dc reSistivity values lor aluminUm wire alloys at 20"C, table S.s dead....nd, 5-21, 5-23 dellis, fig. 5-26 pretormed, 5·24, fig. 5-26 steel eye, fig, 5·26 tubular compression, fig. 5-4 dead-end a1 pole, '19" 11-30 dead-end clamps, 5-21, 5-23 dead-end support at pole" fig. 11-31 dead-enctrg cables, messengers, guy wires on poles, 1i9. 11~30 Dearborn Chemica! Co., 13-44n deflection and stress formulas, bus conductorS, table 13-12 detloClion values Scheel. 40 pipe, table 13-13 Sched. 60 pipe, table 13-14 Delta TO values. 9-23 deSign 01 cables, 9-1 cutting rigid oonduit 17·6 of conduit, 17-' sta1iOn structural. 18-8 transmission towers, 18-4 designations of conductors, 4-2 of insulators and coverings, NEC. 8-12 of power cable constructions, 8-13 QelJllle, Henri Sainte..Qall'e, t·1 die-cast rotor, open-slot, fitt 16-3 die-cast rotors, 16-3 dielectric advantages, strip magnet conductor, 14-9 dielectric computation. 8-16 dielectric oonstant. 8--1, 6-14 under 8<t condilions, 8-14 dielectric loss, U temperature rise, 9-23 dielectric stress, 8-9 dielectric theory, 8-1310 &16 dimensions of heavy-S(tIie:S alurnin:lm bolts, national coarse ltireads, table 13-21 direcl current busses, 13-27 direct potential, 8-14 dlreC1-burlal cables. 10-8, 10-15, 11-12 direction ¢f lay, 7-1 displacement currem, 8·13 dissimilar rMtal interfaces, 13-41 drawing the parabola, method of, 5-11 drawn aluminum round wires fur use in electrical c0n dUctor cables, table ,., dross delect, rotors. 16-4 dry foil, 15-6 duct bank cables, ampacity intarpolatlon chart. 9·26 dUcts (de!.), 9·1 installing, 9-1 installing cable in, 11·10, fig, 11-21 staggering caole ends in, fig. 11~2O dynamiC balanGing, 14-2 dynamometer, 5-7 o E D dass of stranded conductors, 3·2 damper cable, 6·16 damper spaolng, fig, 6-8, 6-9 dampers fOf bundled conductors. 6·15 festoon, 6-14 Srockbridge, 6-14, lig. 6-7 vibratiOn,6-14 dancing. fH3 earth thermal resIStivity, 9-23 economic study of cables, 9-6 economics aluminum magMl wire, 14-1, 14·2 bus coooUClor, 13-1 Of cable seiection, 9-21 Of capacitor design, 15·1 eddy-currentloss. 3-10,9-1. 9-3, 9-6, 17-1 hystersis and, 3-10 CO'.'erings availability. 8-1 braided, 8-2 selection: chemical. electrical, moohaoical, thermal factors, a-1 for \.Ininsulaled conductors, 8-2 companSOn of, table S-1 covering temperature, a-12 in rotors, 16-4 creep, 2-1,2-3, 13-5. 13..J6, 13-40 rate,6-11 CfacKs Short-time, 2·3 creep factors. bus conductor, 13-6, table 13-4 cross arms, 18·3 oross.\inked polyethylene Insulation, 8·5, table 8-4 orosswind damage, 6-13 orucible furnaces, 16-2 crushing resistance, insulatiOn, B-1 cryolite, molten, 1·1 Current-Catrying Capaolly of ACSR, H.e. House & P.O. Tuttle,3-8n curenl, charging, 8-13 curren!, displacement, 8-13 curren!, leakage-conduction, 8-13 ourrent in shealtl beiore insulation damage, computing, 12-2 current ovetfoad, 6-10 current per unil area of contact interlace, 13·41 curranl ratings for ACSR table 3·21 for bus bar arrangements, table 13·26 current values, 6-1 current·temperatuTMise graph for ampacity, 3-22, 3-23, 3·24,3·25 current 'IS. temperature rise, 13·22 currents in an insuialOl', vectorial relationship of, lif,,,, 8-15 iv Edison ElectriC Institute, 6-9, 11-23 effective resistance of loll electrodes, 15-3 EHV lines, 3-3 design,3-12n expanded core designs for, 4-1 elastic limit. 13-7 EJectric Equipment, General PrincipJes for Temperature limits it'! the Rating Of, IEEE Pub., 14·2 eleclric furnace. 9·9 busses, 13·52 electric method, Insulation. water absorPtion, s..12 electric wave filters, 15-2 electric-are welding, 13-46 electrical and phySical oonstants, conductor metal, table 4.;1 eleC1tlcal and mechanical properties 01 all-aluminum 1350-H19 compacHound stranded condUCiors, table 4-9 solid-round 13S0·H19 aluminum wires, table 4·4 metrical and physical properties AAAC, 6201-1"81 stranded. ACSR diameters. table 4-12 in even AWG and kemil diamelers, table 4-13 ACSR compacl-round, lable 4-18 ACSR'AW, table 4·17 ACSRiTW, table 4-19,4-20,4·21.4-22 aa..aluminum 't350-HI9 Class AA and A stranded oonductOrs Of even kcm'! sims, tabk.! 4·7 aluminum oonductors, 1350-H19, stranded wth alu minum clad steel (AW) conductors_ tables 4-37,4-36 integral-web channel bUs conduClOrs, table 13·62 pipe-size conductors, standard, table i3·S7 >OlJnd-tube bus OC>I1ductors, table 13-58 square aluminum tubular conductors, table 13-59 square-comer bus bars, tables 13-53, 1$-54 un'iorrn-thic\<ness aluminum channel bus conductors, table 13-00 uniform-took.r!Oss angle bus conductors, labia 13-61 electrical characteristics of aluminum conduit va steel, 17-3 of ro1or metal, 16-2 electrical circuit 01 a capacitOr, equivalent, fig. 15-1 eleC1rical conductors, aluminum and aluminum alloys tor, 1·4 eleC1ncalfactors in selecting cable coverings, 8-1 insulation, 9- i electrica< properties ot bus conductors, 13..3 eleC1rical resistance Of aluminum 'f',l$S in ACSF table 3-4A eleC1rode, consumable, ~3-46 e!ectroIyt'c al1ack on rigid condUit. 17-6 electrolytic capacitor deSign, fig. 15-4 electrolytic capacitOl's. 15-4 electrolytiC supply bus bar arrangement, fig. 13-29 electromagnetic coil, 14-1 etectromagnetlCtorces, 14·13 on bus conductors. 13-24, 13·25, iabies 13-10,13-11 fault...:tJrrent, &-9 elongation and tensile strength, alUminum conductor aJloy data, table 4-3 elOngation ot insulation, 8-4 emergency loading, 6-10 emergency overload ratings, 9-16 emergency overloads. 12·1 emissivity. radiation, table 13·9 emissivity, sun, altitude, multiplying taC10r lor various conditions of, ftg_ 3·15 emissivity, limllatiofis, 3-21 EMT benders, 17·7 energy loss. 9-3, 13-12 EPOM. 8-5. 1{)'5 EPM, 8--5, 10-S EPR 8-5 EPRf TransmiSSion Line Aeferen<;e Book, 3-12 ethylene-prOpylene copolymer. 8·5 ethylene-propylene insulating material, 8 ..5 index ethylene-proPlf1ene rubber, 8-2, 6-5 ethylene-propylene terpolymer. 8-5 exothermic welding, 13-47 'expanded" core concentric-lay conductor, 3·3 expanded core designs lor EHV, 4-1 expansion connecrors. bus, jig. 13-16 expansion joints for rigid conduit, 17-7 "extended foil." 1S.S extruded aluminum, 18-10 extruded aluminum structural shaoos, fig. 18-12 extruding, ;·1 e:.o:lrusion C1esign capability, transmissiOn toWers, 1a-S F F (Iemper designation). 1-6 fabrication of aluminum, fig. 1·2 sequence 01 operations. 1-4 stati()(l structure. 18-9 factor K, shape couectiOn, fig. 13-12 foil (continued) per, table 15-2 alloy thickness and width limitations, table 1&3 chemical composition of alloys used. table 15-1 roll si:ze. weight table 1&6 slick, 15-5 splICe data, table 15-5 yield limitations, table 15-7 fOld-Out parent metal Stfip conductor lead, 14-10 formab!lity, bus conductor, 13-7 foundations for Transmission ~!'S, 18-5 rree4Oop1~,ErI4 frequencies, resonant rectAngular bus. fig. 1$-14 fretting, £·14 fric1ion, inlerstrand, $-14 fumaces "bl"eakClOwn." :6-3 channel plugging, 1$,3 eqU1(XTlent for rOlor manu1acture, 1S.2 induction, 16-$ reverberatory, 1&3 fuse, 6-1 laslening methods, $lation structures, 18-'10 heat balat'IW, equation. 1&-21 heat effects of short-circuit currents.. 6-9 heat loss, 15-2 lota(,9-6 equalion, indoor bus, table 13-20 heat-sink eflec1, 9-24. 12-1 heat treatment, 2-1 heat ttansfer characteristics of strip conductor. fig. 14-10 helicoptef1ll and aluminum towers, 18-8, fig, 18-8 Herault. Paul L, l-'l H-trame lowers. 18-7, fig. 1s..8 Ngr,..voltage cable, ampacitj of. 10-16 hlgh-vctlage substalions, 13-27, 13-48 hollow-ingot process, i~ hori:rontal cold chamber die-casting, 16·3 House. HE, 3·8 housing for bus bars, 13-52 HV lines, 3-3 Hypalon. 8-9 hysteresis, 3-10. n-1 and eddy current effeds, 3<0 lOsS, 3-10, 9-1, 9-3, 11-16. 17-6 iatigue of conductor strands, &-14 of overhead conductors, 6· t 1 1aligue resislanoo, 2-1 fault conditions. 3-16 impedance under, g..13 fault-cUrrent adjustment factors. table &.2 blJlT'ldown, 6-1 in aoonduit. 17~3, 17·5 e1ectfomagnetic torces between parallel bare wires and cables, 6-9 in sheath, 12~ in Shield, 12·3 fault-curren! limit, 6-1 maximum lor bare stranded ACSR aluminum conduc tot, figs, 6-6 to £-8 maximum lor stranded aluminum conductor, f.gs, 6-1, 6-2 faull-current wave, 6-9 fault locatiOn, 12-6 fault-tune adjustment factors, table 6-2 faultS transmission line, 6·S underground, 2·4 feeder bUsways, 13-4$, fig 13~27 FEP, &5 festoon damper, 6·14 liU area, 17·1, table 17·1 flUers, 8-12 fUm-insulated round wire, 14·1 firm resistance, 13-40 1~ms, anodized, 14-4 filtering capacitor, 15-4 1ish Hne, for cable installation, 1HO fishing thrOUgh conduit, 17-7 fittings, o... erhead conductor, 5-21 fittings for rigid conckJit, 17-7 fiat armor wire, 5-21 flash welding. 1347 flashOver, 6-2 flat bus, 13·9 flat bus bars, cold·bend characteristics, table 13-5 flat washers, ou1slde diametet and thickness, table 13-23 flexibility, ifl$uiation, 8-1 fluorinaled ethylene propylene rubber, 6-S fluxing, 16-3 foU anodized. 15-6 dry, 15-6 electrodes, effective resistance of, 15-3 production, alloy physiCal propert~ temper, table, 15-2 G Gaertner, G.H" 6-9 gallOping, 6- i 3 galyanic attack on rigid conduit. 1 N): galvanic cotrOsIOt'I, 1346 galvanized inner-eore wires of ACSA, 3-4 garnets, 1-1 gas hOles, 1$-.4 gas welding, 13-26 General Electric Company Data Book, 9-9 General PrincipleS tor Temperature Limits in the rating 01 Electric Equipment. IEEE Pub., 14-2 generator bus, 13-47 geotl'letric mean distance, 3-13 valuesoi, table 3-15 geomel:ric mean radius, Xa and, 3·14 glass, 14.-5 GMAW welding, 13-46, 1&-10 GMD, S-13, 13-17 values 01. tables 3-10,13-7 GMR 01 annular rings, fig. 3-10 ~ and, 3-14 Godde, W.B" 6-9 Government Ru~r.styrene. 8--4 graphile, aqueous, 16-4 gravimelric methOd, insulation Walef absorptiOn, 8-12 GRS, 8-4 GTAW welding, 13-46, HHO Guide for Design of SubSlation Rigid-&Js Stru=tures. IEEE, 13-11, 13-27, 13-26 guyed "Delta" to'Ner, 16-4 guyed "Delta" transmission line tower, lig. 18-4 guyed "Gull Wing" transmission line tower, fig, i8-5 guyed three-DOle transmissioflline tower, f'9- 18-6 guyed "V" transm:sSloflline tower, fig. 18-4 guyed "Y" transmission line tower, jig. 18-2 H H (lemper deslgna11on), 1-6 H1 {temper designation), 1-6 H111 (te:mperdes.ignation), 1-6 H112 (temper designatiOn), 1-6 H2 (temper designation), 1-6 Hall, Charles Martin, 1-1 Han process, 1-1 Harvey, J,A" 6-11 Hazan, Earl, 3-S heat batance, 3-19 12R losses, bus, 13-12 lACS, 3-7 ice load, 3-3 ice-<:oatirtg, s., 3 ICEA, 7-5. 8-5 ampacily ratings. 9-13 ampa~ly, report 00 cable, 9-6 installation practices, 11 -1 pertormaru:e specificatlons, &12 Pub, No, P45-482, 12-3 Mtw26, .... U, '962, 9-4, 9-6, 9-21, 10-18. 10-22 Resistances. Table 9-3 8·61·402, Table 4. 10-1, 10-12, 10-14 8-66-524,10-1 P-53-426,10-18o shield specifications. 8-10 Standards: for emergency-lOad and short-circuit load temperalLlfe$ for insulalion. table 9-7 ICEA-AlEE ampacity tables llA·1 lCEA·IEEE ampacily tables. explanation. 9·22 to 9-29 IC£A..NEMA Publication S-19-81wWC-3. a-1<, 9-16 Standards, spectflcarions lor thermoplaS!ic ifl$UialiOns, table 8-3 identification of product. 4--1 IEEE IEEE GlJide for Caiculating LO$5e$ in Isolated Phase Bus, 13-24 IEEE Guide for Design of Substation Rlgid~8us Struc tures, 13-11, 13-27, 1&-28 IEEE Paper 64-146, i.Jmitations On Stringing and Sagging Conductors, 5·10 IEEE publicaiion P-524, Guide to the Instalfarion of Overhead Transmission Conductors, 5·7 Special TechniCal Conference on Underground Dit>~ tribution, 11-11 TP 674 PWA, 6-11 Transaction PaperT-72·131-S. 13-38 Paper6(H80.13-12 Pub. No. S~135, 9-21 Stds. pUb. No, 1, April 1969,14-2 Standard No. Zl, 13-12 Tran!factfon an Power Apparatus and Systems, $-141'1 .mpedance, 15-1 reduction Of, by adding terminals, fig, 15-3 under fault condilioos. 3-1 S zero-sequence, 3-16 improvement 01 phySlcal properties. treatment for, 1-4 impu!:se!i:Nl<Ieclor melhod, 12-7 impulse generator. 12-7 v index inductance, 15-1 of strip magnet conductor colis, ,4·7 indUCtiOn fumaces, 1a-3 induction motor rolOrs. alloys for, table 16-1 insulation (continued) tapering, fig. 11-16 temperaltJres, &12 indudive reactance. 3·12, 9-8 thermal characteristics, 14-2 thickness, delermining, 10·11 for high-voltage conductorS in three-phase systems, table 10·4 of secondary cables for direct burial or underground in duct, table 10·3 01 secondary cables lor power and Ifghting, table 10·2 unshielded cable, 10.12 insulator pin-type, 5-23 Of bundled conductors, 3-16 bus bar, 1~17 and capaCItive reactance, 3-12 to neutral 2, 3, 4 single conductor in same oonduit, table 9-5 separaifon component, at 60 Hz ohms!conductor/mile. table 3-9 series, 9-2, 9-8 spacing factors, table 13-7 and zero-sequence resistance, 3-16, table 3-11 industrial applications 01 rigid conduit, 17-5 industry code word, 4·1 inert-gas shielded welding, 1:H6 ingolS, production 01,1·1 inhibitor joint compound, 2-3, 11-1, 13-4! ini1ial and iinal sag--1enSior\ charts: for variable--Jength spans, 5--2 in.i1isl stringing chart, 5-4 iollia! stringing sag Chart, 5--4 installation of cables aerial insUlated, 11-23, table 11-10 cables in trays, 11·9 in condu!! Of cruet. ; 1-8 directlY bulied, 11-10 dead ending secondary cables, fig. 11·30 secondary triplex., neutral-messenger-suppol1ed, fig. 11-31 techniques, 11-7 installation of conduit 9-1, 17-6 instailatlon of duct, 9-1 practices ins, cable, 11-1 instaJ;ation proof-tesling, 12-5 insulated cables conductOrs tor, 8-2 short-circuit currents lOr, figs. 9-18 to 9-20 insulated conductors (de!.), 7·1 0-000 volts, 7-2 above 600 volts, 7-4 ampacity of, 9-13 series inductanCe reactance nomogram, 9-10 for special conditions, 7-5 insulated wires or cables, conductors for use with, 7·1 insulating materials, 8-2 selediOn of, B-1 thermoserting, 8·4 insulation atrangement of layerS, S- asbeSlos, 14-5 !)reakdown. causes, 124 cable, portable 1D-9 cleaning, 11-7 compatibility with, 2-1, 2..a damage. maximum CUi'tent before, 12..a failure, causes, 12-4 for slop magnet comruCior, 14-4 interleaved, 14-5 level, 10-11 paper, 14-4 performance, &2 performance specifiCations, 8-5 pofyamide, 1~..i polyester, 144 power factor, 8-1. 8-14 Quality,8·4 reSistance, 8-1, 8-12, 8-14 temperature corrections, table 8A~ 1 selection, chemical factors, 8-1 electrical faders, 6-1 mechanical faders, 6-1 thermal factors, 8-1 shielding, 7·4, 8-1, 8·2, 8·10 primary cables (to 46 kV), 10-12 vi leakage-conduction current, 8-13 lengths of conductor, solid vs. stranded, 3·2 Las Sau):., France, 1-1 Lewis. W.A., 3-13n limits,8·4 su;);lOI1 spacing, 13-33. 13-34 unbalanced force at, 5·10 vectorial relationships of curl'el'l1s in an, f:g, 6-A1 integrat-web channel bus, 13-9 electrical and physical properties, table 13--32 interlace compressive stress, 13-36 interlace, contact, nature of, 13W lnterlaces, dissimilar metals. 13-41 interior wiring (branch circuits to 30 amps), 10-7 intertaced bus assemblies. 13-16 lnterlaced bus arrangement, fig. 13-9 interleaved insulation, 14-6 interlocked armored cable, 7-6 international annealed copper standard, a..7 International E:eclro-Technical Commission. 3-7 ionization voids, 8-12 Iron. 1-4, 2-2, 13-1 isolated bus, 13·24 iSOlated-phase bus, 1ig. 13-23, LF, 9~24 lighting cables 600v InSulated, fig. 10-6 600·1000v, 10-5 insulation thicknesses, table 10..6 highway standards, dimensions, lable 16·1 series street. 7-5 standards, 18-1, fig. 1&'1 I.ghtning, ~2 line design tae1Ot'$, 0-1, 6-9 lit"lear expanSlOO, design coefficients of, 2·3 li~ar expansion, thermal, 2-3 lines of force from conductors in grounded sheath. fig, 8-, tacto(, 9-23 load load power lac!O(. 9-9 loading, emergency, 6-10 locomotive reel equipment cable. 7-8 long spans. sag correctlons $0(, 5-7 lOss, energy, bus, 13-12 loss lactof. 9·24 loss 10 a capacitor, 15-2 fOil, 15-$ leads. 15-<3 lubrication of conduit joints, 17·7 01 bus conductor bends, 13-8 ~3·24 M J jacket materials, 8·9 neoprene, 8-9 to protect insulation, 8·2 PVC.8w9 requirements. cables with no, 8·10 specifications, rubber or thermoplastic, !abe 8-5 thickness, 10·11 for single· and multi-conductor power cables, table 10·5 lor single-condUClor 00Nef cables (AWG-l¢mil sizes), lable 10-0 ,ade, 1·1 ;onng aluminum strips, 14-9, 14-10 joining rigkl conduit, 17-7 jointcornpound, "·1, 13,.41 j{lints, 5-21 design, 1340 power, cable 15kV or 25kV, fig. 1,-25 Jumper conMCtor, &21 K Kaiser Aluminum Sus Conductor Technical Manuaf. 1~H Kvar reactive requirements, 3-Sn L laminations, 18·1 stamped, 14·2 steel,16-4 Larson, R.E, 6-11 lateral displacement, 2·4 Lavoisier, Antoine L, 1-1 leaKage reactanoo, 3-12 MCAdams, W,H., $·19 McGrath. M.H.. 9-13 magneSium, 1..4, 2·2 magneSium-silicide 0063-T1 aUoy, 1Nl magnet wire, i compression terminals, f'9, ~ 4-2 mechanical terminalion, 14-4 in motors, 14-3 soldering, 14-4 spliCing _14-4 magnetic effect, 9-6 magnelic hoist cable, 7~ maintenance proal testinQ, 12-5 manganese. 1-5, 2-2 manufacture, rigid conduit, 17-2 manufacturing cast aluminum rotors, 16·2 Martens, C.A , 6-2 Martin, J.S., 5-10 materials for il1$ulaliot'l, 8-2 maximum current in $.">eath before Insulatlon damage, computing, 1M met:haniCal bending properties, bus conductor, 13-8 mechanical clamp-boll conooctor, 1:9. 11-1 mechanical damage to cable, 12~0 mechanical design of conductors, 3·1 mechaniCallactors in selecting cable COvering, 8-1 mechanicallactors in selecting insu.iation, 8·1 mechanical joining 01 strip conductor, 14-10 mechanicallOOd claSSifications, NESC lor ovemead con· dUCtor, tabia 5·1 mechanical properfies, bus conductors, 13-6, lable 13·1 mechanical set-screw cooooctors, 11-3. figs. 11-1, 11·2 mecnantCailerminatlon, magnet wire, 14-4 messenger size of primary cables, 11-23 messenger-supported, servioo-drop and seco'ldary cable (duplex, iriplex and <lUadruplsx), 10-' messenger $t,'SpensiOn clamp at pole, til}, 1~ -31 messengers, 11-23 messengerS, neutral, 10-1 4-' index metal-workil'lg p~sses, aluminum, 1-1 MetalliC Eiectrk:al CondUctors, t.-2 metallic stue#ding, 8-1 Meyer, Kat1 Joseph. 1·1 mhos, 3-7 mica, 14-5, 1&4 mine power cableS, 7 ? minimum training radii, 1HO. table 11·5 !'I'\i!rlimum bending radii, labIe 11-7 moisture ~islance, 8-1 rl1('XQf lead cable. 7-6 motor rotors, M fractional hOrsepower. 16-3, 16-4 induction. alloys f¢I, tabJ& 16·5 Integral hOrsepoW¢(, 16-4 motors, magnet wire in, 1+3 squirrel cage inductloo, 16-1 multi-oonductor cables. corrections for, 9·9, table 9-11 multiple conductor power cables, (0.600 Yolts), 7-3 multlPlYlng fac10r for various conditions ofemrssrvity, sun, altitude, fig, 3-15 multiplying factors tor maximum short-clrcuit lateral force, table S·2 Murray Loop, 12'-7 N National Electrical Code, 6-1 National Electric Safety Code, 5·2, 7 1, 7·,2 M NBS Handbook 109, 3-10 NEe. 6-1. 7~1, 7-2, 7·3, Nh 8-1, 8-4 arnpacity ratings. 9·13 Articles referenced from t~ cOde 220,12-1 230, 12-1 250-21. 17-3 310,10-1,10-18 310-6,10.1S 310-'3,7-1,10-11 310-i6 to 19, 17·1 318-2, 10-8 334,7·2 33&3,10·6 338, ,0·2 364,13-52 430, 12-1 500, expIoslon-orooling, 17-6 710, 10-4 Code rubber insulations, 8-5 designations, insulators and coverings, &12 for power cable construction, 8-12 installation practices, 11.1 requ.irements fOr rigid conduit 17-1 standard for cables in duel, 9-2 types of insulation, 8-4 VOltage drop. 9-12 voltage-droP lirnrtalion, 9-12 negative sag, 5-8 Neher, J.H.. 9-i3 NEMA Puo. No. HU·l, 1973, 13-38 Standards BU-1, 13-52 sa·l·a02. 13-57n SG·I-4.05, 13-45n SG-5,13-52 SG-e, 13-38 neoprene insulation jacketS. 8-2, &-9 synthetic ruboor, 8-5 NESC 5-2. 7-1n burial, cable separa1ion, 11-11 for overhead conductol", mechanical load classlflca lions, table 5-1 neutral l'nGSsengers, 10-1 ,,-23 neu1ral-supported cables, .5eNice-drop cable, 1h23 nickel, 2~2 nilrlle·butadiene/polyvinyl-chloride jackets, 8'10 NM type btaI"Id"t-Wiring cat>les, fig, 10-8 MN type non-melal6c sheathed cable, 10-7 NMC type non-metallic sheathed cable, 10-8 "Nomex," 14--5 flOfH3egregared three..pha$e bus,. 13-47 nylon Jackets, 8-10 o o (1emper deSIgnation), 1-6 Oerstedt, H.C.• 1-1 ohmic loas. 15-2 oil-resistant control cable, 10-10 open-slot die-cast rotor, fig, 16-2 oscillation, 6-13 overhead conduCtOl'S accessories, classillcation, 5--21 fittings, ciassificatiorl, 5-21 National Eiecfric Safety Code for, mect'iaNca! load classifications, tabI~, 5-2 vibration and fatigue. 6-11 ~overtap," oorrtact surface area. 13·40 "overtapp&el toil," ~ 5-3 overload, emergency, 8-10. 12-1 ovel'load conditions, st>?ady-state, 6-1 overioad ratings, emergency, 9-16 oxide 111m, removing, 11~1, 11-7 oxide inhibitOrs, 13-41 oxygen, 1~1 oxygen-sensitive Insulalion. 8-4 ozone, 8-12. 10-13 ozone-resisting butyl rubber, 8-S ozone-reSlsting rubber insulatiOn, 8-5 p paired anglflS, 13-11 paired bus arrangement, f.g. 13·9 paper capacitor Mat loss vs. frequency. fig. i 5-5 If'fIpedance vs, frequency, fig, 15-2 paper insulation, 14-5 parabola. diagram 101' OlotMg OOIrm,; on a fig. 5-9 parabola. methOd 01 drawing the, 5-11 parabola, ternp(ale lor linal sags, fig. 5-5 parabola formula, (;1)mOlelion of stringing graph by use 01,5-6 pa!'a[~1 conductors, 6-9 parasitic losses, 15-2 PE,8-S pencilling tool, fig. 1H6 Pennsylvania Department of Mines, 10-11 performan<::e specifications, ICEA, insulation, 9-4, B·12 phase conductors, insulated aluminum_ 7-4 phase identiflca.fion, a-1 physical and electrical properties 01 AAAC 6201-T131 stranded, ACSA diameters. table 4-12 table for even AWG and kOmi/ diamelern, 4-13 of ACSR compact-round, table 4-18 of ACSRI1W, 1m<$' 4-19 to 4~22 of ACSRlAW, lable 4-27, 4-28, 4-29 of Me 1350-H19 Class AA and Astra~conduetors of even kCmil sizes, table ('-7 of AACrrw, taD!e 4-10, 4-11 of all allJmirom conductors, 1350-1-119, stranded with aluminum clad st~ (AW) conduclOfS, tabte 4-25 of aluminum standard oioo-s1ze conductors, table 13-27 01 Integral-web channel bus conductors, table 13-32 ph~ical and <$'Iectrica! properties (continued) 01 round-tube' buS <:onductors, lable 13-28 of square aluminum tubular conductors, table i3--29 at square-corner bus bars, table 13-25 at unlform·thickness aluminum channel bus conduc tors, table 13-30 of uniform-1hiCkness angle tws oonduc1ors. tabl<$' 13-31 physical properties 01 MC concentric-lay Class A and AA stranded bare conductors, 1350 H~1S. tabl~ 4-5, 4-7 of aU-aluminUm 1350 of various hardnesses 10 Class B, C, and D stranding, table 4-8 of aluminum wrougIil tws condl..lCtOr alloys, table 13·2 treatl"rlen1 for Improvement 01, 1-4 pipe-size conductors, standard, physical and e!ectrical properties, table 13-29 pipe-type cables, amoaCity interpolation chart, 9-27 plastic insulation, 8-4 pla$lic-jacketed three-conductor cable, 1 0-7 pias1ic pipe assembly, 11)-9 plastic-type coverings, a~2, B-4 plates, presStJre_ 13-43 plating. connedor, 11·3 plating ihickMsses, 13-41 ploWlng4n method. 11-12 plug-in busways. 1348, ~ig, 13-28 plug-in connections, 1lg.11-26 plug-in power drop cable 7.13 pole support for cables. messengers, guy Wires, lig. 11-30 pole-and-bracket cables, 7-5 poIyamde insulation. 14-5 polyamidliMmide, 14-5 polyester Insulalion, 14·5 polyethylene cross-linlwd, insulating materia1. 8-2, 8... cross-link<$'d, thermosetting, specifications for insula~ tions. labia 8-4 high-molecular insulating materials, 8-2 insulations, 8-2 jackets. &-9 thermoPlaSlic, 8-9 thermosetting cross-linked, g·S polyviny; chloride insulating material, 8·2 insulation jacket 8-2 thermoplastic, &9 portao!e cables, 7.13.11).9, Jig. 10-10 potassium, 1-1 potential gradient, uniformity, 8-1 potheads lor cable termination, Single-conductor, fig. 11-29 power cables 000 volt, 7~2 600 volt, insulated, lig. 10-6 above 600 vOlts, 7-4,10·5 construction. NEe designations, 8-12 joints 1SkV, 25kV. fig, 11-25 inslalling directly buried, 11-12 insulalion thickness. table 10-2 insulators and coverings, NEG designations, 8-12 power factO!' Of insulations, 9-14 po~r rails electric cran<$'S, 13-1 rapid transit. 1$-1 preassemble<:! aerial catlIe above 600 valls, 7-$ preass<$'mbled patallel secondary cables, 1Q..2 preliminary sag tension graph, fig, 5-17 premolded splicing and terminating devices, 11-iS to 11-22, fig. 11-26 pressure casling rolors, 16-4 pressure plates, 13-43 primary aerial cables, q-23 initial sag and tensiOn values, table "·11 vii index primary cable aerial cables, 11~23 15-35 kV two-eonductor concentric flat~strap neutral, fig. 10-18 lor direct burial, duct. or aerial use. two~ductor concentrie-wire neutral, fig. 10·16 With insulation shielding, (to 35 kV), 10-12 pre-assemb!ed triplexed 5 kV to 25 kV, Shielded, fig. 10-14 joinl, Japed, lH8. fig. 11·2] shielded insulated, figs. Ni. 10-13 I.MShielded insulated, fi9. 10-12 URD, 7·5, 10-15 primary distribution cable, 10-10 primary intertocked armored cables, 1Q-12. fig. 10-16 primary voltage drouits, 11·18 product identificatlof'!, 4·1 production of alUminum, Flow Sheet illustrating, 1-2 proof-testing, 1.2-5 propelled lines shot through rigid conduit 17-7 properties of aluminum as a oonduclOl', 2·1 p~ capabilities 01 aluminum C()nduit, 17-3 proof tes1 voltages IGEA, table 11-7 proximity eHect, 3-9, 9-3. 13--15. 13-17 pull line, lor t::able installalion, 11-8 pulling cable in dUet, fig. 11-10, rig. 11-21 pulling tension, 11-11 allowable,11·11 computing, 11011 reducing. 11~10 pulling through conduit, 17-7 PVC, 8-9 PVC-6Q insulation, 8-9 R Ft.,{R<k curlew conductor, comparison 01 basic and 00/' reC1ed, table 3-8 RadRdO ratios for Me an(! ACSA, comparison of, table 3-8A 9,;in efted in l$OIated rectangular conduc1or expressed as, fig. 13-6 l.ii(in effect in isolated square rod and square tubular oondvctots expressed as, fig, t3-7 skin efle¢t in iSolated round rod and tubular conductors expressed as, fig. 13-8 radar test, 12-6 radiation coefficient, 13-2:1 radiation emissivity, tatne 13-9 radiation heat loss. 3·20 radialion loss, 3-10 radii 01 gyration, 18-3 radio innuence voltage, 13-19 radio transmitting capacitors, 1$·2 "randOm lay," 9-10 ,at"" 6O-cycfe ac:de, estimating, table 94 ac resistance 10 dc resistance, 3-9 R&:i~\:' 3-9 reactance of bundled conductors, inductiVe, 3-16 bus bar, 13-17, 13-19 calculation. series indUc1ive, 9-9 capacitive, 8-14 01 bundled conduc1ors, 3-9 separation component 01. at 60 lit tne9Onm-mlles per conductor, ta':)ie 3-12 at conductors on rigid cable supports, 9-9 fadOfS, lnOuc1ive, and ~nce resistance, table 3-11 inductive, 13-5 bu.s bar, 13-17, table 13--7 and capacitive. 3-12 separatiOt'l COmponent of, at 60 H2 ohms Per COfI ductor per mi)e, table 3-9 spacing factors, tlibIe 13-7 viii reactance {cot'Itinued) and Z"~uence resistance. 3-16 leakage, 3-12 series inductive, 9-2. 9-8 ShUnt capacitive, 3-17,~, 9·j2 total system. 3-12 values, 9·3 zer<rsequenee capacitive, 3-18 reaming rigid conduct, 17-6 reduction of alumina, elactrolytic, 1-1 reduction of breaklng strength, fig, 6-4 refraclOly crucible, 1&3 relative permittivity, 6-13 relaying, shield, 8-10 RNistance and Reactance at Aiumtt'IUfr! Conductors, Steel fMinfOlced, The, 3-13 resistance of aluminum oable with rubber and thermoplastic m~ SUlation, table 9-5 bus bar, 13·17 cable-conductor, 9-3 calcutalion of ac, 3-8 conduit, 17-5 constric1ion, 13-37, fig, 13-17 contact, 1340, fig. 13-18 effective, of a capadtor, 15·2 oIloil electrodes, 15-3 film, 1$-40 insulation, $..12, 8-14 1emperatUffl corrections for, table 8-15 muUiplying factors for thr~ayer ACSR for aluminum condoctivity of 62%, fig. 3·9 oVerall, for Iriplexed thr~nduCl:Or assembly. fig. of "" strip magnet condudor, calculating de, 14-6, 14-7 welding, 13-46 zero-sequence, and inductive reactance, 3- Ul factors, lable 3·11 resistance-bridge loop method, 12·7 resistivity calculation 01. 3-7 constants,3-7n earth thermal, 9-23 valoos tor aluminum wire alloys at 2O'C, dc, table 3-5 resonance, 15-2 resonance puisatloos, bUs conductor, 13·27 resonant freQuencies, rectangular bus. fig_ 13-14 reverberatory furnaces, 1 reverse twist (RTS), aerial oable assemblies, 7·3 reverse twist, secondary cable, 10-2 Revue GeneraJe d l'e.lectriCJte. 14·7 RHO, 9-24, 9-23 ribbon cable, fig. 10-8 Rifenbert. R.C., 11-10 rigid conduit acWantages, 17-1 composition, 17·2: manufac1ure, 17-2 I'iSer Shields, 11-1$ AN, radio-ir'lfluencevoltage, 13-19 riveting, 8-10 "redding out," 16-3 Rodee. Rio(, 5-10 Rodee Graphic Method. 5·10 Roehman, LE. 17-4n rolling. 1-4 ~ch stranding, IH rope-concenlric stranding, 2 rope-lay construction. 3-3 a..s. a w roIQrn aibys, oontamination of, 16-4 for ir'li1uctiOn motor, table 16-1 selec1ion, 16-2 cast, comparative pertormance, 16-1 casting, melhods, 16-3 problems, 164 rotof$ (continued) thermallreatmenl, 16-4 temperature, 16-4 vertical press me1hOd, 164 olosed-slot, fig. 16-1 (b} construction, squirrei cage, rIg, 16-3 cracks, 16-4 die-oastlng.16-3 dross defect. 16-4 electrical conductivity, 16-1 'fractional horsepower motor. 16-3, 16-4 heateapacity,16-1 heat conductiVity, 16-1 ingot. 16-2 electrica! conductivity, 1&-1 manufacture, 16-2 furnace equipment, 16-2 melting equipment, 16-2 pressure casting, 1&-4 open-slot, fig. 1&1(a) die-cast, fig. 16-2 shrinkage, 1&-4 weight 18-1 found-tube bus, '$-9 found-tube bus conductors, physical and electrical prop ertles, table 13-28 round tubular bus oonductors, 13-9: round wire, lilm-insulated. 14-1 round-wire armor, 7-5 rubber, 2-3 ethylene-propylene, S--5 fluorinated e1hyleoe propylene, 8-5 jacket specifications, table 8-5 natured speMlCali<ms tof insulations, table 8-2 synthetic, Insulation, 8-4 specUioabons for, tables 8-2. 8-4 neopilrene, 8-5 rubies, 1-1 tuhng spar'!, 5-4 s salety factors, station structure, 18·9 sag and arcing, 6-2 Chart, initial stringing, 5~4 chart when supports differ in elevatIOn, fig. 5--6 oorrec1ion fOr loog spans, 5-7 CUMS, fig. 5-1 final, template parabola for, flQ. 5-5 negative:, s-a temperature effed on final, 6·11 when supports are at different elevations, 5-8 sag-span parabola and temp/are, 5-7 sag-tension, 5 2 oharts for variable--Iength spans, initial and final, 5-2 graphs, for composije conductors, 5·t8 preliminary, fig. 5-12 preliminary, and oatenary curve, 5-10 preparation of, 5-10 final. fig. 5w4 initial, fig, 5-2 initial and f:naI, of a designation conductor, span. and NESG Ioa<fing lor various tOO1peratures, 5-14 values, initial, for primary aerial oables, table 11-10 for service-drop and secondary cable, ta~e 11-11 at various temperatures, table 5-5 sal! fluxing, 16-$ sapphires, 1-1 SBR, a-4 SBA insulating material. 8-4 Schung, OR, 3-19. 13-30 $chung & Frick 3-19 scrap value, la-10 SCf'a1ch.brush abrasion, 11-4, 13-41 w 10·5 aeries indut1ive reactance. Dl'imaty cable. 13-5 stress-strain curves. table 15·7 gutter. 13-6 slick fod. double. 10-1 initial stringing sag and tension values. mechanicai and efectrical properties. 9-2. 11·1 Shrinkage casting. fig. 4-10 and solid conductors. 7"1 compressed 7-1 conoontric-Iay. 6-9 latera!. 6-9 loading. table 13·19 speci1ic gravity. fig. fig. 9-28 phase-to-phase. 9-8 calculation. 8-10 short circuil in. 14·2 Standard Handbook fOr fiiectneaf &1gineefS. ACAR. a-1 sheath. 8-1 stranded conductors. at serviCe-drop span damp. 12·2 sheathed cable. 1-4. 7. 6-10 . 8-2 street lighting. 3-3 stranded conductors. 5-4 use ol. 6-13 on DUS conductors. 2-1... 11-28 splicil'1g. 6-14 self-supporting towers. stt1poonductor. Brown and. table 8-6 tor tubber and 1harmoplastic Jackets. 6-1. 10-2. 11·11 insulation thic'<nesses. 1·2 spacers fOr bu~ conductors. 1&2 tensile and yield.2. stringfrg. initial. 3·11 in isolated rectangular conductor. &-13 silica. 3·12. installa~iOn details. 11-4 ¥S. 10·1 neutrai-supported triplex reverse-twist. fig. 7-5 service drop. 3·9. fig. differences between. 9-28 conductors.(. impact. table 3-12 inductive reactance at 60 Hz megohm miles per c0n ductor. 18·7. 74 materials. grounded metallic. 18-1. 3·2 solid-roond 1350 aluminum wires. 2~3 conduit. 11-31 taps. compressive. fig. fig. 3-3 tensile and yield. &-10 retaying. 10-' neutral-supportea. 1·1 specilic inductive capacity. fig. 16-7 separation oomponent.ial stringing sag and tension values. 5-10 standard designations for allOyS and tempers. fig. 3-2 methods ot cable. 16-4 use in ACSA. Type SE. 16--4 squirrel cage rotor with surrounding Iron removed10 show construction. 13-24 short-circuits {continuedl CJJ~ts. table 6-12 heat sHedS. 8-13 specitICatiOns for cross-linkOO thermosetting. f:g. 13·14 S~edamper. neuttal-messenger-supported. 7-3. 4--2 Skin effe<:t. 11-1510 1H6 insUialedcables.16 !n shields and sheaths. 11-22 neutral-ooppor1ed duplex. 6-15 spacing between cables. 50-12. 11-15 ini. 1-6 sl'lort-oircuits. a. 13-34 no1 maintained. table 13-7 insulator supports. 11-16 stress-strain. 16-4 shunt capacitive reactance. 5-7 shield condtJCtor. table 17-5 laminations. table t3r l' capatitive reactance al 60 Hz megohm miles per conductor. 17-1 vs. 17-3 vs. 14 strand shielding. fig. 9·2. 14"10 soldering. fig. 7-6 shielded primary cable in jacket.index screw. 14-11 shielded portable cables. fig. 8-2 rope-bunch. 1350-H12. 1·5 stamped laminations. 14·5 Silver. 9·1610 9-20 curve of a-c wave during offset.8·10 strand. etectr:car cliaracterlstics. 1-5 stands. grounded. fig. tables 4-9. 13-25. difference between. fig. 18-9. 11·31 secondary-distribution cable for underground residential distribution. 9-9 01 bundled conductors. table 10-3 DOWer and lighting.13-16 factor for solid-round or r. fig. 18-11 serni·ilexible towers. fig. 9-2 between bare metal parts. 10-1 neulral-supool'1ed. 13-2 and elongation. table 13-22 interface compressive..). 9-3. 14-4 solid and stranded con(luctOf'$. 50-7 stringing sag chart. 1~2 preassembled parallel. 6101·T6.plex and dupleX. 1·1 smoo/\ 1~1. table 6-3 splice data for electrolytic foil. ~ in wefd. 2·2 solder . quadn. 13-40 srres.·2. fig. calculation of. 2~2 bus CQfiducIor. weight of. table 11-10 stringing sag and It'nSion values for service-drop and seconda. 5-7 sheave frictiOn. fig. t. ratil'lgs. mul~ tiplying lactors lor. table 13-17 cables. 8-9 sector bus. 9·9 factors. 13-1 tlmMemperatlKe for l350-H19 aluminum wire. 8-14. 1-1.12·1 lor insulated cables. fig. lable 10·2 neutral-supported. 10-2 spJice kit. 8-10 shielded cable. amapacity grouping factors. 11-13.6-14. tabie 11·11 tine covering. 5-4 stringing sag-tension values fOr. 3·9 steppe(!-parallel bus bar ammgement. 9-10 series street lighting. 9·8. fig.!. 11~14 maqnel wire. 14--2 square·tube bus. 7~3. spedfIcations. 9·8 of insulated condudors. and quadruplex. ICEA. . 11-23 for URD. 3·19 side swing. fig. 14·2 comparison chart. f19" 8-7 strain hardening. 9-1 ¥s. 8-2 rope-concentric. Ihree·COf'\d1Jctor. 13-47 self-damping protection. 18-1 strength.. 8-10 1hree-conductor.it'1ginQ char1 completion of.8-1 shipyard cable. 13·' Size relationships. 16-1 squirrel cage motor.propyteoe rubber insulations.-'24 Shalpe gage. lines of force in.8·10 ifl$Ulation. rolling. 11~14 details ot method. 5·10 typical for various kinds of composite condUdOra. binding head. 13-1.ry cables. table 4-3 loss of eonductor. 3-1 sheath. 13-9 square IUbular conductors. 13-47 station structures. 10-5 shielding insulation. poIyethyiene and eth yJene. 5-1 tensile. 12·1 pertormaoce. inductive reactanoe. factor K 1:. nomogram.. triplex. table 44 spacer cable. 13-46 sirength 10$$ due to overload. in outdoor substations. 6-3 va:lues for wek:ling. 1abIe 1H 1 . 1. 18-8 thru 1$-13 steel. 12. 10-1 three-cooductor ~ntric neutral.!. erties. 3·2 stranding. mechanieal and elec trical properties. aluminum. ccrroSion. 12·. by use of parabola totmuta. a· 1 methods.. aluminum measured temperature rise under short-drruil conditions. 3·1 aikaklminum 1350·H19 compact-round. underground in duct. 1·4 arrangements. 16-3 stabllizing. tabJe 8--5 for thermoplastiC insulations. 17-2. acting on suspended paraltel conduclors. bolt.13-12. 1H'i Insulation. 8-9 neutral-supported. 3-5 compact. 5-16 slress-strain graph. tabla 13·29 sqUirrel cage induclJon motors. direct burial. 10-4 type SE-style SER. aluminum. fig. tables. physicaf and electricel prop. table 3-9 SER cabte. type SE-style U. fig. 13-47 magtW'I wife.11-a neutral-suppo!1ed duplex. skit'I etfed in. ligs. 5-23 sodium. trlple. 15-8 snaking. N2 siliCQlls.s. 10-2 shape oorrectlon. table 3-48 ratings of conductors in ASTM Standards.s straet lighting standard. 2-4 snUbbing principle. 7·3. 5-6 initial. aluminum. 13-3 Sl. alwrnnum conductor alloy data.rouJar conductor at 60 Hz. 11·24 service-entrance cable. 6-9 rating factors ACAR. 7-4 secondary tTiplex cable. fig. fig. 7-6 jacket. 6·. 12-2 sheave. 10-9 span damp. . series.Ooints. 3·3 steel-rein10reed aluminum conductor. table 8-8 for Mlural and synthetic rubber insulations. 6·10 metallic. bus conductor.heat zone. 11~3 secondary cables circuits-600V. 10-a secondary line wire covering. 3-17. 8-1 1350 aluminum conductors. 7·3 sheaths. 13·27 computing. fig.9. temperature rise tor aluminum and steel conduit. 13-8 segregated bus. 12·2 temperature limit lor insulaled aluminum conductors. 1·4 station bus. 10·11 shielded inert arc welding of strip conductor. 14·4 ulg systems 11~14 springbaCk. 10-2.relief cones. fig.. 8-12 short circuit in. 1·4 rotor. 6-11 temperature-time. 13-43 In heavy series bolts. table 5·3 strip. fig. 1:). 12-6 tracldng. useful formulae. 6-5 1hermose:Iting inSIJlating materials. lable 5·5 tension stress-strain curves. rT'IiitSsengers. &4 limit.. 18-6 thumper. 144 coil design. 11-3 lugs. rig.O. 2-3 sun. self supporting. fig. 3-15 sun heat gain. 14-7 tfiree.8 USE cable. fig.-9 expansion support ior. 5·25. 5-~1. 1:). magnet wire." &-1 allowable pulling. 13-4 of wire materials. span and NESC loading for various temperatures. muHiplying fader tor variouS conditions of. 1U. 15-2 temper designations. 17·6 labeling of cable. 600-100OV. emissMty.. 8-1 limit. 5-5 s. table S-6 of wire malerials at various temperatures. 18-13 substation structures.. fig. P. 14·1 charactefistlcs Il'IStilabOf'l applie.oidal strands. fig. 6"':. underground service entrance cable. 13-8 tum insulation. 18-4 transmission line faults.s damage." 18-4. table 4-3 1350-H12. 13·52 conduit alloy composition requirements. reduction of impedanoe by adding. 12-6.!um(num oondllCtoffl. 10-4 three-conductor shielded cabJe with lmer10cked or cor rugate.l) coefficients of resistance for bus ()()I'lC$oc1or alloys and representabve value for copper bus bar. table 9-7 insulation. overall reSistance and acidc ratio. 3--2 and elongation. 18-8 semi·f!exibie. 11-26 terminations building wire. 8-12 limit of lnsulatioo and ampacity. 1341 suspension ctam~. 12-1 . altitude. fig. bolt. 10-5 thr-ee--conductor nOfNnetaj!ic jacketed cable.1{)"20 Underground Oi$(fibUtfon. 13-18 switchgea. 14-7 strip wound coils. tables 11-2. 13-5. lig.l armor.. lor am· pacity ratings. 16·4 thermoplastic insulating materials.. 17-1 rise in bus. fig. 18-4. 1(). extruded aluminum.l to aluminum. 14·9 insulation. 1a-S H-frame. table 3-7 x temperature (contlnue. 18-6 structural shapes. lXI.. 16-5 use of aluminum In.11-24 - adVanI:ageS. 8-4 submarine cables. arrangements of cables in. table SA·' covering. 2-2 torQue. 11-13 undergound dud.. 13·12 shor1-ci~uit load. fig. fig. 10-5. and guy wires on poles. fig. 5-23.2.6 tracer/detector method. fig. table 13·3 conduC1or. schematic. 18-9 1hr'ee-poIe guyed. 1a-. 18-4 guyed "gull Wing. 18-8 composite. 11-3. fig. 3-12 pnmaty cable in 00. fig. 13-16 tubular bus conductors. 6-10. 2-3 resistivity. 5-7 stringing sag values. 14-$ Tuttle. contact. 3-13 two-conductor. fig. ii-13 for insulation. ill effects. bus conductor alloys. 11-12.LJmits in me Rating 01 £1ecttic Equipment.. fig. 1·7 T6 (temper designation). fig. 14-2 conduc!Mty. 11-11 tensions and sags. fig. 6-1 linear expansion. 3·20 support unbalanced 101'00 at. Special Technical CQrt/erence Thomas.r power. fig. fig. 14-1 Teflon. 5-10 Stlppot1ing cables. fig.. 13~20 ~e. 11·21. 13·1 template half"iXItiine for COtIductQf. lor insulaled aluminum cot'Idictors. final." 18-4. 11-2S UFlD6OO\ftlg. 1{). Generot Principle$lor.. fig. &. 8-1 lransnion pieces to join strip ccoductors. 16-4 - for 14A kV substation. 5-3 initial. fig. 144 thermal advantages. 3-' synthetic rubber insrulaiion.14 treatment for improvement of physical properties. table 18-3 structural design. types of a. fig. 18-7 single-rnast. Itg. 5-23. e.H" 5-10 threading rigid condurt. 12-7 tie wires. 11-2 insulated cable. table 13-3 thermoplastic jael\et specifiCatiOl'IS. table 9-7 temperature-resistance coefficients lor various temper atures. 5·4 stringing sags tor various spans. 7-2 treeing.oonductOl'ouldoor.9-$ corrections for insulation reslstance. 13-41 jacket. 18-3 thru 1&8 designs. 10-e UL·S57. 10-16 three-pole guyed towers. template paraOOla for tinal sags. 11~1a. tl'W magne1 oondtietor. IEEE. lor insulation. &10 terminals. fig.-21 tubular bus. lig.ce emissivity. table' 4·4 structural aHoY$. 5-2 Initial and linal. 14-7 dielectrio at. 10-7. 9·1 tube bending chart. 18-6 guyed "Detta. 1343 torQue in heavy series bQ!(s. 1$-48 sulphur. undergrouod leader cable. 5-14 values at various temperatures. fig. 6-9 trapezoidal wires in composite conductor. 18-4..a tensile load. lable 14--5 strip magnel conductor. 1-4 tree wire. 3-2 tensile strength. 11~2S single-conductor poltleads lor cabie. 13-26 bus. &9 factors in se1ee1ing cable coverings.. e-1 factors in seleCling insulation. 11·27 technical advantages. 13 2 "tension IimiIs. 14·9 aging aluminum and copper magnet Wire. 3-3 traveling waves. 13-$7. aluminum. fig. 9·23 surfa. 13-40 surtace preparation lor bolted oonnec1ions.lig_ 15-3 terminating. 18-10 6061. 18-4 foundations. 2·3 properties. table 18·2 6063. 8-4 tmekness. 9A~2 . fig. figs. llH 2 styrene-butadiene synthetic rubber insulatiOn. fig. fig. copper. 13-15 switchboard clearances. 14-6 coil inductance. 17-{) tnree-cooductor 5 ~V 10 35 IN Shielded three--conductor cab1e.11--3 torsional rigidity. earth. 13-8. fig.index sl1inging sags and tensions for constant lensioo of a given temperat\ife. 1-5 _ature ambient. f'9_ 5--$ time-temperature percent strength in 1350"""'9 aluminum wire. table 13-22 ~e clamping iorce ior bolls. 4-3 tapes. 5-7 stringing sag tables.7 NM cable. fig. fig. 14<>9 winding design techniques. 18-7. aluminum magnet wire vs. 12·5 triplexed three-conductor assembly.. SA-i. P.::: guyed ''Y. tables 13-17. 1&-7.13-49 91'01JnQ.16 Type Type Type Type Me cable. 7-S subs1a1lon. 8-9 specifications. 16-9 designs. M 1:3-7 terminal insufalion. 6-11 tempers used lor bus conductors.lvarrtages. aluminum oondudO( alloy data. fig.11-30 in vertical raceways. of a designated condUctor. 1z.8-10 dimensions. 12~7 tracer equipment. table $-2 stringing sheaves. 8-9 thermoplastic polyvinyl chloride. substatiOn. 3-19 for casting rotors. table 11-9 insulating. fig.type outdoor. 14--5 telephone circuits. 3-7 trapez. 11-27 UF. 1e-S tracer current faut!: delec1ion. 1·7 tables. plating." 18-4.1 ultra-violellight. fig. 18-5 guyed "V. 8-4.'' 18-4. 11-29 strip conductor. 16-4 coefficients of de: resistance. 14~10 lransmission towers. 13-50 symbols to. 1iM'3 NMC cable. fig. AlIJmjnum. coated. S·1(}. 13-4 tube welding." IEEE Pub" 14·2 rise during short circuit steel conduit \is. table 11-6 surtac:e area. 3-8.wire neutral primary cable. 18-8. 14-5 strip conductor alloys. 11~2 mechanical. 6-13 swinging suspension for high-current bus. 1·7 T8 (temperdesignalion). 18-3 toIa! system reactance. 8-10 taping insulation. &-1 T T (Iemper designalion). 8-9 thefmosetting cross4inked polyethylene. fig. 10--8 USE. coooentfie. 10-15 towers assembly by helicopter. 18-6 to 1l:H3 substations.3·8 temperature-time strength loss. 144 single conductor. 12>-5 traCking ~bility. fig. fig. titanium. ~tage. fig. lig. list of in chapler 4.8-12 emergency-load. 1(). Shor1-circui'. 8-4 system regulation. 5-20 sway. 7-4 u UD splice diagram. 13-21 treatment 01 rotor castings. table 8-5 !hemloplasbo polyethylene. a·g unbalanced force at support 5-10 Underground DistliblJtion Reference Book. lig. . table 10-4 w washers. chemica! composition limitS (maximum. 6-1. 5·22 welding. 7-2 unilomrthiJ. table 13-23 water absorption. Skin Effect in Tubular and Flat Conductors. 13-41 Be!leviUe. Bectricai Transmission & Distri/. 1$-2 z . 6101~T6. 7-4. fig. table 2·2 light. 2·1. 3-18 Impedance bare eonductof'. 3-16 resistance and Inductive reactance. 13-47 welding-equipment cable.Jution Reference Book. 15--2 waxed paper capacitor. 10-15 underground seMCe entranoe insulation materia!. 8-Al venting problems. tabJe 1H6 vibtation aeolian. 6-13. 17-4 voltages for determining insulation thickness.' xi . 11·24 URO secondary-diSiriblJl:lcn cable. $trip magnet conductor. H wori<ability. table 15-3 strength. 6-11 wind lOad. URC 6-2 wiring (continued) interior (branch circuits to 30 amps. 13-46. for. 1a-a transmission tower.. table 1-6 "ight atunjnum conduit vs. 3-11 zinc. 8-5 Underwriters Laboratories.4 x and geometric mean radius. bus atlOy. 9·8. 8-12. 13-47 GMAW. 13-4'7 gas. table 3-12 ~ of induC1ive reactive at 60 Hz ohms per conductor per ~ ~ mile.ness angle." 5-12 wound cores.l. strip conductor. lable 9-6 rigid conduit circuit. lable 13·31 unitonn-!hlckness channel. 14-3 wound paper capacitor. 3-11 wrought aluminum alloys for electriooJ condUClol'$ in percent. 18-10 exothermic. 18-3 weld S!tength values. table 6·1 "unipass" jaekelS. 13-27. table 13-30 unilorm-lbicJ. bus. fig.. 11~2 Wohler. apartment-house. stool. 13-33 bUs conductor. 10.miles per ooMuctor. 13-46 tungsten inert-gas. table 13-15 vinyl chloride. 10-8 v vectorial relationships 01 currents in an insulator.B. 5-8 uplift fOrce. 5·21 \ 6-14 overhead cOnductors. 8-13 watl!oss in a capaCitor'. fig 5-7 upper temperature limit adjustment. table. 9-6.13-46 inert~ shielded. 1-5. AWS HandbOOk. 13-46 GTAW. 13-1 strength. 1350-H12.12 uplift condition. c0m parative. 13-46 welded aluminum-to-aluminum connections. 14·10 Welding Aluminum. 600 volt. 16-4 vertical raeewa~ 11-10. physical and electrical properties.13-28 dampers. 15-4 weather-resistant cOverings. 9-2 VOI1age-<:lrop. 9-a. table 3-9 XHHW. diameter and thickness. flQ. 3-3 windability. 3-14 of oapadlille reactance of 60 Hz megohm. s-9 volt-ampere vector relationship. H. 13"11 uninsulated conductors· coverings for. 3.index Underground residenlial cistribution primary cables. S-10 urt$hieIded cable Insulation. lig. &-5 XLPE. '4" window area.. Sw5 y yield yield yield yie1d limitations. 3-14 wind damage. 5-23. 11-7. 14·2 winding design techniques.tIon structures. foil. cap<lCitor. 13-44 flat. 13-46 ultra-sonic. 1Q. '7-6 WestinghOuse. 14-3 wire-drawing... 2-2 "WOTking Jimil. 2·1. 13-11 uniform-thickness angle bus conductors. calculation of. fig.s of bare conductor in direct-eurrent conductance. 17. 12-1.. 13-46 welded connections. 1-4 wiring.ne:$$ aluminum channel bus conductor~L physical and electrical ptOperties. 2-2 of su. a-2 comparison of cOverings.zero-sequence capacitive reactanoe. 9-12 line--to-line. 1$-7 strength. 15-3 Wright. . 1o-e. 6-2 URO primary cables.lB. fig. 16-4 verticeI press method of rotor casting. 13-4'7 flash. Friedrich. 10-11. &-11 vibration-free span length. to-H) UAD secondary cables [600 volts). 2-2 """""'9.