Differences IECIEEE

Differences between the IEC and IEEE electrical equipment standardsIEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www.ieee.or g/ia s REVIEWING EQUIPMENT STANDARDS G LOBAL USERS OF ELECTRICAL power equipment are increasingly given the option of using equipment that implements either the National Electrical Manufacturer’s Association (NEMA)/the American National Standards Institute (ANSI) or the International Digital Object Identifier 10.1109/MIAS.2013.2282565 Date of publication: 31 October 2013 © ISTOCKP HOTO.COM /ROBE RT CHURCH ILL B y M a r c e l o V a l d e s , X u h u i Re n , S h r i d h ava l Sa p r e , M a r t y T r ive t t e , & S t eve n M ei n e r s Electrotechnical Commission (IEC) standards. In many parts of the world, either set of standards may apply. IEC and IEEE standards have come substantially closer over the last decade. However, differences remain. In this article, the authors will explain the differences in the applicable standards and what those differences might mean to a user. The intent is to provide the user with an analytical basis upon which to understand the 16 1077-2618/14/$31.00©2014IEEE o rg /ias ANSI. IEEE standards are written by IEEE working groups (WGs) sponsored by various IEEE committees. CBs may be one or three pole for use in single.tradeoffs that may be made in choosing one set of standards over the other. government. a base document for CBs [7]. test requirements. These committees and WGs are manned by industry experts from manufacturer. and related technology are the C37 standards [5]–[14]. The main IEEE/ANSI standards family that defines MV switchgear. sponsored by the Switchgear Committee of the IEEE Power & Energy Society.2) c) ME interrupter switchgear (C37. Similarly.ieee . The predominant IEC standards are the 62271 standards [19]. however. Common Specifications [21] IEC 62271-100-2008-04.04 [5]. circuit breakers (CBs). CBs with controlled per-pole mechanisms intended for nonsimultaneous operation are not included at this time but are under consideration for future inclusion.3) 2) ME bus (C37.# series [9]–[13] define the requirements for CBs and equipment. [22]. The ANSI adopts these IEEE standards. Common Standards Scope Both sets of standards rely on a base document for common requirements [14]. 4. The IEC standard voting process is focused on balanced participation from the various participating countries. the equipment that is built to meet these standards and the needs and desires of the various markets that use the equipment also differ. The IEC standards do not have an MC versus ME gear. Devices that depend on manual operation for closing or opening are not included. [35]. IEEE. 4. Other standards. in fact. and other items that warrant separate treatment. manufacturers offer equipment that predominantly reflects the traditions and requirements of one set of standards but is offered to the market as meeting the requirements of the other. Electrical Equipment Standards From a myriad national standards for medium-voltage (MV) electrical equipment. define test protocols and acceptance criteria used by Underwriters Laboratories and significantly mimic the test sections of the C37. AC Metal-Enclosed Switchgear and Controlgear for Rated Voltages Above 1 kV and up to and Including 52 kV [35]. CBs and associated switchgear for 50 or 60 Hz and applications above 1. The scope of this article will be devices covered by the IEC 62271 family of standards: IEC 62271-1-2011-08. To state that one standard is better than or not as rigorous as the other would not be correct. and their differences merit recognition. which are in turn sponsored by IEEE Societies. either as the accepted standard or as the predominant model for local national standards commonly used within a particular country.20.5# [15]–[18].or three-phase systems. This type of hybrid product is becoming increasingly common in North American markets and is. The final vote on IEEE standards is performed by members of the IEEE Standards Association via an online vote handling process to assure balanced participation and inclusion of various perspectives and opinions. user. The IEC relies on two sets of definitions 17 . IEEE C37.1) b) metal-clad (MC) switchgear (C37.20. Both sets of standards also refer to a long list of other documents for test protocols. IEC international standards are also consensus based and are written by manufacturing.000 V. Table  1 lists the common ratings defined within IEC 62271-1 [21. The 62271 numbering system has organized the various relevant documents within the IEC standards into one numbering system. [21].21). and in the case of C37 standards. Other C37 standards define applications and other related parameters. Over the last decade. user.06-2009 [7]. IEC 62271 Series IEC standards describe various subsets of devices covered by various standards and limit the scope within those standards. [6] and the C37. and NEMA ANSI standards for switchgear are written by IEEE WGs. [18]. ▪ ▪▪ ▪ ▪▪ I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w. those issued by the ANSI and IEC. Sec.20. however. In some cases. Additional related standards are used by NEMA members to document test protocols and criteria for verification of adherence to the standards [17]. [21]–[35] written by the 17A and 17C committees. and a base document (or two in the case of ANSI equipment) for the equipment [9]. In some markets and applications. Alternating Current Circuit Breakers [22] IEC 62271-200-2011-10. sponsored by the IEEE Power & Energy Society’s Switchgear Committee.23) 3) control switchboards (C37. these standards have come significantly closer. 43–44]. IEC standards predominate in Europe and much of the rest of the world. IEEE standards for switchgear assemblies are divided into three categories: 1)  m etal-enclosed (ME) power switchgear. users have a choice of buying and installing equipment to either of these standards as well as local national standards. This family of standards was first published in 2001 under a new organization using the 62271 prefix. and published by the IEEE. applicable to. ANSI standards predominate in North America and are generally composed of documents created by the IEEE or NEMA and adopted by ANSI as broadly accepted consensus standards. and design representatives from many countries around the world. pp. influencing how the North American standards are evolving.20 standards. Manufacturers often design a product for one set of requirements and then modify it to meet the requirements of the other. 32] and 62271-100 [22. [10]. IEEE C37. and consultant ranks that volunteer to create and maintain the IEEE standards. further divided into three categories: a) low-voltage power CB (C37. Each member country has one vote to accept a proposed standard. two sets of standards emerge as predominant. specific requirements for special applications and definitions of various conditions.20. p. Sec. C37. They are different. they incorporated material from other now-superseded IEC standards that are several decades older. they remain different in several ways. 4.7— Guide for Testing MetalEnclosed Switchgear Rated up to 38 kV for Internal Arcing Faults j)  Ratings of the internal arc classifications (IAC). Optional within IEC standards.or g/ia s h)  Rated supply voltage h)  Rated values of the of closing and components forming opening devices and part of the metalof auxiliary circuits ( U a ) enclosed switchgear and controlgear i)  Rated supply including their frequency of closing. —Arc-resistant(AR) preferred ratings are covered by this C37. Optional within IEC standards.i) Rated filling level (fluidfilled compartments) filled compartments) —Where multiple symbols are listed as “or. 15 a) R  ated voltage ( U r ) and number of phases b) Rated insulation level c) Rated frequency ( fr ) d)  Rated normal current ( I r ) (for main circuits) e) Rated short-time withstand current ( I k.1. 9 a)  Rated maximum voltage ( V ) or ( U r ) b)  Rated insulation level ( U d ). ( U s ). 3.TABLe 1. BASIC SWITCHGEAR RATINGS STIPULATED FOR IEC AND IEEE EQUIPMENT.2-1999. p. see the “Switchgear Type: MC. pp. Sec. 38 IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www. Optional within IEC standards. 32 a) Rated voltage ( U r ) b) Rated insulation level c) Rated frequency ( fr ) d)  Rated normal current ( Ir ) e) Rated short-time withstand current ( I k ) IEC 62271-200-2011-10. k) Rated filling level (fluid. IEEE C37.20. ( U p ) c)  Rated power frequency ( fr ) d)  Rated continuous current ( I r ) e) Rated short-time withstand current ( I k ) IEEE C37.20. ajor subcomponents and assemblies are completely ▪▪M enclosed by metal barriers with no intentional openings. All live parts are enclosed within grounded metal  compartments.20. ME. 5] that may be summarized as follows (italics are added by the author): Drawout self-aligning CB element with  a connected  and disconnected position with self-coupling primary and manual or self-coupling secondary terminations. Sec. 4. operating devices and opening devices and auxiliary equipment of auxiliary circuits j)  Rated pressure of compressed gas supply for controlled pressure systems IEEE Standard C37. 6 a)  Rated maximum voltage b) Rated insulation levels c)  Rated power frequency d)  Rated continuous current e) Rated short-time withstand (avg. 4.1-2007. such that when a cubicle door is open on a closed CB.100. 2.7 standard.6 # rms-first cyc. The main interrupting device or mounting shall include a metal barrier. p. are used to cover the primary connections ▪▪ ▪▪ ▪▪ . 4. p. p. Sec. t ke ) (for main and earthing circuits) f) Rated peak withstand current ( I p ) g)  Rated duration of short circuit ( t k ) h) R  ated supply voltage of closing and opening devices and of auxiliary ciruits ( U a ) i)  Rated supply frequency of closing and opening devices and of auxiliary ciruits j) R  ated pressure of compressed gas supply for insulation or operation f)  Rated momentary with.. 18 for partition class and service continuity. Automatic shutters. rms current. the symbols are common. 2 sec. p.ieee.6 # Rated rms current ( I p ) short-time withstand) g)  Rated duration of short circuit ( t k ) IEEE Standard C37. I pe ) (main and earthing circuits) g)  Rated duration of short circuit ( t k. if assigned by manufacturer. the second is the IEC symbol.20. ANSI MC switchgear is characterized by several features identified in C37. Sec. —Where "or" is not stated. and Service Continuity” section.2 [9. I ke ) (main and earthing circuits) f) Rated peak withstand current ( I p. Sec. no primary live components are exposed.06— Standard for ac HighVoltage Circuit Breakers Rated on a Symmetrical Basis.5. which cover primary circuit  elements. Pk. 5.” the first is the IEEE symbol.) IEC 62271-1-2011-08. Table 18.f) Rated peak withstand stand (2. Both standards define special conditions as ered by C37. Manufacturers Primary bus conductors and con requiring a voltage to be applied for a nections are covered with insulatfixed period of time.100.100. and Fault Interrupters for Alternating the rating for cold climates as -40 °C to 40 °C and that Current Systems up to 38 kV. However. it is up to the specifications to refer to the proper rating for the application Voltage Ratings and Tests in General when the equipment is specified. The CBs identify which temperature rating is desired.20.000 V [7] I EEE C37. -30 °C. IEC 62271-100 [6] IEEE C37. and hence “S2-type outdoor circuit breakers. The IEC standard also defines the 24-h average Switchgear [9] maximum temperature as 35 °C. Wet conditions apply to reQUireMeNTS Instrumentation and wiring are iso CBs specifically designed for outdoor lated by grounded metal barriers applications. the IEEE C37. Both standards put the responsibility to identify tion of Transient Recovery Voltage for Harmonization with special conditions on the specifier or user. Normal conditions are divided into  ture for AC High-Voltage Circuit Breakers [5] indoor and outdoor in both standards.-30  °C. Both standards one set of for proper operating sequence under define different tests for dry versus wet normal operating conditions.2. One series is at power frequency.60-2003-IEEE standard requirements for -50 °C to 40 °C for very cold climates and 5 °C to 55 °C Overhead.20. Sec. Outdoor CBs have Optional within IEC standards.4.1. they are only equipment. 2. conditions. which are typically used and then from all primary circuit elements. and -40 °C. 2. to specify MC to gain these features. Circuit Breakers Rated on a Symmetrical Current Basis. for overhead lines.2 cle. Standard of Common Require. Standard for AC High-Voltage Temperature and Humidity (IEC 62271-1. jointly published by IEC as for hot climates as -15 °C to 50 °C.when a CB is removed. IEEE C37.3) Both standards provide for an upper-normal temperature Voltages Above 1.ieee . shall focus on devices rated for application MC construction.2.1.and seem to closely align between the two sets of docucal Current Basis Amendment 2: To Change the Descrip. Reclosers are cov. which feature desired when expecting that type of equipment. applied with a defined rate of rise. Optional mostly consist of two series of tests. Generator CBs are cov.America and within IEC markets as well.3-2001.1. For both standards. and Submersible Auto. and 2.2. -15 °C.standard only defines one normal range as +40 °C to ered in a dedicated standard.” the user should specify the features if they S2-type devices are not the main subthe other. This artistruction does not fully satisfy the requirements of C37.000 W/m 2.1. The methods for testing the dielectric capability of The IEC standard defines normal solar radiation on switchgear are similar within the two standards and outdoor gear at 1. Standard for Metal-Clad of 40 °C. and the other often design a ing materials. the normal low-temperature rating structure and construction requirements for all preferred values are defined by the IEC standard as indoor and outdoor types of ac high-voltage CBs rated -10  °C.1.o rg /ias 19 .20.1. It is recommended to be specific on each at 38 kV and below in MC or ME equipment.04-1999 (R2006). The IEEE covered are for use at 50 or 60 Hz. the preferred minimums are -5 °C.2. The defined condiIEEE C37.04b-2008. Standard for Rating Structure for tions are mostly defined within the “common” documents ac High-Voltage Circuit Breakers Rated on a Symmetri.000 V. Sec.3. Pad-Mounted. the traditional IEC MC conapplications above 38 kV. and decay. -20 °C. Since multiple ratIEC 62271-111:2005 in 2005.06-2009. but some are not mandatory by dards refer to this class of devices as requirement of standard in the base product.2. 8.3. Standard Rating Struc. Similar to the IEC standards. applicable to three-pole devices for three-phase systems and -25 °C. within IEC standards. Optional within IEC series requires a voltage pulse to be standards. Dry Vault.1.IEEE documents. For indoor above 1.013. however. This indicates that user specifications need to and single-pole devices for single-phase systems.1.Service Conditions ments for High-Voltage Power Switchgear Rated Above Service conditions within both sets of standards are defined 1.2. 2.000 V [14] as normal and special as well as usual and unusual within IEEE C37. many of America as distribution CBs. and IEEE C37. equipment. The IEEE standard ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w. Standard for Metal-Enclosed normal maximum is the same for indoor and outdoor Interrupter Switchgear [10]. has traditionally been called MV switchgear in North The main IEEE standards germane to MV and high. are desired.1-2007.ments. C37. voltage switchgear are as follows: IEEE C37.2-1999. and Preferred Ratings and Related Required Capabilities for 2.20. The IEEE standard also identifies matic Circuit Reclosers.for very hot climates. ings are possible under each standard. product for Mechanical interlocks are provided  duration. The ANSI standards establish a symmetrical current For outdoor equipment. It is common in IEC regions ject of this article. The standards also include CBs for However. Sec. these characteristics are currently availcurrently both the IEC and IEEE stanmeet the able. traditionally been referred to in North modify it to Within IEC equipment. 2 f.3. p.2 and C37. is the gear only required to operate properly after an event. i. Both standards suggest a space conditioning or heating apparatus to minimize the effect of condensation or extreme humidity. When applying equipment.20. IEEE C37. 29]. Totally enclosed nonventilated enclosures may be required. and 2.2. especially with respect to temperature. Special conditions are to be identified by the user. 40] provides a table with dielectric correction factors and continuous current correction factors from 1. Figure 1. Table C1 within the annex identifies four levels of pollution and the associated minimum required creepage distances. Sec.defines normal as 1. 2. The IEEE standard defines three classes of ice coating: up to 1 mm. However.2.4. Sec.2 extends the range to 6. Within IEC standards.6.2 kPa maximum daily average and 1. which adds voltages found in other markets such as North America.1.2 [9.1.1.1. IEEE C37.2.2.100. and pollution.100. if these undesirable conditions cannot be eliminated. Tilting—Seismic (IEC 62271-1. Normal indoor relative humidity conditions are defined in both standards as not to exceed an average daily value of 95% and an average monthly value of 90%.000 m above sea level.1. Altitude (IEC 62271-1.2.20. IEEE C37. more frequent maintenance may be required.040 W/m2. p. 2.000 m and the formula in IEEE C37. shock.1. p. up to 10 mm.1. Sec.20.81 for nuclear applications.6. Higher wind speeds would be considered special.000  m.6) Both standards define normal and special conditions very similarly.. and series II. which includes the traditional IEC voltage ratings.1. Table 8.4. an annex providing guidance for classifying environments for relative pollution levels is provided.1. and Annex C) Wind is handled similarly within both standards. 2. or during and after the event. Sec. Special conditions within the IEC standard are levels III and IV. 2.1. 8. Vibration. p. The IEC standard also defines values for water vapor pressure: 2. respectively. p. 14] within IEC standards and 40 m/s (90 mi/h) [21.1. 2.e. Both reference IEC 60071-2. The IEEE guidance in C37. depending on design.20.20. and IEEE C37. Forced ventilation with appropriate filters may be required in other cases.20. IEEE C37. 17] for outdoor.24. Sec. The current ratings may be decreased by as much as 30%. if at all possible. Sec. The IEEE standard also mentions that the user must identify what the operational requirements are for seismic events.4.20. 8.100. The IEC standard defines normal as none for indoor and level II as described in IEC 60815 [36. Permissible ice coating for outdoor equipment is mentioned in both standards.2. class 2 [9.000 m above sea level. with 34  m/s (76 mi/h) [14.1. 43].20.1. 8.2. Both standards also advise the user to provide conditions that are as close to normal as possible.1. and both put the responsibility on the user to identify unusual conditions. and attention must also be paid to insulation levels described later in this article. as class 1.1.3. 2. Table 5. IEEE C37. Pollution (IEC 62271-1. Other Service Condition Requirements IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www. p.100. as the formula within IEC 62271-1 [21. sec. and no preferred ratings above 40 m/s are proffered by either standard.1 and 2. Sec. the rated voltage must be equal to or higher than the expected maximum system voltage. p. the IEC information in 62271-1 and C37. dust ingress control is provided by an IP5X degree of protection. Both standards indicate that particularly dry or humid conditions can affect equipment dielectric performance.100. p. 8. p. The IEC standard refers to IEC 62271-300 The IEC standards list two voltage ranges: series I. class 1 per IEEE C37. sec. 5] within IEEE standards considered normal. Normal is defined as up to 20 mm for the IEC standard.2.1-2007 [14] includes a broader list of voltages ratings harmonized with the IEC 62271-1 . Both lists are shown in Table 2.2 [9. 55]. and level II is considered normal for outdoor gear. Seismic activity is expected to be negligible.ieee. 2. The minimum level is considered normal for indoor gear. Sec. Exposure to damaging fumes and dust of various kinds requires proper coatings as well as heaters for the former and proper enclosure accommodations for the latter. IEEE provides guidance on how to account for higher levels of solar radiation in IEEE C37. and tilting.2. Where seismic activity is expected.” Maximum Application Voltage for Equipment 20 Both standards define normal conditions as relatively free of vibrations. 8. 2.4.1 [14.000 m for ME switchgear [10. IEEE C37. and IEEE C37.2.000 to 6. as defined within IEC 60815. and 2. The IEEE standard refers to IEEE 693 for severity level definitions and IEEE C37. and up to 20 mm. both standards refer to other documents for definitions of severity level.1.2.1. Shock. and 2.4. 2.3. I EEE C37. 2.1 only extends up to 4. where the 5 indicates dust protection as well as a 1-mm protection against access to hazardous parts [14.2 f. and 20. 43]? The user should identify the operational requirement regardless of the equipment standard specified. Sec. The IEC standard refers to IEC 607212-4 [39]. Sec. 15] assumes a starting point of 1. and allowances should be made for such environments. Within the IEEE standard. 2. with minor differences.1. the air is expected to be relatively free of pollutants. 6] is applicable from sea level. p.1. humidity. p. 41] advises that “the emphasis should be on eliminating such conditions.2 [9. Both standards refer to IEC 60071-2:1996 for data on how to deal with pollution to achieve proper dielectric performance. 2. The main conclusion is that neither standard seems to offer significantly different capability.1. the formulas differ slightly. However. Sec. 8.4.1.8 kPa maximum monthly average.2.100.20.1. 10.000 m that both define as normal. The IEEE standards have one list of preferred voltages described in C37.20. Table 7.1.3 only provides factors up to 3. Service Conditions Summary Under the normal conditions for indoor equipment.or g/ia s Both sets of standards provide for altitude correction factors to be used to derate the dielectric capability of equipment when used at altitudes above 1. Sec.3) or IEC 62271-2. In North America.091999(R2007) includes single-phase tests at 58% V [8. equivamended time. which applies to circuit breakers above 245 IEEE STANdArdS kV (i. 36 kV-equipment designed with lower insulation levels would be IEC 3. For applications at 12–13. At this rating. and IEC offers 17. but in IEC ratings.20.e.8 27 38 48.25-kV. The preferred rated insulation voltages and associcommittees.3-kV Insulation levels refer to various measurements of dielectric applications is usually suitable for 4. p. equipment. ANSI offers a 27-kV rating. ated maximum rated voltages are shown in Table 3.are similar.lower IEC withstand levels generally are lower than those cific requirements. Basic Switchgear Ratings Ratings for equipment are generally covered by two sets of The higher withstand ratings generally exceed or match documents: 1) the common requirements. Rated insulation levels are defined three ways: light.20. North American standards and fall within the normal equipment service con. 4. IEEE test procedures do not allow any parameters to be The IEEE guide states that 0.76-kV IEEE requirements. The various ratings specified within these standards are lent slightly higher rated voltage IEC gear may be applied.” This same IEEE standard suggests a list of voltage ratings to be used in future IEEE switchgear standards that is fully harmonized with IEC 62271-1 with respect to rated maximum voltage and rated insulation levels.2 for the next lower or equal IEEE-rated voltage. cumulative effect of high temperatures. switching impulse (U s ). and the [21] and IEEE C37. The IEEE guide equivalent equipment.76 8..100. humidity. IEC 62271-200 and IEEE C37. both ditions.2 & C37. the TABLe 2. Tests. kV ANSI offers a 27-kV class of equipment. The test condi.20.5-kV-class equipof pollutants.2 12 17.3. SWITCHGEAR VOLTAGE CLASSES. IEC 62271-1 the closest equal or lower IEEE-rated voltage. 21 . The [13.25 15 27 38 Rated Power Frequency ( fr ) I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w.2-kV are not normal. often referred to as BIL in IEEE mar.9-kV.5 s for time [13.5 24 36 52 comparable to the ANSI 27-kV Series class of equipment.the IEC 3. and air pressure that are similar across both sets of 7.1 s is the minimum recom. IEC 62271-1 identifies possible frequencies as 16 2/3. and more than 1 s is considered unnecessary. one needs to jump to 36-kV class equipment. The IEC standards do not include similar tests. For 34. are also sponsored by applied across the isolating distances where devices are drawn into a test or various IEEE disconnect position. ratings. It is important to realize that if service conditions of which exceed the dielectric ratings of equivalent 7.ieee . IEEE C37.o rg /ias From IEEE 62271-1. in some cases.3 38-kV class and the IEC 36-kV Series class at higher insulation levels II (kV) are comparable. equipment selected for 2. p. IEEE C37.6 7. 25. Sec. One difference between the relevant IEC and IEEE standards is that the IEC standards identify two levels of impulse withstand for each rated voltage. and 2) the switchgear-spe. The voltage ratings can then be tested against IEEE working phase to ground (earth).6-kV requirements but align well with the IEC tude.5-kV I (kV) applications.20. For use at common voltages in North America. the ANSI IEC 8.16-kV applications and capability under a variety of test conditions.and IEC offers a 24-kV rating.or 15-kV-class equipment. 6].1 [14]. not the MV CB used in MC equipment discussed in this article).kets. Sec. IEC 62271-200 refers to –1 for these ratings.below rated values during qualifying tests. 4.7 [13].25 15 15.3. 17]. there are small differences in the dielectric test levels between the various ratings when using the higher of ings applicable for equipment rated at 52 kV and lower. IEEE (kV) 4. This article will only discuss rat. alti. At 27. When [9]. phase to grOUPS phase. the build-up of dirt. the two choices available at these ratings in IEC equipment Rated Insulation Levels (Table 3). these voltages are described as “the upper limit of the highest voltage of systems for which the switchgear is intended.is rated per the 4.5 25.However. For applications at 21 kV. The dielectric ratings for both of these are very simitemperature cycling can affect insulation performance. There is one noticeable difference in the test requirements between the two sets of standards. p. However. the available withstand voltage for testing does define preferred AR ratings for current should be evaluated. At 6. Another difference is that the IEC and time: equal to short circuit withstand for current standards allow 3% tolerance around test parameters.2. The dielectric requirements ning impulse (U p ). summarized in Table 1.users implement 8.8 kV.2-kV-class requirements. IEEE covers arc-resistant (AR) switchgear testing in a specifying or accepting IEC equipment in lieu of IEEE separate document. IEEE offers Lack of maintenance. the rated insulation levels may be affected. IEEE C37. cumulative effect 15-kV-class equipment. 5] and 0. Table 1. and across the switching device. lar. are written by and power frequency (U d ). or ment. These exceed tions include specific ranges of temperature. 500 40. IEEE C37. the manufacturer should be consulted if there is doubt on how to apply.6 39. Other rated current values such as short-circuit interrupting current are also from the R10 series. b IEC 10 11 23 46 Isolating Gap ANSI 6 a.6 2 2. Rated Continuous Current (Normal) Preferred ratings are in bold.3 kV 4.20. INDOOR. 22 50.250 1.2 8.000 20.3 8 10 12. The values in this series are listed in Table 4.76 Impulse Withstand U p (kV Peak) Common ANSI 8 IEC 9 20 40 60 66 40 60 95 95 75 95 95 125 125 137.5 3.000 5.5 24 27 36 34.000 63. The rated current is the current that conductors within the equipment are able to carry continuously without any parts of the equipment exceeding allowable temperature rise or allowable maximum temperature while the equipment is operated within normal service conditions. S1 CBs.5 40 50 63 80 102 100 125 160 200 250 315 400 500 630 800 103 1.25 12.9 kV Rated Voltage V or U r (kV rms) ANSI 2 IEC (SI) 3 3.15 4 5 6.000 25. For example.8 kV 15 17.000 50. The rated current and temperature rise are integrally related. IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www. The relay timing may be in milliseconds or cycles.000 2. specifically the 104 columns. higher frequencies may negatively impact temperature rise. R10 NUMBER SERIES USED TO DERIVE VARIOUS IEC CURRENT RATINGS. The first column is the R10 series.6 38 50 45 60 66 70 80 88 36 36 21 kV 21 kV.5 104.000 80.600 2.150 4. TABLe 4. and 60 Hz. 13. When converting from cycles to milliseconds.000 6.16 kV 6. and lower frequencies my impact peak current related ratings.5 16 20 25 31.500 16. may imply changes in the device capabilities.ieee. b IEC 7 12 20. The ratings are created by multiplying the R10 series by ten.5 kV 38 a b NA Application Voltages Column 1 2.000 12. EQUIPMENT VOLTAGE CLASSES AND ASSOCIATED DIELECTRIC RATINGS.5 145 170 150 165 165 195 104. However. or the opposite.000 Application at 50 Hz based on 60-Hz ratings. R10 Number Series.000 104 10.6 4. raised to a whole . IEC 60060 101 1 1.9 20 23 39.300 8.25 1.500 3. IEEE C37.47 kV. Power Frequency Withstand U d (kV) Common ANSI 4 IEC 5 10 19 7. 27 kV 60 80 Test not required if equipment has grounded metal shutters.000 1.5 85 110 110 145 46 70 Isolating Gap ANSIa.000 31.2 and C37.or g/ia s 110% of common voltage withstand.3 base all ratings and test criteria on 60 Hz only.100. with each number approximately 25–28% larger than the previous. the ratings used to evaluate application should be based on the actual application frequency or adjusted based on manufacturer recommendations. IEC 62271-1 uses the IEC 60059 R10 series of values.1 identifies 50 and 60 Hz as preferred.20. Whenever possible. the appropriate period should be used.TABLE 3. 25 15 1.000. When a specific standard describes different requirements than the “common requirements” the identified requirements take precedence. Rated Interrupting Current ( I sc ).200.000 1.20. 2. 2.20.000.5 82 79 ings may be seen in C37.000 4. The interrupting time for the CBs may be three or five 60-Hz cycles. Equipment/ Device IEC Switchgear CBs ME switchgear IEEE MC switchgear CBs Rating in rms A.o rg /ias Rated Continuous Ur kV rms Current ( I r ) A rms 4. Table 3. 2.200. as specified applications than is typical for low-voltage applications.000 50 130 125 that the equipment can carry for a specified period of time under pre1.  IEEE C37. The stanHz changes the peak current that the CB experiences dard time constant (L/R) is 45 ms in both standards with during fault conditions.3 has the same 65 °C requirement. 4. 75. 2. 2. 2.standards. Rated Peak-Withstand Current ( I p ). 3.000 25 65 63 the short time withstand currents may be selected from the R10 series 38 1. 2.000.000.000.000.5 63 79 The rated short-time withstand cur1. Rated Short-Time Withstand Current ( I k ).000 C37.000 A may be fan assisted (cooled). are the same. In the case of continuous current ratings.000 62271-1-2007 630 1.5 40 82 104 130 164 104 52 65 82 79 100 125 158 100 50 I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w. 4.000. The maximum permissible trip.000.250 1. Short circuit cur.ieee . 4]. The allowed temperature rise is based on a normal service condition of 40 °C ambient in both sets of standards.000 1. That difference is small and is the IEC standards identifying longer special constants of shown in Table 6.60 Hz 50 Hz rent ( I k ) kA rms 2.6X 2. 1. PREFERRED CONTINUOUS CURRENT RATINGS FOR IEC AND IEEE CB.000. 2. 3.200.000 C37.000 3.200.250 1. Normal Service Conditions Standard 630 1.000.600 2.000. PREFERRED CURRENT RATINGS (S1 CB).200.5X 31. Application at 50 versus 60 for special application with high X/R ratios. with the only difference being driven by the rent values for the associated IEEE preferred voltage and application frequency and longer dc time constants used continuous current ratings. p.200.600 2. 4. IEC standards allow any number in the R10 series to be used. 4.000 40 20 25 31.000 63 8. 3. C37.100. 4. The peak-withstand current for IEC and IEEE standards is essentially the same. The preferred ratings for IEC and IEEE equipment and CBs are shown in Table 5. 4. 2. kA Circuit and Short-Time Cur.76 1.000. 3.200.2 limits temperature rise in bolted connections to 65 °C above ambient [9.000 1.200 16 42 40 and behavior.Rated Duration of Short Circuit ( t k ) rents are made up of a symmetrical rms component and a The time that the switchgear or CB can carry a current dc component (dc offset) that is more substantial in MV equal to its rated short-time withstand current is called 23 . 3.150 4. and Rated Close and Latch Current (Rated Short-Circuit Making Current in IEC Terms) TABLE 5.000 31.20. by the manufacturer.000 40 104 100 rent is the maximum rms current 1.2-1999 2.200 2. 3. preferred rat1.000.200.000. 2. 2.20.000 3. Table 1.000 63 164 158 scribed “normal” conditions of use 27 1.200 16 42 40 of numbers. 2.200.000 50 1.000 4.000 62271-1-2007 600 1.1 and IEC 62271-1 are substantially harmonized and may be considered relatively equal when similar materials and equipment technology are compared.200.000 40 104 100 interrupting amperes and rated short-time current are the same in this table.  9] versus the 75 °C that the harmonized “Common Requirement” standards allow.000 3. the exponent may be two or three.150 4. 3. and 120 ms.200. Rated short-circuit 1.3-2001 2. 3.  However. 2. 1. Within IEC standards. Rated Closing and Rated ShortLatching A ( I p ). p. 3. 2. I p and rated close and latch current 60.200. IEEE C37.000 C37.000 3.06-2009 [7.The degree of dc offset is the same for IEC and IEEE ping time delay is 2 s.200 1.integer power.06-2009 TABLe 6.000.200. Table 6 shows the preferred cur. Larger device ratings such as 4. 2.000 1.000.200.000 1.200.000 25 65 63 For IEEE standards.200 1. 3. This is similar within North American standards to the performance provided by a molded case CB with integral tripping or any CB with override protection. Table 18. 100–90 V. (1) Per IEEE C37/20.2. IEEE Note 2—C37. This is also addressed in IEC 62271-1 Section 3. hence. Rated Supply Voltage ( U a ) and Rated Supply Frequency. provided that when connected in a circuit the CB shall be able to carry the prospective current for the maximum  time  the  integral  trip could take to operate.2.TABLe 7.4. The control power tolerances are generally 85–110% for IEC devices. and CBs with self-contained dc control also have different ratings.06.ieee. p. Within IEEE S2. Whenever applying this type of CB. and 3 s.118. The CB provides its own protection and. where a definition of self-tripping is provided as “any CB that is tripped by current in the main circuit without the need for auxiliary power” [22. IEC Vac 380/220 230 400/230 415/240 IEEE and IEC Vac 120 IEC Tolerance Expected 102–132 323/187–418/242 196–253 340/196–440/253 353/204–204/264 IEEE Tolerance Expected 104–127 Auxilliary devices 208–254 (1) 180Y/104–220Y/127 208–254 (1) (1) and functions shall operate up to the stated tolerances 240 480 IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www. 38 identifies slightly lower dc V for S2 outdoor CB (38–>36 V. 24 the rated duration of short circuit in IEC and IEEE standards. it does not need to specify a time limit to guide external relay application. it is incumbent on the system designer to understand the self-imposed time limitation this type of CB may have and what the effect will be on expected coordination (discrimination). 200–>180 V). specified differently for tripping versus other for IEEE.or g/ia s 204–264 408–528 177/102–229/132 204–264 408–528 408/235–528/305 510/295–660/382 208/120 240D 480D 480/277 600/347 Source: IEC 62271-1-2007 & C37. although the sensor locations may vary and may not be integral to the CB mechanism as they are in lowvoltage CBs. Sec. CBs with integral trip capabilities are available for North American markets as well. CBs have different ratings. Table 7 provides a detailed list . IEC 62271-100 adds that self-tripping CBs need not specify a value for t k . for IEEE it is 2 s. 33. CONTROL POWER PREFERENCES.1-200.8.5. 7. for Secondary Devices The rated values for frequency in  both standards are dc: 50 Hz and 60 Hz. the IEC standards allow other values to be used. >254 Vac and >280 Vdc control or instrument voltage is not allowed. p. The standard value for IEC standards is 1 s. p. Expected Supply Tolerance IEC and IEEE IEC Vdc IEEE and IEC Vdc 24 48 60 110 or 125 220 or 250 187 242 200–280 140–280 85% 20 41 51 94 110% 26 53 66 121 100–140 70–140 38–56 IEEE Closing and Auxilliary Tripping 14–28 28–56 IEC Closing and Auxilliary Tripping 20–26 41–53 51–66 94–121 106–138 187–242 213–275 17–26 34–53 42–66 77–121 88–138 154–242 175–275 IEEE Note 1— Equipment having self–contained dc control sources shall operate over the range of 85–115% of nominal voltage and the table above shall not apply. 28]. 2. However.100. The preferred values are 0. either defined as Open-t-Close-Open-t'-Close Open or Close-Open-t''-Close-Open. Devices that employ stored energy mechanisms for operation shall have a charged/ discharged status indication. 5]. The electrically operated devices are rated with a close-and-latch capability and may or may not have an open or interruption capability. If an interruption capability is required. I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w. with the following t values: t     = 300 ms t' = 3 min t'' = 15 s. or overhead cable connections are required. The device must have position indication that is fully visible when installed in the switchgear [12. and expected operated range for auxiliary devices and functions.04b-2008 [6].20. Test ports are not required by standard. alternatively 15 or 60 s for CB intended  for rapid reclosing t'' = 15 s for CB not intended for rapid reclosing.o rg /ias 25 . The different standards reflect common secondary control voltages used within the various markets as well as the different tolerance allowances. the load circuit.011-2005 IEEE Application Guide for Transient Recovery Voltage for ac High-Voltage Circuit Breakers. Sec. The devices must also have interlocks that prevent them from being racked-in or rackedout in the closed position.000 V. the control power voltage must remain within the expected tolerance. Typical S1-type indoor CBs (Figure 1) used in industrial and commercial applications have less demanding needs. these requirements are different from those imposed on reclosers. User-defined interlocks to ensure that the G&T devices are operated under proper system topology conditions are normal but should be carefully specified. and as in any CB control system. Part of the system design process is to identify the interlock sequence that is needed for proper system interlocking. Devices with six terminals will have a way to select which three are grounded.of preferred voltages. Sec.ieee . The selection is made when the device is “not” installed in the gear. 3 and 4.. Table 8 is a summary of the various CB types and the main standard references. Shutters protecting the potentially energized front terminals shall be interlocked with the grounding terminal mechanism. Most vacuum CBs in industry today meet the rapid reclosing requirements.06-2009 [7]. significant capacitor switching. even under serious fault conditions [40]. These devices may be inserted into a CB cubicle and used to effectively ground and short circuit either the main bus in the switchgear or the load side connections of a switchgear cubicle. A power-operated G&T device shall have a colored position indication clearly stating if the device is closed-grounded. ▪▪ ▪ ▪▪ ▪ ▪▪ ▪ ▪ ▪ ▪▪ ▪ Classes of CBs and Special Applications The IEC 62271-100 [22. Transient Recovery Voltage Transient recovery voltage (TRV) is the voltage impressed across a switching element’s contacts by the current interruption process interacting with the source and load circuit impedances and available power. pp. the user must specify it. as defined within IEC 60815. Operating sequence is similar in both standards. Devices may be provided with three or six rear terminals. The interested reader is encouraged to also read IEEE C37. Description of Transient Recovery Voltage for Harmonization with IEC 62271-100 [22] and C37. resulting in IEEE C37. Many G&T devices will include test ports for access to measure voltage.e. The IEC standards define t and t' as follows: t = 3 min for CB not intended for rapid auto reclosing  t = 300 ms for CB intended for rapid reclosing  t' = 3 min. i. which can only be operated outside the equipment.2. they must have barriers to prevent inadvertent access. 29] standard specifically addresses several types of CBs above 1. The differences are not significant. expected supply tolerances. G&T devices must have mechanical interlocks so they cannot be installed in higher-rated CB cubicles that exceed the G&T device’s rating. This is a complex subject of significant importance for distribution CBs (S2-type CBs) and breakers in particularly stressful applications where out-of-phase conditions. p. particularly for S1 CBs below 100 kV. which has greatly incorporated the IEC methodology. A power-operated G&T may have a user selector switch.6-2007 [12]. or open-ungrounded. They must be applied so their close-and-latch capability matches or exceeds system requirements. The IEEE WG has significantly aligned TRV standards with IEC requirements over the last decade. to select which terminals are  grounded. but if provided. IEEE standards have equivalent ratings for most of these. During the operation of a device. IEEE switchgear typically relies on accessory devices called ground and test (G&T) devices defined in C37. Amendment 2: To Change the Maintenance Grounding— Earthing Switches Versus Ground and Test Devices Maintenance grounding accommodations provided by IEC switchgear versus IEEE switchgear vary.  IEEE uses the O-t-CO-t'-CO sequence for rapid auto reclosing and CO-t''-CO for CB not intended for rapid reclosing. Operating Sequence SPeciAl cONdiTiONS within the IEC STANdArd Are levels III and IV. 6. The G&T devices may be manually or electrically operated. it is imperative that control power be within tolerances and highly reliable to ensure that devices operate when called upon to do so. However. 28. Manually operated devices do not carry a close-andlatch rating and must be operated on a system already known to be de-energized. Standard classification. CB with “basic” electrical endurance Sec. 3.100.06 compliant CB must meet 10.2. 163.4. pp. 40 Limited reclosing application discussed for indoor and outdoor CBs intended for external relaying control. CB intended for line (overhead) pro3. IEC Definition S1 S2 62271100 2007 IEEE Definition Equivalent defined similarly in IEEE C37-06. ance” type tested for 2. No similar classification. 3. 4. as C0 (general purpose). 3. per Table 4 (<100 kV). Required for auto reclosing distri.ieee.116 Sec. CB TYPE DESCRIPTIONS AND REFERENCES. 11–18 CB intended for cable system protec. pp. and other factors. IEEE defines an optional S1 CB pp.000 operations with no maintenance. 3. 26 . C37.06 compliant devices except with respect to control power and trip control source (relaying).Sec.4. All C37. All 35–37 C37.114 Sec. C1 CB with “low” probability of restrike during capacitive current breaking as demonstrated by specific type tests CB with “very low” probability of restrike during capacitive current breaking as demonstrated by specific type tests Sec. 9.000 operations with minimal maintenance. 3.4.112.113 bution CB rated # 52 kV.1. 35 and 36 E2 (1) Sec 3. Reclosers with dedicated integral controls intended for network applications defined in C37. optional for those not required to perform auto reclosing Sec. typical commercial and industrial 3. Table 8.or g/ia s M1 CB with “normal mechanical endurSec. IEEE C37. 11.8. 4–10 Sec.000 operations requiring only limited maintenance during operations Sec.60. 6. pp.2 7 a dedicated standard to be substantially different than standard C37. Similarly for S2 CB. typical of utility applications and very large distribution systems. pp.Sec. tion. 4. 164. earthing.06 but not specifically defined by Sec.5kV and higher have different requirements.115 C2 IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www.TABLe 8.118 SelfCB that is tripped by a current in the tripping main circuit without the aid of any form of auxiliary power (commonly done with low-voltage CB) Inductive switching Capacitor bypass switching CB for switching of highly inductive loads CB for use as bypass switches for line series capacitors 62271-110 62271-109 and 60143-2 Notes—IEC: (1) Number of operating sequences varies based on % short circuit current.120 tection. 16–18 as C1 or C2 (formerly definite purpose).06 compliant CB must meet 2.06 2009 Sec. pp. M2 CB with “extended mechanical endur.4. p. Equivalent defined similarly in IEEE C37-06. pp.4. 8–10 and Table 8. Mentioned within C37.06-2009. C1 and C2 CB have greater capacitive inrush capability. 9.119 Sec.4. See Table IEC 62271-100. CB with “extended” electrical endurance. Also similarly referred to in IEEE C37. Sec. C37.117 ance” type tested for 10.4.06. 5. Sec.000 operations 3.06-2009 defines S1 CB Table 4. S2 CB at 15.112 E1 Standard CB as defined in C37. 6.4. 3. there are two major categories. can be opened with the bus bars energized.103. the tests include 500 insertions/removals from the cubicle and 250 operations with maintenance allowed at 125 operations.. respectively. is the most commonly offered by manufacturers. and Service Continuity IEEE standards divide indoor-type MV switchgear into two types. E0.20. tests are 500 insertions and removals from a cubicle and 500 open/ close operations including five operations each at maximum and minimum control voltage. When implementing a stationary CB with this degree of compartmentalization it is implied that the CB requires little maintenance when used as expected.103. It is interesting to note that the strictest IEC definition for compartmentalization and isolation of the various devices and sections may be achieved with or without a drawout element. the interlocks must also be supplied and coordinated with the system source devices to ensure a live bus is never grounded and proper sequencing is observed. Within IEC standards. Opening of accessible high-voltage compartments in a functional unit is possible while other functional units of the same section are energized. However.3. 8. as well as proper partitioning. Within the IEC definition. 1 ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ cables) to the functional unit being accessed may be kept energized. E1. In industrial applications. other than the main bus bar compartment. [25] is the standard for earthing devices. E0. the third for isolation only. Sec. LSC2. each rated at zero. 54] and show various possible CB. For manual devices. Routine maintenance is allowed after 250 operations with no parts replacement. pp. LSC2 (family): Intended to allow maximum continuity  of service. and E2. The CB-earthing switch combination must have interlocks to ensure that the grounding switch is never closed while the corresponding CB is closed. IEC definitions are as follows: LSC1: Not intended for maximum service continuity  during the opening of any accessible compartment and may require complete disconnection from sources before opening any compartment doors. LSC2: Minimum requirement is that it is possi ble to open the connection compartment while keeping the bus bars live. This standard covers a wide range of applications including high-voltage distribution line applications.6. This implies that there also is a point of disconnection.o rg /ias 27 . Switches used in series with CBs often have three positions. Figures 2–4 are from IEC 62271-200 [35.20. MC defined by IEEE C37. Earthing and isolation switches fulfill the role of the drawout function. or can be maintained in situ. These are not the only possible variations. There may or may not be other accessible high-voltage compartments. If there are multiple sources. p. shutter function and grounding function. the high-voltage connections (e.ieee . Users may specify CBs without earthing switches and may rely on earthing trucks similar to those commonly used in ANSI applications or may use earthing switches for CB and feeder cable earthing and a separate truck for main bus earthing. The lowest rating. they are not commonly used. 8. IEC relies on the service continuity definitions provided in IEC 62271200-2011 [35. The normal IEEE expectation of having CB elements easily removable for maintenance or replacement is not easily achieved without drawout elements. LSC2A. electrical interlocks may be required to enforce proper sequencing. different close and latch ratings are possible. with LSC2 divided into three subcategories. drawout equipment of the LSC2B type is most common. None of the definitions limit the CB to a stationary or draw-out configuration. nor the location and type of earthing switches. In the case of a separate permanently installed grounding switch. and isolation or drawout connections combinations under the standards definitions. in IEC terms) switches are often fixed mounted in the equipment and may be provided on a per-circuit basis within each CB assembly. IEC earthing devices are rated for 2.Design endurance tests are made per Section 7 of C37. I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w. Switchgear Type: MC. 52–54]. Note that the definitions above do not specify drawout or stationary. Switchgear Bus CB Line-Side Earthing Switch CB Contacts Interlock System to Ensure Main Bus Is Not Grounded CB Load-Side Earthing Switch Load-Side Cable Connections A simplified IEC CB symbol as may be used in MV indoor switchgear. and LSC2B. ME. is relatively easy to remove. LSC1 and LSC2.20. Earthing switches may have two or three positions.2 and ME switchgear defined by IEEE C37. IEC 62271-102-2003 [24]. between the accessed compartment and the high-voltage connections. two. Sec. section barriers (compartmentalization). or five times carrying capacity. Though removable G&T devices are available for enclosed switchgear. For electrically operated G&T devices.3.g. LSC2A: All accessible high-voltage compart ments. L SC2B: In addition to the requirements of  LSC2A. grounding (earthing. earthing switch.000 operations and have withstand ratings to match the CB capabilities. (b) Figure 102-LSC2—Stationary CB with compartmentalization. (a) Figure 101-LSC1— Stationary CB without compartmentalization.103. 11].109. Both types shall provide IP2X protection per IEC 62271-1 [21.104. [35. No compartment may be opened with bus energized. C37. (a) Figure 105-LSC2B—Stationary CB with full compartmentalization.3. 55–59] lays out the basic IEC requirements. The market traditionally served by switchgear meeting IEEE standards has had two clearly differentiated  products available.1– 8. The IEC standards have considered this subject for several decades.1. It would be reasonable to see significant influence from the corresponding IEC standards. This does allow the CB and cable compartment to be opened with energized bus. However. Bus Bar Compartment IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www.3. CB and Cable Connections in 1 Compartment Isolating and Earthing Switch Isolating and Earthing Switch CB Compartment Cable Connection Compartment (b) Cable Connection and CB Compartment (a) CB Compartment Cable Connection Compartment (b) (a) 2 3 The LSC1 and basic LSC2 section layouts are described in IEC 62271-200. which has benefits for the user as maintenance and system design practices can become more similar. AR Ratings Arc resistance in switchgear is a subject with increased levels of attention in IEEE markets over the last ten years. Sec. (a) Figure 103-LSC2—Stationary CB with partial compartmentalization. pp. (b) Figure 105-LSC2B—Drawout CB with full compartmentalization. Typical of ring main units (RMU) designs. grounding of switch and load capability. providing design and manufacturing efficiencies that should result in lower costs for all. equipment that has been 28 The IEC standard (62271-200) also defines partitions as PI (nonmetallic). This does not allow the CB compartment to be opened with energized bus. Sec.103. 8. 3. In IEC standards. This trend has the effect of bringing the equipment platforms closer to each other. MC switchgear based around drawout vacuum CBs and ME switchgear based around fused switches. IEC 62271-200. This does allow the CB/cable compartment to be opened with live bus. Section 8.104. Section 8.4 is for the switches used in the ME switchgear.ieee.103.20.3 is in the process of revision today to address the use of fixed and drawout CBs. This does allow the CB and cable compartment to be opened with energized bus. can be more easily designed and manufactured for both markets. Sec 3. 55]. The LSC2 with partial compartmentalization and LSC2A section layouts as described in IEC 62271-200.or g/ia s Bus Bar Compartment Drawout Connection = Isolating and Earthing Switch (1 of 2) CB Compartment CB Compartment Cable Connection Compartment (a) Cable Connection Compartment (b) 4 LSC2B sections with stationary or with drawout CB.6. ers (PM) and shutters (if intended as earthed) shall be earthed so that no electric field is present in the un-energized open compartment. most importantly. IEEE C37. Metallic barri- . the use of stationary CBs within equipment meeting ME standards. IEC 62271-200 [35. The advantages for the manufacturers are that similar components. (b) Figure 104-LSC2A—Stationary CB with compartmentalization. Future versions of ME switchgear will incorporate CBs installed and meeting this new revision to the standard. and eventually equipment.3. This does allow the CB and cable compartment to be opened with energized bus. 11] or PM (metallic) [35. p. Table 7. Conductors passing through the partitions shall be provided with suitable bushings or insulation. Section 8.109. p. but the cable compartment may be opened.2. p. various products demonstrating an IEC influence have appeared in the market.20. in the last decade.Isolating and Earthing Switch Bus Bar Compartment Bus Bar Compartment Bus Bar Compartment Isolating and Earthing Switch CB Bus Bar. Personnel training.3. Overvoltage Surge protection and adequate insulation coordination.TABLe 9.104. delayed reopening. vermin. CAUSES. are maintained. Regular programmed maintenance as needed.104. Dielectric tests on site. I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w. Measures to ensure that specified service conditions ingress of dust. in relation to internal arc. and earthing switches Bolted connections and contacts Maloperation Examples of Possible Preventive Measures Selection of appropriate materials and use of adequate dimensions. p.” Under general comments in Section 8. The standard also states that the faults have been shown to occur more in some locations inside the switchgear than in others. Sec. LOCATION. 56. Use of plating. TABLE 102.1. are met in the event of internal arc as demonstrated by type tests. Limiting access via compartmentalization. should be governed by a procedure to achieve a level of tolerable risk. for protection of persons. A table of locations and probable causes is provided in the standard and summarized in Table 9. Location Where Internal Arc Faults Are Most Likely to Occur Connection compartments Possible Causes of Internal Arc Faults Inadequate design Faulty installation Insulation failure Disconnectors. Therefore. Encapsulation where possible. According to ISO/IEC Guide 51.132. 14] as “metal-enclosed switchgear and control gear for which prescribed criteria. Avoid short circuits by using covers. Proper torque. Partial discharge testing. Worksmanship supervision. tested to sustain an internal arcing fault is referred to as “internal arc classified” (IAC) and defined [35. SEC. or differential protection application of fuses in combination with switching  devices to limit the let-through current and fault duration ▪▪ ▪▪ 29 . Furthermore. Training. 8. Training. the IEC standard states: When selecting a metal-enclosed switchgear and control gear. Correct torque. Worksmanship supervision. Use of corrosion-inhibiting coating and/or greases. Dielectric testing/maintenance. This protection is achieved by reducing the risk to a tolerable level. moisture. the selection of adequate equipment. Corrosion Faulty assembly Rack-in/out due to damage or distortion of the plug-in contact and/or shutters Instrument transformers Ferro resonance Short circuit on lowvoltage side of VTs CBs All locations Insufficient maintenance Human error Aging Suitable design of the circuit. Use of gas-filled compartments. Checking of worksmanship by suitable means. risk is the combination of the probability of occurrence of a harm and the severity of the harm. and other means.o rg /ias Pollution. where applicable. This procedure is based on the assumption that the user has a role to play in the risk reduction. adequate locking means. Supplemental heating to prevent condensation. switches.ieee . the possibility of the occurrence of internal arc faults should be properly addressed. P. with the aim of providing an acceptable protection level for operators and. Avoiding crossed cables. IEC 62271-200. Worksmanship supervision. low-voltage fuses. heat. AND EXAMPLES OF MEASURES TO DECREASE THE PROBABILITY OF INTERNAL ARC FAULTS. the IEC standard directly addresses supplementary protective measures such as rapid fault clearing based on fault detection via light. Embedding energized parts in insulation. for the general public. etc. Interlocks. Independent manual operation. 3. Sufficient device-making capacity.  pressure. the time it was tested for and the sides that passed the test.20. It is not intended for protection of personnel under maintenance conditions nor for protecting service continuity [35. Users must identify the need based on how the system on which the switchgear will be applied is grounded. This should lead the user to consider the recommendations in the IEC standard and C37. The classifications may be described as follows: general: classification IAC  accessibility: A. In the case where the switchgear design is such that only single phase arcing fault can occur. Designation of the gear is based on the accessibility that it is intended for. includ ing that of the general public accessibility type C: restricted by installation out of  reach and above a general public area. 0. IEEE C37. 2] describes a similar intention. and isolated neutral (floating) systems need 87%.4 goes on further to state that it is not possible to test equipment for all possible conditions that can produce an internal arcing fault.2 accessibility type A: restricted to authorized person nel only accessibility type B: unrestricted accessibility. p. Manufacturers may offer varying ratings.7-2007 [13] IAC Classification. especially liquid-filled components or other materials internal to components that may fail. and L. Not all equipment will require the same operating or  maintenance procedures. rear.2.” includes some important points such as that the guide does not address all effects that constitute risk. Passing the basic tests for either type of accessibility allows the switchgear to be labeled as Type 1A or Type 2A. and some may require procedures that invalidate an AR/IAC rating. Sec. Sec. However the IEEE guide provides guidance on how to qualify those claims by test. for 0. p. Successful passing of this second set of criteria allows the equipment to be labeled 1B or 2B. R. 57]. Section 1.5 kA.1. Not all switchgear and control gear is of withdraw able design. IEEE Guide for Testing Metal-Enclosed Switchgear Rated up to 38 kV for Internal Arcing Faults. with a successful IAC test for all four sides at 12 kA. ast elimination of the arc by diverting it to a metal▪▪flic short circuit crowbar by means of fast-sensing and fast-closing devices emote operation instead of operation in front of the ▪▪rswitchgear and control gear p  ressure-relief device ▪ ▪ t  ransfer of the withdrawable part to or from the ser▪▪vice position only when the front door is closed. The IEC standard also points out certain considerations the user should take into account.ieee. or the test position. the earthing position. 4. Although the above considerations are based on common IEC equipment practices. Not all switchgear and control gear is fitted with a  door that can be closed when in the service/connected position. ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ (I A) . IEC 62271-200 30 Classification under IEC and IEEE standards is intended for protection of personnel under normal operating conditions. Not all equipment in an electrical room may be AR/  IAC. back.20. Not all circuits and devices that may require mainte nance or verification will be in compartments free from arc hazard. It should be noted that the standard does not specify a particular current value nor a particular time period.2.7-2007. Sec. not how to achieve them or what they must be. not a standard. Impedance and solidly grounded systems require 100% phase-to-earth arc resistance.2. it is a guide for testing. and hence a hazard may exist regardless if one piece of equipment is so rated.3. 5] identifies two types by accessibility: Type 1—switchgear with AR designs or features at  the freely accessible front of the equipment only Type 2—switchgear with AR designs or features at  the freely accessible exterior (front. Section  4.104. and the suggested values for time are 0.5 s. and 1 s. IEEE C37. 1. Where the manufacturer only states a single value of three-phase IAC rating the single-phase rating shall be 87%.2. Equipment certified for unrestricted accessibility.6. The guide also does not address the failure of components. or C per 62271-200. such as release of toxic materials or excessive sound pressure. although the current values must be taken from the R10 table previously described.7 [13.101. A third criterion is described in the annex for suffix C designation. B.5 s would be designated IAC BFLR 12. Single-phase values ( I Ae ) may be used where construction prevents three-phase arcs as demonstrated during the internal arc test. p.5.or g/ia s closed-door drawout. Single-phase values may be 87 or 100% of the three-phase current ▪ ▪▪ ▪ ▪▪ ▪▪ ▪▪ The defining IEEE document for arc resistance is IEEE C37. they can easily be identified with parallels viable regardless of the equipment standards such as the following. The IEEE standard [35. only a single phase arc rating needs to be provided. Sides are indicated by letters: F. The minimum approach distance to be stated by the manufacturer and the minimum installation height is the declared minimum approach distance plus 2 m.20.7 for supplementary protection and other application considerations regardless of which standards the applied equipment meets.20. As listed in the title to this section. 0. and sides) of the equipment only. lateral. An assembly proven by these tests cannot guarantee to withstand all internal arcing faults that may occur in service. Annex AA defines additional tests that allow a user to open a compartment door for compartments identified as low voltage control or instrumentation only. 8. Section 1. Arc-fault current is expressed in (kA) and arc test duration in seconds. front. Suffix C indicates that the ▪▪ ▪▪ .2 and Annex AA.IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www.2. the fault current it was tested with. “Application of This Guide. even in AR/IAC rated equipment. Not all switchgear and control gear will be IAC  classifiable. The IEC standards do not have a specific designation for front only and front/sides/rear other than the individual listing of the qualified sides per test. Stationto realize that compartmentalized and that each comary CBs are more common in IEC partment is independently AR. Changes not normal. The adoption of this type of switchgear have been significantly harmonized. The responsibility for choosing the ferences is the ways that CBs are installed in equipment.34(A) [15.effect of an internal arc fault is confined Fully front-connected assemblies are only to the compartment where the more common in IEC equipment.connectivity. isolating switch. The complex physics and even more com. one of the main areas of dif. 29 [35].tion provided by a CB in the drawn out position or visible ground current.National Electrical Code’s (NEC’s) requirement for visible plex testing of characteristics like TRV dictate that com. size and even cost perspective. These designs may be very attractive from the tection resides.out of the cubicle for fast replacement. pp.This requirement is fulfilled by MC equipment’s drawout dard simply recognizes that we all must deal with the CBs or ME. Plus.between them. and testing. “To properly apply current transformers (CTs) mounted affected. the user will often need to rely on position indication provided by a common shaft or other mechanism that provides Conclusion feedback on the status of the CB. the combination can yield not be easy.2.o rg /ias 31 . the switchgear. This requires lation and the electrical protection the CBs to be drawn out to access the devices must be coordinated with the CTs and also requires the CB cell conratings of the arc-resistant switchgear. However. However.1(3)]. Additional requirements in the final product targets.” nections to allow sufficient space to This is true regardless if the gear is based on IEC or IEEE mount multiple CTs in one cubicle. both the physical instalwithin the CB cubicles.S. Sec. However. A more the standards will not achieve complete harmonization in substantial barrier to the adoption of IEC practices is the the near future. For an IEC-style fixed mounted CB. North American 200. Currently. test in the same laboratories. is consistent with ton panels ascertain that excessive heat or hot materials do the reliability requirements of the system. IT IS IMPOrTANT fault originally occurs. on all sides but has been tested for the expected in C37. Type C suffix although the standards do not directly implies that the equipment is fully promulgate that construction. tion fully clear the fault within that time. But those practices have been in use for many years in further harmonize the standards. 70–87. For the main secThe IEC practice of combining isolation switches with tion where the protection may be on the line side of a grounding switches in the CB section can take the place of transformer at a higher voltage. visible-blade knife-type switches. p.practices in both markets. it is likely that markets where IEC equipment is routinely used. with finer gradations equipment choices. due to its location or other are bringing that practice to the tradiconsiderations. current available. the user will need A difference in the AR tests is that the IEC uses 300 to determine if the complexity of having multiple devices mm and IEEE C37.20. 120. dardize that practice in North Amerthe rated The IEEE guide also includes an ica. which cannot be drawn cotton test panels and the equipment enclosure. The cot. and mon IEC practice of using shaft position or other less posioften use the same components or subassemblies regardless tive indication of device position does not normally meet of what standard the product shall meet or what market the requirements in the NEC.1 and mon standards facilitate the generation of common 230. 70–71 and pp.verification of isolation found in articles 225. But modern electronic relays proaccount that the equipment is only rated for a specific vide lower burden and are facilitating common CT amount of time. Harmonizing the stan. Comprotection without a sophisticated protection scheme may bined with a SF6 insulated tank.enough power from the CT’s iron to power electromagmize probability of a failure. but recent products introif service D (for type 1 only) is also described for duced in the North American market cONdiTiONS Are gear that. traditions and some NFPA 70E [38.7 requires 100 mm between the that form one integral assembly. bringing IEC and IEEE practices application section (Annex B) similar in closer together. Special attention should be paid to protection of very compact equipment that can be built for full-front the line side of the incoming compartment. differences in the standards still create distinctly different A user today has more choices. maintenance pracstandards currently being revised by the IEEE WGs will tices. respectively]. knowledge. Also. in a particular I E E E I ndu str y Appl ic ations Ma gazin e • Jan |Feb 2 014 • ww w. science. does not need to be AR tionally IEEE market. iNSUlATiON content to what is found in IEC 62271Traditionally. achieving sufficiently fast a drawout mechanism and a ground and test device.3 will further stansides that need the arc resistance. it should be taken into netic protective relays. The comsame physics problems. and Over the last decade. where that pro. North American not exit the enclosure. IEEE and IEC standards for MV and grounding switch assembly. A suffix equipment. Common IEC pracstandards.2. whereas the IEC tests are performed on an blade switch contacts viewable through an inspection winimpedance grounded system with limited ground fault dow in the switchgear. The IEEE equipment may require changes in U.20.ieee . the AR tests under IEEE are users are accustomed to the positive verification of separaperformed on a system that can deliver full phase-to. An important point is described in equipment relies heavily on doughnut levels may be B. and hence it is imperative that all protec. There is always a desire for the fastest possible tices have been to rely on bar CTs more often so as to get protection to minimize damage to the equipment and mini. optimum product for an application. 54-2002. NFPA Standard 70E.5 kV and Above. [14] IEEE Standard of Common Requirements for High Voltage Power Switchgear Rated Above 1000 V. 2011. [21] High-Voltage Switchgear and Controlgear—Part 1: Common Specifications. IEC Standard 62271-108. IEC Standard 62271-101. Jr. China. IEC Standard 62271-110. IEC Standard 62271-200.57-2003. no. PadMounted... NEMA ANSI Standard C37. 2009. 2008. IEC Standard 62271-111.09-1999. [24] High-Voltage Switchgear and Controlgear—Part 102: Alternating Current Disconnectors and Earthing Switches. India. R2006. Dry Vault. IEC Standard 62271-104. IEEE Standard C37. [3] D.region. IEEE Standard C37. 216–225. 1999. IEC Standard 62271-102-am1. [11] IEEE Standard for Indoor AC Switches (1 kV–38 kV) for Use in MetalEnclosed Switchgear. Bridger. Calgary. “Transient recovery voltages for high voltage circuit breakers. Valdes is a Senior Member of the IEEE. [8] Standard for Testing Procedures for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis. 2012. “Applying microprocessor-based protective relays in switchgear with AC control power. New York: Wiley. Ind. IEC Standard 62271-106. [6] IEEE Standard for Rating Structure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis Amendment 2: To Change the Description of Transient Recovery Voltage for Harmonization with IEC 62271-100.4-2001. IEC/TR Standard 62063.06-2009.20. 1. 2011. [18] Switchgear—Metal-Enclosed Interrupter Switchgear Assemblies—Conformance Testing. [15] National Electrical Code.” IEEE Trans. 2005. [27] High-Voltage Switchgear and Controlgear—Part 104: Alternating Current Switches for Rated Voltages of 52 kV and Above.or g/ia s [23] High-Voltage Switchgear and Controlgear—Part 101: Synthetic Testing. Applicat. [2] B. References IEEE In dustry A p plication s M ag az in e • Jan |F eb 2014 • www. Marcelo Valdes (marcelo.20. NFPA Standard 70. 1. 2005. Contactor-Based Controllers and Motor-Starters.” presented at the IEEE Mega Projects Workshop.20. 2010. [29] High-Voltage Switchgear and Controlgear—Part 106: Alternating Current Contactors. IEC Standard 62271103.7-2007. [4] L. vol. R2007. 2011. 2008. many detailed decisions are still required to procure the optimum equipment solution regardless of the standard referenced. Bridger.20. [34] High Voltage Switchgear and Controlgear—Part 111: Overhead. 1996.. IEC Standard 60721-2-4. [12] IEEE Standard 4. 2001. [25] Amendment 1—High-Voltage Switchgear and Controlgear—Part 102: Alternating Current Disconnectors and Earthing Switches. 2001. IEEE Standard C37. IEEE Standard C37.100. vol. 6. Jan.ieee. 2002. IEEE Standard C37. [13] IEEE Guide for testing metal-enclosed switchgear rated up to 38 kV for internal arcing faults. Applicat. vol. IEC Standard 60815-1. 2009. Shridhaval Sapre is with GE Industrial Solutions in Hyderabad.” IEEE Trans./Feb. [1] B. IEC Standard 62271-109. R2010. still falls on the user. [33] High-Voltage Switchgear and Controlgear—Part 110: Inductive Load Switching. [7] IEEE Standard Rating for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis-Preferred Ratings and Related Required Capabilities for Voltages Above 1. van der Sluis. Transients in Power Systems. IEC Standard 62271-100. 2011. [39] Classification of Environmental Conditions—Part 2-4: Environmental Conditions Appearing in Nature—Solar Radiation and Temperature. IEC Standard 62271-107. [20] High-Voltage Switchgear and Controlgear—The Use of Electronic and Associated Technologies in Auxiliary Equipment of Switchgear and Controlgear. IEEE Standard C37. pp. IEEE Standard C37. Regardless of the choice.58-2003. [40] G. IEC Standard 60071-2. NEMA ANSI Standard C37.04b-2008. [22] High-Voltage Switchgear and Controlgear—Part 100: Alternating Current Circuit-Breakers..1-2007. “Comparison of ANSI/IEEE and IEC requirements for metal-clad switchgear. “All amperes are not created equal: A comparison of current ratings of high-voltage circuit breakers rated according to ANSI and IEC standards. [5] IEEE Standard Rating Structure for AC High-Voltage Circuit Breakers . 1436–1443. AB. [26] High-Voltage Switchgear and Controlgear—Part 103: Switches for Rated Voltages Above 1 kV up to and Including 52 kV. Xuhui Ren is with GE Industrial Solutions in Shanghai. 2005.. [37] Insulation Coordination Part 2: Application Guide. [30] High-voltage Switchgear and Controlgear—Part 107: Alternating Current Fused Circuit-Switchers for Rated Voltages Above 1 Kv up to and Including 52 kV. Canada. [35] High-Voltage Switchgear and Control Gear—Part 200: AC MetalEnclosed Switchgear and Control Gear for Rated Voltages Above 1 kV and up to 52 kV. 195– 201. IEEE Standard C37.000 V. Jr. Information and General Principles.6-2007. This article first appeared as “IEC & IEEE Medium Voltage Distribution Equipment Standards: A Review and Analysis” at the 2012 IEEE IAS Petroleum and Chemical Industry Technical Conference. IEEE Standard C37. Ind. IEEE ANSI Standard C37. 2011. IEC Standard 62271-1. 32 . [17] Switchgear—Metal-Clad Switchgear Assemblies—Conformance Test Procedures. 1997. 2002. [31] High-Voltage Switchgear and Controlgear—Part 108: High-Voltage Alternating Current Disconnecting Circuit-Breakers for Rated Voltages of [email protected]. [36] Selection and Dimensioning of High-Voltage Insulators Intended for Use in Polluted Conditions—Part 1: Definitions. and Submersible Automatic Circuit Reclosers and Fault Interrupters For Alternating Current Systems up to 38 kV. Fox. 2008. 2005. 41. Oct.2-1999. Applicat. [16] Conformance Test Procedures for Indoor Alternating Current High-Voltage Circuit Breakers Applied as Removable Elements in Metal-Enclosed Switchgear Assemblies. [19] Indoor Medium Voltage Switches for Use in Metal-Enclosed Switchgear— Conformance Test Procedures. pp. [10] IEEE Standard for Metal-Enclosed Interrupter Switchgear./Feb. IEEE Standard C37. no. Jan. Acknowledgment The authors wish to thank Ted Olsen for his careful review and many valuable suggestions. 33.” IEEE Trans. R2010. 2008. 1993. Ind. Dufournet.55-1989. Marty Trivette. 29. 2011. Trivette and Meiners are Members of the IEEE. [9] IEEE Standard for Metal-Clad Switchgear. [28] High-Voltage Switchgear and Controlgear—Part 105: Alternating Current Switch-Fuse Combinations. pp.20. and it is the user that must become informed on the choices available. [38] Standard for Electrical Safety in the Workplace. no. H. IEC Standard 62271-105.com). Nov. R2010. IEC Standard 62271102.04-1999. and Steven Meiners are with GE Industrial Solutions in Plainville. IEEE Standard C37.76kV to 38kV Rated Ground and Test Devices. [32] High-Voltage Switchgear and Controlgear—Part 109: Alternating-Current Series Capacitor By-Pass Switches. Connecticut.–Dec.