Electrical Design Estimation and Costing10EE82 VTU Question Solution Unit-1 1.Define the estimating and mention the purpose of estimating and costing. (Jan-2016) Estimating is an art of assessment of quantities of different items and cost thereof to plan the amount required for executing a work before actually carrying out the work. OR Estimating means to determine the quantities of various items required to execute a job and to assets the cost of execution. 2.Write a short note on comparative statement. (Jan-2016) Bidding goods and services is important for several reasons. The bidding process: • allows "comparison shopping" for the best pricing and service • allows for an informed and objective choice among potential suppliers • encourages competition among suppliers • provides a standard for comparing price, quality, and service • provides a list of qualified suppliers for future bids • provides access to University business for suppliers The bid process begins with the development of a set of specifications or objectives. The Contract Administrator (CA) in conjunction with the requester must define the requirements exactly. Colleagues, technical personnel, trade manuals, and suppliers may be consulted for assistance in developing specifications. The requirements are then communicated to the selected suppliers by a Request for Quotation (RFQ) or a Request for Proposal (RFP). 3.Briefly explain the modes of tendering. (Jan-2016) Prepare Reasonable Cost Estimates Project cost estimating is not an exact science; however, estimators are expected to prepare reasonable project cost estimates that represent the cost to complete the project. These costs include those required not only for the contractor to construct Department of EEE, SJBIT Page 1 Electrical Design Estimation and Costing 10EE82 the project but, also includes the costs for the purchase of right of way, mitigation of environmental issues and any other costs that will be incurred to complete the project. Project alternatives and their associated cost estimates must be thoroughly compiled by diligently using all of the available data, modifying that data with good judgment and using past cost estimating experience so that the cost estimates can be used with confidence. Coordination between the project planning cost estimates, the project design cost estimates, and the specifications and policies that will be in place during the construction of the project is required. Cost Estimates are Not Static Cost estimates, in a sense, are never completed. They are not static, but have to be reviewed continually to keep them current. The Project Manager (PM) is responsible for keeping the project cost estimate up-to-date throughout the project development process, reviewing all project cost estimates and ensuring that the current project cost estimates are entered into the Project Management data base and a hard copy is in the project file. 4. What is estimating and what are the importance of the estimating and costing(Jun -2015) Electrical estimating is a process used by electricians, construction managers and engineers to determine the amount and cost of electricity required for a specific location or process. There are two general methods of creating accurate electrical estimates: computer software or manual calculations. Both methods have value, benefits and risks. Original electrical estimating software options were quite clumsy to use, but recent enhancements have vastly improved this tool for electrical estimation. Electrical estimating computer software has increased in popularity as it has improved in quality and performance. This tool is designed for use by electricians, architects and electrical engineers. There are different versions available for residential, commercial or prototype development. An estimating technique is an approach to predicting cost or revenue. Using a consistent methodology is important to achieve reliable and comparable results. Firms may have specific policies their personnel have to follow when making estimates to ensure that the approach will be similar no matter who prepares the estimate. This can help reduce problems associated with variances in methodology, like an offer from one mechanic in a shop of a very low price for service while another indicates the cost of a job will be much higher. Department of EEE, SJBIT Page 2 Electrical Design Estimation and Costing 10EE82 When preparing estimates, people can broadly divide them into detailed and approximate types. Approximate estimates offer a rough guess of the cost, based on similar projects, experience, and quick research. They can be helpful for getting a general idea of expenses before proceeding with a more detailed estimate. For people soliciting estimates, they can't be quoted as firm bids, but may provide a frame of reference. A homeowner looking for a new roof, for example, could ask for an approximate estimate from several contractors to learn more about the range of possible prices. 5.Explain the following:1)Electrical schedules 2)Catalogues 3)Purchase system 4)Market survey . (Jun -2015) Electrical Schedule: The electrical load schedule is an estimate of the instantaneous electrical loads operating in a facility, in terms of active, reactive and apparent power (measured in kW, kVAR and kVA respectively). The load schedule is usually categorised by switchboard or occasionally by subfacility / area. Catalogues: The main objective of a catalogue is to promote the products and services offered by your company. A catalogue layout properly designed must show your company's products or services arranged neatly, so that they can be easily recognized; and, at the same time, it must look attractive to improve your sales. In addition, the catalogue layout must be strategically arranged in order to give more importance to certain items or to make the catalogue look more eyecatching. Finally, the visual coherence on which a company's corporate Image is supported must be kept. A catalogue may promote products within promotional packages or lithe known products; it may inform the audience about the new comfort and convenience of a service or it can simply contain small businesses' month offers. Market Survey and source selection: Market research is a continuous process for gathering data on product characteristics, suppliers' capabilities and the business practices that surround them—plus the analysis of that data to make acquisition decisions. This requires one to collect and analyze information about the market that subsequently can be used to determine whether the need can be met by products or services Department of EEE, SJBIT Page 3 Electrical Design Estimation and Costing 10EE82 available in the commercial market; whether commercial practices regaiding customizing, modifying products or tailoring services are available to meet customer needs; what are the customary terms and conditions, including warranty, buyer financing, and discounts under which commercial sales are made; and whether the distribution and logistics support capabilities of potential suppliers are sufficient to meet the needs of the government. Marret research information can be used to shape the acquisition strategy, to determine the type and content of the product description or statement of work, to develop the support strategy, the terms and conditions included in the contract, and the evaluation factors used for source selection. Various locational difficulties are described: 1. Remoteness 2. Confined sites 3. Labor availability 4. Weather 5. Design considerations (related to location). 6. Vandalism and site security 6. List out guidelines for inviting tenders. (Jan -2015) Bidding goods and services is important for several reasons. The bidding process: • allows "comparison shopping" for the best pricing and service • allows for an informed and objective choice among potential suppliers • encourages competition among suppliers • provides a standard for comparing price, quality, and service • provides a list of qualified suppliers for future bids • provides access to University business for suppliers The bid process begins with the development of a set of specifications or objectives. The Contract Administrator (CA) in conjunction with the requester must define the requirements exactly. Colleagues, technical personnel, trade manuals, and suppliers may be consulted for Department of EEE, SJBIT Page 4 Electrical Design Estimation and Costing 10EE82 assistance in developing specifications. The requirements are then communicated to the selected suppliers by a Request for Quotation (RFQ) or a Request for Proposal (RFP). 7. Write the necessity of estimating and costing. (Jan-2015) Electrical estimating is a process used by electricians, construction managers and engineers to determine the amount and cost of electricity required for a specific location or process. There are two general methods of creating accurate electrical estimates: computer software or manual calculations. Both methods have value, benefits and risks. Original electrical estimating software options were quite clumsy to use, but recent enhancements have vastly improved this tool for electrical estimation. Electrical estimating computer software has increased in popularity as it has improved in quality and performance. This tool is designed for use by electricians, architects and electrical engineers. There are different versions available for residential, commercial or prototype development. An estimating technique is an approach to predicting cost or revenue. Using a consistent methodology is important to achieve reliable and comparable results 8. Explain by giving examples for the following terms. i) Contingencies ii) Overhead charges iii) Profit (June-2014) Estimating the cost of labor for electrical construction can vary greatly from project to project, depending on the installation crew’s experience and the complexity of the project. Charging an hourly installation rate is common for electrical contractors until installation data (number of hours per installer for job completion) can be collected and projects can be estimated based on the amount of work. Electrical contractors are responsible for installing, repairing, and maintaining electrical systems in homes and commercial buildings. Due to the differences in skills and costs between home systems and commercial systems, most companies will focus solely on either residential or commercial work. Fortunately, the process of pricing an electrical job is similar no matter what Department of EEE, SJBIT Page 5 matching invoices. (June-2014) FUNCTION/ROLE OF A PURCHASING DEPARTMENT To buy at the right time. SJBIT Page 6 . it is fairly easy to price an electrical job and develop an appropriate estimate. fans and socket outlets or a total load of 800 W.passing of invoices for payment and settlement of accounts Disposing of surpluses Other activities like assisting with preparation of material expenditure/purchasing budget. For those with a basic understanding of construction and electricity. right price and right terms Ensuring the continuity of supply Selection and evaluation of suppliers/vendors Aware of long-term and short term effects Preserving and enhancing reputation of company Aware of all supply options Maintain stock level MAJOR PURCHASING ACTIVITIES Obtaining and analyzing quotations of vendors/suppliers Interview representatives and correspondence Deciding best buying terms and conditions Negotiating and checking contracts Scheduling orders and following up Work with finance department to obtain discount. Briefly explain the factors to be considered while deciding choice of wiring sys(Jan-2016) General rules for interior wiring: 1) No lighting circuit should contain more than 10 points of lights.Electrical Design Estimation and Costing 10EE82 type of building is involved. verify receipt. Department of EEE. Unit – 2 1. Explain activities of Purchase department. purchase journal entry. 9. For 5A socket outlets installed at a height of 25 cm above the floor.Electrical Design Estimation and Costing 10EE82 2) Switches must always be placed on the live wires only. Appliances requiring a current of more than 15 A shall be connected through a double pole switch of appropriate rating. the installation must have an ELCB (Earth Leakage Circuit Breaker). the switch may. 6) The main switch board must be fixed within 15 cms from the meter board (MB) so that it is easily accessible to disconnect in case of emergency.3 m above the floor level. more than two socket outlets are allowed in one power circuit. All socket outlets are to be mounted at a minimum height of 1. be mounted at a height of 1. Only 3-pin. 7) The meter board. Adequate numbers of socket outlets are to be provided at suitable places in all rooms so as to avoid use of long lengths of flexible cords. if desired. 4) When the total load exceeds 800 W for lighting only. 8) All sub-circuits (lighting or power circuit) should have its own continuous earth wire (each sub-circuit is earthed separately). 5A socket outlets are to be used in all light and fan circuits and only 3-pin. 5A socket outlets are to be used in all power circuits. 9) The wall plug socket should be of 3-pin type and the third (big) terminal is always connected to the earth. 3) Each circuit should be provided with a separate cut-out in the distribution boards for their live wires. main switch and distribution board are to be installed at a minimum height of 1. Department of EEE. 3-ph supply is to be taken and the load is to be distributed equally among the three phases. 5) No power circuit should contain more than 3000 W load and in no case. 10) The power (or heating) circuit must be drawn separately in AEH (All Electric Home)installations from the meter board itself.3 m above floor and are to be controlled by individual switches which are to be located immediately adjacent to it. 11) When the total load exceeds 5 kVA. No socket outlet of rating higher than 15 A is to be installed. SJBIT Page 7 . Socket outlets are not to be located centrally behind the appliances connected to them. Socket outlets accessible to children should be shuttered or interlocked type.5 m from the floor. is to be installed such that its bottom lies 1. 19) No fuse or switch is provided on an earthed conductor. Also. Dining rooms. living rooms and bed rooms. 16) The height at which conduit runs on a wall (horizontal run) must be a minimum of 3 m from the floor.25 m to 0. 15) All incandescent lamps should have a minimum clearance of 2. 23) Every circuit or apparatus is to be provided with a separate means of isolation such as a switch. 13) The current rating of the conductor used should be corresponding to the connected load to ensure safety to the consumers. one or two 3-pin.75 m from the floor. 15 A socket outlets are to be provided to plug-in hot plates and other appliances.5 m from the floor level and ceiling fan should have a minimum clearance of 2. are to be provided with at least one 3-pin. sockets. regulators etc. The main switch shall have two poles in case of single phase supply three poles in case of three phase supply. 24) No additional load is to be connected to an existing installation without ensuring that the installation Department of EEE.5 m and depends on the type of building. 15 A socket outlets in each. 18) The distance between the ceiling and the horizontal run may vary from 0.Electrical Design Estimation and Costing 10EE82 12) All the metal parts like metal sheaths / conduits of wiring and metal casings of all consumer appliances (starter body. all light conductors are to be insulated or otherwise safeguarded to avoid danger. if required. SJBIT Page 8 .25 m above the floor.) must be earthed properly to avoid danger due to electric shock. 21) Every installation is to be properly protected near the point of entry of supply cables by a main switch and fuse unit. iron clad switches etc. 20) Each circuit is to be protected from drawing excessive current (due to overload or insulation failure) by a fuse or automatic circuit breaker. 17) A switch board which contains switches. 22) Depending on the size of the kitchen. All plugs & socket outlets are of 3-pin type 6. 26) The switch board and socket outlets should not be fixed at locations where there are chances of water entering even in traces. Department of EEE. Unless otherwise specified. the clearance between the bottom most point of the ceiling fan and the floor shall be not less than 2.5mt above the floor 7. 11. socket outlet which automatically gets screened by the withdrawal of plug is preferable. 9.4 m. 10. Every installation is to be properly protected near the point of entry of supply cables by 2linked main switch and a fuse unit. the minimum clearance between the ceiling and the plane of the blade shall be not less than 30 cm.915 mm size. In any building . In a situation where the socket outlet is accessible to children. No fuse or switch is to be provided in earthed conductor 8.List out the general rules and guidelines for residential installation. polarity of single pole switches. water cooler etc. fan power wiring are to be kept separately. A switch board is to be installed so that its bottom lies 1. 2. Conductor used is to be of such a size that it carry load current safely. (Jun -2015) 1. Ordinary socket outlet may be fixed at any convenient place at a height above 20 cm from the floor level. 12.Electrical Design Estimation and Costing 10EE82 25) Lamp holders used in bath rooms are to be constructed or shrouded in insulating materials and fitted with protective shield and the earth continuity conductor shall not be less than 7/0. 4. SJBIT Page 9 . Every sub-circuit is to be connected to a distribution fuse board. the installations are to be tested for insulation resistance. Each 15 A socket outlet provided in building for the use of domestic appliances such as AC. 3. Each socket outlet shall be controlled by a switch which shall preferably be located immediately adjacent thereto or combined therewith. light. 2. 28) After completion of work. earth resistance and earth continuity before energization. etc.25mts above the floor. All incandescent lamps are to be hung at ht of 2. 5. 27) Looping of neutral and phase wires may be done on any one of the brass connectors embedded in insulating material such as in junction box terminals or switch terminals or holder terminals. 94 (in table 3) at 40°C (104°F) and current carrying capacity of (7/0. therefore this size of cable (7/0. Since the calculated value (26.(J VERANDAH un 4 4 201 5)(J Total Loadun = 4.5 x 220)/100 = 5. Now find the voltage drop for 100feet for this (7/0.(Ju n201 3 5)(Ju n 2201 5)5 Total Current = I = P/V = 5400W /220V =24.94 = 26.036 cable according table 1. But in our case.5V Department of EEE. the length of cable is 35 feet.5 x1000W = 4500W 20% additional load = 4500 x (20/100) = 900W 201 Total Load = 4500W + 900W = 5400W 5)5 1. so the temperature factor is 0.Electrical Design Estimation and Costing 10EE82 3.5A (from Table 1) which is 7/0. the voltage drop for 35feet cable would be Actual Voltage drop for 35feet = (7 x 35/100) x (24. Therefore. Now check the selected (7/0.036) cable with temperature factor in Table 3.036) is also suitable with respect to temperature.Estimating the quantity of materials required for writing a newly constructed building where plan is shown in fig Assume the details of the load All dimensions are in meters (Jun -2015) KITCHEN HALL BATH 3 ROOM 3.5/28) = 2. SJBIT Page 10 .5kW = 4.32 Amp) at 40°C (104°F) is less than that of current carrying capacity of (7/0. current carrying capacity of this cable at 40°C (104°F) would be Current rating for 40°C (104°F) = 28 x 0.1V And Allowable voltage drop = (2.32 Amp.036) cable which is 28A. therefore.036 (28 Amperes) it means we can use 7/0.036) cable from Table 4 which is 7V.036) is 28A.5A Now select the size of cable for load current of 24. 12. 4. Every sub-circuit is to be connected to a distribution fuse board. A switch board is to be installed so that its bottom lies 1. All incandescent lamps are to be hung at ht of 2. 2. Therefore. socket outlet which automatically gets screened by the withdrawal of plug is preferable. Each 15 A socket outlet provided in building for the use of domestic appliances such as AC. fan power wiring are to be kept separately. Department of EEE. 10. Unless otherwise specified.Electrical Design Estimation and Costing 10EE82 Here The Actual Voltage Drop (2. What are the general rules to be followed for internal wiring. Ordinary socket outlet may be fixed at any convenient place at a height above 20 cm from the floor level. Draw the single line dia for lighting and heating circuits on the sketch. Each socket outlet shall be controlled by a switch which shall preferably be located immediately adjacent thereto or combined therewith. (Jan-2015) 1.4 m. the minimum clearance between the ceiling and the plane of the blade shall be not less than 30 cm.036) for that given load for Electrical Wiring Installation 4. 5.5V. 9.1V) is less than that of maximum allowable voltage drop of 5. length and size of the wire by taking safety factor equals to two.25mts above the floor. 5. The fig shows the plan of a low income group government quarter. Conductor used is to be of such a size that it carry load current safely. water cooler etc. In a situation where the socket outlet is accessible to children. No fuse or switch is to be provided in earthed conductor 8. Calculate total load . In any building .5mt above the floor 7. the appropriate and most suitable cable size is (7/0. light. 3. SJBIT (June-2014) Page 11 . All plugs & socket outlets are of 3-pin type 6. 11. the clearance between the bottom most point of the ceiling fan and the floor shall be not less than 2. Every installation is to be properly protected near the point of entry of supply cables by 2linked main switch and a fuse unit. 38mm (13Amp) Cable suggested for Sub-Circuit 2 = 7/. Deciding the number of Sub-circuits: The total load in a commercial building is calculated taking into consideration the general lighting load.029” (13Amp) or 1/1.27 So cable suggested for Main-Circuit = 7/.(Jan-2016) Design consideration of Electrical Installation in Commercial building: i. The distribution fuse boards shall be located as near Department of EEE.029” (21Amp) or 7/0.1A = 29. sub-switch boards. maindistribution boards.1A + 18.Electrical Design Estimation and Costing 10EE82 Total load of Sub-Circuit 1 = (2 x 1000) + (4 x 80) + (2×120) = 2000W + 320W + 240W = 2560W Current for Sub-Circuit 1 = I = P/V = 2560/230 = 11.044” (34Amp) 0r 7/1.85mm (24Amp) Total Current drawn by both Sub-Circuits = 11. ii. The sub-distribution boards. Deciding the size of rating of switch boards and distribution boards: Sub circuits are fed from sub-distribution boards. Cable suggested for sub circuit 1 = 3/.1A Therefore.1A Total load of Sub-Circuit 2 = (6 x 80) + (5 x 100) + (4 x 800) = 480W + 500W + 3200W= 4180W Current for Sub-Circuit 2 = I = P/V = 4180/230 = 18. List out the design consideration of electrical installation in commercial bldgs. The total requirements are then tabulated and the number and size of sub-circuits are determined. which is turn are fed from main distribution boards and to which supply comes from the main switch board.04mm (31Amp) Unit – 3 1. and main switch boards are designed stage by stage considering the load at different levels. The load on each light-fan sub-circuits shall be restricted to 800 watts or 10 outlets and the load on each power sub-circuit should be restricted to 3000 watts or 2 outlets.the motor load and other power loads. SJBIT Page 12 . Electrical Design Estimation and Costing 10EE82 as possible to the centre of the load they are intended to control. Conductors of ac supply and dc supply shall be bunched in separate conduits. In a bus-bar chamber these are fixed four of which three are for the three phases and the fourth for the neutral. Deciding the size of conduits: The size of conduit is determined from the size of the cables and the number of cables to be drawn though it. The size of angle iron depends upon the weight and size of the switchboard or distribution board to be mounted on the frame. v. They shall be marked "Lighting" or "Power" as the case may be.Explain the determination of load calculation selection of size of service connection and nature of supply. and also marked with voltage and number of phases of the supply. The conduit size is stated in term of its outer diameter. (Jun -2015) Conduit wiring : • Rigid non-metallic conduits are used for surface. Any type of mounting frame can be made with suitable angle iron. SJBIT Page 13 . Deciding the size of Cables: The size of cables or conductors feeding the different stages of supply connection can be found out by calculating the actual current value at each stage. (Refer IS: 732 . The size of busbar chamber depend on (a) size and number of strips used. vi. iv.1983) iii. (b) number and rating of switches to be mounted on it. Bus bar and bus bar chamber: Bus bar camber consists of bus bars which are strips of copper or aluminium. Mounting arrangement of switchboards and distribution boards: Switchboards and distribution boards can be mounted on to the wall or on the floor. For electricity distribution from a substation or main switch board to a number of subswitchboards.1 kV grade single core cables that may be drawn into Department of EEE. PVC insulated armored and PVC sheathed cable installed in under ground trenches should be made use of. recessed and concealed conduit wiring. The numbers of insulated cables that may be drawn into the conduit are given in table. The incoming lines are connected to these distribution bus bars through the main switch fuse and the load circuits are supplied from the bus bar through the switch fuse units. Maximum permissible number of 1. 2. 1st floor and 2nd floor having same plan that of ground floor. Fig Shows the plan of ground floor of school building .School building consists at ground floor . Then 1 no.15 Number of Sub-circuits: )(J un Taking 8 points per circuit or 560 W per 20 No. ii. SJBIT Page 14 . inspection boxes. of Sub-circuits in ground floor Auxillary building = 30 / 8 = 4 No.( (all dimensions are in meters) Ju n20 i.Electrical Design Estimation and Costing 10EE82 rigid non metallic conduits Conduit shall be fixed by saddles secured to suitable wood plugs or other plugs with screws at an interval of not more than 60 cm. whenever necessary. No. 4 way single phase ICDB is required for wiring the 4 no's 15A power socket outlets.( Ju n20 Class 15 )(J Room un -3 20 15 )5 7. elbows or similar fittings.( Ju n20 Class 15 )(J Room un 2 20 15 )5 7. 10 7. bends or diversions may be achieved by bending the conduits or by employing normal bends. 3.(J un 201 5)(J un Wc201 1 5)5 Wc 2 (Jun -2015) 2 Wc 3 Wc 4 1. inspection bends. of Sub-circuits in ground floor main 15 )5 Passage circuit building = 45 / 8 = 6 No. of Sub-circuits in first floor main building = 44 / 8 = 2 No's 10 way single phase ICDB's are required for wiring the circuits in the two floors. of Sub-circuits in first floor Auxillary building = 27 / 8 = 4 2 No's 10 way single phase ICDB's are required for wiring the circuits in the two floors. Deciding the cable size: Department of EEE. Draw single line diagram for ground floor and calculate materials required for three floors.( Ju n20 Class 15 )(J Room un 1 20 15 )5 d 7.( Ju n20 Staff 15 )(J room un 20 15 )5 d d d 1. 24 mm aluminium conductor cable of current carrying capacity 42A can be used. Fan and 5A Socket points from the distribution boards can be done by 1/1. (Higher size of cable is choosen taking into account the future expansion of the building) ii.5 3 415 L IA = = × 3 1/2 core 25 sq mm PVC insulated aluminium conductor cable or four core 7/2. Cable has to be run from the main switch board to the different distribution boards in each area.24 mm aluminium conductor cable of current carrying capacity 20A can be used for connecting MSB and DB's 1 and 3.5 draws a current of 17.4A. b) Wiring of 15A power socket points from the DB. iii.67 240 A = Single core 1/2.80 mm aluminium conductor cable of current carrying capacity 27A can be used for connecting MSB and DB.1 and DB.0 240 A = Single core 1/1.40 mm single core aluminium conductor cable.9 kw. 10 way. Load current = 4000 16. a) Wiring of light.4. So 30A DP isolator can serve as incomers to these DB's.3 and 3. Since Department of EEE. Load current = 16900 23.2 and DB.4 = 2640 watts. Load current = 3960 16. Single phase 15A per way ICDB's can control the different sub-circuits.5A. Deciding the switchboards and distribution boards: The rating of switch boards & distribution boards are decided by knowing the load current. 3-phase 4 wire system of supply is choosen. SJBIT Page 15 .3A. a) Average load on DB. The distribution boards are located at different locations as shown in fig. c) Average load on DB. & the load on DB. b) Average load on DB.5 = 4000 watts. Total wattage of the scheme = 16900 watts = 16.5 can be done by 1/1.80 mm single core aluminium conductor cable. iii.Electrical Design Estimation and Costing 10EE82 i.80 mm aluminium conductor cable of current carrying capacity 15A can be used for connecting MSB and DB's 2 and 4. The average load on DB's 1 & 3 draws a current of 15. Load current = 2640 11. 6 way or 4 way. So 15A DP isolator can serve as incomers. 3.3 = 3960 watts.5.5 240 A = Single core 1/2. The avrage load & DB's 2 and 4 draws a current of 10. each level. 1 no 30A TPN switch is kept as spare for future expansion. 4 SWG aluminium wire.28 sq. Total area of 16 SWG MS sheets required for the bus bar 2) Allowance for wastage and cutting 20% = 0. Allowance for wastage = 0.18 mm Al. 1 no 30A TPN and 1 no.02 sq.Electrical Design Estimation and Costing 10EE82 the total load current of the scheme is 23A.66 sq. .18 mm Al. m (m2) Total = 1. 60A TPN.4 mm x 3. Strips for phase bars 1 x 3 = 3m Length of 12. m (m2) b.5 w ill help in understanding this arrangement more clearly. also considering the future expansion of the building. Strips for phase bars 1 = 1m 4 no's 30A/15A/DPIC switches are to be fixed on to the top of the bus bar chamber and 1 no. 3 No's 30A DPIC switches and 2 no's 15A DPIC switches are provided for controlling the five DB's located at different places. bakelite supports of thickness 0. strips/ wires can be used. different sizes of Al. SJBIT Page 16 . DPIC switches to the bottom of bus bar chamber.18 mm AL strips are c for neutral bar considering the maximum current flowing through the bus bar is 60A.14 sq. For inter connecting the switches of different ratings to the bus bars. 30A TPN/DP switch = No. To keep the bus bars in fact inside the bus bar chamber. iv.3 m.4 mm x 3. Department of EEE. Bus bar and Bus bar chamber. the main switch incoming is choosen as 60A TPN switch. Length of 25. mm c. The schematic or line diagram shown in fig. 25. The busbar chamber is made up of 16 SWG MS sheets. 3.7 mm x 3. a.3 mm Total area of 2 no's bakelite sheets for bus bar supports. mm & cutting 20% Total = 0. School building consists of gnd floor.8kW = 5800W Voltage = 230V Current = I = P/V = 5800 / 230 = 25.036 cable according table 1 Now check the selected (7/1. SJBIT Page 17 . 8 SWG aluminium wire. Department of EEE. therefore this size of cable (7/1.04) cable which is 31A.04) cable with temperature factor in Table 3. Draw single line dia for gnd floor & calculate material required for three floors.2A 20% additional load current = (20/100) x 5.97 (in table 3) at 35°C (95°F) and current carrying capacity of (7/1.04 (31 Amperes) it means we can use 7/0.97 = 30 Amp. (June-2014) Load = 5.Electrical Design Estimation and Costing 10EE82 15A DP switch = No.2A + 5A = 30. therefore.2A (from Table 1) which is 7/1.2A Now select the size of cable for load current of 30. 1st floor.2A = 5A Total Load Current = 25. current carrying capacity of this cable at 40°C (104°F) would be Current rating for 35°C (95°F) = 31 x 0. fig shows the plan of ground floor of school building. so the temperature factor is 0. Since the calculated value (30 Amp) at 35°C (95°F) is less than that of current carrying capacity of (7/1. 2nd floor having same plan that of gnd floor. (1 set for 30A TPN & 3 sets for 30A DP) = 3 m Length of n 4.04) is 31A.04) is also suitable with respect to temperature. List and explain the design considerations of electrical installation in commercial buildings (Jan-2015) Ans : Same as Unit-3 (1a) 5. 6V And Allowable voltage drop = (2. Department of EEE.5 x 230)/100 = 5.35V) is greater than that of maximum allowable voltage drop of 5. But in our case. SJBIT Page 18 .1 mV (See table (5)). Therefore. the voltage drop for 35 meter cable would be: Actual Voltage drop for 35meter = = mV x I x L (7/1000) x 30×35 = 7. According to Table (5) the current rating of 7/1.75V Here the actual Voltage drop (7. the actual voltage drop for 35 meter cable would be Actual Voltage drop for 35meter = = mV x I x L (4.75V. (iv) The lead-in wires are of size sufficient to carry the full. Service Connections: In case of overhead line.35V = 5. Therefore.04) which is 7/1. Therefore.1/1000) x 40×35 = 7. Unit .Electrical Design Estimation and Costing 10EE82 Now find the voltage drop for per ampere meter for this (7/1.74V This drop is less than that of maximum allowable voltage drop. 1.load current.4 1.35 and find the voltage drop again.35 is 40Amperes and the volte drop in per ampere meter is 4. this is not suitable size of cable for that given load. check and ensure that: (i) The lines are terminated at a sufficient distance from the building. the length of cable is 35 meter.04) cable from (Table 5) which is 7mV. So we will select the next size of selected cable (7/1.List out the points to be checked while carrying out inspection of wiring install(Jan-2016) Internal wiring should be inspected once a year and the following points should be checked while carrying out inspection of tho wiring installation. (iii) The fuse wire of correct rating is provided on the phase line. (ii) The danger notice exists to warn the staff. So this is the most appropriate and suitable cable size. (iv) The single pole switches are provided on the live conductor. Explain in detail testing of polarity. (iii) The insulation resistance between conductor and earth and between conductors is more than permissible value as per IE rule. ln case of underground cable check up and ensure that (i) the cables are properly sealed and there is no leakage of cable oil (ii) there are earth connections to the cable armouring. (vi) The phase and neutral wires are clearly marked for identification. (ix) The leakage current is not more than 1/5. 0. Main Switchboard: In case of main switchboard check and ensure that (i) The voltage available is correct. submain distribution boards.Electrical Design Estimation and Costing 10EE82 (v) The lead-in pipe is properly earthed and bonded and pipe ends are provided with insulating bushes to protect the wires from mechanical damage. conduit pipes enclosing VIR or PVC cables are properly earthed. (vii) The metallic covering of iron clad switch. 2. (i. GI pipe.) (ii) The main switch is provided close to the point of commencement of supply. 3. (vi) The metallic frames of all power equipment are earthed by two independent earth conductors. 2.e. within permissible limits of declared voltage. distribution board. (iii) The fuse of correct size is provided on the live pole.914 m). (iv) The main switch is easily identified and is easily accessible so that in case of emergency the entire supply to the building can be switched off at once. Department of EEE. Miscellaneous: The points to be checked are : (i) No branch circuit feeds more than 10 points or 800 watt load. (v) The electrical resistance from the point of connection with the earth electrode to any point on ECC in the complete installation is not more than one ohm. (v) There is a clear working space all round the board (as mentioned in IE rule 51 i. SJBIT (Jan-2016) Page 19 . (vii) Caution notice in Hindi or other local language is placed. Mention the different types of tests conducted on wiring installations.e.000 of maximum supply current. Polarity Test Testing of Earth Continuity Path. Pocket neon testing tubes for the purpose are available An alternative method is by means of a test lamp. If the test lamp lights on one of the two contacts.Electrical Design Estimation and Costing 10EE82 Testing of Polarity of Single Pole Switches. the leakage current will start giving severe shock to the person touching it. For safety all the metal pieces or coverings such as conduits. It in necessary that single pole switches are placed in + ve side or live side so that by making switch off the lamp can be made quite dead. even when the single pole switch is in open position which may easily lead to accidents. does not give light on either contact of the switch. then lamp holder or the fan as well as part of wiring will remain alive. one end of test lamp is connected to earth and the other end is tapped by lead to each contact of each switch in turn. main fuse is inserted.2 (a) and if test lamp. its one terminal is held in the hand and the other against the feed terminal of the switch. While performing polarity test by means of a small neon tube tester. Department of EEE. this test is performed. so must be connected correctly. In this method all the lamps are removed. it indicates that the switch is on neutral wire. As regard the function of a single pole switch. 5. never on neutral wire. if the switch is correctly connected the neon lamp will glow. it indicates that switch is on the live wire as shown in Fig. metal covers of switches etc. To ensure that all the switches are placed in phase or live conductors and not in neutral conductor. must be solidly connected to earth otherwise on the damage of insulation. it is equally effective whether it is connected in live or neutral wire but from the safety point of view it is necessary that all single pole switches are provided on phase or outer wire. For example. A convenient and quicker method of performing this test is by means of a small neon tube tester. SJBIT Page 20 . a person who is replacing lamp even after opening the single pole switch is liable to get shock if he comes in contact with the line terminal of the lamp holder. main switch is put in ‘on’ position. The reason of it is that if the switch in provided on neutral wire. One end of the earth continuity tester is connected to an independent earth and the other end is connected to the wiring say to a switch or conduit. SJBIT Page 21 . The pointer will indicate the earth resistance. 3. Heating = 2 kW. Estimate the material required for single phase overhead service line of a house located 20 meters away from the pole. Higher than this value shows that conduit or switch has not been properly earthed. main fuse withdrawn. The nominal system supply voltages listed below can vary by ±10% or more. all other switches in on position and lamps in their respective holders. Watt Node meter models are available in seven different versions that cover the full range of electrical services types and voltages. Meters and current transformers are designed for use on either 50 or 60 Hz systems. (Jan-2016) 4. With following loads: Lighting load = 800 watts. which should not exceed the value of one ohm. main switch should be opened. Classification of Different Services: Alternating current electric power distribution systems can be classified by the following properties: Frequency: 50 Hz or 60 Hz Number of phases: single or three phase Number of wires: 2.Electrical Design Estimation and Costing 10EE82 In case of conduit wiring there is a possibility of the conduit joints to become loose or to be separated resulting in high resistance in the earth path. or 4 (not counting the safety ground) Neutral present: Wye connected systems have a neutral Delta connected systems typically do not have a neutral Voltage levels: Low Voltage: 600 volts or less Department of EEE. For earth continuity test. (Jun -2015) This describes various types of utility electrical services and supply voltages. 3. Take factor of safety 2. Write short note on service lines. the phase-to-neutral voltages should be equal if the load is balanced. When tampering is detected. Power companies often install remote-reporting meters specifically to enable remote detection of tampering.500 volts High Voltage: 46.Electrical Design Estimation and Costing 10EE82 Medium Voltage: 601 volts to about 34. At US$0. legal in most areas of the USA. or the service is disconnected.000. the normal tactic. SJBIT Page 22 . a standard residential 50 A meter causes a legally collectible charge of about US$5. Meter readers are trained to spot signs of tampering. is to switch the subscriber to a "tampering" tariff charged at the meter's maximum designed current. The change to smart power meters is useful to stop energy theft. and specifically to discover energy theft.095/kWh.00 per month. Department of EEE. 5. the maximum rate may be charged each billing period until the tamper is removed. Write the reason for excess recording of energy consumption by energy meter(Jan -2015) Meters can be manipulated to make them under-register. This theft or fraud can be dangerous as well as dishonest.000 volts and up Line-to-line voltages are typically 1.732 times the phase-to-neutral voltages: In symmetrical three-phase electrical system. effectively allowing power use without paying for it. and with crude mechanical meters. metering at the substation can alert the Department of EEE. and many modern meters can detect or compensate for them. extra clock setting. The owner of the meter normally secures the meter against tampering. glued buttons. Revenue meters' mechanisms and connections are sealed. Magnets can also saturate current transformers or power-supply transformers in electronic meters. magnetic anomalies. Strong magnets saturate the magnetic fields in the meter so that the motor portion of a mechanical meter does not operate. ambient magnetic fields. though countermeasures are common. Some combinations of capacitive and inductive load can interact with the coils and mass of a rotor and cause reduced or reverse motion. etc. Rectified DC loads cause mechanical (but not electronic) meters to under-register. However.Electrical Design Estimation and Costing 10EE82 A common method of tampering on mechanical disk meters is to attach magnets to the outside of the meter. Some tampers bypass the meter. reversed or switched phases etc.[34] Disconnecting a meter's neutral connector is unsafe because shorts can then pass through people or equipment rather than a metallic ground to the generator or earth. Meters may also measure VAR-hours (the reflected load). Lower power magnets can add to the drag resistance of the internal disk resistance magnets. DC current does not cause the coils to make eddy currents in the disk. Safe tampers of this type normally increase the neutral current at the meter. Newer computerised meters usually have counter-measures against tampering. Most split-phase residential meters in the United States are unable to detect neutral currents. so this causes reduced rotation and a lower bill. All of these effects can be detected by the electric company. modern tamper-resistant meters can detect and bill it at standard rates. SJBIT Page 23 . Even if an earth ground is safe. neutral and DC currents (elevated by most electrical tampering). wholly or in part. A phantom loop connection via an earth ground is often much higher resistance than the metallic neutral connector. AMR (Automated Meter Reading) meters often have sensors that can report opening of the meter cover. Even simple mechanical meters can have mechanical flags that are dropped by magnetic tampering or large DC currents. inverted installation. 415 .S.5 1.25 3 415 0. Find the materials required for 1- overhead service lines of a house located 10 meters away from pole. 16 mm2 aluminium conductor having current carrying capacity of 38 A shall be used from meter board to main board. we have full.9 A Hence cable from meter board to main board shall have a current carrying capacity 1. 415 .54 3 415 0.6 times of full.85 0. including wastage = 1. Length of 25 mm exible conduit from HG conduit to motor terminals fan machine no.54 + 1. inter-ties.0 m 2.57 + 11. Length of 31 mm exible conduit from meter board to main switch board and from main switch board to distribution board.25 = 21.load current of the mot Hence 3-core. in order to find and fix power distribution problems.Electrical Design Estimation and Costing 10EE82 operator to tampering.75 .7 . 3 11.8 3.[35] Indoor marijuana growers aware of this are particularly motivated to steal electricity simply to conceal their usage of it.85 0.8.54 + 7. 6. SJBIT Page 24 . 000 5.85 0. with following loads :Lightning =300 watts. 3 1. including wastage = 1. Narcotics detectives associate abnormally high power usage with the lighting such operations require. These investigations are an effective method to discover tampering.8 5. Power thefts in the U.load current for these motors = 1. 3 7. Power companies normally investigate discrepancies between the total billed and the total generated.load currents of motors as ( ) ( ) ( ) 1 2 34 0.Assume safety factor=2 (Jan -2015) power supply and another for domestic supply.57 3 415 0.5 . 415 . 1100 V grade PVC insulated. are often connected with indoor marijuana grow operations.7 1. Assuming efficiency of motor 85% and power factor 0. The current rating of main switch in the starting current of one motor of highest rating plus full 1.8 I I For kW V phase motor A I For kW V phase motor A I For kW V phase motor A × = Total full. Heating= 2500 watts. 000 0. 000 3.75 1. and transformers normally have a high-accuracy meter for the area served. Substations. 4.0 m Department of EEE. Department of EEE.4.3 metre for every 33.2 metres plus 0. SJBIT Page 25 .1 metres (2) No conductor of an overhead line. if bare . erected along any street shall at any part thereof be at a height less than(a) for low and medium voltage lines 5. including service. 7. Write the reason for excess recording of energy consumption by energy mtr (June-2014) Meters can be manipulated to make them under-register.000 volts or part thereof by which the voltage of the line exceeds 33.where than along or across any street shall be at a height less than(a) for low. medium and high voltage lines up to and including 11.000 volts: PROVIDED that the minimum clearance along or across any street shall not be less than 6. lines. including service lines.0 (c) for high voltage lines above 11. This theft or fraud can be dangerous as well as dishonest.8 metres (3) No conductor of an overhead line including service lines. medium and high voltage lines up to and including 11. Span lengths 1) No conductor of an overhead line. 8.1 metres. erected across a street shall at any part thereof be at a height less than(a) for low and medium voltage lines 5. if insulated 4.Electrical Design Estimation and Costing 10EE82 3. Length of 19 mm exible conduit required for connecting motor switches to motor starters for all the four machines and HG conduit to motor terminals for machines no.2 metres (4) For extra-high voltage lines the clearance above ground shall not be less than 5.5 metres (b) for high voltage lines 5. Explain points to be checked while carrying out inspection of wiring installat(Jan-2015) Conductors configuration spacing and clearances. erected else.8 metres (b) for high voltage lines 6. 1.6 metres (b) for low. effectively allowing power use without paying for it.000 volts 5.000 volts.000 volts. Revenue meters' mechanisms and connections are sealed. neutral and DC currents (elevated by most electrical tampering). and many modern meters can detect or compensate for them. the maximum rate may be charged each billing period until the tamper is removed. The change to smart power meters is useful to stop energy theft. SJBIT Page 26 . All of these effects can be detected by the electric company. magnetic Department of EEE. Even simple mechanical meters can have mechanical flags that are dropped by magnetic tampering or large DC currents. etc. Strong magnets saturate the magnetic fields in the meter so that the motor portion of a mechanical meter does not operate. the normal tactic. legal in most areas of the USA. or the service is disconnected. DC current does not cause the coils to make eddy currents in the disk. A common method of tampering on mechanical disk meters is to attach magnets to the outside of the meter. Magnets can also saturate current transformers or power-supply transformers in electronic meters.095/kWh. so this causes reduced rotation and a lower bill. At US$0. and with crude mechanical meters. Meter readers are trained to spot signs of tampering. Newer computerised meters usually have counter-measures against tampering. When tampering is detected.Electrical Design Estimation and Costing 10EE82 Power companies often install remote-reporting meters specifically to enable remote detection of tampering. though countermeasures are common. Meters may also measure VAR-hours (the reflected load). Lower power magnets can add to the drag resistance of the internal disk resistance magnets. is to switch the subscriber to a "tampering" tariff charged at the meter's maximum designed current. Rectified DC loads cause mechanical (but not electronic) meters to under-register. and specifically to discover energy theft. ambient magnetic fields. a standard residential 50 A meter causes a legally collectible charge of about US$5.000. Some combinations of capacitive and inductive load can interact with the coils and mass of a rotor and cause reduced or reverse motion. The owner of the meter normally secures the meter against tampering.00 per month. AMR (Automated Meter Reading) meters often have sensors that can report opening of the meter cover. 8 5.85 0. we have full.85 0.8 I I For kW V phase motor A I For kW V phase motor A I For kW V phase motor A × = − = = × × Total full-load current for these motors = 1.S.7 . modern tamper-resistant meters can detect and bill it at standard rates. 000 3. wholly or in part. 3 11. are often connected with indoor marijuana grow operations. with foll loads : Lighting = 300 Watts.57 3 415 0.8. These investigations are an effective method to discover tampering.[35] Indoor marijuana growers aware of this are particularly motivated to steal electricity simply to conceal their usage of it.5 1. Safe tampers of this type normally increase the neutral current at the meter. Substations. Heating= 2500 Watts Assume safety (June-2014) power supply and another for domestic supply. inverted installation. 000 5. Power companies normally investigate discrepancies between the total billed and the total generated. Most split-phase residential meters in the United States are unable to detect neutral currents.54 + 1. find the material required for 1pase overhead service line of a house located 10 mts away from pole. Even if an earth ground is safe. A phantom loop connection via an earth ground is often much higher resistance than the metallic neutral connector. in order to find and fix power distribution problems.Electrical Design Estimation and Costing 10EE82 anomalies. glued buttons.54 3 415 0. 3 1. Narcotics detectives associate abnormally high power usage with the lighting such operations require.85 0. Some tampers bypass the meter.25 = 21. Assuming efficiency of motor 85% and power factor 0. metering at the substation can alert the operator to tampering.9 A Department of EEE. 3 7. 415 . However.7 1.75 . extra clock setting. inter-ties. and transformers normally have a high-accuracy meter for the area served.25 3 415 0.8 3.54 + 7. Power thefts in the U. 415 . reversed or switched phases etc.5 . 415 . factor=2. 9.[34] Disconnecting a meter's neutral connector is unsafe because shorts can then pass through people or equipment rather than a metallic ground to the generator or earth.57 + 11. 000 0. SJBIT Page 27 .load currents of motors as 1. 4. 5. List out important consideration regarding motor installations. The starters are used to limit the starting current to a desirable value. regardless of its size shall be provided with a switch fuse placed near it. Every motor.25 metres. In addition to switch fuse all motors shall be provided with suitable means for starting and stopping (starters) placed at convenient places. Length of 25 mm exible conduit from HG conduit to motor terminals fan machine no. Looping of conductors and use of the joints shall not be done. (Jan-2016) IMPORTANT CONSIDERATION REGARDING MOTOR INSTALLATION WIRING These are as detailed below. switches and motors shall not exceed 1. SJBIT Page 28 .0 m 3. Length of 31 mm exible conduit from meter board to main switch board and from main switch board to distribution board. star-delta starters.0 m 2. 3. 16 mm2 aluminium conductor having current carrying capacity of 38 A shall be used from meter board to main board. All equipment used in power wiring shall be of iron clad construction and wiring shall be of the armoured cable or conduit type (IE Rule 51). auto transformer-starters (or rotor Department of EEE. 2. Length of 19 mm exible conduit required for connecting motor switches to motor starters for all the four machines and HG conduit to motor terminals for machines no. 1100 V grade PVC insulated. 4.Electrical Design Estimation and Costing 10EE82 Hence cable from meter board to main board shall have a current carrying capacity 1. including wastage = 1. including wastage = 1. The current rating of main switch in the starting current of one motor of highest rating plus full load curr 1. The length of exible conduit used for connections between the terminal boxes of motors andstarters. Direct-on-line starters. Woodwork shall not be used for mounting of switchgear. 1. [IE Rule 50 clause (d)] 6.6 times of fullHence 3-core. Unit-5 1. 1. 415V TPIC switches. The conduit should preferably be laid in covered trenches to facilitate operator movement (safe). Show the key diagram and estimate quantity of material required.5 times full-load current = 1. Motor efficiency 85% and power factor 0. 2.8 (lagging).75 kW and below 11 kW and above 11 kW respectively. 3. 0. 6 mm2 aluminium conductor cable of current carrying capacity 24 A may be used. 5. 4. Flexible conduit of size 25 mm will be used for connecting motor switch and motor starter and of size 31 mm will be used for connecting heavy gauge conduit to motor. Two earth wires will be run side by side for earthing the motor. The motor shall be installed on suitable foundation.5 metres from ground level. As from meter board to main board and main board to motor control board only one 3-core cable is to be run so a HG conduit of size 25mm will be run from meter board to main board and from main board to motor control board.06 = 22. 3 phase. Length of 25mm HG Rigid Conduit Department of EEE. above 0. The motor and starter are to be procured through separate contract. 7. 2. Laying of cables must be in separate conduits for separate motors. SJBIT Page 29 . starter and switches. 6. Hence three-core PVC 1100V grade. shows the plan of workshop. Full load current = Starting current = 1. 8.The Fig. Motor disconnect switches and main switches are to be supplied by wiring contractor. The main switch and motor switch to be used will be 32 A. motor switch and starter shall be mounted at a height of 1.2 m above the floor level. All the conduits are to be run exposed on walls.Electrical Design Estimation and Costing 10EE82 resistance starters in case of slip-ring induction motor)are used for ac motors of rating up to 0. (Jan-2016) Assumptions made: 1. 7.75 kW. From. One 15 HP. motor starter to motor two 3-core cables carried so HG conduit of size 31 mm will be used. The main switch.5 X 15.6A. 415 y induction motor is installed. 10 96 = 3.2 + l) = 8.2 + 1.3 metres Total = 25.1 metres = 25 metres (say) Length of 31 mm HG Conduit From motor starter to ground = 1. for 10 HP motor 8 SWG GI wire will be required as earth wire.2 m Total Length= 31.5 metres (say) Length of 25 mm exible conduit required for connecting motor switch to motor starter= 0. 1/2.1 + 0.25 m Wastage and for connections.31 metre Total = 3.5 + 0.3 m from main board to motor switch (mounted on control board) = 22.2 + 0.4 = 3.5 metres Total = 22.31 = 3.80 mm (6 mm2) aluminium conductor PVC cable (i) 1 Length from meter board to main board = 0.Electrical Design Estimation and Costing 10EE82 From meter board to main board = 0. the motor frame.4 metre Total = 1. 1100 V grade.38 = 36 metres (say) Length of Earth Wire According to IE rules.0 + 0. Length of earth wire required Department of EEE. motor switch.8 metres Wastage 10% = 2. From the table for size for earth wire.2 = 0.41 = 3. motor starter.1 metres Wastage 10% = 0.25m Length of 31 mm exible conduit required for connecting heavy gauge conduit to motor = 1 metre Length of 3 core.5 metres Below ground level = 0.main switch are to be earthed by means of two separate and distinct connections.2 metres Along ground up to foundation = 1.0 metres Up to top of motor foundation = 0.13 m Total = 34.5 m (iii) l Length from motor switch to motor starter = 0. SJBIT Page 30 . Hence two separate earth electrodes will be provided for earthing purpose.3 m (ii) 1 Length from main board to motor switch = 22.25 m (iv) 2 Lengths from motor starter to motor terminal box = 2 (3. 5 metres = 60 metres (say) or 6 kg. SL Description of Material With Full Specifications Quantity Rem N Required a rks O Qu Unit ant ity 1 32A. TPIC rewirable type switch fuse unit 2 IC boards complete with locking arrangement 1 no etc. grade 6 mm2 aluminium 4 do 6 conductor PVC cable 25 do 7 Conduit bends 6 do i) 31mm 2 3 4 5 2 nos ii) 26 mm 8 Conduit Saddles i) 31 mm ii) 25 mm 9 Lock nuts i) 31 mm Department of EEE.Electrical Design Estimation and Costing 10EE82 = 2 (25 + 3.2 do ii) 25 mm 5 do Flexible conduit 35 nos i) 31 mm 2 do ii) 25 mm 6 do 3 core. SJBIT Page 31 . 415V. 1 do 3.5 + 0. 1100 V.25 + l) = 59.5 m 25 do Heavy gauge (HG) 16 SWG conduit 1 do i) 31 mm 0. cement etc.) Department of EEE. Finishing. Foundation of motor. covering up. SJBIT Page 32 . building up of CI frame. check nuts with washers 25 Funnel with wire mesh 26 Charcoal 27 Salt 28 Soldering material Civil Engineering works (Digging.Electrical Design Estimation and Costing 10EE82 ii) 25 mm 10 Flexible pipe coupling complete with locknuts i) 31 mm ii) 25 mm 11 Wooden bushings i) 31 mm ii) 25 mm 12 Teak wood gutties 13 8 SWG GI wire 14 Shock treatment chart 15 Iron screws 32 mm 16 Caution plates 17 GI thimbles with nuts and bolts 18 Earth wire clips 19 GI Plate 600 mm x 600 mm x 60 mm 20 GI pipe 19 mm diameter 21 GI pipe 12 mm diameter 22 8 SWG GI wire 23 CI Cover 30 cm x 30 cm 24 GI bolts nuts. g.e.Electrical Design Estimation and Costing 10EE82 3.e. stranded or solid Conductor surface coating .g. which includes: Conductor material . which includes: Load type: motor or feeder Three phase. current to motors & rating of cables. single phase or DC System / source voltage Full load current (A) . plain (no coating).(Jun -2015) Step 1: Data Gathering The first step is to collate the relevant information that is required to perform the sizing calculation.e. you will need to obtain the following data: Load Details The characteristics of the load that the cable will supply. tinned.g. circular or shaped Conductor type .this length should be as close as possible to the actual route of the cable and include enough contingency for vertical drops / rises and termination of the cable tails Cable Construction The basic characteristics of the cable's physical construction.normally copper or aluminium Conductor shape .or calculate this if the load is defined in terms of power (kW) Full load power factor (pu) Locked rotor or load starting current (A) Starting power factor (pu) Distance / length of cable run from source to load . SJBIT Page 33 . silver or nickel Department of EEE. Typically. Explain determination of input power. g.e. is it installed on cable tray / ladder.e. 2C. etc. for underground cables.g. insulation. more copper or aluminium) have lower resistive losses and are able to dissipate the heat better than smaller cables. conductors. XLPE. Department of EEE.g. etc) must be capable of withstanding the temperature rise and heat emanating from the cable. the number of cables that are bunched together Cable spacing. The current carrying capacity of a cable is the maximum current that can flow continuously through a cable without damaging the cable's insulation and other components (e. is it directly buried or buried in conduit? for above ground cables. are the cables installed in trefoil or laid flat? Step 2: Cable Selection Based on Current Rating Current flowing through a cable generates heat through the resistive losses in the conductors. SJBIT Page 34 . bedding. sheath. The component parts that make up the cable (e.g. dielectric losses through the insulation and resistive losses from current flowing through any cable screens / shields and armouring. in air.Electrical Design Estimation and Costing 10EE82 Insulation type . Ambient or soil temperature of the installation site Cable bunching. Cables with larger conductor cross-sectional areas (i. bedding. Therefore a 16 mm2 cable will have a higher current carrying capacity than a 4mm2 cable.single core or multicore (e. It is sometimes also referred to as the continuous current rating or ampacity of a cable. i. armour. i. against a wall.e. EPR Number of cores .e. 3C or 4C) Installation Conditions How the cable will be installed.e. PVC. etc). which includes: Above ground or underground Installation / arrangement .g. sheath. whether cables are installed touching or spaced Soil thermal resistivity (for underground cables) Depth of laying (for underground cables) For single core three-phase cables. In the absence of any guidance.Electrical Design Estimation and Costing 10EE82 Base Current Ratings Table 1. or another problem in the electrical circuit. (Jun -2015) We depend on electricity to light our homes. 3 . turn on our television sets. copper conductor.g. 415 v. It is important to note that the current ratings are only valid for the quoted types of cables and base installation conditions. and even cook our meals. ambient temperature. a short circuit. the plan of which is shown in fi Shows the wiring dia of the layout and estimate the quantity of materials required and its cost. SJBIT Page 35 .6/1kV voltage grade. installation method. understanding what the basic components of an electrical system is a must. etc) and a base set of installation conditions (e. Example of base current rating table (Excerpt from IEC 60364-5-52) International standards and manufacturers of cables will quote base current ratings of different types of cables in tables such as the one shown on the right. the following reference based current ratings may be used 4. Department of EEE. Each of these tables pertain to a specific type of cable construction (e. etc). PVC insulated.g.50Hz squirrel cage IM is to be installed in a flour mill. When the power goes out because of a storm. 0. A 10 HP (metric). A main breaker of 100 amps will only allow 100 amps to flow through it without tripping. Main Breaker A breaker panel consists of a main breaker that is sized according to your homes’ load needs. The advantage of having a disconnect switch is for safety. It is the interrupt between the service and the branch circuits of the panel. This main breaker protects the main service wires from damages that would occur given an overload. This is where the electric company connects their wires to your homes’ feeder wires that attach to the meter on your home or power pole. Department of EEE. homes have a 100 amp or a 200 amp service. no current will flow throughout the panel. From here your meter either feeds a disconnect switch or a main breaker or fuse panel. In a tripped state. Disconnect Switch A disconnect switch is mounted on the outside of your home close in proximity to the meter on the outside of your home or power pole. The other instance is having a transfer switch in which you can switch between live power and a generator for backup power. SJBIT Page 36 . It is used to turn the power on and off to the entire electrical panel. a neutral and a ground wire.Electrical Design Estimation and Costing 10EE82 Your homes’ electricity starts with the electrical service connection. the wires would heat up and eventually could cause a fire. A typical home has a single phase service consisting of an “A” phase and a “B” phase. This is the device that measures the amount of electricity your home uses and determines the amount of money the electric company charges you on a monthly basis. Typically. In that case. In the event of a fire or flash flood. you can shut the power off from the outside of your home verses having to enter a burning home or a flooded basement. Outlets Electrical outlets are used to plug portable devices into. In a 240 volt circuit. Remember to size your breaker by the name plate rating on the device you are connecting to. outlets and furnaces. a two-pole breaker uses both phases of a circuit. These appliances don’t work unless both “A” and “B” phases are working. These circuits provide power to lighting. These switches come in many different styles and colors to suit your design needs. Their purpose is to alter the flow of current to your lights and fans in a home. These circuits can either be 120 volts or 240 volts. Televisions. Some outlets are used especially for wet areas. Wiring Department of EEE. The breakers are usually sized at 15 or 20 amps. There are single-pole. three-way. computers. using only one phase of the electrical service. central air conditioning and sub-panels are considered branch circuits. SJBIT Page 37 . an electric stove or central air conditioning.Electrical Design Estimation and Costing 10EE82 Branch Circuit Breakers Breakers that feed lighting. four-way and dimmer switches. lights. a neutral and a ground. Examples of 240 volt appliances would be an electric range. Switches Switches are the devices that turn on and off lights and fans in your home. Outlets consist of a hot feed. outlets. Most of these examples would require a two-pole 30 amp breaker. vacuums and toasters are all good examples of devices that can be plugged into an outlet. The 120 volt circuits require a single pole breaker. freezers. Department of EEE. The formal name is NM that means non-metallic sheath.Electrical Design Estimation and Costing 10EE82 Your home’s wiring consists of romex. Romex is a brand name for a type of plastic insulated wire. protected areas (inside stud walls. the plan of which is shown in below fig. This is suitable for use in dry.8 lagging. Assume efficiency of motor = 85% & powerfactor 0.). Bx cable is known as armored cable. 50 Hz induction motor is to be installed in a workshop. (June-2014) Decide Number of Conductor and Layer of Conductor: If N: number of conductors [strands]. Wires are covered by aluminum or steel flexible sheath that is somewhat resistant to damage. 415V. These different types of wiring carry electrical current from the panel to the device being fed. d: Diameter of strands. etc. show the layout of the wiring (key dia) & estimate the quantity of material required. 3 Phase. BX cable or wiring concealed in conduit. A 10 HP (metric) . on the sides of joists. that are not subject to mechanical damage or excessive heat. 5. List any eight important considerations regarding motor installation wiring (Jan-2015) Same Ans as 1 of unit -5 6. Check the rated required load requirements marked on each device to determine the needed size wire to carry the needed load. SJBIT Page 38 . The wiring is to be surface conduit. . Wiring is sized according to the load demand required.X: number of layers. Single strands of conductor wire are pulled through conduit that is the safest method for wiring for durability purposes. where than along or across any street shall be at a height less than(a) for low. if bare .0 Meter 120 mille second 132 KV 6.8 Meter 100 mille second 220 KV 8.1 Meter 160 mille second 66 KV 5.0 (c) for high voltage lines above 11. medium and high voltage lines up to and including 11.Electrical Design Estimation and Costing o 10EE82 Usually the relation between N&X take as followed. then we can get the total Diameter of cable as dT= (2X-1)d.000 volts.1 metres. erected else.000 volts 5.000 volts: PROVIDED that the minimum clearance along or across any street shall not be less than 6. If Total Number of Conductor (N)=19 Than 19=3×2-3x+1. SJBIT Page 39 .000 volts or part thereof by which the voltage of the line exceeds 33.2 metres (4) For extra-high voltage lines the clearance above ground shall not be less than 5. N= 3X2-3X+1 If N is given we can used the above relation get X. if insulated 4.6 metres (b) for low. medium and high voltage lines up to and including 11. Ground Clearance Fault Clear Time 400 KV 8.3 metre for every 33.1 Meter 300 mille second Department of EEE.2 metres plus 0. So Number of Layer (x)=3 o Than Diameter of Cable dT = (2x-1)d =5d No conductor of an overhead line including service lines. Voltage Min.000 volts.4. 4. Cross arms and Clamps: These are either of wood or steel angle section and are used on pole structures to support the insulators and conductors. The function of the line support in obviously to support the conductors so as to keep them at a suitable level above the ground. 1. 2. for supporting the conductors and taking strain or suspending the conductors respectively. due to lightning. to earth. as the case may be. 6. Bird Guards: A stick of ebonite with rounded top is xed near the insulator on the cross arm to prevent flash-over due to birds pecking on the conductors (on line with pin insulators). Lightning Arrestors is discharge excessive voltages built upon the line. 10 Guard Wires are provided above or below power lines while crossing telephone or telegraph lines. Supports: Poles or towers depending upon the working voltage and the region where these are used. Conductors: Copper. Department of EEE. 12. The guard wires and steel structures are solidly connected to earth. 8. aluminium or ACSR or of any other composition depending upon the current to be carried and the span of the line. Insulators: Pin. 11. strain or suspension types. Vee-Guards are often provided below bare overhead lines running along or across public streets to make the line safe if it should break. 7.Electrical Design Estimation and Costing 10EE82 Unit-6 1. SJBIT Page 40 . Continuous Earth Wire: is run on the top of the towers to protect the line against lightning discharges. 9. 5. as below. Guys and Stays: Braces or cables are fastened to the pole at the termination or angle poles to resist lateral forces. (Jan-2016) The main components of an overhead line are enlisted. Fuses and Isolating Switches: to isolate different parts of the overhead system.List out the main components of overhead lines. 3. Phase Plates in order to distinguish the various phases. Miscellaneous Items such as vibration dampers. Typical height ranges from 15 to 55 metres (49 to 180 ft).5 m from the ground for at least 1 metre. top hampers. used to support an overhead power line.2 ACSR. The conductor used No. What are the requirements of the line supports? Describe factors governing ht of pole? (Jun -2015) A transmission tower (electricity pylon in the United Kingdom and parts of Europe. usually a steellattice tower. including concrete and wood. Assume a span of 500 mts and every 10th tower is an anchor tower. 2. They are used in high-voltage AC and DC systems.5 m from the ground.Electrical Design Estimation and Costing 10EE82 13. Danger Plate: It ia provided on each pole. Estimate the quantity of material required for running 80 km. single circuit of 66 kv transmission line using four legged fabricated steel structures. Barbed Wire: Barbed wire in wrapped on a pole at a height of about 2. 15. This prevents climbing by unauthorized persons.[1]though the tallest are the 370 m (1. as a warning measure indicating the working voltage of the line and the word “danger”. (Jan-2016) Length of line = 1 km Average span = 120 m Number of spans = 1000 8 120 = (as 3 conductors run in 3-phase 11 kV line) metres = × × = 128 1000 Length of conductor × 1 km weighs 128 kg 128 3060 391.68 390 1000 kg say kg 3 . Department of EEE. and a hydro tower in certain provinces of Canada where power generation is mainly hydro-electric) is a tall structure.. and come in a wide variety of shapes and sizes.214 ft) towers of a 2700-metre-long span of Zhoushan Island Overhead Powerline Tie. beads for jumpers etc. other materials may be used. SJBIT Page 41 . In addition to steel. 14. It is provided at a height of 2. 2 KV is stepped up to 132 KV and is supplied to the 132KV sub-station through two double circuit transmission lines.2 MW + 3. the input to the substation must be greater than the requirement. 4. The SIL of 132 KV line = (132KV) 2 /325 = 53. The second double circuit tower is constructed keeping in mind the future load demand increase.2MW) at 33KV and D (36MW) at 132 KV. Transmission towers and their overhead power lines are often considered to be a form of visual pollution. almost 130 MW 5.2) MW i. B (3. The generated 16. Estimate the quantity of materials required for adding 132KV bay at 132KV grid ss.61 = 54 MW (approx) The SIL of 33 KV line = (33KV) 2 /325 = 3. A (3. Methods to reduce the visual effect include undergrounding.2MW) and C (3.Electrical Design Estimation and Costing 10EE82 There are four major categories of transmission towers:[1] suspension. terminal.5 MW (approx) Observing the total load demand.2 mw).2 MW + 3. So one double circuit 132KV transmission lines (54 X 2 = 108 MW) only can satisfy this. tension. (Jun -2015) The sub-station is connected with three substations or load viz.1 Assumptions The value of surge impedance of transmission lines under consideration = 325 Ω Total load requirement = 3. Hence the input of the substation can be as high as (108 X 1.2 MW + 36 MW The distance between the substation & the neighboring generating station is 50km. The lines first supply the power to the 132KV bus A of the sub-station. Department of EEE.e.2 times of the theoretical value. Some transmission towers combine these basic functions. the SIL can increase to 1. andtransposition. After analyzing the requirements of the loads & SIL of transmission lines the whole arrangements are done in the following way: 2. As the distance between the substation and the generating station is only 50km. SJBIT (Jan-2015) Page 42 . Draw & explain typical ac electrical power supply system.35 = 3. The primary transmission voltages are 110. Estimate quantity of materials required for adding 132KV bay at 132 KV grid substation. 6.3. 6. 6. 11 or 33 kv. (June-2014) Ans is same for que 4 of unit -6 Department of EEE. for example. hospitals. some may not have secondary transmission and the others may not have transmission at all. Smaller power systems are also found in industry. (iii). electric rail systems. Specialised power systems that do not always rely upon three-phase AC power are found in aircraft. Modern ac power systems usually consist of the (i) generating stations (ii) step up transformer stations (iii) transmission lines (iv)switching stations (v) step down transformer stations (vi) primary (high voltage) distribution lines or net-works (vii) service transformer banks (viii) secondary (low voltage)distribution lines. An example of an electric power system is the network that supplies a region's homes and industry with power . most usual value adopted in practice is 11 kv. Essentially elements (ii). the amount of power to be transmitted and the system stability.for sizable regions. 132.Electrical Design Estimation and Costing 10EE82 An electric power system is a network of electrical components used to supply. ocean liners and automobiles.6 or 3. commercial buildings and homes. Generation voltages are 3. The majority of these systems rely upon three-phase AC power . Secondary transmission voltage is normally of the order of 33 or 66 kv. the transmission system that carries the power from the generating centres to the load centres and the distribution system that feeds the power to nearby homes and industries. transmit and use electric power. The voltages for primary distribution are 1. being very small and so on. 220 or 400 kv depending upon the distance. this power system is known as the grid and can be broadly divided into the generators that supply the power.6.the standard for large-scale power transmission and distribution across the modern world. SJBIT Page 43 . (iv) and (v) fall in the transmission system and distribution may or may not include all elements enumerated above. some systems may have no primary transmission.3 kv depending upon the requirements of the bulk consumers and for secondary distribution usable voltage is 400 volts. a cement concrete muff. RCC Pole RCC poles generally have larger cross-section than the PCC poles and. Rolled Steel Joists and Rails – A suitable pad of cement concrete. the base plates or muffing are usually not provided for these types of poles. Write short note on guarding of over head lines.2 x O. SJBIT Page 44 . if earth-augers are not available a dog pit of the size I. for PCC poles. (Jan-2016) Overhead Line Pole Foundation hole should be drilled in the ground with the use of earth-augers. Where metal works are likely to get corroded ( points where the pole emerges out of the ground ). before the metallic pole is erected. 20 cm above and 20 cm below the ground with sloping top shall be provided. a base plate ( 40 x 40 x 7 cm concrete block ) shall be provided. Cement concrete muff with sloping top may also be provided. when the ground or local conditions call for the same. However. However. Tubular Pole Steel Tubular Poles. The depth of the pit shall be in accordance-with the length of the pole to be planted in the ground as given in respective Indian Standards. stone or steel shall be provided at the bottom of the pit. therefore.Electrical Design Estimation and Costing 10EE82 Unit-7&8 1. 20 cm above and 20 cm below-the ground level.V Line (120m To 160m Span) Department of EEE.6 m should be made in the direction of the line. H. Department of EEE. either double cross arms or disc insulators should be used for HT lines up to 11 kV. For low and medium voltage line.Assume every 8th pole is the Anchor pole.Electrical Design Estimation and Costing 10EE82 The insulators should be attached to the poles directly with the help of ‘D’ type or other suitable clamps in case of vertical configuration of conductors or be attached to the cross arms with the help of pins in case of horizontal configuration Pin insulator:. Step-Up or Primary Substations. and recommended for use on straight runs and up to maximum of 10’ deviation. The disc insulators are intended for use a pole positions having more than 30’ angle or for dead ending of I1 kV lines. Between Disc insulator to Guy Wire=500mm. The substations. 2.59 mm with an average span of 120 mts. Such substations are usually associated with generating stations. (Jan-2016) 3. Classification of Substations on The Basis of Nature of Duties. a bend of 10” to 30’.The conductor used is ACSR of 611 x 2. Between Disc insulator to Disc Insulator=1000mm. is stepped up to primary transmission voltage so that huge blocks of power can be transmitted over long distances to the load centres economically. may be classified into the following three categories: 1. Estimate the quantity of material required for 11 kV feeder running 1. Explain the classification of substations. which is usually low (11 or 33 kV).5 km line using 9 mt RCC poles. on the basis of nature of duties. (Jan-2016) CLASSIFICATION OF SUBSTATlON The substations may be classified in numerous ways such as on the basis of (i) nature of duties (ii) service rendered (iii) operating voltage (iv) importance and (v) design. The generated voltage. SJBIT Page 45 . For lines having=. shackle insulators should be used For Vertical configuration for Conductor erection: Distance between Pole’s Top to Disc insulation=200mm. (DP structure). These are the substations from where bulk power is transmitted from one point to another point in the grid. Such substations are located at suitable load centres along the primary transmission lines.Electrical Design Estimation and Costing 10EE82 2. 2. Department of EEE. In these substations. SJBIT Page 46 . 3. according to operating voltage. 2. At such substations different connections are made between various transmission lines. where the sub-transmission/primary distribution voltage is stepped down to secondary distribution voltage (415/240 V). Switching Substations. Such substations are meant for switching operation of power lines without transforming the voltage. The substations. the primary transmission voltage is stepped down to different suitable secondary voltages. Classification of Substations on The Basis of Service Rendered. Such substations are meant for either converting ac to dc or vice versa or converting frequency from higher to lower or vice versa. Step-Down or Distribution Substations. These are the substations which feed the consumers through distribution network and service lines. The substations. Transformers are installed on such substations transform the power from one voltage level to another level as per needs. Ultra High Voltage Substations (UHV Substations) operating on voltage above 400 kV. 1. High Voltage Substations (HV Substations) involving voltages between 11 kV and 66 kV. Classification of Substations on The Basis of Importance. Converting Substations. Transformer Substations. Grid Substations. These are important because any disturbance in these substations may cause the failure of the grid. may be categorised as. Such substations are located at the load centres. 1. 3. 'l‘he secondary transmission lines are carried over to the secondary substations situated at the load centres where the voltage is further stepped down to sub-transmission or primary distribution voltages. Primary Grid Substations. Classification of Substations on The Basis of Operating Voltage. according to service rendered are: 1. Extra High Voltage Substations (EHV Substations) involving voltages between 132 kV and 400 kV. 3. Draw and estimate material required for 66/11 KV substation with following details:i) Input line 66 KV 2 nos. Town Substations. Classification of Substations on The Basis of Design. SJBIT (Jan-2016) Page 47 . Show the position of isolators or protective devices. conductive dust etc. Outdoor Substations. Department of EEE. Such substations are erected for distribution of power in localities. 1. These substations step-down the voltages at 33/11 kV for further distribution in the towns and any failure in such substations results in the failure of supply for whole of the town. 125 kVA and above 125 kVA (but up to 250 kVA) respectively. These substations are further subdivided into: (a) Pole Mounted Substations.Electrical Design Estimation and Costing 10EE82 2. of 11 KV outgoing lines 2 on each transformer. ii) Transformer 66/11 KV 2 nos of 100 MVA. In such substations the apparatus is installed within the substation building. iii) 4 Nos. 2. 4. Such substations are usually for a voltage up to 11 kV but can be erect/ad for the 33 kV and 66 kV when the surrounding atmosphere i* contaminated with impurities such as metal corroding gases and fumes. Single stout pole or H-pole and 4-pole structures with suitable platforms are employed for transformers of capacity up to 25 kVA. Indoor Type Substations. 66KV grade without earth bus: 1 set iii) Transformer 6300 KVA.Electrical Design Estimation and Costing 10EE82 Material Calculation: a) Equipment on primary side i. 800A. 1250A switch gear with instrument transformer outdoor type 11KV class: 1 set c) Protecting devices and equipments: Department of EEE. 4 sets vi) 300 MVA. 11KV class: 4 set iii) Battery set with charger: 1 set iv) Auxiliary Transformer for station operator 50KVA. 800A. 11KV/440V: 1 Set v) Take of structure on 9 m. SJBIT Page 48 . forced air cooling with on load tap changer: 1 Set b) Equipment on secondary side i.e. 11KV class. 66KV grade complete set with earth set: 1 set ii) GOS. RCC pole.e. 66KV/11KV with oil immersed... 11 kV: i) 11KV class lighting arrestor’s plinth mounted: 6 No’s ii) GOS 400A. 66 kV: i) GOS. List the points to be considered at the time of erection of overhead lines.Electrical Design Estimation and Costing 10EE82 i) Lightning arrestor’s 66KV class: 2 sets ii) Circuit breaker 66KV class: 1 set iii) PT’s 66KV/110KV: 1 set iv) CT’s 800A/5A. As a rule. Sometimes at such crossings there can be problems because of the maximum pylon height allowed for flight safety reasons. 11KV class single core 100mm² for banks: 175 m iii) Cable end and terminals 11KV class single core 1000mm² UG cable: 6 No’s 5. This is usually done by leaving unchanged the line that is crossed. SJBIT Page 49 . vi) Panel for relays and controls for accumulator: 1 No vii) Panel for relays and controls for line: 1 No d) Cable for power control: i) UG cable 11KV class 3 core for feeders 150mm²/240mm²: 300 m ii) UG cable. the two lines must be kept at the necessary safety distances between the lines and the ground. Construction workers try to plan these crossings in such a way that their construction is as economical as possible. (Jun -2015) At crossings of overhead lines by other overhead lines. Department of EEE. and because of its small height it is preferable to create an arrangement with conductors in one level. Undercrossings of existing lines are often constructed in proximity to the line's pylons. the line with the lower voltage passes under the line with higher voltage. 200A/5A: 3 No’s v) Panel for relays and controls for transformer: 1 No. the line running below it will be rebuilt on smaller pylons or replaced with an underground cable. if possible. 400A/5A. If it is not possible at a given location for the pylons of the upper line to be built at a necessary height. since this can often be accomplished without raising the existing pylons and while keeping the necessary safety distances between the ground and the other line. In the course of undercrossings the pylon picture is frequently changed. specially in rural areas. (Jun -2015) Line Supports. i. keeping the cost low. Department of EEE. Write a short note on conductor erection. ii. have life form 25 to 30 years. These poles possess greater mechanical strength and so permit use of longer spans (50-80 m) but cost is higher. The supports used for transmission and distribution of electrical power must have the characteristics-high mechanical strength. have got insulating properties and resistance against chemical action. These give good outlook. very strong and can be used for longer spans (80-200m) and have very long life. The average life of steel poles is more than 40 years. the wooden poles. good looking and easily accessible for painting and erection of line conductors. Steel Poles. need no maintenance. steel. are extensively used for distribution purposes. The steel poles are of three types (i) rail poles (ii) tubular poles and (ii) rolled steel joists. well impregnated with creosote oil or any preservative compound.A pole for an overhead 11KV-3phase . easily available.Make a neat sketch showing how it should be done. low initial as well as maintenance cost. Here crosses the powerline Kincardine-Tealing two other lines.Electrical Design Estimation and Costing 10EE82 A unique undercrossing of two powerlines can be found north of Kincardine at Scotland at 56°5'17"N 3°43'11"W. The line supports are of various types including wood. Wooden Poles. SJBIT Page 50 . These are cheapest. Since these poles are very heavy. providing insulating properties and therefore. 6. longer life. The disadvantage of such supports is that these need periodical inspection because they tend to rot and their life is short. light in weight. Prepare a list of materials required (Jun -2015) 7. RCC Poles. therefore. 50Hz line is to be earthed (pipe) & a stay is to be provided. transportation cost is heavy and require care in handling and erection. Their use is usually limited to low pressures (up to 22 kv) and for short spans (up to 60m). reinforced concrete poles and lattice steel towers. One of the two circuits of Kincardine-Tealing powerline crosses these lines on two small pylons and the other circuit via an underground cable. iii. These towers need periodical painting or galvanizing for protection against corrosion. Conductor materials Properties of Overhead Bare Conductors: Current Carrying Capacity Strength Weight Diameter Corrosion Resistance Creep Rate Thermal Coefficient of Expansion Fatigue Strength Operating Temperature Short Circuit Current/Temperature Thermal Stability Cost Categories of Overhead Conductors: Homogeneous Conductors: Copper AAC( All Aluminum Conductor) AAAC (All Aluminum Alloy Conductor) The core consists of a single strand identical to the outer strands. Since all the strands are the same diameter. These are mechanically stronger and have got longer life. one can show that the innermost layer always consists of 6 strands. yet for tall supports and longer span these prove economical. rivers etc. Due to robust construction long spans (300 m and above) can be used and are much useful for crossing fields. Narrow-base lattice steel towers are used for transmission at 33 kv and broad-base lattice steel towers are used for transmission at 66 kv and above.Electrical Design Estimation and Costing 10EE82 iv. railway lines. Lattic Steel Towers. SJBIT Page 51 . Department of EEE. valleys. Even though these are two to four times costlier than wooden poles. SJBIT Page 52 . or 128 strands. Non Homogeneous Conductors: ACAR (Aluminum Conductor Alloy Reinforced) ACSR (Aluminum Conductor Steel Reinforced) ACSS (Aluminum Conductor Steel Supported) AACSR (Aluminum Alloy Conductor Steel Reinforced. 19. 91. etc. Within the core or within the outer layers. 37.. the strands in the core may or may not be of the same diameter.Electrical Design Estimation and Costing 10EE82 the second layer of 12 strands. however. in 26/7 ACSR. making conductors having 1. 7. 61. Thus. the number of strands always increases by 6 in each succeeding layer. In a 30/7 ACSR conductor the aluminum and steel strands are of the same diameter. the number of layers in the inner layer of aluminum is 10 and in the outer layer 16 Categories of Overhead Conductors VR (Vibration Resistance) Non-Specular ACSR / SD (Self Damping) Choices of overhead depend upon: Power Delivery Requirements Current Carrying Capacity Electrical Losses Line Design Requirements Distances to be Spanned Sag and Clearance Requirements Environmental Considerations Department of EEE. In a 30/19 ACSR they are not. Advantages of Outdoor Substation (AIS): Department of EEE. Size of switchyard is similar to AIS Substation. Make a neat sketch showing how it should be done. (Jan -2015) Air Insulated Substation (AIS) or Outdoor Substations have all switchgear equipment. 3-Ohase. Substation with SF6 enclosed modules (Gas Insulated Substation) in building which takes about 10% of the total AIS substation space Because of excellent properties of SF6 gas such as high dielectric strength. Indoorsubstations are of two types Substation with conventional switchgear equipment enclosed in big building. less space requirement and less maintenance. high electronegativity. for EHV substations more than 230kV now a days Indoor Gas Insulated Substations (GIS) are employed in place of AIS substations.Electrical Design Estimation and Costing Ice and Wind Loading Ambient Temperatures 10EE82 8. Prepare a list of materials required. In earlier days for any voltage ratings AIS or outdoor substation is employed. A pole for an overhead 11KV . Some of the advantages and disadvantages of outdoor switchyard is discussed below. SJBIT Page 53 . 50Hz live is required to be earthed (pipe) & a stay is to be provided . Indoor Substation type is only employed in places where high pollution or saline environment exists. Write short notes on indoor ss? List advantages and disadvantages of outdoor ss over indoor ss. busbars and other switchyard equipment installed outside open to atmosphere. However the cost of GIS indoor substation is higher compared to AIS substation but it has some benefits which includes high reliability. (Jan -2015) 9. Electrical Design Estimation and Costing 10EE82 This type of substation arrangement is best suited for low voltage rating substations (step down substations) and for those substations where there is ample amount of space available for commissioning the equipment of the substation The construction work required is comparatively less to indoor switch yard and the cost of switchgear installation is also low In future the extension of the substation installation is easier The time required for the erection of air insulated substation is less compared to indoor substation All the equipment in AIS switch yard is within view and therefore the fault location is easier and related repairing work is also easy There is practically no danger of the fault which appears at one point being propagated to another point for the substation installation because the equipment of the adjoining connections can be spaced liberally without any appreciable increase in the cost Disadvantages of Air Insulated Substation (AIS): More space is required for outdoor substation when compared to indoor gas insulated substation (GIS) Outdoor switch yards are more vulnerable to faults as it is located in outside atmosphere which has some influence from pollution. They are also vulnerable to direct lightning strikes and other external events such as heavy winds. Deposition of saline particles on insulators can cause insulator failures. rains and cyclones. SJBIT Page 54 . saline environment and other environmental factors. Therefore reliability wise air insulated substation or outdoor substations are relatively low compared to indoor substation Regular maintenance is required compared to indoor substations (Maintenance for Gas Insulated Substation is very minimal and reliability is very high) as they are exposed to outside environment Department of EEE. 33/4 kV 250 kVA Control Panel a). 33 kV tripple feeder panel U/F Relay Panel Energy meter 0. 33 kV Tendom Isolators 132 kV CTs a).Electrical Design Estimation and Costing 10EE82 10. 132 kV b). 33 kV Line Isolators a). Double feeder panel d).2 acc. 132 kV CVT b). 33 kV PT LA (Lightining Arrestors) a). 132/33 kV. fencing. B/C Panel c). 132 kV b). 132 kV b). Distance protection panel e). 33 kV a). 33 kV Bus Isolators a). Estimate the quantity of material required for installation of 132/32KV ss with main & transfer bus scheme having 2 x 40MVA Transformers (Jan -2015) SL No Equipments Quantity Unit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 16 17 18 19 20 21 22 a). T/F control and relay panel b). 33 kV Post Insulator Transformers a). SJBIT Page 55 . Cla(ABT) Control and Power Cable Structures DC equipments ( Protection & Conn) Bus Bar and Insulator S/S and Control Room Lighting Earthmat and Earthing Firefighting equipment Boundary wall. Land (Subject to Actual) 11 2 10 8 15 4 12 33 9 6 12 12 92 2 1 2 1 1 2 3 1 1 LS Provision 60 1 1 (LS Provision) nos do do do do do do do do do do do do do do do do do do do do do MT set Department of EEE. Control room building Store shed etc. 132 kV b). 40 MVA b). 132 kV b). It is the clearance between the operating rode of the AB switch and the jumpers of 11 kV down conductors • The supported length of 11 kV jumpers shall be limited to 1. 10EE82 (Jun-2014) On the basis of design substations may be classified in to (a)Outdoor type i. SJBIT Page 56 . • Phase to phase clearance at the AB switch shall be 915 mm • Phase to earth clearance at the AB switch shall be 610 mm. certain clearances must be maintained. • Clearance between supplier’s and consumer’s structure should not be less than 333 meters.44 m for solid conductors (No. • Where there is a cable end box with open terminations. 100 kVA and above 100 kVA) ii. the clearance of the live pars to ground shall not be less than 305 m • The ground clearance of ht parts. Department of EEE.5 m for standard conductors and 2. Explain the classification of substations. Pole mounted (single stout pole/ H-type/ 4-pole structure employed for transformers of 25 kVA. usually 11 kV at the transformer bushings shall not be less than 2. • The ground clearance of the live parts of CTPT unit shall not be less than 3.75 m. This is for maintaining the minimum sectional clearance of 206 m at 11 kV.7 m.Electrical Design Estimation and Costing 11. 2 or No. 0 SWG copper). • Supplier’s and consumer’s structure shall be braced together when the clearance between them is 5 m or less. Foundation mounted (For transformers above 250 kVA and voltage of 33 kV and above (b) Indoor type (In this the substation apparatus are installed within the building) Outdoor substation : When transformers are installed out door. SJBIT (Jun-2014) Page 57 .66Kv iii) Output line-0. Both sides of the transformer are protected by suitable capacity CB. Adequate fire fitting equipment shall be provided at easily accessible positions. so as to give adequate clearance between wall and various equipments. LA and DO fuse are installed in the DP structure. having 66KV ii)Output line-2.Electrical Design Estimation and Costing 10EE82 • The ground clearance of AB switch handle shall be between 1 and 1. The installation of transformer should that the cable boxes are on the sides and not facing the door. Danger notice board should be provided on the HV and MV equipments. with foll details : i) Input lines-2. CT PT unit is installed for connecting metering device. 6 numbers. telephone exchange etc. 12. Room size should be sufficient. Substation building is constructed for installing transformer. Suitable ventilation for entry of fresh air at the bottom of transformer room and exit of hot air at top on opposite sides are necessary. All protection accessories such as AB switch. The OH line terminates on a DP structure outside the indoor substation.2 m Indoor Substation : Indoor substation of 11 kV/415 V are usually installed at industrial areas and other load areas like multistoried buildings. Supply to HT side of transformer is brought through UG cable. Draw and estimate materials required for 66/11KV substation.11KV Department of EEE. HT and LT panel etc. SJBIT Page 58 . First Circuit: Load current = 780/230 = 3. bed room and kitchen = 780 watts. Length of Casing and Capping Department of EEE. Factor of safety = 2.82 A. Second Circuit: Room. Second Circuit: Load current = 325/230 = 1. Inner Verandah. two circuits are used. Therefore 1/18 PVC or VIR copper wire is suitable.Electrical Design Estimation and Costing 10EE82 Material calculation for lighting: As the lighting load is more than 800 watts.41 A. lavatory and bath = 325 watts. hall. Current to be observed in wire table = 3. First Circuit: Verandah. Therefore 3/22 PVC or VIR Copper wire suitable. Current to be observed in wire table = 1.39 x 2 = 6.39 A. Factor of safety = 2.78 A.41 x 2 = 2.
Report "Eee-Viii-electrical Design Estimation and Costing 10ee81 -Solution"