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10. 1.2/50 micro seconds impulse 325 kV (Peak) 170 kV (Peak) 75 kV (Peak)wave withstand test voltage11. One minute power frequency 2 kV 2 kV 2 kVwithstand test voltage onsecondary12. 3 second short time current As per IS: 3156 As per IS: 3156 12.5 kArelay13. Dynamic Rating As per IS: 3156 As per IS: 3156 2.5 times14. Minimum creepage distance ofbushings (based onAs per Para 2.5 of section 1environment)5.2 Temperature Risea) 36 kV & AboveThe maximum temperature of the windings, cores etc. should not exceed 45C overambient, while max. temperature of oil at top should not exceed 35C over ambient. ThePTs should be suitable for mounting on steel structures. All nuts, bolts, flanges and baseshould be hot dip galvanized. The terminal connectors should be such as to give intimatecontact between conductor & terminal and offer protection against and effects ofelectrolytic and atmospheric corrosion and should also have sufficient mechanicalstrength. The connectors should conform IS 5556: 1970. The junction boxes should besuitable for terminating all the connections of the PTs secondaries with other equipmentsof the power station 400V grade terminal connectors of 15 Amp (continuous) currentrating should be provided.b) 12 kVWhen tested in accordance with IS: 3156, the temperature rise of the windings shall notexceed the following *table 2.5.2) limits:Class E insulationClass B insulationClass F insulation50 0 C600 0 C85 0 CNote: Maximum ambient temperature shall be taken as 65 0 C5.3 11 kV Voltage TransformerThe tank shall be given three coats of rust preventing paint. The other iron parts shall behot dip galvanized. The tank shall be provided with lifting lugs either welded on the sidesor top cover plate of the tank.The dimensions and electrical characteristics of the 11 kV bushings shall be inaccordance with IS: 2099-1986 or its latest version.2-12
The tank shall be provided with two separate earthing terminals.The unit shall have rating and diagram plate and will have suitable base channels tofacilitate mounting of the equipment on the structure.Terminals: The voltage transformers shall be provided with bolted type terminals on the11 kV side to receive ACSR conductors upto 8 mm dia (without requiring use of lugs)both in vertical and horizontal directions. The terminals shall be such as to avoidbimetallic action.Indoor TypeThe voltage transformer shall be of resin-cast type suitable for indoor installation andshall be normally mounted on one of the 12 kV incoming circuit breakers.5.4 Coupling Voltage Transformer (36 kV & Above)These transformers should be suitable for use on transmission line to pass through thecarrier frequencies for communication and low voltage for protection and metering. Thesingle phase CVTs should be of suitable ratio (say 66 kV/√3/110V/√3 for 66 kV line)suitable for outdoor installation on steel structures. The equipment should be suppliedwith terminal connectors suitable for vertical take off from line conductor and hot dipgalvanized base fasteners. Other details should be in accordance with the specificationsfor potential transformers. The secondary terminals should be provided duly marked forabove requirements.The wave traps should hanged underneath feeder bay structure. The carrier frequenciesand wave trap capacity should be decided in accordance with the other ends of thetransmission lines terminating at sub station.6.0 TransformersSelection of power transformer is discussed in section 3. Layout of transformer isdiscussed as it is the largest piece of equipment in a substation and it is, therefore,important from the point of view of handling and station layout. In small hydro stationstransformer are installed in the switchyard and the bay width is determined bytransformer dimensions. Handling of transformer is normally done by the powerhousecrane and for large transformer rails are laid from powerhouse to the site of installation inswitchyard. For this purpose bi-directional rollers are provided on the transformers.Arrangement for removal of transformer in case of repair/maintenance without disturbingother equipment is required and also affects layout. In order to reduce the chances ofspread of fire, transformers are provided with a soaking pit of adequate capacity tocontain the total quantity of oil. Sometimes where feasible drainage arrangements areprovided to drain the oil away from the transformers in case of fire. Besides, separationwall are provided in between the transformers and also between the transformer androads within the substation.2-13
Page 2 and 3: Section -1Guide for Design of Outdo
Page 4 and 5: The terms atmospheric overvoltages
Page 6 and 7: Table 2.31. Basic Data Example 1.Hi
Page 8 and 9: Spark gaps specified for fitting to
Page 10 and 11: 2.4.2 Working Safety Clearances125
Page 12 and 13: Highest System Voltage rating kV Sp
Page 14 and 15: 2.6 Insulator TypeTypes of insulato
Page 16 and 17: Bending .. .. 1265 kg/sq.cm.Shear .
Page 18 and 19: v) Installations in difficult site
Page 20 and 21: During maintenance, it is essential
Page 22 and 23: Areva Compact Air Insulated Substat
Page 24 and 25: The bus bar sizes should meet the e
Page 26 and 27: disconnect switch contacts in such
Page 28 and 29: (iv)Electro magnetic type interlock
Page 30 and 31: ) Temperature rise of 11 kV Class C
Page 32 and 33: 4.6 TestsThe CTs shall be provided
Page 36: 7.0 Lightning ArrestorsLightning ar
Page 39 and 40: and this aspect has to be kept in m
Page 41 and 42: Fig. 12.1: Layout of 12 kV Agnoor S
Page 43 and 44: Fig. 12.4 Layout of 72.5 kV Switchy
Page 45 and 46: 464006800 7600 3000LA30002000 2000X
Page 47 and 48: Fig. 12.6:145 kV Outdoor Switchyard
Page 49 and 50: Fig. 12.7: 245 kV Outdoor Switchyar
Page 51 and 52: 2-20
Page 53 and 54: 3.0 Transformer RatingThe full load
Page 55 and 56: OFAFOil Immersed with forced oil ci
Page 57 and 58: The transformer may be operated wit
Page 59 and 60: 8.10 Parallel OperationThe transfor
Page 61 and 62: (a)(b)33 kV Transformers (MVA)1.001
Page 63 and 64: (e)(f)(g)(h)(i)(j)(k)(l)(m)(n)(o)(p
Page 65 and 66: 18.0 Oil Containment and Fire Prote
Page 67 and 68: ) The limits of temperature rise me
Page 69 and 70: Example Calculation -1Generator Tra
Page 71 and 72: TRANSFORMER RATING AND CHARACTERSTI
Page 73 and 74: 3.0 Type of Circuit BreakerFollowin
Page 75 and 76: iii) during arcing of SF6 breaker,
Page 77 and 78: 3.4 Protection Classes for Switchge
Page 79 and 80: The rated voltage is expressed in k
Page 81 and 82: 5.7 Rated Short Circuit Making Curr
Page 83 and 84: Effect of circuit conditions on rec
Page 85 and 86:
5.17 Rated time quantities and oper
Page 87 and 88:
25405017.5 812.516254024 812.516254
Page 89 and 90:
component of fault current in addit
Page 91 and 92:
Steps involved in applying method a
Page 93 and 94:
to earthxvii. Difference in the ins
Page 95 and 96:
Datai) Sub transient reactance of g
Page 97 and 98:
Annexure-1Current waveAA = envelop
Page 99:
Annexure-3Fig. 3.3 Arc extinction4-
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