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Fig. 3.6 Reclosing – Close Open Reclose TimeThe rated interrupting time of a circuit breaker is the maximum permissible intervalbetween the energization of the trip circuit at rated control voltage and rated mechanismpressure and the interruption of the current in the main circuit in all poles. It is used toclassify breakers of different speed.For line-to-ground faults, the interrupting time is estimated to exceed the ratedinterrupting time by 0.1 cycle. For asymmetrical faults, it is estimated that theinterrupting time may exceed rated time by an additional 0.2 cycle. Hence, for groundedasymmetrical faults, the last phase to clear is estimated to be 0.3 cycle slower than therated interrupting time. Additionally, rated interrupting time may be exceeded duringextreme cold weather or when the breaker has been closed for an extended period of time.Also, the breaker may be slower at the lower limits of control voltage and/or mechanismstored energy. These interrupting times are in the range of several milliseconds havesystem stability implications.The rated interrupting time may be exceeded for close-open operations. The increase ininterrupting time on close-open operation may be important from the standpoint ofpossible system instability. For low values of current, these considerations are lessimportant.6.0 Co-ordination of rated valuesCo-ordination of rated voltages, short circuit breaking current and rated normal currentfor guidance as per IS 13118 for rated voltage 33 kV and above as commonly used are asfollows. (Table 3.4).Table 3.4Ratedvoltage(kV)3.6 101625407.2 812.516256012 812.516Rated shortcircuitbreakingcurrent (kA)400400400 630630630400400 630630630 125012501250Rated normal current (A)12501250125012501600160016001600160012501250 160025002500 400025002500 40004-15
25405017.5 812.516254024 812.5162540400 630630630630 12501250125063063063016001600160025002500250012501250125012501250 1600 250012501250125016001600160025002500 400036 812.516254052 812.52072.5 12.5162031.5145 12.5202531.54050245 2031.54050630630630800 125012501250125012501250800800800160016001600160016001600160012501250125016001600160012501250 1600 2000125012501250 1600 20001250 1600 20002000200020002000200020002000200020003150315031503150315025002500 40007.0 Tests7.1 Type TestFollowing type tests as applicable in accordance with IS 13118 and IEC 56 arerecommended to determine adequacy of the circuit breaker.i) Dielectric tests (1.2/50 micro second lightning impulse withstand) and 1 minutepower frequency voltage with stand (dry & wet) test4-16
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Section -1Guide for Design of Outdo
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The terms atmospheric overvoltages
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Table 2.31. Basic Data Example 1.Hi
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Spark gaps specified for fitting to
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2.4.2 Working Safety Clearances125
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Highest System Voltage rating kV Sp
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2.6 Insulator TypeTypes of insulato
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Bending .. .. 1265 kg/sq.cm.Shear .
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v) Installations in difficult site
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During maintenance, it is essential
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Areva Compact Air Insulated Substat
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The bus bar sizes should meet the e
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disconnect switch contacts in such
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(iv)Electro magnetic type interlock
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) Temperature rise of 11 kV Class C
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4.6 TestsThe CTs shall be provided
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10. 1.2/50 micro seconds impulse 32
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: 5.17 Rated time quantities and oper
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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