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Annexure-3.1Ambient temperature & temperature rise for Mukerian Stage II Generatortransformer 11/66 kV class rated 10/12.5 MVA and 6.6/33 kVclass transformer for Sikasar Project Generator Transformer3.3/33 kV class rated 2 x 3.5 MWA. Reference Ambient TemperaturesThe reference ambient temperatures for which the transformers are to be designed are asunder:-i) Maximum ambient temperature 50 degree Cii) Maximum daily average ambient temp : 40 degree Ciii) Maximum yearly weighted average ambient temp : 40 degree Civ) Minimum ambient air temperature : ;(Cooling Minus 5 degreemedium shall be Air)CB. CLIMATIC CONDITIONS :i) Maximum relative humidity 100%ii) Yearly average number of thunder storms _______varies from 30 to 50 .iii) Average no. of rainy days per annum 60 daysiv) Fog : The atmosphere is subject to fog for two monthin winter.v) Number of months during which tropical monsoon 3 monthsconditions prevailvi) Dust storms occur at frequent intervalsvii) Average annual rainfall 60 cmsviii) Maximum wind pressure150 kg/sq.m.B. ALTITUDEAltitude above M.S. level not exceeding 1000 mtrs.C. TEMPERATURE RISE , OVER LOAD CAPACITY & CONTINUOUS RATINGa) With the above service conditions, given in clause-6.4 each transformer shall be capableof operating continuously on any tap at normal rating without exceeding followingtemperature rises, over maximum ambient temperature of 50 deg. C.i) 30 deg. C in oil by thermometerii) 45 deg. C in winding by resistanceiii) The temp. of hot spot in the winding not to exceed 90 deg. C when calculatedover max. annual weighted average temp. of 40 deg. C & 105 deg. C at worstambient of 50 deg. C.3-15
) The limits of temperature rise mentioned above and over load capacity as per IEC-354(1993) will have to be satisfied by the manufacturer by carrying out the heat run test atthe lowest negative tap. This test shall be carried out by feeding the following losses: -(Total max. losses at 75 deg. C at highest current tap) x 1.1c) The safe overload capacity of the transformer and the duration of overload for each typeof cooling (ONAN/ONAF/ ) under maximum temperature conditions (Clause 6.5 above )without any damage to the winding or harmful effects on the insulation shall be clearlystated in the tender, which must be as per IEC-354 (1993) – Guide for loading of oilimmersed transformers, suitable for climatic conditions given in clause-6.4 above.d) The transformer may be operated without exceeding temperature rises, winding gradientsand hot spot at any particular tapping at the rated MVA provided that the voltage does notvary by more than 10% of the voltage corresponding to that tappings. Transformer shallbe able to withstand for 30 minutes after achieving steady state at full load rating withoutinjurious heating to winding/insulation etc. under auxiliary failure condition.3-16
Page 2 and 3:
Section -1Guide for Design of Outdo
Page 4 and 5:
The terms atmospheric overvoltages
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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
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Highest System Voltage rating kV Sp
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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 34 and 35: 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: 18.0 Oil Containment and Fire Prote
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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