standards / manuals / guidelines for small hydro development - AHEC

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5.0 Cooling12.5 66/11 ONAN/ONAF20.0 66/11 ONAN/ONAFTable 1 (D) 132 kV Class Two Winding TransformersThrees phase power rating Voltage ratio kV CoolingMVA16 132/11 ONAN/ONAF25 132/11 ONAN/ONAF31.5 132/11 ONAN/ONAFTransformer cooling system for generator transformers specified table 2.4 (A,B & C) inaccordance with IS: 2026 (part II) are identified according to the cooling methodemployed. Letter symbols used in the table are as follows:.(i) Cooling Medium Symbola. Mineral oil or equivalent flammable Osynthetic insulating liquidb. Air A(ii)Kind of Circulationa. Natural Nb. Forced (oil not directed) FTransformer is identified by four symbols for each cooling method for which a rating isassigned by the manufacturer.1 st Letter 2 nd Letter 3 rd Letter 4 th LetterKind of cooling Kind of circulation Kind of cooling Kind of circulationmedium indicatingmedium indicatingthe cooling that isthe coolingin contact with thewindingsmedium that is incontact with theexternal coolingsystemsFollowing cooling systems are used in hydroelectric stations upto 25 MVA capacitySymbolONANONAFOil Immersed Natural Air CooledOil Immersed Forced Air Cooled3-3
OFAFOil Immersed with forced oil circulation Forced Air CooledTransformers when located in powerhouse should be sited so that unrestricted ambient aircirculation is allowed. The maximum transformer rating should match maximumgenerator rating with forced cooling in dual rating transformers, which are commonlyemployed. The rating of these dual rated transformers is usually as follows:ONAN/OFAFONAN - 60%OFAF - 100%The rating under ONAF condition although not guaranteed should be about 80%.Standby cooling capacity should be provided for different type of forced cooling asfollows as per Central Board of Irrigation and Power Manual on Transformer.ONAN/OFAF-2 – 50% group2 – 100% pump of which one will be standby,2 – Standby fans one in each 50% groupOr3 – 50% group with independent pump andfans out of which one group to act as standby.6.0 Temperature Rise, Overload Capacity And Continuous RatingConservative value of temperature rise, overload capacity and continuous rating oftransformer located in the switchyard should be specified. For the purpose ofstandardization of maximum temperature rise of oil and windings, the following ambienttemperatures are recommended by CBI & P.Cooling mediumMaximum ambient temperatureMaximum daily average ambient temperatureMaximum yearly weighted average temperature: Air: 50 0 C: 40 0 C: 32 0 CWith the above ambient temperature condition the temperature rises for powertransformers as per CBI & P are as given below:Oil 0 CWinding 0 C50 55However more conservative temperature rise are specified for generator, transformers.Reference ambient temperatures and climatic conditions and temperature rise specifiedfor generators transformer at Mukerian stage II in Punjab given in Annexure 3.1.3-4
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 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: 3.0 Transformer RatingThe full load
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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