standards / manuals / guidelines for small hydro development - AHEC

More documents

Recommendations

Info

The terms atmospheric overvoltages and switching overvoltages are defined bythemselves. The term temporary overvoltages means overvoltages essentially of powerfrequency or a frequency close to it. Switching overvoltages are of consequence only atlevels above 220 kV and not applicable to system under consideration. The protectionagainst overvoltages is essentially made by Surge diverters (lighting arrestors). Lightningimpulse wave is defined as time in microsecond for the wave to reach crest (1.2 microsecond) followed by the time in microsecond for the wave to reach half magnitude (50micro second). This has been standardized in the test forms to establish insulation levelon a common basis.2.3.2 Selection of basic Impulse Insulation Level (BIL): Equipment insulation mustwithstand temporary overvoltages and protected against lightning by suitable lightningarrestor. The basic impulse insulation level should be selected which can be protectedwith a suitable lightning protective device. The best protection is provided by moderntype (gapless) lightning arrestors. The spread margin between the BIL and the protectivedevice, allowing for manufacturing tolerance, is an economic consideration that mustbalance the chances of insulation failure against the cost of greater insulation strength.When using lightning arrestors the economic factor may be one of greater risk to thearrestor than to the equipment insulation. The arrestor can be applied so that it willprotect the insulation but may under certain extreme conditions, usually unlikely, besubjected to sustained rms temporary over voltages against which it cannot recover.Practice has been to apply arrestors so that they have an rms voltage rating above themaximum possible rms line-to-neutral power frequency voltage under any normal orexpected fault condition with sufficient margin. The BIL of the equipment insulationmust therefore be higher than the maximum expected surge voltage across the selectedarrestors selected to withstand highest credible temporary overvotage.2.3.3 Station Design for Lightning and Standardisation of Insulation Levels: Stationdesign for lightning involves in general, provisions of an adequate insulation level for allequipment and protective measures to prevent, as for as possible lightning overvoltagesapproaching that level from appearing on station lines or on equipment. These levels aregiven in table 2.1 & 2.2 as per the Indian Standard IS: 2165. In this standard, table 2.1covers the standard insulation levels highest system voltages of 52 kV and below andTable 2.2 for highest system voltages of more than 52 kV and less than 300 kV.Table 2.1: Standard Insulation Levels for (equipment in range A 1 kV for preferred valueHighestVoltage forEquipmentU mRated Lightning ImpulseWithstand Voltage (Peak)Rated Short Duration PowerFrequency Withstand Voltage (rms)List 1List2kV kV kV kV3.6 20 40 107.2 40 60 201-3
12 60 75 2824 85 125 5035 145 170 70Note: Insulation levels as per list 2 are recommended.For SHP application where temporary overvoltages are high due to speed rise on loadthrow off equipment insulation as per list 2 of table 2.1 should be used.Standard Phase-to-Phase Insulation Levels for 52 kV ≤ U m < 145 kV (IS: 2165)Table 2.2Highest Voltage Base for P.U. Rated Lightning Rated Shortfor Equipment Values Impulse Withstand Duration Power-FrequencyWithstand VoltageU m U m 2 / 3(rms) (peak) (peak) (rms)kV kV kV kV72.5 59 325 140123 100 450550185230145 118 (450)*550650(230)*230275245 200 650*750*8509501050360*360*360395460Generator transformer/step up transformer in SHP are liable to be subjected to hightemporary overvoltages due to load rejection, as well as line capacitance which mayremain connected on interconnecting tie line in case of receiving end breaker opening.Basic insulation level on power frequency overvoltages of 1.5 per unit for transformers isworked out in table 2.3 for a typical 145 kV transformer.In case of generator transformer in SHP 90 – 95 % lightning arrestors are recommended.An increase of impulse level of 15% above the withstand level to earth is recommendedfor disconnecting switches between the terminals of each pole in the open condition. Acorresponding increase of distance may be applied for distances between phases for busbars and connections, or between connections which may be located on opposite sides ofan open disconnecting switch.1-4
Page 2 and 3: Section -1Guide for Design of Outdo
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 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-
show all

standards / manuals / guidelines for small hydro development - AHEC

Create successful ePaper yourself

Delete template?

Save as template?