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Note 1Terminal Arrangement: The tope metal cap and the base of the lightning arrestors shallbe galvanized. The line terminal shall have a built-in-clamping device which can beadjusted for both horizontal and vertical take off to suit ACSR (conductor size to bespecified by the purchaser). The base of the lightning arrestors shall be provided with twoseparate terminals distinctly marked for connection to earth.Sealing: The arrestors shall be hermetically sealed to avoid ingress of moisture. Suitablerubber gaskets with effective sealing system should be used. Manufacturers should devicea suitable routine production testing to verify the efficiency of sealing.Disconnective Device: The arrestors for 11 kV system may be provided with a suitabledisconnecting device. This shall be connected in series with the ground lead and shouldnot affect the sealing system of the arrestors. The disconnecting device shall conform tothe requirements specified in IS: 3070 (Part – 2) – 1985.Pressure Relief Device: The arrestors for 33 kV and 66 kV system should have asuitable pressure relief system in order to avoid damage to its porcelain housing.7.2 Lightning ProtectionA substation has to be shielded against direct lightning strokes by provision of overheadearth wires or spikes. This equipment is essential irrespective of the isoceraunic level ofthe area due to .serious consequences and damage to costly equipment in case substationis hit by a direct stroke. The choice between these two methods depends upon severalfactors economy being the most important consideration. Both the methods have beenused sometimes even in the same station. Generally, the spikes method involves tallerstructures than the alternative of using earth wires. Another method' comprises the use ofseparate lightning masts which are provided at location determined on the basis of substation area and height of bus-bars. - Besides providing lightning protection, these mastsserve as supports for luminaires required for switchyard illumination. Spikes and theearth-wire .have to be suitably placed so as to provide coverage to the entire substationequipment. Generally an angle of shield of about 45° for the area between ground wiresand, 30° for other areas is considered adequate for the design of lightning protectionsystem.7.3 InsulatorsProvision of adequate insulation in a substation is of primary importance from the pointof view of reliability of supply and safety of personnel. However, the station designshould be so evolved that the quantity of insulators required is the minimumcommensurate with the security of supply. An important consideration in determining theinsulation in a substation, particularly if it is located near sea or a thermal powergenerating station or an industrial plant is the level of pollution. As a first step to combatthis problem, special insulators with higher leakage distance should be used. In case thisdoes not suffice, washing the insulators by using live line equipment has to be resorted to2-16
and this aspect has to be kept in mind while deciding the layout of the substation.Another method which has proved to be successful in other countries involves theapplication of suitable type of greases or compounds on the surface of the insulators.This, however, also requires cleaning of insulation, the frequency depending upon thedegree and the type of pollution.8.0 Equipment for Communication, Relaying and Tele Metering and Off-site ControlFollowing types of equipments may be used for the purpose.i) Carrier Equipmentii) Microwaveiii) VHF wirelessiv) Dedicated fibre optic cableVHF equipment is normally recommended for 33 kV systems. Fibre optic cable isrecommended when offsite control is provided.The carrier equipment required for communication, relaying and Tele metering isconnected to line through coupling capacitor and wave trap. The wave trap installed atthe line entrance. The coupling capacitors are installed on the line side of the wave trapand are normally base mounted.Economic study for Microwave transmission for the purpose is required.9.0 AuxiliariesBesides the main equipment a number of auxiliary facilities and system as enumeratedbelow have to be provided. These are discussed alongwith auxiliaries for the powerhouse.In step-up substations most of the facilities are provided in the powerhouse.a) Earthing and Grounding – Steel grounding system is provided for earthmat andinterconnectionb) Oil Handling System – portable oil purification system is providedc) Illumination and lighting system – illumination system is discussed withauxiliaries systemd) Compressed air system – is required for cleaning etc. and provided in thepowerhousee) Fire protection system – All substations should be equipped with fire lightingsystems conforming to the requirements given in latest IS: 1646 and Fireprotection manual Part –I issued by Tariff Advisory Committee of InsuranceCompanies.f) AC Auxiliary power system – is provided in the power houseg) DC system is provided in the powerhouseh) Cables – discussed in powerhouse electrical auxiliaries2-17
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 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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