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Section –1Guide for Design of Outdoor Step up Sub-Stationand Selection of Equipment1 IntroductionOutdoor step up substation at hydroelectric stations are provided to step up power atgenerated voltage generally for interconnection with the grid to evacuate power.Generation voltage in SHP varies from 415 volts to 11 kV and step up voltage of smallhydro upto 25 MW capacity may not exceed 145 kV. Guidelines for design and selectionof comprises of main equipment, ancillary equipment, switchyard structures and substation layout.2. Design RequirementsReferences and CodesLatest edition of the following shall apply.IS: 9920 Part I to IV – Alternating current switches for rated voltages above 1000 voltsand less than 52 kVIS: 9921Part 1 to 5 – Alternating currents disconnectors (isolators) and earthing switchesrating, design, construction, tests etc.IS: 1893 – Criteria for Earthquake resistance design of structuresIS: 2705 Part 1 to 4 – Current transformerIS: 3156 Part 1 to 4 – voltage transformerIS: 3070 part 1 to 3 – Lightning arrestorsIS: 2544 – Porcelain insulators for system above 1000 VIS: 5350 – Part III – post insulator units for systems greater than 1000 VIS: 5621 – Hollow Insulators for use in electrical equipmentIS: 5556 – Serrated lock washers – specificationIS: 3716 – Application guide for insulation co-ordinationIS: 2165 – Phase to earth insulation co-ordinationRural electrification Corporation (REC) specification and standardsPower Engineers Hand Book - Tamil Nadu Engineer’s AssociationCentral Board of Irrigation and Power - Manual on Sub-Station LayoutUPSEB - Construction Manual for Rural Electrification and secondary system planning2.1 GeneralThe equipment shall be designed and manufactured to provide most optimum functionalvalue and neat appearance. All major assemblies or equipment shall be designedto facilitate easy and quick surveillance, maintenance and optimum operation. Allcontrol sequences shall be simple and rational.1-1
All live, moving and rotating parts shall be adequately secured in order to avoid dangerto the operating staff. All electrical components shall be electrically earthed.Suitable lifting eyes and forcing off bolts shall be provided where required or wherethey will be useful for erection and dismantling.2.2 Seismic ConsiderationForces caused by earthquake which may occur for the seismic intensity of the zoneconcerned should be taken into account. Stresses resulting after including these loadsshould not exceed permissible stresses. For Himalayan region projects it may be specifiedas under:-Switchyard equipment and structure be designed to safely withstand earthquakeacceleration force 0.3g both in the vertical and horizontal direction.For other regions refer IS: 1893.2.3 Basic Insulation Level and Insulation Co-ordinationInsulation coordination is the correlation of the insulation of electrical equipment andsystem with the characteristics of protective devices such that the insulation is protectedfrom excessive over voltages. Thus in a substation the insulation of transformer, circuitbreakers, bus supports, etc. should have insulation strength in excess of the voltage levelsthat can be provided by protective equipment such as lightning arrestors and gaps.According to International Electro Technical Commission Technical Committee No. 28on Insulation Coordination the same is defined as follows by IEC:“Insulation coordination comprises the selection of the electricstrength of equipment and its application in relation to the voltageswhich can appear on the system for which the equipment is intendedand taking into account the characteristics of available protectivedevices, so as to reduce to an economically and operationallyacceptable level the probability that the resulting voltage stresses willcause damage to equipment insulation or affect the continuity ofservice”.2.3.1 Over-voltages: The selection of basic insulation level for various components ofswitchyard equipment and its coordination is based on the extent of different types ofover voltages and dielectric stresses on insulation of the equipment. Overvoltages areclassified as follows (IS: 3716).(i)(ii)(iii)(iv)Power frequency voltages under normal operating conditionsTemporary OvervoltagesSwitching overvoltagesAtmospheric or Lightning overvoltages1-2
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 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
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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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