standards / manuals / guidelines for small hydro development - AHEC

depends upon site conditions e.g. for 2 x 10 M Mukerian SHP 72.5 kV switchyard(Punjab Plains), it was specified as follows and is recommended for similar breakers.i) Reference ambient temperature in shade = 50 0 Cii) Reference temperature under direct rays = 60 0 Cof the sun for limiting temperature riseas per IS: 99213.2 RatingEach isolating switch should have the following particulars (table 2.3.2) under the siteconditions for the system under design.Table 2.3.21. Highest system voltage 72.5 kV 36 kV 12 kV2. Rated frequency (cycle/second) 50 c/s 50 c/s 50 c/s3. Rated lightning impulse withstand voltage (withoutarcing horn)i) To earth and between poles (kV Peak)ii) Across the isolating distance (kV peak)4. Rated one-minute power frequency wet withstandvoltagei) To earth and between poles (kV rms)ii) Across the isolating distance (kV rms)Voltage against ground and between poles2-3325 kV(+ ve & - ve waveto earth &between poles)140 kV(against ground &between poles)170 kV195 kV70 kV80 kV75 kV85 kV28 kV32 kV5. Continuous rated current (Amps) 1600 A 630 A 400 A6. Short time current ratingsi) For one second not less than kA (rms) 20 kA16 kA 16 kAii) For 3 secondsTo be stated To be To be7. Rated peak withstand current kA (peak) in closedpositionstated statedTo be stated 40 kA 40 kA8. Transformer off-load breaking capacity A (rms) To be stated 6.3 kA 6.3 kA9. Line charging capacity A (rms) To be stated 6.3 A 2.5 A10. Rated DC voltage for auxiliary circuits A (rms) To be stated11. Rated supply frequency and voltage of AC operatingdevicesIsolators 36 kV and 12 kV: should conform to IS: 9920Isolated 72.5 kV & above should conform to IS: 99213 phase 415 volts and single phase 220V ACThe location of disconnect switches in substations affects substation layouts.Maintenance of the disconnect contacts is also a consideration in the layout. In somesubstations, the disconnects are mounted at high positions either vertically orhorizontally. Although such substations occupy smaller areas, the maintenance of