Electrical Adda

1.    Full load current of any motor based on HP,                                     Full load current = 1.5 x H.P                                      For 5 hp motor full load current = 1.5 x 5                                                                = 7.5 A 2.    Capacitor Bank for any Industry = 1/3 x Total H.P of             Company       Ex- For 15000hp capacity industry capacitor bank = 1/3 x 15000                                          Q = 5000 KVAR 3.    Number of Suspension insulators for various voltages.            No of insulators= (Nominal phase    Voltage) / 11                      Ex- For 66 KV Transmission line                   No of insulators = (66/1.732 )/11                                             = 4 +1 (safety)                                             = 5                                                

ACB tripping settings   Acb has 6 adjustable tripping settings 1 Long time delay (Tr ) 2 Short time delay( Tsd ) 3 Earth fault delay (Tg) 4 Long time (Ir) 5 Short time (Isd) 6 Earth Fault (Ig) Long time is for maximum overload capacity . Short time is for short circuit current Earth fault is for earth fault current . As per thumb Rule : 1. Long time set at 0.8 means 80% of full load current .Until this level of current  breaker carry without tripping  . Above 0.8 Acb trips. Long time delay causes the breaker to wait for certain time to allow heavy temporary inrush currents to pass away. Generally long time delay is set at  4 Sec. 2. Short time set at 0.6 means  60% of full load current . It determines the Amount of Current the Breaker will carry for short time period.  Generally short time delay set at 0.2 sec. 3. Earth Fault set at 0.3 or 30% of  fault current . It controls the amount of Ground Fault current that will cause the breaker to interrupt the cir

SUBSTATION GROUND CLEARANCES Nominal System Voltage     Clearance in meters  (Minimum) 11KV        2.75m 33KV        3.7 m 66KV        4.0 m 132KV        4.6m 220KV        5.5m 440KV        8.1m Minimum Clearances (meters) 33KV 132kv 220kv 400kv 765kv Phase –Phase  (meters) 0.320  1.3   2.1  4.2   9.4 Phase-Earth    (meters) 0.320  1.3  2.1  3.5   6.4 Sectional clearance  (meters)  3.0  3.8  5.0  6.5   10.3