Answer Posted / madhu mohan

First calculate the current of primary side(HT) and derate the cable by atleast 0.7.
Eg:1500*1000/(1.732*11000)=78.73A
Current I after Derating =78.73/.7 =112A (0.7 if laid on the trays or value will vary if buried in the ground).
Cable equivalent to rating has to be selected.
Now Short circuit withstand capacity (sq. of I X t in sec) has to be checked from the cable catalogue.This value of cable should be higher then SC withstand capacity of the ground usually it is 50KA.it less go for next size and finalise.

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