Answer / s bagchi

Step1: convert the kva or kw load into amps by dividing
with the respective voltage & pf in case of kw.
Step2: refer a cable catalogue & derate the current
considering temperature rating factor & group rating factor.
Step3: select a cable size considering the derated current.

at first you need to calculate the min cable size in case
of ht cables considering short time current & the fault
clearing time of the upstream breaker.

Answer / harshad

First calculate the current.
Eqn for 3phase: Current= Connected load in watt/sqr root of 3*415*pf

Eqn for 1phase: Current=Connected load in watt/230
Select the cable size from the chart with respect to the current.
pf(power factor) is 0.8 or 0.9

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