The busbar size will be determined by the total loads
connected to the bus.This will require a comprehensive
study of nature of loads plus the surroundings of place.
The general procedure will be such that the operating
parameters don't voilate the maximum safety limits of the
Depending on the maximum load current the busbar size will
be determined. Usually for copper it is taken as 2 to 4 Amps
per square mm and for alluminium it is taken as 1 to 2 Amps
The normal availability and design of the busbars is
in our 6.6kv motor feeder[it is having two sources from
Bus A&B] earth fault relay is acting, we checked CBCT
connection and cable meggerd values found very good still
earth fault acting during first two are three start after
that it will hold. please clarify what was the reason. if
same motor is starting from other Bus-A it will start.