i have one transformer 1000kva, 11/.433kv. we are using
200/5 amp. ct unit for measuring purpose, & one 800 amp.
V.C.B Unit for the same t/f operate, i wants to known the primary
current of T/F is only 53 amp. why we used 800 amp.
V.C.B ? & 200/5 amp. CT Unit.

Answer Posted / a k kataria

Well given the rating of transformer as 1000 kva, CT ratio
should have been 100/5. As far as VCB current rating is
concernd,these are generally made for universal
applications and are generally 630 Amps onwards 'cause in
the eventuility of fault ,heavy currents are to be taken
care of.More over increase in the rated current capacity of
breaker adds little to the cost compared to other
components of the breaker.There fore capacity of VCB is OK.

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