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 / krishna chaitanya

first u must know that transformer transforms with
no change in power. As its 11 kv on primary side as
per funda you can calculate primary current 53 amps.
P = vi cos fi. A 100/5 ratio ct is enough to measure.
But its always advisable to select equipments with
larger than required ratings. Sometimes u'l see a
300/5 ratio ct.
and vcb, 800 amp vcb is for load. There'l be another
breaker at secondary of transformer with larger than
this amp rating. 800 vcb is provided for a particular
load control.
checkchaitu@yahoo.com

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