Answer / sunit

from my point of view what i have seen physically .. if one phase of the 11kv line is faulty or jumper in transmission lines burnt out then there will be a low voltage in the secondary side of transformer,
actually DTR breaker in control room needs to trip the circuit but if the relay time settings are not accurate then it won't trip the circuit rather show low voltage in the secondary side...

Answer / k.prakashchandra

If delta/star ,one phase voltage will be normal and the
other two 50%, If star/star two phases normal and the third
missing

Answer / b.janardhana rao

I seen physically. One phase of 3 phases failure in HT. I said Example it will shows like RY - 415, YB-415, BR - 230Volts in seconary side. In that time two phases what loads are there is working. Remaining phase is not working. So 3 phase loads like pums, motors are not working. So we can put in ACB phase failure relay to be used. In that case the ACB breaker wads tripped.

Answer / suresh

HT side one phase fails means secondary side unbalance voltages coming ,that means upstream side breaker will trip within time limit.

Answer / technical1210

11kv/415v T/F is designed for 3 phese supply , if 1 phase
fails then t/f will trip automaticly and no voltage will be
avaliavle at secondary side.

Answer / m.prasath

Here,
Primary voltage is 11kv.
Secondary voltage is 400v.
If primary voltage is failed means nothing will happen in secondary side. ie almost zero in secondary side in transformer....

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