We have one 500KVA transformer. We have tested REF relay and commissioned. Aft

We have one 500KVA transformer. We have tested REF relay
and commissioned. After one and half year, due to some
ground fault in one of the DB circuit Transformer tripped
by REF relay. What will be cause and remedy. Please advise?

Question Posted / keshavpillai

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We have one 500KVA transformer. We have tested REF relay and commissioned. After one and half year..

Answer / k.prakashchandra

I think DB is the marshalling box.If there is earth fault
or short circuit in CT secondaries of REFR core ,as the
balancing of currents is lost, there will be tripping.You
are advised to test the Tr for internal earth fault before
re-charging.The coneections of CT leads in the MB TB may be
firmly done with brass/copper bolts and nuts to avoid loose
connections.

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