Transformer trips ,After recommissioning of Differential relay in YNd1 Transformer Protection panel. What are the probable reason ?

The probable reasons are:

1) Real Fault in transformer

2) Wrong connections of CTs

3) Wrong configuration of the relay

You need to carry out following:

1) Test the transformer for its healthiness

2) Carry out stability test for diffenrential protection circuit to investigate the discrepancy, which is leading to trip.

INRUSH CURRENT AND DIFFERENTIAL PROTECTION CT SATURATION AT HV SIDE

3 Main causes

1. Inrush currents

2. Overexcitation conditions

3.current transformer saturation

check for the derived earth fault setting & measured earth faoult with there time setting.

wrong configuration of the Relay

Real fault in transformer

Wrong connection of CTs.

Wrong configuration of the relay.