Differential Protection of Transformer using Differential Relay

 Generally Differential protection is provided in the electrical power transformer rated more than 5MVA.

The Differential Protection of Transformer has many advantages over other schemes of protection.

1. The faults occur in the transformer inside the insulating oil can be detected by Buchholz relay. But if any fault occurs in the transformer but not in oil then it can not be detected by Buchholz relay. Any flash over at the bushings are not adequately covered by Buchholz relay. Differential relays can detect such type of faults. Moreover Buchholz relay is provided in transformer for detecting any internal fault in the transformer but Differential Protection scheme detects the same in more faster way.
2. The differential relays normally response to those faults which occur in side the differential protection zone of transformer.