Detection of Internal Faults in Transformers By Negative Sequence Current

Abstract

Initially it is very difficult to find out internal fault in transformer. These internal fault are hazardous and causes overheating of transformer oil and winding, it consequences as insulation failure because of this uninterrupted power supply cannot be continued. It is more difficult to detect internal fault in small ratting transformer. Buchholz Relay is classical method for detecting these internal faults in transformer but this method is based on generation of gasses during faults.
This work deals with a technique which is based on source formation of negative sequence current inside or outside of transformer for detecting internal fault. The protection against these fault with the help of differential relay connected both side of the transformer winding which compare the phase difference of negative sequence current.