A Two Terminal Network-Based Method for Discrimination Between Internal Faults and Inrush Currents

A novel scheme based on two-terminal network to distinguish the inrush current from the internal fault current in the power transformer is proposed. By eliminating the mutual flux linkage in the transformer loop equation, a two-terminal network containing only the winding resistance and the leakage inductance is generated. According to the absolute difference of active power (ADOAP) flowing into and consumed by the two-terminal network, the criterion to identify the internal fault is developed. A total of 162 experimental cases have been tested and the proposed method is able to reliably and accurately discriminate internal faults from inrush currents with easy implementation.