An adaptive distance relaying algorithm immune to reactance effect for double-circuit transmission line systems

An accurate digital distance relaying algorithm which is immune to the combined reactance effect of the fault resistance and the load current is proposed. The algorithm can estimate adaptively the impedance to a fault point independent of the fault resistance. To compensate the magnitude and phase of the apparent impedance, this algorithm uses the angle of an impedance deviation vector. The impedance correction algorithm for ground faults uses a current distribution factor to compensate mutual coupling effect instead of using the collected zero-sequence current of the adjacent parallel circuit. A series of tests using EMTP output data in a 154(kV) double-circuit transmission line have proved the accuracy and effectiveness of the proposed algorithm.