Adaptive zero sequence compensation algorithm for double-circuit transmission line protection

This study presents an adaptive zero sequence compensation algorithm to improve the conventional ground distance relays performance, in double-circuit transmission lines. The proposed approach corrects the estimated impedance by correcting the degree of zero sequence compensation of ground distance relays. The new scheme is proposed for the standalone distance relays and does not inherently require any communication link. However, it is applicable to all well-known pilot protection schemes. The proposed method utilises zero sequence equivalent circuit in order to estimate the compensation term. Afterwards, the estimated impedance is corrected by using a recursive approach. Finally, the proposed method compensates the fault resistance effect. The simulation and experimental results verify the efficiency, security and dependability of the proposed method. The results indicate that by using the proposed method, the maloperation of the conventional distance relay because of the mutual coupling is mostly resolved.