A faulted side identification scheme-based integrated distance protection for series-compensated transmission lines

This paper introduces an integrated distance protection technique for series-compensated transmission lines (SCTLs) based on a new scheme to identify the faulty side with respect to the compensator. Conventional distance algorithms suffer from mal-operation under faults behind the Series Compensator (SC). Therefore, the modified mathematical algorithm of the distance relay treats with these faults via compensating the voltage drop through the SC to integrate the relay performance along the line. Consequently, the faulty side either upstream or downstream the SC must be identified. This identification is accomplished via a new function inserted in the mathematical algorithm. The presented function is a voting system based on both of the angles of the obtained conventional and modified apparent impedances. The presented voting scheme is based on basics theories of the fault analysis and the phasors diagrams of the equivalent apparent impedances seen by the conventional and modified algorithms whether the fault is upstream or downstream the SC. The presented scheme is suitable for all fault types even with high fault resistances. MATLAB package is used to simulate 400 kV compensated transmission lines and also to implement the presented algorithm. Diverse fault cases are investigated to test the response of the presented voting system under different fault conditions including the fault type, location, and impedance. The results confirm the efficacy of the presented scheme.