Sum-difference impedance relay of transmission line is proposed in this paper. For internal faults of line, sumdifference impedance is equal to line capacitive reactance and for external faults, sum-difference impedance is equivalent impedance of fault resistance and system impedance. The sum-difference impedances are different for internal faults and external faults. The operation zone of sum-difference impedance relay is set in impedance plane. The performance sum-difference impedance relay of PT beak is analysed. The performance of sum-difference is verified by RTDS simulation data. Simulation results show that sum-difference impedance relay is sensitive and not affected by line capacitance current and shunt reactor.
L. Huangzhang, W. Xingguo, Z. Zexin, In Proc. 13th International Conference on Development in Power System Protection 2016 (DPSP), Edinburgh, UK
KEYWORDS: Transmission line, sum-difference impedance relay, capacitance current, internal fault, external fault