Analysis of Polygonal Distance Protection Relay of Transmission Line Affected by SMES Device

Because of unique advantages in rapid response and independent control of act ve and reactive power, Superconducting Magnetic Energy Storage (SMES) device will be widely used in the power system. The SMES exchanges power with power grid in the charging and discharging process, so it may affect the performance of protection relay of transmission line, which will lead to mal-operation. Based on SMES model, the tripping characteristic of polygonal distance relay for single-machine-infinite-bus performance of polygonal distance relay with SMES. The simulation results show the measured impedance of polygonal distance relay is changed by SMES, and polygonal distance relay will make mal-operation when faults occur in the boundary of protection zone. Also an improving distance relay is proposed to solve the problem.