Static synchronous series compensator (SSSC) is a new series compensation device. Its powerful control function brings great benefits to the operation of power system, and it also brings new problems to power system relay protection, especially the performance of distance protection. It is greatly degraded due to the presence of the SSSC. Based on practical SSSC project, the influence of SSSC on distance protection was analyzed, and a new distance protection scheme is proposed. The proposed scheme consists of the new first zone distance protection, the traditional second zone and third zone distance protection. The new first zone distance protection is based on the single-ended ranging quadratic equation method. With the voltage and current signals, it could obtain the distance from fault point to protection installation, and effectively distinguish between the internal fault and external fault according its calculation result and degree of fluctuation. Finally, time domain simulation verifies the feasibility of the scheme.

SSSC, distance protection, fault distance percentage, fluctuation, time domain simulation