Modified distance protection in presence of SSSC on a transmission line

This paper presents a modified distance protection in the presence of Static Synchronous Series Compensator (SSSC), one of the series connected Flexible Alternating Current Transmission System (FACTS) devices. The presence of SSSC on a transmission line has a great influence on the measured impedance at the relaying point. The measured impedance itself depends on the power system structural conditions, pre-fault loading, and especially the fault resistance. In the presence of SSSC, its injected voltage as well as its installation point affects the measured impedance. Therefore, the conventional distance techniques do not fulfill the protective duties satisfactorily and new approaches are required.