Effects of SSSC on Distance Relay Tripping Characteristic

This paper presents the measured impedance at the relaying point in the presence of one of the series connected flexible alternating current transmission system (FACTS) devices, i.e. static synchronous series compensator (SSSC). The presence of SSSC on a transmission line greatly influences the tripping characteristic of distance relays. Distance relay tripping characteristic itself depends on the power system structural conditions (short circuit levels at the line ends), pre-fault loading (load angle and voltage magnitude ratio of the line ends), and especially the ground fault resistance. In the presence of SSSC, its controlling parameters as well as its connection point also affect the tripping characteristic. Here, the measured impedance at the relaying point is calculated due to the mentioned affecting parameters.