Effect of SSSC on measured impedance of distance relay in double-circuit lines

Distance relays operation is based on impedance measurement at the relaying point, and can be affected by several factors, such as power system structural and operational conditions. With the growing loads, and limits for rights of paths for new transmission lines, resulting in interdiction of more and more double-circuit transmission lines and Flexible AC Transmission System (FACTS) devices into the power systems, which impose further changes on the measured impedance. This paper presents the effects of static synchronous series compensator (SSSC), as a series connected FACTS device, on the measured impedance at the relaying point. In addition to SSSC structural and controlling parameters, its installation point is also affects the measured impedance.