Effects of Instrument Transformers Connection Point on Measured Impedance by Distance Relay in Presence of SSSC

This paper presents the measured impedance at the relaying point in the presence of a series connected Flexible Alternating Current Transmission System (FACTS) device, i.e. Static Synchronous Series Compensator (SSSC). The presence of SSSC on a transmission line has a great influence on the tripping characteristic of distance relays. The distance relay tripping characteristic itself depends on power system structural and pre-fault operational conditions and, especially, the ground fault resistance. In the presence of SSSC, its controlling parameters, as well as the connection point of the instrument transformers of distance relay affect the tripping characteristic. Here, measured impedance at the relaying point is calculated, due to the concerned parameters.