Effect of instrument transformers connection point on distance relay operation in presence of SSSC

This paper presents the measured impedance at the relaying point 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 by distance relays. The measured impedance by distance relay itself depends on the power system structural conditions, pre-fault operational conditions, and especially the ground fault resistance. In the presence of SSSC, its structural and controlling parameters as well as the connection point of the instrument transformers of distance relay affects the measured impedance. Here, the measured impedance at the relaying point is calculated due to concerning parameters for both the line on which the relay is installed as well as the line behind.