Distance Relay Over-Reaching due to TCSC Presence on Second Circuit of Double Circuit Line

This paper discusses the distance relay over-reaching in the case of installation of Thyristor Controlled Series Compensator (TCSC) which is categorized as a series connected Flexible Alternating Current Transmission System (FACTS) device, on second circuit of a double circuit transmission line. This is done by presenting the measured impedance at the relaying point in the case of TCSC presence at the far end of the second circuit. Distance relay tripping characteristic is greatly influenced in the presence of TCSC on the transmission line or even in the case of installing TCSC on the far end of the second circuit. Distance relay tripping characteristic depends on many factors including the power system structural conditions and the pre-fault loading, the ground fault resistance, and TCSC compensation degree.