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 seriesconnected flexible alternating current transmission system (facts) device, i.e. staticsynchronous series compensator (sssc). the presence of sssc on a transmission line hasa great influence on the tripping characteristic of distance relays. the distance relay trippingcharacteristic itself depends on power system structural and pre-fault operational conditionsand, 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 thetripping characteristic. here, measured impedance at the relaying point is calculated, due tothe concerned parameters.