Performance analysis of phase distance relay on series compensated UHV lines

For a long UHV line with large distributed capacitance, the lumped parameter model of SC line is no longer valid. The apparent impedances of distance relay on series compensated line are derived and analyzed in details based on the distributed parameter model. Results show that the apparent impedances are influenced by the location of series capacitors. The sensitivity of relays is reduced largely by the settings based on lumped parameter model, while the overreach of relay occurs by the settings based on distributed parameter model but without considering the location of series-compensated capacitors. A modified setting method considering the distributed parameter model and location of series capacitor is presented, and simulation shows that the modified setting method can improve the reliability and sensitivity of distance relay.