Comparing series and shunt reactive power compensation via UPFC from distance relay point of view

This paper presents the measured impedance at the relaying point in the presence of Unified Power Flow Controller (UPFC), one of Flexible Alternating Current Transmission System (FACTS) devices, and compares the effect of series and shunt reactive power compensation via UPFC from distance relay point of view. The presence of UPFC on a transmission line greatly influences the measured impedance at the relaying point. The measured impedance itself depends on the power system structural conditions, pre-fault loading, and especially the ground fault resistance. In the presence of UPFC, its structural and controlling parameters as well as its installation location affects the measured impedance. Here, two cases of series and shunt reactive power are compared due to their impact on the measured impedance at the relaying point.