Effects of CT and VT Connection Point on Distance Protection of Transmission Lines with FACTS Devices

: This paper presents the effects of instrument transformers connection points on the measured impedance by distance relays in the presence of Flexible Alternating Current Transmission System (FACTS) devices with series connected branch. Distance relay tripping characteristic itself depends on the power system structural conditions, pre-fault operational conditions, and especially the ground fault resistance. The structural and controlling parameters of FACTS devices as well as the connection points of instrument transformers affect the ideal tripping characteristic of distance relay. This paper presents a general set of equations to evaluate the measured impedance at the relaying point for a general model of FACTS devices to consider different affecting parameters.