Adaptive relay setting for flexible AC transmission systems (FACTS)

The paper presents an apparent impedance calculation procedure for distance relaying of transmission line involving FACTS devices, particularly the UP FC (unified power flow controller). The presence of UPFC significantly affe cts the trip boundaries which are also adversely affected by fault resistan ce combined with remote end infeed, Depending on the UPFC location, the tri p boundary is influenced by the fault location, prefault condition, the are fault resistance and the parameters of the UPFC itself (series voltage mag nitude and phase angle). The adaptive nature of this protection scheme nece ssitates the use of a neural network for generation of trip boundaries.