Active Power Based Distance Protection Scheme in the Presence of Series Compensators

Flexible ac transmission system (FACTS) controllers, especially the series-FACTS controllers, affect the operation of distance relays and can lead to the relays under/over-reaching. This paper aims to demonstrate the effects of static synchronous series compensator (SSSC) and series capacitive compensation (SCC), as two important series compensators, on the distance protection using theoretical and computational methods. The results of the investigation are used to develop a feasible and adequate method for eliminating the negative effects of these devices on the distance relays. The developed method measures the voltages at terminals of the SSSC and SCC by phasor measurement units (PMUs) which are then transmitted to the relay location by communication channels. The transmitted signals are used to modify the voltage measured by the relay. Different operation types and conditions of SSSC and SCC, and different faults such as phase-to-phase and phase-to-ground faults are investigated in simulations. Since the modeled distance relay can measure the fault resistance, trip boundaries are used to show the performance of the presented method. Results show that the presented method properly eliminates the negative effects on the distance relays and prevents them from mal-operation under all fault resistance conditions.