Adaptive digital distance relay for SSSC-based double-circuit transmission line using phasor measurement unit

The existence of midpoint series flexible alternating current transmission system (FACTS) devices leads to degrade the performance of mho relay, leading in erroneous estimation of fault location, ie, overreach or underreach for wide variation in network parameters. This research article proposes a novel mho relay algorithm to improve the performance of distance relay in presence of FACTS device using phasor measurement unit (PMU). First, the complete model of transmission system employing static synchronous series compensator (SSSC) and its control strategy is described analytically, where the error introduced in measurement of impedance due to SSSC on the performance of distance relay. Second, a novel mho relay procedure is developed based on PMU to protect the first zone of double-circuit transmission line for single line-to-ground (SLG) fault. The proposed work is analysed and simulated with 48-pulse SSSC carried out with Bergeron model of transmission line using power system computer-aided design (PSCAD) computer simulation. Finally, the simulation results represent that the suggested adaptive scheme is truthful, reliable, and secure with change in compensation level of SSSC.