Implementation of DSP based relaying with particular reference to effect of STATCOM on transmission line protection

The presence of flexible AC transmission system (FACTS) devices in the loop significantly affects the apparent resistance and reactance seen by a distance relay, as FACTS devices respond to changes in the power system configuration. The objective of this paper is to investigate the effect of mid-point compensation of STATic synchronous COMpensator (STATCOM) on the performance of impedance distance relay under normal load and fault conditions and to implement the adaptive distance-relaying scheme for transmission line protection. From the simulation studies carried out in PSCAD software and using analytical calculations, it is identified that there is a need for the distance relay to adapt to the new settings in its characteristic for the detection of fault within the zone of protection of transmission line. Apparent impedance is simulated for different loading and line to ground (L-G) fault conditions at different locations on the power system network. The proposed adaptive distance relay scheme has been implemented on TMS320C50 Digital signal processor (DSP) system.