Development of adaptive distance relay for STATCOM connected transmission line

Flexible AC Transmission System (FACTS) devices are inserted into power grids in series, in shunt, and in some cases, both in shunt and series for the improved power transmission capability. They also improve the controllability, stability and power quality of the power system. Static Synchronous Compensator (STATCOM) is a shunt type FACTS device connected at the midpoint of the transmission line to maintain the voltage at desired level by injecting/absorbing the reactive power. These devices have fast dynamic response time, which overlap with the response time of the line protection distance relays. This interaction affects the performance of distance protection relay during line faults. In this paper the design and development of a new adaptive distance relaying scheme to mitigate the adverse effects of the STATCOM is presented. A ±100MVA 48 pulse STATCOM with associated control system, connected at the midpoint of a typical 400KV transmission system is selected for simulation. The line faults of different types at various locations of the line are simulated using EMTDC/PSCAD^® and the performance of newly developed adaptive distance protection scheme has been evaluated and efficacy of the proposed scheme is illustrated.