Analysis of impedance relaying procedure effected by STATCOM operation

With the increase in the number of static synchronous compensator (STATCOM) type FACTS devices in transmission lines, transient behavior of power transmission systems in presence of fault accuracy are affected, that is due to the impacts of these devices on operation of relays during fault clearing. It is very important that the distance relays do not malfunction under system fault conditions, as this will result in the lack of stability or the security of the system, which defeats the main purpose of installing a STATCOM. These influences are dependent on location of STATCOM, the setting of STATCOM control parameters and the operation mode of STATCOM. In this paper, the measured impedance at the relaying point is calculated and the analytical and simulation results of the application of distance relay for the protection of transmission line incorporating STATCOM are presented. A detailed model of STATCOM and its control is proposed and integrated into the transmission system in order to accurately simulate the fault transient. The results are presented in relation to a typical 400kV transmission system employing STATCOM. The PSCAD/EMTC software is utilized for transient simulation of the selected system.