Using Series Facts Device for Protection of Transmission Line on Distance Protection Relay and its Mitigation

The basic operation principle of distance relay is based on the fact that the line impedance is fairly constant with respect to the line length. However, the implementation of FACTS controllers in power system transmission for enhancing the power system controllability and stability have introduced new power system issues in the field of power system protection that must be considered and analyzed. Some of the concerns include the rapid changes in line impedance and the transients introduced by the fault occurrence and the associated control action of the FACTS Controllers. The presence of the FACTS devices in the faulted loop introduces changes to the line parameters seen by the distance relay. The effect of FACTS device would affect both the steady state and transient characteristics of the apparent impedance seen by distance relays due to the fast response time of FACTS Controllers with respect to that of the protective devices.