Using Fault Current Limiter to minimize effect of Thyristor Controlled Series Capacitor on over reach problem of distance protection

FACTS series devices such as thyristor control series capacitor (TCSC) are used to improve the power transfer capability of long transmission lines. These series connected FACTS devices inject a series voltage with the line and change the line impedance and cause the impedance seen by distance relay to be lower or higher than the actual line impedance and the distance relay either over reaches or under reaches. In this paper, a new method is proposed to minimize the impact of TCSC on distance relay. In this method each TCSC is equipped with the Variable Impedance Fault Current Limiter, when fault is occurred, this Fault Current Limiter enters in the system and by injecting series impedance, minimizes the impact of TCSC on distance relay. The simulation results verify the suggested method.