The impact of TCSC on distance protection relay

When a fault occurs in thyristor controlled series compensation (TCSC) transmission lines, TCSC presents a very complicated impedance characteristic and exerts influence on the power system´s distance relays. Under ground faults, the complex changes of sequence currents exert influences on the mho characteristic, reactance characteristic and directional characteristic and makes the protection region unstable. Longitude distance protection with an overreaching setting value may be a solution to TCSC line´s protection, but it has difficulty in setting the relay on the reverse directional line to avoid misoperation. Simulation shows that sampling frequency has an influence on distance protection performance in TCSC transmission lines