Heydar Imani - University of Science and Technology , Iran
Sadegh Jamali - University of Science and Technology , Iran

Fault occurrence in the transmission lines which are compensated by TCSC exerts complicate characteristic on distance relay operation. Different modes of TCSC in fault conditions can be appeared for preventing the TCSC equipments against overvoltage . Different modes made by TCSC control strategy cause relay mal-functioning, because these modes affect the distance relay impedance calculation from relaying point to a fault location considerably. When a single phase to ground fault is occurred in transmission line which is compensated by TCSC and TCSC be located in the line section between relaying and fault points, the pre-fault load flow, operational and structural power system conditions and zero sequence parameters changing make the relay overraching or losing directional integrity less than 3- phase – phase fault case.

Distance relay , Thyristor controlled series capacitor , Impedance measurement , Power system blockset