Identification of faulted section in TCSC transmission line based on dc component measurement

This paper presents an analysis of possibility of detecting a fault position with respect to the compensating bank in a series compensated transmission line. TCSC transmission line is taken into considerations. The compensation rate for such lines is controlled by the fire angle of thyristors included in parallel to the compensating capacitors. Knowledge of the fault position, i.e. whether a fault has occurred in front of the compensating bank or behind it, is important for a distance relay protecting the series compensated line. In case of identifying that the fault is behind the bank, the fault loop impedance has to be calculated with compensating for the voltage drop across the compensating bank. In turn, for faults occurring in front of the compensating bank, there is no need for reflecting the compensating bank, and the fault loop impedance is calculated as in a distance relay designed for uncompensated lines. The presented algorithm for detecting the fault position is based on determining the contents of dc components in the distance relay input currents. The dc contents is evaluated with use of fuzzy logic technique.