A new fuzzy fault locator for series compensated transmission lines

Series capacitors (SCs) are installed on long transmission lines to reduce the inductive reactance of the lines. SCs and their associated over-voltage protection devices (typically metal oxide varistors, and/or air gaps) create several problems for distance protection relays and fault locators including voltage and/or current inversion, sub-harmonic oscillations, transients caused by the air-gap flashover and sudden changes in the operating reach. In this paper, using fuzzy logic a simple and accurate fault location algorithm is presented for series compensated transmission lines. The fault region is determined by a fuzzy identifier, firstly. Then the distance to fault is calculated from the fault loop quantities similar to the classic fault locators, but in case of voltages additionally the compensation for the voltage drop across the bank (or banks) of series capacitors is performed. The power system is simulated on a PC using PSCAD software to provide fault data. The fuzzy fault region identifier and fault locator are designed and implemented using MATLAB software. The operating behaviour of the fault locator was assessed using a 400 kV, 400km double end fed simulated transmission line with three phase faults at various locations on the line. It relies totally on locally derived information.