Two-Terminal Algorithm Analysis for Unsymmetrical Fault Location on 110 kV Lines

This work analyses a two-terminal algorithm designed to locate unsymmetrical faults on 110 kV power transmission lines. The algorithm processes synchronized voltage and current data obtained from both ends of the protected transmission line and calculates the distance of the fault. It is based on decomposing the equivalent circuit into the positive-, negative- and zero-sequence components and finding the point where the output voltages of the right and the left side of the transmission line are equal. Compared to the conventional distance relay locator, the accuracy of this method is higher and less influenced by the fault resistance, the parallel-operated line effect and line asymmetry, as discussed in this work. It is, however, very sensitive to the synchronization accuracy. The mathematical model of the power system was created in the PSCAD (Power Systems Computer Aided Design) environment and the computational algorithm was implemented in Mathematica software.