New criterion to determine the nature of single-phase faults

The character of the voltage at the end of the opened phase conductor was studied and an improved voltage criterion was proposed to distinguish between temporary and permanent single-phase faults. The performance of the improved criterion is hardly influenced by load currents of healthy phases, transmission line length, fault distance or fault earth resistance. For EHV/UHV lines with shunt reactors, the improved method is also effective when a calculated capacitive coupling voltage is employed. Simulation tests show that the conclusions are correct.