Analysis and simulation to spurious operation of sensitive directional earth fault under load switching condition

This paper presents the theoretical analysis of intermittent mal-operation of sensitive directional earth fault relays when switching off/on load and simulation tests based on Real Time Digital Simulator (RTDS). The magnitude of the residual current and voltage is dependent upon the load level and power factor, system source and line impedance´s, system capacitance to ground and the location of the open circuit. This paper analyses the effect of all electrical quantity to the problem. Based on the test results, the conclusion of mal-operation is drawn.