Selection of Energizing Quantities for Sensitive Ground Fault Protection of MV Electric Power Networks

摘要

Effective detection and clearing of ground faults in MV networks particularly under high fault resistance is difficult to achieve due to too low values of both voltage and current being used as threshold for fault indication. It must be noted that MV networks employed in mining industry operate with different neutral point arrangement i.e. isolated, compensated and ineffectively grounded via selected resistor as well. Many scientific works were performed if about as detection, modeling and measurement as well as methodology of restoring power supply such failures [1]. Therefore after many years of experience authors have found that one of the possibility to overcome this problem can be application of argument difference detection as a criteria. Thus the argument difference between 1st and 2nd harmonic of both zero sequence voltage (U_0) and current (IOL) for healthy and faulty lines were found to be convenient. However, it requires application of a suitable both voltage and current measuring units. Paper presents and discusses simulation results of possible variations of selected quantities for different network and fault conditions. The influence of leakage (ground fault) resistance and line loading were taken under consideration. On the basis of the investigated results conclusions on reliable operation of the new developed ground fault protection are formulated.