Characteristics of earth faults in electrical distribution networks with high impedance earthing

Abstract This paper presents an analysis and comparison of earth fault characteristics in the medium voltage distribution networks (20 kV) with high impedance earthing. The results presented are based on the evaluation of 476 real case data recordings, obtained from substations of distribution networks with an unearthed or a compensated neutral during the observation period of 3 years, 1994–1996. The networks were mainly of overhead construction, with a smaller share of underground cables. In the occurrence of disturbances, the traces of phase currents and voltages and neutral currents and voltages were recorded at two feeders at two substations. The study dealt with the clearing of earth faults, relation between short circuits and earth faults, arc extinction, arcing fault characteristics, appearance of transients and magnitudes of fault resistances. The results contribute to various developments of distribution automation and protection systems.