Use of higher harmonics to detect difficult earth-fault cases in MV networks

This paper gives the analyses of some basic earth fault events in a real electric power distribution network, with a special attention given to the situation when the load side end of the conductor has an earth contact. This kind of a fault is much more serious than common type of the earth fault, which is predominantly analyzed in the literature. Considerable number of measurements of the earth fault currents and neutral point voltages in the various fault situations have been performed. Here are given comparative results for an insulated and a small impedance earthed distribution system. Certain attention is also given to the analyses of higher harmonic components, especially 5th harmonic, in the earth fault current.