Analysis of earth currents in a medium-voltage distribution network with three-core cables

In this paper a simplified zero-sequence model of a medium-voltage network with three-core cables is proposed. The model is then used to analyze the distribution of earth currents in the network when a phase-to-ground fault occurs in the line between consumer substations. Then this paper studies how this distribution changes when the resistance of earth grids of consumer substations change and when fault location changes. Result shows that a large proportion of earth current flows back to the earth grid of source substation through sheaths and armors of cables instead of flowing to the earth grid of the nearest consumer substation. And this proportion is hardly affected by the resistance of earth grids of consumer substations or by fault location. The theoretical result is testified by simulation using PSCAD.