Effect of Extensive Cabling on Efficiency of Resonant Earthing Applied in Medium-Voltage Distribution Networks: a Hungarian Case Study

Earthing practice of medium-voltage networks fundamentally affect operation of distribution networks by determining voltage and current behavior during earth faults, which are the most common type of shunt faults. A widely applied solution is the utilization of arc suppression coils and resistive earthing on overhead line and cable subnetworks, respectively, but transition of network infrastructure often necessitates reviewing best practices. Latter issue is discussed in present paper, using a mixed overhead line-cable subnetwork of a Hungarian distribution system operator as case study. The examined subnetwork is subject to significant extension and topology reorganization, providing motivation for an in-depth analysis. Computer modelling and simulation was used to estimate changes in the magnitude of earth fault currents, detuning factor and ratios of positive and zero sequence impedances. Based on results of the simulation, a proposal has been prepared to maintain compensation capabilities of the subnetwork by installation of additional arc suppression coils.