Touch voltages and earth fault currents in a rural large-scale underground cable network with connected earthing systems

Abstract

Several long power outages caused by storms led to changes in the Finnish Electricity Market Act in 2013 bringing stricter obligations considering the power outages caused by heavy wind, storm or snow load. New requirements have substantially increased the use of underground cables in medium voltage networks in rural areas where the network has traditionally been overhead lines. Underground cabling changes the structure of the rural earthing network and long cable feeders also bring new electrical phenomena to the network. Caruna, the biggest distribution system operator in Finland, organized two field tests in two different locations to study touch voltages and earth fault currents in its large-scale underground networks. The findings of those field measurements are presented in this paper.