Lightning electric field in the soil and its effect to buried cables

This paper presents the distribution of electric field in soil and electric field at underground cable surface due to lightning current to ground. The finite element method is used to analyze the electric field. There are many factors that could have an effect on soil breakdown, including the influence of soil resistivity, cable depth, distance between cable and strike point and lightning peak current. The safety depth of cable and the suitable ground rod position are shown in this paper. In case of the distance between cable and strike point are constant value, the result shows that electric field at cable surface in each position are different. In case of regions with soil resistivity 100 Omegamiddotm and 2 % risk of failure, the distance between ground rod and underground cable should be about 3 meters for depth of cable about 1.2 meters while depth should be 5.5 meters to protected direct lightning strike over cable