Earthing grid parameters with conductor surrounded by an additional substance

An extensive analysis has been carried out of the influence on touch voltage and earthing grid resistance of placing an additional substance in the trench surrounding the conductor. Earthing grid resistances and touch voltages have been computed by two different methods: a simple approximative analytical method and a much more accurate boundary element method. It has been shown that the approximate analytical method gives sufficiently good results. The influence of the additional substance in the trench on touch voltages is especially significant for large earthing grids, while the influence on earthing grid resistance is smaller.