A two layer ground computational model for the numerical simulations of the earthing systems

A two layer ground model for the computation of the earthing systems is presented. The model combines the pipe element method with multiple image technique by using a fundamental solution defined for the two-layered three-dimensional (3D) half space. The model couples two problems: an external one that models the phenomena that occur in the soil - solved with the boundary element method (BEM), and an internal one that models the potential distribution in the buried metallic structures - solved with the finite element method (FEM). In order to evaluate the two layer ground computational model, the resistance-to-earth is computed for three particular earthing systems (vertical rod, horizontal rod and gradient control mat) and compared with the analytical solution. The earth potential rise (EPR) in case of the gradient control mat is represented.