Multilayer ground determination from apparent resistivities and impact on grounding resistances

The determination of the ground structure in terms of its electric parameters (resistivity and permittivity) is a key point for calculations of ground electrical conduction, especially when high voltages are involved. A mixed optimization method designed to determinate the resistivities and lengths of the ground layers in a horizontally stratified model for the soil is presented, using the Genetic Algorithms and Pattern Search. The input for this method will be a set of apparent resistivities, measured using the four-probe Wenner method. This paper will justify the need of taking into account a heterogeneous soil.