EFFICIENT GROUND GRID DESIGNS IN LAYERED SOILS

A detailed analysis of the effects of ground grid configuration on gro unding performance has been carried out for uniform and horizontally s tratified soils with multiple layers. The results of the analysis reve al that the most efficient and cost-effective design is highly depende nt on soil structure type and characteristics. In the absence of groun d rods, grounding grids with uniform mesh size are quite efficient in soils having a thin (relative to grid size) high resistivity (relative to the lower layers) top soil, while grids with small mesh size at th e periphery of the grid provide optimum performance in uniform soils a nd soils with low resistivity top soils. Ground rods were found to be effective only when a significant portion of their length is in contac t with a low resistivity soil, as expected.