FORMULA FOR RESISTANCE OF SUBSTATION GROUNDING GRID IN 2-LAYER SOIL

A simple and accurate formula for calculating the resistance of a grou nding grid buried in two-layer soil, is proposed in this paper. The fo rmula is derived from the image theory and a novel synthetic asymptote technique. The resulted; formula is dependent on both the substation grounding grid design parameters (such as grid size, number of meshes, grid-conductor diameter, grid depth, etc.) and the soil parameters (s uch as the resistivities of the upper and lower soils). The resistance s calculated using the proposed formula are compared to the resistance s obtained from a detailed numerical method and the agreement between the results is very good.