Grounding resistance of buried electrodes in multi-layer earth predicted by simple voltage measurements along each surface-a theoretical discussion

A power system protection earth is modeled as an inhomogeneous conducting medium with multiple horizontal layers. For known layer conductivities and thickness, the voltage distribution and grounding resistance have been computed efficiently using an equivalent image method. In this paper, the reverse sequence is proposed. Without explicitly knowing the layer conductivities, thickness and number of layers, the equivalent images are determined by the voltage measurement results along the earth surface. Then these images are linearly translated to compute the underground voltage profiles and grounding resistance of buried electrodes. Such surface measurements are simple and inexpensive, and should give very accurate results based on the experience of applying these images in the microwave area