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Expressions for the earth resistance of the human feet in safety studies of earthing systems

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Abstract

This paper concerns the human feet resistance estimates in safety studies of earthing systems, taking into account small effective thicknesses of the surface layer and mutual resistance between the feet. Based on simulations using the finite element method, performed to determine the variation of the feet resistance to earth with the following parameters: resistivity of natural soil, surface layer resistivity and thickness, and separation distance between the feet, the available literature was analyzed; then, expressions for the surface layer derating factor based on the one-foot model are suggested that best match the simulation results. Simple correction factors are also proposed for calculating the earth resistance of two feet in parallel and in series that take into account the mutual interference of the feet for different separation distances between the feet. The influence of inaccuracies in feet resistance assessment on estimates of permissible prospective touch and step voltages is discussed in various cases, taking into account that resistance of the human body depends on the applied voltage and current path.

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Acknowledgements

The author thanks Mr. Joel White, Beloit, Wisconsin, USA, for proofreading the first version of this paper.

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  1. Hydro Power Plants “Iron Gate”, JP EPS Belgrade, Trg Kralja Petra 1, 19320, Kladovo, Serbia

    Ivica Života Paunović

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Paunović, I.Ž. Expressions for the earth resistance of the human feet in safety studies of earthing systems. Electr Eng 105, 1377–1396 (2023). https://doi.org/10.1007/s00202-023-01736-3

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