A Computational Procedure to Estimate the Fundamental Parameters in Grounding Grid Design

The grounding grid design must be made in such a way that the fundamental parameters do not exceed the safety limits. The estimation of the values of the grid resistance, the touch voltage and the step voltage is carried out by means of formulas and algorithms based on the average potential methods. In this framework, the average potential is often obtained taking into account the mutual influence between the grid electrodes and considering that the current distribution along each electrode is uniform. However, the physical phenomena shows that the current derived to earth is distributed in the grounding grid in such a way that the potential is constant in it. A good approximation to the current distribution that makes constant the potential on the grounding grid, can be performed by a linear programming algorithm. In this communication, we present some results obtained by applying this methodology in the estimation of the grid resistance and the surface potential of several grounding grids. With the aim of improve the features of a grounding grid we tackle the problem of modifying its mesh geometry, keeping fixed the total length of the electrodes and the meshes number, and this also shows the versatility of our methodology. Finally we compare grounding grids with different meshes number and we check that optimizing its geometries, we can get touch and step voltages comparables with the ones obtained by considering equally space grounding grids with a greater meshes number, what can provide a substantial save of material.