Numerical Formulation to Evaluate the Coupling by the Soil Among Multiple Grounding Electrodes: A High Voltage Substations Application

This article presents a methodology to calculate grounding potentials in adjacent electrodes present in high-voltage substations subjected to a short-circuit current dissipated in the main grid. The contribution of the technique is the consideration of the coupling by the soil among electrodes taking into account a two-layer soil and irregular geometry of the conductors. This problem is of special concern due to the presence of passers-by near metallic fences, not directly connected to the grounding grid, whose potentials usually have not been evaluated. In this context, the article presents a general analytical formulation aiming to estimate the potential in multiple electrodes, leading to a possible risk to human beings close to the substation. Sensitivity studies are performed in order to evaluate the effect of the soil resistivity and the distance from the faulted grid and the coupled electrode. A practical application in a substation grounding system is discussed. Finally, a huge grounding system is evaluated in order to verify the robustness of the proposed formulation.