Mutual interference of neighboring grounding systems and approximate formulation

Abstract The paper develops mathematical models for the analysis of the mutual interference of closely positioned ground electrodes in order to assess the safety risks that might appear in various circumstances often characteristic for urban areas. The potentially hazardous situation that might arise in open pit mines at the equipment grounded by connection with the common ground electrode is also investigated. In the scope of the analysis of possible dangerous circumstances the maximum touch – and step – voltages that appear at the sites protected by the grounding grids are calculated for various distances between the grids and in case of uniform and nonuniform two – layer soil. Approximate expressions for assessing some interference effects are also provided and successfully checked for various cases. Based upon the results of the conducted series of calculations, the safety risks are determined for all investigated cases. It was shown that the highest safety risks can appear in the case when the neighboring grids are unintentionally connected as well as in the case when the neighboring grid is connected with some grounded objects, which is characteristic for urban areas and for open pit mines with common ground electrodes.