Substation Grounding Grid Diagnosis Applying Optimization Techniques Based on Measurements and Field Tests

In measurements on substations grounding grid located in urban areas and considering the overhead ground wires of transmission lines connected to the conductors of the grid, some constraints results in issues in the measurement process. In this scenario, an adequate diagnosis of the safety offered to human beings by the grounding grid under test when a short-circuit involving the earth occurs is not a trivial task. In this context, the paper presents a methodology that allows a trust diagnosis regarding to the safety provided by a grounding grid to the people nearby or inside of a substation. The method has two steps. First, the Fall-of-Potential Method with reduced distances between electrodes is used to determine the equivalent impedance of the grounding system. After that, the ground current is obtained. In both stages, optimization techniques are applied to the specific equations that govern the phenomenon under study. Measurements were performed on real ground grid, as well as, comparisons with state-of-the-art demonstrate that the methodology provides adequate results.