Validation of an integrated methodology for design of grounding systems through field measurements

Abstract

EDP Labelec is responsible for the safety analysis of the grounding system of every new substation in the Portuguese distribution grid, and over the past 14 years, it has developed and perfected an integrated methodology for designing grounding systems, which was described in a previous publication. The company has also more than 30 years of experience in earthing field measurements and is responsible for performing almost all earthing measurements in substations from Portugal's electrical grid. The key goal of this study is to validate the integrated methodology used by EDP Labelec, while identifying the main strengths and weaknesses of each soil resistivity measurement method (2D/3D geoelectrical surveys versus traditional 1D Wenner/Schlumberger), and their impact on the measured results versus simulated results, for different soil types and substation layouts. To accomplish this, the results and statistical data for 6 selected substations are described, which had their grounding grid recently designed and measured by EDP Labelec, before and after their construction, respectively. In sum, the results obtained are very encouraging, and the integrated methodology is considered validated, with results that largely exceeded expectations. Despite this, some significant questions emerged during the analysis of the results. These issues will be addressed in future work.