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The soil characterization is one of the major prerequisites in grounding system studies. Along with an adequate measurement procedure and a reliable field data processing, they are responsible for the success in the design and the installation of grounding grids in electrical power systems. In this frame of reference, the purpose of this work is to present an embracing investigation combining in-situ measuring data from soil resistivity and geological survey, supported by the Wenner method and standard penetration test (SPT). The study is focused on investigating the differences in the apparent soil resistivity interpretation, provided by distinct approaches, identifying the one that better correlates with SPT. Furthermore, a geoelectrical and geotechnical soil characterization is in-depth evaluated, culminating in the derivations among soil resistivity, moisture content, and its mechanical properties. The study has a particular application, but not restricted, to electrical substations design, in which a proper soil modeling and representation are mandatory. The obtained results are promising serving as a foundation for further investigation. [ABSTRACT FROM AUTHOR]

Considering urban substations ground grid diagnosis, some real-physical constraints result in measurement process challenges: 1) limited length between electrodes used to measure the equivalent impedance of the grounding system; 2) to determine the current that flows from ground grid conductors to the earth; and 3) to determine the grid resistance. In this scenario, an adequate diagnosis of the safety offered by the ground grid under test when a ground fault occurs is not a trivial task. This article describes a methodology that allows a reliable diagnosis regarding the safety provided by a substation ground grid. The methodology is applied to the parameters obtained in performed field tests. 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. Then, the ground current is obtained. In both stages, optimization techniques are applied to the specific equations that govern the phenomenon under investigation. Comparative case studies considering real-life data illustrate the effectiveness of the method. [ABSTRACT FROM AUTHOR]