Apparent Soil Resistivity Data Processing Using Optimization Method

The soil forms the basis of grounding studies and the main steps to obtain its model are: the acquisition, processing and interpretation of soil resistivity data. This paper refers to the processing stage, which were obtained through field measurements. In this context, the aim of this work is to present a methodology for the treatment of measured apparent soil resistivity data using the Wenner 4-Electrode Method in the area where a substation grounding grid will be installed. The methodology is characterized by the minimization of an objective function, which is applied to a set of measured apparent soil resistivity values in the various directions where the measurements were carried out. The comparison of the methodology that minimizes an objective function with the procedure that is usually applied on the ground grid design (arithmetic average of the measured resistivity data) indicated that both methodologies provide different models for the soil structure. However, the method usually adopted by designers should be used with caution, especially when there are significant variations in the apparent soil resistivity values. The optimization method aims to find the equivalent resistivity value of the soil which presents the smallest deviation between measured and calculated apparent soil resistivity values.