On the Performance of Concrete Foundations as Natural Grounding Electrodes in Transmission Line Towers

The purpose of this study is to analyze the behavior of the structural foundation of transmission line towers as a grounding system. Using the Segmentation-Integration method implementation available in industry-standard software, a typical tower structure is analyzed under different scenarios, with a compreheensive assessment of current distributions, GPR, touch and step voltages for different values of concrete electrical resistivity, considering a non-homogeneous soil. The results show that in soils with two layers, if the resistivity of the top layer is lower than of the bottom layer, then the tower foundation grounding performance may become impaired, depending on the characteristics and humidity state of the concrete. However, the association of counterpoise conductors with the foundation shows satisfactory results. If the top soil layer has a higher resistivity than the bottom layer, the foundation itself may be sufficient to ensure effective grounding dispersion.