Soil Water Content and Porosity on Earth Potential Rise of Vertical Grounding Rods

Several formulations have been proposed to compute the electrical parameters of soil regarding its physical properties such as frequency effect, ground stratification, porosity, water content, and temperature. This paper investigates the impact of the porosity and water content on the soil conductivity proposed by the improved Archie's model on the harmonic grounding impedance of a 3-m vertical rod buried in two types of soil (clay loam and sand). The harmonic grounding impedance is computed by the full-wave electromagnetic software FEKO® for a frequency range from 100 Hz up to 10 MHz. Then, the transient ground potential rise (TGPR) is computed for lighting currents of the first and subsequent return strokes. Results indicated a significant influence on the peak values of TGPR wave-forms obtained for saturated soils, including porosity and water content compared with those assessed with dry soils. Increasing the water content and decreasing the porosity level produce more conductive soils that impact the transient responses notably.