Soil resistivity: A limiting determinant to zero-sequence currents for grounded conductors in south african low voltage networks

In this paper, the dependence of soil resistivity on the geological structure and meteorological conditions are discussed. The South African context of changing resistivity and its inevitable consequences on the behaviour of prospective zerosequence currents in low-voltage distribution systems is highlighted. Therefore, field measurements of soil resistivity using the Wenner Array technique is conducted on expansive clay-based soil. The resulting zero-sequence current inherent to the soil conditions is also assessed. The results obtained indicated that the soil resistivity value of 488.74 Ω. m, which corresponds to the soil conditions at the time and measurement season, represents an increase of 62.91% of the standard limit value for expansive clays, and causes 37.14% decrease in the zerosequence current likely to flow at the limit value of expansive clay’s resistivity.