THE SOIL IONIZATION GRADIENT ASSOCIATED WITH DISCHARGE OF HIGH CURRENTS INTO CONCENTRATED ELECTRODES

It has been known for many years that the grounding resistance of a concentrated electrode drops when it is subjected to a high current discharge. This helps reduce the ground potential rise. The degree of the resistance reduction depends on the magnitude of the ionization gradient of the soil E(o). Based on both a theoretical analysis and a critical review of the large number of available measurements, this paper recommends that E(o) be taken equal to 300 kV/m for typical soils. This is significantly less than the 1000 kV/m value used by some authors. Graphs are also given describing the behaviour of the rod electrodes which are used in many field installations.