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 charge. This helps reduce the ground potential rise. The degree of the resistance 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