How does current flow in the ground?

One of the most exotic concepts in the field of earthing is the ability of the earth to conduct electricity. Its sheer size means that the impedances produced by the passage of current through the soil are very low. Large earthing systems in low soil resistivity areas can produce very small earthing system impedances. What is not as well appreciated is that an overhead conductor using an earth return path to complete a circuit, such as is the case during a phase to earth fault, incurs an additional impedance due to the passage of current through the earth. This paper explores the analogous condition of current flow in a homogeneous conductor and the distribution of current within that conductor due to the impact of skin effect. The earth fault current distribution is constrained by the magnetic forces produced by the current in the earth and the excitation current, being the insulated earth fault current carrying conductor, located either above the ground or within the earth. The earth fault currents distribute in a manner unexpected by many, but with direct impact on transmission line easements and the manner in which transmission impedances are calculated.