Fault Clearance and Transient Impedance

In order to better understand the operation of a grounding electrode, it is useful to examine the flow of current under a fault situation. During fault clearance, current will flow from the electrode into the surrounding earth. Equipotential surfaces can be plotted at right angles to the current path and will assume a shape determined by that path. Step voltage, the potential experienced across a step by anyone walking on the surface, is determined by the density of equipotential surfaces having equal voltage differences between them in a given direction. The gradient will be highest near the grounding electrode and dissipate with distance.