Step potential calculations closely resemble another service offered by Earthing Services, being touch potential calculations. More can be learned by referring to the dedicated service page for touch potential calculations, however this page shall offer some comparison between the two.
Touch potential is the prospective exposure to electrical current in the event that someone is touching a piece of infrastructure at the moment it is subjected to fault electricity. Step potential is a similar concern but considers the likely volume of electricity that may be inducted through the feet and legs of a person standing within the vicinity of a piece of infrastructure during fault conditions. This may not immediately make sense but it is worth considering the behaviours of electricity; it will always seek the path of least electrical resistance, meaning that it is easier to discharge, and it will dissipate over time within the strata of the earth proportionally to the resistance to electricity in the mass of earth.
In the event that the ground mass is offering a poorer conductive environment for electricity to pass than other elements, such as metal pipes, structural steels, or indeed human beings stood on the surface of the ground then electricity will induct to the preferable element, being the path of least electrical resistance (the least opposition to electrical current flow).