Simplified Conservative Testing Method of Touch and Step Voltages by Multiple Auxiliary Electrodes at Reduced Distance

Abstract

Grounding systems (GSs) must be tested periodically in order to maintain the touch voltage (TV) and step voltage (SV) below a safe value in all of the zones of the installation. Measurements of the ground resistance and of the TV and SV are typically done by the fall-of-potential (FoP) method, locating the auxiliary current electrode at remote distance to test the effective behavior of the GS. In urban areas, it could be very complicated or impossible to install the auxiliary current electrode as required, not having area around with sufficient accessibility. At this aim, this paper describes a methodology of using multiple current electrodes at short distances, modifying the classic FoP practice, so that the measurements of TV and SV are always conservative. The adequacy of a GS is verified if the values of the TV and SV, tested inside and in the vicinity of the GS, are below the permissible limits, regardless if they are true or conservatively increased. Thus, the measured TV and SV by the suggested method, always conservative, allow verifying the adequacy of GSs, in the cases where it is impossible to locate the remote auxiliary electrode.