Soil moisture variation around the electrical substation grounding system — draining/damping — is usually caused in two ways: (1) seasonal atmospheric changes (atmospheric precipitation, sun, frost) and (2) high intensity and long duration currents flow from the grounding system, e.g. permanent short circuit current in transmission and distribution networks with isolated neutral point of power transformers, return current flow through the ground in the monopolar electrical systems which use ground as a return line (AC and DC electrotransport systems, DC power transmission, „back-to-back” (AC/DC/AC) substations for two unsynchronized systems connection). Changes in moisture cause the change of physical structure of the soil, which is reflected on geo electrical soil characteristics, especially on the specific electrical resistance p. These study of this phenomena and their impact on the main calculation parameters of grounding system will be carried out using the field interdependence model. The analysis will be performed on a real substation and these results will try to give an answer if these phenomena were justifiably or unjustifiably neglected due to their complexity and lack of effective analytical tools in classical grounding design so far.