Interferences Phenomena Between Separate Grounding Systems

One of the main purposes of grounding systems is to safely inject fault currents into the soil; such currents flow through any buried conductive objects (e.g., other earth electrodes) eventually present along their path to the source. As a result, even though grounding systems may be metallically isolated, they become coupled due to the flow of the earth-current and interferences occur. Due to this unwanted coupling, dangerous potentials may arise over the “passive” electrode, which may expose persons to the risk of electric shocks. This paper proposes a semianalytical approach to evaluate mutual interactions among grounding systems at low frequency, and establishes criteria to evaluate their actual independence. A significant case study of interactions between the substation grid and the safety ground bed in a mining installation is quantitatively discussed.