Global Earthing System: Can Buried Metallic Structures Significantly Modify the Ground Potential Profile?

Global Earthing Systems (GESs), created by the interconnection of local Earthing Systems (ESs), should guarantee the absence of dangerous touch voltages. According to international Standards, one of the reasons for this safety characteristic of GESs is that MV and LV grounding systems form a quasi-equipotential area. Typical examples of GESs are in city centers, thanks to the high number of interconnected grounding systems in the area. For this reason, in addition to ground-grids, also other metallic parts with different primary functions shall be considered: for example, water and gas pipes, tramway tracks and building foundations can modify the electric potential distribution in the area. In this paper, a model based on the Maxwell’s sub-areas method (MaSM) is used to evaluate how buried metallic parts, not intentionally connected to ground-grids, modify the electric potential on the soil surface. Firstly, the MaSM model is validated with experimental measurements on a simple electrodes configuration. The measured voltages are compared with the MaSMresults and with the results obtained with a FEM model simulated with COMSOL Multiphysics. Then the simulations are carried out on a realistic urban test case.