The Meterglob Project: Impact of Fault Current Division and of extraneous Conductive Parts on Global Earthing Systems

The paper presents the Meterglob Project, focused on practical tools to assess Global Earthing Systems in an urbanized area with a dense MV/LV distribution network. Present norms do not include any suggestion on how to assess reliably the presence of a GES and if and how take into account the influence of extraneous buried conductive parts. Two models have been developed. The first model is used to compute the partition of a single phase to ground fault current between the earthing grids of the MV/LV substations and the MV cable shields of the lines connecting the substations. The second model considers the influence of buried metallic structures on the earth potential rise and on the earth potential profile. The two models have been experimentally verified with an extensive campaign of measurements, still under way, with the objective of synthetizing the results in practical and easy to assess indicators