Global earthing systems: Characterization of buried metallic parts

International Standards IEC 61936-1 and EN 50522 define a Global Earthing System (GES) as the earthing network, created by the interconnection of local earthing systems, that should guarantee the absence of dangerous touch voltages. This is achieved through two effects: the division of the earth fault current between many earthing systems and the creation of a quasi equipotential surface. The second effect can be enhanced by the presence of buried metallic parts, such as light poles and water/gas pipelines, that can modify the earth surface potential profile. In order to characterize these buried conductors, an extensive measurement campaign was organized; in order to determine the resistance to earth of these buried conductors a simplified measurement protocol has been applied to more than 800 metallic objects. In this paper, the measurement set-up, the results and their analysis are reported.