Global earthing systems: Characterization of buried metallic parts

Abstract

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 setup , the results and their analysis are reported.

A Comparative Review of the Methodologies to Identify a Global Earthing System

“…Similarly, for the evaluation of the second effect produced by a GES, field measurements were carried out to characterize the different types of extraneous conductive parts (such as, for example, water and gas pipes) that can be buried in urban areas [16], [17], [18]; the effects of these parts on the ground potential profile were analyzed by an analytical model, based on the Maxwell's subareas method [19]. According to the simulation results, a significant smoothing of the ground potential profile occurs only if buried conductors are widespread and connected to the MV grounding network.…”

On the hazardous situations due to the presence of HV/MV substations in urban areas

“…Also the presence of water or gas pipelines, external continuous metal fences or railways must be considered in the design of the earth electrode of the station [1]. In fact, the above-mentioned metal elements can be responsible of the transfer of the earth potential rise (or part of it) to great distances from the fault, in places where an adequate protection against dangerous touch and step voltage can not be easily put into effect [2].…”

The identification of global earthing systems: A review and comparison of methodologies

“…Similarly, for the evaluation of the second effect of a GES, field measurements to characterize the most of the metallic parts that can be buried in urban areas were carried out [12]; their effects on the ground potential profile were analyzed by an analytical model, based on the Maxwell's subareas method [13], [14].…”