Ground Resistance of Buried Metallic Parts in Urban Areas: an Extensive Measurement Campaign

In urban and industrial areas, a relevant presence of buried metallic objects (e.g., gas and water pipes, etc.) can be detected. Usually, these elements are imagined as widespread meshed metallic grids in a good contact with the soil. In the last years, an arising interest on their role in the identification of a global earthing system has been expressed by the scientific community. Unfortunately, the geometrical and electrical properties of this kind of buried metallic parts cannot be provided by any documentations. This is mostly due to the fact that no trustworthy schemes are provided, as the management of these metallic parts is responsibility of different companies, which have installed them during several years. In order to characterize the buried metallic elements with reference to the electrical safety issue, the main quantity of interest is their resistance to earth. With this aim, a field measurement campaign was organized and the resistance to earth of more than 800 metallic objects has been evaluated through a simplified measurement protocol. In this paper, the measurement protocol, the setup, the results, and their analysis are reported.