In electrical power distribution systems, a protective ground conductor is an essential part of the safety earthing system. For measurement purposes, the Earth serves as a somewhat constant potential reference against which other potentials can be measured. Knowing how to properly test an electrical ground system is essential to ensure that it has an appropriate current-carrying capability to serve as an adequate zero-voltage reference level. The main purpose of the instrument is to determine the adequacy of the grounding of an electrical system. By a standard of the National Electrical Code the resistance of the soil should be less than 25 Ohms to reliably and efficiently ground the installation. The NFPA and IEEE recommend a ground resistance value of 5 ohms or less. Computers, generating stations, and process control equipment may require as little as 1 or 2 ohms. Before the design of the grounding system begins, soil resistivity measurements need to be taken at the substation. Stations with uniform resistivity throughout the entire area are rarely found.
Geophysical Methods Used For Electric Grid Investigations
Geophysics HM
