Q: Whenever we see graphics for single-point grounding, it’s always a cluster, a connection to the neutral, a connection to a phase and a chain connecting to the other two phases. But when we check with other utilities or consultants, we see all kinds of arrangements, such as bracket grounds with a single point or two sets of single-point grounds bracketing the workspace. Where do we find the definitive arrangement, and why are there so many variations?
A: Under OSHA, the employer is solely responsible for determining how they will meet the requirements of 29 CFR 1910.269(n)(3), “Equipotential zone,” which requires that grounding of de-energized phases be installed in an arrangement that prevents employees from being exposed to differences in electrical potential. In addition to 1910.269(n)(3), there also is Appendix C to 1910.269, “Protection From Hazardous Differences in Electric Potential,” as well as IEEE 1048-2016, “IEEE Guide for Protective Grounding of Power Lines,” a consensus standard that may be considered the authoritative best practice. IEEE 1048 is filled with detailed electrical data – from modeling to application – to explain how to create equipotential protection and effective tripping of grounded circuits that may inadvertently be energized.