Incident Prevention Magazine

Dwight Miller

Equipotential Grounding: Lessons Learned in the Field

Equipotential Grounding: Lessons Learned in the Field

When the earliest linemen first began to ground lines for worker protection, they attached a small chain – known as a ground chain – to the conductors, with the end dropped to the ground. When I began to work on a line crew, I’m sad to say that my grounding practices weren’t much better than those used in the early days. I wish someone had better explained to me then the situations that could arise, the ways grounding could protect me and the best methods to accomplish it. So, in an effort to help out other lineworkers in the electric utility industry, I want to share in the following pages some of the important aspects of grounding that I’ve learned throughout my career.

Worker Protection
Ever since enforcement of 29 CFR 1910.269 began in 1994, OSHA has required grounding practices that will protect employees in the event that the line or equipment on which they are working becomes re-energized. The equipotential zone, or EPZ, is made to do just that.

If you read paragraph 1910.269(n)(3), the preamble discussion and Appendix C to 1910.269, titled “Protection From Hazardous Differences in Electric Potential,” OSHA’s intent seems clear. To summarize, install temporary grounds and bonds at the worksite in such a manner that keeps the worksite at the same potential and prevents harm to workers even if the line is accidentally re-energized or exposed to induced voltages. You can follow Appendix C as a one-size-fits-all approach or perform your own engineering analysis to create procedures. But keep in mind that if you create your own procedures, you must be able to demonstrate they will protect your workers.

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