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Earth Ground Does Not Always Clear Utility Fault

Mike

I have been a registered PE for more than 24 years now, and spent most of my time in the Electric Utility industry. I can tell you (Although I realize this is reinforcement, not new to you) that earth ground at even the lower utility distribution medium voltages (5kV to 15kV) does not always provide good fault clearing current. We had a terrible time clearing faults in our delta systems. Some of our distribution systems were actually grounded wyes but without the grounded conductor included in the wiring system. Our 4kV distribution was notorious for lying on saturated ground and burning (literally) without tripping any fault protection on the line.

One of our better linemen was killed because of this. A 4kV line was on the ground at both ends. Current traveled to a guy wire through the ground from the source side and electrified the guy at 4kV. As the wires were all on the ground and not burning or sparking, he assumed it was dead, leaned over and picked up the guy wire. It was the last thing he did in this life.

Maybe something the NFPA, PE Society, NEMA, etc., etc. need to do is review the Code with respect to inconsistencies using the words "ground", "grounding" and "bond." If anywhere, the NEC should use these words rigorously correctly at the level of an Ivy League English Scholar writing for the King Of England.

Frank Elliott, P.E.
FElliot1@ci.tucson.az.us
City of Tucson, Arizona

PS: Keep up the good work!


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