Failed 100 amp fused disconnect

[linemanfrog]

Had a crew last week that was changing out an arrestor and found a bad fused disconnect. The disconnect and arrestor was on a fiberglass "T" bracket and they placed a mechanical jumper from the line to the stem on the URD termination. Once the jumper was in place they opened the disconnect and lifted the top side of the arrestor and disconnect so that the only thing that should have been energized was the bottom side of the disconnect and the termination. The lineman allowed the "de-energized" top side to lay in the bucket and noticed a buzzing and thought it was induction or static. He proceeded to loosen the nut that holds the arrestor to the "T" bracket and it fuzzed like an energized phase would. At that point he backed up and asked for a primary voltage meter. Upon testing the metal end on the fiberglass bracket he found over 3000 volts of potential. At this point the removed the termination from the disconnect and changed out the disconnect. Once a new disconnect was in place the voltage present on the metal end of the "T" bracket was gone.

When the crew returned to the yard they saw the folks that test our aerial lift testing trucks and asked them to test the failed disconnect. The disconnect failed the test both top side to bottom side and from bottom side to mounting bracket. The disconnect had no hairline cracks, excessive build up of dust, mold, or mildew, or any other visible cause for failure. The disconnect was a porcelain AB Chance disconnect.

Just thought I'd share with everyone to reinforce the reason why you need to lift the top side of fused disconnects before considering them a visible open when making your work safe for dead and grounded work. There was no indication of any kind of failure other than the buzzing of the material that should have been deenergized.