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.

[reppy007]

Good info frog,Im pleased and happy that there was no accident,and that it was noticed....wonder if a younger guy in a hurry would have noticed....once again good info.

[bluestreak]

It's been talked about here before A B Chance cutouts are junk anyplace with a freeze /thaw cycle like the northeast where I'm from has had a serious problem with failures over the last 15 or 20 years. The big problem appears that in the manufacturing process they scrimped on the amount of cement they used when installing the fittings in the porcelain which allowed moisture to get into the porcelain and with the freeze/thaw it would lead to cracks with a lot of near disastrous results when operating them. N U spent millions replacing the ones on their system after years of complaints from the Union.

[loodvig]

Most places have made a big effort to REMOVE all AB Chance porcelain 'potted' cutouts from their systems years ago. AB Chance changed their name to Hubbel BTW!

[reppy007]

just a thought....how many guys have worked on a transformer/ect...and only have opened the barrel/door and not lifted the high-side,some always lift it and some dont huh?

[Lineman North Florida]

just a thought....how many guys have worked on a transformer/ect...and only have opened the barrel/door and not lifted the high-side,some always lift it and some dont huh?

Plenty, some would consider it a visual open, but it pays to cover all your bases nowadays.

[BigClive]

At high voltage it doesn't take much moisture or internal tracking to allow a significant current to flow. I'm not necessarily talking amps, but even a few tens of milliamps can impart a fatal shock. The High potential testers tend to be quite sensitive to low currents, so although there may have been significant "fizz" on the cutout it wan't necessarily a dangerous level of current.

Chance cutouts featured heavily on this forum a while back due to a serious number of accidents that involved physical failure of cutouts resulting in wires dropping on workers.
The general opinion at that time was to treat old cutouts as being a liability and to treat them as if they were going to break.

[Bipeflier]

. AB Chance changed their name to Hubbel BTW!

Slight correction here. Chance didn't change their name, they were bought by Hubbell. Chance is now just a brand name under the Hubbell banner.