Electrician Talk banner

Mistakes & Mishaps

111K views 929 replies 80 participants last post by  radio208 
#1 ·
Bet That Left A Mark

 
See less See more
1
#20 · (Edited)
We saw that video in masters class. My masters teacher was a state fire investigator and he slowed the video down and showed us how that guy is reduced to a pile of ash. He paused it a few times and you can actually see his hard had pop off his head. My teacher said he probably felt minimal pain.
 
#21 ·
Probably would have done more good if he said the guy felt it all and died slowly.

Too many guys take unnecessary chances for no reason.
 
#27 ·
It's hard to be sure, but it looked to me like he was reeling in a steel fish tape.

Then it looked like he'd reached the head and stuck his own head down to pull the last of the conductors towards him.

If the head was massively soaped// pulled a lot of water up from the U/G run...

Then it splashed across the energized busing and the plasma blast made him a conductor, too... as his very wet hands were still on the steel and current was jumping to ground from the hots.

Why was he messing around with hot busing nearby ?
 
#29 ·
The breaker failed - I believe while being racked out but I could be wrong. I actually got to see that same model breaker that had suffered the same mode of failure once while at a training seminar. If memory serves, that particular model had a design flaw that caused a retainer around the bus fingers to develop a stress crack and fail over time, allowing all the individual fingers in the cluster to fall out into the buswork. I'm pretty sure it was a 5kV breaker, too.
 
#35 ·
I won't speak to the accident; I did not watch the video. I have seen two closely related events like it. I'm good.

I do have plenty of experience with the old Westinghouse DH series MV gear and DB series LV ACB's. Both had the infamous finger clusters, and both were notorious for breaking the POS stamped sheet metal retaining rings. The DH's were round and the DB's were rectangle. The round retainer rings would break just anywhere, but the rectangular rings usually broke at one of the corners. And yes, when a retainer broke, it often sent twenty or thirty fingers and finger springs clinking and clanking down through the cell.

I watched one evening as a 600 amp DB finger cluster broke during insertion and literally disintegrate the low side of an outdoor substation. The blast knocked my electrician clear out the door, scared ****less but unharmed due his proper PPE (40 cal). The 15 kV high side never did trip (sub setup was HV-transformer-LV). I stood there as long as I could and ended up opening the 15 kV side myself with only level 2 PPE. Yeah, maybe not my most brilliant moment, but the conditions weren’t getting any better and I really didn’t want the fire to escalate to the transformer or HV switch.

I also lost a 5 kV DH breaker due to the same issue. I actually found and purchased a replacement breaker through a gentleman whom I “met” on this very forum who specialized in vintage switchgear (among other things).
And when I set up our air circuit breaker rebuild shop, I found and instituted modern aftermarket re-designed replacement retainers. We never had another failure due to broken finger clusters again.

I write this only as an FYI to some of you younger guys who may come across an old DH or DB from time to time. Please examine the finger clusters (and cell stabs) carefully before you rack. And always do a megger, hi-pot, or at least meter test to any LV or MV breaker or switch you are about to insert as well. You may be glad you did. I have lots of stories.

Cheers,
Mark
 
#30 ·
Both guys in the video seem to be working almost external of the cabinet. They look more like pulling a snake than cranking motion, especially looking ta the second guy to come into view.
 
#36 ·
A quick rundown on medium-voltage (over 600, up to 35,000 volts) breakers like the one in the video;

The ones I've worked with are about 3' X 3' X 3' and have wheels that roll on a track. There's a long screw, usually about 1/2" diameter that is used to 'rack' the breaker in and out of its cubicle. This screw is turned by a speed wrench (kind of like a crankshaft). There's a socket on the end, usually a basic 3/4" 6 point and you need to push it in against a fairly strong spring and turn at the same time.

In other words, you need to be right in front of the breaker while racking it in or out, you can't stand off to the side.

The back of the breaker has some sort of jaw type set-up that goes onto the busbars. When the breaker is racked in, the jaws are connected to the busses, when it's racked out, the jaws are about 2' from the busbars. This is because most of us are not very comfortable working on stuff when the only thing separating you from an almost always lethal voltage is a vacuum bottle with contacts inside. If it loses its vacuum, it'll arc over......and you're dead.

It's important when racking a breaker that absolutely no load is present on the load side. If there is any kind of load, the jaws will arc when they get close to the busbars and BOOM!!!!

Every breaker that I've worked with has both electrical and mechanical means to trip the breaker open when it's being racked in or out. But these can fail. Also, if one or more vacuum bottles has lost its vacuum, bad news.......Even dust that conducts can cause an explosion.

I hate racking breakers into hot gear.........
 
#39 ·
Years ago I was doing work at the an airport. They had a few failures racking in breakers that caused shutdowns. Luckily no one was ever hurt, this was before anyone wore arc flash suits.

The high voltage electrician was telling me how big the flames were and how nervous they were when cranking in the breakers.

I looked over in the corner of the room there was a remote racking machine. I I was like why don't you just use the remote racking machine...he was like whats that?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top