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#178975 06/18/08 09:47 PM
Joined: Oct 2002
Posts: 482
Z
Zapped Offline OP
Member
Watch and wait until about 1 minute 13 seconds then see the fireworks. All that I can say is I hope both of these guys made it home.

Any ideas on what caused this? Looks to me like the tech at the box was being a bit aggressive and was maybe in a hurry. Rule number 1 and 2 to avoid when working hot.

http://www.liveleak.com/view?i=995_1213752982

Terrifying...

Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
I saw that ... it looks like they're pulling wire ... the sustained arcing would be consistent with a fish tape contacting the bussbars.

Joined: Aug 2001
Posts: 599
N
Member
It looks to me like he was racking in a breaker.

Joined: Jan 2005
Posts: 315
L
Member
I am going to agree with Nick. I appears to me they are racking in a breaker. If you look close you will notice the men are cranking something in a circular motion. The same motion used to crank( rack) in a breaker in that type of gear.

Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
I stand corrected ... I looked at it again, this time at 'fullscreen,' and you're right. You can see them cranking one way, then the other, and back again ... and trading places. Looks like there was some reason it didn't want to seat ... the rest is history.

Joined: Nov 2005
Posts: 826
J
Member
OK, here's my guess. They had it out for maintenance and had the arc chutes out. They have open and closed gap settings to check so they use a feeler gage. Somehow they get the arc chutes back in with metal stuck between phases, They shouldn't have even had access to the 3/4" bolt or square drive to crank if the breaker was closed. So unless a failed shutter of some kind caused the fault, I'll bet they left hardware in the breaker.
Joe

Joined: Sep 2005
Posts: 120
Z
Zog Offline
Member
Joe, seriously, come on, why would you ever have a feeler gauge (in the cell) on a breaker like this? And what are you talking about they shouldnt have had access to the racking screw? This switchgear dosent have shutters so that makes no sense, you are way out to lunch on this. Sorry. How much "Maintenence" have you done on this gear?

Racking mech problem, you can se him racking in, get stuck, rack it back out, back in and torque it hard. Obviously the primary disconnects were misaligned and snapped off, common arc flash cause, operators not properly trained on the equipment. I am suprised the shear pin didnt break on the pantagraph screw like it should have before this happened.


MV/HV Testing Specialist, "BKRMAN"
Joined: Nov 2005
Posts: 826
J
Member
Zog, I was serious. I wouldn't have anything in the cell. If I had a breaker out for maintenance, the DS units that I have worked on, get their red arc chutes removed. Then we have one gap to check with the breaker open and one gap when closed. I also remember having to loosen 4 bolts because the contacts were rotated slightly on some breakers. We would then have to go through the Digi-trip settings with the Amptector. This was an activity that my group got stuck doing on regular time, 3 Saturdays a year, per contract. I'm certainly no expert from doing it 3 times a year, but I thought you couldn't lift the flap to get to the bolt on a closed breaker. I also thought that, on at least some cubicles, a shutter comes down as you rack out the breaker. Am I wrong there? I couldn't tell whose AC SWGR it was from the viewing angle but it looked like it could have been the type that I work with.

If you thought my first guess was silly, how about my second guess? They took out the main breaker and were trying to rack in a spare while they worked on the main. Guesses are guesses. No harm, no foul for a bad one.
Joe

Joined: Aug 2003
Posts: 99
Member
That was a massive bit of arcing, Is there any more info on how it happened?

Joined: Feb 2007
Posts: 65
B
Member
What about PPE? What sort of PPE would normally be required for breaker maintenance (assuming that is what they were doing)?

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