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 Post subject: Blowing Doors Open / Off
PostPosted: Mon Oct 17, 2011 11:55 am 
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I know this has been discussed in various forms here but I have a specific question.

How many of you have had an arc flash where the doors actually blew open or off? It seems this can happen in a lab or maybe in an extreme case but I have not heard of many (any?) "real world" cases. I would be interested to hear your stories (or lack of :) )


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PostPosted: Mon Oct 17, 2011 12:47 pm 
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Great question! I have seen the videos of some pretty bad arc flashes but my own experience has been just a couple of small events :o years ago and in each case the panel cover was off.

I imagine if a switch fails or racking a breaker with doors closed goes terribly wrong and there is enough energy, then blowing the doors off might be possible but I also wonder how common it is? - although even if it is 1 in a billion, I would not want to be that "1".


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PostPosted: Mon Oct 17, 2011 12:58 pm 
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I see it very often (Maybe 20 times this year so far), then again we are the people that usually gets called when switchgear blows up. I would like to post photos but that can be sensitive.


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PostPosted: Mon Oct 17, 2011 1:32 pm 
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Zog wrote:
I see it very often (Maybe 20 times this year so far), then again we are the people that usually gets called when switchgear blows up. I would like to post photos but that can be sensitive.


Could you post them with identifying info blotted out? That would be a big help to the doubters that are here.


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PostPosted: Tue Oct 18, 2011 5:40 am 
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I would if I could, but I can't. Don't have permission to publish.


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PostPosted: Tue Oct 18, 2011 10:58 am 
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Zog wrote:
I would if I could, but I can't. Don't have permission to publish.


Zog, can you provide any details on these "many" events...kV, kA, equipment type or manufacturer, protection scheme, cause of failure, worker activity or interaction, commercial or industrial setting, injuries, etc?


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PostPosted: Tue Oct 18, 2011 12:09 pm 
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SCGEng1 wrote:
Zog, can you provide any details on these "many" events...kV, kA, equipment type or manufacturer, protection scheme, cause of failure, worker activity or interaction, commercial or industrial setting, injuries, etc?


Power plants, heavy industrial mostly. 480V - 15kV switchgear. Most often the 480V Main or transformer transition section, high fault currents, long clearing times.


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PostPosted: Wed Oct 19, 2011 12:55 pm 
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The 2012 Edition of NFPA 70E has a disturbing Informational Note 2 under 130.7 (A) stating that their collective genius finds 600V or less enclosed systems not likely to expose an employee to an electrical hazard. I have seen the aftermath of 480V gear, variable speed drives, and MLO MCC's where things were less than contained by the enclosure. Of course the standard goes on to talk out of the other side of their mouth in 130.7 (C) (15).

The more impressive pictures are from the MV gear but we also ran into an instance where an arc flash in a 4160V switch ocureed while an electrician was re-energizing. Most of of the energy was contained but the buckling door dislocated his hip. The equipment photos don't look too bad but the effect is very real.


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PostPosted: Wed Oct 19, 2011 1:41 pm 
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OK, here is an old one, don't even remember where this was from. In this case the doors held, likely thanks to the vents, but the side of the gear failed.


You do not have the required permissions to view the files attached to this post.


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PostPosted: Thu Oct 20, 2011 12:29 pm 
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Impressive. Was anyone injured from any flash making it though the vents or the new hole in the side?


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PostPosted: Thu Oct 20, 2011 6:52 pm 
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That is an old one, I don't recall the circumstances, but don't remmember any injury that went with it either.


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PostPosted: Fri Oct 21, 2011 2:30 pm 
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An outdoor vacuum in air 15 kV circuit breaker flashed over. The condensation prevention heater and thermostat in the high voltage compartment was set from the factory to zero so that it never came on in our climate. Condensation built up on the bushings and interrupters until a flashover occurred. The high voltage compartment doors were bolted on and held, but the high voltage compartment vented into the low voltage compartment below and blew those doors open. This occurred when no one was present, so no injuries occurred. Breaker spec now calls for the thermostat to be located in the low voltage compartment where it can be checked more easily.


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PostPosted: Wed Nov 02, 2011 7:58 pm 
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I went to a company to review repairs needed after they had a 480V, 1600A Westinghouse DB-50 breaker arc flash on them. Not sure if you have ever seen one of these breakers, but the metal frame is about 1/2" thick and half the breaker was GONE! It disintigrated the door to it and the back of the bucket it was in to where I could see straight through to the back main buss. About 5' around it was singed badly. I did not whitness this arc flash, but it must have been very bad! Other than transformer explosions, this was the worst case I've seen.
In general, I figure if it's Category 2 or more, there is a high probability of having enough blast potential to blast the door open.


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PostPosted: Thu Nov 03, 2011 5:40 pm 
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BruceJAX wrote:
I went to a company to review repairs needed after they had a 480V, 1600A Westinghouse DB-50 breaker arc flash on them. Not sure if you have ever seen one of these breakers, but the metal frame is about 1/2" thick and half the breaker was GONE! It disintigrated the door to it and the back of the bucket it was in to where I could see straight through to the back main buss. About 5' around it was singed badly. I did not whitness this arc flash, but it must have been very bad! Other than transformer explosions, this was the worst case I've seen.
In general, I figure if it's Category 2 or more, there is a high probability of having enough blast potential to blast the door open.


DB's are scary, perhaps the most scary for racking, and besides a "current production insulated case breaker", I have seen more DB failures than anything out there.


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PostPosted: Mon Dec 05, 2011 3:19 pm 
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C. Marsh wrote:
I know this has been discussed in various forms here but I have a specific question.

How many of you have had an arc flash where the doors actually blew open or off? It seems this can happen in a lab or maybe in an extreme case but I have not heard of many (any?) "real world" cases. I would be interested to hear your stories (or lack of :) )


I see multiple instances every year, unfortunately for the same reasons as posted above, I can't post pictures.


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