Zog

PG&E won a safety award for adapting this procedure, this is becoming common practice at power plants and industrial facilities across the country.

http://www.pgecurrents.com/video/new...t-power-plant/

mxslick

Watching the video, one thing kinda bothered me....while setting up the remote racking gear, shouldn't the workers still be in full PPE? I would think that ANY time the door to one of those breaker cubicles was opened it falls under the PPE requirements.

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Zog

That is a grey area in 70E, the whole "Interaction that is likely to cause an arc flash event" line they use. The 70E refers to task in the tables as examples like racking or operating a breaker, taking voltage measurements, or opening a cover to expose bare energized parts. For this type of breaker opening that door does not expose any bare energized parts so it is easy to argue that PPE is not required if you are not going to operate or rack that breaker. Some plants still require PPE to do it though, but most don't.

mxslick

Thanks Zog, that's the answer I was looking for.

In your experience, have you ever encountered a failure "unprovoked" by worker's actions when the door of a cubicle was opened?

I may be overcautious, but I have fears of a fault happening while the door is opened and causing a flash.

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MDShunk

I've had the door blow open on sidearm disconnects when turning them on, and I've had fire fly out of the vents on MCC buckets when pressing the exterior mounted "reset" button extension. There's a lot of "interaction" that can cause an arc flash event that you'd never really think of.

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Big John

That's a battle I'm going through right now.

I've seen enough breakers fail during normal operation that, regardless of 70E and "exposed live parts" my preference is to try and keep a fair bit of distance between people and breakers at all times.

This becomes even trickier in environments where breakers are remotely operated, and where the people in the potential arc-flash boundary have absolutely nothing to do with the breaker or operation.

-John

Zog

Yeah, I had a friend get burned just walking past a MCC on his way back from lunch, a motor was started remotely, the starter failed, enclosure failed, and he was burned on the arm and face.

But there has to be a limit put on risk, and that level of acceptable risk is affected by the hazard level. The problem is, 95% of electricians lack the training to understand how to evaluate the hazard level, hence the requirements we see now for arc flash labels on equipment.

Zog

Opening a panel containing live parts? Yes, seen it myself and have seen the results of it dozens of times. Opening a breaker door with no exposed live parts? No, can't say I am aware of one, but I have seen that to cause a breaker to trip more times than I can count, usually when indusction disc relays are involved, or some 60's vintage Westinghouse gear that had these stupid "door interlocks"

MDShunk

There is an OSHA standard (or, perhaps, an ANSI standard enforced by OSHA) that any manufacturing equipment that can automatically restart must sound an audible signal for 5 seconds before the equipment restarts. If a person was really concerned, that type of arrangement could be put into a control scheme for large breakers that remotely open and close.

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