Safety reminder

[bukwirm]

You can get little devices that lock onto breaker handles so that you can lock out breakers that don't have built-in provisions for locks (example). They work reasonably well - someone could probably pry them off, but it would take some effort.

 

[rwm]

I have lockout devices on some of my home breakers that have hardwired appliances without local service disconnects (i.e. oven). I don't know what code is now. I suspect the industrial setting is different anyway.

 

[K30]

Arc flash is metal and/or air being converted to plasma and expanding with great vigor...

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For illustrative purposes, water to steam is about a 1600:1 expansion ratio. Copper bus bar to plasma is about a 70,000:1 ratio. It acts like a bomb.
We got water into a 13,800V-480V dry three phase transformer a while back, and faulted it out phase to ground, that propagated into phase to phase to phase to ground. The upstream breaker cleared it in about 10 cycles. I had to go take a look inside the enclosure to get "an idea how bad it was" (um, you faulted it, it's junk...). The core weighed 4200 lbs, and i measured the shift in position at about 8". Oh, did i mention one of my guys was on the phone 6 feet away at the time?

 

[MikeWi]

Ok, so really stupid question here: I've youtube videos of two people in silver fire suits, one with a shepherds hook to pull the other away in case of a disaster, while the first sucker, er. guy actually engaged the circuit. What in the heck is preventing them from building these in such a way that you don't risk your life simply energizing the circuit?

 

[Weldingrod1]

They do rate enclosure for energy. However, it may just not be feasible to rate them for cosmic catastrophe. Plus, leaving a tool across the bus bars is NOT according to design!

Having extra protection for the FIRST switch on is just sensible. #2 is much lower risk.

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[K30]

There's also a big difference between load-break and non-load break switchgear.

 

[rwm]

Engineer: I try to make things idiot proof but they keep making better idiots...

 

[verbotenwhisky]

Engineer: I try to make things idiot proof but they keep making better idiots...

That is my favorite saying, I use it often. "if you try to make it idiot proof you'll only develop a better idiot".