Whether single or poly-phase, circuit breakers don't sense fire.

As John said, 480V will leave a very memorable and lasting impression.
I saw such "ball lightning" events when I was in the maintenance dept of a
steel wire mill facility, and in a new area that had only been in operation
for over a year.

You can expect to be showered with grinding dust any time anything
structural is disturbed.
All of the overhead pipes, cables, rafters/stuff are likely to be loaded
with that dust.

By the staining on the walls, it looks like that business had been there for
quite a while.. the yellowing is likely from evaporating (and/or misted)
coolant.

Anything valuable or pristine should be kept under cover.. and it's not a
good place for kids to hang out.
Aluminum oxide dust is bad enough to inhale (and conductive), but silicon
carbide dust is very nasty, in case you haven't been reading those caution
labels or MSDS info sent with SiC products.

Those hanging receptacles may not be installed properly. The best type of
cable to use is the stuff designed for hanging switches/etc (such as on a
hoist) which has an internal steel cable for securing at each end, which
prevents stretching of the conductors.
The boxes shouldn't have been the common type (covered in knockouts) for use
in that kind of shop, and the box connectors should've been the sealing
type.
Details like these will give you an indication of what can be expected when
you need to use, or make changes to, the electrical circuits.
When you see improvised/improper installations, it's likely because the
installer didn't know any better (unqualified inexperienced), and/or because
no one would spend the money to do the job correctly.

A much better installation is to install posts with the boxes mounted to
them.

--
WB
..........


"Ignoramus23561" wrote in message
...
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i