So I am a bit mystified by what happened. The box was energized.
You reached to throw the knife switch off, out of continuity.
As your hand was about to touch the cut-off lever, the box exploded.
A fireball 2-1/2' in diameter came out of the box from the arc fault.
You narrowly avoided a serious burn.
Is this correct?
If you were to the right side of the box and reaching for the knife switch w/your left hand, wouldn't that have put you into direct position to be burned by the arc fault energy?
I read Miles' comment about working on energized electrical equipment.
Did you have a big static charge built-up on you, that somehow jumped to the box?
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No static involved, only bad timing, smoke had start to come out of power box; so had to shut to power off.
All boxes open from its right side, the cut off handle is also at its far right,
so, when you have to shut it off or put it back on, we always use left hand palm freeing fingers from an expeted exploded opening door.
Also, you should look at oposite side of power box and put your right hand on your face left side and ears, protecting from arc.
It`s done mecanicaly, so when you look at experienced worker doing it; you maybe not remark all those moves.
Shut off power or put it back on by using right arm wich need you to put that fore arm in front of power box is verry dangerous; burning your arm and maybe get the power box cover in your face.
In my case, 600volt 30amp box was connected to a truf wich is protec by a 200 amp braker in electric room. I tell you, that 200 amp braker jumped off.
It`s not verry rare, but not an often issue,
first time in my working life wich is neerer to the end then the begening:biglaugh: