More than likely there is no explosion in that box. The standard procedure is to "fake" the effect with powder ejected by pressure and dub the sound effect. That could have been magnesium powder ignited by a spark gap and forced out by air pressure and the sound could be dubbed.
As far as whether you are out of your depth, all I can tell you is that there are no careless people working with high voltage and power, because they're dead. There are no second chances. The first careless incident is also the last. I'm over 60 and you won't live to be half my age with your attitude. We have arc flash shields at work that we stand behind during high risk tests.