I know few guys who have gotten through 400v main with an excavator and just loud bang and scare. Those excavators are not insulated in any way, but the cockpit

I know few guys who have gotten through 400v main with an excavator and just loud bang and scare. Those excavators are not insulated in any way, but the cockpit does make Faraday cage. I think they usually continue working after booting every on board computer and getting a new bucket. The amount of insulation you need is minimal as the excavator blade/drill bit will work as conductor and most of the current then just follows the path it normally would. The flash and bang come from the short period of time when there is small air gap between the electric line and the tool being used and then that gap gets welded shut really fast. The amount of insulation you need might well be reached with just wooden handles on the drill. Or wearing rubber sole shoes.