The mine and mill that I work in were built in the early 1960's. All of the original controls are 480vac delta. Quite alot of them don't have and EGC either, mostly solid wire. Hard part is explaining how the voltage is present on hot and reutrn side of the cicuit with the switch open.
MSHA has it's own set of rules when it comes to electricty, otherwise how could you drag a 200 foot long cable behind a machine running on 480vac? And allow the operator to move it into and out of hangers when it's energized?
