In Polk County (Florida) a lot of phosphate rock it mined by self propelled "dragline" excavators.... they are electric powered, and drag 10+" diameter power cords and sub stations with them... copper thieves have taken to building "guillotine" cutters on the back of pick up trucks... I don't know how much current a 10" cable can carry, but the local sheriff's office has found several "crispy critters" in the past couple of years...