I was working at a creamery in the UK near Chard in England. I was installing a new and expensive process control system that had the computers mounted inside a stainless steel enclosure. A Danish company was also on site, performing some stainless steel pipe installation. A Danish welder put the ground clamp on the exterior of my computer cabinet. It fried everything in that cabinet and also fried other electronics remotely located in the plant that had wires interconnected. After that, I always disconnect the negative battery lead, regardless of whether I think I really need to.