One time when I was working on an electronic organ, the customer turned it on. Fortunately, nothing happened. After that, I built a box that the organ is plugged into. It had a fuse, switch and other goodies for troubleshooting. The point is now I had complete control.
I did the same thing with my lathe and mill. On the right side of each machine is a "master box" that contain a master power switch. Besides the switch, the box contains three ac plug-ins and the lights above the machine are hard wired. That way when I turn on the main switch, the lights turn on and I know power is being sent to the machine. If I need to work on the lathe or mill, I simply unplug the machine, since it is so convenient, Yet I still have my lights. These are 110-volt machines, but you guys with 220 units could probably come up with something similar.