Hi Clicon: Possibly your post #631 about the roof hoist ?
Did you get the fault sorted in the end ?
Thought so, wasn't sure. Not working on it personally but the fault seems to be not on the 400V winch or it's 230V control gear but with a supply flat cable on a catenary. They have managed to get it working and NOT tripping with a 30mA RCD in place fed from known "good" cabling. Trying that same RCD on site with the now suspect feed cabling and it tripped continuosly.