Indeed.Oh that's a good question as i don't have one. Highest power item is the 3kw kettle. I can measure the pssc again when i get the chance as i can't really remember accurately, then you can calculate from that for any theoretical load.
WEll, with the alleged maximum TN-C-S Ze of 0.35 (presumably at the origin of an installation), you would get a drop ('an additional drop' of 28V - so I suppose the answer (for TN-C-S) would be 'no more than a 28V drop'.Who knows what would happen if i tried to take the full 80A or whatever.
Kind Regards, John