I really like the AU tri-prong system for this - high-current plugs/sockets have a physically larger ground connector.

This means you can put a low-current plug (small ground pin) into a high-current socket (large ground slot), but not the other way around.

Only downside I've found so far is that you can't use a high-current-rated extension cord to plug a low-current appliance into a low-current socket.

We’re not talking about high current anything, we’re talking about standard mains electricity.