IMHO that's a rare event, usually instead of being continuously shocked, someone gets shocked and then in the worst case they die and you have to apply CPR until an ambulance can try to save them.

If someone is being shocked, live, then it all depends on the circumstances, but the most generic standard suggestion in various first aid courses seems to be using a non-conductive stick (e.g. broomhandle) to push them away from the source of power or vice versa. They have probably grabbed the thing with their hand and are unable to release it as the hand is cramped, so that may be difficult.

Finding a circuit breaker may be too long. My intuitive guess (though that's not something I have seen recommended) is that intentionally causing a short-circit and trip the breaker might be faster.

Kick them away (or sideways, basically anything to break their grip on the electrified thing they're locked onto) from whatever they're holding. Your shoes aren't conductive so you will be safe.

Alternatively, throw a scarf or other garment as a loop in between the victim and the source of the shock and use it to pull them away from it from behind them - the garment not being conductive means you'll be safe.