Electrical Question

Something like this maybe. Keep in mind this was 5 mins of searching on google. There is probably a much better one out there, but it gives you an idea of what you need.

http://www.electrokits.com/electronics/relays-remotes-switches-timers/36.htm

You set a dip switch to your time limit. Ex. 1 hour. Everytime power is applied it starts counting down. When power is lost, it dies. Then starts all over again.

You could put a "Y" splice in your wire, and run your hot and neutral to the relay, so when it trips, its a direct short to your breaker. Not the best option to direct short your breaker, but this circuit should only be used if you have a leak or something, so it probably will never be used at all.