When your home breaker trips and you reset it , and the oven is still on, that is a mechanical failure. The way the relay works is a coil is briefly energized and closes contacts, no more powers is applied to the coil, the contacts stay energized because of emf (current running through the conacts ) make act like a magnet. if for any reason the circut is interupted they open ( if the spring is good) and the process must start all over again. Try this : wait until it trips unplug it and hit the relay with the back of the screw driver. couple of times. then plug it back in and THEN reset the breaker. if oven is not on you found the problem. And the reason your tripping is because they use pulsed heat, it is just staying on.