over-voltage protection is a certification requirement in CS23 and later versions of FAR23. On all systems that I've come across (Lamar, Electrodelta etc) the over volt system will interrupt the field supply, not trip the breaker. Pilot action is always required for an over-voltage reset -it should never automatically clear the fault. Older Pipers used a separate relay as the protection device. Most later Cessnas have the protection within the voltage regulator although early 28v aircraft have a discrete over-volt unit mounted just above the park brake handle. You very rarely find an over-volt protection on an aircraft with a generator but normally always with an alternator.