Internal fault indicator for power electrical devices

A fault indicator for indicating the occurrence of a rapid pressure surge within a housing of an electrical device, the fault indicator comprising:

• a) pressure surge detecting means for moving an actuating member in response to a rapid rise in pressure within a housing of an electrical device;
• b) indicator means actuated by the pressure surge detecting means, the indicator means comprising a plunger movably disposed within a bore, the plunger movable outwardly in the bore from an armed position to a triggered position upon movement of the actuating member;
• and,
• c) retaining means for preventing the plunger from becoming separated from the fault indicator.

A method for indicating the occurrence of a rapid pressure surge within a housing of an electrical device, the method comprising:

• a) providing a chamber within a housing of an electrical device, the chamber comprising an enclosed volume and an orifice communicating between the enclosed volume and an air space within the housing and providing a plunger having a hidden portion which is hidden from view;
• b) allowing a rapid pressure surge within the housing to displace a wall portion of the chamber inwardly;
• c) in response to motion of the wall portion releasing a plunger;
• and,
• d) moving the plunger so that the portion of the plunger which was hidden from view is exposed.