A capacitor is provided with a case having a receptacle with an expandable section that allows the receptacle to extend axially when internal pressure builds within the case as a result of a fault. Terminals are mounted on the cover and electrically connected to the electrodes of a capacitor element through an interrupter plate, via leads. The plate is attached to the section of the case that extends under pressure, whereby the plate is drawn away from the cover, thereby breaking the electrical connections to the terminal. The plate may also work in conjunction with a cover that expands outward in response to internal pressure, to provide a second pressure interrupter mechanism.