Abstract: A liquid dielectric capacitor is provided housed in a sealed casing having a noncircular cross-section. The casing includes a sealed top cover to which terminals are affixed. An elongated flexible plate member is positioned within the casing spanning a major diameter of the casing. The ends of the plate member substantially abut the interior walls of the casing along the major diameter. Breakable, electrical conductors are affixed to the terminals and plate member. The plate member is preconditioned to bow downwardly, away from the casing top, when the ends of the plate member are subjected to inwardly directed forces, as when a pressure buildup occurs within the casing. The conductors are adapted to break when the relative distance between the terminal and plate exceeds a preselected value.