A device for detecting vacuum loss in a vacuum breaking apparatus that includes an enclosure having a first part at least partially of insulating material, closed at its opposite ends by end-plates, and housing fixed and mobile electrodes. A second part of the enclosure is insulating material at least partially around the first part, this second part is an over-molding of electrically grounded conductive shielding at least a part of its outer surface. This first strip of over-molding faces both the first part and one of the electrodes, thereby providing two capacitances in series, namely, a vacuum capacitance between the electrode and the inner surface of the first part, and a solid capacitance between the inner surface of the first part and the first strip, and means for measuring change of current value in the first strip, which corresponds to a vacuum loss inside a vacuum breaking apparatus.
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