Internal unbalance detection in capacitors

#The present invention relates to internal unbalance detection in capacitors using circuitry internal to the capacitor, and more particularly to the pre-detection of capacitor section failures within a capacitor. Even more particularly, the present invention relates to the detection of capacitor section failures within a capacitor using internal circuitry and, for example, a fiber optic output, wherein capacitor failure is detected upon, for example, a detected failure of a prescribed number of capacitor sections and capacitor failure is pre-detected, i.e., incipient capacitor failure is detected upon, for example, a detected failure of a predetermined lesser number of capacitor sections. Even more particularly the present invention also relates to detection of incipient capacitor failure with a widely varying voltage on the capacitor, without the need to recalibrate the detection system to account for the widely varying voltage.

#Present day operational equipment and research devices require the use of large capacitors connected in banks, and in some instances employ capacitor sections connected in commonly-housed capacitors. As used herein the term capacitor section refers to a single capacitor element, e.g., in general, a pair of conductive structures, e.g., plates, separated by a dielectric material. The term capacitor refers to a functional electrical component made up of at least one capacitor section, and having at least two externally accessible electrodes through electrical connection can be made to the one or more capacitor sections. The term capacitor module refers to that portion of, for example, a high voltage device, such as an accelerator or a laser, made up of at least one capacitor, and associated hardware. By high voltage it is meant a device operating at, for example, more than 5 kilovolts, e.g., 10 kilovolts.

#Standard practice for high voltage capacitors dictates that each capacitor consists of several parallel series of high voltage capacitor sections in a sealed casing (or housing).

#The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:

#FIG. 1 is a perspective view of an exemplary capacitor in accordance with an embodiment of the present invention;

#FIGS. 2A, 2B, 2C and 2D are a schematic diagram illustrating a progressive short circuit failure sequence, in a capacitor such as the capacitor of FIG. 1;

#The following description of the presently contemplated best mode of practicing the invention is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.

#Referring first to FIG. 1, a perspective view is shown of an exemplary capacitor 10 in accordance with an embodiment of the present invention. Shown is typical of an example of a large high voltage double ended capacitor 10 having a first electrode 12 and a second electrode 14. (By high voltage it is meant a capacitor capable of operating a voltage of, for example, 5 kilovolts or more, e.g., 10 kilovolts.) Also shown is an output port 16 through which a fiberoptic cable connection is passed through a housing 18, such as a plastic insulated housing, in order to provide an unbalance detection output.

#Advantageously, in accordance with the present embodiment, the unbalance detection output signals at least three possible conditions: balanced; unbalanced with predetection of capacitor failure; and unbalanced with detection of imminent capacitor failure. Thus, unlike in prior art approaches, the capacitor 10 of the present embodiment can be taken offline and replaced during a scheduled maintenance operation when predetection of capacitor failure is signaled as opposed to merely taken offline immediately upon the detection of an imminent capacitor failure. At the same time, should the capacitor 10 fail more quickly than expected, i.e., before scheduled maintenance can be performed, an interlock mechanism, such as is known in the prior art, can be used upon the signaling of imminent capacitor failure to remove the capacitor 10 from service, as well as shut down related systems, before catastrophic failure of the capacitor 10 occurs.