Electricity: measuring and testing – A material property using electrostatic phenomenon – Corona induced
Reexamination Certificate
2002-09-11
2004-08-17
Patidar, Jay (Department: 2858)
Electricity: measuring and testing
A material property using electrostatic phenomenon
Corona induced
C324S456000
Reexamination Certificate
active
06777948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to high voltage electrical equipment. More specifically, the invention is directed to detecting wear in components of high voltage electrical equipment that are regularly exposed to electrical arcing.
2. Description of Related Art
Load tap changers, voltage regulators, circuit breakers and switches are used to interrupt power. The surfaces of some of their components are eroded by being regularly exposed to electrical arcing and mechanical friction during the course of their normal operation. Equipment failure results if these components are allowed to wear out to the extent that their electrical and mechanical integrity is compromised. Components most susceptible to erosion are the arcing metal contacts and TEFLON nozzles in sulfur hexafluoride (SF
6
) gas circuit breakers.
It is desirable to know when components of electrical equipment have become dangerously worn out without taking the equipment out of service to perform an internal inspection. Several approaches have been used to accomplish this. One approach is installing fiber optic strands into the electrical contacts of the electrical equipment. As the contacts wear, the fiber optic strands become exposed to light emitted from electrical arcing, which may be detected by a photodiode or other sensor placed at the opposite ends of the fiber optic strands. Installing fiber optic strands in electrical contacts is expensive, however, and the fiber optic strands are subject to breakage as a result of mechanical stress. Another approach embeds tracer materials at predetermined depths in the electrical contacts or below the surface of a TEFLON nozzle of a SF
6
circuit breaker. When the electrical contacts wear to the point that the tracer materials are exposed, the tracer materials are released into the insulating medium or else are decomposed by the electrical arc. In order to determine whether wear has proceeded beyond a safe level, the insulating medium must be withdrawn and analyzed periodically for the presence of the tracer elements or the products from their decomposition. This approach is not suitable for continuous monitoring of the electrical equipment.
Based on the foregoing, there is a need for a way to continuously monitor for excessive wear of the components of electrical equipment that are susceptible to erosion by being exposed to electrical arcing and mechanical friction.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to detect excessive wear in components of electrical equipment by monitoring them continuously.
This object and other objects are provided by the present invention, one embodiment of which comprises a method of monitoring a component of an electrical device for wear by exposing a component having a tracer material embedded in it at a predetermined depth to an electrical arc, wearing the component until the tracer material is exposed to the electrical arc, and detecting electromagnetic radiation emitted by the tracer material when the tracer material is exposed to the electrical arc. The electromagnetic radiation emitted by the tracer material is distinct from electromagnetic radiation emitted by any other parts of the component; for example, it may have a different wavelength. The component is preferably monitored continuously to detect electromagnetic radiation emitted by the tracer material. Another embodiment of the present invention comprises a method of manufacturing a component of a device in which an electrical arc may be generated wherein the method involves embedding a tracer material within the component at a predetermined depth.
Yet another embodiment of the present invention comprises an apparatus for detecting wear in an electrical device in which a tracer material is embedded at a predetermined depth within a component of the electrical device. As in the other embodiments, the tracer material emits electromagnetic radiation when the tracer material is exposed to an electrical arc that is distinct from electromagnetic radiation emitted by any other parts of the component; for example, it may have a different wavelength. The apparatus preferably includes an electromagnetic detector, such as a photodiode having a narrow bandwidth filter or spectrophotometer, to continuously monitor the component for electromagnetic radiation emitted by the tracer material. A fiber optic cable may be used to transmit the electromagnetic radiation to the electromagnetic detector. Suitable tracer materials include lithium, cobalt, niobium and rare earth metals, such as yttrium. In addition, multiple tracer materials may be embedded at multiple pre-determined depths and/or at pre-selected locations within the component in order to detect the extent and/or location of wearing in the component.
These and other objects and features of the invention will appear from the following description from which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.
REFERENCES:
patent: 3715598 (1973-02-01), Tomlin, Jr.
patent: 5389792 (1995-02-01), DiMarzio et al.
patent: 5453591 (1995-09-01), Stroud
patent: 5844331 (1998-12-01), Kieser et al.
patent: 6023036 (2000-02-01), Nichols
Casson David W.
Dominelli Nicola
Hall Edward A.
Schellhase Hans
Electric Power Research Institute Inc.
Nguyen Vincent Q.
Patidar Jay
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