High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Air-current blowout
Reexamination Certificate
2001-04-02
2003-09-30
Donovan, Lincoln (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Air-current blowout
C218S064000
Reexamination Certificate
active
06627831
ABSTRACT:
The invention relates to an insulating component, which is at least partially composed of a plastic, for high-voltage systems, in particular for use in gas-insulated systems, whose conductivity is increased in the region of its surface, and to a method for producing such a component.
An insulating component is known, for example, from DE-C 26 26 855. Such dielectric components are used, for example, in electrical high-voltage switches, in particular in high-voltage power breakers, as spacers or as nozzles for carrying an insulating-gas flow.
An insulating component for high-voltage systems is known from DE 26 25 071 A1, in which surface regions are provided with increased electrical conductivity by means of implanted ions.
In encapsulated high-voltage switchgear assemblies, such components are used, for example, as supports for busbar conductors or as bushings. They may be composed, for example, of casting resin, for example an epoxy resin, or of PTFE (polytetrafluoroethylene), or a similar polymer.
Once subjected to a high dielectric load, that is to say in the presence of high electrical field strengths, especially when the field strength has a component tangential to the surface of the component, there is an increased tendency for displacement currents to flow on the surface of the component, which can also lead to electrical flashovers. Such flashovers can then initiate larger flashovers between conductors, and must therefore invariably be avoided.
According to DE-C 26 26 855, a poorly conductive fabric is embedded in the region of the surface of the component in order to dissipate surface charges.
An insulating component is known from DE 195 19 992 A1, whose surface roughness is increased in order to dissipate surface charges. The increased surface roughness results in uneven areas which promote tip discharges due to corresponding field distortion. This results in charge carriers being emitted and surface charges being dissipated.
However, mechanical machining of the surface is necessary to produce such a surface according to the prior art.
In contrast, the present invention is based on the object of providing an insulating component of the type mentioned initially, in which the dissipation of surface charges is assisted, and which can be produced and machined in a simple manner with little effort.
The object is achieved according to the invention in that the material of the component is treated with beta or gamma radiation in order to increase the conductivity at least in a region of its surface in which it is subject to higher dielectric loading during operation than in other regions.
The good mechanical robustness and, above all, the good insulation characteristics of the plastics from which such insulating components are produced result from the molecular structure, which has a large number of long carbon chains. These carbon chains likewise result in a high electrical resistance.
The measure of irradiation with beta or gamma radiation destroys the molecular chains in the region into which the radiation penetrates. This on the one hand makes it easier to carry out mechanical machining and on the other hand decreases the electrical resistivity, so that surface charges can be dissipated by electrical conduction in this region on the surface of the insulating component.
Experiments have shown that the decay time for surface charges is considerably shortened (halved) by such treatment of insulating components.
In that region of an insulating component which is not subject to any increased dielectric loads during operation, such treatment of the component is superfluous.
An advantageous refinement of the invention provides for the conductivity to be increased significantly to a depth of at least 5 mm in the at least one region.
Such treatment of the material to a depth of 5 mm, and advantageously to a depth of about 10 mm, results in the effect of reduced surface resistance being retained even if a part of the surface is worn away, for example under the influence of an arc, once the component has been used.
This is the situation especially when the invention is used in a dielectric nozzle in the interrupt unit of a high-voltage circuit breaker.
However, in the configuration according to the invention, the surface of such a nozzle body is only partially worn away even after a number of load switching operations, so that a material which has been treated by the irradiation and whose resistance has been reduced remains in the region of increased dielectric loading, and dissipates any surface charges which may be present.
A further advantageous refinement of the invention provides for the component to be composed of PTFE.
The production of dielectric components composed of PTFE or else of casting resin is quite normal in this field and can be carried out in widely different forms, without major effort, by casting or sintering.
The invention may also comprise a method for producing an insulating component, in which the component is subject to alpha, beta or gamma radiation in the at least one region.
In addition, the invention can be refined by the component being subjected to the influence of an arc, at least in the one region.
The immediate proximity of an arc subjects the component to increased beta radiation, which results in the desired effect occurring as a function of the intensity and the duration of the influence of the arc. This treatment with an arc can be carried out either instead of systematic irradiation of the component, or as a supplement to it. Particularly if the component is a nozzle body for a high-voltage circuit breaker, the component can be subjected to arcs systematically before or after being brought into use, even when installed, in order to achieve the effect according to the invention. The switching arc can be used as an arc for this purpose.
REFERENCES:
patent: 5151565 (1992-09-01), Perret
patent: 26 25 071 (1976-06-01), None
patent: 26 26 855 (1976-06-01), None
patent: 195 19 992 (1995-05-01), None
patent: 55-56002 (1980-04-01), None
Schmunk, Miller, Becker: “Tests on irradiated insulator materials”, Journal of Nuclear Material, Bd. 123, 1984, Seiten 1381-1385, SP000852523, (No date).
Donovan Lincoln
Morrison & Foerster / LLP
Siemens Aktiensellscraft
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