High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Auxiliary shunt
Reexamination Certificate
1999-08-16
2001-04-03
Scott, J. R. (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Auxiliary shunt
C218S048000, C218S065000, C218S146000
Reexamination Certificate
active
06211478
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a switching arrangement in particular for power switches such as those which are used in power plants, transformer substations and other electrical power supply facilities, in order to switch operating and excess currents on and off, and to a method for its production.
2. Discussion of Background
Switching arrangements of the generic type are known, in which in particular parts of switching contacts on which the roots of the arc which is formed during switching are situated consist of material which is particularly resistant to contact erosion. Such material is usually produced by sintering a mixture of metal powders e.g. tungsten as a high-melting component and copper as a lower-melting component. This sintered material is relatively difficult to process. In particular, it is extremely brittle and can only be shaped by means of processors which remove metal. It cannot be welded in a customary manner and can only be joined to other materials by comparatively complicated processes, for example by having copper cast behind it, by friction welding, by flush butt welding or electron beam welding or by soldering which, however, produced a comparatively weak joint, or may be removably joined by means of a screw connection, which, however, requires complicated machining. The provisions of parts or coatings which are resistant to contact erosion therefore generally requires a high level of outlay.
Since in practice the material which is resistant to contact erosion cannot be deformed, the possibilities for shaping a base body which is to be provided with a coating which is resistant to contact erosion are extremely limited. Owing to the brittleness of the material, it is also impossible to provide flexible parts with a coating which is resistant to contact erosion. For these reasons, it is generally deemed sufficient, for example, to use tips of switching pins, arcing rings and similarly simple parts which are made from material which is resistant to contact erosion. Other parts of the arcing chamber and areas which adjoin the latter, which are also exposed to the hot gases generated when opening the switch, on the other hand, remain unprotected.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a novel switching arrangement of the generic type which is easy to produce, and a method for its production.
The advantages which are achieved by the invention are, in addition to the fact that the switching arrangement, in particular its parts which are resistant to contact erosion, are easier to produce, lie primarily in the fact that there are considerably wider options for the application of protective layers which are resistant to contact erosion. For example, according to the invention protective layers can be applied to parts of virtually any desired shape in a variable thickness and even with a variable composition. Due to their greater flexibility, protective layers can even be applied to flexible, in particular elastically deformable parts without the flexibility of these parts being significantly impaired and without there being any risk of crack formation in the protective layer.
The possibility of applying protective layers which are resistant to contact erosion to virtually any desired surfaces according to local requirements eliminates significant restrictions on the design of switching arrangements, in particular of the switching contacts, and makes it possible to implement designs which otherwise would have limited or no suitability for practical applications. As a result, there is considerably greater freedom when designing switches.
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Schoenemann Thomas
Zehnder Lukas
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Scott J. R.
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