High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Multiple break
Patent
1995-11-20
1997-09-02
Scott, J. R.
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Multiple break
218 5, 218 6, 218 10, H01H 3314, H01H 3366
Patent
active
056635443
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is based on a switching device. A switching device of this type is preferably used in a high-voltage power supply and preferably serves there to switch large currents having a high transient recovery voltage rate.
2. Discussion of Background
The invention refers to a prior art such as is specified, for example, in U.S. Pat. No. 4,087,664. A switching device for a high-voltage power supply described in this prior art contains two current connections, between which a compressed gas-blast circuit-breaker having SF.sub.6 as quenching gas and a vacuum circuit-breaker are arranged in series. The vacuum circuit-breaker is designed such that it can carry and switch both rated and short-circuit currents. Such a vacuum circuit-breaker is therefore very costly. In addition, the vacuum circuit-breaker is driven separately from and in synchronism with the compressed gas-blast circuit-breaker. Since the vacuum circuit-breaker has a considerably smaller travel than the compressed gas-blast circuit-breaker, this produces, moreover, a considerable outlay for the drive and control of the vacuum circuit-breaker. In addition, the vacuum circuit-breaker requires a very high contact pressure force in order to prevent premature lifting off of its electrodes, through which, if appropriate, short-circuit current flows, in the switched-on state.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a novel switching device of the type mentioned in the introduction, which can be produced and operated with little outlay and which, nevertheless, can interrupt large currents having a high transient recovery voltage rate.
The switching device according to the invention is distinguished by virtually maintenance-free operation and an outstanding switching capacity. Since there are no stringent requirements imposed on the at least one vacuum circuit-breaker in respect of the breaking capacity and the continuous current-carrying capacity, the switching device according to the invention can also be produced extremely cost-effectively. The at least one vacuum circuit-breaker can be a standard product which is used in large numbers in medium-voltage technology and is therefore particularly inexpensive. This is due to the fact that the at least one vacuum circuit-breaker is shunt-connected with a rated current path of the compressed gas-blast circuit-breaker and therefore carries, during rated current operation, at most a small fraction of the rated current flowing through the switching device. It is not until a specific short-circuit current value is exceeded that the vacuum circuit-breaker of the switching device according to the invention is commutated into the current path which now carries short-circuit current. The high short-circuit current flowing through the Vacuum circuit-breaker generates large electrodynamic forces which drive the electrodes of the vacuum circuit-breaker apart and thus interrupt the short-circuit current.
These electrodynamic forces are completely sufficient, given appropriate dimensioning of the short-circuit current-carrying path, to separate the electrodes of the vacuum circuit-breaker from one another to such an extent that the interruption of the short-circuit current is ensured.
It is additionally possible, as a result of suitable arrangement of the vacuum circuit-breaker, also to utilize drive assistance, which is easy to coordinate, from the compressed gas-blast circuit-breaker during the separation of the electrodes by the electrodynamic forces of the short-circuit current.
A particularly advantageous design of the switching devices according to the invention does not contain the at least one vacuum circuit-breaker, but rather a module having two or more identical vacuum circuit-breakers which are aligned and connected in parallel with one another. Such a module has the additional advantage that, as a result of the division of the short-circuit current between a plurality of small vacuum circuit-breakers having
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patent: 4814559 (1989-03-01), Stegmuller
patent: 5276286 (1994-01-01), Demissy et al.
patent: 5347096 (1994-09-01), Bolongeat-Mobleu et al.
ABB Research Ltd.
Scott J. R.
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