Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Patent
1998-10-27
2000-11-21
Leja, Ronald W.
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
361127, H02H 100
Patent
active
06151201&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a gas-insulated semiconductor valve means for high voltage and for high power, which comprises a stack of valves with a plurality of semiconductor elements electrically series-connected between a first and a second electrical main connection. The valve stack has a longitudinal axis and the main connections are arranged at opposite ends of the longitudinal axis of the stack. The valve stack is provided with electrostatic shields for reducing the stresses on the insulating gas.
The concept "high voltage" as used in this application relates to a valve voltage exceeding about 50 kV, and the concept "high power" relates to a rated power exceeding about 100 MW in a twelve-pulse converter with valves according to the present invention.
The concept "main connection" as used in this application means a connection to a valve which is intended to carry the load current of the valve, this to distinguish from other electrical connections to the valve which may be arranged for, for example, control and measurement purposes.
BACKGROUND OF THE INVENTION
Semiconductor valves of the kind mentioned in the introduction are previously well-known. The semiconductor elements may consist of thyristors or other controllable semiconductor elements, or of diodes. Such valves are used within electric power engineering in power transmission plants. An important field of use is as valves in converters in installations high voltage power transmission. Another field of use of the valves is as control and switching means in equipment for series- or parallel compensation in ac networks.
Installations of the kind referred to here often have very high operating voltages. The valve voltages often lie at one or a few hundred kV, and the operating voltages relative to ground may be in the interval 500-1000 kV. A result of this is that large insulation distances are required, and the valve and the equipment have large dimensions and require large space.
The above-mentioned disadvantages are especially prominent in the case of enclosed, gas-insulated valves designed for outdoor erection. From, for example, the International Patent Applications WO 93/17488 and WO 95/28030, such valves are known. Each valve (possibly half a valve or two series-connected half valves) is arranged in a separate enclosure. The valve is gas-insulated, and the housing in which the valve itself is arranged is filled with a suitable gas, for example air, nitrogen, or SF.sub.6 (sulphur hexafluoride).
Valves of the above-mentioned kind have considerable advantages. The enclosures with the semiconductor valves mounted therein may, in principle, be prepared completely at the factory, and the need of the large valve halls is completely eliminated. However, in case of valves for higher voltages, the completion of the valves at the factory entails relatively large transport dimensions. At the highest currently occurring voltages, the dimensions of the enclosures would be so large that they could not be accommodated within conventional loading-gauges and thus could not be transported at all. The large dimensions of the enclosures would also entail a relatively large need of ground area for erection of the valves, usually 12 or 24 valves, which are included in a single-pole and a two-pole HVDC converter station, respectively.
SUMMARY OF THE INVENTION
The invention aims to provide a semiconductor valve means of the kind described in the introductory part of the description, which has considerably smaller dimensions than prior art semiconductor valves and which thus requires less ground area or hall space for their erection.
The invention preferably aims to provide an enclosed semiconductor valve for outdoor erection, the dimensions of which, also at the highest voltages occurring, will not be so large as to prevent transportation thereof by conventional means of transport.
In a means according to the invention, a plurality of electrostatic shields are arranged one after another along the stack of valves. Each shield is annular
REFERENCES:
patent: 3603721 (1971-09-01), Foti et al.
patent: 3609218 (1971-09-01), Herb et al.
patent: 4107455 (1978-08-01), Richards
patent: 4774385 (1988-09-01), Toshima
patent: 5371651 (1994-12-01), Asplund et al.
Asplund Gunnar
Ekwall Olle
Saksvik Olaf
ABB AB
Leja Ronald W.
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