Abb Research Ltd.

Makan Chen

Willi Paul

Martin Lakner

Lise Donzel

Jakob Rhyner

Markus Hoidis

Oystein Fischer

Michel Decroux

Markus Hodis

Louis Antognazza

The present invention relates to a resistive superconducting current limiter with a meandering shape. This current limiter avoids current density peaks at the turning points () or corners of the conductor track () in that the central path of the fault current when limiting occurs is artificially increased by appropriate design of the turning points. For this purpose, conductor material is removed in the region of the inner edge of the turning points (), or the electrical bypass is reinforced at its outer edge ().

Resistive superconducting current limiter

The invention is concerned with a resistive fault current limiter (FCL) based on thin superconducting films. The FCL comprises constrictions ( ) with a reduced critical current, separated by connecting paths ( ). Upon occurrence of a fault current, the former turn resistive simultaneously and build up a resistance which allows the applied voltage to drop entirely only over the constrictions. Only at a later stage, the connecting paths become resistive and dissipate energy. The thickness and width of an electrical bypass determine said normal resistivities of the constrictions and the connecting paths.

Superconducting fault current limiter

In a superconducting current limiter , in the limiting state pressure waves which may damage the superconductor are produced as a result of the evaporation of cooling liquid. According to the invention, the current limiter is not immersed in a cooling liquid, but rather is brought into thermal contact with a cooling fluid which does not undergo a phase transition at over the operating temperature and therefore does not evaporate in the limiting state. A refrigeration reservoir , which may be the condensed phase of a gaseous cooling fluid or a cryogenic cooler, determines the operating temperature of the current limiter. One advantage is that it is now possible for a plurality of plate-like current-limiter modules &prime; of unlimited size to be arranged next to one another in the cooling fluid

Device used in superconductor technology

An electrically stabilized thin-film high-temperature superconductor includes a superconductive layer ( ) applied over a flat metallic substrate ( ) and connected to the metallic substrate ( ) so that electrical contact between the superconductive layer ( ) and the metallic substrate ( ) is distributed over the area of the metallic substrate ( ).

Electrically stabilized thin-film high-temperature superconductor and method for the production thereof

On transition from the superconducting state to the normal conducting state, current limiters having a high-temperature superconductor increase their electrical resistance and thereby limit an electric current which is flowing through them. To provide electrical stabilization, the high-temperature superconductor is combined with a silver foil having a layer thickness of <50 &mgr;m to form an extensive composite conductor with good conductivity. The ratio of the layer thickness of the high-temperature superconductor to that of the silver foil should be >10. To produce this composite conductor, the silver sheet is placed on one side on a 2 mm thick MgO powder layer and, on the other side, is covered with a 600 &mgr;m thick so-called green sheet which contains a high-temperature superconductor powder and an organic binder. In order to stabilize the high-temperature superconductor mechanically after it has been fused together, a 200 &mgr;m thick layer consisting of glass or carbon fibers and epoxy resin is applied by vacuum impregnation to at least one side of the composite conductor. In order to produce resistive current limiters, current limiter elements in sheet form, having the specified layer structure, are cut to form meanders and are bonded or pressed onto one another in at least two layers, if appropriate with the interposition of cooling elements. Inductive current limiters are obtained by bending flexible sheets of this type to form tubes and soldering a metal strip of silver over a gap in the ring.

Current limiter having a high-temperature superconductor

The present invention relates to a high-temperature superconductor arrangement which is protected against hot spots. A contact-making layer is provided between a superconductor layer and an electrical bypass which contact-making layer has anisotropic electrical conductivity. This ensures a low contact resistance between the superconductor and the bypass without the admittance being increased in the main current flow direction The said anisotropy is produced by discontinuities in the contact-making layer for example by said contact-making layer being broken down into areas which are not connected to one another.

High-temperature superconductor arrangement and a method for its production

Ceramic high-temperature superconductors ( ) which are intended to be used as current limiters in alternating-current lines should have a bypass layer ( ) whose electrical resistivity is increased by more than 10 times with respect to that of a pure noble-metal bypass layer. In order to achieve this, the noble-metal bypass layer ( ) of the high-temperature superconductor ( ), preferably of silver, is alloyed with a base metal, preferably Pb or Bi or Ga, by a thermal treatment. The ratio of the bypass layer thickness (d ) of the noble-metal bypass layer ( ) to the superconductor layer thickness (d ) is adjusted to <1/5. A base-metal bypass layer ( ) of steel whose electrical resistivity is in the range between 10 &mgr;&OHgr;&times;cm and 100 &mgr;&OHgr;&times;cm at 77 K is soldered on or applied under isostatic pressure over the noble-metal-containing bypass layer ( ). The noble-metal bypass layer thickness d and the base-metal bypass layer thickness d are to be chosen so that the ratio &rgr;2/d is >0.5&times;&rgr;3/d , where &rgr;2 and &rgr;3 are the electrical resistivity of the noble-metal-containing bypass layer ( ) and the base-metal bypass layer ( &prime;), respectively.

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Baden-Dättwil, Switzerland

Makan Chen