Superconducting device with inductive current limiter using a high-tc superconducting material

#The invention relates to a superconducting device having at least one inductive current limiter unit, which contains at least one conductor track which carries a switching current in a limiting situation, at least one annular body which is inductively associated with the conductor track and is composed of high-Tc superconductor material, and a core limb which is surrounded by the annular body and is composed of soft-magnetic material. A corresponding superconducting device is disclosed in EP 0 353 449 A1. Its at least one current limiter unit may have an associated transformer, which has a primary and a secondary coil winding as well as an associated magnetic flux body composed of soft-magnetic material and having a number of yoke limbs.

#Short circuits and electrical flashovers cannot be reliably avoided in electrical AC supply networks. In the process, the alternating current in the circuit that is affected arises very quickly, that is to say within the first half-cycle, to a multiple of its rated value, until it is interrupted by suitable protection and/or switching means. As a consequence of this, considerable thermal and mechanical stresses occur as a result of current forces in all the affected network components, such as cables, busbars, switches and transformers. Since these short-term loads increase with the square of the current, safe limiting of the short-circuit current to a lower peak value can considerably reduce the requirements for the load capacity of said network components. This results in cost advantages, for example for the construction of new networks and when upgrading existing networks, in that the installation of current limiter units makes it possible to avoid the need to replace network components by embodiments having a higher load capacity.

#The use of superconducting current limiter units makes it possible, in a manner known per se, to limit the current rise after a short circuit to a value equivalent to a few multiples of the rated current. Furthermore, a limiter unit such as this is ready for operation once again a short time after the disconnection process. It thus acts as a rapid, self-healing protection device. In the process, it ensures high operational reliability since it acts passively, that is to say autonomously without previous detection of short circuits and without active tripping by means of a switching signal.

#In order to supplement the explanation of the invention, the following text refers to the drawing, which illustrates preferred embodiments of the superconducting devices according to the invention. In this case, in each case illustrated schematically:

#FIG. 1 shows the major parts of a superconducting device with a transformer and a superconducting current limiter unit in the form of a longitudinal section,

#FIG. 2 shows parts of a further superconducting device with a transformer and a different current limiter unit, in the form of a cross section,

#Corresponding parts are in each case provided with the same reference symbols in the figures.

#The magnetic coil windings of the superconducting device according to the invention comprise the primary winding and the secondary winding of a transformer using preferably superconducting conductors (see, for example, WO 00/16350 A) The conductors of the transformer coil windings, which if necessary are subdivided into a number of winding elements, do not, however, necessarily need to be composed of superconducting material, in particular high-Tc superconducting material. Normally conductive material is also suitable as the conductor material. The circuit comprising at least one of the transformer coil windings, preferably the primary winding, is intended to have at least one associated inductive current limiter unit. A number of current limiter units may, of course, also be provided. Current limiter units which are suitable for the superconducting device according to the invention are based on known embodiments and their method of operation (see, for example, DE 39 19 465 A1 or EP 0 353 449 A1).

#Oxidic HTS cuprat materials such as YBa2Cu3Ox, Bi2Sr2CaCu2Oy or (Bi, Pb)2Sr2Ca2Cu3Oz may be used, in particular, as the conductor material for the superconducting parts of the current limiter unit and, if required, of the coil winding. By way of example, (Bi, Pb)2Sr2Ca2Cu3Oz material may be chosen for the conductor of any HTS coil winding. The specific choice of the material in this case depends on the production processes for the individual parts, and is chosen as a function of the respective operating temperature.