EP1301933A1

EP1301933A1 - Superconducting device with inductive current limiter using a high-tc superconducting material

Info

Publication number: EP1301933A1
Application number: EP01953888A
Authority: EP
Inventors: Heinz-Werner NEUMÜLLER; Günter RIES
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2000-07-21
Filing date: 2001-07-09
Publication date: 2003-04-16
Also published as: US20030191028A1; JP2004505440A; WO2002009129A1; DE10035634A1; US6795282B2; JP3699448B2

Abstract

The invention relates to a superconducting device (22) that comprises an inductive current limiter (28a, 29b) with an annular element (27a, 27b) produced from high-Tc superconducting material. The device is further provided with a soft-magnetic yoke leg (26c, 26d) enclosed by said material and with a transformer (23) with primary and secondary windings (24, 25) and a soft-magnetic flux element (26) with a plurality of yoke legs (26a-26e). The magnetic flux element (26) is designed to contain between the primary winding (24) and the secondary winding (25) of the transformer (23) the yoke leg (26c, 26d) of the current limiter (28), the conductor of one winding (24) producing a switch current for the current limiter (28).

Description

description

Superconducting device with inductive current limiter unit using high-T _c superconducting material

The invention relates to a superconducting device with at least one inductive current limiter unit, which has at least one conductor track carrying a magnetic switching current in the case of limitation, at least one ring body made of high-T _c superconductor material inductively assigned to the conductor track, and a core leg made of soft magnetic material enclosed by the ring body contains. A corresponding superconductivity device can be found in EP 0 353 449 AI. A transformer can be assigned to your at least one current limiter unit, which transformer has a primary and a secondary coil winding and an associated magnetic flux body made of soft magnetic material with several yoke legs.

Short circuits and electrical arcing cannot be avoided with certainty in electrical AC supply networks. The alternating current in the circuit concerned rises very quickly, ie within the first half-wave, to a multiple of its nominal value until it is interrupted by suitable fuse and / or switching means. As a result, considerable thermal and mechanical loads from current forces occur in all affected network components such as lines, busbars, switches and transformers. Since these short-term loads increase with the square of the current, a safe limitation of the short-circuit current to a lower peak value can significantly reduce the requirements for the load capacity of the network components mentioned. This enables cost advantages to be achieved, for example when building new networks or when expanding existing networks, by replacing network components with embodiments that can withstand higher loads by installing current limiter units. With superconducting current limiter units, the current rise after a short circuit can be limited to a value of a few multiples of the nominal current in a manner known per se. In addition, such a limiter unit is ready for operation again a short time after the shutdown process. So it acts like a quick, self-healing backup. It ensures a high level of operational safety because it acts passively, ie it works autonomously without short-circuit detection and without an active triggering by a switching signal.

Superconducting current limiter units usually form a switching element to be inserted serially into a circuit. Corresponding current limiter units can be of the so-called resistive or inductive type. Inductive current limiter units are often designed as choke coils (see e.g. DE 38 29 207 AI or EP 0 440 664 Bl). In this type, a shielding current is induced by a conductor track of a choke coil winding carrying a nominal current during operation in an associated (secondary) superconducting winding which is short-circuited. This superconducting winding can also be formed by a superconducting core or the part of such a core in the interior of the choke coil. In the event of a short circuit, the shielding current induced by a corresponding switching current in the superconducting winding or the core becomes so great that the critical (shielding) current of the superconducting material is exceeded. As a result, the load-bearing capacity of this winding or the core collapses due to the superconducting material becoming normally conductive, as a result of which the inductance of the inductor increases abruptly and the AC resistance in the conductor track of the inductor is accordingly increased to a value causing the current limitation.

A corresponding inductive current limiter unit emerges from the EP-A document mentioned at the beginning. It contains an induction coil through which the nominal current flows, the one Encloses ring body made of high-T _c superconductor material. This ring body has a centrally symmetrical, hollow interior, in which a core leg made of soft magnetic material of high permeability is arranged concentrically. This core leg can also be part of a complete, self-contained magnetic circuit.

Known current limiter units of this type with metal oxide high-T _c materials (so-called “HTS” materials) whose transition temperature T _{c is} so high that they can be kept in the superconducting operating state with liquid nitrogen (LN ₂ ) of at most 77 K, show a rapid increase in the electrical resistance when their critical values are exceeded. The associated heating to the normal conducting state and thus the indirect triggering of the current limitation take place in a sufficiently short time so that the peak value of a short-circuit current to a fraction of the unlimited current, The superconducting parts should be in good heat-conducting contact with a suitable refrigerant, which they can return to the superconducting operating state in a relatively short time after the critical values have been exceeded can.

If the current in the circuit of one of the coil windings of a transformer, the at least one conductor of which surrounds a yoke leg of a magnetic flux body made of soft magnetic material, is now to be limited with a corresponding current limiter unit, this is done according to the prior art by connecting corresponding separate components in the circuit in series , The related design effort is correspondingly high.

It is therefore an object of the present invention to provide a superconducting device with the features mentioned at the beginning, the design complexity of which is reduced. This object is achieved with the measures specified in claim 1. The superconducting device according to the invention consequently has at least one inductive current limiter unit, which has at least one conductor path carrying a switching current in the event of a limitation, at least one ring body made of high-T _c superconductor material inductively assigned to the conductor path and a core leg made of soft magnetic material enclosed by the ring body Contains material. Furthermore, the device has a transformer which contains a primary and a secondary coil winding and an associated magnetic flux body made of soft magnetic material with several yoke legs. The magnetic flux body between the primary coil winding and the secondary coil winding should be provided with at least one further yoke leg, which is provided as the core leg of the current limiter unit, and the at least one conductor track of the current limiter unit should be formed with the at least one conductor of one of the coil windings.

In this context, an annular body is understood to mean any structure made up of at least one element or component or conductor which contains at least high-T _c superconductor material and forms a short-circuit ring which forms the associated yoke leg which acts as a magnetic bypass element of the magnetic flux body.

The advantages associated with the configuration of the superconducting device according to the invention are to be seen in particular in that the magnetic yoke of the inductive current limiter unit is integrated as a further yoke leg in the magnetic flux body which is to be provided anyway for the transformer coil windings. This reduces the amount of soft magnetic material accordingly. In addition, no separate conductor path generating a switching current is required for the current limiter unit, since the

Switching current is now generated by the at least one conductor of one of the coil windings itself; ie, the switching trigger send function regarding of the high-T _c superconductor material of the ring body is caused solely by the conductor of this coil winding.

Advantageous embodiments of the superconducting device according to the invention emerge from the dependent claims.

The conductors of the transformer coil windings can also particularly advantageously contain high-T _c superconductor material. In this case, in particular the coil windings and the current limiter unit can be arranged in a common cryostat vessel which contains two refrigerant spaces in which the winding or the current limiter unit are accommodated. This has the advantage that the

Refrigerant rooms can set different temperature levels.

It is particularly advantageous if the refrigerant in the refrigerant chamber of the transformer coil windings is at a lower temperature level than the refrigerant in the refrigerant chamber of the limiter unit. Preferably, the coolant area of these coil windings and the refrigerant space should here are the limiter unit at least approximately at the same pressure (with the inclusion of variations of the pressure in the coolant space of the limiter unit of the pressure in the refrigerant space of the windings by a maximum of ± 10% ^'). In this way, the heat loss generated in the windings as a result of alternating current losses of the superconductor can be dissipated by convection without undesired gas formation due to appropriate evaporation. In this way, a reduction in the dielectric strength caused by gas bubbles, which is particularly required when operating at high voltage, can be avoided. Advantageously, the superconducting device according to the invention can also comprise a current limiter unit which has a plurality of yoke legs of a magnetic flux body enclosed by superconducting ring bodies. This opens up a correspondingly large degree of design freedom with regard to the cross section of the soft magnetic material.

Further advantageous embodiments of the superconducting device according to the invention can be found in the remaining claims and the drawing.

For a supplementary explanation of the invention, reference is made below to the drawing, in which preferred embodiments of superconducting devices according to the invention are illustrated. Each shows a schematic representation of their

1 essential parts of a superconducting device with a transformer and a superconducting current limiter unit in a longitudinal section, FIG. 2 parts of another superconducting device with a transformer and another current limiting device in a cross section, FIG. 3 parts of another superconducting device with a warm transformer and a superconducting current limiter unit in one Longitudinal section and their figures 4 and 5 two design options of the superconducting ring body of a current limiter unit suitable for a superconducting device in cross-sectional or oblique view.

In the figures, corresponding parts are each provided with the same reference symbols.

The magnetic coil windings of the superconducting device according to the invention are the primary and secondary windings of a transformer using preferably superconducting conductors (cf. for example WO 00/16350 A). However, the conductors of the transformer coil windings, which may be subdivided into a plurality of partial windings, need not necessarily have superconducting, in particular high-T _c, superconducting material. Normally conductive material is also suitable as conductor material. At least one inductive current limiter unit should be assigned to the circuit of at least one of the transformer coil windings, preferably the primary winding. Of course, several current limiter units can also be provided. Current limiter units suitable for the superconducting device according to the invention are based on known embodiments and their mode of operation (cf., for example, DE 39 19 465 AI or EP 0 353 449 AI).

In particular, oxidic HTS cuprate material such as YBa ₂ Cu ₃ O _x or Bi ₂ Sr ₂ CaCu ₂ O _y or (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _z comes in as the conductor material for the superconducting parts of the current limiter unit and optionally the coil winding Question. For example, (Bi, Pb) ₂ Sr ₂ CaCu ₃ O _z material can be selected for the conductor of a possible HTS coil winding. The specific choice of material depends on the manufacturing processes of the individual parts or is selected depending on the respective operating temperature.

1 shows a first embodiment of a superconducting device according to the invention. This device, generally designated 2, contains, for example, a superconducting, in particular an HTS transformer 3 with a primary and a secondary (transformer) coil winding 4 and 5, respectively. These coil windings each enclose a first and second yoke leg 6a and 6b of a three-legged one Magnetic flux body 6 (or magnetic core) made of soft magnetic material, as is known for example from transformer construction. According to the invention, the magnetic flux body between the primary coil winding and the secondary coil winding should be provided with at least one further yoke leg, which acts as a current limiter unit. hearing yoke leg can be seen. Accordingly, in the embodiment shown, the magnetic flux body 6 has a central or central yoke leg 6c between its two outer yoke legs 6a and 6b as the third (further) yoke leg. This yoke leg βc is enclosed in a known manner by an annular body 7 made of HTS material in the form of a corresponding hollow cylinder. Together with the ring body 7, it forms the essential part of a current limiter unit 8. In contrast to the inductive current limiter unit that can be gathered from the aforementioned EP 0 353 449 AI, this current limiter unit does not have its own conductor track, which in the event of limitation is a switching current, in particular a short-circuit current. Rather, this conductor track is formed by the primary winding 4 of the transformer 3. This winding, constructed with at least one conductor designed for a nominal current, generates an alternating magnetic flux in the magnetic flux body 6 in the magnetic flux body 6 in a closed magnetic flux circuit in which the two yoke legs 6a and 6b assigned to the primary winding 4 and the secondary winding 5 are located. In the figure, this magnetic flux present during operation between the primary and secondary windings via the yoke legs 6a and 6b is indicated by a dashed, arrowed line 10. A ring current or shielding current is induced in the superconducting ring body 7, which prevents magnetic flux from flowing through the yoke leg 6c enclosed by it.

In a limitation case (short circuit case or switching case), the current induced in the ring body exceeds the critical value of the HTS material, so that it becomes normally conductive (so-called “quench”). The consequence of this is that magnetic flux now passes through the yoke leg 6c The magnetic flux caused by the primary winding 4 and passing through the assigned yoke leg 6a can now close via the yoke leg 6c before it reaches the area of the yoke leg assigned to the secondary winding 5 6b reached. This leg 6c thus forms a magnetic bypass for the magnetic flux generated by the primary winding 4 with respect to the secondary winding 5. The magnetic flux of this bypass is indicated in the figure by a dotted, arrowed line 11. With the magnetic bypass activated, there is practically no net flow through the secondary winding; ie the secondary voltage has then decreased to a minimal residual value. The current limiter unit 8 is therefore in limiter mode.

Of course, the superconducting device according to the invention is not limited to a soft magnetic flux body or yoke core, which has only a single additional yoke leg as a magnetic bypass element with an HTS ring body. An embodiment with two such

FIG. 2 shows the bypass duck. The superconducting device, generally designated 12, accordingly contains a magnetic flux body 16 with two additional yoke legs 16c and 16d serving as magnetic bypass elements, each of which consists of a hollow cylindrical ring body 17a or 17b

HTS material are enclosed. In the embodiment of the magnetic flux body 16 shown, the primary winding 14 of a transformer is arranged around a central yoke leg 16b. The secondary winding 15 of this transformer then not only encloses the primary winding 14, but also the two yoke legs 16c and 16d arranged laterally therefrom with their HTS ring bodies 17a and 17b. In the figure, the two outer side parts 16a and 16e of the magnetic flux body 16 can also be seen.

For the embodiment of a transformer shown in FIG. 2 with a surrounding primary and secondary winding, instead of the two bypass elements 16c and 16d shown, it is of course also possible to use only one such element or even a larger number of such elements in that between the middle yoke leg 16b and the formed the two outer yoke legs 16a and 16e 20 may be arranged. The sum of the cross sections of soft magnetic material must be able to carry the entire primary flux, i.e. roughly the same size as the transformer core itself.

The primary and / or secondary winding of a transformer are advantageously made of superconducting conductors, in particular HTS conductors. If HTS material is used for the conductors, the material of the HTS ring body 7, 17a, 17b need not necessarily be identical to that for the conductors of the at least one winding. All superconducting parts are expediently accommodated in a common cryostat vessel, discrete refrigerant spaces being optionally provided for the at least one ring body and the at least one coil winding. This has the advantage that different temperature levels can be set in the refrigerant rooms, but in particular at the same pressure. It can be expedient if the refrigerant spaces are in a refrigerant connection with one another. This is because it is advantageously possible to exchange the refrigerant between the two refrigerant spaces which may be at di ferent temperature levels.

In addition to using superconducting, in particular HTS, material for the at least one coil winding of a superconducting device according to the invention, normally conducting, cooled or non-cooled conductor material can also be provided for the winding. FIG. 3 shows a corresponding exemplary embodiment of a superconducting device 22 with a transformer 23 which contains a primary winding 24 and a secondary winding 25 made of normally conductive, non-cooled conductors. A magnetic flux body 26 used has a central yoke leg 26b and two outer yoke legs 26a and 26e. In each of the spaces 28a and 29b between the middle yoke leg 26b and the two outer yoke legs 26a and 26e there is another yoke leg 26c and 26d as a magnetic bypass element. This Elements are each enclosed by a hollow cylindrical HTS ring body 27a or 27b and form current limiter units 28a or 28b. The HTS ring bodies, together with their associated yoke legs 26c and 26d, are each located in their own cryostat 30a or 30b. This makes it necessary for there to be a small gap sl or s2 between the end faces of the yoke bodies 26c and 26d located in the cryostats 30a and 30b and the respectively adjacent, non-cooled parts of the magnetic flux body 26. However, this gap does not impair the magnetic bypass function of the yoke legs 26c or 26d. The cryostat walls must therefore consist of a non-magnetic, electrically poorly conductive material such as stainless steel, so that no winding voltages can be induced in them during normal operation.

A cross section through the shown structure of the superconducting device 22 according to FIG. 3 has an appearance corresponding to that of FIG. 2. The magnetic flux lines 10 and 11 are also illustrated in FIG.

Further design options for a limiter unit of a superconducting device according to the invention are:

• Use of an HTS ring body in the form of a hollow cylinder made of HTS solid material or a carrier tube made of non-magnetic material such as ceramic, glass or metal, which is coated with the HTS material as a thin or thick film.

• Use of an HTS ring body in the form of a short-circuit winding, for example made of (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _z -HTS-

Conductor material in an Ag alloy matrix with a high specific resistance of in particular p> 2 μΩcm. A corresponding exemplary embodiment is indicated in FIG. 4 in a perspective view. A hollow cylindrical yoke leg 36i serving as a magnetic bypass element made of soft magnetic material is provided with two superconducting windings 37a and 37b of identical winding number wrapped on the inside and outside. These windings form an HTS ring body 27 in that they are connected to one another in such a way that a current flows through them in the opposite direction. In this embodiment, the primary winding with a yoke leg of a magnetic flux body is located within the magnetic bypass element or yoke leg 36i, while a secondary winding is arranged around this leg. The main flow of the transformer does not induce current; only a leakage flux is shielded. In the event of a short circuit, the superconducting material changes to the normal conducting state, the magnetic flux closing via the yoke leg 36 as a magnetic bypass. The result is a structure of a superconducting device similar to that according to FIGS. 2 and 3.

• Use of an HTS ring body in the form of a short-circuit winding made of an HTS strip conductor, which forms a film made of HTS material such as YBa ₂ on a strip-shaped carrier material such as stainless steel or a Ni alloy (eg made of "Hastelloy") Cu ₃ O _x The short-circuit winding can be designed, for example, in accordance with FIG.

• Use of a HTS ring body, which is composed of individual HTS elements. A corresponding exemplary embodiment is shown in cross section in FIG. The HTS ring body, designated 47, encloses a yoke body 46i serving as a magnetic bypass element. It is composed of individual plate elements 47i, which are connected to one another at their edges in an electrically conductive manner via electrical connecting elements 48i to form a short-circuit ring. The plate elements 47i have, for example, a corresponding carrier element 49 made of an insulating material such as a ceramic or glass, on which an HTS layer 50, for example made of YBa ₂ Cu ₃ O _x, which is represented by a reinforced line, is applied. In the figure, four such HTS plate elements 47i are interconnected to form the short-circuit ring; Of course a different number of corresponding elements can also be provided.

Claims

claims

1. Superconducting device

- With at least one inductive current limiter unit, which a) contains at least one conductor track which carries a switching current in the event of a limitation, b) at least one ring body made of high-T _c superconductor material c) which is inductively assigned to the conductor track and a core limb made of soft magnetic material and surrounded by the ring body,

- With a transformer that has a) a primary and a secondary coil winding and b) an associated magnetic flux body made of soft magnetic material with several yoke legs, characterized in that • the magnetic flux body (6; 16; 26) between the primary coil winding (4 ,; 14 ; 24) and the secondary coil winding (5; 15; 25) of the transformer (3) is provided with at least one further yoke leg (6c; 16c, 16d; 26c, 26d; 36i; 46i), which acts as the core leg of the current limiting unit (8) is provided

And that the at least one conductor track of the current limiter unit is formed with the at least one conductor of one of the coil windings.

2. Device according to claim 1, so that the conductors of the coil windings (24, 25) consist of normally conductive material.

3. Device according to claim 1, dadurchge - indicates that the conductors of the coil windings (4, 5; 14, 15) contain high-T _c superconductor material.

4. Device according to claim 3, so that the coil windings (4, 5; 14, 15) and the current limiter unit (8) are arranged in a common cryos data vessel.

5. Device according to claim 4, so that the cryostat vessel contains two refrigerant spaces in which the coil windings (4, 5; 14, 15) or the current limiter unit (8) are accommodated.

6. Device according to claim 5, so that the refrigerant spaces are in a refrigerant connection with one another.

7. Device according to claim 5 or 6, so that the refrigerant in the refrigerant space of the coil windings (4, 5; 14, 15) is at a lower temperature level than the refrigerant in the refrigerant space of the current limiter unit (8).

8. Device according to one of claims 5 to 7, so that the refrigerant chamber of the coil windings (4, 5; 14, 15) and the refrigerant chamber of the current limiter unit (8) are at least approximately at the same pressure.

9. Device according to one of the preceding claims, so that the at least one superconducting ring body (27a, 27b) with its associated yoke leg (26c, 26d) is arranged in its own cryostat (30a, 30b).

10. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the

Current limiter unit several of superconducting ring bodies (17a, 17b; 27a, 27b) has enclosed yoke legs (16c, 16d; 26c, 26d) of a magnetic flux body (16; 26).

11. Device according to one of the preceding claims, characterized in that the at least one superconducting ring body (7; 17a, 17b; 27a, 27b) consists of high-T _c superconductor solid material.

12. Device according to one of claims 1 to 10, - characterized in that the at least one superconducting ring body (7; 17a, 17b; 27a, 27b) consists of a carrier tube which is coated with the high-T _c - superconductor material.

13. Device according to one of claims 1 to 10, characterized in that the at least one superconducting ring body (37) is formed by a short-circuit winding of at least one high-T _c superconductor.

14. Device according to claim 13, characterized in that the conductor of the short-circuit winding contains high-T _c superconductor material embedded in an alloy matrix or applied to a band-shaped carrier.

15. The device according to claim 13 or 14, so that the short-circuit winding is formed from two concentric, bifilar connected partial windings (37a, 37b) which are arranged on the inside or outside of a hollow cylindrical yoke leg (36i) of a magnetic flux body.

16. Device ^" according to one of claims 1 to 10, - characterized in that the at least one superconducting ring body (47) by a short final winding is made up of plate elements (47i) coated with high-T _c superconductor material.