JPH05145128A - Superconductive current limiting device - Google Patents

Abstract

PURPOSE:To ensure homogeneous superconductivity as well as easy production by constituting a superconductive magnetic shield by laminated hollow/solid plate superconductors or thin film superconductors. CONSTITUTION:A current limiting device 1 houses a vertically laminated-type conductive magnetic shield in a cryostat 2 which is a temperature-transmitting holder having heat insulating structure. Around the cryostat 2, a current limiting coil 4 wound up with copper wire is installed. In addition, an iron core having high permeability is inserted to form a magnetic circuit in the current limiting coil 4. At this time, the shielder 3 is constituted by laminating layers of hollow/ solid plate superconductors or thin-film superconductors. Regarding the cross section of the shielder, optional shapes, for example, round or rectangular, are available. As the performance to shield magnetism does not depend upon the thickness of the shielder, the thickness can be also optional. In this way, the superconductive shield constituting the current limiting holder can be easily produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault current limiter which is introduced into a power system in order to suppress an excessive current generated at the time of an accident such as a ground fault or a short circuit of a transmission line to a predetermined magnitude or less.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, a device utilizing a magnetic saturation characteristic of an iron core is known. However, this device requires a bias coil to saturate the iron core.
Further, there is a problem that a DC power supply device for supplying a large current to them is required.

Therefore, the inventor of the present application previously has a simple structure of the current limiter in which the straight bulk (integral) hollow superconducting magnetic shield 7 is inserted into the air-core portion of the air-core coil 6 as shown in FIG. ,
Alternatively, as shown in FIG. 8, a current limiter in which the iron core 5 is inserted in the hollow portion of the shield 7 has been proposed (Japanese Patent Application No. 229195).

In the device of this structure, the air-core coil 6
Due to the magnetic flux shielding effect of the superconducting magnetic shield 7 inserted in the air core, the magnetic flux in the air-core portion of the air-core coil 6 is eliminated. When the frequency alternating current exceeds a certain threshold, the shielding ability of the superconducting magnetic shield 7 is lost, the alternating magnetic flux generated by the air-core coil enters the air-core portion, and the impedance thereof remarkably increases. That is, it has a function of suppressing an excessive current of the power transmission line.

[0005]

However, in the above apparatus, since the shield 7 is made of a hollow bulk superconductor, the manufacture of the shield 7 becomes extremely difficult as the size of the shield 7 increases. However, there is a drawback that uniform superconducting properties cannot be secured.

Further, since the shield 7 is made of a hollow bulk superconductor, it can only have a straight structure, and therefore the magnetic field generated by the air-core coil 6 wound around the shield 7 is externally exposed. There is also a problem that the current limiting function deteriorates due to leakage.

[0007]

However, according to the research by the inventor of the present application, the magnetic field generated by the air-core coil 6 as described above is substantially parallel to the shield 7, and such a magnetic field is in the direction of the magnetic field. The superconductor having a structure in which plate-shaped superconductors are stacked can be sufficiently shielded.

Therefore, in the present invention, paying attention to the above knowledge, in a superconducting fault current limiter having a structure in which a coil formed by winding a copper wire or a superconducting wire around the superconducting magnetic shield is arranged, A superconducting fault current limiter using a laminated superconducting magnetic shield constituted by stacking hollow or solid plate-shaped or thin-film superconductors is proposed.

The shield used in the present invention is composed of a laminated body of hollow or solid plate-shaped or thin-film superconductors, and its cross section may be circular, rectangular, or any other shape, and shields magnetism. Since the performance does not depend on the thickness, the thickness may be arbitrary.

Furthermore, the stacking interval of the plate-shaped or thin-film superconductors is determined by the length of the shortest cutting line (circular plate-shaped one) which can be drawn through the center of gravity of the plate-shaped or thin-film superconductor. 10 to 20% of the length corresponding to the diameter in the case of a superconductor)
The following is sufficient.

For this reason, it is possible to select a thickness advantageous in terms of manufacturing technology, which makes it extremely easy to manufacture, and it is possible to save the necessary superconducting material as compared with the bulk superconducting magnetic shield.

On the other hand, a thin film superconductor is usually formed on a substrate made of a non-superconducting material, and the magnetic shielding performance depends on the ratio of the thickness of the substrate to the thickness of the superconducting layer. When using a laminated magnetic shield made of a conductive thin film, the ratio must be properly designed. In the shield according to the present invention, the thickness of the superconductor layer is 1 and the thickness of the substrate is arbitrary. 10 to 20% or less of the length of the shortest cutting line (the length corresponding to the diameter in the case of a circular plate-shaped superconductor) that can be drawn through the center of gravity of the thin film superconductor of Is desirable.

Further, in the case of a high-temperature oxide (ceramics) superconductor, a plate-like or thin-film form produced by various methods such as sintering of raw material powder, chemical or physical vapor deposition method, slurry coating method, doctor blade method, etc. The magnetic shield used in the present invention can be easily manufactured by stacking the superconductors described above.

Therefore, in the present invention, a high temperature oxide superconductor, which has a critical temperature of about the liquid nitrogen temperature or more, but is extremely difficult to manufacture a structure having uniform characteristics and large dimensions, can be easily used as a shield. can do.

Further, in the present invention, since the superconducting magnetic shield is formed by laminating plate-shaped or thin-film-shaped superconductors, various structures such as a toroidal shape or a racetrack-shaped structure other than the straight structure. Can be manufactured.

By using a superconducting magnetic shield having a toroidal shape or a racetrack shape, it is possible to obtain a fault current limiter with extremely little external magnetic field leakage.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 shows a current limiting device according to an embodiment of the present invention, in which a current limiting device 1 stores a linear laminated superconducting magnetic shield 3 in a cryostat 2 which is a cryogenic container having a heat insulating structure. A current limiting coil 4 wound with a copper wire is provided around the cryostat 2, and a high-permeability iron core 5 forming a magnetic circuit is further inserted in the current limiting coil 4.

FIG. 2 shows an example of the structure of a current limiting device which is constructed without using the iron core 5 composed of the laminated superconducting magnetic shield 3.

In the current limiting device 1 described above, when the current flowing through the current limiting coil 4 is small, most of the magnetic field generated by the current limiting coil 4 is the shield 3.
Is rejected by. However, when the current increases and most of the generated magnetic field increases to such an extent that it reaches almost the inner wall of the thick portion of the shield 3, the magnetic shielding ability is suddenly lost, and all the magnetic flux that has been repulsed inside the shield 3. Break into. then,
The impedance of the current limiting coil is greatly increased and the current is suppressed.

Particularly, in the fault current limiter 1 of FIG. 1, when all the magnetic flux enters the inside of the shield 3, the current limiting coil 4 and the iron core 5 are magnetically coupled to each other. The impedance is significantly increased, and the effect of suppressing excessive current is increased.

In the above case, when the superconducting wire is used as the coil wire of the current limiting coil 4, both the shield 3 and the current limiting coil 4 must be housed in the cryostat 2. In this case, Requires a power lead for introducing a current from a room temperature portion to a low temperature portion for energizing the current limiting coil 4, and heat loss there becomes a problem.

FIG. 3 shows an example of a laminated superconducting magnetic shield 1 in which hollow superconductor plates having an arbitrary cross section are arranged in a toroidal shape. When using this, a current limiting device is constructed. The iron core 5 is inserted into the hollow portion of the shield 1 to be housed in the low temperature container, and the current limiting coil is wound around the low temperature container.

FIG. 5 shows an example of a laminated superconducting magnetic shield 1 constructed by arranging hollow superconductor plates of arbitrary cross section in a racetrack shape. The structure of the current limiting device is the same as that described above.

By thus forming the magnetic shield in a laminated structure, a straight, toroidal, or racetrack-shaped shield structure can be easily manufactured. Further, by forming the toroidal or racetrack-shaped structure. Since the magnetic field generated by the current limiting coil is linked to almost all the current limiting coils without leaking to the outside, there is a great effect that the current limiting action occurs extremely efficiently.

[0025]

In summary, according to the present invention, the superconducting magnetic shield constituting the current limiting device can be manufactured very easily, and various types such as a straight shape, a toroidal shape and a racetrack shape can be manufactured. A feature is that a shield having a shape can be easily manufactured, and in particular, a superconducting magnetic shield can be easily manufactured from a high temperature oxide superconductor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a current limiting device incorporating a linear laminated superconducting magnetic shield showing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a current limiting device in a case where an iron core incorporating a linear laminated superconducting magnetic shield showing another embodiment of the present invention is not used.

FIG. 3 is a schematic configuration diagram showing an example of a laminated superconducting magnetic shield in which hollow superconductor plates having an arbitrary cross section used in the present invention are arranged in a toroidal shape.

FIG. 4 is a sectional view taken along line AA of the above.

FIG. 5 is a schematic configuration diagram showing an example of a laminated superconducting magnetic shield in which hollow superconductor plates having an arbitrary cross section used in the present invention are arranged in a racetrack shape.

FIG. 6 is a sectional view taken along line BB of the above.

FIG. 7 is a schematic configuration diagram showing an example of a current limiting device incorporating a conventional superconducting magnetic shield.

FIG. 8 is a schematic configuration diagram showing another example of a current limiting device incorporating a conventional superconducting magnetic shield.

[Explanation of symbols]

 1 Current Limiter 2 Cryostat 3 Stacked Superconducting Magnetic Shield 4 Current Limiting Coil 5 Iron Core 6 Air Core Coil 7 Bulk Hollow Superconducting Magnetic Shield

Claims (3)

[Claims] 1. A superconducting fault current limiter having a structure in which a coil formed by winding a copper wire or a superconducting wire around the superconducting magnetic shield is arranged, and the superconducting magnetic shield has a hollow or medium shape of any shape. A superconducting fault current limiter characterized by using a laminated superconducting magnetic shield formed by stacking actual plate-shaped or thin-film superconductors. 2. The superconducting fault current limiter according to claim 1, wherein the superconducting fault current limiter is formed by directly stacking the superconductors to form a laminated superconducting magnetic shield. .. 3. The superconducting fault current limiter according to claim 1, wherein the superconductors are stacked in a racetrack shape or a toroid shape to form a laminated superconducting magnetic shield. Superconducting fault current limiter.