JP4671111B2 - Superconducting cable - Google Patents

Description

  The present invention relates to a superconducting cable. In particular, the present invention relates to a superconducting cable that can suppress the ballooning of the superconducting wire accompanying the vaporization of the refrigerant and that can reduce the cable size.

  As a superconducting cable, a superconducting cable shown in FIG. 2 has been proposed. This superconducting cable 100 has a configuration in which a three-core cable core 10 is housed in a heat insulating tube 20 (for example, Patent Document 1).

  Each cable core 10 includes a former 11, a superconducting conductor layer 12, an insulating layer 13, a superconducting shield layer 14, and a protective layer 16 in order from the center. For example, the former 11 is composed of a stranded wire obtained by twisting strands made of a normal conducting material such as Cu. The conductor layer 12 is configured by spirally winding a superconducting wire on the former 11 in multiple layers. Typically, a superconducting wire is used in the form of a tape in which a plurality of filaments made of an oxide superconducting material are arranged in a stabilizing material such as a silver sheath. Such a superconducting wire is usually manufactured by a powder in tube method, and a superconducting filament which is an oxide is obtained by sintering at atmospheric pressure. The insulating layer 13 is configured by winding insulating paper. The shield layer 14 is formed by spirally winding a superconducting wire similar to the conductor layer 12 on the insulating layer 13. Insulating paper or the like is used for the protective layer 16.

  The heat insulating tube 20 has a structure in which a heat insulating material (not shown) is disposed between the double tubes composed of the inner tube 21 and the outer tube 22, and the inside of the double tube is evacuated. An anticorrosion layer 23 is formed outside the heat insulating tube 20. Then, the space formed between the inner pipe 21 and the core 10 is filled and circulated with a refrigerant such as liquid nitrogen, and the insulating layer 13 is impregnated with the refrigerant to be used.

  On the other hand, in the case of superconducting cables such as those mentioned above, in order to prevent accidental current from flowing into the superconducting wire in the event of a short-circuit accident or ground fault, It is necessary to secure the road. Therefore, it has been proposed to combine a normal conducting material with the constituent material of the superconducting cable. For example, Patent Document 2 discloses that a normal conductive metal layer serving as a shunt path for an accident current is formed outside a conductor made of a superconducting wire. Further, Patent Document 3 discloses that a twisted wire structure of an insulation-coated wire made of a normal conducting material is used as a constituent material of a core material (former), and an accident current is divided.

Japanese Patent Laid-Open No. 2001-202837 (FIG. 1) JP 2000-67663 A JP 2001-325838

  However, the conventional superconducting cable has a problem that it is difficult to achieve both the prevention of ballooning of the superconducting wire accompanying the vaporization of the refrigerant and the reduction of the cable size.

  As described above, since the filament of the superconducting wire is obtained by sintering at atmospheric pressure, the density is not 100%, and the filament has a certain amount of voids. When the superconducting wire is immersed in a refrigerant such as liquid nitrogen during the cable operation, the refrigerant enters the gap of the filament from a pinhole or the like of a silver sheath that serves as a stabilizer. In this state, when a temperature rise exceeding the boiling point of the refrigerant occurs, the refrigerant that has entered the gap is vaporized, resulting in ballooning in which the wire is expanded. The occurrence of ballooning causes a decrease in the critical current of the superconducting wire due to filament cracks and the like.

  Such a sudden rise in the cable temperature accompanying the vaporization of the refrigerant occurs, for example, when an accident current flows through the superconducting wire or when the temperature of the superconducting cable is raised during cable maintenance.

  In general, fault currents such as short-circuit accidents and ground faults are large currents that are several tens of times the rated current, so when such large currents flow through a superconducting wire, the superconductors cause a transition to normal conductors. Fever. When this heat generation is large and accompanied by a temperature rise exceeding the boiling point of the refrigerant, ballooning occurs.

  As a measure to suppress damage to the superconducting wire due to this accident current, the core material (former) can be used as a shunt path for the fault current as described above, or a normal conducting layer can be formed outside the superconducting wire conductor as a shunt path for the fault current. It has been proposed to do. However, if an attempt is made to suppress the temperature rise when the accident current flows to below the boiling point of the refrigerant, it is necessary to increase the cross-sectional area of the former and the normal conducting layer that serve as a flow path for the accident current. As a result, the cross-sectional area of the cable is increased, and the compactness that is a merit unique to the superconducting cable is hindered. In particular, if the diameter of the cable increases, the superconducting cable may not enter the specified laying pipeline.

  On the other hand, when the temperature of the cable is raised during cable maintenance, if the rate of temperature rise is high, the refrigerant that has entered the gaps in the filaments may vaporize before passing through the pinholes of the silver sheath, and ballooning may still occur. At this time, it can be considered that ballooning can be suppressed by slowing the temperature rising rate of the cable. In this case, however, it takes a long time to raise the temperature of the cable, and it is impossible to perform an immediate maintenance operation.

  The present invention has been made in view of the above circumstances, and a main object thereof is to provide a superconducting cable capable of achieving both prevention of ballooning of a superconducting wire and reduction in cable size.

  The present invention achieves the above object by using a superconducting wire that is substantially free of voids in a superconducting filament, in addition to combining a normal conducting material that becomes a shunt path for an accident current with a superconducting cable.

  The superconducting cable of the present invention includes a core made of a normal conducting material, a superconducting inner conductor provided outside the core, an insulating layer provided outside the inner conductor, and a superconducting outer conductor provided outside the insulating layer. And a normal conducting layer to which an accident current flowing in the outer conductor is shunted. Here, for at least the outer conductor, a superconducting wire in which a superconducting filament is arranged in a stabilizing material is used, and the superconducting filament has a density substantially free of voids. The cross-sectional area of the normal conducting layer is that the outer conductor temperature when the fault current flows to the outer conductor is equal to or higher than the boiling point of the refrigerant at the refrigerant pressure during operation of the superconducting cable, and the temperature rise of the outer conductor at that time is Select to be 100K or less.

  If a superconducting wire having a density with substantially no voids in the superconducting filament is used, ballooning caused by vaporization of the refrigerant entering the voids in the filament can be prevented. Therefore, there is no problem that the critical current is lowered due to ballooning even if the accident current flows through the superconducting wire or the temperature rises during maintenance even if the wire temperature exceeds the boiling point of the refrigerant at the refrigerant pressure during cable operation.

  Thus, by using a superconducting wire that does not substantially cause ballooning, the superconducting wire is allowed to be heated to a temperature equal to or higher than the boiling point of the refrigerant at the refrigerant pressure during cable operation. Conventionally, in order to prevent ballooning, the core material or normal conducting layer has a sufficient cross-sectional area to shunt the fault current and reduce the fault current flowing in the superconducting wire. The cable is designed not to rise. In the present invention, since the temperature of the superconducting wire is allowed to rise above the boiling point of the refrigerant, the cross-sectional area of the normal conducting layer can be reduced as compared with the conventional case, and the superconducting cable can be made compact. Here, examples of the refrigerant for the cable include liquid helium, liquid hydrogen, liquid nitrogen, and liquid oxygen. For example, in the case of liquid nitrogen, the refrigerant pressure during operation is about 2 atm to 6 atm, and the boiling point of the refrigerant at that time is about 84K to 97K.

  On the other hand, even if the boiling point of the refrigerant at the refrigerant pressure at the time of cable operation exceeds the critical current due to ballooning, considering the actual operation of the superconducting cable, the temperature rise of the superconducting cable due to energization of the accident current If the value is large, problems such as a long time required for returning to the original low temperature state and starting the operation again occur. Therefore, it is preferable that the temperature increase range is small. Further, for example, when a Bi-based superconducting wire is cooled from room temperature to liquid nitrogen temperature, thermal contraction of about 0.3% occurs. On the other hand, when an accident current flows through the superconducting wire and a temperature rise occurs, the superconducting wire expands thermally. If the temperature rise of the wire due to the accident current is large, the wire will instantaneously thermally expand and extend in the longitudinal direction, but if the amount of thermal expansion is large, the expansion will be concentrated at the cable end, causing buckling of the superconducting wire, etc. It is possible that this problem will occur. In order to suppress such a problem, it is preferable to suppress this thermal expansion coefficient to about 0.15% which is half of the thermal contraction ratio during cooling. Therefore, the cross-sectional area of the normal conducting layer is selected so that the temperature rise of the superconducting wire can be reduced to 100K or less so that the thermal expansion coefficient can be suppressed to about 0.15%.

  The superconducting wire having the high-density filament is used for at least the outer conductor. In general, since the fault current flowing through the inner conductor can be shunted to the core member normally provided as a cable component, the inner conductor is easy to take measures against the temperature rise. On the other hand, since it is necessary to add a normal conducting layer as a countermeasure against the temperature rise, the outer conductor has a problem that the outer diameter of the core is increased by increasing the cross-sectional area of the normal conducting layer. For this reason, a superconducting wire having a high-density filament on the outer conductor that is difficult to take measures against temperature rise is used.

  In addition, the inner conductor has an insulating layer on the outer side, and this insulating layer has not only electrical insulation but also thermal insulation functions to some extent. For this reason, it is recommended to supply gas nitrogen instead of liquid nitrogen during maintenance. When the temperature is raised, the rate of temperature rise of the inner conductor becomes relatively slow, and it can be said that ballooning hardly occurs. However, since the outer conductor has gas nitrogen immediately outside, the rate of temperature rise is increased, the wire material is likely to be ballooned, and there is a high possibility that problems such as a decrease in critical current will occur. Therefore, the occurrence of ballooning can be effectively suppressed by using a superconducting wire having a highly dense filament at least as the superconducting wire of the outer conductor.

  A superconducting wire having a density with substantially no voids in the superconducting filament can be obtained by, for example, a pressure sintering method. The pressure sintering method is a powder-in-tube method for producing a superconducting wire, in which pressure is applied by gas when sintering the wire that is the source of the superconducting wire, and external pressure is applied isotropically to the wire. It is. The wire manufactured by this method has a density of almost 100%, and there is substantially no void into which the refrigerant enters.

  The production of superconducting wire by the powder-in-tube method is, for example, “Adjusting the raw material powder of the superconducting phase → Clad wire (single core wire) → Manufacture of multi-core wire → Production of primary rolling wire → Primary heat treatment → Production of secondary rolling wire → This is performed by a process called “secondary heat treatment”. In the pressure sintering method, for example, secondary heat treatment is performed in a pressurized atmosphere. As the gas at the time of pressurization by the pressure sintering method, a mixed gas of an inert gas and oxygen is suitable. The pressure applied at that time is preferably 15 to 50 MPa. In the case of a mixed gas of an inert gas and oxygen, the oxygen partial pressure is preferably 7 kPa or more and 21 kPa or less. By this pressure adjustment, an external pressure due to the atmospheric gas is applied isotropically to the wire, and the density of the superconducting filament can be improved. Inert gases include nitrogen, argon, helium, and neon. The atmosphere of this heat treatment may be air. This pressure-adjusted pressure heat treatment may be performed for both the heat treatment and the secondary heat treatment when the primary heat treatment and the secondary heat treatment are performed. This pressure sintering method is described, for example, in “Development of Bismuth Superconducting Wire”, Kohei Yamazaki, etc. “SEI Technical Review”, No.164, pages 36-41, March 2004.

  Although we have already mentioned that superconducting wires with high-density filaments are used for at least the outer conductor, ballooning can be prevented on both the inner and outer conductors by using superconducting wires with high-density filaments on the inner conductor. More preferable. At that time, since the fault current flowing in the inner conductor is shunted to the core material, the cross-sectional area of this core material is the inner conductor temperature when the fault current flows to the inner conductor for the same reason as in the normal conductive layer. However, the temperature is selected so that the temperature rise of the inner conductor at the refrigerant pressure at the refrigerant pressure during operation of the superconducting cable is 100K or less. With this configuration, the inner conductor is allowed to have a temperature equal to or higher than the boiling point of the refrigerant, and the diameter of the core material can be reduced as compared with the conventional one, which can contribute to the reduction in the diameter of the cable core.

  The superconducting wire used for the inner and outer conductors of the cable of the present invention may be a wire in which a linear superconducting filament is arranged in the stabilizing material, or a superconducting filament twisted in a spiral is arranged in the stabilizing material. A twisted wire may be used. In particular, the use of twisted wires is effective in reducing AC loss in the case of AC cables. In the case of a twisted wire, the induced current flowing between the stabilizing material and the filament is divided for each twisting pitch of the filament, flows as a small loop, and the magnitude of the current is limited. As a result, Joule heat generation of the stabilizing material can be avoided, and reduction of AC loss can be achieved.

  In the cable of the present invention, it is preferable that the core material and the normal conducting layer serving as the shunt path for the accident current are made of a material having high conductivity from the viewpoint of suppressing heat generation during the shunt of the accident current. For example, Cu, Al, Mg, or an alloy containing any of these as a main component can be suitably used. Of these, the core material is preferably formed by twisting strands. By making the core material a stranded wire structure, the flexibility of the core material can be ensured. The normal conductive layer is preferably used in the form of a round wire or a tape wire. More specifically, the normal conducting layer may be formed by spirally winding these round wires or tape wires on at least one of the inside and outside of the outer conductor layer. By using the normal conducting wire in such a form for the normal conducting layer, it is easy to ensure the flexibility of the normal conducting layer. In particular, when a tape wire having a rectangular cross section is used, the gap between the tape wires can be made smaller than in the case of a round wire, and a high space factor can be secured.

  Each of the normal conducting wires used for the core material and the normal conducting layer preferably has an insulating coating. When superconducting cables are used for AC applications, eddy current loss occurs when a magnetic field is applied to the normal conducting wire, but each normal conducting wire constituting the core material and the normal conducting layer is electrically insulated. Thus, eddy current loss can be reduced. As this insulating coating, a plastic coating such as enamel can be suitably used.

  The present invention can be used not only for single-core cables but also for multi-core cables. In addition, the present invention can be used with either an AC cable or a DC cable. In the case of AC cable, the outer conductor serves as a shield layer, and when the cable is operated, a reverse current is induced with approximately the same size as the inner conductor to cancel the magnetic field generated from the inner conductor and prevent leakage of the magnetic field to the outside. To do. In the case of a DC cable, for example, in unipolar power transmission, the inner conductor can be used as a forward current flow path, and the outer conductor can be used as a return current flow path.

  According to the superconducting cable of the present invention, the following effects can be obtained.

  (1) If a superconducting wire having a density with substantially no voids in the superconducting filament is used, ballooning caused by vaporization of the refrigerant entering the voids in the filament can be prevented.

  (2) By using a superconducting wire that does not substantially cause ballooning, the superconducting wire is allowed to be heated to a temperature higher than the boiling point of the refrigerant at the refrigerant pressure during cable operation. Therefore, it is possible to reduce the cross-sectional area of the core material or the normal conductive layer that becomes a branch path of the accident current flowing in the superconducting wire, and the outer diameter of the cable core can be reduced.

  (3) By selecting the cross-sectional area of the normal conducting layer (core material) that can reduce the temperature rise of the superconducting wire to 100K or less, the refrigerant temperature necessary for operating the cable can be adjusted early. it can. Also, by defining the cross-sectional area of the normal conducting layer (core material) in this way, the accident current diverted to the superconducting wire is reduced, the degree of thermal expansion of the superconducting wire at that time is reduced, and the cable terminal portion It is also possible to suppress the occurrence of buckling due to the expansion of the wire.

  Embodiments of the present invention will be described below.

[Overall structure]
As shown in FIG. 1, the AC superconducting cable 100 of the present invention is composed of a single cable core 10 and a heat insulating tube 20 that houses the core 10.

[core]
The core 10 includes, in order from the center, a former (core material) 11, a superconducting conductor layer (inner conductor) 12, an insulating layer 13, a superconducting shield layer (outer conductor) 14, a normal conducting shield layer (normal conducting layer) 15, and protection It has a layer 16.

<Former>
The former 11 is a core member for maintaining the shape of the superconducting conductor layer 12 and, when an accident current flows through the conductor layer 12, functions as a flow path to suppress damage to the conductor layer 12. It has a function. Here, an insulation element wire in which an enamel insulation coating was formed on a Cu wire was twisted to form a stranded wire structure former with a diameter of 15.2 mm. In this former, 2.6 mmφ × 19 insulation strands are arranged on the center side, and 1.5 mmφ × 30 insulation strands are arranged on the outer periphery thereof.

<Superconducting conductor layer>
For the superconducting conductor layer 12, a Bi2223-based Ag sheathed tape wire having a thickness of 0.24 mm and a width of 3.8 mm was used. This tape wire is a twisted wire manufactured by a pressure sintering method and having a spiral superconducting filament. More specifically, a tape wire is obtained as follows. First, a raw material powder mainly composed of Bi2212 phase is inserted into a silver pipe and drawn to obtain a single-core clad wire. Next, a plurality of clad wires are inserted into another silver pipe, and the silver pipe is drawn to produce a 61-core multi-core wire. The obtained multifilamentary wire is twisted and lightly drawn, then rolled at a reduction rate of 80% (primary rolling), and processed into a tape-like primary rolled wire. The obtained primary rolled wire is subjected to a primary heat treatment in an inert gas and oxygen atmosphere at a total pressure of 0.1 MPa, an oxygen partial pressure of 8 kPa, and 830 ° C. for 30 hours to obtain a primary heat treated wire in which a Bi2223 phase is generated. This primary heat-treated wire is re-rolled at a rolling reduction of 10% (secondary rolling) to obtain a secondary rolled wire having a thickness of 0.24 mm and a width of 3.8 mm. Then, the secondary rolled wire is subjected to secondary heat treatment in an atmosphere of inert gas and oxygen at a total pressure of 30 MPa and an oxygen partial pressure of 8 kPa to obtain a superconducting wire. The obtained superconducting wire is a wire having a structure in which a spiral 61-core superconducting filament is embedded in an Ag stabilizing material. The density of this superconducting filament is almost 100%, and it does not have voids that allow the refrigerant to enter substantially. The tape wire is wound in multiple layers on the former 11 to form the conductor layer 12. Here, a superconducting wire is wound around the four layers. The winding direction of each layer was SSZZ in order from the inner layer side.

<Insulating layer>
An insulating layer 13 is formed on the superconducting conductor layer 12. The insulating layer 13 has a function of electrical insulation against alternating current flowing through the conductor layer 12. Here, the insulating layer 13 is made of PPLP (registered trademark of Sumitomo Electric Industries, Ltd.) in which polypropylene and kraft paper are joined. Although not shown, an inner semiconductive layer is formed on the inner peripheral side of the insulating layer 13, and an outer semiconductive layer is formed on the outer peripheral side. All the semiconductive layers were formed by winding carbon paper.

<Superconducting shield layer>
A superconducting shield layer 14 is provided outside the insulating layer 13. The superconducting shield layer 14 cancels out the magnetic field generated from the superconducting conductor layer 12 and prevents leakage of the magnetic field to the outside by inducing a reverse current in the same size as the superconducting conductor layer 12 during cable operation. To do. Here, a superconducting wire obtained by the same pressure sintering method as that of the superconducting conductor layer 12 was used. More specifically, it is composed of two layers, and the winding direction of each layer is SS.

<Normal conducting shield layer>
Subsequently, the normal conducting shield layer 15 was formed on the superconducting shield layer 14. The normal conducting shield layer 15 serves as a shunt path for the accident current in order to prevent the superconducting shield layer 14 from being damaged due to an excessive accident current being induced in the case of a short circuit accident or the like. . Here, an enamel-coated copper wire is spirally wound around the superconducting shield layer 14. This normal conducting shield layer 15 is composed of two layers, and uses a tape-shaped copper wire having a width of 4 mm and a thickness of 0.25 mm. The winding direction of each layer of the normal conducting shield layer 15 was SZ in order from the inner layer side.

<Protective layer>
A protective layer 16 made of an insulating material is provided outside the normal conducting shield layer 15. Here, the protective layer 16 is constituted by winding kraft paper. The protective layer 16 can provide mechanical protection for the normal conducting shield layer 15 and can be insulated from the heat insulating tube (inner tube 21) to prevent shunting of the induced current to the heat insulating tube 20.

[Insulated pipe]
The heat insulating tube 20 is a double tube including an inner tube 21 and an outer tube 22, and a vacuum heat insulating layer is formed between the inner and outer tubes 21 and 22. A so-called super insulation (trade name) in which a plastic mesh and a metal foil are laminated is disposed in the vacuum heat insulating layer. A space formed between the inner side of the inner tube 21 and the core 10 serves as a refrigerant flow path. A polyvinyl chloride anticorrosion layer 23 is formed on the outer periphery of the heat insulating tube 20.

[Example calculation]
In the above superconducting cable, when operating with liquid nitrogen as a refrigerant, the temperature rise of the superconducting conductor layer and the superconducting shield layer when an accident current 40 times the rated current flows was calculated. The estimation results are shown below.
Refrigerant boiling point at the same pressure as the refrigerant pressure during rated current operation: 2 atm, 84K
Temperature T1 of conductor layer 12 and shield layer 14 during rated current operation: 77K
Temperature T2 of the conductor layer 12 and the shield layer 14 when an accident current flows: 127K
Temperature rise range T2-T1: 50K

  According to the above superconducting cable, since the superconducting wire having a density with substantially no voids in the superconducting filament is used, it is possible to prevent ballooning caused by vaporization of the refrigerant entering the voids in the filament. it can.

  In addition, the temperature T2 of the superconducting conductor layer and the superconducting shield layer when an accident current flows exceeds the refrigerant boiling point of 84K, but by using a superconducting wire that does not substantially cause ballooning, the superconducting wire can The temperature is allowed to rise above the boiling point of the refrigerant at the current refrigerant pressure.

  Furthermore, the temperature rise width T2-T1 is 50K, which is 100K or less. Therefore, the degree to which the superconducting wire expands due to the temperature rise due to the accident current flowing is low, and it is possible to suppress the occurrence of buckling due to the expansion of the wire at the cable terminal portion. In addition, even when the superconducting wire is cooled again and the superconducting cable is operated, it can be restored in a relatively short time.

  On the other hand, if the temperature T2 of the superconducting conductor layer and the superconducting shield layer when an accident current flows is set to be equal to or lower than the boiling point of the refrigerant at the refrigerant pressure at the rated current operation, the outer diameter of the core material is 20 mm, and the normal conducting shield layer Six layers of tape-shaped copper wires were required. Therefore, the cable of the present invention can reduce the cross-sectional area of the former and the normal conducting shield layer, and can reduce the outer diameter of the cable core.

  The superconducting cable of the present invention can be used as an AC or DC power transportation means.

It is a cross-sectional view of the superconducting cable of the present invention. It is a cross-sectional view of a superconducting cable.

Explanation of symbols

100 superconducting cable
10 core
11 Former 12 Superconducting conductor layer 13 Insulating layer
14 Superconducting shield layer 15 Normal conducting shield layer 16 Protective layer
20 Insulated pipe
21 Inner pipe 22 Outer pipe 23 Anticorrosion layer

Claims (8)

A core material made of a normal conductive material, a superconducting inner conductor provided outside the core material, an insulating layer provided outside the superconducting inner conductor, a superconducting outer conductor provided outside the insulating layer, and a superconducting outer conductor. A superconducting cable provided on at least one of the inside and the outside and having a normal conducting layer to which an accidental current flowing in the superconducting outer conductor is shunted,
At least the superconducting outer conductor is made of a superconducting wire in which a superconducting filament is arranged in a stabilizing material. This superconducting wire is manufactured by pressure sintering, so that the superconducting filament is substantially free of voids. Has no density,
The cross-sectional area of the normal conducting layer is such that the temperature of the superconducting outer conductor when the fault current flows to the superconducting outer conductor transferred to the normal conductor is equal to or higher than the boiling point of the refrigerant at the refrigerant pressure during operation of the superconducting cable. A superconducting cable, characterized in that the temperature rise of the superconducting outer conductor is selected to be 100K or less. Furthermore, a superconducting wire in which a superconducting filament is arranged in a stabilizing material is used for the superconducting inner conductor, and this superconducting wire is manufactured by a pressure sintering method. Have a degree,
Cross-sectional area of the core material, a superconducting inner conductor temperature when the fault current flows in the superconducting inner conductor that has metastasized to the normal conductor is in refrigerant above the boiling point of the refrigerant pressure during operation of the superconducting cable, superconducting at that time The superconducting cable according to claim 1, wherein the temperature rise of the inner conductor is selected to be 100K or less.   The superconducting cable according to claim 1 or 2, wherein the superconducting wire is a superconducting wire obtained by a pressure sintering method.   The superconducting cable according to any one of claims 1 to 3, wherein the core material is formed by twisting strands made of Cu, Al, Mg, or an alloy containing any of these as a main component.   The superconducting cable according to claim 4, wherein each of the strands has an insulating coating.   The superconducting cable according to any one of claims 1 to 5, wherein the normal conducting layer is made of a round wire or a tape wire made of Cu, Al, Mg, or an alloy containing any of these as a main component. .   The superconducting cable according to claim 6, wherein the round wire or the tape wire has an insulating coating. The superconducting wire comprises a stabilizing material and a superconducting filament built in the stabilizing material,
The superconducting cable according to claim 1, wherein the filament is twisted in a spiral shape.

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