WO2007080794A1

WO2007080794A1 - Superconducting cable

Info

Publication number: WO2007080794A1
Application number: PCT/JP2006/326091
Authority: WO
Inventors: Hiroyasu Yumura
Original assignee: Sumitomo Electric Industries, Ltd.
Priority date: 2006-01-16
Filing date: 2006-12-27
Publication date: 2007-07-19
Also published as: JP5115778B2; TW200735128A; JP2007188844A

Abstract

A superconducting cable comprising a core material (former), and a conductor layer composed of a superconducting thin film wire wound thereon, wherein the superconducting thin film wire has a metal substrate, and an RE based superconducting thin film formed only on one surface of the substrate. Since the superconducting thin film wire can be wound such that the surface on which the RE based superconducting thin film is formed directs outward with respect to the core material and the low resistance surface on the superconducting thin film side can be located on the outer circumferential side of the cable, connection resistance can be decreased at the joint when a connection member is fitted over the outer circumference of the superconducting thin film wire and joined, resulting in a superconducting cable in which resistance can be decreased at the joint.

Description

Specification

Superconducting cable

Technical field

[0001] The present invention relates to a superconducting cable. In particular, it relates to superconducting cables using RE (rare earth) superconducting thin film wires.

Background art

[0002] Bi-based superconducting wires represented by BSCCO (Bi-Sr-Ca-Cu-O) tape wires are being put into practical use as superconducting wires. The BSCCO tape wire is a tape wire having a structure in which a plurality of superconducting filaments made of, for example, Bi2223 phase are embedded in a stable brazing material such as silver. This Bi-based superconducting wire has the advantage that it can be easily processed into a wire, and although it has been proposed to be applied to superconducting cables, superconducting motors, superconducting transformers, etc., it has an even higher field current density (Jc). Improvement is desired.

[0003] On the other hand, RE-based superconducting thin film wires are being developed as next-generation superconducting wires (for example, Patent Document 1). Figure 6 shows a typical configuration of RE-based superconducting thin film wires. The wire 3 is a tape wire in which an intermediate layer 32, a superconducting thin film 33, and a protective layer 34 are sequentially laminated on a tape-shaped metal substrate 31. Specific examples include Hastelloy (registered trademark) as the metal substrate 31, YSZ as the intermediate layer 32, Y-type 123 (YBa Cu Oy) thin film as the superconducting thin film 33, and protective layer 34.

twenty three

Silver is used. Usually, the intermediate layer 32 and the superconducting thin film 33 are formed only on one side of the substrate 31 by laser vapor deposition or the like.

[0004] Such a RE-based superconducting thin film wire has a higher critical current density (Jc) than that of a Bi-based superconducting wire, and a decrease in critical current (Ic) due to a magnetic field is excellent. It is expected to be used as a next-generation wire following conductive wires.

Patent Document 1: Japanese Patent Laid-Open No. 2001-31418

Disclosure of the invention

Problems to be solved by the invention

[0006] However, when the above RE-based superconducting thin film wire is applied to a superconducting cable, it has been found that the resistance increases at the connection point of the cable. [0007] In general, a superconducting cable has a structure in which one or more cores are housed in a heat insulating tube. The core includes a core material and a superconducting wire wound around the outer periphery of the core material to form a conductor layer. Here, when a RE superconducting thin film wire having a superconducting thin film on one side of the substrate is wound as a superconducting wire, the superconducting thin film is wound inside, that is, on the core material side. This is because when a superconducting thin film wire is wound, a compressive strain is generated inside the bend and a bow I tension strain is generated outside the bend. This is because it is better in bending characteristics to arrange the inside.

However, in order to construct a line with a superconducting cable, it is necessary to connect a conductor layer at a connection point between the cables. Usually, this connection is performed by fitting a connection member such as a copper sleeve outside the conductor layer of the abutted cable and soldering between the conductor layer and the connection member. At that time, since the superconducting thin film wire constituting the conductor layer is wound with the superconducting thin film inside, the substrate side is located outside the conductor layer. As a result of conducting a test 'examination as will be described later on the connection resistance of the connection portion in this state, the present inventors have found that the connection member and the surface of the superconducting thin film wire are connected via solder. The knowledge that connection resistance becomes large was obtained.

[0009] The present invention has been made in view of the above circumstances, and one of its purposes is to provide a superconducting cable capable of reducing the resistance of a connection point.

Means for solving the problem

[0010] In the present invention, when the RE-based superconducting thin film is used as a superconducting wire having a superconducting thin film only on one side, the above object is achieved by devising the winding method.

The superconducting cable of the present invention is a superconducting cable comprising a core material and a conductor layer made of a superconducting thin film wire wound thereon. The superconducting thin film wire has a metal substrate and a RE superconducting thin film formed only on one side of the substrate. And this invention is

The wire is wound so that the surface on which the RE-based superconducting thin film is formed faces outward with respect to the core material.

[0012] With this configuration, since the surface on the superconducting thin film side having a low resistance can be positioned on the outer peripheral side of the cable, the connection member is fitted on the outer periphery of the superconducting thin film wire. In this case, the connection resistance at the connection location can be reduced.

[0013] The cable of the present invention may have a configuration having a superconducting shield layer. That is, a superconducting thin film having an insulating layer and a superconducting shield layer sequentially on the outside of the conductor layer, the superconducting shield layer having a metal substrate and an RE-based superconducting thin film formed only on one side of the substrate. Use wire. Then, the superconducting thin film wire is wound so that the surface on which the superconducting thin film is formed faces outward with respect to the insulating layer.

[0014] According to this configuration, when alternating current is passed through the conductor layer, a reverse current is induced in the superconducting shield layer and the magnetic field generated in both layers is canceled. preferable. In addition, the connection resistance at the connection point of the superconducting shield layer in the butt cable can be reduced.

[0015] The RE-based superconducting thin film of the superconducting thin film wire used in the cable of the present invention is preferably composed of a Ho-based superconductor or a Y-based superconductor.

[0016] The Ho-based superconductor or the Y-based superconductor has a high deviation and can obtain a current density, and is a material suitable for forming a conductor layer and a shield layer of a superconducting cable. In particular, Ho-based superconductors are more resistant to moisture degradation than Y-based superconductors.

[0017] Further, in the cable of the present invention, a normal conducting connecting member electrically connected to the superconducting thin film wire at the end is provided at the end of the superconducting cable, and the normal conducting connecting member and the superconducting thin film wire are provided. It is also preferable that the connection length in the longitudinal direction of the cable with the conductor layer is 20 mm or more.

[0018] By setting the connection length to 20 mm or more, the contact length between the superconducting thin film wire and the connection member can be secured, and the connection resistance can be sufficiently reduced. The connection length is the length in the longitudinal direction of the cable at a location where the superconducting thin film wire and the normal conducting connecting member are electrically connected by solder.

The invention's effect

According to the superconducting cable of the present invention, the thin film side is wound on the outer peripheral side of the cable by winding the superconducting thin film wire so that the surface on which the RE-based superconducting thin film is formed faces outward with respect to the core material. Can be located. Along with this, it is possible to reduce connection resistance when a connection structure is formed by arranging a connection member outside the conductor layer. Brief Description of Drawings

FIG. 1 is a cross-sectional view of the superconducting cable of the present invention.

FIG. 2 is a schematic perspective view showing an end portion of a core of the cable of the present invention.

FIG. 3 is a cross-sectional view of an RE-based superconducting thin film wire used in the cable of the present invention.

FIG. 4 is an explanatory diagram showing a test method for a resistance measurement test.

FIG. 5 is a graph showing the measurement results of a resistance measurement test.

FIG. 6 is a schematic perspective view showing a configuration of a RE-based superconducting thin film wire.

Explanation of symbols

[0021] 1 Heat insulation pipe 11 Inner pipe 12 Outer pipe

2 core

21 Former 22 Superconducting conductor layer 23 Insulating layer

24 Superconducting shield layer 25 Outer layer 26 Interlayer insulation

3 RE-based superconducting thin film wire

31 (Metal) substrate 32 Intermediate layer 33 Superconducting thin film 34 Protective layer 35 Stabilization layer 41

Copper plate 42 Solder 43 DC power supply

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described. Hereinafter, the same reference numerals in the drawings denote the same items. The dimensional ratios in the drawings do not necessarily match those described.

The superconducting cable of the present invention typically has a structure in which a core 2 is accommodated in a heat insulating tube 1 as shown in FIG. As shown in FIG. 2, the core 2 includes a former 21, a superconducting layer 22, an insulating layer 23, a superconducting shield layer 24, and an outer layer 25 in this order. The superconducting thin film wire 3 is used for the superconducting conductor layer 22 and the superconducting shield layer 24.

As shown in FIG. 3, the superconducting thin film wire 3 has a substrate 31, an intermediate layer 32, a RE-based superconducting thin film 33, a protective layer 34, and a stable layer 35. Here, the intermediate layer 32, the superconducting thin film 33, and the protective layer 34 are sequentially laminated on the upper surface side of the substrate 31, and the protective layer 34 is also formed on the lower surface side of the substrate 31, so that the entire stacked structure is formed. Cover with stabilizing layer 35.

[0025] Such a wire is wound on the core so that the substrate is on the inside and the superconducting thin film is on the outside. FIG. 2 shows the case where the conductor layer 22 is composed of four layers of superconducting thin film wire 3 and the shield layer 24 is composed of two layers of superconducting thin film wire 3. These superconducting thin film wires are spirally wound in multiple layers, and an interlayer insulation 26 is provided between each wire layer. By winding the wire 3, the superconducting thin film side of the wire is positioned on the outer peripheral side of both the conductor layer 22 and the shield layer 24. Therefore, when connecting superconducting cables, or when connecting a superconducting cable and another device, fit a connecting member (not shown) outside the conductor layer 22 or shield layer 24 at the end of the cable, A connection portion with a low connection resistance can be formed by flowing solder between the conductor layer 22 and the conductor layer 22 (shield layer 24). For the connection member, a Cu sleeve or the like is used for the connection of the conductor layer 22, and a Cu braided material or a Cu sleeve is used for the connection of the shield layer 24.

[0026] Hereinafter, a preferable configuration of each component of the superconducting cable of the present invention will be described.

[0027] First, regarding the superconducting thin film wire 3, the substrate 31 is made of a metal material (Fig. 3). Examples of preferable metals include nickel alloys (Northernloy (registered trademark)), stainless steel, nickel and the like. The substrate 31 may be a single material force or a composite material. Examples of the substrate 31 made of a composite material include those obtained by laminating a silver foil on a stainless steel foil. As the form of the substrate 31, a tape material is preferably used.

[0028] The intermediate layer 32 plays a role of preventing deterioration of superconducting characteristics by diffusion of components in the substrate 31 to the superconducting thin film 33, but is not an essential configuration. The intermediate layer 32 can be omitted. The intermediate layer 32 may be made of cerium oxide, yttria stable zirconia (YSZ), magnesium oxide, yttrium oxide, ytterbium oxide, norium zirconia, or the like. In particular, a high-conductivity superconducting wire can be obtained by imparting orientation to the crystals of the intermediate layer 32. As a method for forming the intermediate layer 32, a laser vapor deposition method or the like can be suitably used.

[0029] The superconducting thin film 33 is of RE type. Typically, an oxide superconductor thin film having a structure of RE Ba Cu O is used. “RE” here is a rare earth element. Examples of rare earth elements include yttrium (γ), neodymium (Nd), and gadolinium. ) And samarium (Sm). Specific examples of this superconducting thin film 33 include RE123, that is, YBa Cu O,

2 3 7

HoBa Cu O and so on. This superconducting thin film 33 is one of the front and back sides of the substrate 31. It is formed only on the surface. As a method for forming the superconducting thin film 33, a laser vapor deposition method or the like can be suitably used.

[0030] For the protective layer 34, for example, Ag or an Ag alloy is preferably used. Silver is preferable because it has little reaction with the superconducting thin film 33.

[0031] For the stable layer 35, Cu, Cu alloy, or the like can be suitably used. The stable layer 35 can be formed by, for example, plating.

[0032] Next, the force (FIG. 2) about the core 2 can be suitably used for the former 21 such as a hollow pipe or a copper stranded wire. For the insulating layer 23, kraft paper or composite paper in which kraft paper and polyolefin film are laminated can be used. Further, the outer layer 25 protects the shield layer 24 and secures insulation against the heat insulating pipe 1 (FIG. 1), and various plastics such as polyethylene can be used.

[0033] Further, as the heat insulating tube 1 (FIG. 1), a vacuum structure using a double tube is preferably used.

For example, a vacuum is drawn between the inner pipe 11 and the outer pipe 12 and a super insulation (trade name) is arranged between the two pipes.

[0034] (Test example)

A bending test was conducted using the RE-based superconducting thin film wire shown in Fig. 3, and changes in the Ic characteristics were examined. In this test, a wire sample is placed along an FRP bending jig with a specific bending diameter, bending strain is applied to the wire at room temperature, and the field current value (Ic) at the liquid nitrogen temperature before and after bending is measured. The Ic retention rate after applying bending strain was determined, and the bending diameter at which Ic did not deteriorate was determined. The definition of Ic degradation is that Ic has decreased by more than 5% compared to the initial value before bending. The bending diameter was reduced by 50mm even at 5mm intervals. At this time, the test was performed for each of the RE-based superconducting thin film wire material with the RE-based superconducting thin film inside and outside the bending.

[0035] The specifications of the wire used for the test are as follows.

Wire width: approx. 4mm, wire thickness: approx. 0.15mm

Substrate: Hastely (registered trademark) thickness lOO / z m

Intermediate layer: YSZ thickness Superconducting thin film: YBCO thickness l / zm

Protective layer: Ag thickness

Stabilization layer: Cu thickness 20 m

[0036] The results are as follows.

Inside of bending YBCO: Bending diameter up to 10mm No reduction in Ic, Ic reduction at 5mm

Outside YBCO bending: bending diameter up to 25mm, no decrease in Ic, decrease in Ic at 20mm

[0037] As is clear from this result, when the wire is wound so that YBCO is inside the bend, YBCO is subjected to compressive strain, and Ic is lower than when the wire is wound in the opposite direction. It turns out that it is difficult to do. In other words, when YBCO is placed inside the bend, the limit bend diameter can be made smaller than in the reverse case, and the wire can be wound around the smaller diameter core material at a short pitch.

[0038] <Resistance measurement test>

Next, in the superconducting cable as shown in FIG. 1 and FIG. 2, the connection resistance was measured by the following test assuming that the conductor layers are connected to each other through a connecting member.

[0039] The test method will be described with reference to FIG. In this test, the RE-based superconducting thin film wire 3 used in the bending test was prepared, and at both ends of the wire 3, a copper plate 41 simulating a connecting member was connected to the surface on the YBCO side or substrate side with solder 42. deep. Then, a direct current power source 43 was connected to the copper plate 41 and energized, and the voltage between the copper plate 41 and the wire 3 was measured to obtain the resistance. At that time, the resistance was measured by changing the length (corresponding to the connection length) in the longitudinal direction of the wire where soldering was performed to 10, 20, and 50 mm. For comparison, the same resistance measurement was performed using BSCCO superconducting wire instead of RE superconducting thin film wire. However, since the BSCCO superconducting wire has no front and back sides, the measurement is performed when a connecting member is connected to either side.

[0040] The results are shown in the graph of FIG. As is apparent from this graph, when the connecting member is soldered to the superconducting thin film side of the RE superconducting thin film wire, the connection resistance is almost the same as when using the BSCCO superconducting wire, and the RE superconducting thin film It can be seen that the connection resistance is about 1/5 compared to the case where the connection member is soldered to the substrate side of the wire. In particular, it can be seen that the connection resistance decreases as the connection length exceeds 20 mm. [0041] <Summary>

To summarize the results of the above bending test and resistance measurement test, it is preferable to wind the RE superconducting thin film wire with the superconducting thin film inside, considering the decrease in Ic due to bending strain. Considering the connection resistance when forming the connection part of the superconducting cable, it is preferable to wind the RE superconducting thin film wire with the superconducting thin film outside. As a result, the connection resistance of the connection portion can be reduced, and local heat generation at the connection portion can be suppressed.

[0042] The embodiment disclosed this time should be considered as illustrative in all points and not restrictive! The scope of the present invention is shown not by the above-described embodiment but by the scope of claims for patent, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims for patent are included.

Industrial applicability

[0043] The superconducting cable of the present invention can be used to construct a power transport line. In particular, it can be suitably used for construction of a line in which the connection resistance between the connection points of the cables is reduced.

Claims

The scope of the claims

[1] A superconducting cape nore comprising a core material and a conductor layer made of a superconducting thin film wire wound thereon,

The superconducting thin film wire is

It has a metal substrate and an RE-based superconducting thin film formed only on one side of the substrate, and is wound so that the surface on which the superconducting thin film is formed faces outward with respect to the core material. Features superconducting cable.

[2] Further, an outer insulating layer and a superconducting shield layer are sequentially provided outside the conductor layer.

For this superconducting shield layer, a superconducting thin film wire having a metal substrate and an RE-based superconducting thin film formed only on one side of the substrate is used.

2. The superconducting cable according to claim 1, wherein the superconducting thin film wire is wound so that a surface on which the superconducting thin film is formed faces outward with respect to the insulating layer.

[3] The superconducting cable according to claim 1 or 2, wherein the RE-based superconducting thin film of the superconducting thin-film wire is composed of a Ho-based superconductor or a Y-based superconductor.

[4] Further, the end portion of the superconducting cable is provided with a normal conducting connecting member electrically connected to the superconducting thin film wire by solder,

The superconducting cable according to any one of claims 1 to 3, wherein a connection length in a longitudinal direction of the cable between the normal conductive connecting member and the conductor layer is 20 mm or more.