JPH07114838A - Oxide superconducting cable - Google Patents

Abstract

PURPOSE:To prevent decrease in critical current characteristics and enhance flexibility to increase installation workability by arranging a spiral oxide superconductive element wire in the circumference of a cable former comprising a spiral pipe or corrugated pipe covered with a wire interwoven material. CONSTITUTION:A wire material interwoven cover layer 2 made of fibers or ribbons with uneven surface as a buffer is arranged in a cable former 1 made of a stainless steel spiral pipe or corrugated pipe. Oxide superconductive element wires 3, 4 are spirally piled up on the cover layer 2 in multilayer winding structure to form a cable. By using the spiral pipe or the corrugated pipe as the cable former, the stress-strain of the element wire generating by expansion coefficient difference between the element wire and the cable former is decreased to prevent drop in critical current characteristics. By the flexibility based on the shape change, installation work is facilitated and workability is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconducting cable which is suitable for power cables and has excellent layability and excellent superconducting properties.

[0002]

2. Description of the Related Art A system for realizing high current transmission with a compact power cable by utilizing the characteristics of an oxide superconductor has been studied.

Conventionally, as a power cable used in such a system, there has been known one in which an oxide superconducting wire having a metal sheath is spirally wound around the outer circumference of a cable former made of a metal pipe. However, when cooled to a low temperature to form a superconducting state, characteristics such as critical current are deteriorated, and it is difficult to bend the cable, and the flexibility is poor and workability at the time of laying is poor.

[0004]

DISCLOSURE OF THE INVENTION The present invention exhibits good flexibility and is excellent in laying workability, and when the cable is cooled to a low temperature, characteristics such as critical current are unlikely to be deteriorated and superconducting characteristics are excellent. A subject is to obtain an oxide superconducting cable.

[0005]

According to the present invention, a spiral wire made of an oxide superconducting wire having a metal sheath is provided on the outer circumference of a cable former made of a spiral tube or a corrugated tube covered with a wire knitted material. The present invention provides an oxide superconducting cable characterized by the above.

[0006]

By using the spiral tube or the corrugated tube as the cable former, it is possible to prevent the characteristics such as critical current from being deteriorated when the cable is cooled to a low temperature, and to improve the deformability of the spiral tube or the corrugated tube. Based on this, a cable having good flexibility and excellent workability in laying can be obtained.
In order to prevent the characteristic deterioration due to the low temperature cooling, the thermal deformation difference due to the difference in expansion coefficient between the wire and the cable former during low temperature cooling is deformed by reducing the diameter of the spiral tube or corrugated tube, and the deformation It is considered that the stress strain generated in the oxide superconducting wire forming the twisted wire is reduced by absorbing the shrinkage of the wire due to low temperature cooling.

Further, in the above description, a cable former is formed by coating the outer periphery of the spiral tube or corrugated tube with a wire material knitted product, and the oxide provided in a spiral shape on the spiral tube or corrugated tube without impairing the above advantages. It is possible to improve the contact area or the close contact state between the superconducting wire and the cable former, and thereby prevent or suppress the occurrence of local strain of the oxide superconducting wire due to partial contact with the cable former. The local strain of the oxide superconducting wire causes a decrease in the critical current.

[0008]

EXAMPLE An oxide superconducting cable of the present invention has a spiral wire made of an oxide superconducting wire having a metal sheath on the outer circumference of a cable former made of a spiral tube or a corrugated tube covered with a wire rod formation. It is a thing.

An example of such an oxide superconducting cable is shown in FIG.
It is shown in FIG. Reference numeral 1 is a cable former made of a spiral tube, 2 is a coating layer made of a knitted wire material, 3 is a first-layer strand, and 4 is a second-layer strand. Further, 5 is a cable former composed of a corrugated pipe. In addition, 6 is a polymer film layer provided on the coating layer 2 of the knitted wire material,
This can be provided on either a spiral or corrugated cable former as required.

The spiral tube and corrugated tube used as the base of the cable former in the present invention may be appropriately selected depending on the oxide superconducting cable to be formed.
Generally, as a spiral tube, a plate wire having a width of 2 to 10 mm and a thickness of 1 to 5 mm is spirally wound into a tubular shape having an outer diameter of 10 to 30 mm with a gap of 1 to 5 mm provided. Part-contact type or convex pitch is 30 cm or less, especially 15 cm
In the following, a recess having a depth of 1 to 10 mm, an outer diameter of 10 to 30 mm and a wall thickness of 1 to 5 mm is used.

As the material for forming the spiral tube and the corrugated tube, metals such as stainless steel, silver and copper or plastics, or FRP using carbon fiber or glass fiber is generally used. For forming a cable for AC power transmission, a spiral tube or corrugated tube made of FRP or the like is advantageous because power loss is small.

The coating layer composed of the wire rod knitted material on the outer periphery of the spiral tube or corrugated tube is in a state where the oxide superconducting wire forming the stranded wire is in partial contact with the spiral tube or corrugated tube due to gaps or irregularities, It is provided for the purpose of preventing the deterioration of the characteristics caused by the local strain due to the stress difference in the oxide superconducting wire due to the bending and extension of the cable.

The knitted wire material is preferably one in which the coating layer functions as a buffer layer for the uneven surface of the spiral tube or corrugated tube and does not cause local strain in the oxide superconducting wire provided in a spiral shape in the cable former. A spiral tube or corrugated tube having an appropriate thickness depending on the size of the surface irregularities is used. In addition, it is preferable that the cable former has a smooth surface with respect to the oxide superconducting wire provided in a spiral shape including the polymer film layer used as necessary. Therefore, the cross-sectional dimension of the oxide superconducting wire provided in a spiral shape is preferable. For example, a material having an appropriate gap may be used.

As the wire rod knitted material, fibers made of metal such as stainless steel, silver, copper, polyimide, polyester, plastics such as fluororesin, ceramics such as glass, wire rods such as ribbons, or carbon fibers are woven or woven. It is possible to use a material knitted in an appropriate shape such as a net shape, a mesh-like shape or a non-woven shape.

The polymer film layer which may be provided on the covering layer made of the braided wire material is provided for the purpose of obtaining a cable former having a smoother surface.
The polymer film layer can be formed, for example, by a method in which a tape-shaped or sheet-shaped film made of a polymer is wound around the outer periphery of a coating layer made of a knitted wire material without a gap, and the like. As the polymer film, for example, a film made of polyester or polyimide, and above all, a fluororesin having good slipperiness and low temperature embrittlement resistance can be preferably used. The polymer film layer and / or the wire knitted material layer may be provided between the layers when the strands of oxide superconducting wire are superposed to form a multi-layer winding structure.

The oxide superconducting cable can be formed, for example, by spirally winding a linear oxide superconducting wire around the outer periphery of the cable former, or by previously forming a strand of the spiral oxide superconducting wire. It can also be carried out by a method of forming the above and mounting it on the outer circumference of the cable former. The former is advantageous in preventing the deterioration of superconducting properties due to looseness, etc. because the oxide superconducting wire can be wound around the former with good adhesiveness, and the latter can prevent the occurrence of bending strain due to the spiral winding mounting on the former and thus the critical current. It is advantageous for forming cables with excellent superconducting properties, and avoiding the winding process on the former avoids problems such as cracking due to the winding process, and it is possible to use a former with a smaller outer diameter. This is advantageous for forming a compact cable. The oxide superconducting cable is 10 per layer.
Generally, about 15 to 15 strands are spirally wound in parallel, but the present invention is not limited to this.

The above-mentioned spiral element wire made of an oxide superconducting wire has a bending strain amount of 0.1% or less when the wire material of an oxide superconducting system having a metal sheath is spirally wound on a cable former. It can be manufactured by, for example, a method of spirally winding the heat-resistant tube around the outer circumference of the heat-resistant tube due to the difference in bending strain, and heat-treating it.

The oxide superconducting stranded wire material having a metal sheath, which is spirally wound around the outer periphery of the heat resistant tube, may be an oxide superconducting wire obtained by finishing the sintering of the superconducting layer. Generally, the oxide superconductor inside the metal sheath before sintering is in a powder state, or it is the state in which the formed superconducting layer is crushed by pre-sintering it and pressing it. . The press treatment is intended to stabilize or improve the quality, and is performed twice or more if necessary, and in that case, a heating step is usually provided between the press treatment before and after the press treatment.

The stranded wire material may be made of an oxide superconducting wire having a metal sheath or a single core material of the oxide superconducting wire, or a composite material obtained by making the single wire multicore by an appropriate method. May be. The stranded wire material has a width of 2 to 5
In general, a flat shape such as a tape shape or a rectangular shape having a thickness of about 0.1 mm and a thickness of 0.1 to 0.3 mm is used, but it has an appropriate cross-sectional shape such as a round wire shape and other polygonal shapes. May be.

The formation of the above-mentioned stranded wire material is carried out, for example, by filling an oxide superconductor powder into a metal tube, and using a suitable wire drawing means such as a die or pinch roll, a rolling means, and a swaging means to make a thin long wire. It can be performed by an arbitrary method such as a method of flattening, flattening, or forging. The metal tube is processed into a metal sheath. The multifilamentary wire can be obtained by, for example, a method of filling a plurality of wires into a metal tube and thinning or flattening the metal tube to form a composite, which is repeated a plurality of times as necessary. The particle size of the oxide superconductor powder used is 100 μm or less,
In general, it is generally 0.1 to 10 μm, and the powder can be obtained by, for example, a method of pulverizing a sintered body of an oxide superconductor.

As the material for forming the metal sheath in the oxide superconducting stranded wire material, for example, silver, gold, platinum, stainless steel, alloys containing such metals such as silver-magnesium alloys, especially silver-platinum alloys, silver -A noble metal-based material such as a high melting point alloy such as a palladium alloy is generally used, but is not limited thereto.

There is no particular limitation on the type of components forming the oxide superconductor inside the metal sheath. Examples thereof include Bi ₂ Sr ₂ CaCu ₂ O _y and Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y.
Bi-based oxide superconductors such as YBa ₂ Cu ₃ O _y and YBa ₂ C
Y-based oxide superconductors such as u ₄ O _y , Ba _- based oxide superconductors such as Ba _1-x K _x BiO ₃ , Nd _- based oxide superconductors such as Nd _2-x Ce _x CuO _y , Tl ₂ Ba Examples include Tl-based oxide superconductors such as ₂ Ca ₂ Cu ₃ O _y , other La-based oxide superconductors, Pb-based oxide superconductors, and the like.

Further, the above-mentioned components such as Bi are substituted with other rare earth elements, the components such as Sr are substituted with other alkaline earth metals, and the O components are substituted with F and the like. To be Furthermore, the thing containing the pinning center etc. is mentioned. The pinning center-containing oxide superconductor has the advantage of exhibiting a large critical current density even under a high magnetic field due to the effect of pinning the magnetic flux by the pinning center. The oxide superconductor containing the pinning center is, for example, the MPMG method (Melt
Powdering Melt Growth) and the like.

The heat-resistant tube used for forming the above-mentioned spiral element wire is intended to allow the element wire obtained after the heat treatment to be removed therefrom, and therefore, the heat-resistant tube is made of the oxide superconducting stranded wire material by the heat treatment. The tube may be made of a suitable material such as a tube made of ceramic such as alumina that does not become inseparable by adhesion, or a coated tube such as a stainless steel tube coated with ceramic. The heat-resistant tube may be formed as an assembled split mold or the like to facilitate the removal of the wire.

The winding condition of the oxide superconducting stranded wire around the heat-resistant tube is within 0.1% of the bending strain when spirally wound around the cable former to be used, preferably 0.05.
A spiral winding condition with a bending strain difference of less than 100% is preferable. If the difference in the amount of bending strain exceeds 0.1%, the superconducting property may be largely deteriorated when applied to a cable former.

The bending strain amount (ε) is calculated by the equation: ε = t
・ Can be calculated from cos ² β / 2r. Note that t is the thickness of the oxide superconducting stranded wire material, r is the radius based on the outer diameter of the heat resistant tube or cable former, and β is the angle of spiral winding with respect to the heat resistant tube or cable former.

Therefore, from the viewpoint of efficiently forming the strands while satisfying the above-mentioned difference in bending strain, a heat-resistant tube having a diameter larger than that of the cable former to be used is used, and an oxide superconducting stranded wire material is used. It is advantageous to spirally wind the with a narrow pitch. However, in the spiral winding, lap winding is avoided so that the wire materials do not adhere to each other during the heat treatment. The relationship between the pitch (P) and the angle (β) of the spiral winding is
Formula represented by ^{cosβ = 2r / √ (4r 2} + P 2/4).

In addition, in the above, since the strands can be provided as a superposed layer of two or more layers on the outer circumference of the cable former, when the strands of the second layer or more are formed,
The bending strain amount difference is determined based on the outer diameter of the cable former in which the stranded wire layer serving as the lower layer such as the first layer or the second layer is provided.

The heat treatment of the spirally wound oxide superconducting wire material with a predetermined bending strain amount on the outer periphery of the heat-resistant tube is carried out by heating the spiral superconducting wire having an oxide superconducting wire having a sintered superconducting layer. Intended for formation. Therefore, the heating conditions can be appropriately determined according to the conventional type according to the type of oxide superconductor. Generally, heat treatment is performed at a temperature of 700 to 1200 ° C.

The obtained spiral strand is removed from the heat resistant tube and mounted on a predetermined cable former to obtain an intended oxide superconducting cable. In that case, the wire may be single-phase winding or multi-layer winding. As the multi-layer winding, 20 layers or less, especially 4 to 10 layers are common, but not limited to this. When obtaining an electric power cable, it is preferable to have a power transmission capacity of 1000 A or more from the viewpoint of reducing power transmission loss. In that case, a multilayer winding structure is generally used. In the case of a multi-layer winding structure, it is advantageous to reverse the spiral direction of the wire up and down in order to improve the flexibility of the cable.

Example 1 Powder of Bi _1.7 Pb _0.3 Sr ₂ Ca ₂ Cu ₃ O _y type oxide superconductor having a particle size of 0.1 to 10 μm was filled in a silver tube having a thickness of 1.0 mm and a diameter of 7.0 mm. Then, after rolling it with a pinch roll to form a tape body with a width of 3 mm and a thickness of 0.2 mm (thickness of the superconducting portion is 100 μm), the tape body is straightened to 820 to 820.
Heat treatment was performed at 860 ° C. for about 50 hours to obtain an oxide superconducting wire.

Next, the oxide superconducting wire is covered with a wire material on the outer periphery of a spiral tube having an outer diameter of 20 mm, which is formed by spirally winding a copper plate having a width of 5 mm and a thickness of 2 mm in a cylindrical shape with a gap of 2 mm. The outer circumference of the cable former consisting of the above is spirally wound at a pitch of 50 mm to form the first layer, and then the spiral direction is reversed to form the second layer to form an oxide superconducting cable with a length of about 400 mm. Got 20 oxide superconducting wires were used for forming the first layer and the second layer, respectively.
Therefore, a total of 40 oxide superconducting wires are wound around the outer circumference of the cable former. Further, as the above-mentioned wire material knit, a netting formed by knitting a stainless wire having a diameter of 0.2 mm in a net shape at a pitch of 1 mm was used.

Example 2 A tape body was spirally wound on the outer circumference of an alumina tube having an outer diameter of 50 mm at a pitch of 5 mm and heat-treated at 820 to 860 ° C. for about 50 hours to form a spiral strand of oxide superconducting wire. Got
Next, the above-mentioned wire was removed from the alumina tube so that bending stress was not applied as much as possible, and it was attached to the outer periphery of the cable former according to Example 1 so that bending stress was not applied as much as possible. Got the cable.

Example 3 Instead of the spiral tube, a stainless corrugated tube having an outer diameter of 20 mm and a wall thickness of 1 mm having a height and a width of 5 mm at a pitch of 20 mm was used. 80 μm thickness
An oxide superconducting cable was obtained in the same manner as in Example 2 except that the cable former formed by winding the Kapton tape of 1. was used without gaps.

Comparative Example An oxide superconducting cable was obtained in the same manner as in Example 1 except that a copper pipe having a wall thickness of 2 mm and having a regular shape with no gap was used for the cable former.

Evaluation Test Flexibility The cables obtained in Examples and Comparative Examples were cut into 10 cm, and when one end was supported and a load of 10 kg was applied to the other end, the amount of bending at the other end was examined.

Superconducting Properties The cables obtained in Examples and Comparative Examples were cooled with liquid nitrogen, and the critical currents in the linear state and the bent state with a diameter of 1 m were examined.

The above results are shown in the following table.

[0039]

The oxide superconducting cable of the present invention is excellent in superconducting properties such as critical current when cooled at low temperature, exhibits good flexibility, and is excellent in laying workability.

[Brief description of drawings]

FIG. 1 is an explanatory side view of an embodiment.

FIG. 2 is an explanatory side view of another embodiment.

[Explanation of symbols]

 1: Cable former made of spiral tube 2: Cover layer made of wire knitted material 3, 4: Spiral element wire made of oxide superconducting wire 5: Cable former made of corrugated tube

Claims (2)

[Claims] 1. An oxide superconducting wire, which comprises a spiral former made of an oxide superconducting wire having a metal sheath on the outer circumference of a cable former made of a spiral tube or a corrugated tube covered with a braided wire. cable. 2. The oxide superconducting cable according to claim 1, which comprises a cable former having a polymer film layer on a coating layer of a wire rod composition.