TWI385675B - Superconductive cable - Google Patents

Description

Superconducting cable

The present invention relates to a superconducting cable. In particular, it relates to a superconducting cable that can absorb shrinkage caused by cooling of a constant conductive layer constituting a superconducting cable.

As the superconducting cable, a superconducting cable described in Fig. 4 has been proposed. This superconducting cable 100 is configured to house three cable cores 10 in the heat insulating tube 20 (for example, Patent Document 1).

The cable core 10 has, in order from its center, a core 11, a superconducting conductor layer 12, an insulating layer 15, a superconducting shield layer 16, and a protective layer 18. Typically, the core 11 is constructed of stranded wire or tubing. The conductor layer 12 is configured such that the superconducting wire is spirally wound around the core 11 in a plurality of layers. A representative superconducting wire is a belt-shaped one in which a plurality of filaments composed of an oxide superconducting material are disposed in a matrix such as a silver clad layer. In the case of the AC cable, in order to suppress the superconducting wire which is located on the outer peripheral side of the conductor layer 12, the current density is increased, and the AC current is reduced, and the winding pitch of the superconducting wires of the respective layers is also changed. The insulating layer 15 is formed by winding an insulating paper. The shield layer 16 is formed by spirally winding the same superconducting wire as the conductor layer 12 on the insulating layer 15. The protective layer 18 is made of insulating paper or the like.

Further, the heat insulating tube 20 is configured such that 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 anti-corrosion layer 23 is formed on the outer side of the heat insulating tube 20. Then, in the space formed in the core 11 (in the case of a hollow) or in the space between the inner tube 21 and the cable core 10, a refrigerant such as liquid nitrogen is filled and circulated, and the refrigerant is impregnated into the insulating layer 15 to be used. .

On the other hand, in the above-described superconducting cable, in order to prevent an accident current from flowing on the superconducting wire during a short-circuit accident or the like, it is necessary to secure a branching path of the accident current due to excessive temperature rise and damage of the same wire. Therefore, a proposal has been made to combine a constant conductive material with a constituent material of a superconducting cable. For example, Patent Document 2 discloses a normally conductive metal layer in which a shunt path that is an accident current is formed outside a conductor layer made of a superconducting wire. Further, Patent Document 3 discloses a configuration in which a stranded wire structure of an insulating coated wire material made of a constant conductive material is used as a constituent material of a core material (core), and is used as a branching path of an accident current.

[Patent Document 1] JP-A-2001-202837 (Patent Document 2) JP-A-2000-67663 (Patent Document 3) JP-A-2001-325838

However, in the above-described superconducting cable, during operation, it is cooled to a very low temperature by a refrigerant, and the constituent material of the cable is shrunk. There is therefore a need for a construction that absorbs this amount of shrinkage. However, in the constituent materials of the superconducting cable, particularly for members composed of a constant conductive material, a suitable configuration that can be used to absorb the amount of shrinkage has not been proposed.

In the configuration of a cable core having three cores, a countermeasure for absorbing the contraction amount of the cable constituent material by slackening the cable cores can be sought. However, in this case, it is necessary to increase the outer diameter of the cable by the amount of slack that the cable core has. On the other hand, in a single-core superconducting cable, a countermeasure such as a 3-core cable cannot be used. Therefore, when the shrinkage of the superconducting wire and the constant conducting wire with cooling is not sufficiently absorbed, the stress will act on the two wires. At this time, there is a case where the superconducting wire is deteriorated or the cable is shrunk, and a side pressure is applied to the heat insulating pipe at the bent portion of the cable, so that the heat insulating performance is lowered.

The present invention has been made in view of the above circumstances, and its main object is to provide a superconducting cable which can be easily configured to absorb the amount of shrinkage of a constant conductive layer due to cooling in a constituent material of a superconducting cable.

Another object of the present invention is to provide a superconducting cable which can be simply configured to absorb the shrinkage amount of the constant conductive layer caused by cooling in the constituent material of the superconducting cable, and to absorb the shrinkage amount of the superconducting layer as much as possible. .

Still another object of the present invention is to provide a superconducting cable which can be simply configured to absorb the amount of shrinkage of a constant conductive layer with cooling and to reduce the amount of use of a constant conductive material.

The superconducting cable of the present invention is a superconducting cable having a superconducting layer and a constant conducting layer disposed on at least one of the inner side and the outer side of the superconducting layer, characterized in that: the structure has a stress inside the constant conducting layer. The relaxation layer is formed by the stress relaxation layer to absorb the amount of shrinkage in the radial direction of the constant conductive layer accompanying the cooling of the refrigerant.

By providing a stress relaxation layer inside the constant conductive layer, when the constant conductive layer shrinks due to cooling, the stress relaxation layer can absorb the amount of reduction of the constant conductive layer corresponding to the shrinkage (by cooling) At least a portion of the amount by which the diameter of the constant conductive layer is reduced. Thereby, the tension generated in the normally conductive layer can be reduced. Further, by reducing the diameter of the constant conductive layer, the diameter of the superconducting layer is also reduced, and in particular, the stress caused by shrinkage during cooling of the superconducting wire wound at a short pitch can be alleviated.

Hereinafter, the configuration of the superconducting cable of the present invention will be described in detail.

The superconducting cable of the present invention is typically composed of a cable core and a heat insulating tube in which a cable core is housed. Among them, the cable core is mainly composed of a stress relaxation layer, a constant conductive layer, a superconducting conductor layer, and an insulating layer. Usually, a core composed of a cable constituent member is provided more than the cable core. In this case, for example, a stress relaxation layer and a constant conductive conductor layer are formed on the core.

The stress relieving layer is a layer for absorbing the heat shrinkage amount of the normally conductive layer. The constant conductive layer is a layer composed of a constant conductive material in the constituent material of the cable, and represents a shunt path formed by a constant conductive material in order to be divided into an accident current for short-circuiting or the like. More specifically, a part of the core may be formed of a constant conductive material.

The core is disposed inside the superconducting conductor layer in order to maintain the superconducting conductor layer in a predetermined shape. In the cable of the present invention, it is suitable to form a constant conductive layer and a stress relaxation layer on the core. For example, the stress relaxation layer and the constant conductive conductor layer are sequentially formed from the inner side, and the reduced diameter of the constant conductive conductor layer is absorbed by the stress relaxation layer.

The normally conductive layer is composed, for example, of a normally conductive wire. More specifically, a copper wire or an aluminum wire can be used for the constant conductive wire. Since the copper wire or the aluminum wire has high conductivity, it is suitable as a shunt path for overcurrent, and since it is non-magnetic, it is also preferable from the viewpoint of reducing AC loss. The cross-sectional shape of the constant conductive wire is not particularly limited, and may be a round wire or a strip wire. In the case of a constant conductive conductor layer constituting one of the cores, usually because the winding diameter is small, the round wire is relatively easy to wind. However, in the case where the constant conductive conductor layer is formed by a round wire, in order to smooth the outer peripheral surface thereof, it is preferable to provide a strip-shaped wound layer on the constant conductive conductor layer or to use a small diameter near the outer peripheral surface. Often conductive wire and so on.

It is preferable that the constant conductive layer is constructed as a twisted wire. For example, the constant conductive wire is spirally wound around the outer side of the stress relieving layer described below. By winding the normally-conductive wire in a spiral shape, the normally-conductive wire itself can be easily reduced in diameter upon cooling. Further, the twisted wire structure may be formed by twisting a plurality of core wires to form a fan-shaped conductor, or by concentrating a plurality of the fan-shaped conductors.

It is preferred that the constant conductive wire constituting the constant conductive layer is used for core insulation. The eddy current line between the normally conductive wires is cut by spirally winding the normally-conductive wire which has been insulated as a core wire, and the loss can be further reduced.

On the other hand, the stress relieving layer can be formed to have a shrinkage amount capable of absorbing at least a part of the reduced diameter of the normally-conductive layer when the cable is cooled to a very low temperature by a refrigerant. The stress relieving layer can be made to have a material and thickness at which the specified amount of shrinkage can be obtained.

The constituent material of the stress relieving layer can suitably utilize at least one of a kraft paper, a plastic tape, and a composite tape of a kraft paper and a plastic tape. The plastic tape can suitably utilize polyene, especially polypropylene. In general, kraft paper is inexpensive and has a small amount of shrinkage due to cooling, so that the buffering effect of cellulose fibers can be expected. The plastic belt will have a large amount of shrinkage due to cooling. Although the composite tape of kraft paper and polypropylene is expensive, if the thickness of the polypropylene is large, a large shrinkage amount can be secured, and the buffering effect of the cellulose fibers constituting the kraft paper can also be expected. By forming the stress relaxation layer by such a material, even when the amount of reduction of the constant conductive wire is large, it is possible to form a stress relaxation layer which does not apply excessive tension to the constant conductive wire. In addition, in kraft paper, wrinkled kraft paper or humidity-controlled kraft paper ensures a large amount of shrinkage. Further, the stress relaxation layer having a thickness capable of absorbing at least a part of the reduced diameter of the constant conductive layer can be formed by using or combining these materials alone.

The core material may also be disposed inside the stress relieving layer. The core material can easily form a stress relaxation layer, and the thickness of the stress relaxation layer can be adjusted by the diameter of the core material to adjust the absorption amount of the shrinkage amount of the constant conductive layer. The shape of the core material may be hollow or solid. Specific examples of the hollow core material include a tube material or a strip-shaped body formed into a spiral shape. It is preferable that the pipe is made into a bellows in consideration of flexibility. A specific example of the solid core material is a twisted wire structure.

The superconducting conductor layer is a conductor portion composed of a superconducting wire. For example, a conductor layer is formed by winding a superconducting wire in a spiral shape on the outer side of a core. Specific examples of the superconducting wire rod include a band-shaped one in which a plurality of filaments composed of a Bi 2223-based oxide superconductor material are disposed in a matrix of a silver clad layer or the like. The winding of the superconducting wire may be a single layer or a plurality of layers. In general, in order to suppress the bias current of the conductor layer and reduce the AC loss, the winding direction or the winding pitch of the superconducting wire can be changed in each layer or each of the plurality of layers. Further, in the case of forming a plurality of layers, an interlayer insulating layer may be provided. The interlayer insulating layer is formed by winding a composite paper such as kraft paper or a composite paper such as PPLP (registered trademark of Sumitomo Electric Industries Co., Ltd.).

The insulating layer is composed of an insulating material having an insulating endurance in response to the voltage of the conductor layer. For example, at least one of kraft paper, a plastic tape, and a composite tape of a kraft paper and a plastic tape can be suitably used.

Among the above materials, the construction of the insulating layer only by kraft paper has the lowest cost. When the composite tape is used in combination with kraft paper, the use amount of the high-priced composite tape can be reduced as compared with the case where the composite tape is formed only of the composite tape, and the cable cost can be reduced.

On the other hand, in the case where a composite tape is used for the insulating layer, it is preferable in terms of electrical characteristics. The composite tape is preferably a laminate of kraft paper and polypropylene film.

A superconducting shielding layer may also be disposed outside the insulating layer. The superconducting shield layer cancels the magnetic field generated by the superconducting conductor layer by inducing a current of substantially the same size and opposite direction to the superconducting conductor layer to prevent the magnetic field from being leaked to the outside. The superconducting shield layer is also spirally wound around the same superconducting wire as the superconducting conductor layer. Generally, in the same manner as the superconducting conductor layer, in order to suppress the bias current, the winding direction or the winding pitch of the superconducting wire constituting the superconducting shield layer may be changed in each layer or each of the specified plurality of layers.

On the other hand, the normally-conductive shielding layer is a shielding layer composed of, for example, a constant conductive material disposed close to the superconducting shielding layer. In the usual cable operation, as described above, a current of substantially the same size and opposite direction to the superconducting conductor layer is induced on the superconducting shield layer. On the other hand, in the case where an overcurrent flows to the superconducting conductor layer due to a short-circuit accident or the like, and an overcurrent flows in the superconducting shield layer in response thereto, the normally-conducting shield layer functions as a branching path thereof. It is used to suppress the damage of the superconducting shielding layer caused by excessive temperature rise.

The constant conductive shield layer is preferably composed of a common conductive wire which is the same as the normal conductive conductor layer, and is preferably wound in a spiral shape. In particular, it is preferred that the normally-conductive shielding layer be formed of a strip-shaped electrically conductive wire. Since the winding outer diameter of the constant conductive shielding layer is larger than that of the constant conductive conductor layer, it is also easy to be wound in the strip-shaped wire, and the normally-conductive shielding layer having a desired sectional area can be formed thinner. In addition, the distance between the strip wires is very small compared to the round wires, and the ratio (area occupancy) of the constant conductive wires occupied by the cross section of the constant conductive layer can be increased.

As described above, the amount of reduction of the constant conductive shielding layer is preferably such that it can be absorbed by the stress relieving layer formed on the core. That is, when the core is reduced in diameter, the insulating layer becomes easy to reduce in diameter and contributes to shrinkage of the normally conductive shielding layer. In addition to this, the insulator itself can also be utilized as a stress relieving layer for absorbing the reduced diameter of the normally conductive shielding layer. When the insulator itself is used as the stress relaxation layer, the diameter of the cable core is reduced.

Further, it is preferable to provide a protective layer on the outermost circumference of the cable core. The protective layer has a function of mechanically protecting the outer conductor layer while being insulated from the heat insulating tube. The material of the protective layer can be made of insulating paper or plastic tape such as kraft paper.

On the other hand, the heat insulating pipe may have any structure as long as it can maintain the heat insulating structure of the refrigerant. For example, a heat insulating material may be disposed between the double pipes of the double structure composed of the outer pipe and the inner pipe, and the inner pipe and the outer pipe may be evacuated. Usually, a super-insulating material in which a metal foil and a plastic mesh are laminated is disposed between the inner tube and the outer tube. At least a conductor layer is housed in the inner tube, and a refrigerant such as liquid nitrogen that cools the conductor layer is filled.

This refrigerant can maintain the superconducting wire in a superconducting state. At present, it can be considered that the use of liquid nitrogen for the refrigerant is most practical. In addition to this, it is also conceivable to use liquid helium, liquid hydrogen, and the like. Especially in the case of liquid nitrogen, it is a liquid which does not swell the polypropylene, and even when the insulating layer is formed by the composite of polypropylene, it can constitute a DC withstand voltage characteristic, and the Imp. pressure characteristic is excellent. Superconducting cable.

In addition, in the above-described cable of the present invention, it is preferable to provide the following configurations individually or in combination.

(1) The winding pitch of the constant conductive wire is 4 to 6 times the winding diameter.

The winding diameter refers to the diameter of the layer of the normally-conductive wire material wound, that is, the inner diameter of the layer composed of the normally-conductive wire. By defining the ratio of the winding pitch to the winding diameter as described above, it is possible to reduce the short pitch of the amount of shrinkage when the constant conductive wire is shrunk by cooling, and it is possible to suppress the use of the constant conductive wire. Winding pitch.

When the winding pitch of the constant conductive wire is reduced, the amount of shrinkage when the constant conductive wire is shrunk by cooling and the amount of absorption by the stress relieving layer are also reduced, so that the stress relieving layer can be easily formed. However, when the winding pitch is reduced, the use of the constant conductive wire is increased, and the cost is also increased. Therefore, it is important to select a winding pitch which can suppress the increase in the amount of use of the constant conductive wire as much as possible. Here, by defining the ratio of the winding pitch to the winding diameter as described above, it is possible to reduce the short pitch of the amount of reduction in diameter when the constant conductive wire is shrunk by cooling, and to suppress the use of the constant conductive wire. The amount of spacing is used to form a superconducting cable.

The preferred winding pitch of such a constant conductive wire can be obtained by trial or actual measurement as follows. First, the relationship between the ratio of the winding pitch of the constant conductive wire constituting the constant conductive layer to the winding diameter "(pitch/diameter) ratio" and the amount of reduction of the constant conductive wire during cooling was investigated. Next, the relationship between "(pitch/diameter) ratio" and the amount of use of a constant conductive wire was investigated. Then, the winding pitch and the winding diameter of the normally-conductive conductive wire in which the amount of the normal conductive wire is reduced to a predetermined value or less and the amount of the normally-conductive wire used is equal to or less than a predetermined value can be selected.

Further, in the case where the normally-conductive layer (normally-conducting conductor layer or constant-conducting shielding layer) is formed of a plurality of layers of normally-conducting wires, the winding direction or volume of the constant-conducting wires can be changed in each layer or each of the designated plurality of layers. The pitch is preferably preferred. Thereby, the bias current of the constant conductive layer can be suppressed. Even in the case where the winding pitch of the constant conductive wire is changed as such, the winding pitch of the normally-conductive wire is changed in the range of 4 to 6 times the winding diameter from the viewpoint of the amount of reduction in diameter and the amount of wire used. Preferably.

(2) Formation of Semiconductor Layer For example, a semiconductor layer may be formed between at least one of the inner and outer circumferences of the insulating layer, that is, between the superconducting conductive layer and the insulating layer, and between the insulating layer and the superconducting shield layer. The electrical performance can be effectively stabilized by forming the inner semiconductor layer of the former and the outer semiconductor layer of the latter. The semiconductor layer can be formed by winding carbon paper or the like.

(3) A Bi-based oxide superconducting wire produced by a pressure calcination method is used.

In the case where the superconducting wire is spirally wound to form a superconducting layer (superconducting conductor layer or superconducting shielding layer), generally, a plurality of different pitches are combined to wind the superconducting wire from the viewpoint of suppressing the drift. . On the other hand, if the winding diameter of the superconducting wire is the same, the smaller the winding pitch, the larger the amount of reduction. Therefore, according to the absorption amount of the stress relaxation layer, it is required that the superconducting wire having a large winding pitch allows the stress accompanying the contraction. In this case, if the superconducting wire is a wire having excellent tensile strength, a sufficiently practical superconducting cable can be constructed. One of the means for obtaining the superconducting wire having excellent tensile strength is a method of producing a superconducting wire by a press calcination method.

The press calcination method is a method in which a pressure in a gas is applied to a power in tube method for producing a superconducting wire, and an external pressure is applied to the wire in an isostatic manner. By this pressurization, the decrease in the filament density of the wire can be suppressed, and a super-conductive wire having a high tensile strength can be obtained. In the case of the cable of the present invention, although the stress relaxation layer absorbs the reduced diameter of the constant conductive layer to alleviate the effect of the stress on the superconducting wire, even in this case, stress, especially tensile stress, is considered to act on the superconducting wire. Wire. Therefore, in the case of a superconducting wire having excellent tensile strength, tension can be allowed to act on the superconducting wire, and deterioration of the superconducting wire can be effectively suppressed.

In particular, in the case where the superconducting layer is formed of superconducting wires having different winding pitches, it is preferable to apply the superconducting wire manufactured by the pressure calcining method to the superconducting wire having a large winding pitch. . Since the superconducting wire having a large winding pitch is larger than the diameter of the superconducting wire having a small winding pitch, when the amount of the reduced diameter is not well absorbed, the tension acts on the superconducting wire. Therefore, if the superconducting wire obtained by the pressure calcination method is applied to a superconducting wire which is easy to apply tension, deterioration of the superconducting wire can be effectively suppressed.

As the gas during pressurization by the press calcination method, a mixed gas of an inert gas and oxygen gas is preferred, and a pressurization pressure of 15 to 30 MPa is preferred. This press-calcining method is disclosed, for example, in "Development of lanthanide superconducting wire rods" Yamazaki Koto, "SEI Technology Watch" No. 164, 36-41, March 2004.

(4) A reinforcing layer for reinforcing the tensile strength of the superconducting wire is provided.

As described above, the superconducting wire preferably has a higher tensile strength and allows stress to act on the superconducting wire. However, by providing a reinforcing layer on the superconducting wire, a tensile superconducting wire can be formed. The reinforcing layer may be, for example, a stainless steel tape attached to a superconducting wire or a resin coating such as varnish applied to the superconducting wire.

(5) The crimp layer and the buffer layer may be provided to form a rolled layer on the outer side of the superconducting layer (superconducting conductor layer or superconducting shield layer). By forming a rolled layer on the outer side of the superconducting layer, it is expected that the superconducting layer is biased toward the inside. By this tightening effect, the diameter of the superconducting layer can be smoothly slid. The material of the crimp layer is a one that can produce a specified tightening force on the superconducting layer. For example, a metal strip, especially a copper strip or the like can be suitably used.

In the case of using this rolled layer, it is preferred to intervene the buffer layer between the rolled layer and the superconducting layer. In the case where a metal strip is used for the rolled layer, generally, the superconducting wire is also made of a metal such as silver, so that the rolled layer and the superconducting layer form a metal contact with each other, and there is a possibility that the superconducting wire is damaged. Therefore, if the buffer layer is interposed between the two layers, direct contact of the metals with each other can be avoided, and damage of the superconducting wire can be prevented. The specific material of the buffer layer can be suitably made of insulating paper or carbon paper.

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

(1) by providing a stress relaxation layer inside the constant conductive layer, and when the constant conductive wire is shrunk by cooling, the stress relaxation layer can absorb at least the amount of the reduced diameter of the constant conductive layer due to the shrinkage. portion. Thereby, especially the stress acting on the superconducting wire wound at a short pitch can be alleviated or eliminated.

(2) By absorbing at least a part of the amount of reduction of the constant conductive layer by the stress relieving layer, the tension acting on the cable core can be reduced, and the stress applied to the cable end can be reduced. Along with this, the design of the cable terminal can be easily performed. Further, by reducing the tension acting on the cable core, it is possible to suppress a decrease in the heat insulating performance of the heat insulating layer due to the side pressure of the bent portion of the cable.

(3) The cable core itself is provided with a mechanism capable of absorbing heat shrinkage, and the multi-core superconducting cable naturally does not need to be said, even in a single-core superconducting cable which is conventionally considered to be difficult to provide an absorbing mechanism, it can absorb a constant conductive wire. And at least a portion of the amount of shrinkage of the superconducting wire. In the case of a multi-core cable such as a 3-core cable, it is possible to reduce the slack and the outer diameter of the cable.

(4) By making the winding pitch of the constant conductive wire 4 to 6 times the winding diameter, it is possible to absorb the reduced diameter of the constant conductive wire during cooling with a simple configuration, and it is also possible to minimize the constant conductive wire. The amount of superconducting cable used.

Hereinafter, embodiments of the present invention will be described.

(First embodiment)

[Overall construction]

As shown in Fig. 1, the AC superconducting cable 100 of the present invention comprises a one-core cable core 10 and a heat insulating tube 20 for accommodating the cable core 10.

[cable core]

The cable core 10 has a core 11, a superconducting conductor layer 12, a buffer layer 13, a rolled layer 14, an insulating layer 15, a superconducting shield layer 16, a constant conductive shielding layer 17, and a protective layer 18 in this order from the center.

<core>

The core 11 is a member for forming a superconducting conductor layer 12 made of a superconducting wire as a core, and has a core material 11A, a stress relieving layer 11B, and a constant conductive conductor layer 11C in this order from the center. Here, the core material 11A is a spiral steel strip, and an insulating tape is wound around the core material 11A to serve as the stress relieving layer 11B, and a constant conductive wire is wound around the stress relieving layer 11B to serve as the constant conductive conductor layer 11C.

The core material 11A is a member which is used as a core for forming the stress relieving layer 11B, and has a structure in which a SUS316 steel strip having a width of 6 mm and a thickness of 0.8 mm is spirally wound.

The stress relieving layer 11B is made of a material and a thickness that can absorb the amount of reduction in shrinkage when the normally conducting conductive layer 11C is thermally contracted. More specifically, the insulating tape is a composite tape PPLP (registered trademark) manufactured by Sumitomo Electric Industries Co., Ltd. which is laminated with kraft paper and a polypropylene film. The ratio of the thickness of the polypropylene film to the thickness of the composite tape as a whole of the PPLP was 60%.

In addition, the constant conductive conductor layer 11C is a shunt path for causing an accident current in order to suppress an electric current from flowing through the superconducting conductor layer 12 and causing damage to the superconducting conductor layer 12 in order to suppress a short-circuit accident or the like. Here, the copper wire coated with polyvinyl fluoride is spirally wound around the stress relaxation layer 11B. The constant conductive conductor layer 11C is composed of two layers, and the copper wire on the inner peripheral side has a diameter of 1.5 mm, and the copper wire on the outer peripheral side has a diameter of 1.1 mm. The winding direction of each layer of the constant conductive conductor layer 11C is sequentially S-Z from the inner side.

<Superconducting Conductive Layer>

The superconducting conductor layer 12 is a Bi2223-based Ag-Mn clad strip wire having a thickness of 0.24 mm and a width of 3.8 mm. This strip wire is produced by a pressure calcination method. This strip-shaped wire is wound on the core 11 (normally conductive conductor layer 11C) in multiple layers to constitute the superconducting conductor layer 12. Here, four layers of superconducting wires were wound. The winding direction of each layer is S-S-Z-Z in order from the inner side.

<buffer layer and crimp layer>

A buffer layer 13 is formed on the superconducting conductor layer 12, and a rolled layer 14 is formed thereon. The buffer layer 13 is formed by winding a plurality of layers of kraft paper on the superconducting conductor layer 12, and the crimp layer 14 is formed by winding a copper strip. The buffer layer 13 is used to avoid contact between the superconducting conductor layer 12 and the metal caused by the coiled layer 14, and the crimping layer 14 presses the superconducting conductor layer 12 inwardly via the buffer layer 13 to smoothly cool the layer. The diameter of the superconducting conductive layer 12 is reduced, and the diameter of the constant conductive conductor layer 11C is further reduced.

<insulation layer>

An insulating layer 15 is formed on the rolled layer 14. This insulating layer 15 has a function of electrically insulating the current flowing through the conductor layer 12. Here, the insulating layer 15 is composed of PPLP. Further, the insulating layer 15 has a function as an external stress relieving layer for absorbing a reduced amount of cooling of the normally-conductive shielding layer 17 to be described later. By using the insulating layer 15 itself as the external stress relieving layer, it is not necessary to form the external stress relieving layer individually, and the increase in the outer diameter of the cable core can be suppressed.

Further, although not shown, an inner semiconductor layer is formed on the inner peripheral side of the insulating layer 15, and an outer semiconductor layer is formed on the outer peripheral side. Any of the semiconductor layers is formed by winding of carbon paper.

<Superconducting Shielding Layer>

A superconducting shield layer 16 is provided on the outer side of the insulating layer 15. The superconducting shielding layer 16 is offset from the magnetic field generated by the superconducting conductor layer 12 by sensing the current of the same size and opposite direction to the superconducting conductor layer 12 during the operation of the cable to prevent the magnetic field from being leaked to external. Here, it is composed of the same superconducting wire as the superconducting conductor layer 12. More specifically, it is composed of two layers, and the winding direction of each layer is S-S.

<normal conductive shielding layer>

Next, a constant conductive shield layer 17 is formed on the superconducting shield layer 16. The constant conductive shield layer 17 is a shunt path for the accident current in order to suppress the occurrence of a short-circuit accident or the like, and the current is induced in the superconducting shield layer 16 to damage the superconducting shield layer 16. Here, the copper wire coated with polyvinyl fluoride is spirally wound around the superconducting shield layer 16. This constant conductive shielding layer 17 is composed of two layers, and a strip-shaped copper wire is used. The winding direction of each layer of the constant conductive shielding layer 17 is sequentially S-Z from the inner side.

<protection layer>

A protective layer 18 made of an insulating material is disposed on the outer side of the constant conductive shield layer 17. Here, the protective layer 18 is formed by winding of kraft paper. By the protective layer 18, the normally conductive shielding layer 17 is mechanically protected, and the insulation from the heat insulating tube (the inner tube 21) is obtained, and the shunting of the induced current flowing to the heat insulating tube 20 can be prevented.

[insulation tube]

The heat insulating tube 20 is composed of a double tube including an inner tube 21 and an outer tube 22, and constitutes a vacuum heat insulating layer between the inner and outer tubes 21 and 22. A so-called super insulating material made of a laminated plastic mesh and a gold foil 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 flow path of the refrigerant. Further, the anticorrosive layer 23 may be formed of polyvinyl chloride or the like on the outer circumference of the heat insulating tube 20 as needed.

(Trial example)

Next, in the production of the above-described superconducting cable, the following calculation is performed in such a manner that the amount of reduction of the constant conductive wire can be reduced while reducing the amount of the constant conductive wire.

First, the relationship between the ratio of the winding pitch of the constant conductive wire constituting the constant conductive layer to the winding diameter "(pitch/diameter) ratio" and the amount of reduction of the normal conductive wire was investigated. Here, the winding diameter is three types of 20 mm Φ, 30 mm Φ, and 40 mm Φ, and the linear expansion coefficient of each material is used to calculate the "(pitch/diameter) ratio" of each case and the cooling by the operation. The amount of reduction in the case where the constant conductive wire shrinks by 0.3%. This result is shown in the graph of Fig. 2.

As shown in the graph, it can be seen that if the "pitch/diameter" ratio is the same, the smaller the winding diameter, the smaller the amount of reduction. In addition, it is understood that if the "winding diameter/diameter" ratio is smaller than the same winding diameter, the amount of reduction is small. From this result, it is understood that the short-pitch configuration is selected, and the amount of shrinkage which should be absorbed can be small.

Next, the relationship between "(pitch/diameter) ratio" and the amount of use of a constant conductive wire was investigated. Here, when the constant conductive wire is placed along the longitudinal direction of the winding target, that is, the amount of the normal conductive wire used in the case is set to 1.0, and the "(pitch/diameter) ratio is changed" In the case, the relative value shows how the amount of the constant conductive wire is changed. This result is shown in the graph of Figure 3.

As shown in the graph, it can be seen that when the "pitch/diameter" ratio is about 6.0, the amount of the constant conductive wire is not extremely increased, but the amount of the constant conductive wire is increased from less than 4.0. .

From the above two trial results, it can be seen that if the amount of shrinkage of the constant conductive wire during cooling is easily absorbed, and the amount of the commonly used conductive wire is small, the "(pitch/diameter) ratio" is 4.0 to 6.0. The degree is better.

(industrial availability)

The superconducting cable of the present invention can be used as a means of power transmission. In particular, it can be suitably used as a single-core AC power transmission means.

100. . . Superconducting cable

10. . . Cable core

11. . . Core

11A. . . Core

11B. . . Stress relaxation layer

11C. . . Constant conductive conductor layer

12. . . Superconducting conductor layer

13. . . The buffer layer

14. . . Compression layer

15. . . Insulation

16. . . Superconducting shield

17. . . Constant conducting shield

18. . . The protective layer

20. . . Insulation tube

twenty one. . . Inner tube

twenty two. . . Outer tube

twenty three. . . Anti-corrosion layer

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

Fig. 2 is a graph showing the relationship between "(pitch/diameter) ratio" and the amount of shrinkage when the constant conductive wire is cooled.

Fig. 3 is a graph showing the relationship between "(pitch/diameter) ratio" and the amount of use of a constant conductive wire.

Figure 4 is a cross-sectional view of a conventional superconducting cable.

10. . . Cable core

11. . . Core

11A. . . Core

11B. . . Stress relaxation layer

11C. . . Constant conductive conductor layer

12. . . Superconducting conductor layer

13. . . The buffer layer

14. . . Compression layer

15. . . Insulation

16. . . Superconducting shield

17. . . Constant conducting shield

18. . . The protective layer

20. . . Insulation tube

twenty one. . . Inner tube

twenty two. . . Outer tube

twenty three. . . Anti-corrosion layer

100. . . Superconducting cable

Claims (8)

A superconducting cable is a superconducting cable having a superconducting layer and a constant conducting layer disposed on at least one of an inner side and an outer side of the superconducting layer, characterized in that: a stress relieving layer is disposed inside the constant conducting layer, and the structure is The stress relieving layer is thereby absorbed to absorb at least a portion of the amount of shrinkage in the radial direction of the normally conducting layer with cooling of the refrigerant. The superconducting cable of claim 1, wherein the constant conductive layer is composed of a normally conductive wire wound in a spiral shape. The superconducting cable of claim 2, wherein the winding distance of the constant conductive wire is 4 to 6 times the winding diameter. The superconducting cable according to any one of claims 1 to 3, wherein the superconducting cable has a core, a superconducting conductor layer formed on the outer side of the core as a superconducting layer, and formed in the super An insulating layer on the outer side of the conductive conductor layer, the core having a constant conductive layer and a stress relaxation layer. The superconducting cable of claim 4, wherein the superconducting cable further comprises: a superconducting shielding layer formed on the outer side of the insulating layer as a superconducting layer; and being formed on the outer side of the superconducting shielding layer as a constant conducting layer. Constantly conductive shielding layer. The superconducting cable according to any one of claims 1 to 3, wherein the superconducting layer is composed of a superconducting wire which is oxidized by Bi-based oxidation calcination. Superconducting wire. The superconducting cable according to any one of claims 1 to 3, wherein the superconducting layer is composed of a superconducting wire, and the superconducting wire is provided with a reinforcing layer for reinforcing the tensile strength thereof. The superconducting cable according to any one of claims 1 to 3, wherein the stress buffer layer is composed of at least one of kraft paper, a plastic tape, and a composite tape of kraft paper and a plastic tape.