JP4716160B2 - 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 buckling of the superconducting layer that is likely to occur when the superconducting layer and the outer peripheral layer located outside thereof are relatively displaced in the longitudinal direction.

  As a superconducting cable, a single-core superconducting cable shown in FIG. 4 has been proposed. FIG. 4 is a cross-sectional view of this superconducting cable. The superconducting cable 100 has a configuration in which one cable core 110 is housed in a heat insulating tube 120.

  The cable core 110 includes a former 10, a conductor layer 30, an insulating layer 60, a shield layer 70, and a protective layer 80 in order from the center. The conductor layer 30 is formed by spirally winding a superconducting wire on the former 10 in multiple layers. Usually, the superconducting wire is a tape-like one in which a plurality of filaments made of an oxide superconducting material are arranged in a matrix such as a silver sheath. The insulating layer 60 is configured by winding insulating paper such as semi-synthetic insulating paper. The shield layer 70 is configured by spirally winding a superconducting wire similar to the conductor layer 30 on the insulating layer 60. For the protective layer 80, insulating paper or the like is used.

  On the other hand, the heat insulating tube 120 has a structure in which a heat insulating material (not shown) is disposed between the double tubes composed of the inner tube 121 and the outer tube 122, and the inside of the double tube is evacuated. An anticorrosion layer 130 is formed outside the heat insulating tube 120. The space formed between the former 10 and the inner tube 121 and the core 110 is filled and circulated with a refrigerant such as liquid nitrogen, and the insulating layer 60 is impregnated with the refrigerant to be used.

  As an intermediate connection part of such a superconducting cable, the technique of FIG. 5 is known (as a similar technique, for example, Patent Document 1). In this connection portion, first, the respective layers are stripped off at the end portions of the cables to be connected to each other to expose the conductor layer 30 and the former 10 stepwise, and the formers 10 are inserted into the connection sleeve 210 and crimped. The connection sleeve 210 is a metal cylinder having a former insertion hole at an intermediate portion and a conductor insertion hole having an inner diameter larger than that of the former insertion hole at both ends. The crimping connection of the former 10 is performed by compressing the former insertion hole, and the conductor layer 30 exposed in stages is not inserted into the former insertion hole but is inserted into the conductor insertion hole with a gap. The reason why the conductor layer 30 is not crimped is that the superconducting characteristics deteriorate when the superconducting wire is compressed. Therefore, the conductor layer 30 and the connection sleeve 210 are connected by pouring the solder 220 into the gap between the conductor insertion hole and the conductor layer 30.

  Further, in order to perform this soldering operation, a space S is usually provided between the end of the connection sleeve 210 and the end of the insulating layer 60. For the insulating layer 60 of the superconducting cable, for example, semi-synthetic paper laminated with polypropylene and insulating paper is used. This is because the end of the insulating layer 60 is in contact with or close to the solder 220 without the spacing S described above, and the polypropylene melts due to the heat of dissolution of the solder 220, thereby degrading the insulating performance.

  When the connection between the former 10 and the conductor layer 30 by the connection sleeve 210 is completed, the connection sleeve 210 is halfway from the vicinity of the outer periphery of the connection sleeve 210, that is, from the vicinity of the insulating layer end of one cable to the vicinity of the insulating layer end of the other cable. An insulating tape such as synthetic paper is wound to form the reinforcing insulating layer 230.

Japanese Patent Laid-Open No. 11-121059 (FIG. 9)

  However, in the above superconducting cable, there is a problem that when the connecting portion is formed, the superconducting wire may be buckled due to thermal expansion and contraction of the cable.

  The superconducting cable shrinks when the superconducting wire is cooled with the refrigerant, and stretches when returning to room temperature. In that case, since each layer which comprises a cable differs in the constituent material and is comprised by radial direction discontinuity, the relative movement to a longitudinal direction may arise between each layer. For example, when a superconducting cable is cooled, the superconducting wire that is wound in a spiral shape and constitutes the conductor layer contracts and is subjected to tensile stress, and moves in a direction in which the twist is tightened, that is, in a direction in which the diameter decreases. Conversely, when the superconducting cable is returned to room temperature, the superconducting wire moves in the direction of loosening. On the other hand, the insulating layer formed outside the conductor layer has a smaller degree of expansion and contraction due to temperature change than the superconducting wire. For this reason, as the superconducting cable is repeatedly cooled to a cryogenic temperature and returned to room temperature, a relative movement in the longitudinal direction gradually occurs between the conductor layer and the insulating layer.

  In particular, in the connection portion of the superconducting cable, in FIG. 6, movement (movement from the broken line to the solid line) such that the end of the insulating layer 60 approaches the connection sleeve 210 side, or movement in the opposite direction may occur. is there. In the process, the interval S (see FIG. 5) provided between the end of the connection sleeve 210 and the end of the insulating layer 60 repeatedly narrows and widens, and the gap between the superconducting layer and the insulating layer is repeated. The superconducting wire positioned at the interval S may buckle due to the formation of a space or wrinkling of the superconducting wire. As a result, it is expected that the electrical / mechanical characteristics of the superconducting wire are deteriorated or that the superconducting wire is broken in the worst case.

  The present invention has been made in view of the above circumstances, and the main purpose of the present invention is to provide a seat for a superconducting layer that is likely to occur when a superconducting layer such as a conductor layer and an outer peripheral layer located outside the conductor layer move relatively in the longitudinal direction. The object is to provide a superconducting cable capable of suppressing bending.

  The present invention achieves the above object by providing a reinforcing layer that suppresses buckling by pressing the superconducting layer immediately above the superconducting layer.

  That is, the superconducting cable of the present invention is a superconducting cable having a superconducting layer, and is characterized in that a reinforcing layer for preventing buckling is provided immediately above the superconducting layer.

  Even if relative movement between the outer peripheral layer (for example, the insulating layer) located outside the superconducting layer and the superconducting layer occurs by pressing the superconducting layer with the reinforcing layer, the superconducting layer is directly below the inner peripheral layer by the reinforcing layer. It is pressed to the side. Therefore, the space in which the superconducting layer behaves in the radial direction is small, and the superconducting layer can be prevented from being bent due to floating from the inner peripheral layer or wrinkles on the inner peripheral layer.

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

  The superconducting cable of the present invention typically has a basic configuration including a superconducting layer, a reinforcing layer, an insulating layer, and a heat insulating tube. In addition, a former and a shield layer are usually provided. In the present invention, the superconducting layer is a layer formed using a superconducting wire, and is typically a conductor layer. Further, when the shield layer is also composed of a superconducting wire, the shield layer is also included in the superconducting layer.

  In the above cable, the former retains the conductor layer in a predetermined shape, and a pipe-shaped or stranded wire structure can be used. The material is preferably a nonmagnetic metal material such as copper or aluminum. When the former is pipe-shaped, the inside of the former can be a refrigerant flow path.

  The conductor layer is formed by, for example, winding a wire made of a superconducting material in a spiral shape on a former. A specific example of the superconducting wire is a tape-like one in which a plurality of filaments made of Bi2223 oxide superconducting material are arranged in a matrix such as a silver sheath. The winding of the superconducting wire may be a single layer or a multilayer. In the case of a multilayer structure, an interlayer insulating layer may be provided. The interlayer insulating layer may be provided by winding insulating paper such as kraft paper or semi-synthetic insulating paper such as PPLP (registered trademark, manufactured by Sumitomo Electric Industries, Ltd.).

  The reinforcing layer is provided immediately above the superconducting layer. In other words, (1) just above the conductor layer (conductor reinforcement layer), (2) just above the shield layer (shield reinforcement layer), (3) providing a reinforcement layer directly above each of the conductor layer and shield layer It is done. In particular, it is preferable to provide a reinforcing layer immediately above the conductor layer. Usually, the shield layers of the cables connected to each other are often connected by a braided material having excellent flexibility, and the relative movement between the shield layer and its outer peripheral layer itself is small. The possibility of buckling is low. On the other hand, since the conductor layers are connected by a connection sleeve that is substantially inflexible, if there is a relative movement between the conductor layer and the outer peripheral layer, the conductor layers are likely to buckle. Even if the shield layer has a low possibility of buckling, it may be damaged due to relative movement with the outer peripheral layer. Therefore, it is preferable to provide a reinforcing layer.

  The reinforcing layer is preferably formed by winding a tape material on the superconducting layer. The superconducting layer is pressed against the inner peripheral side by winding the tape material, and the buckling of the superconducting layer is effectively suppressed. In general, superconducting wires are wound at a relatively large pitch because they are intended to allow current to flow effectively. On the other hand, if the reinforcing layer that holds the superconducting wire is formed by winding the tape material at a pitch equal to or less than the winding pitch of the superconducting wire in consideration of mechanical properties such as bending, the superconducting wire can be effectively pressed down. it can. More preferably, the reinforcing layer may be formed by winding the tape material at the same pitch as the insulating layer. If the reinforcing layer is formed at the same pitch as the insulating layer, the reinforcing layer (the superconducting layer wound around the reinforcing layer) and the insulating layer can be moved in synchronization with each other, and their relative movement is reduced. can do.

  Further, the winding method of the tape material is preferably aligned winding. The combined winding is a winding method in which two different tape materials appear alternately on the surface. When forming the connection portion of the superconducting cable, the reinforcing layer is cut at the end of the cable. If the reinforcing layer is formed by winding together, one of the two different tapes is pressed by the other tape, so that the reinforcing layer can be prevented from coming off from the cut end.

  Either a conductive material or an insulating material can be used as the material of the reinforcing layer. Any material having sufficient tensile strength to press the superconducting layer may be used. Specifically, metal tapes such as copper tape, aluminum tape, and stainless steel tape can be suitably used, and various plastic tapes and paper tapes can also be used. In particular, it is also preferable to use an insulating material for the shield reinforcing layer.

  The insulating layer is preferably formed by winding semi-synthetic paper such as PPLP (registered trademark of Sumitomo Electric Industries) laminated with polypropylene and kraft paper, or insulating paper such as kraft paper. A semiconductive layer may be formed on at least one of the inner and outer circumferences of the insulating layer, that is, between the conductor reinforcing layer and the insulating layer, or between the insulating layer and the shield layer. By forming the former inner semiconductive layer and the latter outer semiconductive layer, adhesion between the conductor layer and the insulating layer or between the insulating layer and the shield layer is improved, and deterioration due to the occurrence of partial discharge, etc. Suppress.

  Moreover, it is preferable to provide a shield layer outside the insulating layer. By providing the shield layer, leakage of the alternating magnetic field flowing through the conductor layer to the outside can be suppressed. The shield layer may be made of a conductive material, and is preferably formed by winding a superconducting wire similar to the conductor layer around the outside of the insulating layer.

  In addition, a cushion layer may be interposed between the former and the conductor layer. The cushion layer avoids direct contact between metals between the former and the superconducting wire, and prevents damage to the superconducting wire. In particular, when the former has a stranded wire structure, the cushion layer also has a function of making the former surface smoother. As a specific material of the cushion layer, insulating paper or carbon paper can be suitably used.

  It is also desirable to interpose a cushion layer between the superconducting layer and the reinforcing layer. That is, a cushion layer is provided between at least one of the conductor layer and the reinforcing layer and between the shield layer and the reinforcing layer. The insulating paper and carbon paper mentioned above can be used also for the cushion layer here. This cushion layer reduces the possibility of voids between the superconducting layer and the reinforcing layer to improve electrical characteristics, and also reduces the possibility of damage due to direct contact between the superconducting layer and the reinforcing layer. The characteristics can be improved.

  On the other hand, the heat insulation pipe | tube has the structure which arrange | positions a heat insulating material between the heat insulation pipe | tubes of the double structure which consists of an outer pipe | tube and an inner pipe | tube, and evacuates between an inner pipe | tube and an outer pipe | tube. The inner tube contains at least a conductor layer and is filled with a refrigerant such as liquid nitrogen that cools the superconducting layer.

  The superconducting cable of the present invention can be applied to any of multi-core cables as well as single-core cables. In particular, application to a single-core cable is suitable. Usually, a multi-core cable, such as a three-core cable, is configured such that the cores of each core are gently twisted and the core itself behaves by contraction during cooling. Therefore, the problem of buckling of the superconducting layer due to relative movement between the superconducting layer and the outer peripheral layer is more likely to occur in the single-core cable.

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

  (1) Since the superconducting layer is pressed to the inner peripheral layer side immediately below it by the reinforcing layer, even if relative movement between the outer peripheral layer (eg, insulating layer) located outside the superconducting layer and the superconducting layer occurs The space in which the superconducting layer behaves in the radial direction can be reduced. Therefore, the superconducting layer can be prevented from floating from the inner peripheral layer or wrinkled on the inner peripheral layer, and buckling of the superconducting layer can be prevented.

  (2) By constituting the reinforcing layer by the combined winding with the tape material, it is possible to suppress the reinforcing layer from being separated from the end of the reinforcing layer cut at the time of forming the connecting portion.

  (3) By interposing a cushion layer between the superconducting layer and the reinforcing layer, it is possible to suppress damage to the superconducting layer due to direct contact with the reinforcing layer, and a void is generated between the superconducting layer and the reinforcing layer. It is possible to prevent deterioration of electrical characteristics due to

  Embodiments of the present invention will be described below.

Example 1
As an example of the superconducting cable of the present invention, an AC single-core superconducting cable was produced. FIG. 1 shows a cross-sectional view thereof, and FIG.

  As shown in FIG. 1, the cable 100 includes a single core 110 and a heat insulating tube 120 that houses the core 110.

  As shown in FIG. 2, the core 110 includes, in order from the center, the former 10, the cushion layer 21, the conductor layer 30, the conductor reinforcing layer 41, the internal semiconductive layer 51, the insulating layer 60, the external semiconductive layer 52, and the shield layer 70. The shield reinforcing layer 42 and the protective layer 80 are provided. Of these layers, superconducting wires are used for the conductor layer 30 and the shield layer 70. The superconducting wire constituting the core 110 is maintained in a superconducting state by circulating a refrigerant (for example, liquid nitrogen) in the space between the heat insulating pipe and the core.

  For the former 10, a plurality of copper wires twisted together was used. By using a former with a stranded wire structure, it is possible to simultaneously reduce AC loss and suppress temperature rise due to overcurrent. Also, in this example, the outer strand is made thinner than the central strand, and the unevenness due to the groove is made as small as possible, which appears on the outer circumferential surface of the former.

  A cushion layer 21 is provided on the former 10. The cushion layer 21 was formed by winding carbon paper around the former 10 in a spiral shape. By this cushion layer 21, the surface of the former 10 can be smoothed, and damage due to direct contact between the former 21 and the conductor layer 30 can be reduced.

  For the conductor layer 30, a Bi2223-based Ag-Mn sheath tape wire having a thickness of 0.24 mm and a width of 3.8 mm was used. The tape wire is wound around the cushion layer 21 in multiple layers to form the conductor layer 30. In this conductor layer 30, the twist pitch of the superconducting wire is different in each layer. In addition, the current flowing in each layer can be equalized by changing the winding direction for each layer or for each of the plurality of layers.

  A conductor reinforcing layer 41 is formed immediately above the conductor layer 30. Here, the conductor reinforcing layer 41 was formed by winding a copper tape on the conductor layer 30 in a spiral manner. At that time, the winding pitch of the copper tape constituting the conductor reinforcing layer 41 is the same as the winding pitch of the insulating tape constituting the insulating layer 60, and is smaller than the winding pitch of the superconducting wire constituting the conductor layer 30. The conductor layer 30 is surely pressed against the inner peripheral side.

  On the outer periphery of the conductor reinforcing layer 41, an internal semiconductive layer 51, an insulating layer 60, and an external semiconductive layer 52 are formed in this order from the inside. The internal / external semiconductive layers 51 and 52 suppress the generation of minute voids at the interface between the conductor reinforcing layer 41 and the insulating layer 60 or the interface between the insulating layer 60 and the shield layer 70, and partial discharge in the voids. To prevent. For these semiconductive layers 51 and 52, carbon paper can be used. Further, the insulating layer 60 is formed by, for example, using an insulating tape (PPLP: registered trademark manufactured by Sumitomo Electric Industries, Ltd.) laminated with kraft paper and a resin film such as polypropylene and wound around the outer periphery of the internal semiconductive layer 51. be able to.

  A shield layer 70 is provided on the outer semiconductive layer 52 described above. The shield layer 70 is formed by winding a superconducting wire similar to that used for the conductor layer 30. In this shield layer 70, a current in the reverse direction having almost the same size as that of the conductor layer 30 is induced, thereby canceling out the magnetic field generated from the conductor layer 30 and preventing leakage of the magnetic field to the outside.

  Further, a shield reinforcing layer 42 is provided on the shield layer 70. Here, as with the conductor reinforcing layer 41, the shield reinforcing layer 42 was formed by winding a copper tape on the shield layer 70 in a spiral manner. At that time, the winding pitch of the copper tape constituting the shield reinforcing layer 42 is the same as the winding pitch of the insulating tape constituting the insulating layer 60, and is smaller than the winding pitch of the superconducting wire constituting the shield layer 70. The shield layer 70 is surely pressed against the inner peripheral side.

  The protective layer 80 is formed on the shield reinforcing layer 42 by wrapping kraft paper. The protective layer 80 mechanically protects the structure inside the shield reinforcing layer 42.

  On the other hand, as shown in FIG. 1, the heat insulating pipe 120 has a stainless steel double pipe structure having a corrugated inner pipe 121 and a corrugated outer pipe 122. Usually, a space is formed between the corrugated inner tube 121 and the corrugated outer tube 122, and the space is evacuated. In the space to be evacuated, a super insulation serving as a heat insulating material (not shown) is arranged to reflect radiant heat. An anticorrosion layer 130 is formed outside the corrugated outer tube 122.

  When forming the connecting portion, the conductor layer 30 is pressed by the conductor reinforcing layer 41 and the shield layer 70 is pressed by the shield reinforcing layer 42. Therefore, even when thermal expansion and contraction occurs in the cable, such as contraction during cooling, the superconducting layer And the relative movement of the conductor reinforcing layer does not occur. As a result, the superconducting layer can be prevented from buckling. In particular, since the reinforcing layers 41 and 42 are formed by the combined winding, even if the cable terminal is cut at the time of forming the connection portion, it is possible to suppress the reinforcing layers 41 and 42 from separating from the cut ends. When forming the connection portion, if the lengths of the conductor layer 30 and the conductor reinforcement layer 41 at the end of the cable are made the same, the conductor reinforcement layer 41 and the conductor insertion hole of the connection sleeve 210 (see FIG. 5) have a conductor. By inserting the layer 30, the conductor reinforcing layer 41 is also integrally soldered to the connection sleeve 210, and the buckling can be more effectively suppressed.

(Example 2)
Next, an example in which two cushion layers are further added to the configuration of Example 1 will be described with reference to FIG. 1 denote the same members. The core 110 of the cable 100 has a cushion layer 22 between the conductor layer 30 and the conductor reinforcement layer 41, except that the cushion layer 23 is provided between the shield layer 70 and the shield reinforcement layer 42. Other configurations are the same as those of the first embodiment. Hereinafter, this difference will be mainly described.

  These cushion layers 22 and 23 were also formed by winding carbon paper. By providing the cushion layers 22 and 23, direct metal contact between the conductor layer 30 and the conductor reinforcement layer 41 and between the shield layer 70 and the shield reinforcement layer 42 is avoided, and mechanical damage is suppressed. It is possible to suppress a reduction in electrical characteristics by suppressing the generation of a gap between 30, 41 or 70, 42.

  The superconducting cable of the present invention can be used as a power transportation means. In particular, the buckling of the superconducting layer can be suppressed in the connecting portion, which can contribute to the formation of a highly reliable connecting portion. In addition, the present invention can be applied to any of multi-core superconducting cables such as AC superconducting cables, DC superconducting cables, single-core superconducting cables, and 3-core batch type.

It is a cross-sectional view of the superconducting cable of the present invention. 2 is a cross-sectional view of a core of a superconducting cable in Example 1. FIG. 6 is a cross-sectional view of a core of a superconducting cable in Example 2. FIG. It is a cross-sectional view of a conventional superconducting cable. It is a model fragmentary sectional view which shows the connection part of the conventional superconducting cable. It is explanatory drawing which shows the relative movement of a conductor layer and an insulating layer.

Explanation of symbols

100 superconducting cable
110 core
10 Former 30 Conductor layer 60 Insulating layer 70 Shield layer 80 Protective layer
21, 22, 23 Cushion layer 41 Conductor reinforcement layer 42 Shield reinforcement layer
51 Internal semiconductive layer 52 External semiconductive layer
120 Heat insulation pipe 121 Corrugated inner pipe 122 Corrugated outer pipe 130 Corrosion protection layer
210 Connection sleeve 220 Solder 230 Reinforcing insulation layer

Claims (6)

A superconducting cable having a superconducting layer,
Provide a reinforcing layer to prevent buckling just above the superconducting layer ,
A superconducting cable , wherein the reinforcing layer is made of a tape material wound together . The superconducting layer conductor layer, a superconducting cable according to claim 1, wherein the reinforcing layer is a conductive reinforcing layer. The superconducting layer is shielding layer, a superconducting cable according to claim 1, wherein the reinforcing layer is a shielding reinforcing layer. The superconducting cable according to any one of claims 1 to 3, wherein a cushion layer is interposed between the superconducting layer and the reinforcing layer. The superconducting cable according to any one of claims 1 to 4, wherein a winding pitch of the tape material constituting the reinforcing layer is equal to or less than a winding pitch of the superconducting wire constituting the superconducting layer. Furthermore, an insulating tape is formed by winding an insulating tape, and includes an insulating layer that insulates the conductor layer constituting the superconducting layer,
  The superconducting cable according to any one of claims 1 to 5, wherein a winding pitch of the tape material constituting the reinforcing layer is the same as a winding pitch of the insulating tape.

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