JP2007200783A - Multiconductor superconductive cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiconductor superconductive cable capable of sufficiently absorbing thermal compression when cooling. <P>SOLUTION: This superconductive cable 1 is a three-conductor cable formed by stranding three-conductor cable cores 2 cooled by a coolant and housed in a heat insulating pipe 3. The three-conductor cable cores 2 are stranded while having a slack required to absorb thermal compression of the core itself at the time of cooling, and is equipped with a spacer 4A in a gap portion surrounded by the three-conductor cores 2 to keep the slack. The spacer 4A is formed of a material having brittleness by which it is crushed by the behavior of thermally compressed cores 2 when cooling. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-core superconducting cable housed in a heat insulating tube in a state where a plurality of cable cores are twisted together. In particular, the present invention relates to a multi-core superconducting cable that can sufficiently absorb thermal contraction of a cable core itself when cooled by a refrigerant filled in a heat insulating tube.

  In recent years, superconducting cables have been studied as power cables. The superconducting cable includes a cable core having a superconducting layer and a heat insulating tube that accommodates the core. In a multi-core cable, a plurality of cable cores are housed in a heat insulating tube in a twisted state. Such a superconducting cable is used for power supply in a state where a core such as liquid nitrogen is filled in a heat insulating tube and the core is cooled in order to bring the superconducting layer of the core into a superconducting state. Therefore, in the superconducting cable, the cable core and the heat insulating tube that are in contact with the refrigerant are cooled to a cryogenic temperature such as normal temperature (about 300 K) to about 80 K or less (77 K when the refrigerant is liquid nitrogen) by introduction of the refrigerant. While the temperature of the cable core and the heat insulating tube is changed from room temperature to extremely low temperature, the metal used for the material constituting the core and the heat insulating tube contracts by about 0.3%. That is, thermal contraction of about 30 cm occurs for every 100 m of cable. Usually, both ends of the superconducting cable are fixed by an intermediate connecting part for connecting the cables and a terminal connecting part for connecting the superconducting cable and a power device arranged on the room temperature side. Therefore, in a multi-core cable, when the twisted cable core contracts, the core moves so that the twist is tightened. That is, the core moves so that the twisted diameter of the cable core becomes smaller and the length of the twisted core becomes longer in the longitudinal direction of the core. At this time, in particular, the cable core of the superconducting cable receives a force in the radial direction of the core (side pressure) along with its axial direction (longitudinal direction) force, and may damage the superconducting layer whose performance is easily deteriorated due to mechanical stress. There is. If the superconducting layer is damaged excessively, it cannot function as a superconducting cable. Therefore, the superconducting cable needs to have a configuration that absorbs the heat shrinkage.

  As a configuration that absorbs heat shrinkage, for example, a structure in which a plurality of cable cores are twisted and stored in a heat insulating tube with slackness, and the heat shrinkage allowance is used to absorb heat shrinkage of the core itself. Possible (see Patent Document 1). In Patent Document 1, in order to give this slackness, when twisting three cable cores, a spacer made of felt is arranged between the cores and twisted together with the cores, and the twisted cores are stored in a heat insulating tube. It is disclosed that the spacer is removed before and the strand is stored in the heat insulating tube in a relaxed state. Since the spacer between the cable cores is removed, the core accommodated in the heat insulating tube can move without being restrained by the spacer.

JP 2002-216555 A

  After the cable core is housed in the heat insulation pipe, the superconducting cable is wound around a drum or the like, transported to the installation site and installed, and then introduced into the heat insulation pipe for use. At the time of this laying, in the superconducting cable described in Patent Document 1, since the spacer is removed as described above, the behavior of the cable core in the heat insulating pipe is not hindered by the spacer, so that the cable is pulled during laying. There is a risk that the slack will disappear and the heat shrinkage allowance cannot be secured sufficiently.

  Therefore, a main object of the present invention is to provide a multi-core superconducting cable in which a twisted cable core has a sufficient heat shrinkage before cooling.

  By adopting a configuration in which the spacers are laid and cooled with the spacers interposed between the cable cores, the inventors of the present invention ensure the looseness of the twist that becomes the heat shrinkage and do not hinder the behavior of the cores during cooling. Such a configuration was examined. As a result, the present invention stipulates that a member having a portion made of a brittle material that is crushed and broken by the behavior of the core during cooling is used as a spacer, and the spacer is provided between the cores. Specifically, the present invention is a multi-core superconducting cable in which a plurality of cable cores cooled by a refrigerant are twisted and housed in a heat insulating tube, and the core absorbs thermal contraction of the core itself during cooling. It is assumed that a spacer for holding the slack is disposed between the cores. As the spacer, a spacer having a brittle portion that is crushed by the behavior of the core that thermally contracts is used.

Hereinafter, the present invention will be described in more detail.
The cable of the present invention has a basic configuration that includes a cable core having a superconducting layer and a heat insulating tube that houses the core. As a basic configuration of the cable core, a configuration including a former, a superconducting conductor (superconducting layer), and an electric insulating layer in order from the center can be given. An external superconducting layer made of a superconducting material in the same manner as the superconducting conductor may be provided on the outer periphery of the electrical insulating layer, and a cable core having a protective layer on the outer periphery thereof. In the case of a cable core having an external superconducting layer, the external superconducting layer is set to ground potential (ground potential). When the cable core does not have an external superconducting layer, a grounding shield layer as a ground potential is provided.

  The former may be a solid body or a hollow body formed of a metal material such as copper or aluminum, and examples thereof include a stranded wire structure in which a plurality of copper wires are twisted together. The superconducting conductor is formed by winding a wire in which a plurality of filaments made of an oxide superconducting material, for example, a Bi2223 superconducting material, are arranged in a silver sheath or a silver alloy sheath around the former in a single layer or multiple layers. To do. When the superconducting conductor is a multilayer, 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). The electrical insulating layer may be formed by winding an insulating material such as insulating paper such as kraft paper or semi-synthetic insulating paper such as PPLP (registered trademark) around the outer periphery of the superconducting conductor. In the case of a cable core having an outer superconducting layer on the outer periphery of the electric insulating layer, the outer superconducting layer is formed of a superconducting material in the same manner as the superconducting conductor. Furthermore, a semiconductive layer may be provided by carbon paper or the like between the superconducting conductor and the electric insulating layer, and between the electric insulating layer and the external superconducting layer. The cable core having the former inner semiconductive layer and the latter outer semiconductive layer tends to have stable electric performance. Examples of the heat insulating pipe that stores the cable core include a double structure including an inner pipe and an outer pipe, and a configuration in which the inside of the double pipe is evacuated. You may arrange | position heat insulating materials, such as a super insulation, between both pipes. The inside of the inner tube is used as a refrigerant flow path that is filled with a refrigerant such as liquid nitrogen that cools the superconducting layer such as a superconducting conductor or an external superconducting layer. As the inner tube and the outer tube, a flat tube having a smooth surface made of a metal material such as lead, aluminum, or stainless steel, a corrugated tube having irregularities on the surface, or the like can be used. The cable of the present invention is a multi-core cable housed in the heat insulating tube in a state where a plurality of cable cores having the above-described configuration are twisted together. That is, the cable of the present invention includes at least two cable cores. In particular, when the cable of the present invention is a three-core cable, it is easy to stably form a twisted structure, and when this three-core cable is used for three-phase AC power transmission, three-phase power is transmitted collectively with a single cable. can do.

  Since various metal materials are used for the cable constituent members as described above, cable cores including members made of these metal materials cause thermal contraction when cooled with a refrigerant such as liquid nitrogen, and the force due to the thermal contraction is the core. In addition, there is a risk that the core component, particularly the superconducting layer, may be destroyed. Therefore, in the cable of the present invention, in order to absorb the heat shrinkage of the cable core itself, a plurality of cores are twisted together with slackness, and this slackness is used as a shrinkage allowance. In particular, in the cable of the present invention, a spacer is twisted together with a cable core, the spacer is interposed between the cores to form the slack, and the spacer is left as it is without being removed from between the cores. The cable of the present invention is laid with a spacer interposed between the cable cores, so that the cable core is less likely to be loosened due to pulling during installation, and the cable core itself absorbs thermal contraction before cooling after laying. Can be held more reliably.

  For example, when the cable of the present invention is a two-core cable having a two-core cable core, the two cores and the spacer are twisted together so that the spacer is disposed between one core and the other core. Good. For example, when the cable of the present invention is a three-core cable having a three-core cable core, the three-core cores are twisted so as to form a triangular shape, and a spacer is disposed between adjacent cores in the same manner as the two-core cable. That is, it is good to arrange the spacers between the three cores and twist them together. However, in this case, the spacer may come off (drop off) between the cores during twisting. Therefore, when the cable of the present invention is a three-core cable, the three-core cable is formed in the center of the three-core core arranged in a triangular shape and the spacer is arranged in the gap surrounded by the three-core core. It is preferable to twist the core and the spacer together. Similarly, for a multi-core cable having four or more cores, it is preferable to arrange a spacer in a gap formed in the center of the multi-core.

  The cable core is usually manufactured as a continuous long body. Therefore, when making a spacer into a short body, it is good to prepare several spacers and to arrange these spacers along the longitudinal direction of a cable core. When the spacer is a continuous long body, it is preferable that the spacer is easily twisted with a long cable core. The cross-sectional shape of the spacer is, for example, a circular shape, but is not particularly limited. The spacer may be solid or hollow. In the case of a hollow body, since the spacer forming material can be reduced as compared with the case of a solid body, the amount of fragments generated by crushing can be reduced.

  The spacer is large enough to maintain a slack so that the twisted cable core can have sufficient heat shrinkage before cooling and is not crushed by the core before cooling Use one with a certain degree of strength. On the other hand, in the cable of the present invention, the core is cooled while the spacer is present between the cable cores as described above. Therefore, it is desirable that the spacer does not hinder the behavior of the cable core that is thermally contracted during cooling. Therefore, in the cable of the present invention, a spacer having a brittle portion having brittleness that is crushed by being crushed by the behavior of the cable core that is thermally contracted is used. The entire spacer may be formed of the brittle material, and the entire spacer may be a brittle portion, part of the spacer may be formed of the brittle material, and the other portion is formed of a non-brittle material. And it is good also as a combined body of a brittle part and a non-brittle part. Since the part which contacts a cable core in a spacer becomes a part which is almost crushed by the behavior of the core at the time of cooling, such a part is formed with a brittle material. Therefore, when it is set as a combined body, for example, it is preferable that the center portion is made of a non-brittle material and the outer periphery thereof is made of the above brittle material. The cable according to the present invention including the spacer having such a brittle portion, when the cave core is thermally shrunk during cooling, the brittle portion provided in the spacer disposed between the cores is sandwiched between the cores and crushed, so that a plurality of fragments By being separated into two, the core can move sufficiently. Therefore, the cable of the present invention is designed so that the gap between the cable cores provided by the slack is reduced, more specifically, the twisted diameter is reduced, even when the spacer is present during cooling. The core can move so that the length of the twisted core becomes longer in the longitudinal direction of the core, and the thermal contraction of the core itself can be sufficiently absorbed.

  The material for forming the brittle portion may be appropriately selected depending on the refrigerant to be used. For example, when liquid nitrogen, liquid helium, or the like is used as the refrigerant, the brittle temperature (temperature at which the cable core is crushed) is 80 to 243K. A material whose degree, more preferably, the embrittlement temperature is 210K to 243K. Since the embrittlement temperature is a relatively high temperature of 210K to 243K, the brittle part is in a state that can be collapsed at an early stage after the start of cooling, and it is difficult to hinder the behavior when the cable core contracts. . Examples of the material having such an embrittlement temperature include rubber materials such as neoprene rubber, natural rubber, butyl rubber, styrene rubber, ethylene propylene rubber, silicon rubber, and fluorine rubber. The rubber material such as neoprene rubber is cured when cooled by the refrigerant, and is crushed by the behavior of the core when the embrittlement temperature is reached. However, if the thickness is reduced to some extent as will be described later, the core is less likely to be crushed by the behavior of the core even at the embrittlement temperature. The brittle portion made of such a material may be formed by, for example, extrusion. Note that superconducting cables are operated after a refrigerant such as liquid nitrogen has been introduced and the cable core (superconducting layer) has reached the same temperature as the refrigerant so that the superconducting state of the superconducting layer can be sufficiently maintained. Be started. Therefore, the superconducting cable thermally contracts in the range from the normal temperature to the refrigerant temperature from the start of introduction of the refrigerant to operation. Accordingly, the embrittlement temperature of the brittle portion can be any temperature in the range from room temperature to the refrigerant temperature. However, if the brittle part is crushed at room temperature, it is not possible to sufficiently secure the slackness due to the intervening spacer before cooling. Further, considering the storage temperature of the superconducting cable before cooling and the environmental temperature of the laying site, the brittle temperature of the brittle portion is appropriately about 80 to 243K.

  When the entire spacer is made to be a brittle part, it is crushed by the cable core and separated into a plurality of pieces, and if the pieces are present in the heat insulation pipe, after the refrigerant is introduced into the heat insulation pipe, these pieces inhibit the flow of the refrigerant. Otherwise, there is a risk that the fragments transported together with the refrigerant come into contact with the cable constituent member to cause problems such as damage to the cable constituent member. Then, it can prevent effectively that a fragment floats in a heat insulation pipe | tube by using the spacer which accommodated the brittle part in the bag-shaped body. The bag-like body may be any one that has a flexibility that can capture debris, is not crushed by the behavior of the core during heat shrinkage, and can be deformed at the refrigerant temperature, and does not penetrate the refrigerant. The structure may be sufficient and the structure which a refrigerant | coolant can permeate | transmit may be sufficient. In the latter case, a bag-like body having holes penetrating the front and back is preferable. For example, a sheet-like base material is provided with a plurality of holes, and a bag-like body can be produced with the perforated base material, or a long bag-like material can be woven or knitted to produce a mesh-like bag-like body. Can be mentioned. By setting it as the structure which distribute | circulates a refrigerant | coolant in a bag-shaped body, the distribution resistance of a refrigerant | coolant can be reduced. Therefore, with this configuration, it is possible to reduce the pressure loss of the cable constituent member due to the increase in flow resistance. The size of the hole or mesh is adjusted to such an extent that fragments of the brittle portion can be captured. Examples of the material for the bag-like body include rubber materials such as neoprene rubber, natural rubber, butyl rubber, styrene rubber, ethylene propylene rubber, silicon rubber, and fluorine rubber. When a bag-like body is made of these rubber materials, if the thickness is reduced to about several hundred μm, the cable core is not easily crushed due to the behavior of the cable core during thermal contraction. In addition, examples of the material for the bag-like body include fluororesins such as Teflon (registered trademark), glass fibers, and the like. Further, the size of the opening of the bag-like body is sufficient as long as the brittle portion can be inserted, and may be equal to or larger than the outer periphery of the brittle portion. .

  When a spacer made of a combination having a central part made of a non-brittle material and an outer peripheral part made of a brittle material arranged on the outer periphery thereof, the central part made of a non-brittle material is particularly a cable core during heat shrinkage. The size is set so as not to impede the behavior. For example, in the case of a multi-core cable having three or more cores, a gap portion surrounded by the core is formed at the center of the twisted core. Although this gap portion becomes smaller due to the behavior of the cable core during heat shrinkage, there is a limit to the reduction, and a minimum size is secured. Therefore, if the size of the central portion made of the non-brittle material is made smaller than the gap portion having the minimum size, the behavior of the cable core during cooling is not hindered. Examples of the non-brittle material include metal materials such as stainless steel and copper, and resin materials such as FRP (fiber reinforced resin) and epoxy resin.

  If the temperature of the superconducting cable, particularly the cable core, changes rapidly, the cable performance may be affected. Therefore, when introducing a refrigerant into a superconducting cable, it is common to introduce the refrigerant so that the core is gradually cooled while checking the temperature over the entire length of the cable core. In order to check the temperature of the entire length of the cable core, an optical fiber is used as a temperature sensor, and this optical fiber is arranged along the core. Also in the cable of the present invention, an optical fiber may be arranged in the longitudinal direction of the cable. For example, the optical fiber is arranged between twisted cable cores. At this time, the cable of the present invention includes the spacer and an optical fiber serving as a temperature sensor between the cable cores. In particular, when the spacer has an optical fiber, the spacer and the temperature sensor can be simultaneously disposed between the cores. For example, in the case of a spacer having the bag-like body, a brittle part or a combination of a brittle part and a non-brittle part and an optical fiber may be inserted into the bag-like body, or a hollow body spacer. An optical fiber may be inserted and arranged in the internal space of the hollow body, or may be integrated by incorporating the optical fiber in a brittle part or a non-brittle part. In the latter case, for example, a spacer containing the optical fiber can be formed by extruding a brittle part forming material or a non-brittle part forming material around the optical fiber as a core material. In addition, when using a spacer with an optical fiber built in, the optical fiber is crushed by the core due to the behavior of the cable core during thermal contraction if the optical fiber is formed at the center of the brittle part or the non-brittle part. Such a problem can be prevented. Alternatively, the outer periphery of the optical fiber may be a spacer provided with a short body made of a brittle material or a non-brittle material so as to be spaced apart in the longitudinal direction. Thus, an optical fiber can also be protected by inserting an optical fiber in a bag-like body or providing a brittle part or a non-brittle part on the outer periphery. A commercially available optical fiber may be used as a temperature sensor.

  The superconducting cable of the present invention does not substantially change its shape when the cable core is not thermally shrunk before cooling, and changes its shape as the core shrinks during cooling, specifically, it is crushed. A spacer having a brittle portion made of such a material is interposed between the cable cores. The cable of the present invention creates a slack in the twisting of the cable core due to the interposition of the spacer, and lays in a state where the spacer is interposed between the cable cores, so that even if the cable is pulled during laying, the core It is difficult to eliminate loosening due to twisting. Therefore, the cable of the present invention can sufficiently secure the slack (heat shrinkage allowance) before cooling. Moreover, even if it cools in the state which provided the said spacer as it is, this invention cable does not inhibit the behavior of the core at the time of a heat contraction by a brittle part being crushed by a cable core. As described above, the cable according to the present invention secures a heat shrinkage allowance due to the twisting of the cable core, so that the core can sufficiently move and absorb the shrinkage at the time of the heat shrink, and the core, particularly, the superconducting layer is damaged. To prevent.

  In addition, by using a spacer in which a brittle portion is housed in a bag-like body, the cable of the present invention can prevent a plurality of pieces generated by breaking the brittle portion from obstructing the circulation of the refrigerant or transporting by the refrigerant. It is possible to suppress the occurrence of problems such as damage to the cable component.

  Furthermore, by using a spacer including an optical fiber serving as a temperature sensor, the cable of the present invention can easily check the temperature in the vicinity of the cable core when the refrigerant is introduced.

  Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view showing a schematic configuration of a superconducting cable of the present invention, in which (A) shows a state before cooling and (B) shows a state during cooling. FIG. 1B shows only the cable core portion. The superconducting cable 1 is a three-core cable in which a three-core cable core 2 is twisted and stored in a heat insulating tube 3. The heat insulating tube 3 is filled with a refrigerant such as liquid nitrogen, and the cable core 2 is cooled by this refrigerant. The three-core cable core 2 is twisted together with a slack necessary to absorb the thermal contraction of the core 2 itself during cooling, and the cable 1 is shown in FIG. As shown, a spacer 4A is provided in the gap surrounded by the three cores 2. The spacer 4A can maintain the space of the gap before cooling, and is brittle so as to be crushed by the behavior of the core 2 that thermally contracts during cooling as shown in FIG. 1B. Is formed. Hereinafter, each configuration will be described in more detail.

  The cable core 2 includes a former 21, a superconducting conductor 22, an electrical insulating layer 23, an external superconducting layer 24, and a protective layer 25 in order from the center. The former 21 is a member that serves as a core for retaining the superconducting conductor 22, and has a function of suppressing damage to the conductor 22 as a flow path when an accident current flows through the conductor 22. The former 21 has a configuration in which a plurality of coated strands in which an enamel insulating coating is formed on a copper wire are twisted together. The superconducting conductor 22 and the external superconducting layer 24 are formed by winding Bi2223-based Ag sheathed tape wires in multiple layers on the former 21 and the electrical insulating layer 23, respectively. In AC power transmission, the external superconducting layer 24 induces a reverse current of approximately the same magnitude as that of the superconducting conductor 22. The magnetic field generated by the induced current cancels the magnetic field generated from the conductor 22, and leaks the magnetic field to the outside. Functions as a shield to prevent Further, the external superconducting layer 24 can be used as a return path in direct current power transmission when the superconducting conductor 22 is used as a forward path. In any power transmission, the external superconducting layer 24 is grounded. The electrical insulating layer 23 is formed by winding PPLP (registered trademark) obtained by bonding polypropylene and kraft paper around the outer periphery of the superconducting conductor 22 in multiple layers. An inner semiconductive layer and an outer semiconductive layer made of carbon paper may be formed on the inner and outer peripheral sides of the electrical insulating layer 23, respectively. A protective layer 25 formed by winding kraft paper is provided on the outer periphery of the external superconducting layer 24. The protective layer 25 mechanically protects the outer superconducting layer 24 and is formed of an insulating material such as kraft paper to electrically insulate the outer superconducting layer 24 from the heat insulating tube 3 (inner tube 31). Thus, it is possible to prevent the induced current and the return current from being diverted to the heat insulating tube 3.

  The heat insulation pipe 3 is a double pipe comprising an inner pipe 31 and an outer pipe 32, and is constituted by a stainless corrugated pipe. The space between the tubes 31 and 32 is evacuated to a predetermined degree of vacuum. A heat insulating material layer (not shown) formed by arranging super insulation is provided on the outer periphery of the inner tube 31. The cable core 2 is housed inside the inner pipe 31 and a coolant such as liquid nitrogen is circulated during the cable operation to cool the core 2. An anticorrosion layer 5 made of polyvinyl chloride is provided on the outer periphery of the heat insulating tube 3.

  The spacer 4A is a long solid body having a circular cross section formed entirely of neoprene rubber, and is formed by extrusion. The spacer 4A is twisted together with the three cores 2 so as to be disposed in a gap surrounded by the three cores 2 when the three cable cores 2 having the above-described configuration are twisted together. Be united. With this configuration, the twisted cable core 2 is held by the spacers 4 </ b> A interposed between the three cores 2, which is a contraction allowance for absorbing the thermal contraction of the core 2 itself during cooling. Therefore, the spacer 4A is sufficiently large to function as a member for ensuring looseness of twisting before cooling. The integrated product of the cable core 2 and the spacer 4A is stored in the heat insulating tube 3. In housing the integrated product in the heat insulating tube 3, the heat insulating tube 3 is previously evacuated between the inner tube 31 and the outer tube 32. The integrated object is inserted into the heat insulating tube 3 by sending the integrated material to the heat insulating tube 3 in an endless track. When forming a heat-insulated pipe by welding, place a plate-like material that becomes the inner pipe on the outer periphery of the integrated object, weld both edges of the plate-like material to make an inner pipe, and form the outer pipe in the same way And it is good also as a state in which the integrated object was accommodated in the heat insulation pipe | tube. In this case, after forming the outer tube, a vacuum is drawn between the inner tube and the outer tube.

  As described above, the superconducting cable 1 shown in FIG. Such a superconducting cable 1 is laid and an intermediate connection portion and a termination connection portion are appropriately formed to construct a line. The superconducting cable 1 is laid with the spacer 4 </ b> A interposed between the cable cores 2. For this reason, even when the cable 1 is pulled during installation, the slack provided by twisting the cable core 2 is not eliminated by the spacer 4A existing between the cores 2. In operating the constructed track, a refrigerant (here, liquid nitrogen) is introduced into the heat insulating tube 3. When the superconducting cable 1 is cooled by introducing the refrigerant, the metal material constituting the cable core 2 and the heat insulating tube 3 is thermally contracted. Since both ends of the superconducting cable 1 are fixed by the intermediate connection part and the terminal connection part, when the thermal contraction occurs, the cable core 2 moves so that the twist is tightened, that is, the slack is eliminated. In the superconducting cable 1, since the spacer 4A exists even when the refrigerant is introduced, the slack is ensured. Therefore, the cable core 2 can operate so as to eliminate slackness during heat shrinkage. That is, the superconducting cable 1 can securely hold the slack and absorb heat shrinkage by the slack.

  When the refrigerant is introduced and cooled, the core 2 is tightened so that the twist of the cable core 2 is tightened, that is, the length of the twisted core 2 is increased in the longitudinal direction. As shown in FIG. 1B, the gap surrounded by the three cores 2 is also reduced. On the other hand, the spacer 4A made entirely of neoprene rubber is cooled and hardened by introduction of the refrigerant. In this state, when the cable core 2 moves so as to reduce the gap as described above due to heat shrinkage, the pressure applied from the core 2 gradually increases as the spacer 4A is sandwiched between the three cores 2. Eventually, as shown in FIG. 1 (B), it is broken by this pressure and broken down into a plurality of pieces 41. Therefore, even when the spacer 4A exists between the cable cores 2 during cooling, the behavior is not hindered by the spacer 4A, and the core 2 can move sufficiently as much as necessary to absorb the heat shrinkage. . In addition, the heat insulation pipe | tube 3 can absorb heat contraction by the pipe | tube itself by making it the corrugated pipe | tube which can be expanded-contracted.

  The superconducting cable 1 of the present invention includes a spacer 4A made of a brittle material that is crushed by the behavior of the cable core 2 at the time of thermal contraction, so that the looseness of the twist can be sufficiently retained before cooling. Sometimes heat shrinkage can be fully absorbed. Therefore, the superconducting cable 1 of the present invention can more reliably prevent damage to the superconducting layer due to heat shrinkage. In addition, since the superconducting cable 1 of the present invention has a configuration in which the spacer 4A is disposed in the gap surrounded by the three-core cable core 2, the spacer 4A is not dropped from between the cores 2 during twisting.

  In the first embodiment, the spacer is made of a brittle material as a whole. For example, the central portion is made of a non-brittle material such as stainless steel, and the outer circumference is provided with a layer made of a brittle material such as neoprene rubber. A spacer may be used.

  In Example 1 described above, a superconducting cable including a spacer made entirely of a brittle material has been described. In this example, a superconducting cable including a spacer in which a brittle portion made of a brittle material is housed in a bag-like body will be described. FIG. 2 is a cross-sectional view showing a schematic configuration of a cable core portion in the superconducting cable of the present invention, where (A) shows a state before cooling, and (B) shows a state during cooling. The basic configuration of the superconducting cable shown in this example is the same as that of the first embodiment, and the spacer configuration is different. Therefore, here, the spacer is described in detail, and the other configurations are omitted.

  The spacer 4 </ b> B includes a brittle portion 42 and a bag-like body 43 that accommodates the brittle portion 42. The brittle portion 42 is a long solid body having a circular cross section made of neoprene rubber, and is formed by extrusion. The bag-like body 43 is made of neoprene rubber having a thickness of 100 μm, has a plurality of holes so that the refrigerant can permeate, and the size of the opening is larger than the outer periphery of the brittle portion 42. The brittle portion 42 is inserted into the bag-like body 43 to produce the spacer 4B in which the brittle portion 42 is enclosed in the bag-like body 43, and the three cable cores 2 and the spacer 4B are twisted in the same manner as in the first embodiment. Combine these together and store the integrated product in a heat insulating tube. And after laying, a refrigerant | coolant is introduce | transduced into a heat insulation pipe | tube.

  Due to the behavior of the cable core 2 cooled by the introduction of the refrigerant, the brittle portion 42 is crushed into a plurality of pieces 41. This is the same as the first embodiment. However, since the spacer 4B includes the bag-like body 43, even if the brittle portion 42 is separated into a plurality of pieces 41, these pieces 41 are captured by the bag-like body 43 and go out of the bag-like body 43. It is suppressed. Therefore, it is possible to prevent problems such as the broken pieces 41 preventing the refrigerant from flowing or being transported by the refrigerant and damaging the cable constituent members. Moreover, since the bag-like body 43 has such flexibility that it deforms with the behavior of the cable core 2 during heat shrinkage, the behavior of the core 2 is not hindered. Note that the bag-like body 43 may contain not only the brittle portion 42 but also an optical fiber for temperature measurement as will be described later along the brittle portion 42.

  Next, a superconducting cable having a spacer containing an optical fiber serving as a temperature sensor will be described. FIG. 3 is a cross-sectional view showing a schematic configuration of a cable core portion in the superconducting cable of the present invention, in which (A) shows a state before cooling and (B) shows a state during cooling. The basic configuration of the superconducting cable shown in this example is the same as that of the first embodiment, and the spacer configuration is different. Therefore, here, the spacer is described in detail, and the other configurations are omitted.

  The spacer 4 </ b> C includes a brittle portion 44 and a temperature measuring optical fiber 45 built in the brittle portion 44. The brittle portion 44 is a long body having a circular cross section made of neoprene rubber, and is formed by extrusion. The optical fiber 45 is a commercially available one that is used as a temperature sensor. By extruding neoprene rubber to the outer periphery of the optical fiber 45, a spacer 4C containing the optical fiber 45 is produced at the center of the brittle portion 44, and the three cable cores 2 and the spacer 4C are formed as in the first embodiment. Twist them together. By this twisting, the optical fiber 45 is arranged over the entire length of the cable core 2. The integrated product of the cable core 2 and the spacer 4C is housed in a heat insulating tube as in the first embodiment. And after laying, a refrigerant | coolant is introduce | transduced into a heat insulation pipe | tube. At this time, the spacer 4 </ b> C includes the optical fiber 45 serving as a temperature sensor, so that the temperature can be confirmed over the entire length of the cable core 2. Specifically, a temperature detection device having a laser light source is connected to the end of the optical fiber, laser light having a pulse waveform is incident from one or both ends of the optical fiber, and the intensity of the Raman backscattered light is detected, The temperature can be obtained from the property that the intensity of the scattered light depends on the temperature. Further, the temperature distribution along the optical fiber can be obtained by determining the generation position of the scattered light based on the round-trip time from when the laser light is incident until the scattered light is detected. Since the optical fiber 45 is arranged in the longitudinal direction of the cable core 2, a temperature distribution can be obtained along the longitudinal direction of the core 2. Since the introduction amount of the refrigerant can be adjusted based on this temperature distribution, the cable core 2 is rapidly cooled by the refrigerant, and the performance of the core 2 is prevented from being deteriorated by this sudden temperature change. In addition, since the optical fiber 45 can be disposed along the cable core 2 at the same time as the brittle portion 44 by forming the integrated product, the manufacturing time of the superconducting cable can be shortened. Furthermore, since the spacer 4C is configured to include the optical fiber 45 so as to be positioned at the center of the brittle portion 44, the cable core 2 has three cores during cooling as shown in FIG. Even if the gap surrounded by the core 2 moves so as to be small, the optical fiber 45 is generally in a state of being arranged before cooling, that is, in a state of being arranged at the center of the gap as shown in FIG. Maintained. That is, the optical fiber 45 hardly contacts the cable core 2 even during cooling, and is not crushed by the core 2. Therefore, the temperature near the cable core 2 can be reliably measured by the optical fiber 45. Note that the brittle portion 44 containing the optical fiber 45 shown in the present embodiment may be accommodated in the bag-like body described in the second embodiment.

  The superconducting cable of the present invention can be suitably used for power supply such as AC power transmission or DC power transmission.

It is sectional drawing which shows schematic structure of this invention superconducting cable which provides the spacer which consists entirely of a brittle material, (A) is a state before cooling, (B) shows the state at the time of cooling of a cable core part. It is sectional drawing which shows schematic structure of the cable core part of this invention superconducting cable which provides the spacer by which the brittle part was accommodated in the bag-like body, (A) is the state before cooling, (B) is the state at the time of cooling Indicates the state. It is sectional drawing which shows schematic structure of the cable core part of this invention superconducting cable which provides the spacer which incorporates the optical fiber for temperature sensors in a brittle part, (A) is the state before cooling, (B) is cooling Indicates the state of the hour.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Superconducting cable 2 Cable core 3 Heat insulation pipe 4A, 4B, 4C Spacer 5 Corrosion prevention layer 21 Former 22 Superconducting conductor 23 Electrical insulation layer 24 External superconducting layer 25 Protection layer 31 Inner pipe 32 Outer pipe 41 Fragment 42, 44 Brittle part 43 Bag shape Body 45 Optical fiber

Claims (4)

A multi-core superconducting cable in which a plurality of cable cores cooled by a refrigerant are twisted together and stored in a heat insulating pipe,
The core is twisted together with a slack to absorb the heat shrinkage of the core itself during cooling,
A spacer that holds the slack is disposed between the cores,
The multi-conductor superconducting cable, wherein the spacer has a brittle portion that is crushed by the behavior of a core that is thermally contracted. A superconducting cable is a three-core cable with three cores,
The multi-core superconducting cable according to claim 1, wherein the spacer is disposed in a gap surrounded by a twisted three-core core.   The multi-core superconducting cable according to claim 1, wherein the spacer includes a bag-like material including the brittle portion.   The multi-conductor superconducting cable according to any one of claims 1 to 3, wherein the spacer includes an optical fiber that is disposed in a longitudinal direction of the cable and serves as a temperature sensor.

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