HK1069671B - Superconducting cable joint structure - Google Patents

Description

Superconducting cable joint structure

Technical Field

The present invention relates generally to a superconducting cable joint structure, and more particularly, to effectively preventing conductor joint portions from being overheated during a jointing process, and thereby connecting an end of a core of a superconducting cable to a mating conductor.

Background

There is a trend today for cities and similar areas to consume more power and therefore require greater underground power transfer capabilities. Therefore, a superconducting cable allowing a current density close to 100 times that of the conventional cable was developed. Such a superconducting cable is constructed such that a plurality of cable cores having superconductors pass through an inner space of a sheath having liquid nitrogen or the like flowing therethrough to serve as a coolant layer, as disclosed in japanese laid-open patent No. 2002-.

In order to lay the aforementioned superconducting cables underground, such superconducting cables having a prescribed length must be connected together. However, a method aiming at proper connection of existing superconducting cables has not been studied so far. Japanese laid-open patent No.7-335358 discloses joining a conventional non-superconducting power cable with a mating power cable and thereby connecting them together. More specifically, as shown in fig. 11, the power cables 1 have their respective ends with the respective exposed conductors 2 abutted against each other and connected together by a conductor connecting sleeve 3 fitted on the outside of the power cable 1, and further, they are surrounded from the outside in the circumferential direction by an oil-impregnated paper.

However, if the cores in the superconducting cables are respectively joined and thus connected together by joining the conventional power cables 1 together as shown in fig. 11, the conductor connecting sleeve 3 as in the ordinary conductor will be connected together with the superconductor. This results in a higher resistance value at the portion where the ordinary conductor is connected to the superconductor. As a result, more heat is generated and the coolant surrounding the core of the cable boils, eventually damaging the coolant impregnated paper, and the refrigerator must have a large capacity to operate in order to maintain the superconducting properties of the cable. Also, a higher resistance at a portion where a conductor connecting sleeve formed of a common conductor is connected to a superconductor leads to a decrease in the current capacity of the superconducting cable as a whole.

Disclosure of Invention

The present invention seeks to join and thereby join together cores in a superconducting cable, respectively, while preventing the joint from increasing in temperature due to heat generation, while allowing the joint to provide a smaller electrical resistance and thereby generate less heat.

In one aspect, the present invention provides a structure for jointing a superconducting cable used at a cryogenic temperature or jointing a terminal of the superconducting cable with a general conductive cable, the structure comprising: a joint insulating layer provided on an outer periphery of a conductor connecting portion that connects together the conductors in the superconducting cable or the conductors in the superconducting cable and the conductors in the ordinary conductive cable, respectively; and at least one separate coolant channel provided at the joint insulating layer to cool the conductor connecting portion. It should be noted that, in the present invention, the common conductive cable further includes a lead bar (a lead rod), a current conducting wire and other similar connecting rods, conductor drawing rods (conductor drawing rods) and other similar metal rods.

The joint insulating layer has a coolant passage for receiving and flowing a coolant. When the conductor connection part generates heat, the coolant flowing through the coolant passage can remove the heat to prevent the conductor connection part from overheating.

Preferably, in the structure, the superconducting cable has a sheath and a cable core inserted in an inner space of the sheath. The cable core has a sizing tube made of long fibers, a superconducting layer disposed on a radially outer surface of the sizing tube, and an insulating layer disposed radially outside the superconducting layer. The inner space serves as a coolant layer through which a coolant passes, the coolant layer being in direct contact with the joint insulating layer, with coolant channels through which the coolant in the coolant layer flows.

Thereby, the coolant for cooling the cable core having the superconducting layer serving as a conductor can also flow into the coolant channel in the joint insulating layer.

Preferably, in the structure, the joint insulating layer is formed of a coolant-impregnated paper disposed in layers. The joint insulation layer formed of coolant-impregnated paper can also be used directly for cooling the conductor connection. This can interact with the effect achieved with the coolant channels to cool the conductor connection, resulting in a synergistic effect.

Preferably, the structure further comprises a conductor connection sleeve which is arranged at the conductor connection and is pressure-connected to the other radial surface of the conductor in the superconducting cable arranged against each other or to one radial outer surface of the conductor in the superconducting cable arranged against each other with the conductor in the ordinary conducting cable. The conductors which abut one another and are connected together by the conductor connecting sleeves which are fitted on the outside can be mechanically stabilized in their connection.

Preferably, in the structure, the coolant passage has a radially inner opening along a radially outer surface of the conductor connecting sleeve to allow the radially outer surface to directly contact the coolant.

The opposing conductors are joined together by an outer conductor connecting sleeve, and the sleeve generates heat. However, the coolant passage having the radially inner opening communicating with the connecting sleeve may allow the coolant to pass through the radially inner opening to directly cool the radially outer surface of the connecting sleeve, and thereby more efficiently prevent the connecting sleeve from overheating.

Preferably, in the structure, the coolant passage has an inclined passage for connecting the radially inner opening to the radially outer opening of the coolant passage.

If the coolant channels form a right angle with respect to the longitudinal direction of the cable and thereby provide a clearly inclined portion, the voltage applied to the conductor will enhance the electric field formed at the boundary of the insulating layer and the coolant channels, and the equipotential surfaces surrounding the electric field formed there will not remain parallel at the clearly inclined portion, resulting in the electric field exceeding a critical value. The inclined coolant channel can effectively attenuate an electric field formed at a boundary surface of the insulating layer and the coolant channel.

Also, the joint insulating layer may be formed of an insulating resin mold with a coolant passage. In other words, there is no need to wet the paper with a layered arrangement of coolant.

Preferably, in the structure, the superconducting cable and the ordinary conducting cable are connected together via the conductor connecting portion so that the conductor protruding from the ordinary conducting cable and the conductor in the superconducting cable are connected together via the conductor connecting portion, the conductor connecting portion is circumferentially provided with a joint insulating layer, and the coolant passage is provided at an intersection of one end face of the joint insulating layer and an outer end face of the ordinary conducting cable.

A conductor of a normal conduction cable is connected to a superconducting cable, and a coolant passage is provided in a portion of the normal conduction cable having an interface with a joint insulating layer. The coolant channel can be easily formed. Also, when the conductor connection part generates heat, the heat may be dissipated into the coolant passage to prevent the conductor connection part from being overheated.

Preferably, the conventional conductive cable provides a fixing portion of an insulator made of an epoxy resin exhibiting high heat resistance, a small shrinkage percentage with curing thereof (high dimensional stability), and superior adhesion.

Preferably, in the structure, the interface is inclined with respect to a longitudinal direction of the cable, and the coolant passage is provided.

If the coolant channel forms a right angle with respect to the longitudinal direction of the cable and thereby provides a clearly inclined portion, the voltage applied to the conductor will enhance the electric field formed at the boundary of the insulating layer and the coolant channel, and the equipotential surfaces surrounding the electric field formed there will not remain parallel at the clearly inclined portion, resulting in the electric field exceeding a critical value. The coolant passage provided on one inclined plane can effectively attenuate the electric field at the boundary.

If the coolant channel forms a right angle with respect to the longitudinal direction of the cable and thus a clearly inclined portion, the equipotential surfaces of the electric field formed there by the current flowing through the conductor will not remain parallel in the clearly inclined portion, resulting in the electric field exceeding a critical value. The coolant channel provided at one of the inclined interfaces may facilitate that equipotential surfaces of the electric field remain substantially parallel in the joint insulating layer to prevent enhancement of the electric field.

In another aspect, the present invention provides a superconducting cable joint structure for jointing a superconducting cable used at a cryogenic temperature or jointing a terminal of the superconducting cable with a general conductive cable. This structure includes: a conductor connecting portion allowing the respective conductors in the cable to abut against each other and be connected together, or allowing the superconducting cable and the respective conductors in a general conductive cable to abut against each other and be connected together; a conductor connecting sleeve which is connected with the circumference of the conductor connecting part in a pressing way; a superconducting wire disposed on a radially outer surface of the conductor connecting sleeve or embedded inside the conductor connecting sleeve to reduce heat generation; and a joint insulating layer provided on an outer periphery of the conductor connecting sleeve or the superconducting wire.

Since the resistance of a superconducting wire connected to the outer surface or the inner surface of the conductor connecting sleeve is significantly smaller than that of the connecting sleeve, a current from a conductor (superconductor) in a superconducting cable tends to flow through the wire rather than the connecting sleeve. Thereby, less heat can be generated. Also, at the conductor connection, current tends to flow through the superconducting wire rather than the conductor connection sleeve, because the superconducting wire has a smaller resistance than the conductor connection sleeve. In general, the superconducting cable can be prevented from having a small current capacity.

Opposite ends of the superconducting wire are electrically connected to a conductor in each of two superconducting cables to be connected together, or to a conductor in a superconducting cable to be connected together and a conductor in a normal conducting cable.

Thereby, a superconducting wire having a small resistance can be directly and laterally connected (crosslink) to the conductors in the superconducting cable, respectively, to reduce heat generation, and the conductor connection sleeve can maintain a stable connection.

Suitably, the superconducting wire is arranged longitudinally on the radially outer surface of the conductor connecting sleeve or is helically wound thereon and soldered thereon.

In still another aspect, the present invention provides a superconducting cable joint structure for jointing a superconducting cable used at a cryogenic temperature or jointing a terminal of the superconducting cable with a general conductive cable. This structure includes: a conductor connection portion which allows the respective conductors in the cable to abut against each other, to be welded and to be electrically connected together, or allows the superconducting cable and the respective conductors in the ordinary conducting cable to abut against each other, to be welded and to be electrically connected together; a superconducting wire disposed on a circumference of the conductor connecting part in a longitudinal direction or wound thereon to reduce heat generation; and a joint insulating layer disposed radially outside the superconducting wire.

Since the superconducting wire attached to the outer or inner surface of the conductor connecting sleeve has a significantly smaller resistance than the connecting sleeve, the current from the superconducting layer in the core of the cable will tend to flow through the wire rather than the connecting sleeve. Thereby, less heat can be generated. Also, at the conductor connection, current tends to flow through the superconducting wire rather than the conductor connection sleeve because the wire has a lower resistance than the conductor connection sleeve. In general, the superconducting cable can be prevented from having a small current capacity.

Preferably, in the structure, the joint insulating layer has at least one coolant passage. This is also preferred as a way of resisting heat, since a synergistic effect of dissipating heat through the coolant channels is achieved, possibly in interaction with the effect of reducing heat generation.

The superconducting cable and the ordinary conducting cable have a conductor connecting portion so that the superconducting cable has a conductor protruding therefrom, the superconductor and the conductor in the superconducting cable are connected together via the conductor connecting portion while the joint insulating layer is provided radially outside the conductor connecting portion, and further, an end face of the joint insulating layer and an outer end face of the ordinary conducting cable are connected together to form a boundary portion with a coolant passage. This is preferable because the coolant passage is allowed to be easily formed, and the conductor connection portion can also be prevented from overheating.

The superconducting cable includes: a cable core having a sizing tube made of long fibers; a superconducting layer spirally wound around the sizing tube in a plurality of layers; and an insulating layer located radially outside the superconducting layer. The cable core has a terminal with a stepped exposed sizing tube and a superconducting layer, and the conductor connecting sleeve has a radially inner surface and an outer surface, and a superconducting wire is embedded therein to reduce heat generation, and is connected to the stepped exposed sizing tube and the superconducting layer. The superconducting layers exposed in the stepped shape allow the conductor connecting sleeve to form a stable electrical connection with the superconducting layer of each layer.

As a specific configuration, the aforementioned structure has more than one cable cores connected to each other, each having a shielding layer with a superconducting wire disposed radially outside the insulating layer and a shield layer made of an insulator and disposed radially outside the shielding layer, the superconducting layer in the cable core and the superconducting layer in another cable core or the conductor in a normal conducting cable being connected together via a conductor connecting portion, the conductor connecting portion being covered with a joint insulating layer.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when read in conjunction with the accompanying drawings.

Drawings

In the drawings:

fig. 1A is a cross-sectional view of a superconducting cable in one embodiment, fig. 1B is a perspective view of a core of the cable, and fig. 1C is a perspective view of a superconductor;

fig. 2A is a longitudinal cross-sectional view showing a manner of connecting cores in the superconducting cable in the first embodiment, and fig. 2B is a cross-sectional view orthogonal thereto;

fig. 3 to 5 are longitudinal cross-sectional views showing the manner of connecting the cores in the superconducting cable in the second to fourth embodiments, respectively;

FIG. 6 is a cross-sectional view showing an example of a modification of the fourth embodiment;

fig. 7 is a longitudinal cross-sectional view showing a manner of connecting cores in the superconducting cable in the fifth embodiment;

FIG. 8 is a cross-sectional view showing an example of a modification of the fifth embodiment;

fig. 9 and 10 are two longitudinal cross-sectional views showing the manner of connecting the cores in the superconducting cable in sixth and seventh embodiments, respectively; while

Fig. 11 is a cross-sectional view of a conventional example.

Detailed Description

Embodiments of the present invention are described below with reference to the drawings.

Referring to fig. 1A, the present embodiment provides a superconducting cable 100 comprising, as seen in a radially outward direction, an inner corrugated tube 15, an insulating layer 16, an outer corrugated tube 17, and an anti-corrosion layer 18, which are layered to form a cylindrical body, so as to form an outer shell 70 serving as an insulating conduit. The sheath 70 has an inner space 71, the inner space 71 serving as a coolant layer R, and three cable cores 10 passing therethrough. The inner bellows 15 and the outer bellows 17 are corrugated cylinders made of stainless steel, and the anti-corrosion layer 18 is made of, for example, polyvinyl chloride (PVC). The coolant layer R uses a coolant such as liquid nitrogen or liquid helium.

As shown in fig. 1A and 1B, the cable core 10 includes: a sizing tube 11, the sizing tube 11 being made of copper wires twisted together and placed in the middle of the core; a superconducting layer 12, the superconducting layer 12 being made of a superconductor spirally wound around the sizing tube 11; and an insulating layer 13 having a shield layer and a shield layer (not shown) wound around the outer periphery of the superconducting layer 12.

The sizing tube 11 is made of a plurality of copper wires that form an insulated conductor bundle twisted together to maintain the mechanical properties (rigidity, bending characteristics, and the like) of the cable core 10 and also reduce eddy current loss in the sizing tube. Also, since the superconducting layer 12 is wound around the outer periphery of the sizing tube 11 and the resistance of the superconducting layer 12 is very low, current tends to flow through the superconducting layer 12 instead of the sizing tube 11. It should be noted, however, that if eddy currents are present and exceed a critical value Ic, the resistance of the superconducting layer 12 will increase and the sizing tube 11 will also pass the current and act as a bypass for safety reasons. The sizing pipe 11 may also be made of a metal other than copper.

As shown in fig. 1C, the superconducting layer 12 is made of a wire in the form of a strip made of bismuth (Bi) -2223, superconducting fibers 12b, and silver 12a (or an alloy of silver) covering the fibers. The superconducting fibers 12b may be made of ceramics, such as yttrium oxide, thallium oxide, bismuth oxide.

The insulating layer 13 is made of polypropylene laminated paper (PPLP) formed of a polypropylene film, to at least one surface of which kraft paper is bonded. The insulating layer 13 is impregnated with a coolant and is in a low temperature insulating system. Alternatively, the insulating layer 13 may be a sheet of paper made of, for example, a polyethylene film, a polypropylene film, or the like combined together.

The shield layer 14 is constructed similarly to the superconducting layer 12, and a current flows in a direction opposite to the superconducting layer 12 to cancel the magnetic field.

As will be described later, the superconducting cable 100 has the cable core 10 combined and connected in the first embodiment.

First embodiment

Referring to fig. 2A, the present embodiment provides a superconducting cable joint structure 52. More specifically, two opposed cable cores 10 have their respective sizing tubes 11 and superconducting layers 12 exposed in a stepped manner so that they can be connected to conductor connection sleeves 19. The sizing tubes 11 abut against each other, while the conductor connecting sleeves 19 are fitted and connected outside to form a conductor connection 22, wherein the conductor connecting sleeves 19 are formed as a metal cylinder (for example copper, aluminum or the like).

The conductor connecting sleeve 19 and the superconducting layer 12 are electrically connected by, for example, solder, and the conductor connecting sleeve 19 and the sizing tube 11 are press-connected.

The conductor connecting sleeve 19 is covered with a first coolant-impregnated paper 20A and a second coolant-impregnated paper 20B wound therearound to serve as a joint insulating layer 20. Similar to the insulating layer 13, the first coolant-impregnated paper 20A and the second coolant-impregnated paper 20B may also be made of polypropylene laminated paper (PPLP) formed of a polypropylene film, to at least one surface of which kraft paper is bonded, or may be kraft paper.

More specifically, as shown in fig. 2A, the conductor connecting sleeve 19 is wound with a first coolant-impregnated paper 20A divided into two in the longitudinal direction, and as shown in fig. 2B, washers 21 are provided on the radially outer surface of the first coolant-impregnated paper 20A at intervals in the circumferential direction, and a second coolant-impregnated paper 20B thereon is wound on these washers 21 to form the joint insulating layer 20 having one coolant passage S.

It is to be noted that one end portion of the joint insulating layer 20 is provided with a side surface 20c inclined so that it does not form a right angle with respect to the longitudinal direction of the cable core 10 and thus smoothly abuts the cable core.

If the side surface 20e forms a right angle with respect to the longitudinal direction of the cable and thus forms a significantly inclined portion, the voltage applied to the superconducting layer 12 can enhance the electric field formed at the boundary of the joint insulating layer 20 and the side surface 20c, and the equipotential surfaces surrounding the electric field formed therein will not remain parallel at the significantly inclined portion, resulting in the electric field exceeding the critical value. The end of the joint insulating layer 20 is provided with a side surface 20c smoothly abutting the cable core 10, which can effectively attenuate the electric field at the boundary.

Also, as shown in fig. 2, the coolant passage S has a horizontal portion Sa and an inclined portion Sb. The horizontal portion Sa has an end portion communicating with the coolant layer R, and the inclined portion Sb also has an end portion abutting the outer surface of the conductor connecting sleeve 19.

In other words, the coolant passage S has an inclined passage Sb that connects the radially inner opening S1 of the coolant passage S with the radially outer opening S2 of the coolant passage S. The radially inner opening S1 is located at the conductor connecting sleeve 19 along the radially outer surface 19a, wherein the radially outer surface 19a is in direct contact with the coolant. The portion Sb is inclined with respect to the longitudinal direction of the cable core 10, not perpendicular thereto, for the same reason as the side surface 20c is inclined.

Thus, opposed cable cores 10 have their respective conductive layers 12 joined together by a common conductor or conductor connection sleeve 19 fitted on the outside thereof. Although the connection sleeve 19 generates heat, the coolant of the coolant layer R corresponding to the inner space 71 of the inner bellows 15 may flow into the coolant passage S formed in the joint insulating layer 20, and the heat generated at the connection sleeve 19 may be diffused to the coolant layer R by convection of the coolant in the coolant passage S, thereby preventing the connection sleeve 19 from overheating.

It is to be noted that, as shown in fig. 2B, although more than one coolant passage S is circumferentially provided in the present embodiment, any number of coolant passages may be provided. For example, only one coolant passage may be provided. Also, the gasket 21 is suitably interposed between the insulating layers 20A and 20B formed of the coolant-impregnated paper wound in layers. However, it may be disposed between the radially outer surface of the cable core 10 and the joint insulating layer 20. Also, the joint insulating layer 20 may be an insulating resin mold.

Second embodiment

Referring to fig. 3, the present embodiment differs from the first embodiment in that the present embodiment provides a superconducting cable joint structure 53 including a joint insulation layer 20 ', the insulation layer 20' including a coolant passage S 'extending along the cable core 10 as viewed in the longitudinal direction, and the coolant passage S' communicating at a portion adjoining the conductor connection sleeve 19.

The coolant passage S ' has a horizontal portion Sa ' having one end Sf ' communicating with the coolant layer R; an inclined portion Sb 'communicating with the horizontal portion Sa' and having an end abutting the conductor connecting sleeve 19 at the radially outer surface 19 a; a horizontal portion Sd 'having one end Sg' in communication with the coolant layer R; an inclined portion Se 'communicating with the horizontal portion Sd' and having an end abutting the connection sleeve 19 at the surface 19 a; and a communicating portion Sc ' allowing respective ends of the opposed inclined portions Sb ' and Se ' to communicate with each other.

More specifically, the conductor connecting sleeve 19 is wound with a first coolant-impregnated paper 20A divided into two parts as seen in the longitudinal direction. Subsequently, the first coolant-impregnated paper 20A is provided on the radially outer surface thereof with washers arranged in a circumferentially spaced manner, and the second coolant-impregnated paper 20B' is wound thereon. A joint insulating layer 20 'having a coolant channel S' is thus formed. In this process, it is also necessary to provide a gasket between the ends of the inclined portions Sb 'and Se' on the outer surface of the connecting sleeve 19 so that the gaskets are arranged circumferentially and at intervals, and to wind the second coolant impregnated paper 20B 'therearound to allow the communicating portion Sc' to be formed horizontally and to abut the connecting sleeve 19 at the surface 19 a.

The foregoing arrangement allows the coolant present in the coolant layer R outside the joint insulating layer 20 'to flow into the coolant channel S' at one end Sg 'and flow out at the other end Sf'. The coolant thus circulates through the coolant passage S' to more efficiently cool the connecting sleeve 19.

The remaining configuration in this embodiment is similar to that in the first embodiment.

Third embodiment

In the present embodiment, a description will be given of a structure in which a terminal of a superconducting cable is joined together with a resin unit for fixing a general conductive cable.

Referring to fig. 4, the present embodiment is different from the first embodiment in that the present embodiment provides a superconducting cable joint structure 54 for connecting a cable core 10 in a superconducting cable 100 to a conductor 31 in a resin unit 33, wherein the resin unit 33 is used for fixing a general conductive cable to an external member.

In the resin unit 33, a conductor 31 made of aluminum and copper is surrounded by a fixed portion of an insulator 32, wherein the insulator 32 is made of epoxy resin and has a rhomboid cross section. One end of the fixed portion of the insulator 32 is provided with a conductor 31 protruding and exposed therefrom, and the conductor 31 has one end, i.e., a connection portion 31a, which is fitted to the outside of the superconducting layer 12 in the cable core 10 and is thereby connected thereto.

The outer surface of the conductor connecting sleeve 19 and the side surface 32a of the end of the fixed portion of the insulator 32 are coated with coolant-impregnated papers 30A and 30B wound therearound to form a joint insulating layer 30. The interface of the joint insulating layer 30 and the common conductive cable 33 is inclined with respect to the longitudinal direction of the cable core 14, and is provided with a coolant passage S1.

More specifically, the side surface 32a is provided with washers (not shown) spaced along the circumference of the cable core 10, and the first coolant-impregnated paper 30A is wound around the conductor 31 to serve as a protrusion of the conductor connecting portion 22, and thereby covers the protrusion. Next, the first coolant-impregnated paper 30A is also provided with spaced-apart washers (not shown) in the outer circumferential direction, and the second coolant-impregnated paper 30B is wound thereon to form the bonding insulation layer 30. In other words, the joint insulating layer 30 and the fixed portion on the insulator 32 have an interface with the first coolant passage S1 communicating with the coolant layer R, and the joint insulating layer 30 is internally provided with the second coolant passage S2 such that the first coolant passage S1 communicates with the end portion of the conductor 31, i.e., the connection portion 31 a.

The second coolant passage S2 has a horizontal portion S2b communicating with the first coolant passage S1, and an inclined portion S2a abutting the conductor 31 at the end, i.e., the connecting portion 31 a. It is to be noted that, although the first coolant passage S1 has one end portion communicating with the conductor 31, it is only necessary to communicate with at least the second coolant passage S2. It is not necessary to make the first coolant passage S1 communicate with the conductor 31.

Thereby, the coolant layer R located outside the cable core 10 can cause the coolant to flow into the second coolant passage S2 through the first coolant passage S1, so that the heat generated at the end of the conductor 31, i.e., the connection portion 31a, can be diffused to the coolant layer R through the first coolant passage S1 and the second coolant passage S2 to prevent the conductor connection portion 22 from overheating.

Although the fixing portion on the insulator 32 is preferably made of epoxy resin when heat resistance, dimensional stability and adhesiveness are considered, it is not limited to a specific material as long as it exhibits high heat resistance, a small percentage of shrinkage with curing (or high dimensional stability) and superior adhesiveness. Also, the conductor 31 in the resin unit 32 may be a superconductor.

A fourth embodiment.

Referring to fig. 5, the present embodiment provides a superconducting cable joint structure 55 including a conductor connection sleeve 19, the connection sleeve 19 having a radially outer surface with a superconducting wire 41 spirally wound thereon and welded thereto to reduce heat generation. No coolant passage is provided in the joint insulating layer 40. Superconducting wire 41 is similar in construction to superconducting layer 12 shown in fig. 1C, and may be wound either densely or sparsely. Opposite end 41a of superconducting wire 41 abuts cable core 10 at superconducting layer 12. Thereby, the opposite end portions of the superconducting wire 41 are electrically connected to the sizing pipe 11 in each of the two connected superconducting cables 100.

Thus, the opposed cable core 10 has its respective superconducting layers 12 and sizing tubes 11 connected by an externally fitted conductor connection sleeve 19, which conductor connection sleeve 19 has a radially outer surface with superconducting wires 41 connected thereto. Since superconducting wire 41 has a lower resistance than conductor connection sleeve 19, current will tend to flow through wire 41 rather than connection sleeve 19. The connecting sleeve 19 can thus generate less heat.

Although the superconducting wire 41 is spirally wound in the present embodiment, the wire 41 may be simply provided on the radially outer surface 19a of the conductor connecting sleeve 19 in the longitudinal direction (or in the longitudinal direction of the cable core 10). Alternatively, the wire 41 may simply be embedded in the conductor connecting sleeve 19. Also, the wire 41 need not have its end in contact with the superconducting layer 12. Note that although the wire 41 is soldered to the superconducting layer 12 in this embodiment, the wire 41 may be simply embedded with the winding of the bonding insulating layer 40. Alternatively, the wires 41 may be arranged radially inside the connection sleeve 19.

The remaining configuration in this embodiment is similar to that in the first embodiment.

Although the present embodiment has been described in connection with the superconducting-cable joint structure 55 for connecting superconducting cables together, the present invention is also applicable to a superconducting-cable joint structure for connecting a superconducting cable and a general conductive cable together.

Further, referring to fig. 6, the present embodiment provides another superconducting cable joint structure 56 in which the first coolant-impregnated paper 40A divided into two parts as viewed in the longitudinal direction is wound and thus covered on the superconducting wires 41, the superconducting wires 41 are disposed on the radially outer surfaces 19a of the conductor connection sleeves 19, and the outer surfaces of the cable cores 10 are abutted thereto. Also, the first coolant-impregnated paper 40A is circumferentially surrounded from the outside by spaced-apart washers (not shown), and the second coolant-impregnated paper 40B is wound around these washers. Thus, joint insulation layer 40' with coolant channels S allows outer coolant layer R to communicate with superconducting wire 41, where superconducting wire 41 is disposed at radially outer surface 19a of conductor connection sleeve 19.

Thereby, the coolant located outside the joint insulating layer 40' can flow into the coolant passage S. If the conductor connecting sleeve 19 and the superconducting wire 41 generate heat, the coolant passage S allows this heat to diffuse into the coolant. This provides an efficient way of counteracting the heat synergy as it interacts with the heat reducing effect due to the provision of superconducting wire 14 for the connection sleeve 19.

Fifth embodiment

Referring to fig. 7, the present embodiment provides a superconducting cable joint structure 57. More specifically, the sizing tubes 11 of the opposing cable cores 10, which abut each other, are welded and thereby joined together. Also, the sizing pipe 11 and the superconducting layer 12 have an outer surface with the superconducting wire 51 spirally wound therearound and are soldered or similarly connected to the superconducting layer 12 to establish electrical connection. Further, a coolant-impregnated paper is spirally wound on the radially outer side thereof to form a joint insulating layer 50.

Thus, the opposing cable cores 10 have their respective superconducting layers 12 electrically connected by the superconducting wire 51. The electrical connection can be realized with a resistor having a smaller resistance value, so that the connection part can generate less heat. Also, since the superconducting wire 51 for forming the electrical connection has a small rigidity, the sizing pipes 11 having a sufficient rigidity can be welded and connected together, so that the connection can maintain a constant strength.

It is to be noted that, although the superconducting wire 51 is spirally wound in the present embodiment, the superconducting wire 51 may be simply disposed on the outer surfaces of the superconducting layer 12 and the sizing pipe 11 in the longitudinal direction. Also, although the wire 51 is soldered to the superconducting layer 12 in the present embodiment, the wire 51 may be embedded simply by the force of the joining insulating layer 50 wound therearound.

The remaining configuration in this embodiment is similar to that in the first embodiment.

Still referring to fig. 8, the present embodiment provides another superconducting cable joint structure 58. More specifically, the superconducting wire 51 and the cable core 10 adjacent thereto have an outer surface covered with a first coolant-impregnated paper 50A, the coolant-impregnated paper 50A being divided into two parts as viewed in the longitudinal direction and wound around the outer surface. The first coolant-impregnated paper 50A is provided with spaced-apart washers (not shown) circumferentially on the outer side, and the second coolant-impregnated paper 50B is wound around these washers. Thus, joint insulation layer 50' having coolant channel S allows outer coolant layer R to communicate with superconducting wire 51.

Thereby, the coolant outside the joint insulating layer 50' can flow into the coolant passage S. If superconducting wire 51 generates heat, coolant channel S allows this heat to diffuse into the coolant. This provides a sufficient path for the efficiency of the heat resistance, since it interacts with the heat reducing effect due to the use of superconducting wire 51.

Sixth embodiment

Referring to fig. 9, the present embodiment differs from the third embodiment as follows: the present embodiment provides a superconducting cable joint structure 59 in which a fixing resin unit 33 'corresponding to a general conductive cable has a conductor 60 with a superconductor 61 spirally wound therearound, and the superconductor 61 of the resin unit 33' and the superconducting layer 12 of the cable core 10 are joined together by a conductor joint sleeve 19 fitted outside, and further, a superconducting wire 41 is spirally wound on the outer surface of the conductor joint sleeve 19.

More specifically, in the resin unit 33', the conductor 60 made of aluminum or copper is surrounded by the superconductor 61 spirally wound therearound, and the superconductor 61 is also surrounded by the fixed portion on the insulator 32, wherein the insulator 32 is made of epoxy resin and has a rhomboid cross section. One end of the fixed portion of the insulator 32 is provided with a conductor 60 and a superconductor 61 projecting in a step shape.

The conductor 60 has an end abutting on the cable core 10 at the sizing tube 11, and the superconductor 61 and the superconducting layer 12 are connected together by a conductor connecting sleeve 19, which connecting sleeve 19 is fitted from the outside and on the radial outer surface 19a of which the superconducting wire 41 is helically wound, the superconducting wire 41 being welded and thereby connected thereto.

One end of the fixed portion on the insulator 32 has a side surface 32a, the side surface 32a is provided with circumferentially spaced washers (not shown), and a first coolant-impregnated paper 30A is wound to cover the conductor connecting sleeve 19 with the superconducting wire 41. Further, the first coolant-impregnated paper 30A is circumferentially surrounded from the outside by a gasket (not shown), and the second coolant-impregnated paper 30B is wound thereon to form the joint insulating layer 30. Thus, the interface 63 of the joint insulating layer 30 and the fixed portion on the insulator 32 is provided with the first coolant passage S1 communicating with the coolant layer R, and the joint insulating layer 30 is provided internally with the second coolant passage S2 for communicating the first coolant passage S1 with the superconducting wire 41.

The remaining configuration in the present embodiment is similar to that in the third embodiment.

Seventh embodiment

Referring to fig. 10, the present embodiment is different from the sixth embodiment in that the present embodiment provides a superconducting cable joint structure 66 in which a conductor 60 of a fixing resin unit 33' and a sizing tube 11 of a cable core 10 are abutted against each other and welded together, and the sizing tube 11, a superconductor 61, and a superconducting layer 12 have an outer surface on which a superconducting wire 51 is spirally wound, and the superconducting wire 51 is welded or similarly connected to the superconducting layers 12, 61 to form an electrical connection.

Further, as in the third and sixth embodiments, the first coolant-impregnated paper 30A and the second coolant-impregnated paper 30B are wound to form the joint insulating layer 30 having the second coolant passage S2 and the first coolant passage S1.

The remaining configuration in this embodiment is the same as that in the third embodiment.

According to the present invention, as apparent from the foregoing description, the conductor connecting portion of the superconducting cable is provided at the outside thereof with a joint insulating layer provided with a coolant passage, so that heat generated at the conductor connecting portion can be dissipated by the coolant flowing into the coolant passage to prevent the conductor connecting portion from being overheated. Furthermore, at the conductor connection, the conductors can be connected together by a superconducting wire fitted on the outside and provided with a conductor connection sleeve, or directly by a superconducting wire, so that the joint generates less heat.

Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

Claims (9)

1. A joint structure (55, 56, 59) of a superconducting cable for joining together a superconducting cable (100) for use at a cryogenic temperature or joining together a terminal of the superconducting cable (100) and a general conductive cable (33'), the structure comprising:

a conductor connection portion (22) that allows the cable (100) to have their respective conductors (11) abut against and be connected together, or allows the superconducting cable (100) and the normal conduction cable (33') to have their respective conductors (11, 60) abut against and be connected together;

a conductor connecting sleeve (19) which is connected with the periphery of the conductor connecting part (22) in a pressing way;

a superconducting wire (41) which is arranged on the radial outer surface of the conductor connecting sleeve (19) or is embedded inside the conductor connecting sleeve (19) to reduce the generation of heat; and

a joint insulation layer (40, 40', 30) provided on the outer periphery of the conductor connection sleeve (19) or the superconducting wire (41),

wherein the joint insulating layer has at least one coolant channel therein.

2. The joint structure (55, 59) of a superconducting cable according to claim 1, wherein the superconducting wire (41) has its opposite ends electrically connected to the conductor (11) of each of two superconducting cables (100) to be connected together, or to the conductor (11) of the superconducting cable (100) to be connected together and the conductor (60) of the ordinary conducting cable (33').

3. The joint structure (55, 59) of a superconducting cable according to claim 1, wherein: the superconducting wire (41) is disposed longitudinally on a radially outer surface (19a) of the conductor connecting sleeve (19) or is helically wound around the conductor connecting sleeve and welded thereto.

4. A joint structure (59) of a superconducting cable as claimed in claim 1, wherein: the superconducting cable (100) and the ordinary conducting cable (33 ') have the conductor connecting portion (22) so that the ordinary conducting cable (33 ') has a conductor (60) protruding therefrom, the superconductor (60) and the conductor (11) of the superconducting cable (100) are connected together via the conductor connecting portion (22) with the joint insulating layer (30) disposed radially outside the conductor connecting portion (22), and further, an end face of the joint insulating layer (30) and an outer end face of the ordinary conducting cable (33 ') are connected together to form a boundary portion (63), and the boundary portion (63) is provided with a coolant passage (S).

5. The joint structure (59) of a superconducting cable according to claim 1, wherein:

the superconducting cable (100) has a cable core (10);

the cable core (10) has a sizing tube (11) made of a long fiber, a superconducting layer (12) spirally wound around the circumference of the sizing tube (11) in a multi-layer form, and an insulating layer (13) disposed radially outside the superconducting layer (12); and is

The cable core (10) has a terminal with the sizing tube (11) and the superconducting layer (12) exposed in a stepped shape, and the superconducting wire (41) embedded in the conductor connecting sleeve (19) is connected to the sizing tube (11) and the superconducting layer (12) exposed in a stepped shape at a radially inner surface or a radially outer surface.

6. The joint structure (52) of a superconducting cable according to claim 1, wherein:

the superconducting cable (100) has more than one cable cores (10) connected to each other, each of the cable cores (10) having a shielding layer (14) with a superconducting wire arranged at an outer periphery of the insulating layer (13) and a shield layer (49), the shield layer (14) being made of an insulator and arranged on an outer periphery of the shielding layer (14); and is

The superconducting layer (12) of the cable core (10) and the superconducting layers (12) of a plurality of other cable cores (10) or the conductors (60) of the ordinary conductive cables (33') are connected together via the conductor connecting portions (22), the conductor connecting portions (22) being covered with the joint insulating layer (20).

7. A joint structure (57, 58, 66) of a superconducting cable for joining together a superconducting cable (100) for use at a cryogenic temperature or joining together a terminal of the superconducting cable (100) and a general conductive cable (33'), the structure comprising:

a conductor connection portion (22) that allows the cable (100) to have their respective conductors abutted against, welded to, and electrically connected together, or the superconducting cable (100) and the ordinary conducting cable (33') to have their respective conductors (11, 60) abutted against, welded to, and electrically connected together;

a superconducting wire (51) that is disposed on an outer periphery of the conductor connecting portion (22) in a longitudinal direction or is wound around the conductor connecting portion to reduce generation of heat; and

a joint insulation layer (50, 50', 30) arranged radially outside the superconducting wire (51),

wherein the joint insulating layer has at least one coolant channel therein.

8. The joint structure (66) of a superconducting cable according to claim 7, wherein: the superconducting cable (100) and the ordinary conducting cable (33 ') have the conductor connecting portion (22) so that the ordinary conducting cable (33 ') has a conductor (60) protruding therefrom, the superconductor (60) and the conductor (11) of the superconducting cable (100) are connected together via the conductor connecting portion (22) while the joint insulating layer (30) is disposed radially outside the conductor connecting portion (22), and further, an end face of the joint insulating layer (30) and an outer end face of the ordinary conducting cable (33 ') are connected together to form a boundary portion (63), the boundary portion (63) being provided with a coolant passage (S).

9. The joint structure (58, 66) of a superconducting cable of claim 7, wherein:

the superconducting cable (100) has more than one interconnected cable cores (10), each cable core (10) having a shielding layer (14) with superconducting wires arranged radially outside the insulating layer (13) and a shielding layer (49), the shielding layer (14) being made of an insulator and being arranged radially outside the shielding layer (14); and is

The superconducting layer (12) of the cable core (10) and the superconducting layer (12) of another cable core (10) or the conductor (61) of the ordinary conductive cable (33') are connected together via the conductor connecting portion (22), the conductor connecting portion (22) being covered with the joint insulating layer (20).