JP2020028134A - Terminal structure of superconducting cable - Google Patents

Abstract

To provide a terminal structure of a superconducting cable capable of shortening length of a porcelain tube body while capable of effectively relaxing the electric field of an insulation part of a bushing.SOLUTION: A terminal structure of a superconducting cable comprises a cable core, a bushing inserted into the cable core, a porcelain tube accommodating a normal temperature side area of the bushing, a conductor extraction part connected with an end of the cable core, and an inner vacuum insulation pipe provided so as to extend to the normal temperature side through the porcelain tube. The bushing has an insulation part and a stationary part formed at the circumference of the insulation part. The porcelain tube has a body part with an electric field control surface, a lower metal fitting attached to the stationary part of the bushing, and an upper metal fitting inserting-fixing a normal temperature side end of the inner vacuum insulation pipe. The normal temperature side end of the inner vacuum insulation pipe has a step part. While the insulation part of the normal temperature side area of the bushing is arranged so as to be overlapped with the electric field control surface of the body part of the porcelain tube in a radial direction, The step part of the inner vacuum insulation pipe is positioned nearer than the electric field control surface to the normal temperature side.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a terminal structure of a superconducting cable.

  A superconducting cable is expected as a power cable constituting a transmission line because it can transmit a large amount of power with low loss as compared with an existing normal conducting cable (eg, an OF cable or a CV cable). Generally, a superconducting cable has a structure in which a cable core having a superconducting conductor layer on the outer periphery of a former is housed in a heat insulating tube, and a refrigerant (for example, liquid nitrogen or liquid helium) is placed in the heat insulating tube (between the cable core and the heat insulating tube). ) To cool the cable core (superconducting conductor layer) to maintain the superconducting state.

  When a power transmission line is constructed using a superconducting cable, a terminal for connecting to a normal conductive power device is provided at the end of the superconducting cable. Patent Literature 1 discloses that a cable core pulled out from a heat-insulating tube end of a superconducting cable, a bushing through which the cable core is inserted, an insulator tube accommodating a room-temperature region of the bushing, and a superconducting conductor layer of the cable core are connected. A terminal structure of a superconducting cable including a normal conducting lead-out portion is disclosed. In the terminal structure described in Patent Literature 1, a coolant that cools the superconducting conductor layer is provided from the end of the heat-insulating tube to the connection point between the superconducting conductor layer and the normal conducting lead portion through the inside of the insulator tube. A vacuum layer (a vacuum layer on the cable side, a vacuum layer on the inside, and a vacuum layer on the normal temperature side) for heat insulation is provided.

JP 2015-192552 A

  In the terminal structure of the superconducting cable, improvement in installation and workability is desired, and as one of them, it is required to reduce the length of the entire terminal in the longitudinal direction. However, heretofore, it has not always been said that sufficient consideration has been given to shortening the dimensions of the insulator tube while sufficiently considering the electric field control of the bushing.

  Therefore, an object of the present disclosure is to provide a terminal structure of a superconducting cable that can effectively reduce the electric field of an insulating portion in a bushing and that can shorten the length of an insulator tube main body.

The terminal structure of the superconducting cable according to the present disclosure,
A cable core protruding from the end of the heat insulating tube at the end of the superconducting cable,
A bushing through which a part of the cable core is inserted;
A porcelain tube for accommodating a room temperature side region in the bushing;
At the end of the cable core protruding from the room temperature side end of the bushing, a conductor extraction portion to which a superconducting conductor layer provided in the cable core is connected,
An inner vacuum heat insulating pipe that is provided so as to extend from the inner circumference of the bushing and the outer circumference of the cable core to the room temperature side through the inside of the insulator tube, and insulates and retains a refrigerant that cools the superconducting conductor layer of the cable core. ,
The bushing has an insulating portion having a normal-temperature side region tapered toward an end, and a fixing portion provided at an intermediate portion of the insulating portion and formed on an outer periphery of the insulating portion,
The insulator tube includes a cylindrical main body having an electric field control surface on which a plurality of insulators are formed, a lower fitting provided at a cable side end of the main body, to which the fixing portion of the bushing is attached, An upper fitting provided at a normal temperature side end of the section and through which the normal temperature side end of the inner vacuum heat insulating tube is inserted and fixed,
At the room temperature side end of the inner vacuum heat insulating tube, there is a step portion where the outer diameter is locally increased,
The insulating portion in the room temperature side region of the bushing is radially overlapped with the electric field control surface of the main body in the insulator tube, and the step portion of the inner vacuum heat insulating tube is connected to the electric field control surface. It is located on the normal temperature side.

  The terminal structure of the superconducting cable can reduce the length of the insulator tube main body while effectively reducing the electric field of the insulating portion in the bushing.

FIG. 2 is a schematic longitudinal sectional view illustrating a terminal structure of the superconducting cable according to the first embodiment. It is the elements on larger scale which expand and show the principal part of the terminal structure of the superconducting cable shown in FIG. FIG. 4 is a diagram schematically illustrating a distribution of equipotential lines in a room temperature side region of the bushing according to the first embodiment. It is a schematic perspective view which shows an example of a superconducting cable.

[Description of Embodiment of the Present Disclosure]
In order to sufficiently exhibit the insulating performance of the bushing, it is necessary to reduce the concentration of the electric field in the insulating portion. In a conventional terminal structure, a bushing is housed in a porcelain tube in order to prevent the electric field between the high voltage side, which is a high potential, and the ground side, which is a low potential (ground potential), from being locally concentrated. , The insulation performance is enhanced.

  In the terminal structure of the superconducting cable, in order to reduce thermal shrinkage during cooling, for example, an inner vacuum layer (inner vacuum heat insulating pipe) provided so as to extend from the space between the bushing and the cable core to the room temperature side through the insulator tube. It is conceivable to insert a bellows tube partially. In this case, the outer diameter of the portion of the inner vacuum heat insulating tube into which the bellows tube is inserted becomes locally large, and a step is formed. If such a step is formed in the inner vacuum heat insulating pipe, an electric field (equipotential line) generated in the bushing (insulating section) may intersect the step depending on the position of the step, and the insulating section Electric field may not be sufficiently reduced. Therefore, if there is a step, to make it easier to control the electric field of the bushing, increase the distance between the bushing and the step to prevent the electric field generated in the insulating part from intersecting the step. Can be considered. However, if the distance between the bushing and the step portion is simply increased, there is a problem that the length of the insulator tube becomes longer and it becomes difficult to shorten the entire length of the terminal.

  Hereinafter, embodiments of the present disclosure will be listed and described.

(1) The terminal structure of the superconducting cable according to the embodiment of the present disclosure is as follows:
A cable core protruding from the end of the heat insulating tube at the end of the superconducting cable,
A bushing through which a part of the cable core is inserted;
A porcelain tube for accommodating a room temperature side region in the bushing;
At the end of the cable core protruding from the room temperature side end of the bushing, a conductor extraction portion to which a superconducting conductor layer provided in the cable core is connected,
An inner vacuum heat insulating pipe that is provided so as to extend from the inner circumference of the bushing and the outer circumference of the cable core to the room temperature side through the inside of the insulator tube, and insulates and retains a refrigerant that cools the superconducting conductor layer of the cable core. ,
The bushing has an insulating portion having a normal-temperature side region tapered toward an end, and a fixing portion provided at an intermediate portion of the insulating portion and formed on an outer periphery of the insulating portion,
The insulator tube includes a cylindrical main body having an electric field control surface on which a plurality of insulators are formed, a lower fitting provided at a cable side end of the main body, to which the fixing portion of the bushing is attached, An upper fitting provided at a normal temperature side end of the section and through which the normal temperature side end of the inner vacuum heat insulating tube is inserted and fixed,
At the room temperature side end of the inner vacuum heat insulating tube, there is a step portion where the outer diameter is locally increased,
The insulating portion in the room temperature side region of the bushing is radially overlapped with the electric field control surface of the main body in the insulator tube, and the step portion of the inner vacuum heat insulating tube is connected to the electric field control surface. It is located on the normal temperature side.

  According to the terminal structure of the superconducting cable, the step portion provided at the room temperature side end of the inner vacuum heat insulating tube is located at the room temperature side of the electric field control surface of the insulator tube, so that the bushing (insulating portion) is at the room temperature side. It is possible to prevent the equipotential lines generated in the region from intersecting the step. Therefore, the equipotential lines generated in the insulating portion mainly pass through the electric field control surface of the insulator tube, and the distribution of the equipotential lines is made uniform over the entire length of the electric field control surface. As a result, the potential distribution on the surface of the insulator is equalized, the electric field in the insulating portion can be effectively reduced, and the surface of the insulator can be used effectively. Further, since the surface of the insulator can be effectively used, the length of the insulator tube main body can be reduced. Therefore, the terminal structure of the superconducting cable can shorten the length of the insulator tube main body while effectively reducing the electric field of the insulating portion in the bushing, thereby making it possible to shorten the entire length of the terminal. is there.

  (2) As one mode of the terminal structure of the superconducting cable, a bellows pipe may be provided at the step portion of the inner vacuum heat insulating pipe.

  Since the bellows pipe is provided at the step portion of the inner vacuum heat insulating pipe, the bellows pipe can absorb heat shrinkage during cooling.

  (3) As one mode of the terminal structure of the superconducting cable, a non-vacuum heat-insulating layer that covers the outer periphery of the conductor lead-out portion is provided, and the non-vacuum heat-insulating layer is formed of a heat insulating material.

  By providing the non-vacuum heat insulating layer on the outer periphery of the conductor lead-out portion, heat intrusion from the outside can be suppressed, and heat intrusion into the superconducting conductor layer from the conductor lead-out portion can be reduced. Further, since the non-vacuum heat-insulating layer has a heat-insulating structure formed of a heat-insulating material, it has a simpler structure than a heat-insulating structure using a vacuum layer (vacuum heat-insulating layer), is excellent in workability, and can reduce cost.

[Details of Embodiment of the Present Disclosure]
A specific example of a terminal structure of a superconducting cable according to an embodiment of the present disclosure will be described below with reference to the drawings. The same reference numerals in the drawings indicate the same names.

[Embodiment 1]
<Overview of terminal structure of superconducting cable>
The terminal structure 1 of the superconducting cable according to the first embodiment will be described with reference to FIGS. The terminal structure 1 shown in FIG. 1 is a conductor drawing for electrically connecting a superconducting conductor layer 112 provided in a cable core 110 of a superconducting cable 100 and a conductor of a normal conducting device (not shown) used in a normal temperature environment. A unit 2 is provided. Examples of the normal electric conduction equipment include an apparatus for constructing a transmission line such as a normal conduction cable and a bus bar made of a normal conduction material such as aluminum and copper. As an installation form of the terminal structure 1, a horizontal type in which the axial direction of the superconducting cable 100 is a horizontal direction, a vertical type in which the axial direction of the superconducting cable 100 is a vertical direction, and the conductor lead-out portion 2 is disposed vertically upward. And the like. Here, in the terminal structure 1, the side where the conductor lead-out portion 2 is located is the normal temperature side (upper side), the side where the superconducting cable 100 is located is the cable side (lower side), and the cable drawn out from the end of the heat insulating pipe 120. The extending direction of the core 110 is defined as a longitudinal direction.

  As shown in FIG. 2, the terminal structure 1 according to the first embodiment includes a bushing 4 through which the cable core 110 is inserted, an insulator tube 7 that accommodates the room-temperature side area of the bushing 4, and a space between the bushing 4 and the cable core 110. And an inner vacuum heat insulating pipe 5 provided to extend to the room temperature side through the insulator pipe 7. At the room temperature side end of the inner vacuum heat insulating tube 5, there is a stepped portion 55 having a locally large outer diameter. One of the features of the terminal structure 1 is that the insulating portion 41 in the room temperature side region of the bushing 4 is arranged radially overlapped with the electric field control surface 7 </ b> A of the insulator tube 7, and the step portion of the inner vacuum heat insulating tube 5. The point 55 is located at a room temperature side of the electric field control surface 7A. Hereinafter, the basic configuration of the superconducting cable 100 will be described first with reference to FIG. 4, and then the detailed configuration of the terminal structure 1 will be described.

《Superconducting cable》
As shown in FIG. 4, the superconducting cable 100 includes a cable core 110 having a superconducting conductor layer 112 on the outer periphery of a former 111, and a heat insulating tube 120 for accommodating the cable core 110. The cable core 110 shown in FIG. 4 includes a former 111, a superconducting conductor layer 112, an electrical insulating layer 113, a shielding layer 114, and a protective layer 115 coaxially from the center. The superconducting cable 100 is a single-core cable in which one cable core 110 is housed in one heat insulating tube 120, and an electric insulating layer 113 is housed in the heat insulating tube 120 together with the superconducting conductor layer 112, and both are made of liquid nitrogen. This is a low-temperature insulated cable cooled by a refrigerant 130 (see FIG. 1). For example, three such single-core cables are laid, and a three-phase AC transmission line using each cable for power transmission in each phase, or two such single-core cables are laid, and one cable is forwarded. It is possible to construct a DC transmission line using the other cable for the return path. Each component of the cable core 110 can use a known configuration. A typical configuration of each component of the cable core 110 will be described below.

(Former)
The former 111 has a function of supporting the superconducting conductor layer 112. In this example, the former 111 is a hollow body (tubular body), and the internal space of the former 111 is used as a flow path (outward path in this example) of the refrigerant 130 (see FIG. 1) for cooling the superconducting conductor layer 112. As a constituent material of the former 111, a metal such as stainless steel, which can be used even at a refrigerant temperature and is excellent in strength even when it is thin, may be used. When a corrugated pipe or a bellows pipe is used for the former 111, flexibility is excellent even if it is made of a high-strength material. In this example, the former 111 is a bellows tube made of stainless steel. In addition, the former 111 may be a solid body such as a stranded wire obtained by twisting a plurality of strands (a copper wire, a coated copper wire having an insulating coating such as an enamel around the copper wire).

(Superconducting conductor layer)
The superconducting conductor layer 112 is formed by spirally winding a plurality of superconducting wires around the outer periphery of the former 111. As the superconducting wire, for example, a tape-shaped wire such as a Bi-based silver sheath wire or a RE123-based thin film wire can be used. The superconducting conductor layer 112 may be formed as a single layer, or may be formed as two or more layers. The number of superconducting wires and the number of layers may be appropriately selected according to the amount of current flowing through superconducting conductor layer 112. In this example, a case where the number of superconducting conductor layers 112 is four is shown. Between the layers of the superconducting conductor layer 112, an interlayer insulating layer (not shown) in which insulating paper or the like is wound may be provided. Further, an intervening layer (not shown) may be provided between the former 111 and the superconducting conductor layer 112 for the purpose of mechanically protecting the superconducting conductor layer 112 and the like.

(Electrical insulation layer)
The electrical insulating layer 113 ensures electrical insulation between the superconducting conductor layer 112 and the outside. The electric insulating layer 113 is formed by spirally winding an insulating paper around the superconducting conductor layer 112. As the insulating paper, for example, semi-synthetic paper such as kraft paper or PPLP (registered trademark; Polypropylene Laminated Paper) can be used.

(Shielding layer)
The shielding layer 114 is provided outside the superconducting conductor layer 112 (in this example, immediately above the electric insulating layer 113), and has a function of shielding an electric field caused by the superconducting conductor layer 112. The shielding layer 114 is formed by spirally winding a tape or a wire made of a normal conductive material such as copper around the outer periphery of the electric insulating layer 113.

(Protective layer)
The protective layer 115 is disposed on the outermost periphery of the cable core 110, mechanically protects a member (particularly, the superconducting conductor layer 112) disposed inside the cable core 110, and electrically protects the member between the shielding layer 114 and the heat insulating tube 120. Ensure insulation. The protective layer 115 is formed by spirally winding the above-described insulating paper around the outer periphery of the shielding layer 114.

  In addition, the cable core 110 may include an outer superconducting layer (not shown) on the outer periphery of the electric insulating layer 113 and a magnetic shielding layer made of a normal conducting material. The outer superconducting layer is formed by spirally winding the above-described superconducting wire. The outer superconducting layer, for example, can be used as a magnetic shielding layer in AC power transmission applications, and in a DC power transmission application, in the case of monopole power transmission, can be used as the return conductor when the superconducting conductor layer 112 is used as the outward conductor, and in the case of bipole power transmission. It can be used as a conductor for flowing a current having a polarity opposite to that of the superconducting conductor layer 112.

(Insulated pipe)
The heat insulating pipe 120 is a double-structured pipe having an inner pipe 121 and an outer pipe 122, and a space between the inner pipe 121 and the outer pipe 122 is evacuated, and a vacuum heat insulating layer in which a vacuum layer is formed is formed. Tube. The internal space of the inner tube 121 is a storage space for the cable core 110 and is used for a flow path (a return path in this example) of the refrigerant 130 (see FIG. 1). The inner pipe 121 and the outer pipe 122 may be formed of a corrugated pipe or a bellows pipe having excellent flexibility, or a straight pipe capable of reducing the pressure loss of the refrigerant. The constituent material of the inner tube 121 and the outer tube 122 includes a metal such as stainless steel. In this example, the inner pipe 121 and the outer pipe 122 are stainless steel corrugated pipes, and a heat insulating material 123 such as super insulation (trade name) is disposed between the inner pipe 121 and the outer pipe 122. . An anticorrosion layer 124 made of vinyl, polyethylene, or the like is formed on the outer periphery of the heat insulating tube 120 (outer tube 122). A vacuum port 100p (see FIG. 1) communicating with the space between the inner pipe 121 and the outer pipe 122 is attached to the opening of the heat insulating pipe 120.

《Terminal structure》
When connecting the above-described superconducting cable 100 and the normal conductive power device, for example, the terminal structure 1 shown in FIG. 1 is constructed. Specifically, at the end of the superconducting cable 100, the cable core 110 is pulled out from the end of the heat insulating tube 120 to expose the end of the cable core 110, and the superconducting conductor layer 112 and the conductor lead-out section 2 are electrically connected. I do. In the terminal structure 1, the exposed end of the cable core 110 is inserted into the bushing 4, the porcelain tube 7 is arranged outside the bushing 4, and the connection between the superconducting conductor layer 112 and the conductor lead-out portion 2 from the exposed portion of the cable core 110. A refrigerant layer (a region filled with the refrigerant 130) and a vacuum layer (the inner vacuum heat insulating pipe 5, the cable side heat insulating container 6) are provided over the locations. Hereinafter, each component of the terminal structure 1 will be described with reference to FIG. 1, and a main part of the terminal structure 1 will be described in detail with reference to FIG. 2.

(Cable core)
The shield layer 114 and the protective layer 115 (see FIG. 4) of the cable core 110 protruding from the end of the heat insulating tube 120 are cut off and removed near the heat insulating tube 120. At the end of the cable core 110 protruding from the end of the heat insulating tube 120, the electric insulating layer 113 is generally exposed in a region ahead of the opening of the heat insulating tube 120. Further, the tip of the cable core 110 (the portion projecting from the room temperature side end of the bushing 4) is stripped off, and the former 111 and the superconducting conductor layer 112 are exposed in order from the tip.

  The exposed superconducting conductor layer 112 and conductor lead-out portion 2 are joined by a suitable joining material such as solder or brazing material, and both are electrically connected. The conductor lead-out portion 2 of the present example has an insertion portion 212 into which a distal end portion of the cable core 110 is inserted at a cable-side end portion (a superconducting-side connecting portion 21 described later; see FIG. 2). The distal end of the cable core 110 is inserted into the insertion portion 212, and the superconducting conductor layer 112 is connected to the insertion portion 212 by the above-described bonding material. Furthermore, in this example, the former 111 and the insertion part 212 are compression-connected, and the connection strength between the cable core 110 and the conductor lead-out part 2 is increased.

  On the other hand, in the cable core 110 protruding from the end of the heat insulating tube 120, a region near the end of the heat insulating tube 120 where the shielding layer and the protective layer are removed and the electric insulating layer 113 is exposed is provided on the outer periphery thereof. A reinforcing insulating layer 8 is provided. The reinforcing insulating layer 8 is formed by spirally winding the above-described insulating paper around the outer periphery of the cable core 110 (the electric insulating layer 113). The reinforcing insulating layer 8 has a shape that tapers from an intermediate portion in the longitudinal direction toward both ends, that is, a shape that tapers toward the room temperature side and the cable side. Each inclined portion functions as a stress cone. The shield connection portion 80 is provided from the shield layer of the cable core 110 to the stress cone portion on the cable side in the reinforcing insulating layer 8. The shield connection part 80 is formed by winding a wire made of a normal conductive material such as copper.

(Bushing)
The bushing 4 penetrates a part of the cable core 110 protruding from the end of the heat insulating pipe 120, specifically, an intermediate part between the end of the cable core 110 and the part where the reinforcing insulating layer 8 is provided. Is done. Hereinafter, the bushing 4 will be described in detail with reference to FIG. The bushing 4 has a cylindrical insulating part 41 through which the cable core 110 is inserted, and a fixing part 42 formed on the outer periphery of the insulating part 41. Inside the bushing 4 (insulating portion 41), an inner tube 51 and an outer tube 52 constituting the inner vacuum heat insulating tube 5 are provided.

(Insulation part)
The insulating part 41 is a member that performs electrical insulation between the cable core 110 and the outside and also alleviates an electric field. The insulating portion 41 of this example is formed of an insulating material that can be used without any problem even at the temperature of the refrigerant, for example, a fiber reinforced resin (FRP) containing a resin component such as an epoxy resin and a reinforcing component such as a glass fiber. The normal-temperature-side region of the insulating portion 41 housed in the insulator tube 7 has a shape whose outer diameter tapers toward a normal-temperature-side end, and the inclined portion functions as a stress cone. The electric field can be adjusted by arranging a plurality of metal foils (not shown) concentrically at intervals in the radial direction in the insulating portion 41. The cable-side region of the insulating portion 41 has a uniform cylindrical surface on its outer peripheral surface, but its inner peripheral surface is inclined radially outward toward the cable-side end. An appropriate space is secured between the reinforcing insulating layer 8 and the stress cone portion on the normal temperature side.

(Fixed part)
The fixing portion 42 is a member provided at an intermediate portion (excluding the stress cone portion) of the insulating portion 41 in the longitudinal direction, and is a member for fixing the bushing 4 to the insulator tube 7. In this example, the fixing part 42 is joined to the outer periphery of the part on the cable side from the stress cone part in the normal temperature side region of the insulating part 41. The fixing portion 42 has a flange portion extending radially outward. The bushing 4 is fixed to the insulator tube 7 by attaching the flange portion to the insulator tube 7 (lower metal fitting 71) with a bolt or the like. The fixing portion 42 is formed of an appropriate metal, resin, or the like.

(Inner vacuum insulation tube)
As shown in FIG. 2, the inner vacuum heat insulating tube 5 is inserted into the insulator tube 7, and is disposed inside the bushing 4 (insulating portion 41) so as to house the distal end of the cable core 110. The inner vacuum heat insulating tube 5 of this example is provided so as to extend from the inner periphery of the bushing 4 and the outer periphery of the cable core 110 to the room temperature side through the insulator tube 7, and a refrigerant 130 for cooling the superconducting conductor layer 112. Keep insulated. In this example, the inner vacuum heat insulating pipe 5 includes an inner pipe 51 and an outer pipe 52, and a space between the inner pipe 51 and the outer pipe 52 is evacuated, and a vacuum layer is formed in this space. . A heat insulating material (not shown) such as super insulation (trade name) is arranged between the inner pipe 51 and the outer pipe 52. The constituent material of the inner tube 51 and the outer tube 52 includes a metal such as stainless steel.

  The inner tube 51 houses the distal end portion of the cable core 110 inside, and is filled with a refrigerant 130 for cooling the superconducting conductor layer 112 and is used for a refrigerant flow path. The outer tube 52 is provided integrally with the insulating portion 41 of the bushing 4 on its outer peripheral surface. The inner pipe 51 and the outer pipe 52 of this example are connected and sealed at both ends on the room temperature side and the cable side. A vacuum port 50p communicating with a space between the inner pipe 51 and the outer pipe 52 is provided at one end on the normal temperature side. In this example, the vacuum port 50p is drawn out of a non-vacuum heat insulating layer 3 (heat insulating material 31) described later.

  In this example, one end of the inner vacuum heat insulating pipe 5 on the normal temperature side protrudes from the insulator pipe 7 (upper fitting 72). The cable side of the inner vacuum heat insulating pipe 5 protrudes from the insulator pipe 7 (the lower metal fitting 71), and is provided so as to partially overlap the room temperature side of the cable side heat insulating container 6 described later. The inner space of the inner tube 51 of the inner vacuum heat insulating tube 5 and the inner space of the refrigerant tank 61 of the cable side heat insulating container 6 communicate with each other, and the refrigerant 130 is allowed to flow between the inner tube 51 and the refrigerant tank 61. Is possible.

(Step)
At the room temperature side end of the inner vacuum heat insulating tube 5 of this example, there is a stepped portion 55 whose outer diameter is locally increased. Specifically, a flange portion 52f is provided at the room temperature end of the outer tube 52, and a step portion 55 is formed by the flange portion 52f. A portion on the room temperature side of the step portion 55 has a large diameter. Here, the large-diameter portion on the normal temperature side of the step portion 55 is also included in the step portion 55. In this example, the bellows tube 52b is inserted into the large diameter portion of the step portion 55, and the bellows tube 51b is also inserted into the room temperature side end of the inner tube 51. Since the bellows pipes 51b and 52b are provided in the inner vacuum heat insulating pipe 5 (the inner pipe 51 and the outer pipe 52), the bellows pipes 51b and 52b can absorb heat shrinkage during cooling. A flange portion 55f extending radially outward is attached to the outer peripheral surface of the step portion 55. By attaching the flange portion 55f to the insulator tube 7 (upper fitting 72) with bolts or the like, the room temperature side end of the inner vacuum heat insulating tube 5 is fixed to the insulator tube 7.

  The main part of the inner pipe 51 and the outer pipe 52 except for the normal temperature side end (in this example, the part closer to the cable than the bellows pipes 51b and 52b) is formed of a straight pipe. If the main portion of the inner pipe 51 is a straight pipe, the pressure loss of the refrigerant can be reduced. On the other hand, if the main portion of the outer tube 52 is a straight tube, it is easy to form the insulating portion 41 in close contact with the outer peripheral surface of the outer tube 52.

(Cable side insulation container)
As shown in FIG. 1, the cable-side heat-insulating container 6 is provided from the opening of the heat-insulating pipe 120 to the lower metal fitting 71 of the heat-insulating pipe 7, and a part of the cable core 110 protruding from the end of the heat-insulating pipe 120. The cable side area of the bushing 4 is stored. The normal temperature side of the cable side heat insulating container 6 of this example is connected to the lower metal fitting 71 of the insulator tube 7, and the cable side of the cable side heat insulating container 6 is connected to the end of the heat insulating tube 120. In this example, the cable-side heat-insulating container 6 includes a refrigerant tank 61 and a vacuum tank 62 covering the outside thereof, and the space between the two tanks 61 and 62 is evacuated to form a vacuum layer. The refrigerant 130 for cooling the layer 112 is kept insulated. A heat insulating material (not shown) such as super insulation (trade name) is disposed between the two tanks 61 and 62. The constituent materials of the refrigerant tank 61 and the vacuum tank 62 include metals such as stainless steel.

  The refrigerant tank 61 accommodates a part of the cable core 110 and the cable-side region of the bushing 4 inside, and is filled with a refrigerant 130 for cooling the superconducting conductor layer 112 and is used for a refrigerant flow path. The vacuum chamber 62 is provided with a vacuum port 60p communicating with a space between the refrigerant chamber 61 and the vacuum chamber 62.

  In this example, the internal space of the refrigerant tank 61 of the cable-side heat insulating container 6 and the internal space of the inner pipe 121 of the heat insulating pipe 120 communicate with each other, and the refrigerant 130 flows between the refrigerant tank 61 and the inner pipe 121. It is possible to do. The cable side heat insulating container 6 is provided with a refrigerant introduction pipe 63 for introducing the refrigerant 130 into the refrigerant tank 61 and a refrigerant discharge pipe 64 for discharging the refrigerant from the refrigerant tank 61. The refrigerant 130 introduced into the refrigerant tank 61 via the refrigerant introduction pipe 63 flows from the refrigerant tank 61 through the inner pipe 51 of the inner vacuum heat insulating pipe 5 toward the distal end side of the cable core 110, and a conductor described later. It flows into the former 111 through the through-hole 21c formed in the extraction part 2 (superconducting side connection part 21, see FIG. 2). The refrigerant 130 that has flowed into the former 111 flows from one end of the superconducting cable 100 toward the other end thereof, and from the inside of the former 111 to the inner tube 121 of the heat insulating tube 120 at the other end (not shown) of the superconducting cable 100. (A space between the pipe 121 and the cable core 110). The refrigerant 130 introduced into the inner pipe 121 of the heat insulating pipe 120 flows from the other end of the superconducting cable 100 toward one end, flows out of the inner pipe 121 into the refrigerant tank 61, and flows out of the refrigerant tank 61. The refrigerant is discharged through the refrigerant discharge pipe 64. In the inside of the refrigerant tank 61 of this example, a space connected to the refrigerant introduction pipe 63 and a space connected to the refrigerant discharge pipe 64 are partitioned by a partition portion 65, and the refrigerant 130 introduced from the refrigerant introduction pipe 63 immediately discharges the refrigerant. It is prevented from being discharged from the pipe 64.

(Insulator tube)
As shown in FIG. 2, the insulator tube 7 is a member that accommodates the normal temperature side region of the bushing 4 (insulating portion 41) and is used for electric field control. The insulator tube 7 of this embodiment is provided at a cylindrical main body portion 70 on which a plurality of insulators 7i are formed, a lower metal fitting 71 provided at an end portion of the main body portion 70 on a cable side, and an ordinary temperature end portion of the main body portion 70. And an upper fitting 72.

(Main unit)
The main body 70 has an electric field control surface 7A formed by a plurality of insulators 7i. In this example, the insulator 7i is a porcelain insulator. The number of the insulators 7i may be appropriately selected so as to secure an insulation distance (creeping distance) between the upper metal fitting 72 and the lower metal fitting 71. The main body 70 and the lower metal fitting 71 and the upper metal fitting 72 are joined via a lower cylindrical part 71b and an upper cylindrical part 72u, which will be described later. Specifically, in the case of the present example, the lower cylindrical portion 71b and the upper cylindrical portion 72u are cemented to the outer peripheral surfaces of the respective ends of the main body 70 on the cable side and the normal temperature side, respectively. The lower metal fitting 71 and the upper metal fitting 72 are respectively fastened to the cylindrical portion 72u by bolts.

(Lower fitting)
The lower metal fitting 71 is an annular member through which the bushing 4 is inserted, and to which the fixing portion 42 of the bushing 4 is attached. Thereby, the bushing 4 is fixed in a state where the bushing 4 is inserted into the lower metal fitting 71. The lower metal fitting 71 has a lower cylindrical portion 71b that protrudes so as to cover the end of the main body 70 on the cable side. The lower cylindrical portion 71b is joined to the lower metal fitting 71 by a bolt or the like and is integrated.

(Upper bracket)
The upper metal fitting 72 is an annular member through which the normal temperature end of the inner vacuum heat insulating pipe 5 is inserted, and the normal temperature end of the inner vacuum heat insulating pipe 5 is inserted and fixed by attaching the above-mentioned flange portion 55f. You. The upper metal part 72 has an upper cylindrical part 72u that protrudes so as to cover the normal temperature side end of the main body part 70. The upper cylindrical portion 72u is joined to the upper metal fitting 72 by a bolt or the like, and is integrated.

  The constituent materials of the lower metal fitting 71 (including the lower cylindrical part 71b) and the upper metal fitting 72 (including the upper cylindrical part 72u) include metals such as stainless steel. The lower metal fitting 71 is grounded and is at the ground potential including the lower cylindrical portion 71b. Therefore, the outer peripheral side of the insulating portion 41 to which the fixing portion 42 attached to the lower metal fitting 71 is joined has a low potential. On the other hand, the inner vacuum insulated pipe 5 is charged to a high potential by a high voltage applied to the cable core 110 (superconducting conductor layer 112), and the upper metal fitting 72 to which the normal temperature end of the inner vacuum insulated pipe 5 is fixed is located on the upper side. The potential becomes high including the cylindrical portion 72u. Further, the inner peripheral side of the insulating portion 41 also has a high potential. Therefore, in the normal temperature side region (the inclined portion as the above-mentioned stress cone) of the insulating portion 41, the potential sequentially changes from the high potential to the low potential along the inclined surface from the tip side.

(Electric field control surface)
The above-described electric field control surface 7A includes a portion of the main body 70 that includes an insulator series in which a plurality of insulators 7i are connected, and is not covered by the upper cylindrical portion 72u and the lower cylindrical portion 72d that cover both ends of the main body 70. (A section between the lower end of the upper tubular portion 72u and the upper end of the lower tubular portion 71d). That is, on the outer peripheral surface of the main body 70, the electric field control surface 7A exists between the lower end on the high potential side and the upper end on the ground potential side, which are sandwiched between the upper tubular portion 72u and the lower tubular portion 72d.

  In the present embodiment, the room-temperature side region of the bushing 4 (the insulating portion 41) is radially overlapped with the electric field control surface 7A. Further, the step portion 55 of the inner vacuum heat insulating pipe 5 is located on the room temperature side with respect to the electric field control surface 7A. FIG. 3 shows the distribution of equipotential lines in the normal temperature side region of the bushing 4. The distribution of the equipotential lines was determined using known FEM (Finite Element Method) electric field analysis software. As shown in FIG. 3, since the step portion 55 is located on the room temperature side with respect to the electric field control surface 7 </ b> A, it is possible to suppress the equipotential lines generated in the room temperature region of the insulating portion 41 from intersecting with the step portion 55. . The equipotential lines generated in the insulating portion 41 pass mainly through the electric field control surface 7A of the insulator tube 7, and the distribution of the equipotential lines is uniform over the entire length of the electric field control surface 7A.

(Conductor drawer)
As shown in FIGS. 1 and 2, the conductor lead-out portion 2 is a member to which the exposed superconducting conductor layer 112 is electrically connected at the end of the above-described cable core 110, and is usually made of copper or aluminum. It is made of a conductive material. In this example, the connection between the superconducting conductor layer 112 and the conductor lead-out portion 2 is arranged in the insulator tube 7 and housed in the inner vacuum heat insulating tube 5.

  As shown in FIG. 2, the conductor lead-out portion 2 of the present embodiment includes a tubular portion 20, a superconducting-side connecting portion 21, and a normal-conducting-side connecting portion 22, and these members are joined and connected. . The superconducting-side connecting portion 21 is joined to an end of the tubular portion 20 on the cable side, and the normal-conducting-side connecting portion 22 is joined to an end of the tubular portion 20 on the normal temperature side. For joining the cylindrical portion 20 to the superconducting-side connecting portion 21 and the normal-conducting-side connecting portion 22, solder, bolts, or the like can be used.

(Cylindrical part)
The tubular portion 20 is provided between the superconducting-side connecting portion 21 and the normal-conducting-side connecting portion 22 and has a hollow interior. The provision of the tubular portion 20 can suppress heat intrusion from the normal-conducting-side connecting portion 22 to the superconducting-side connecting portion 21, and reduce heat intrusion from the conductor lead-out portion 2 to the superconducting conductor layer 112. The reason for this is that in AC power transmission, the current concentrates on the surface of the conductor due to the skin effect, so the effective cross-sectional area of the conductor through which the current flows can be secured, while the actual cross-sectional area is smaller than in the case of a rod shape. This is because heat becomes difficult to transmit. The cross-sectional shape of the tubular portion 20 is not particularly limited. The cylindrical portion 20 of the present example is a cylindrical member having a circular cross section whose outer diameter and inner diameter are uniform in the axial direction. The outer diameter and the inner diameter of the cylindrical portion 20 may be appropriately set so as to ensure a sufficient conductor cross-sectional area according to the amount of current flowing through the superconducting conductor layer 112.

  A through hole 20 h communicating with the internal space of the cylindrical portion 20 is formed on the peripheral surface of the cylindrical portion 20. It is possible to fill the cylindrical portion 20 with a resin constituting a non-vacuum heat insulating layer 3 (heat insulating material 31) described later through the through hole 20h. It is preferable to provide a plurality of through-holes 20h in consideration of the filling property of the resin. The through-hole 20h is a breathing hole that allows air in the cylindrical portion 20 expanded by the heat of the solder to escape to the outside when the superconducting conductor layer 112 is connected to the conductor lead-out portion 2 (superconducting-side connecting portion 21) by soldering. Also works as

(Superconducting side connection)
The superconducting-side connecting portion 21 is a portion to which the superconducting conductor layer 112 is connected, and has a bottomed tubular joining portion 211 joined to the tubular portion 20, and a distal end portion of the cable core 110 (the exposed former 111 and the exposed former 111). (A superconducting conductor layer 112). The inner diameter of the joint portion 211 is slightly larger (about 0.5 mm to 2 mm) than the outer diameter of the tubular portion 20, and the joint portion 211 is fitted to the end of the tubular portion 20 on the cable side, so that the tubular portion is formed. 20 can be sealed on the cable side.

  The insertion portion 212 of this example is inserted into the inner tube 51 from one end on the room temperature side of the inner vacuum heat insulating tube 5 and is housed in the inner vacuum heat insulating tube 5. A through hole 21 c communicating with the internal space of the insertion section 212 is formed on the peripheral surface on the bottom side of the insertion section 212. The internal space of the former 111 inserted into the insertion portion 212 communicates with the internal space of the inner tube 51 of the inner vacuum heat insulating tube 5 through the through hole 21c, and the refrigerant 130 can flow through the former 111. It is. That is, the through hole 21c functions as a part of the coolant flow path.

  In this example, an injection hole penetrating in and out is formed on a peripheral surface of the insertion portion 212 at a position corresponding to the inserted superconducting conductor layer 112. By inserting a bonding material such as solder or brazing material from the injection hole, it is possible to connect the insertion portion 212 and the superconducting conductor layer 112.

(Normal conduction connection)
The normal-conducting-side connecting portion 22 is a portion that protrudes from the upper end of the terminal structure 1 and is connected to the normal-conducting power device, and has a bottomed tubular joining portion 221 joined to the tubular portion 20, a terminal portion 222, Having. The inner diameter of the joining portion 221 is slightly larger (about 0.5 mm to 2 mm) than the outer diameter of the tubular portion 20, and by fitting the joining portion 221 to the end of the tubular portion 20 on the normal temperature side, the tubular portion is formed. 20 normal temperature openings can be sealed.

  The terminal portion 222 of the present example is formed in a flat plate shape, and is connected to a conductor of a normal electric power device.

(Non-vacuum insulation layer)
As shown in FIGS. 1 and 2, the terminal structure 1 of the present example includes a non-vacuum heat-insulating layer 3 that covers the outer periphery of the conductor lead-out portion 2. The non-vacuum heat insulating layer 3 is formed of a heat insulating material 31. By providing the non-vacuum heat-insulating layer 3 formed of the heat insulating material 31 on the outer periphery of the conductor lead-out portion 2, heat penetration from the outside can be suppressed, and heat penetration from the conductor lead-out portion 2 to the superconducting conductor layer 112 can be reduced. Further, since the non-vacuum heat insulating layer 3 is a heat insulating structure formed of the heat insulating material 31, the structure is simpler than that of a heat insulating structure using a vacuum layer (vacuum heat insulating layer). As a constituent material of the heat insulating material 31, a resin is preferable, and examples thereof include a resin such as a polyurethane resin, a polystyrene resin, a polyester resin, a polyolefin resin, a polyethylene resin, a polypropylene resin, and a phenol resin, and a polyurethane resin is particularly preferable.

  In this example, a non-vacuum heat insulating layer 3 is formed by attaching a case 30 surrounding the outer periphery of the conductor lead-out portion 2 and filling the case 30 with a resin as a heat insulating material 31. In the case of this example, the case 30 is attached to the upper side of the insulator tube 7 (the upper metal fitting 72), and a portion of the conductor lead-out portion 2 (normal-conduction-side connection portion 22) except for the terminal portion 222 is covered with the heat insulating material 31. The case 30 is formed with a filling hole 30h penetrating inside and outside, and the resin constituting the heat insulating material 31 can be filled into the case 30 from the filling hole 30h. The resin filled in the case 30 has fluidity at the time of filling, and solidifies after filling. Since the resin has fluidity at the time of filling, the resin can be filled to every corner in the case 30, and the outer peripheral surface of the cylindrical portion 20 of the conductor lead-out portion 2 can be covered with the heat insulating material 31 without any gap. Since the heat insulating material 31 comes into close contact with the outer peripheral surface of the cylindrical portion 20, the outer periphery of the cylindrical portion 20 is cooled by the heat conduction from the superconducting-side connecting portion 21 cooled by the refrigerant 130. Dew condensation and frost formation on the surface can be prevented. Further, in this example, since the resin also enters the inside of the tubular portion 20 through the through hole 20h of the tubular portion 20, the heat insulating material 31 is filled in the tubular portion 20.

  The tubular portion 20 may be left hollow without providing the through-hole 20h in the tubular portion 20. However, as in this example, the tubular portion 20 is filled with the heat insulating material 31. In this case, it is possible to suppress the air from remaining in the tubular portion 20. Therefore, liquefaction of air in the cylindrical portion 20 due to cooling of the cylindrical portion 20 by heat conduction from the superconducting side connection portion 21 cooled by the refrigerant 130 can be suppressed. When the inside of the cylindrical portion 20 is made hollow, a gas (for example, helium gas) that does not liquefy even at the temperature of the refrigerant 130 that cools the superconducting conductor layer 112 to the superconducting state may be sealed in the cylindrical portion 20.

  Further, the refrigerant may be circulated in the tubular portion 20 without filling the heat insulating material 31 in the tubular portion 20. For example, as a refrigerant distribution mechanism, a refrigerant introduction pipe and a refrigerant discharge pipe that penetrate through the non-vacuum heat insulating layer 3 and communicate with the internal space of the cylindrical part 20 are attached, and the refrigerant is introduced into the cylindrical part 20 from the refrigerant introduction pipe. To discharge the refrigerant from the refrigerant discharge pipe. Thereby, since the cylindrical portion 20 can be directly cooled by the refrigerant, the heat intrusion from the normal conducting side connecting portion 22 to the superconducting side connecting portion 21 can be largely suppressed, and the temperature of the conductor lead-out portion 2 can be stabilized. . As the refrigerant, any of a liquid refrigerant (for example, liquid nitrogen), a gas refrigerant (for example, low-temperature nitrogen gas), and a gas-liquid mixed refrigerant containing a liquid refrigerant and a gas refrigerant can be used. Above all, a refrigerant containing a liquid refrigerant has a higher heat capacity than a gas refrigerant, and therefore has a higher cooling efficiency. The temperature of the refrigerant to be circulated may be higher than the temperature of the refrigerant 130 that cools the superconducting conductor layer 112 to a superconducting state.

  In the present embodiment, the configuration in which the outer periphery of the conductor lead-out portion 2 is covered with the non-vacuum heat insulating layer 3 is exemplified, but instead of the non-vacuum heat-insulating layer 3, the outer periphery of the conductor lead portion 2 is formed by a vacuum heat insulating container formed by a vacuum heat insulating container. It is also possible to adopt a configuration of covering with a layer.

  Further, in the terminal structure 1 of the present example, an upper shield fitting 9 surrounding the outer periphery of the non-vacuum heat insulating layer 3 may be arranged.

<< Terminal structure manufacturing method >>
The terminal structure 1 of the above-described first embodiment can be constructed by, for example, a manufacturing method including the following steps.
・ Terminal treatment process of cable core ・ Connecting process of conductor lead-out part ・ Bushing installation process ・ Cable side heat insulating container forming process ・ Insulator tube forming process ・ Vacuum drawing process ・ Non-vacuum heat insulating layer forming process

(Cable core termination process)
At one end of the laid superconducting cable 100, the cable core 110 is pulled out from the end of the heat insulating tube 120, the end of the cable core 110 is stripped, and the former 111, the superconducting conductor layer 112, the electric insulating layer 113, and the like are exposed in order. Let it. In this example, after the reinforcing insulating layer 8 is formed in the vicinity of the heat insulating tube 120 in the cable core 110, the shield connection portion 80 is provided (FIG. 1).

(Connecting process of conductor lead-out part)
The leading conductor 2 is connected to the tip of the cable core 110. In this example, the tip of the cable core 110 is inserted into the insertion portion 212 of the superconducting-side connection portion 21, the former 111 is compression-connected to the insertion portion 212, and the superconducting conductor layer 112 is connected with a bonding material such as solder.

(Bushing installation process)
In this example, the insulating portion 41 of the bushing 4 is integrally provided on the outer peripheral surface of the outer tube 52 of the inner vacuum heat insulating tube 5 in advance, and a part in which the bushing 4 and the inner vacuum heat insulating tube 5 are integrated is manufactured at a factory or the like. Keep it. A step 55 is provided at the room temperature side end of the inner vacuum heat insulating pipe 5, and bellows pipes 51 b and 52 b are inserted into the inner pipe 51 and the outer pipe 52, respectively. Then, in a state where the lower metal fitting 71 of the porcelain tube 7 is fixed to the fixing portion 42 of the bushing 4 by bolts or the like, the distal end portion of the cable core 110 is inserted into the inner vacuum heat insulating tube 5 integrated with the bushing 4, The bushing 4 (insulating portion 41) is arranged at a predetermined position of the cable core 110. Further, the distal end portion of the cable core 110 and the connection point between the superconducting conductor layer 112 and the conductor lead-out portion 2 (insertion portion 212) are housed in the inner vacuum heat insulating tube 5.

(Formation process of the cable side heat insulation container)
The refrigerant tank 61 and the vacuum tank 62 are formed so as to cover a part of the cable core 110 protruding from the end of the heat insulating pipe 120 and the cable side area of the bushing 4, and the cable side heat insulating container 6 is assembled. In this example, the inner tube 121 of the heat insulating tube 120 and the refrigerant tank 61 are joined by welding or the like, and the outer tube 122 and the vacuum tank 62 are joined by welding or the like. Then, the normal temperature side of the refrigerant tank 61 and the vacuum tank 62 is joined to the lower metal fitting 71 by welding or the like so as to close the open end of the cable side heat insulating container 6 on the normal temperature side.

(Process of forming insulator tube)
The porcelain tube 7 is assembled so as to cover the room temperature side region of the bushing 4. In this example, the main body 70 is fitted to the outside of the inner vacuum heat insulating tube 5 so that the room-temperature region of the bushing 4 is housed, and the cable side of the main body 70 is attached to the lower metal fitting 71. After that, the upper metal fitting 72 is attached to the normal temperature side of the main body 70, and the normal temperature side end (the flange 55f of the step portion 55) of the inner vacuum heat insulating tube 5 is joined to the upper metal fitting 72 with a bolt or the like and inserted and fixed. In this example, the lower cylinder 71b and the upper cylinder 72u are cemented to both ends of the main body 70 in advance, and the lower metal 71 and the upper metal 72 are respectively fastened to the lower cylinder 71b and the upper cylinder 72u by bolts. By doing so, the main body 70 is joined to the lower metal fitting 71 and the upper metal fitting 72. At this time, the normal temperature side region of the bushing 4 (insulating portion 41) is radially overlapped with the electric field control surface 7A of the main body portion 70, and the step portion 55 of the inner vacuum heat insulating tube 5 is positioned at the electric field control surface. It is located on the room temperature side of 7A. The introduction of the insulating fluid into the insulator tube 7 can be performed at an appropriate time.

(Evacuation process)
The inner vacuum heat insulating tube 5, the cable side heat insulating container 6, and the heat insulating tube 120 are evacuated using the vacuum ports 50p, 60p, and 100p. Each evacuation can be performed at an appropriate time. In this example, since the vacuum port 50p of the inner vacuum heat insulating tube 5 protrudes from the non-vacuum heat insulating layer 3 (heat insulating material 31) formed in a later step and is drawn out, the formation of the non-vacuum heat insulating layer 3 is performed. It is possible to evacuate not only before but also after the construction of the terminal structure 1. The vacuum ports 60p and 100p can be evacuated even after the terminal structure 1 is constructed.

(Process of forming non-vacuum heat insulating layer)
In this example, a box-shaped case 30 is attached to the upper side of the insulator tube 7 (upper bracket 72), the outer periphery of the conductor lead-out portion 2 is surrounded by the case 30, and then the resin forming the heat insulating material 31 from the filling hole 30h of the case 30. Fill. At this time, the resin filled in the case 30 also fills the inside of the tubular portion 20 through the through hole 20h formed in the tubular portion 20 of the conductor lead-out portion 2. When the filling of the resin is completed, the resin is solidified to form the non-vacuum heat insulating layer 3 formed of the heat insulating material 31.

  Through the above steps, the terminal structure 1 can be constructed. After the construction, the superconducting conductor layer 112 is cooled to a superconducting state by introducing and circulating the refrigerant 130, so that the superconducting cable 100 can be used for a transmission line.

<effect>
The terminal structure 1 of the superconducting cable according to the first embodiment has the following effects.
Since the step 55 provided at the room temperature side end of the inner vacuum heat insulating tube 5 is located on the room temperature side of the electric field control surface 7A of the insulator tube 7, it is generated in the room temperature region of the bushing 4 (insulating portion 41). It is possible to prevent the equipotential lines from intersecting with the steps 55. Therefore, the equipotential lines generated in the insulating portion 41 pass mainly through the electric field control surface 7A of the insulator tube 7 and the distribution of the equipotential lines is made uniform, so that the electric field of the insulating portion 41 can be effectively reduced. . Further, since the surface of the insulator can be effectively used, the length of the insulator tube 7 (the main body 70) can be reduced. Therefore, in the terminal structure 1, the length of the insulator tube 7 can be reduced while effectively reducing the electric field of the insulating portion 41 in the bushing 4, so that the overall length of the terminal can be reduced.

<Applications>
The superconducting cable terminal structure 1 according to the first embodiment can be suitably used for a transmission line (an AC transmission line, a DC transmission line) using the superconducting cable 100.

The present invention is not limited to these examples, but is indicated by the appended claims, and is intended to include all modifications within the scope and meaning equivalent to the appended claims.
For example, the superconducting cable 100 is a single-core cable in which one cable core 110 is housed in one heat insulating tube 120, and a multi-core package in which two or more cable cores 110 are housed in one heat insulating tube 120. It may be a cable. The superconducting cable 100 has a low-temperature insulation type structure in which the electric insulating layer 113 is disposed in the heat insulating tube 120 and is cooled by the refrigerant. An insulating structure may be used.

DESCRIPTION OF SYMBOLS 1 Terminal structure of superconducting cable 2 Conductor lead-out part 20 Cylindrical part 20h Through hole 21 Superconducting side connecting part 211 Joining part 212 Inserting part 21c Through hole 22 Normal conducting side connecting part 221 Joining part 222 Terminal part 3 Non-vacuum heat insulating layer 30 Case 30h Filling hole 31 Heat insulating material 4 Bushing 41 Insulating part 42 Fixed part 5 Inner vacuum heat insulating pipe 51 Inner pipe 52 Outer pipe 52f Flange part 55 Stepped part 55f Flange part 51b, 52b Bellows pipe 50p Vacuum port 6 Cable side heat insulating container 61 Refrigerant tank 62 Vacuum tank 63 Refrigerant introduction pipe 64 Refrigerant discharge pipe 65 Partition part 60p Vacuum port 7 Insulator pipe 70 Main body part 7i Insulator 7A Electric field control surface 71 Lower fitting 71b Lower cylinder 72 Upper fitting 72u Upper cylinder 8 Reinforcement insulating layer 80 Shield connection 9 Upper shield fitting 100 Superconducting cable 110 Cave Lucor 111 Former 112 Superconducting conductor layer 113 Electrical insulating layer 114 Shielding layer 115 Protective layer 120 Insulated tube 121 Inner tube 122 Outer tube 123 Insulating material 124 Anticorrosion layer 100p Vacuum port 130 Refrigerant

Claims (3)

A cable core protruding from the end of the heat insulating tube at the end of the superconducting cable,
A bushing through which a part of the cable core is inserted;
A porcelain tube for accommodating a room temperature side region in the bushing;
At the end of the cable core protruding from the room temperature side end of the bushing, a conductor extraction portion to which a superconducting conductor layer provided in the cable core is connected,
An inner vacuum heat insulating pipe that is provided so as to extend from the inner circumference of the bushing and the outer circumference of the cable core to the room temperature side through the inside of the insulator tube, and insulates and retains a refrigerant that cools the superconducting conductor layer of the cable core. ,
The bushing has an insulating portion having a normal-temperature side region tapered toward an end, and a fixing portion provided at an intermediate portion of the insulating portion and formed on an outer periphery of the insulating portion,
The insulator tube includes a cylindrical main body having an electric field control surface on which a plurality of insulators are formed, a lower fitting provided at a cable side end of the main body, to which the fixing portion of the bushing is attached, An upper fitting provided at a normal temperature side end of the section and through which the normal temperature side end of the inner vacuum heat insulating tube is inserted and fixed,
At the room temperature side end of the inner vacuum heat insulating tube, there is a step portion where the outer diameter is locally increased,
The insulating portion in the room temperature side region of the bushing is radially overlapped with the electric field control surface of the main body in the insulator tube, and the step portion of the inner vacuum heat insulating tube is connected to the electric field control surface. Terminal structure of superconducting cable located on the normal temperature side.   The terminal structure for a superconducting cable according to claim 1, wherein a bellows pipe is provided at the step portion of the inner vacuum heat insulating pipe. A non-vacuum heat insulating layer covering the outer periphery of the conductor lead-out portion,
The terminal structure for a superconducting cable according to claim 1 or 2, wherein the non-vacuum heat insulating layer is formed of a heat insulating material.