JP2015211580A - Terminal structure of superconducting cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terminal structure of a superconducting cable capable of uniformly passing current through each layer of a multilayered superconducting layer.SOLUTION: A terminal structure of a superconducting cable has a plurality of superconducting layers laminated one upon another with an insulating layer interposed therebetween around a circumference of a core material. The terminal structure includes: a plurality of connection members connected to each of the superconducting layers in a one-to-one manner; and an external connection terminal. Each of the connection members has a terminal part connected to the superconducting layer, and a current lead part that extends from the terminal part and is connected to the external connection terminal. A resistance value of the current lead part is larger than a connection resistance value between the terminal part and the superconducting layer.

Description

  Embodiments described herein relate generally to a terminal structure of a superconducting cable.

  Superconducting cables are attracting attention as a technology that can solve the shortage of transmission line capacity in areas where power demand increases and can reduce loss during power transmission. As a superconducting cable, a superconducting cable is known in which an oxide superconducting conductor processed into a wire is spirally wound around a former. In such a superconducting cable, a wire made of an oxide superconductor (oxide superconducting wire) is wound in multiple layers via an insulating layer.

  Such a terminal structure of a superconducting cable is electrically connected by soldering to a connection terminal extending from an external power source (for example, Patent Document 1 and Patent Document 2). In such a terminal structure, the connection terminal is configured to reduce power loss due to the resistance component by reducing its resistance value as much as possible.

JP 2013-59211 A Japanese Patent Laid-Open No. 10-126917

FIG. 8 shows a terminal structure 110 of the superconducting cable 101 as an example of a conventional terminal structure, and FIG. 9 shows a partial sectional view of the terminal structure 110.
In the superconducting cable 101 shown in FIG. 8, two superconducting layers 106 and 107 are laminated around a former (core material) 181 via an insulating layer 182. In the terminal of the superconducting cable 101, the former 181 and the superconducting layers 106 and 107 are exposed stepwise. The terminal portion 104A of the connection member 104 is attached so as to cover each exposed layer. A solder 105 is filled between the connection member 104 and each exposed layer. The connection member 104 includes a current lead portion 104B connected to an external power source. By applying a voltage from an external power source, a current can be passed through the superconducting layers 106 and 107 of the superconducting cable.
The lead portion 104B of the connecting member 104 is configured to be as short as possible in order to make the resistance value as low as possible, thereby reducing the loss due to the resistance component.

  In the terminal structure 110 of the superconducting cable, the superconducting layers 106 and 107 and the connecting member 104 are collectively connected via the solder 105. Further, different connection resistances are generated between the solder 105 and the superconducting layers 106 and 107. This connection resistance is very small, about 1 nΩ to 100 nΩ, and it is difficult to accurately control this connection resistance value. Such a slight connection resistance does not cause a problem in the connection of a normal conducting conductor such as copper. However, since the superconducting conductor does not show a resistance value at an extremely low temperature, there is a problem in that the value of the current flowing through each layer greatly changes due to a slight difference in connection resistance.

FIG. 10 is a simulation result of current flowing in each layer when a direct current is passed through the superconducting cable 101. In this simulation, the connection resistance between the superconducting layer 106 inside the superconducting cable 101 and the connection member 104 is 50 nΩ, and the connection resistance between the outer superconducting layer 107 and the connection member 104 is zero.
The horizontal axis indicates the current value flowing through the entire superconducting cable (that is, the current value flowing through the inner superconducting layer and the outer superconducting layer).
As shown in FIG. 10, since the inner superconducting layer 106 has a slight connection resistance (50 nΩ) between the inner superconducting layer 106, almost no current flows until the total current becomes about 5000A. On the other hand, current concentrates on the outer superconducting layer 107.

  As can be seen from the simulation results shown in FIG. 10, in the conventional terminal structure, the value of the current flowing through each layer is greatly different due to the connection resistance between each superconducting layer of the superconducting cable and the connecting member. As a result, a current flows concentratedly in a part of the superconducting layer, and this current reaches a critical current value, which may cause heat generation of the wire.

  The present invention has been made in view of the above-described conventional situation, and an object of the present invention is to provide a terminal structure of a superconducting cable capable of flowing a current uniformly to each layer of superconducting layers formed in multiple layers.

The terminal structure of a superconducting cable according to the present invention is a terminal structure of a superconducting cable in which a plurality of superconducting layers are stacked around an insulating layer via an insulating layer, and is connected to each superconducting layer on a one-to-one basis. Each of the connection members includes a terminal portion connected to the superconducting layer, and a current lead portion extending from the terminal portion and connected to the external connection terminal. And the resistance value of the current lead portion is larger than the connection resistance value between the terminal portion and the superconducting layer.
Since the connection resistance between the terminal portion and the superconducting layer is made by, for example, solder or the like, the connection resistance varies about several nΩ. According to the above configuration, it is possible to relatively reduce variation in connection resistance by generating a large resistance value with respect to variation in connection resistance between the terminal portion and the superconducting layer in the current lead portion. As a result, the resistance value of the current lead portion becomes the dominant factor as a factor for determining the ratio of the current flowing in each superconducting layer (ie, the shunt ratio). Since the resistance of the current lead portion can be easily controlled, the shunt ratio can be easily controlled.

In the terminal structure of the superconducting cable, the connection member may have a resistance value of the current lead portion of 16 times or more with respect to a connection resistance value between the terminal portion and the superconducting layer.
According to this configuration, it is possible to extremely reduce the influence of the variation in the connection resistance on the shunt ratio by generating a resistance value of 16 times or more the connection resistance between the terminal portion and the superconducting layer in the current lead portion. it can. As a result, it is possible to suppress a difference in the value of the current flowing through each superconducting layer.

In the terminal structure of the superconducting cable, a resistance value of the current lead portion may be 1.6 μΩ or more and 100 μΩ or less.
The connection resistance between the terminal portion and the superconducting layer is, for example, about 1 nΩ to 100 nΩ. By setting the lead resistance value to 1.6 μΩ or more, the influence of variation in connection resistance on the shunt ratio can be extremely reduced. As a result, it is possible to suppress a difference in the value of the current flowing through each superconducting layer. Moreover, the loss of the electric power by resistance can be suppressed by making resistance value of a current lead part into 100 microhm or less.

In the terminal structure of the superconducting cable, the superconducting cable may be a superconducting cable for allowing a direct current to flow.
The difference in current flowing through each superconducting layer due to the connection resistance between the terminal portion and the superconducting layer becomes more prominent when a direct current is passed through the superconducting cable. Therefore, it is preferable to employ the above terminal structure for a superconducting cable for passing a direct current.

  According to the present invention, it is possible to relatively reduce the variation in connection resistance by generating a large resistance value for the variation in connection resistance between the terminal portion and the superconducting layer in the current lead portion. As a result, the resistance value of the current lead portion becomes the dominant factor as a factor for determining the ratio of the current flowing in each superconducting layer (ie, the shunt ratio). Since the resistance of the current lead portion can be easily controlled, the shunt ratio can be easily controlled.

It is a partial section schematic diagram showing the structure of a superconducting cable with which the terminal structure of an embodiment is adopted. It is a side view of the terminal structure of an embodiment. It is a fragmentary sectional view of the terminal structure of an embodiment. It is a perspective view of the connection member of an embodiment. It is a current model of a terminal structure. It is a simulation result of the voltage drop which arises in the 1st, 2nd wire rod layer based on the current model shown in FIG. 6 is a simulation result of the length of the current lead portion and the total current based on the current model shown in FIG. 5. It is a side view of the conventional terminal structure. It is a fragmentary sectional view of the conventional terminal structure. It is a simulation result of the electric current which flows into each layer at the time of flowing an electric current through the conventional terminal structure shown in FIG. 8, FIG.

  Hereinafter, embodiments of an oxide superconducting wire according to the present invention will be described with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

FIG. 1 shows a partial cross-sectional schematic view of a superconducting cable 1 which is an example of a superconducting cable that can employ the terminal structure of the present embodiment.
The superconducting cable 1 has a cable core 85 and a metal heat insulating double tube 84 that houses the cable core 85.
The heat insulating double tube 84 has flexibility. The heat insulating double tube 84 includes an inner tube 84a and an outer tube 84c, and a vacuum heat insulating layer 84b is formed between the inner tube 84a and the outer tube 84c, thereby eliminating the influence of heat from the outside. It has a structure to do. A cable core 85 is accommodated inside the inner pipe 84a with a gap 87 for circulating the refrigerant.

The cable core 85 has a structure in which a plurality of layers are concentrically stacked, and in order from the inside, a former (core material) 81, a first wire layer 6, an insulating layer 82, a second wire layer 7, A cable stabilizing layer 86 and a protective layer 83 are provided.
The former 81 is made of a stranded wire made of metal (for example, copper).
The first wire layer (superconducting layer) 6 is formed by spirally winding a plurality of tape-shaped superconducting wires 2 around a former 81.
An insulating layer 82 is formed around the first wire layer 6 to insulate the inner layer (first wire layer 6) and the outer layer (second wire layer 7) of the insulating layer 82. .
Similar to the first wire layer 6, the second wire layer (superconducting layer) 7 is formed by spirally winding a plurality of tape-shaped superconducting wires 3. The superconducting wire 3 constituting the second wire layer 7 may be the same wire as the superconducting wire 2 constituting the first wire layer 6 or may be wider than the superconducting wire 2. FIG. 1 shows an example in which the spiral directions of the superconducting wire 2 of the first wire layer 6 and the superconducting wire 3 of the second wire layer 7 are matched, but the spiral directions may be opposite to each other. .
The first and second wire layers 6 and 7 function as a superconductor layer formed inside the superconducting cable 1 and are insulated from each other by an insulating layer 82.
The cable stabilization layer 86 is made of a conductive metal and plays a role of stabilizing the current flowing through the cable. The protective layer 83 serves to protect the cable core 85 from the refrigerant.

The tape-shaped superconducting wires 2 and 3 of the present embodiment are RE123-based oxide superconducting wires in which an alignment intermediate layer, an RE-based superconducting layer, and a stabilizing layer are formed on a metal substrate, and the dimensions are 3 to 3 in width. The thickness is about 10 mm and the thickness is about 0.5 mm. A bismuth-based multi-core oxide superconducting wire can also be applied.
The superconducting wires 2 and 3 are spirally wound in the superconducting cable 1 so that the metal substrate is disposed inside and the stabilization layer is disposed outside.

  In the present embodiment, the wire layer formed by spirally winding the superconducting wires 2 and 3 has a two-layer structure of the first wire layer 6 and the second wire layer 7, but more than this. These layers may be formed. Further, a superconducting shield layer may be formed on the outer periphery of the second wire layer 7 via an insulating layer. In this case, a wire similar to the superconducting wires 2 and 3 of the first and second wire layers 6 and 7 can be spirally wound as the superconducting shield layer. By providing the superconducting shield layer, the electromagnetic field generated by the current that can flow through the superconducting conductor layer can be canceled out so that the influence of the electromagnetic field does not affect the outside of the superconducting cable 1.

FIG. 2 shows a side view of the terminal structure 10 of the superconducting cable 1 of the embodiment, and FIG. 3 shows a sectional view of the terminal structure 10.
The terminal structure 10 includes the above-described superconducting cable 1, connection members 4, 5 attached to the first and second wire layers 6, 7 of the superconducting cable 1, and external connections electrically connected to the connection members 4, 5. And a connection terminal 11.
Although not shown, the superconducting cable 1 has a structure in which the superconducting wires 2 and 3 of the first and second wire layers 6 and 7 can be cooled by a refrigerant until reaching the terminal portion 1a. .

  The external connection terminal 11 is an external power source (for example, a power generation device that supplies electric power) itself, or a terminal connected to the external power source. It is what flows. The current supplied from the external connection terminal 11 flows through the first and second wire layers 6 and 7 through the connection members 4 and 5, respectively.

  In the terminal portion 1a of the superconducting cable 1, the first and second wire layers 6 and 7 and the former 81 are exposed stepwise. Connection members 4 and 5 are attached to the exposed portions of the first and second wire layers 6 and 7.

FIG. 4 shows a perspective view of the connection member 4.
The connecting member 4 includes a cylindrical terminal portion 4A and a current lead portion 4B protruding from the outer peripheral surface of the terminal portion 4A. As a material constituting the connection member 4, for example, copper or copper alloy can be employed.

The inner diameter portion 4Aa of the terminal portion 4A has a size that matches the outer diameter of the first wire layer 6 to which the connecting member 4 is attached. In addition, a hole 4Ab penetrating from the outer peripheral portion to the inner diameter portion 4Aa is formed in the terminal portion 4A. The hole 4Ab is provided for pouring the solder 12 in a state in which the first wire layer 6 exposed at the terminal portion 1a of the superconducting cable 1 is inserted into the inner diameter portion 4Aa of the connecting member 4.
Since the superconducting wire 2 of the first wire layer 6 has the base material on the inner peripheral side and the stabilization layer on the outer peripheral side, soldering is performed between the outer periphery of the first wire layer 6 and the inner diameter portion 4Aa of the terminal portion 4A. By flowing 12 in, the connection member 4 and the first wire layer 6 are electrically connected. Moreover, the solder 12 is spread over the entire outer periphery of the first wire layer 6, and the plurality of superconducting wires 2 constituting the first wire layer 6 are short-circuited via the solder 12 and the terminal portion 4 </ b> A.

  The current lead portion 4B is formed to extend in a square bar shape from the outer periphery of the terminal portion 4A. The current lead portion 4B is formed to have a width W, a depth L, and a length D. As an example, the width W can be 10 mm, the depth L can be 50 mm, and the length D can be 100 cm.

The connection member 5 has the same structure as that of the connection member 4 and includes a terminal portion 5A and a current lead portion 5B.
The inner diameter portion 5Aa of the terminal portion 5A has a size that matches the outer diameter of the second wire layer 7 to which the connecting member 5 is attached. The solder 12 can be filled between the inner diameter portion 5Aa of the connection member 5 and the second wire layer 7. Thereby, the connection member 5 and the second wire layer 7 are electrically connected, and all the plurality of superconducting wires 3 constituting the second wire layer 7 are short-circuited.
The current lead portion 5B is formed with a width W, a depth L, and a length D. For example, as with the current lead portion 4B, the current lead portion 4B has a width W of 10 mm, a depth L of 50 mm, and a length D. Can be 100 cm.

  As shown in FIGS. 2 and 3, in the terminal structure 10, the bonding between the terminal portion 4 </ b> A and the first wire layer 6 and the bonding between the terminal portion 5 </ b> A and the second wire layer 7 are performed via solder 12. . In such a solder joint, the connection resistance becomes very small, about 1 nΩ to 100 nΩ, and it is difficult to accurately control this. That is, it is difficult to make the connection resistance between the terminal portion 4A and the first wire layer 6 and the connection resistance between the terminal portion 5A and the second wire layer 7 the same. Therefore, the first wire layer 6 and the second wire layer 7 are connected to the external connection terminal 11 that supplies current by a different connection resistance. Since the superconducting wires 2 and 3 constituting the first and second wire layers 6 and 7 have a resistance value of 0 at a low temperature, even if a slight difference in connection resistance occurs, the current flowing through each of the superconducting wires 2 and 3 changes greatly. End up.

  In the terminal structure 10 of the present embodiment, the length D of the current lead portions 4B and 5B of the connection members 4 and 5 is increased (100 cm in the present embodiment), and the resistance values of the current lead portions 4B and 5B are set to the terminal portions. The connection resistance between 4A and the first and second wire layers 6 and 7 via the solder 12 is set larger. In the current lead portions 4B and 5B, a large resistance value is generated with respect to the variation in connection resistance between the terminal portion 4A and the first and second wire layers 6 and 7, thereby relatively reducing the variation in connection resistance. Can do. As a result, the resistance value of the current lead portions 4B and 5B becomes the dominant factor as a factor for determining the ratio of currents flowing through the first and second wire layers 6 and 7 (that is, the shunt ratio). Since the resistance of the current leads 4B and 5B can be easily controlled, the shunt ratio can be easily controlled.

The resistance values of the current lead parts 4B and 5B are preferably 16 times or more than the connection resistance value between the terminal parts 4A and 5A and the first and second wire layers 6 and 7. By generating a resistance value of 16 times or more with respect to the connection resistance between the terminal portions 4A and 5A and the first and second wire layers 6 and 7, the connection resistance becomes negligibly small, and the current lead portions 4B and 5B. The shunt ratio can be determined according to the ratio of the resistance values.
Further, if the current lead portions 4B and 5B have too large resistance values, the energy loss due to the resistance component increases, so that this resistance value is the connection between the terminal portions 4A and 5A and the first and second wire layers 6 and 7. It is preferable that the resistance value is 10,000 times or less.

  The resistance values of the current leads 4B and 5B are preferably 1.6 μΩ or more. Since the connection resistance between the terminal portions 4A and 5A and the first and second wire layers 6 and 7 is, for example, about 1 nΩ to 100 nΩ, by setting the resistance value of the current lead portions 4B and 5B to 1.6 μΩ or more, The influence of variation in connection resistance can be extremely reduced. Moreover, the loss of the electric power by resistance can be suppressed by making resistance value of current lead part 4B, 5B into 100 microhm or less.

  In order to secure the resistance value of the current leads 4B and 5B, an external resistor may be inserted in the current path of the current leads 4B and 5B. However, as shown in the present embodiment, when connecting members 4 and 5 made of the same material (for example, copper) are used, the resistance D is increased by increasing the length D of the current path of the current lead portions 4B and 5B. A value can be secured.

The terminal structure 10 is suitably used for a superconducting cable for passing a direct current.
When a direct current is passed through the superconducting cable 1, an induced voltage due to inductance does not occur, so the resistance component becomes the dominant factor that determines the shunting. On the other hand, when an alternating current is passed through the superconducting cable 1, an induced voltage due to inductance is generated in the superconducting cable 1. Since this induced voltage is sufficiently larger than the voltage caused by the resistance of the terminal portion 1a, the influence of the resistance component on the shunt is reduced. Therefore, a great effect can be obtained by adopting the terminal structure 10 in the superconducting cable 1 for flowing a direct current. Note that the terminal structure 10 may be employed in a superconducting cable for passing an alternating current, and in this case, a certain effect can be obtained.

Next, simulation results when a direct current is passed through the superconducting cable 1 having such a terminal structure 10 will be described as an example.
FIG. 5 shows a current model 20 of the superconducting cable 1 having the terminal structure 10.
This current model 20 is a model that assumes the terminal structure 10 shown in FIG. 2, and is connected to the first wire layer 6 and the second wire layer 7 that are arranged in parallel from the external connection terminal 11 as a DC power source, respectively. The terminal structure 10 of the superconducting cable 1 connected via 5 is shown.

In the first and second wire layers 6 and 7, a voltage drop V = Vc (I / Ic) ⁿ peculiar to the superconductor occurs. Vc is a reference voltage of the superconductor, I is a current value flowing through the first and second wire layers 6 and 7, and Ic is a critical current value of the first and second wire layers 6 and 7, respectively. . In this current model 20, the critical current value Ic is 6000 A for each superconducting layer.

  The terminal portions 5A and 5A have different resistance values as connection resistances with the first and second wire layers 6 and 7, respectively. In this simulation, the resistance value between the terminal portion 4A and the first wire layer 6 which is the inner superconducting layer is 50 nΩ, and the resistance value between the terminal portion 5A and the second wire layer 7 which is the outer superconducting layer is 0. .

The current leads 4B and 5B generate resistance as a resistance component. In this simulation, calculation was performed based on the volume resistivity of copper, assuming that the material of the current lead portions 4B and 5B is copper. Further, the current leads 4B and 5B both have a width W of 10 mm, a depth L of 50 mm (that is, the current path has a cross-sectional area of 50 mm ² ), and the entire current when the length D is varied is investigated. did. The temperature was 77K. This result will be described with reference to FIGS.

FIG. 6 shows, as an example, when the length D of the current leads 4B and 5B is 10 cm, the horizontal axis represents the total current flowing through the first and second wire layers 6 and 7, and the first and second wire layers 6 , 7 are graphs of simulation results with voltage drops occurring in the vertical axis as vertical axes.
In this example, the voltage drop generated in the first and second wire layers 6 and 7 is the same when the total current is in the range of 0 A to about 7000 A. This means that an equivalent current flows through the first and second wire layers 6 and 7. However, when the total current exceeds about 7000 A, the voltage generated in the second wire layer 7 rapidly increases. On the other hand, the voltage generated in the first wire layer 6 changes stably even when it exceeds 7000A, rises from 11000A, and rises.
There is a connection resistance of 50 nΩ between the first wire layer 6 and the terminal portion 4A. On the other hand, the connection resistance between the second wire layer 7 and the terminal portion 5 </ b> A is 0, and the second wire layer 7 tends to flow current to the first wire layer 6. In this example, when the current exceeds 7000 A, current flows concentrated on the second wire layer 7, and a voltage drop V = Vc (I / Ic) ⁿ peculiar to the superconductor is generated in the second wire layer 7. The voltage drop becomes large.

The reference voltage Vc (1 μV) is shown in the graph of FIG. The reference voltage Vc is a reference voltage for determining the critical current value Ic of the superconductor. When the voltage drop reaches the reference Vc, the current flowing through the superconductor becomes a critical current value Ic, and the current flowing through the superconducting wire approaches a limit. Therefore, the voltage drop of each superconducting layer is preferably set to Vc or less.
In the example shown in FIG. 6, since the second wire layer 7 has reached the reference voltage Vc at about 7000 A, it is desired to pass a current in a region below this. Therefore, as shown in FIG. 6, when the length D of the current leads 4B and 5B is 10 cm, a current of up to about 7000 A can be passed through the superconducting cable 1 as a total current.

  FIG. 7 shows the total current that can be passed through the superconducting cable 1 when the length D of the current lead portions 4B and 5B is variously changed between 0 cm and 100 cm. The “total current that can flow through the superconducting cable 1” means the total current when the voltage drop of the reference voltage Vc occurs in the second wire layer 7 in the current model 20.

As shown in FIG. 7, the total current that can be passed through the superconducting cable 1 can be increased by increasing the length D of the current leads 4B and 5B.
When the length D of the current lead parts 4B and 5B is 40 cm or more, a current of 8500 A or more can be passed as the entire current. Since the critical current value Ic of the first and second wire layers 6 and 7 of this superconducting cable 1 is 6000 A, a current of 70% or more can flow through the critical current.
On the other hand, when the total current is less than 8500 A, only a current less than 70% can flow with respect to the critical current, and more than 30% with respect to the ability of the superconducting cable 1 (ie, the critical current value Ic). It will be wasted and inefficient.
Therefore, in the current model 20, the length D of the current lead parts 4B and 5B is preferably 40 cm or more. That is, by setting the length D to 40 cm or more, a current is efficiently passed when the difference in connection resistance between the first wire layer 6 and the terminal portion 4A and between the second wire layer 7 and the terminal portion 5A is up to 50 nΩ. be able to.

Further, when the length D of the current lead portions 4B and 5B is 40 cm or more, the resistance value of the current lead portions 4B and 5B is 1.6 μΩ (temperature 77K). From this simulation result, it was confirmed that the resistance value of the current lead portions 4B and 5B is preferably 1.6 μΩ.
The current leads 4B and 5B may be used at a temperature of 77K or higher. In that case, the current leads 4B and 5B may be adjusted to 1.6 μΩ or higher by adjusting the cross-sectional area and length of the current leads.

  Each embodiment of the present invention has been described above, but each configuration and combination thereof in each embodiment is an example, and the addition, omission, replacement, and configuration of the configuration is within the scope of the present invention. Other changes are possible. Further, the present invention is not limited by the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Superconducting cable, 1a ... Terminal part, 2, 3 ... Superconducting wire, 4, 5 ... Connection member, 4A, 5A ... Terminal part, 4Aa, 5Aa ... Inner diameter part, 4Ab, 5Ab ... Hole, 4B, 5B ... Current lead Part 6, first wire layer (superconducting layer), 7 second wire layer (superconducting layer), 10 terminal structure, 11 external connection terminal, 12 solder, 20 current model, 81 former (core material) ), 82 ... insulating layer, D ... length, L ... depth, W ... width

Claims (4)

A superconducting cable terminal structure in which a plurality of superconducting layers are laminated around an insulating layer around a core material,
A plurality of connection members connected to each superconducting layer on a one-to-one basis, and external connection terminals,
Each of the connection members has a terminal portion connected to the superconducting layer, and a current lead portion extending from the terminal portion and connected to the external connection terminal,
A terminal structure of a superconducting cable in which a resistance value of the current lead portion is larger than a connection resistance value between the terminal portion and the superconducting layer.   2. The terminal structure of a superconducting cable according to claim 1, wherein the connection member has a resistance value of the current lead portion that is 16 times or more of a connection resistance value between the terminal portion and the superconducting layer.   The terminal structure of the superconducting cable according to claim 1 or 2, wherein a resistance value of the current lead portion is 1.6 µΩ or more and 100 µΩ or less.   The terminal structure of a superconducting cable according to any one of claims 1 to 3, wherein the superconducting cable is a superconducting cable for allowing a direct current to flow.

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