Connection structure and connection method for superconducting cables

Abstract

To suppress reduction in electrification performance in a connection structure in a terminal portion of a superconducting cable.SOLUTION: A connection structure for a superconducting cable comprises at least a multilayer conductor 10, which is configured by laminating a plurality of tape-like superconducting wire rods 20 in a tape thickness direction, and an electrode part 30 which is connected with an end of the multilayer conductor 10. The multilayer conductor 10 is separated into a first region 10A constituting an intermediate portion of the superconducting cable and a second region 10B constituting a connection portion with the electrode part 30. In the first region 10A, at least an FFDS unit 12 is included which is configured by disposing two superconducting wire rods 20 in such a manner that faces of the superconducting wire rods 20 on the side of a substrate 21 are turned outside. In the second region 10B, a BBDS unit 13 which is configured by disposing two superconducting wire rod 20 in such a manner that faces of the superconducting wire rods on the side of the substrate 21 are opposed to each other is individually stored in a slit 40 which is provided in the electrode part 30. Thus, the merit obtained by an FFDS structure is made compatible with the merit obtained by a BBDS structure, thereby contributing to suppression of reduction of in electrification performance.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a connection structure and a connection method for a superconducting cable.

Background Art

[0002] As a superconducting cable for transmitting power to equipment using superconductivity (hereinafter, also simply referred to as "superconducting equipment"), a method using a laminated conductor formed by laminating a plurality of tape-shaped superconducting wire materials described in Patent Document 1 and the like has been developed. According to this method, since it is possible to reduce the weight compared to conventional superconducting cables such as three-phase coaxial type and three-core integrated type, it can be expected to be used for superconducting cables for aircraft etc. where weight constraints are severe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When connecting a superconducting cable using a laminated conductor to a superconducting device, it is necessary to connect the end of the laminated conductor to an electrode portion provided in a connection terminal having a shape corresponding to the connection to the superconducting device. However, after connecting the laminated conductor to the electrode portion, there is a problem that the energization performance (current value) measured by actual measurement is lower than the designed energization performance (current value) determined by the energization performance of the single superconducting wire material and the product of the number of laminated layers. This is considered to be because it is difficult to secure an energization path (connection cross-sectional area) when the superconducting layer of the superconducting wire material located particularly inside the lamination direction among the plurality of superconducting wire materials constituting the laminated conductor is at a position away from the electrode portion, and an electric current imbalance occurs.

[0005] Therefore, one of the objectives of the present invention is to provide a means that can suppress a decrease in current-carrying performance in a connection structure at the terminal portion of a superconducting cable. [Means for solving the problem]

[0006] The present invention, made to solve the above problems, is a connection structure for the terminal portion of a superconducting cable, comprising at least a laminated conductor, which is tape-shaped and has at least a substrate, an intermediate layer, a superconducting layer, and a stabilizing layer in the tape thickness direction, and is formed by laminating a plurality of superconducting wires in the thickness direction of the superconducting wires, and an electrode portion that connects to the end of the laminated conductor, wherein the electrode portion has at least a plurality of slits, and the laminated conductor is divided into at least a first region that constitutes the intermediate portion of the superconducting cable and a second region that connects to the electrode portion, wherein the first region is configured to include at least an FFDS unit formed by arranging two superconducting wires so that the substrate-side surfaces of each superconducting wire face outward from each other, and the second region is characterized in that a BBDS unit formed by arranging two superconducting wires so that the substrate-side surfaces of each superconducting wire face each other is housed in at least one of the plurality of slits provided in the electrode portion. [Effects of the Invention]

[0007] According to the present invention, in a connection structure at the terminal portion of a superconducting cable, it is possible to suppress at least a decrease in current-carrying performance. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing an example of the overall configuration of a superconducting cable according to the present invention. [Figure 2] A schematic diagram showing an example of the configuration of a superconducting wire. [Figure 3] A schematic diagram showing an example of the electrode configuration. [Figure 4] A schematic diagram showing an example of housing superconducting wires in a slit. [Figure 5] A schematic diagram showing an example of accommodation related to Experimental Example 1. [Figure 6] A schematic diagram showing an example of accommodation related to Experimental Example 2. [Figure 7] A schematic diagram showing the overall configuration of the superconducting cable according to Example 2. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Examples]

[0010] <1> Overall structure (Figure 1) The superconducting cable connection structure according to the present invention (hereinafter also referred to as "this structure") is a structure applicable to superconducting cables for connecting a power source to a superconducting device or to superconducting devices themselves. In this invention, the term "superconducting cable" is not limited to a configuration in which a shield or insulator is provided on the conductor, but also includes a configuration consisting only of a conductor. In one example shown in Figure 1, the structure comprises at least a laminated conductor 10 that constitutes a superconducting cable, and an electrode portion 30 that constitutes part or all of a connection terminal for connecting the superconducting cable to a power supply, superconducting equipment, etc. The details of each component are described below.

[0011] <2> Multilayer conductor (Figure 1) The laminated conductor 10 is a component that is placed inside the superconducting cable and functions as a conductor for transmitting power in a superconducting state. The laminated conductor 10 is formed by stacking multiple superconducting wires 20 in the thickness direction of the superconducting wires 20. In this invention, the number of superconducting wires 20 constituting the laminated conductor 10 is not particularly limited. In the example shown in Figure 1, the laminated conductor 10 is composed of four superconducting wires 20. When connecting the laminated conductor 10 to the electrode section 30, which will be described later, it is connected to multiple wire units 11, which are smaller units formed by dividing the multiple superconducting wires 20 that make up the laminated conductor 10. The number of superconducting wires 20 constituting the wire unit 11 can be appropriately set within the range excluding the total number of superconducting wires 20 constituting the laminated conductor 10.

[0012] <3>Superconducting wire (Figs. 1, 2) The superconducting wire 20 is a tape-shaped conductive member constituting the laminated conductor 10. In the present invention, the type of the superconducting wire 20 is not particularly limited. In this embodiment, as the superconducting wire 20, a tape-shaped MOD (Metal Organic Deposition Processes) - based wire is used. The superconducting wire 20 shown in Fig. 2 has, in the thickness direction, a substrate 21, an intermediate layer 22, a superconducting layer 23, and a stabilization layer 24 in this order from below the paper surface upward. Hereinafter, the details of each part will be described.

[0013] <3.1>Substrate (Fig. 2) The substrate 21 is a part that serves as the base of the superconducting wire 20. In the present invention, the type of the substrate 21 is not particularly limited. For example, an alloy obtained by adding any one or more elements selected from tungsten (W), tin (Sn), zinc (Zn), molybdenum (Mo), chromium (Cr), vanadium (V), tantalum (Ta), or titanium (Ti) to nickel (Ni) or copper (Cu) can be used.

[0014] <3.2>Intermediate layer (Fig. 2) The intermediate layer 22 is provided between the substrate 21 and the superconducting layer 23, and is a part for preventing the reaction between the substrate 21 and the superconducting layer 23 during the heat treatment when manufacturing the superconducting wire 20. In the present invention, the type and number of layers of the intermediate layer 22 are not particularly limited. For example, ceria (CeO2), manganese oxide (MgO), etc. can be used.

[0015] <3.3>Superconducting layer (Fig. 2) The superconducting layer 23 is a part for conducting electricity in the superconducting state. In the present invention, the type of superconducting layer 23 is not particularly limited, but for example, yttrium oxide superconductor (RE123) can be used. The superconducting layer 23 can be formed, for example, by the MOD method (Metal Organic Deposition Processes).

[0016] <3.4> Stabilization layer (Figure 2) The stabilization layer 24 is formed directly above the superconducting layer 23 to stabilize the superconducting layer. More specifically, the stabilization layer 24 is a component that bypasses current and disperses heat generated by fault current or AC current to prevent damage and performance degradation due to overheating. In the present invention, the type of stabilizing layer 24 is not particularly limited, but precious metals such as silver (Ag), gold (Au), platinum (Pt), or alloys thereof can be used, and it is especially preferable to use a metal with low resistance.

[0017] <4> Electrode section (Figure 1) The electrode portion 30 is a component for connecting the ends of the connection terminals. The electrode portion 30 according to the present invention can be used to supply power transmitted from the laminated conductor 10 to a superconducting device to which a connection terminal is connected. In the present invention, the material of the electrode portion 30 is not particularly limited, but it is especially preferable to use a material with excellent conductivity, such as copper (Cu).

[0018] <5> Slit (Figures 1 and 3) The slit 40 is a portion for housing the end of the superconducting wire 20. The slit 40 consists of a groove formed to communicate with one end of the electrode portion 30. Multiple slits 40 are provided at intervals in the width direction of the slit 40 (the thickness direction of the superconducting wire 20 that is housed within it). Then, superconducting wires 20 that constitute the laminated conductor 10 are placed in each slit 40, and the superconducting wires 20 are fixed to the electrode portion 30 using appropriate joining methods such as soldering. By housing each superconducting wire 20 constituting the laminated conductor 10 in the slit 40 in this manner, the surface of each superconducting wire 20 facing the superconducting layer 23 and the stabilizing layer 24 (one surface 20a) is positioned to contact or approach the electrode portion 30, thereby securing the current flow path (connection cross-sectional area) of each superconducting wire 20 and suppressing the occurrence of electrical current deviation.

[0019] <5.1> Slit width (Figure 3) In the present invention, the width B of the slit 40 is such that it is long enough to accommodate a wire unit 11 consisting of at least one superconducting wire 20 in the thickness direction of the superconducting wire 20. Furthermore, the width B of each slit 40 may be equal in length or different in length.

[0020] <5.2> Slit length (Figure 3) In the present invention, the accommodating length L1 of the slit 40 is not particularly limited. Furthermore, the storage length L1 of each slit 40 may be equal or different.

[0021] <5.3> Distance between slits (Figure 3) In the present invention, the spacing length L2 between the slits 40 is not particularly limited and can be appropriately determined according to the width of the electrode portion 30, the width of the slits 40, and the number of slits 40. Furthermore, the separation length L2 of each slit 40 may be equal or different.

[0022] <5.4> When two superconducting wires are housed in the slit (Figure 4) In the present invention, when a wire unit 11 consisting of two superconducting wires 20 is housed in a single slit 40, it is preferable that, for the two superconducting wires 20 located on both sides of the wire unit 11, the surface of each superconducting wire 20 facing the superconducting layer 23 and stabilizing layer 25 (one surface 20a) is oriented toward the inner wall side of the slit 40, i.e., toward the side closer to the electrode portion 30, and the surfaces facing the substrate 20 (the other surface 20b) are arranged opposite each other. In other words, the two superconducting wires 20 are configured in such a way that their orientations in the thickness direction are swapped. In Figure 4, the wire unit 11, consisting of two superconducting wires 20, is configured such that the orientation of each superconducting wire 20 in the thickness direction is reversed, so that one surface 20a of each superconducting wire 20 faces the side closer to the electrode portion 30.

[0023] This configuration further suppresses the decrease in overall current-carrying performance compared to cases where multiple superconducting wires 20 are housed in the same orientation, or where the surfaces of the superconducting layer 23 and the stabilizing layer 25 (one surface 20a) are arranged facing each other.

[0024] In addition, in the present invention, the number of superconducting wires 20 constituting the wire unit 11 housed in the slit 40 can be appropriately set within a range that satisfies the current-carrying performance required for the superconducting cable as a whole and the size required for the electrode portion 30. For example, if simply connecting the laminated conductor 10 to the electrode section 30 does not satisfy the required current-carrying performance, the superconducting wires of the laminated conductor can be appropriately divided into smaller pieces and housed in the slits of the electrode section 30 to satisfy this current-carrying performance. Furthermore, when multiple superconducting wires are housed in each slit 40, the width of the slits increases compared to when only one superconducting wire is housed in each slit, but the number of slits can be reduced. This allows for a degree of miniaturization of the electrode section 30 while suppressing a certain degree of degradation in current-conducting performance.

[0025] <5.5> Differences in the number of items that can be stored in the slits (not shown) In this invention, in a single electrode section 30, the number of superconducting wires 20 that can be accommodated in each slit 40 may differ, for example, a slit 40 that accommodates one superconducting wire 20 and a slit 40 that accommodates two superconducting wires 20 may be mixed together. This configuration can be applied, for example, when the laminated conductor 10 is composed of an odd number of superconducting wires 20.

[0026] <6> Comparative study [1] (Tables 1-3, Figures 5, 6) A comparative test was conducted on the current-carrying performance (current value) between electrode sections provided at both ends of a superconducting cable, which was constructed by arranging a laminated conductor 10 consisting of eight superconducting wires 20. In this test, the layouts shown in each figure were applied to both ends of the superconducting cable.

[0027] <6.1> Materials Used (Table 1, Table 2) Tables 1 and 2 show the details of each component used.

[0028] [Table 1] TIFF0007853346000001.tif40151

[0029] [Table 2] TIFF0007853346000002.tif45151

[0030] <6.2> Layout Examples (Figures 5 and 6) Regarding the end structure of the superconducting cable, the layout of the slit 40 and the superconducting wire 20 was set to one of the following two types.

[0031] (1) Experimental example 1 (Figure 5) A laminated conductor 10 consisting of eight superconducting wires 20 is housed in a slit 40 provided in the electrode section 30. When four adjacent superconducting wires 20 make up the laminated conductor 10, the wires are arranged such that in each wire unit 11, the surface of each superconducting wire 20 facing the substrate 21 (the other surface 20b) faces inward as part of the laminated conductor 10, and the surface facing the superconducting layer 23 and the stabilizing layer 24 (not shown in Figure 5) (one surface 20a) faces the inner wall of the slit 40.

[0032] (2) Experimental example 2 (Figure 6) Four slits 40 were provided in the electrode section 30, and each slit contained a wire unit 11 consisting of two superconducting wires 20. The two superconducting wires 20 housed in the same slit 40 were arranged so that the side facing the superconducting layer 23 and the stabilizing layer 24 (one side 20a) faced the inner wall of the slit 40.

[0033] <6.3> Test Results (Table 6) Table 3 shows the measured current values ​​and their ratios to the design current values ​​in experimental examples 1 and 2. [Table 3] As shown in Table 3 of TIFF0007853346000003.tif33151, it was found that by dividing the superconducting wire into smaller portions and housing them in the slits 40 formed within the electrode portion 30, the measured current value approaches the design current value, and the deterioration of current-carrying performance is suppressed. Although this comparative test did not include an experiment in which each superconducting wire 20 was placed in a slit 40, it is clear that in this configuration, the side of each superconducting wire 20 facing the stabilization layer 24 will always face the inner wall of the slit 40. Therefore, it is considered that it would be possible to secure measured current values ​​equivalent to or better than those in Experimental Example 2. [Examples]

[0034] <1> Overall structure (Figure 7) Next, an example of a connection structure for a superconducting cable according to the present invention will be described with reference to Figure 7. In this embodiment, the laminated conductor 10 is divided into a first region 10A and a second region 10B, and the combination and arrangement of each superconducting wire 20 differs in each region. The details of each area are explained below.

[0035] <2> First region (Figure 7) The first region 10A is the region that constitutes the middle part of superconducting cable A. In this invention, the first region 10A is configured to include multiple units, each unit being formed by combining two superconducting wires 20 from a plurality of superconducting wires 20 that constitute the laminated conductor 10. Each of the two superconducting wires 20 in each unit is positioned so that the two surfaces of the superconducting wire 20 in the thickness direction are facing each other, with the surfaces on the superconducting layer 23 side (one surface 20a) facing each other, and the surfaces on the substrate 21 side (the other surface 20b) facing the inner wall side of the slit 40 (i.e., the side closer to the electrode portion 30). In this invention, the above configuration is defined as an FFDS (Face to Face Double Stack) structure, and a unit exhibiting this FFDS structure is defined as an FFDS unit 12. In this embodiment (Figure 7), five sets of FFDS units 12 are formed from ten superconducting wires 20 in the first region 10A.

[0036] <2.1> Advantages of the FFDS structure As in the present invention, by configuring the first region 10A to include the FFDS unit 12, at least one of the following advantages can be obtained. (1) Because the FFDS unit has two substrates 21, its strength is simply improved compared to a single superconducting wire. (2) The two superconducting layers 23 are concentrated towards the center in the thickness direction of the FFDS unit 12, thereby improving the bending strength. (3) Since the two superconducting layers 23 are concentrated towards the center in the thickness direction of the FFDS unit 12, even if a localized defect exists in one of the superconducting layers 23, the current can be routed through the other superconducting layer 23 to bypass the defect, thereby ensuring a current flow path and suppressing a decrease in current flow performance.

[0037] <3> Second area (Figure 7) The second region 10B is the region that constitutes the connection portion with the electrode portion 30 in the superconducting cable A. In this invention, the second region 10B is constructed by mixing units made by combining two superconducting wires 20 from a plurality of superconducting wires 20 that constitute the laminated conductor 10 with a single superconducting wire 20. Each of the two superconducting wires 20 in each unit is configured such that the two surfaces of the superconducting wire 20 in the thickness direction, one of which is the surface on the superconducting layer 23 side (one surface 20a), faces the inner wall side of the slit 40 (i.e., the side closer to the electrode portion 30), while the surfaces on the substrate 21 side (the other surface 20b) are facing each other. In this invention, the above configuration is defined as a BBDS (Back to Back Double Stack) structure, and a unit exhibiting a BBDS structure is defined as a BBDS unit 13. In this embodiment (Figure 7), of the five sets of FFDS units 12 that constitute the first region 10A, one superconducting wire is separated from adjacent FFDS units and combined with them to form four sets of BBDS units 13. Furthermore, there are two sets of superconducting wires 20, each consisting of one superconducting wire 20 remaining from the FFDS units on the upper and lower sides of the paper in the first region 10A, and these are individually housed in the slits 40 of the electrode section 30.

[0038] <3.1> Advantages of the BBDS structure As in the present invention, by configuring the second region 10B to include the BBDS unit 13, the decrease in total current-carrying performance can be further suppressed compared to the case where the FFDS unit 12 prepared in the first region 10A is housed in the slit 40 of the electrode portion 30.

[0039] <4> Connection method An example of a method for connecting superconducting wires to realize this structure is described below. Note that the following methods may be combined as appropriate, within the limits of what is consistent with the work.

[0040] <4.1>Connection Method 1 This method involves taking one superconducting wire 20 from each of the two FFDS units 12 that constitute a part of the first region 10A, and arranging them so that the substrate 21-side faces of each superconducting wire 20 face each other, thereby forming one BBDS unit 13 in the second region 10B, and repeating this procedure as needed.

[0041] <4.2> Connection Method 2 This method involves first housing the BBDS units 13 in the slits 40 of the electrode section 30, then, outside the electrode section 30, taking out one superconducting wire 20 from each BBDS unit 13 and arranging the superconducting layer 23-side faces of each superconducting wire 20 to form an FFDS unit 12, and repeating this procedure as needed. Furthermore, the FFDS unit 12 formed from the BBDS unit 13 of the second region 10B using this method may be used as is in the first region 10A, or it may be joined to a separate FFDS unit 12 prepared separately as the first region 10A.

[0042] <5> summary As explained above, the superconducting cable connection structure according to the present invention can further suppress the deterioration of current conduction performance by combining the advantages obtained by the FFDS structure and the advantages obtained by the BBDS structure. [Explanation of Symbols]

[0043] 10: Multilayer conductor 10A: First area 10B:Second area 11: Wire Unit 12: FFDS Unit 13: BBDS Unit 20: Superconducting wire 20a: One side 20b: The other side 21: Circuit board 22: Middle Class 23: Superconducting layer 24: Stabilization layer 30: Electrode part 40: Slit B: Slit width L1: Slit length L2: Distance between slits

Claims

1. A connection structure at the terminal portion of a superconducting cable, A laminated conductor is formed by stacking multiple superconducting wires, each having a tape-like shape and comprising at least a substrate, an intermediate layer, a superconducting layer, and a stabilizing layer in the thickness direction of the tape, in the thickness direction of the superconducting wire. It comprises at least an electrode portion connected to the end of the laminated conductor, The electrode portion has at least multiple slits, The laminated conductor comprises at least, The first region and the intermediate portion of the superconducting cable, It is divided into a second region that connects to the electrode portion, The first region is, The system is configured to include at least an FFDS unit, which is made up of two superconducting wires arranged so that the substrate-side surfaces of each superconducting wire face outwards from each other. The second region is, A BBDS unit, comprising two superconducting wires arranged so that the substrate-side surfaces of each superconducting wire face each other, is housed in at least one of a plurality of slits provided in the electrode portion. Connection structure of a superconducting cable.

2. A method for obtaining the superconducting cable connection structure described in claim 1, In the first region, in two adjacent FFDS units, The BBDS unit in the second region is characterized by combining the superconducting wire from one FFDS unit on the other FFDS unit side with the superconducting wire from the other FFDS unit on the one FFDS unit side. How to connect superconducting cables.

3. A method for obtaining the superconducting cable connection structure described in claim 1, The BBDS unit is pre-hoarded in at least two of the multiple slits provided in the electrode portion. The superconducting wire located on the other slit side of the BBDS unit housed in one slit and the superconducting wire located on the one slit side of the BBDS unit housed in the other slit are brought together outside the electrode section to form an FFDS unit relating to the first region, or are joined to a separately prepared FFDS unit relating to the first region. How to connect superconducting cables.

Images