Connection structure for superconducting cable and connection method

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 superconducting cables. [Background technology]

[0002] A method has been developed that uses a laminated conductor made by stacking multiple tape-shaped superconducting wires, as described in Patent Document 1, etc., as a superconducting cable for transmitting electricity to equipment that utilizes superconductivity (hereinafter simply referred to as "superconducting equipment"). This method makes it possible to reduce the weight of superconducting cables compared to conventional superconducting cables such as three-phase coaxial or three-core in one type, and is therefore expected to be useful in superconducting cables for aircraft, which have strict weight restrictions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-125436 Summary of the Invention [Problem to be solved by the invention]

[0004] When connecting a superconducting cable using a laminated conductor to superconducting equipment, the end of the laminated conductor must be connected to an electrode portion provided within a connection terminal having a shape corresponding to connection to the superconducting equipment. However, after connecting the laminated conductor to the electrode, there was a problem in that the actual measured electrical performance (current value) was lower than the designed electrical performance (current value) determined by the product of the electrical performance of the superconducting wire alone and the number of layers. This is thought to be due to the fact that when the superconducting layer of the superconducting wire, particularly that located on the inner side in the stacking direction, is located away from the electrode section, it is difficult to secure a current path (connection cross-sectional area), resulting in electrical imbalance.

[0005] Therefore, one of the objects of the present invention is to provide a means capable of suppressing 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, which has been made to solve the above-mentioned problems, is a connection structure for a terminal portion of a superconducting cable, and comprises at least a laminated conductor formed by stacking multiple superconducting wires in the thickness direction of the superconducting wire, each superconducting wire having at least a substrate, an intermediate layer, a superconducting layer, and a stabilizing layer in the tape thickness direction, and an electrode portion connected to an 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 an intermediate portion of the superconducting cable and a second region that connects to the electrode portion, the first region being 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 each other outward, and the second region being configured to accommodate a BBDS unit formed by arranging two superconducting wires so that the substrate-side surfaces of each superconducting wire face each other, in at least one of the multiple slits provided in the electrode portion. [Effects of the Invention]

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

[0008] [Figure 1] 1 is a schematic diagram showing an example of the overall configuration of a superconducting cable according to the present invention. [Figure 2] FIG. 1 is a schematic diagram showing an example of the configuration of a superconducting wire. [Figure 3] FIG. 3 is a schematic diagram showing a configuration example of an electrode unit. [Figure 4] FIG. 10 is a schematic diagram showing an example of accommodating a superconducting wire in a slit. [Figure 5] FIG. 1 is a schematic diagram showing a storage example according to Experimental Example 1. [Figure 6] FIG. 10 is a schematic diagram showing a storage example according to Experimental Example 2. [Figure 7] FIG. 10 is a schematic diagram showing the overall configuration of a superconducting cable according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Example]

[0010] <1> Overall configuration (Fig. 1) A superconducting cable connection structure according to the present invention (hereinafter also referred to as "the structure") is a structure that can be applied to a superconducting cable for connecting a power source and superconducting equipment or connecting superconducting equipment together. In the present invention, the term "superconducting cable" is not limited to a configuration in which a shield or an insulator is provided on a conductor, but also includes a configuration consisting of only a conductor. In the example shown in Figure 1, the components of this structure include 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 source, superconducting equipment, etc. Each component will be described in detail below.

[0011] <2> Laminated conductor (Figure 1) The laminated conductor 10 is a member that is disposed inside a superconducting cable and functions as a conductor for transmitting electricity in a superconducting state. The laminated conductor 10 is formed by laminating a plurality of superconducting wires 20 in the thickness direction of the superconducting wires 20 . In the present invention, there is no particular limitation on the number of superconducting wires 20 constituting the laminated conductor 10. In the example shown in FIG. When the laminated conductor 10 is connected to the electrode portion 30 described later, the laminated conductor 10 is connected to each of a plurality of wire units 11 obtained by dividing the plurality of superconducting wires 20 that constitute the laminated conductor 10 into small pieces. The number of superconducting wires 20 constituting the wire unit 11 can be set appropriately within a range excluding the total number of superconducting wires 20 constituting the laminated conductor 10 .

[0012] <3> Superconducting wire (Fig. 1, Fig. 2) The superconducting wire 20 is a tape-shaped conductive member that constitutes the laminated conductor 10 . In the present invention, the type of superconducting wire 20 is not particularly limited. In this embodiment, a tape-shaped MOD (Metal Organic Deposition Processes) type wire is used as the superconducting wire 20 . Superconducting wire 20 shown in FIG. 2 has, in the thickness direction, from bottom to top on the paper, substrate 21, intermediate layer 22, superconducting layer 23, and stabilizing layer 24. Each part will be described in detail below.

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

[0014] <3.2> Middle layer (Figure 2) Intermediate layer 22 is provided between substrate 21 and superconducting layer 23 to prevent reaction between substrate 21 and superconducting layer 23 during heat treatment when superconducting wire 20 is produced. In the present invention, the type and number of layers of the intermediate layer 22 are not particularly limited, but for example, ceria (CeO2) or manganese oxide (MgO) can be used.

[0015] <3.3> Superconducting layer (Fig. 2) The superconducting layer 23 is a portion for passing current in a superconducting state. In the present invention, the type of superconducting layer 23 is not particularly limited, but for example, an yttrium-based oxide superconductor (RE123) or the like can be used. The superconducting layer 23 can be formed by, for example, the MOD method (Metal Organic Deposition Processes: organic acid salt deposition method).

[0016] <3.4> Stabilization layer (Fig. 2) The stabilization layer 24 is formed directly on the superconducting layer 23 to stabilize the superconducting layer. More specifically, the stabilizing layer 24 is a member for diverting electric current and dispersing heat generated by fault current or AC current flow, thereby preventing breakdown and performance degradation due to heat generation. In the present invention, the type of stabilization layer 24 is not particularly limited, but in particular, noble metals such as silver (Ag), gold (Au), platinum (Pt), etc., or alloys thereof can be used, and it is particularly preferable to use a metal with low resistance.

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

[0018] <5> Slit (Figure 1, Figure 3) Slit 40 is a portion for accommodating the end of superconducting wire 20 . The slit 40 is a groove formed so as to communicate with one end side of the electrode part 30 . A plurality of slits 40 are provided at intervals in the width direction of slit 40 (thickness direction of superconducting wire 20 to be accommodated). Then, the superconducting wires 20 constituting the laminated conductor 10 are accommodated in the respective slits 40, and the superconducting wires 20 are fixed to the electrode portions 30 by a suitable joining method such as soldering. By accommodating each superconducting wire 20 constituting the laminated conductor 10 in the slit 40 in this manner, the surface (one surface 20a) of each superconducting wire 20 facing the superconducting layer 23 and the stabilizing layer 24 is positioned so as to contact or be close to the electrode portion 30, thereby ensuring the current path (connection cross-sectional area) of each superconducting wire 20 and suppressing the occurrence of electrical imbalance.

[0019] <5.1> Slit width (Fig. 3) In the present invention, the width B of the slit 40 is set to a length sufficient 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 widths B of the slits 40 may be equal or different.

[0020] <5.2> Slit storage length (Fig. 3) In the present invention, the accommodation length L1 of the slit 40 is not particularly limited. The storage lengths L1 of the slits 40 may be equal or different.

[0021] <5.3> Distance between slits (Fig. 3) In the present invention, the separation length L2 between the slits 40 is not particularly limited, and may be determined appropriately depending on the width of the electrode portion 30, the width of the slits 40, the number of slits 40, and the like. Furthermore, the separation lengths L2 of the slits 40 may be equal or different.

[0022] <5.4> When two superconducting wires are placed in a slit (Fig. 4) In the present invention, when a wire unit 11 consisting of two superconducting wires 20 is accommodated in one slit 40, it is preferable that the two superconducting wires 20 located on both sides of the wire unit 11 are configured such that the surface (one surface 20a) of each superconducting wire 20 facing the superconducting layer 23 and the stabilizing layer 25 faces the inner wall of the slit 40, i.e., the side closer to the electrode portion 30, and the surfaces (the other surfaces 20b) facing the substrate 20 face each other, i.e., the orientation of the two superconducting wires 20 in the thickness direction is reversed, i.e., the orientation of the two superconducting wires 20 in the thickness direction is reversed. In Figure 4, a wire unit 11 consisting of two superconducting wires 20 is configured by swapping the orientation of each superconducting wire 20 in the thickness direction so that one surface 20a of each superconducting wire 20 faces the side closer to the electrode portion 30.

[0023] With this configuration, the deterioration of the total current-carrying performance can be further suppressed compared to when multiple superconducting wires 20 are stored in the same orientation or when the surfaces (one surface 20a) on the superconducting layer 23 and stabilizing layer 25 sides are arranged opposite each other.

[0024] In the present invention, the number of superconducting wires 20 constituting the wire unit 11 accommodated in the slit 40 can be set appropriately within a range that satisfies the required current-carrying performance of the superconducting cable as a whole and the required size of the electrode portion 30. For example, if simply connecting the laminated conductor 10 to the electrode portion 30 does not satisfy the required electrical conductivity, the superconducting wire of the laminated conductor can be divided into appropriate small pieces and placed in the slits of the electrode portion 30 so as to satisfy this electrical conductivity. Furthermore, when multiple superconducting wires are accommodated in each slit 40, the width of the slit increases compared to when one superconducting wire is accommodated in each slit, but the number of slits can be reduced, which creates room for making the electrode section 30 smaller while still suppressing some deterioration in electrical conductivity.

[0025] <5.5> Differences in the number of accommodating persons in the slit (not shown) In the present invention, in one electrode section 30, each slit 40 may have a different number of superconducting wires 20 accommodated therein, for example, a slit 40 that accommodates one superconducting wire 20 and a slit 40 that accommodates two superconducting wires 20 may be mixed. This configuration can be applied, for example, to the case where the laminated conductor 10 is made up of an odd number of superconducting wires 20.

[0026] <6> Comparative test [1] (Tables 1 to 3, Figures 5 and 6) A comparative test was carried out on the current carrying performance (current value) between electrodes provided at both ends of a superconducting cable in which a laminated conductor 10 made of eight superconducting wires 20 was arranged. In this test, the layouts shown in the figures were applied to both ends of the superconducting cable.

[0027] <6.1> Materials used (Table 1, Table 2) Details of each component used are shown in Tables 1 and 2.

[0028] [Table 1] TIFF2025136358000002.tif40151

[0029] [Table 2] TIFF2025136358000003.tif45151

[0030] <6.2> Layout examples (Fig. 5, Fig. 6) Regarding the end structure of the superconducting cable, the layout of the slits 40 and the superconducting wires 20 was set to the following two types.

[0031] (1) Experimental Example 1 (Figure 5) A laminated conductor 10 consisting of eight superconducting wires 20 was housed in one slit 40 provided in the electrode part 30. The eight superconducting wires 20 constituting the laminated conductor 10 were arranged so that, when adjacent four superconducting wires 20 were grouped into wire units 11, the surface of each superconducting wire 20 on the substrate 21 side (the other surface 20b) in each wire unit 11 faced the inside of the laminated conductor 10, and the surface on the superconducting layer 23 and stabilizing layer 24 (not shown in FIG. 5) side (the one surface 20a) faced the inner wall of the slit 40.

[0032] (2) Experimental Example 2 (Figure 6) A wire unit 11 consisting of two superconducting wires 20 was housed in each of four slits 40 provided in the electrode part 30. The two superconducting wires 20 housed in the same slit 40 were arranged so that the surfaces (one surface 20a) on the superconducting layer 23 and stabilizing layer 24 side faced the inner wall of the slit 40.

[0033] <6.3> Test results (Table 6) Table 3 shows the measured current values ​​and the ratios to the design current values ​​in Experimental Examples 1 and 2. [Table 3] TIFF2025136358000004.tif33151As shown in Table 3, it was found that by dividing the superconducting wire into small pieces and storing them in the slits 40 formed in the electrode section 30, the measured current value approaches the design current value, and the deterioration of the current-carrying performance is suppressed. In this comparative test, no experiment was conducted on a configuration in which superconducting wires 20 are housed one by one in slit 40. However, in this configuration, it is clear that the surface of each superconducting wire 20 facing stabilization layer 24 always faces the inner wall of slit 40, and therefore it is believed that an actual current value at least equal to or greater than that of experimental example 2 can be ensured. [Example]

[0034] <1> Overall configuration (Fig. 7) Next, an example of a superconducting cable connection structure according to the present invention will be described with reference to FIG. 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 the superconducting wires 20 differ depending on the region. Each area will be described in detail below.

[0035] <2> First region (Figure 7) The first region 10A is a region that constitutes the middle portion of the superconducting cable A. In the present invention, first region 10A is configured to have a plurality of units, each of which is made up of two superconducting wires 20 that make up laminated conductor 10. The two superconducting wires 20 in each unit are arranged so that the surfaces (one surface 20a) on the superconducting layer 23 side of the two surfaces of the superconducting wire 20 in the thickness direction face each other, while the surfaces (the other surface 20b) on the substrate 21 side face each other toward the inner wall side of the slit 40 (i.e., the side closer to the electrode portion 30). In the present invention, the above configuration is defined as an FFDS (Face to Face Double Stack) structure, and a unit having this FFDS structure is defined as an FFDS unit 12. In this embodiment (FIG. 7), five FFDS units 12 are configured from ten superconducting wires 20 in first region 10A.

[0036] <2.1> Advantages of the FFDS structure By configuring the first area 10A to include the FFDS unit 12 as in the present invention, at least one of the following advantages can be obtained. (1) The FFDS unit has two substrates 21, which simply improves the strength compared to a single superconducting wire. (2) Since the two superconducting layers 23 are concentrated at the center of the thickness direction of the FFDS unit 12, the bending strength is improved. (3) Since the two superconducting layers 23 are concentrated at the center of the thickness direction of the FFDS unit 12, even if a local defect exists in one of the superconducting layers 23, a current path is secured by bypassing the defect through the other superconducting layer 23, thereby suppressing a decrease in current performance.

[0037] <3> Second region (Figure 7) The second region 10B is a region that constitutes a connection portion of the superconducting cable A with the electrode portion 30. In the present invention, second region 10B is configured by mixing units each made up of two of the plurality of superconducting wires 20 that make up laminated conductor 10 with a single superconducting wire 20. The two superconducting wires 20 in each unit are configured so that the surface (one surface 20a) on the superconducting layer 23 side of the two surfaces in the thickness direction of the superconducting wire 20 faces the inner wall side of the slit 40 (i.e., the side closer to the electrode portion 30), while the surfaces (the other surface 20b) on the substrate 21 side are arranged opposite each other. In the present invention, the above configuration is defined as a BBDS (Back to Back Double Stack) structure, and a unit exhibiting the BBDS structure is defined as a BBDS unit 13. In this embodiment (Figure 7), of the five FFDS units 12 that make up the first region 10A, one superconducting wire is separated from adjacent FFDS units and combined with each other to form four BBDS units 13, and further, two sets of superconducting wire 20 are formed, each consisting of one superconducting wire 20 remaining in 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 BBDS structure By configuring the second region 10B to include the BBDS unit 13 as in the present invention, the deterioration of the total electrical conduction performance can be further suppressed compared to when the FFDS unit 12 prepared in the first region 10A is simply housed in the slit 40 of the electrode portion 30.

[0039] <4> Connection Method An example of a method for connecting superconducting wires to achieve this structure will be described below. The following methods may be combined as appropriate within the scope of the work.

[0040] <4.1> Connection method 1 This method involves taking one superconducting wire 20 from each of two FFDS units 12 that form part of the first region 10A, and arranging the surfaces of each superconducting wire 20 facing the substrate 21, thereby appropriately repeating the procedure of forming one BBDS unit 13 in the second region 10B.

[0041] <4.2> Connection method 2 This method involves previously accommodating the BBDS units 13 in the slits 40 of the electrode section 30, then removing one superconducting wire 20 from each BBDS unit 13 outside the electrode section 30, and arranging the surfaces of each superconducting wire 20 facing the superconducting layer 23, thereby appropriately repeating the procedure of forming the FFDS unit 12. In addition, the FFDS unit 12 formed from the BBDS unit 13 of the second region 10B using this method may be used as the first region 10A as is, or may be joined to a separate FFDS unit 12 that is separately prepared as the first region 10A.

[0042] <5> summary As described above, the superconducting cable connection structure of the present invention combines the benefits of the FFDS structure and the benefits of the BBDS structure, thereby further suppressing the decline in current-carrying performance. [Explanation of symbols]

[0043] 10: Laminated 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: Substrate 22: Middle class 23: Superconducting layer 24: Stabilization layer 30: Electrode part 40: Slit B: Slit width L1: Slit storage length L2: Distance between slits

Claims

1. A connection structure at a terminal portion of a superconducting cable, a laminated conductor formed by laminating a plurality of superconducting wires in a thickness direction of the tape, the superconducting wires having at least a substrate, an intermediate layer, a superconducting layer, and a stabilizing layer in the thickness direction of the tape; an electrode portion connected to an end of the laminated conductor; The electrode portion has at least a plurality of slits, The laminated conductor comprises at least a first region constituting an intermediate portion of the superconducting cable; a second region connected to the electrode portion, The first region is The FFDS unit is configured to include at least two superconducting wires arranged such that the substrate-side surfaces of the two superconducting wires face outward, The second region is a BBDS unit, which is formed by arranging two superconducting wires so that the substrate-side surfaces of the superconducting wires face each other, is accommodated in at least one of a plurality of slits provided in the electrode part; Connection structure of superconducting cable.

2. A method for obtaining the superconducting cable connection structure according to claim 1, comprising the steps of: In two adjacent FFDS units in the first region, the BBDS unit in the second region is configured by combining a superconducting wire on the other FFDS unit side of one FFDS unit with a superconducting wire on the one FFDS unit side of the other FFDS unit. How to connect superconducting cables.

3. A method for obtaining the superconducting cable connection structure according to claim 1, comprising the steps of: The BBDS unit is accommodated in advance in at least two slits among the plurality of slits provided in the electrode portion, The superconducting wire located on the other slit side of the BBDS unit accommodated in one slit and the superconducting wire located on the one slit side of the BBDS unit accommodated in the other slit are gathered outside the electrode part to form an FFDS unit related to the first region, or are joined to a separately prepared FFDS unit related to the first region. How to connect superconducting cables.

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