JPH0955241A - Multi-layer superconducting cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the multi-layer superconducting cable which allows AC critical current to be intensified. SOLUTION: In the multi-layer superconducting cable where a plurality of multi-layer superconductors are connected, in which a plurality of superconductor layers are coaxially composed via insulators, each outer layer 14 and 24 of the two multi-layer superconductors to be connected to each other, is connected to the other layer of its mating cable respectively. Therefore, the impedance of each layer is made uniform, so that AC critical current can thereby be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer superconducting cable having an increased AC critical current.

[0002]

2. Description of the Related Art Conventionally, the connection of a multi-layer superconducting cable in which a plurality of superconductor layers are concentrically compounded via an insulating material has been performed by using the same layers such that outer layers are outer layers.

[0003]

When an alternating current is passed through such a multilayer superconducting cable, the alternating current is large because the impedance (sum of resistance and inductance) is different between the outer layer and the other inner layers. A part flows in the outer layer and hardly flows in the inner layer. For example, the current that flows in each layer of a multilayer superconducting cable in which a tape-shaped superconducting wire with a thickness of 0.2 mm is spirally wound into three layers with 20 layers per layer around a former with an outer diameter of 20 mmφ (such as a metal or plastic pipe). The ratio is calculated as: outer layer: middle layer: inner layer = 10: 2: 1
become. The current ratio is calculated using impedance, but in the superconducting state, the AC resistance is 0, so it is determined only by the inductance. Based on the above calculation results, when the critical current Ic per superconducting wire is set to 50 A, and the current P that can flow through the superconducting cable is calculated, P = 50 × 20 × (1+
0.2 + 0.1) = 1300A. Since the current Q when the current uniformly flows in all layers is Q = 50 × 20 × (1 + 1 + 1) = 3000A, the reduction rate R of the AC critical current in the conventional multilayer superconducting cable is R = (Q- P) / Q = (3000-1300) /
It becomes 3000 = 0.57. As described above, the reduction rate R of the AC critical current in the conventional multilayer superconducting cable is extremely large.
An object of the present invention is to provide a multi-layer superconducting cable with increased alternating current critical current.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a multilayer superconducting cable in which a plurality of multilayer superconducting conductors in which a plurality of superconducting layers are concentrically compounded through an insulating material are connected to each other. A multilayer superconducting cable characterized in that one outer layer is connected to another layer of a connection partner.

In the multi-layer superconducting cable of the present invention, the multi-layer superconducting conductors are connected to each other by connecting the outer layers to the other layers of the connection partners. Therefore, the impedance of each layer is made uniform, and the AC critical current of the multilayer superconducting cable increases.

In the present invention, the work of connecting the inner layers can be easily performed by cutting the superconducting layers in the connecting portion of the multilayer superconducting cable. Further, by exposing the insulating material for a predetermined length, insulation between layers in the connection portion can be surely performed.

In the present invention, each layer can be easily connected by using a lead wire. Also, the electric field is shielded by covering the connecting portion with a metal sleeve.

In the present invention, the superconducting wire is a high-temperature superconductor such as bismuth, strontium, calcium, copper oxide, yttrium, barium, copper oxide, or Nb.
Any superconductor such as a Ti alloy or a metal superconductor such as Nb ₃ Sn intermetallic compound is applied. Among them, since the high temperature superconductor has a small critical current (Ic), it is often used as a composite in multiple layers, and the present invention is particularly useful.

[0009]

EXAMPLES The present invention will be described in detail below with reference to examples. (Embodiment 1) FIG. 1 is a side view of a connecting portion showing a first embodiment of a multilayer superconducting cable of the present invention. Reference numeral 10 is a multilayer superconducting conductor, and a superconductor layer of three layers of an inner layer 12, an intermediate layer 13, and an outer layer 14 is spirally formed on a former (for example, spiral for OF cable) 11 with an insulating material 17 interposed between the layers. It is in the form of a roll. Specifically, each of the superconductor layers
12 to 14 are tape-shaped superconducting wires 15 as shown in FIG.
It is formed by winding 20 pieces in a spiral shape. At the end of the multi-layered superconducting conductor 10, each superconducting layer 12-14 is stepped, and at the end of each layer 12-14, a connection ring 16 is attached, and the end of the superconducting conductor is varackle. Is being prevented.
The insulating material 17 interposed between the layers 12 to 14 is exposed by a predetermined length. As shown in FIG. 2, the superconducting wire 15 is a tape-shaped bismuth-based superconductor 18 with a silver sheath 19, and the critical current (Ic) per wire is 50A. The end of this multi-layer superconducting conductor 10 is arranged to face the end of another multi-layer superconducting conductor 20 that is similarly stepped.
The outer layer 14, the intermediate layer 13, and the inner layer 12 of the multilayer superconducting conductor 10 are connected to the inner layer 22, the intermediate layer 23, and the outer layer 24 of the multilayer superconducting conductor 20, respectively. The above connection is made by welding an aluminum lead wire 40 to the connection ring 16. As the lead wire 40, copper, a superconducting wire, or the like can be used in addition to aluminum. The formers 11 and 21 of the cores of both multilayer superconducting conductors 10 and 20.
The two are connected to each other via a connection sleeve 52. An electric field is shielded by the aluminum sleeve 41 over the entire connecting portion.

FIG. 3 is a completed view of a connecting portion between the two multi-layer superconducting conductors 10 and 20. In the figure, reference numeral 42 denotes a reinforced insulator in which a paper tape is wound across the insulating materials 17 and 27 that cover the superconducting conductors 10 and 20.The reinforced insulator 42 is covered with a heat insulating cylinder 43 for vacuum heat insulation. Has been. The heat-insulating cylinder 43 is liquid-tightly connected to heat-insulating pipes (inner voids filled with heat-insulating material) 44, 45 arranged on the outer periphery of the insulation materials 17, 27. As described above, the multilayer superconducting cable 50 obtained by connecting the multilayer superconducting conductors 10 and 20 to each other is provided with the hollow portion of the outer circumference covered with the heat insulating tubular body 43 and the heat insulating tubes 44 and 45, and the formers 11 and 21. It is used by being cooled to a temperature equal to or lower than the critical temperature by flowing the refrigerant 51 inside and inside respectively.

(Embodiment 2) FIG. 4 is a side view of a connecting portion showing a second embodiment of the multilayer superconducting cable of the present invention. Three multi-layer superconducting conductors 10, 20, 30 are connected in the longitudinal direction. The outer layer 14 of the multilayer superconducting conductor 10 is connected to the intermediate layer 23 of the multilayer superconducting conductor 20 and the inner layer 32 of the multilayer superconducting conductor 30. The outer layer 24 of the multilayer superconducting conductor 20 is connected to the inner layer 12 of the multilayer superconducting conductor 10 and the intermediate layer 33 of the multilayer superconducting conductor 30. The outer layer 34 of the multilayer superconducting conductor 30 is
Inner layer 22 of multilayer superconducting conductor 20 and intermediate layer of multilayer superconducting conductor 10.
Connected to 13. Others are the same as those in the first embodiment.

(Conventional Example 1) Outer layer 14 of multilayer superconducting conductor 10,
The intermediate layer 13 and the inner layer 12 are respectively the outer layers of the multilayer superconducting conductor 20.
24, the intermediate layer 23, and the inner layer 22. Others are described in Example 1.
Is the same as

Each of the obtained multi-layered superconducting cables was cooled to a temperature below the critical temperature and an energization experiment was conducted on the connection part to examine the reduction rate of the AC critical current with respect to the DC critical current. The results are shown in Table 1.

[0014]

[Table 1]

As is clear from Table 1, N of the product of the present invention
In o.1, the impedance was made uniform between the outer layer and the inner layer because each outer layer was connected to the other inner layer, and the reduction rate was suppressed to 0.33. In No. 2, the reduction rate was close to zero because each outer layer was connected to the other middle layer and inner layer by using two connecting parts. On the other hand, in the conventional product, since the outer layers were connected to each other, the impedance was not made uniform and the reduction rate was as large as 0.62. In this example, since each layer was cut in stages and the lead wire was used for the connection, the connection work was facilitated. Further, since the insulating material between the respective layers was exposed at the connecting portion, the insulating between the respective layers was surely achieved even at the connecting portion, and good superconducting characteristics were obtained.

The multi-layer superconducting cable in which two or three multi-layer superconducting conductors using a bismuth-based high-temperature superconductor are connected has been described above. However, the present invention is not limited to other high-temperature superconductors or metal superconducting conductors. The same effect can be obtained by applying it to a superconducting conductor using a body, a multi-layer superconducting conductor other than three layers, or a case where four or more multi-layer superconducting conductors are connected. Further, although an example in which a plurality of multi-layer superconducting conductors are connected to form one superconducting cable has been described, the present invention is also applied to a method of laying each multi-layer superconducting conductor in advance on the site and connecting it on site. Of course you can.

[0017]

As described above, according to the multi-layer superconducting cable of the present invention, the impedance of each layer is made uniform, so that the AC critical current increases and the industrially remarkable effect is achieved.

[Brief description of drawings]

FIG. 1 is a side view of a connecting portion showing a first embodiment of a multilayer superconducting cable of the present invention.

2 is a cross-sectional explanatory view showing an example of a superconducting wire used in the multilayer superconducting cable shown in FIG.

FIG. 3 is a side view showing an embodiment of a cooling structure for the multilayer superconducting cable shown in FIG.

FIG. 4 is a side view of a connecting portion showing a second embodiment of the multilayer superconducting cable of the present invention.

[Explanation of symbols]

 10,20,30… Multilayer superconductor 11,21,31… Former 12,22,32… Inner layer of superconductor layer 13,23,33… Intermediate layer of superconductor layer 14,24,34… Outer layer of superconductor layer 15 ………… Tape-shaped superconducting wire 16 ………… Connecting ring 17,27 …… Insulating material 18 ………… Bismuth system superconductor 19 ………… Silver sheath 40 ………… Aluminum lead wire 41… ……… Aluminum sleeve 42 ………… Reinforced insulator 43 ………… Insulating cylinder 44,45 …… Insulation tube 50 ………… Multilayer superconducting cable 51 ………… Refrigerant 52 ………… Connection sleeve

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Kazuyoshi Inaoka 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Tsukushi Hara 4 Egasaki-cho, Tsurumi-ku, Yokohama-shi, Kanagawa No. 1 Tokyo Electric Power Co., Inc. Electric Power Research Laboratory (72) Inventor Hideo Ishii 4-1 Egasaki-cho, Tsurumi-ku, Yokohama-shi Kanagawa Electric Power Research Institute

Claims (3)

[Claims] 1. A multi-layer superconducting cable in which a plurality of multi-layer superconducting conductors in which a plurality of superconducting layers are concentrically compounded via an insulating material are connected, and one outer layer of the multi-layer superconducting conductors to be connected is different from a connection partner. A multi-layered superconducting cable characterized in that it is connected to the layers. 2. The multilayer superconducting cable according to claim 1, wherein the superconducting layer of the connecting portion of the multilayer superconducting cable is stepped with the insulating material exposed for a predetermined length. 3. The multilayer superconducting cable according to claim 1, wherein the connection is made through a lead wire, and the connecting portion is shielded by a metal sleeve.