JPH08167332A - Superconducting cable - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a compact superconducting cable for AC having a large-scale current capacity of practical scale and a small AC loss. [Structure] A superconducting cable is provided with an even number of superconductor layers twisted around a core material, and each of these superconductor layers includes the same number of superconductors, and the twisting directions of the superconductors are odd and even. It is characterized in that the superconductor layers are opposite to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a superconducting cable,
In particular, the present invention relates to improvement of an AC superconducting cable used in electric power application fields such as superconducting generators, superconducting transformers, and superconducting fault current limiters.

[0002]

2. Description of the Related Art Attempts to increase the capacity of superconducting cables for alternating current have been made, for example, on pages 103 to 112 of the Institute of Electrical Engineers of Japan Static Machine and Rotating Machinery Joint Research Group (Published December 3, 1992).
The Institute of Electrical Engineers of Japan Material Superconducting Applied Power Equipment Study Group 31
Pages 40 to 40 (published September 20, 1994).

FIG. 3 shows a cross-sectional structure of an example of a superconducting cable disclosed in the former document. Such a cable has an AC current (50/50 kA) under a magnetic field of 0.5 T. It has been reported that 60 Hz) can be passed.
The cable of FIG. 3 includes a primary twisted wire 3 in which six superconducting wires 2 are twisted around a primary core wire 1 of normal conductivity. Then, the seven primary twisted wires 3 are thicker than the normal conductive secondary core wire 4
A cable 5 of a secondary round stranded wire is formed by being twisted around the circumference of the. It is also possible to use a core material having a rectangular cross section as the secondary core wire 4, and a secondary flat-angle stranded wire in which, for example, 15 primary stranded wires 3 are twisted around such a secondary core material. Can also be formed.

[0004]

A conventional cable as shown in FIG. 3 uses a superconducting wire 2 having an alternating current of about 200 A or about several hundred A, but a practical scale of 1 kA. In order to obtain a cable having the above-mentioned energizing current, it has been unavoidable to design so as to include a large number of superconducting element wires 2 and primary stranded wires 3. The reason is that, compared with the alternating current that can flow when the superconducting element wire 2 is used alone, the alternating current that can be passed by one superconducting element wire that is twisted and included in the cable is, for example, about 50% or less. Because it will decrease. Then, as the number of superconducting element wires twisted and contained in the cable increases, the alternating current that can flow per superconducting element wire decreases, so that a compact superconducting cable having a large capacity of 1 kA or more is obtained. Is difficult.

The following reason can be considered as the cause of the decrease in the alternating current that can flow per superconducting element wire as the number of superconducting element wires twisted in the cable increases. One of the reasons for this is that due to the complicated twisted structure of the cable, the inductance between the superconducting wires becomes non-uniform and the balance is lost, so that a nonuniform flow occurs between the superconducting wires at the end of the cable. This is particularly noticeable when the surface of the superconducting wire is insulated, because current shunting between the wires becomes impossible. Another reason is that a radial current component of the superconducting wires twisted to form the cable is generated, and a magnetic field in the length direction of the cable is applied to the superconducting wires, which causes electrical instability. It is thought that it depends.

In order to solve the above-mentioned problems in the cable as shown in FIG. 3, Japanese Patent Publication No. 6-3
In 6329, a plurality of superconducting wires are spirally wound along the outer periphery of a normal-conducting core material in such a manner that right-handed layers and left-handed layers are alternately arranged. Proposed. A cable with such a structure can weaken the spontaneous magnetic field inside,
It is shown that the impedance of the cable can be reduced and the current capacity can be increased at the same time.

However, in the structure in which the twisting directions are simply opposite to each other between the layers of the adjacent superconducting wires, it is difficult in principle to completely balance the inductance between the superconducting wires. The longitudinal magnetic field cannot be completely canceled. That is, the magnetic field inside the cable cannot be completely reduced to 0, and there is a limit to the reduction of the impedance of the cable, so there is a certain limit to the improvement of the current capacity.

Therefore, in the present invention, in principle, the inductance of the superconducting element wire can be perfectly balanced, the internal magnetic field in the longitudinal direction can be completely canceled, and a large current capacity and / or a small alternating current can be obtained. An object is to provide an AC superconducting cable that may have a loss.

[0009]

A superconducting cable according to the present invention comprises an even number of superconductor layers twisted around a core material, each of the superconductor layers containing the same number of superconductors. The twisting direction is characterized by being opposite to each other between the odd-numbered and even-numbered superconductor layers.

It is more preferable that the twist pitches of the superconductors are equal between the odd-numbered and even-numbered superconductor layers.

Each of the superconductors may be a single superconducting element wire or a stranded wire including a plurality of superconducting element wires.

It is further preferable that each of the superconducting wires is incompletely insulated by an insulating film having a thickness of 5 μm or less.

The core material has a diameter of 2.0 mm or less 1
It may be a core wire of a book or a stranded wire of a plurality of core wires.

It is preferable that the core material has a resistivity of 1.0 × 10 ⁻⁷ Ωm or more. Paramagnetic CuM alloy, SUS31
At least one selected from a 6LK alloy, a Ti alloy, a fiber reinforced plastic, a glass fiber, and an organic fiber can be included, and the symbol M is Ni, Mn, Si, and V.
It means that at least one selected from is included.

The superconducting cable may be impregnated with a non-metallic material in order to limit the relative movement of the superconducting wire and the core wire.

The plurality of superconductor layers may be insulated from each other, and a fiber reinforced plastic tape containing an epoxy resin can be used as an interlayer insulating material.

[0017]

In the superconducting cable according to the present invention, the twisting directions of the superconductors are opposite between the odd-numbered and even-numbered superconducting layers, and these superconductor layers contain the same number of superconductors. It is possible to achieve a perfect balance of the inductance between the superconductors.

Further, if the twist pitches of the superconductors are equal between the odd-numbered and even-numbered superconductor layers, in principle, the internal magnetic field in the longitudinal direction of the cable due to the radial current component of the superconductor can be completely eliminated. It can be erased.

As each of the superconductors, a single superconducting element wire or a twisted wire of a plurality of superconducting element wires can be used. However, if the outer diameter of the superconducting element wire is 0.3 mm or less, Since a practical alternating current can be obtained and the twist pitch of the superconducting wires can be reduced, the AC loss of the superconducting cable can be reduced. As a superconducting element wire that can be used for such a large capacity superconducting cable,
Cu-30wt% Ni, Cu- Mn, can be used a plurality of composite multifilamentary wire filaments embedded such Nb-Ti and Nb ₃ Sn in the high-resistance alloys such as Cu-Sn. When the filament diameter in such a composite multifilamentary wire is 0.2 μm or less, a high alternating current density can be obtained in a low magnetic field of around 0.5 T, and the hysteresis loss generated in the filament can be reduced. it can.

If each of the superconducting element wires is incompletely insulated by an insulating film having a thickness of 5 μm or less, it is possible to reduce the occurrence of coupling loss between the superconducting element wires and to divide the current between the superconducting element wires. Therefore, it is possible to suppress a decrease in the AC energization current of the cable. As the insulating film, an organic insulating material such as PVF (hole circle), a metal material having a high resistivity such as metallic chromium, and an inorganic insulating material such as copper oxide can be used. It is desirable that neither of them exceeds 5 μm. If the thickness of the insulating film exceeds 5 μm, the insulation between the superconducting element wires will be perfect, and the cooling efficiency will deteriorate, resulting in deterioration of the superconducting characteristics and diversion between the superconducting element wires will become difficult. There is a high possibility that the AC energization current will decrease.

As the core material, a single core material wire or a twisted wire of a plurality of core material wires can be used. However, if the core wire has a diameter of 2.0 mm or less, the eddy current loss generated in the core material can be suppressed even if the core material is a conductive material. When a thick core material is required, a plurality of thin core material wires may be used. Since the outer diameter of a large-capacity cable increases and the diameter of the core material also increases, it is important to select an appropriate diameter for the core wire.

The core material is used to reduce eddy current loss.
1.0 x 10^-7It is preferable to have a resistivity of Ωm or more.
As such materials, paramagnetic CuM alloy, SU
S316L alloy, Ti alloy, fiber reinforced plastic,
Select at least one of glass fiber and organic fiber
Where the symbol M is Ni, Mn, Si, and
Represents including at least one selected from V.
By the way, 1.0 × 10 ^-7Material with resistivity of Ωm or more
Even if the material is a ferromagnetic material, the ferromagnetic hysteresis loss
It is not preferable as a core material because it causes

It is further preferred that the cable is impregnated with a non-metallic material in order to limit the relative movement of the superconducting wire and the core wire. The non-metallic material impregnated in the cable in this way can prevent the AC energizing current of the cable from decreasing by suppressing the relative movement between the wires, and also protect the environment in which the cable is used (superconductivity). It can also play the role of rust prevention for wires and protection against damage from mice).

A cable in which each of the superconducting wires is a non-insulated bare wire and in which the superconductor layers are insulated can be used for high-voltage industrial equipment, and an epoxy resin is used as the interlayer insulating material. A FRP (fiber reinforced plastic) tape containing the above can be preferably used. This FRP
As the material, glass fiber reinforced plastic (GFRP) or carbon fiber reinforced plastic (CFRP) can be used. In particular, if a prepreg tape containing an uncured epoxy resin is used as the interlayer insulating material, both the action of fixing the twisted superconducting element wire and the function of interlayer insulating can be obtained. In addition, after curing the prepreg tape applied on the first layer of the superconducting wires twisted around the core material, by performing the twisting of the superconducting wires of the second layer, It is easy to manufacture a standard superconducting cable. Further, in this structure, the wires can be shunted by making the wires in the layer contact with each other, so that the effect of increasing the alternating current is generated. Moreover, since the layers are insulated, the coupling loss between the wires (the coupling loss is small in the layers and large in the layers) can be reduced.

[0025]

1 is a schematic view showing the cross-sectional structure of a superconducting cable according to an embodiment of the present invention. In this superconducting cable, a single core material 1 having a relatively large diameter is used.
Twenty-one superconductors 12 are twisted around the circumference of 1 as a first superconductor layer. Around the first superconductor layer, 21 superconductors 12 are similarly twisted as a second superconductor layer. The twist directions of these two superconductor layers are opposite to each other. In FIG. 1, the arrow S represents the right-handed winding direction, and the arrow Z represents the left-handed winding direction. Since the second superconductor layer has a longer perimeter than the first superconductor layer, the second superconductor layer contains the same number of superconductors as the first superconductor layer, and 6 It includes a dummy line 13 of a book.

It goes without saying that the superconducting cable as shown in FIG. 1 can include not only two superconductor layers but also an even number of superconductor layers. Further, as the superconductor 12, not only a single superconducting element wire, but also a twisted wire including a plurality of superconducting element wires can be used.

[0027]

[Table 1]

In Table 1, the alternating current characteristics of the superconducting cable having the structure shown in FIG. 3 and the superconducting cable having the structure shown in FIG. 1 are shown in comparison. That is, the cable 1A has a conventional twist structure as shown in FIG. 3, and the cables 1B and 1C have a twist structure according to one embodiment of the present invention as shown in FIG. .

In each of the cables 1A to 1C,
A 0.2 mm diameter NbTi superconducting element wire is used as a single superconductor. This superconducting wire is Cu-30
0.12 μm embedded in a wt% Ni matrix
Contains a large number of NbTi filaments with a diameter of 1.0
It is twisted at a pitch of mm.

In the cable 1A, the primary twisted wire 3 is 5
The secondary twisted wire 5 is twisted at a pitch of 18 mm. On the other hand, in the cables 1B and 1C, the superconducting element wires 12 of the first layer and the second layer are all twisted at a pitch of 18 mm. The first layer is twisted in the S direction, and the second layer is twisted in the Z direction.

Cu-10 wt% Ni is used as the material of the core wires 1 and 4 in the cable 1A, and it has a resistivity of 1.2 × 10 ^-7 Ωm. The core wire 11 and the dummy wire 13 of the cable 1B have the same material as the core wire of the cable 1A. On the other hand, the core wire 1 of the cable 1C
1 and the dummy wire 13 are made of a Cu-2 wt% Ni material,
It has a resistivity of 7 × 10 ⁻⁷ Ωm.

The cables 1A to 1C were subjected to an AC energization test and an AC loss test at a frequency of 50 Hz in liquid helium under an external transverse magnetic field of 0.5T. Table 1
As can be seen, it is clear that the cables 1B and 1C having the structure of FIG. 1 according to the present invention have a larger alternating current and a smaller AC loss than the cable 1A having the structure of FIG. 3 according to the prior art.

Further, in comparison between the cables 1B and 1C having the same structure shown in FIG. 1, 1.0 × 10 ⁻⁷ Ω
It is clear that the cable 1B including the core wire having the non-resistance larger than m has better alternating current characteristics than the cable 1C including the core wire having the non-resistance of 1.0 × 10 ⁻⁷ Ωm. In particular, the cable 1B has a smaller AC loss than the cable 1C, and the AC loss value is 17k.
W / m ³ it can be seen that almost no increase from the AC loss 15kW / m ³ of the superconducting wire itself. That is, in the cable having the structure according to the present invention, the core material is 1 ×
It can be seen that it is more preferable to have a resistivity of 10 ⁻⁷ Ωm or more.

[0034]

[Table 2]

In Table 2, a structure similar to that of FIG. 3 is used.
Cable 2A having a structure and a structure similar to that of FIG.
The alternating current characteristics of the cable 2B that it has are shown for comparison.
ing. That is, the cables 2A and 2B are respectively shown in FIG.
And a structure similar to that of FIG.
And 3 Nb having a diameter of 0.15 mm ₃ 
The primary stranded wire in which Sn superconducting wire is stranded at a pitch of 3 mm
It is used. This superconducting element wire is Cu-10 wt%
A large number of 0.2 μm diameter embedded in Sn matrix
Nb₃ Includes Sn filament, 1.0mm
Twisted on the pitch.

The cable 2A has a secondary twist pitch of 10 mm and a tertiary twist pitch of 27 mm.
In B, both the first layer and the second layer of the superconductor layer have the same twist pitch of 27 mm as the tertiary twist pitch of the cable 2A. As the material of the core wire, the cables 2A and 2
In each case of B, Cu-30 wt% Ni having a resistivity of 3.7 × 10 ⁻⁷ Ωm is used.

With respect to the cables 2A and 2B, the AC current characteristics were measured in the same manner as in Table 1, and the results are shown in Table 2. As is clear from Table 2, the cable 2B having the structure of FIG. 1 is also used when the primary stranded wires including a plurality of superconducting element wires are used as the superconductors 2 and 12 in the structures of FIGS. 3 and 1. A cable 2 having the structure of FIG.
It can be seen that it has better AC current characteristics than A.

[0038]

[Table 3]

Table 3 shows the influence of the number of superconducting element wires in each superconducting layer, the twisting direction, and the twisting pitch on the AC current characteristics of the cable in the cable having the structure of FIG.

In Table 3, the cable 3A is the same as the cable 1B in Table 1. That is, the cable 3A
Each of the first and second superconductor layers therein includes 21 superconducting wires twisted at a pitch of 18 mm, and the twist directions are reversed between the layers. On the other hand,
The cable 3B is similar to the cable 3A, but has the same twist direction between the first and second superconducting layers. Therefore, in the cable 3B, the cable 3
The AC energization current is slightly inferior to A, and the AC loss is considerably increased.

The cable 3C is similar to the cable 3A, but the numbers of superconducting element wires contained in the first and second superconducting layers are different from each other. That is, the cable 3C
In FIG. 1, the six dummy wires 13 in FIG. 1 are replaced with superconducting element wires, and the number of superconducting element wires contained in the second superconducting layer is increased to 27. Therefore, although the cable 3C has almost the same alternating current as the cable 3A, the AC loss is significantly increased.

Cable 3D is similar to cable 3A, but with a slightly different twist pitch between the first and second superconductor layers. As a result, the alternating current passing through the cable 3D is significantly lower than that of the cable 3A. However, the AC loss of the cable 3D maintains a low value equivalent to that of the cable 3A.

As is apparent from Table 3, the superconducting cable having the structure as shown in FIG. 1 includes the same number of superconducting element wires in which the superconducting layers adjacent to each other are twisted at the same pitch, and It can be seen that it is most preferable that the twist directions between the layers are opposite to each other. When the twist pitches are slightly different between adjacent superconductor layers as in the cable 3D, the AC energization current is considerably reduced, but the AC loss can be maintained at a low value.
A cable that has the same number of strands and opposite twist directions, even if the twist pitch is slightly different between adjacent superconductor layers,
It may be useful in some applications.

[0044]

[Table 4]

Table 4 shows the effects of incomplete insulation of the superconducting element wire and the structure and material of the core material on the AC loss of the superconducting cable.

In Table 4, the cable 4A is similar to the cable 1B in Table 1, but only the core material is 5.4 ×.
Stainless steel SUS316LN with a resistivity of 10 ^-7
Has been changed to. This cable 4A is cable 1B
It has the same AC loss of 17 kW / m ³ .

The cable 4B is similar to the cable 4A, but a stranded wire including seven core material wires having a diameter of 0.4 mm is used as a core material. As a result, the cable 4B has a slightly smaller AC loss than the cable 4A. That is, it is understood that the eddy current loss can be suppressed and the AC loss of the cable can be reduced by using the twisted wire including the plurality of thin core material strands as the core material.

The cable 4C is similar to the cable 4B, but the material of the core material is changed to stainless steel SUS304. As a result, the AC loss is significantly increased in the cable 4C. The reason is stainless steel SUS3
This is because the ferromagnetic hysteresis due to 04 has occurred.

The cable 4D is similar to the cable 4B, but PV with each superconducting wire having a thickness of 5 μm.
It is incompletely insulated by the F insulating film. as a result,
Cable 4D has a further reduced AC loss compared to cable 4B. The reason is that incomplete insulation between the superconducting wires reduces the occurrence of coupling loss between the wires, and at the same time enables shunting of the current between the wires to suppress the reduction of the alternating current. Because you can.

The cable 4E is similar to the cable 4A, but the material of the core material is changed to GFRP having a resistivity higher than 10 ^-3 Ωm. As a result, the cable 4E
Has a smaller AC loss than the cable 4A. The reason is that GFRP, which is the core material of the cable 4E, has a very large resistivity, so that the eddy current loss in the core material is significantly suppressed.

Since any of the cables in Table 4 includes a core material wire having a diameter of 2.0 mm or less as the core material, a large increase in the AC loss of the cable due to the eddy current loss has been observed. Absent. However, if the cable 4A having a core wire diameter of 1.2 mm and the cable 4B having a core wire diameter of 0.4 mm are compared, there is a difference of 1 kW / m ³ in AC loss. From this fact, if the diameter of the core wire is 2 mm, the AC loss due to the eddy current loss is proportional to the fourth power of the diameter of the core wire.
It can be calculated that the difference in AC loss is 7.7 kW / m ³ .
Such an increase in AC loss becomes a problem even in a practical cable. Therefore, the diameter of the core wire included in the core material of the cable is preferably 2.0 mm or less.

[0052]

[Table 5]

Table 5 shows the influence of the impregnating material that suppresses the relative movement of the superconducting element wire and the core element element wire in the superconducting cable and the insulating film inserted between the adjacent superconducting layers on the AC current characteristics of the cable. Shows. In Table 5,
Coils having the same dimensions were formed using various superconducting cables. That is, in each of the coils A to E, only one layer of the superconducting cable is wound around the GFRP cylinder having an outer diameter of 100 mm and a length of 150 mm with a pitch of 5 mm and 12 turns. In such a coil, the maximum magnetic field applied to the cable at 1000 Apeak is 0.2T.

In the coil A, the superconducting cable 1B shown in Table 1 is used, and the coil A is fixed only by the tension of the cable.

On the other hand, in the coil B, the cable 1B is used similarly to the coil A, but in the coil B, the superconducting cable is impregnated with epoxy and the whole coil is fixed by being covered with a thick epoxy layer. As a result, in the coil B, the relative movement of the superconducting element wire and the core material element wire in the superconducting cable is suppressed, so that the energizing current is increased and the AC loss is decreased as compared with the coil A.

In coil C, a superconducting cable as shown in FIG. 2 is used. The cable of FIG. 2 is similar to that of FIG. 1, except that an interlayer insulating film 14 is provided between the core material 11, the first superconductor layer, and the second superconductor layer. Only different. That is, the cable 5 used for the coil C
In A, a 0.1 mm-thick prepreg tape obtained by impregnating an uncured epoxy resin into an FRP tape formed by knitting an FRP fiber is used as an interlayer insulating film. Coil 4C is 1 at 150 ° C after the cable 5A is wound.
The epoxy resin has been cured by heat treatment for 5 hours, and the cable is impregnated with an appropriate amount of the epoxy resin. As a result, in the coil C, the relative movements of the individual wires in the cable are suppressed and the superconductor layers are insulated, so that the AC loss is not much different from that of the coil B, but the energizing current is further increased. are doing.

In the coil D, a cable 5B is used. The cable 5B is similar to the cable 5A, but is different only in that the cable 5B uses a 0.1 mm thick FRP tape containing no epoxy resin as an interlayer insulating film. Further, in the coil D, like the coil A, it is fixed only by the tension of the cable. As a result, in the coil D, since the FRP tape as the interlayer insulating film does not contain the epoxy resin, the AC current characteristics are inferior to the coil C, but the AC loss is lower than that of the coil A not including the interlayer insulating film. Has been improved.

In the coil E, the cable 5B is used as in the case of the coil D. However, in the coil E, as in the case of the coil B, the cable 5B is impregnated with the epoxy resin, and the entire coil is fixed with the thick epoxy resin. As a result, the coil E has a conduction current exceeding 1400 Apeak as in the case of the coil B, and the AC loss is further reduced by the effect of the interlayer insulating film of the FRP tape.

From the results shown in Table 5, it is understood that it is preferable that the coil using the superconducting cable contains an inter-layer insulating film as well as an impregnating material which suppresses relative movement between the individual wires in the cable.

[0060]

As described above, according to the present invention, it is possible to provide a compact AC superconducting cable having a large-scale current capacity on a practical scale and a small AC loss.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a superconducting cable according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a superconducting cable according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a prior art superconducting cable.

[Explanation of symbols]

 11 core material 12 superconductor 13 dummy wire S right twist direction Z left twist direction

Claims (9)

[Claims] 1. A core material, and an even number of superconductor layers twisted around the core material, each of the superconductor layers including the same number of superconductors, and the twisting direction of the superconductor is an odd number. A superconducting cable in which the even-numbered superconducting layers are in opposite directions. 2. The superconducting cable according to claim 1, wherein the twist pitches of the superconductors are equal between the odd-numbered and even-numbered superconductor layers. 3. The superconducting cable according to claim 1, wherein each of the superconductors includes one or more equal numbers of superconducting wires having a diameter of 0.3 mm or less. 4. The superconducting cable according to claim 1, wherein each of the superconductors is incompletely insulated by an insulating film having a thickness of 5 μm or less. 5. The superconducting cable according to claim 1, wherein the core material includes one or more core material wires having a diameter of 2.0 mm or less. 6. The core material has a resistivity of 1.0 × 10 ⁻⁷ Ωm or more and is selected from paramagnetic CuM alloy, SUS316L alloy, Ti alloy, fiber reinforced plastic, glass fiber and organic fiber. The superconducting cable according to any one of claims 1 to 5, wherein the superconducting cable includes at least one, and M represents at least one selected from Ni, Mn, Si and V. 7. The cable is impregnated with a non-metallic material in order to limit relative movement of the superconducting element wire and the core material element wire. Superconducting cable described in section. 8. The superconducting cable according to claim 1, wherein the plurality of superconducting layers are insulated from each other. 9. The superconducting cable according to claim 8, wherein a plurality of the superconducting layers are insulated from each other by a fiber reinforced plastic tape containing an epoxy resin.