JP7072162B2 - Superconducting power transmission pipe - Google Patents

Description

The present invention relates to a power transmission tube that transmits an electric current using a superconducting wire.

In general, power cables using high-temperature superconductors, which are being researched and developed for power transmission of commercial power and electric wires for railways, have a certain margin in their performance from the viewpoint of ensuring safety in the event of an accident. It is necessary to secure it. Therefore, the structure of the power cable has to be complicated.

In addition, most of the high-temperature superconductors that are being considered for use in such power cables are bismuth-based superconductors (partly rare earth-based), and their shapes are tape-shaped. Therefore, the core of the power cable has a structure in which a tape-shaped superconductor is spirally wound around a core (for example, a copper wire).

On the other hand, in recent years, MgB ₂ (magnesium diboride), which is a high-temperature superconductor but is a cheaper and more common compound, is often used. For example, the European Nuclear Research Organization (CERN) has developed a superconducting power transmission tube using MgB ₂ for the purpose of reducing power consumption in an accelerator research facility. Although this superconducting power transmission tube is used with direct current, it has a complicated structure because it is used with a large current (see Non-Patent Document 1).

However, when the superconducting power transmission tube is used as a DC or low frequency AC power cable with a relatively low current, it is considered that the structure does not necessarily have to be complicated as in the conventional case. For example, in a superconducting power transmission tube applied to a transmission type magnet in an accelerator system as shown in Non-Patent Document 2, a return conductor is not required, and the refrigerant may also have a one-way flow path.

By the way, in a superconducting power transmission tube (power cable using a superconductor), it is necessary to cool the superconductor which is a current path to a temperature equal to or lower than the critical temperature of superconductivity. Therefore, the superconducting power transmission tube usually has at least a double tube structure in which the superconductor that becomes the current path and the inner tube containing the refrigerant that cools the superconductor is put in the outer tube of the vacuum. It becomes. For example, Patent Document 1 discloses an example of a superconducting cable having a double tube structure composed of an outer tube and an inner tube and having a three-core superconducting cable core in the inner tube. There is. In this superconducting cable core, a bismuth-based superconducting tape material is used.

Japanese Unexamined Patent Publication No. 2011-179543

A. Ballarino, 5 others, “Progress on MgB2 at CERN”, [online], April 9, 2014, CERN, [Searched April 10, 2017], Internet, <URL: http://www.slideshare .net / SR2S / progress-on-mgb2-at-cern ＞ Toru Ogitsu, 7 others, “Design Study of Superconducting Transmission Line Magnet for J-PARC MR Upgrade”, DOI (identifier) 10.1109 / TASC.2017.2656247, for publication in IEEE Transactions on Applied Superconductivity (January 20, 2017)

As mentioned above in the background technology, the superconducting power transmission tube, which is a conventional superconducting power cable, has a complicated structure, in other words, a structure with excessive specifications for application to a relatively small-scale system such as a consumer. It has become. As a result, the cost of superconducting power transmission tubes is relatively high in relatively small systems, especially in short-distance power transmission applications.

On the other hand, even in relatively small-scale applications, as long as the superconducting transmission tube is used as a power cable for passing direct current or low-frequency alternating current, the superconductor (superconducting wire) that becomes the current path is an external magnetic field or It receives an electromagnetic force that is not small according to its own current. Then, when the superconducting wire is deformed and distorted due to the electromagnetic force, the superconducting property of the superconducting wire may deteriorate. In particular, when MgB ₂ is used for a superconducting wire, MgB ₂ is more vulnerable to strain than other high-temperature superconductors, so the structure of the superconducting power transmission tube is such that the superconducting wire is not significantly distorted. Must be.

An object of the present invention is to provide a superconducting power transmission tube capable of using a high-temperature superconductor that is vulnerable to strain as a superconducting wire.

The superconducting power transmission pipe according to the present invention includes a superconducting wire, a sheath into which the superconducting wire is inserted, a cooling pipe into which the sheath is inserted and filled with a refrigerant for cooling the sheath, and the cooling. A superconducting power transmission tube comprising a tube inserted and a vacuum-exhausted outer tube, wherein the sheath is rigidly attached to the cooling tube by a first support member provided in the cooling tube. The cooling pipe is rigidly supported by the outer pipe by a second support member provided in the outer pipe , electrically connected to the sheath, and electrically insulated from the outer pipe. It is characterized by being done.

INDUSTRIAL APPLICABILITY According to the present invention, a superconducting power transmission tube capable of using a high-temperature superconductor that is vulnerable to strain as a superconducting wire is provided.

The figure which showed the example of the sectional view seen from the cut plane perpendicular to the central axis direction of the superconducting power transmission tube which concerns on 1st Embodiment. The figure which showed the example of the sectional view in the cut surface including the central axis of the superconducting power transmission tube which concerns on 1st Embodiment. The figure which showed the example of the structure of the conductor unit of the superconducting power transmission tube which concerns on the modification of 1st Embodiment. The figure which showed the example of the sectional view seen from the cut plane perpendicular to the central axis direction of the superconducting power transmission tube which concerns on 2nd Embodiment. The figure which showed the example of the sectional view seen from the cut plane perpendicular to the central axis direction of the superconducting power transmission tube which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, common components are designated by the same reference numerals, and duplicate description will be omitted.

(First Embodiment)
FIG. 1 is a diagram showing an example of a cross-sectional view seen from a cut surface perpendicular to the central axis direction of the superconducting power transmission pipe 100 according to the first embodiment of the present invention. Further, FIG. 2 is a diagram showing an example of a cross-sectional view of a cut surface including the central axis of the superconducting power transmission pipe 100 according to the first embodiment of the present invention.

As shown in FIGS. 1 and 2, the superconducting power transmission tube 100 is filled with a superconducting wire 1 made of a superconductor, a sheath 2 into which the superconducting wire 1 is inserted, and a refrigerant for cooling the sheath 2. The cooling pipe 5 is provided with an outer pipe 8 for holding the cooling pipe 5 in the vacuum-exhausted space. Then, the sheath 2 is fixed to the inner wall of the cooling pipe 5 via the fixing member 4, and the cooling pipe 5 is fixed to the inner wall of the outer pipe 8 via the load supporting member 7. That is, the sheath 2 is rigidly supported by the cooling pipe 5, and the cooling pipe 5 is rigidly supported by the outer pipe 8.

Here, the space outside the sheath 2 and inside the cooling pipe 5 becomes the flow path 9 for the refrigerant. In the present embodiment, the direction of the flow of the refrigerant is only one direction, and in FIG. 2, the direction is indicated by an arrow. Further, the space outside the cooling pipe 5 and inside the outer pipe 8 is a vacuum space 10 that has been evacuated and is used as a vacuum heat insulating space. That is, the vacuum space 10 is a space provided for suppressing the heat of the outer pipe 8 from being conducted to the cooling pipe 5.

Further, as shown in FIGS. 1 and 2, the fixing member 4 for fixing the sheath 2 to the cooling pipe 5 and the load supporting member 7 for fixing the cooling pipe 5 to the outer pipe 8 are both composed of a donut-shaped disk. Has been done. A plurality of large openings (corresponding to the refrigerant flow path 9 and the vacuum space 10 in FIG. 1) are provided on the disk surface. Here, the opening provided in the fixing member 4 is provided to secure the flow path 9 of the refrigerant, and the opening provided in the load supporting member 7 is for vacuum exhaust. It is provided to reduce the heat conduction path connecting the outer pipe 8 and the cooling pipe 5.

Further, as shown in FIG. 2, the fixing member 4 and the load supporting member 7 are arranged at predetermined intervals (for example, 200 mm) along the central axis of the superconducting power transmission pipe 100, and the cooling pipe 5 and the outer pipe are arranged, respectively. It is fixed at 8. Further, a super insulator 6 for suppressing the intrusion of radiant heat from the outer pipe 8 to the cooling pipe 5 is provided on the outside of the cooling pipe 5 where the load supporting member 7 is not provided. The super insulator 6 is a multi-layer heat insulating material, and is composed of, for example, an aluminum vapor-deposited film and a spacer laminated.

Since the load support member 7 is a member for rigidly supporting the low temperature cooling pipe 5 with the outer tube 8 at room temperature, it has high rigidity such as FRP (Fiber Reinforced Plastics). It is composed of a material with low thermal conductivity. However, depending on the specifications of the superconducting power transmission pipe 100 and its usage conditions, the load support member 7 may be made of ordinary plastic other than FRP.

In the present embodiment, the material of the superconducting wire 1 is MgB ₂ , but the material is not limited to this, and other superconductors may be used. When the material of the superconducting wire 1 is MgB ₂ , for example, 20K helium gas can be used as the refrigerant to be passed through the cooling pipe 5.

Further, in the present embodiment, the superconducting wire 1 and the sheath 2 into which the superconducting wire 1 is inserted are collectively referred to as a conductor unit 3. Then, the sheath 2 is made of a metal of a good conductor such as copper. In that case, the sheath 2 can be used as a spare current path when the superconducting wire 1 undergoes a normal conduction transition. This will be described separately later.

Further, in the case of manufacturing a conductor unit 3 composed of a superconducting wire 1 and a sheath 2 made of MgB ₂ , as a manufacturing procedure thereof, the superconducting wire 1 before heat treatment is passed through the sheath 2 and the sheath 2 is manufactured. A manufacturing method of heat-treating each can be adopted. In this case, since the strain tolerance of the superconducting wire 1 made of MgB ₂ is larger before the heat treatment than after the heat treatment, there is an advantage that the workability at the time of manufacturing the conductor unit 3 can be improved.

As a result, it becomes easy to insert the superconducting wire 1 into the bent sheath 2, or to insert the superconducting wire 1 into the sheath 2 and then bend the sheath 2. This also makes it possible to manufacture a curved conductor unit 3, that is, a curved superconducting power transmission tube 100.

As described above, the method for manufacturing the conductor unit 3 in which the superconducting wire 1 is passed through the sheath 2 and then heat-treated is not limited to the case where the material of the superconducting wire 1 is MgB ₂ , and heat treatment is required. It is also applicable to the superconducting materials of.

By the way, the superconducting wire 1 may be a single wire having a large diameter, a bundle of linear thin wires, or the like, but it is preferably a stranded wire obtained by twisting a plurality of fine wires. When the superconducting wire 1 is composed of stranded wires made of a plurality of fine wires, the plurality of fine wires are twisted and integrated, so that the insertability into the sheath 2 is improved. In addition, it is possible to reduce changes in the external magnetic field and coupling loss (eddy current loss, etc.) during alternating current energization.

Further, the superconducting wire 1 may be simply inserted into the sheath 2, but it is more preferable that the voids in the sheath 2 into which the superconducting wire 1 is inserted are filled with resin or metal. The dimensions of the superconducting wire 1 and the dimensions of the sheath 2 are appropriately determined according to the current flowing through the superconducting power transmission tube 100, but if the superconducting wire 1 is simply inserted into the sheath 2, the superconducting wire 1 will be sheathed. There may be a case where the structure has a spatial margin within 2. In that case, when an electromagnetic force is applied to the superconducting wire 1 by an external magnetic field or the like, the superconducting wire 1 may be distorted or bent in the sheath 2 and its superconducting characteristics may be deteriorated. Therefore, by filling the voids in the sheath 2 into which the superconducting wire 1 is inserted with resin, solder, or the like and physically integrating the superconducting wire 1 and the sheath 2, superconductivity caused by electromagnetic force or the like is achieved. It is possible to prevent distortion and deformation of the line 1.

Further, in the present embodiment, according to the specifications of the superconducting power transmission pipe 100, the conductor unit 3 and the cooling pipe 5 may be electrically insulated or electrically connected. May be good. When electrically insulating between the conductor unit 3 and the cooling pipe 5, an insulating material such as GFRP (Glass Fiber Reinforced Plastic) or resin is used as the material of the fixing member 4.

However, when the potential difference between the conductor unit 3 and the ground is large, or when helium gas is used as the refrigerant, insulation is ensured between the conductor unit 3 and the cooling pipe 5 depending on the dimensions. Can be difficult. In that case, the conductor unit 3 and the cooling pipe 5 are electrically connected via a metal fixing member 4 such as stainless steel, and insulation is provided between the cooling pipe 5 and the outer pipe 8. good.

As described above, the vacuum space 10 between the cooling pipe 5 and the outer pipe 8 is a space for heat insulation. Therefore, for the load supporting member 7 connecting the cooling pipe 5 and the outer pipe 8, an insulating material such as FRP having a low thermal conductivity is used in order to ensure heat insulating properties. Therefore, it can be said that it is rational to provide insulation between the cooling pipe 5 and the outer pipe 8.

As described above, the superconducting power transmission pipe 100 according to the present embodiment includes only the superconducting wire 1 which is a unidirectional current path, and also includes only the cooling pipe 5 which is a unidirectional refrigerant flow path. .. That is, in the present embodiment, the structure of the superconducting power transmission pipe 100 is simplified, and as a result, the manufacturing cost of the superconducting power transmission pipe 100 can be reduced.

Further, in the superconducting power transmission pipe 100 according to the present embodiment, the conductor unit 3 (sheath 2) is rigidly supported by the cooling pipe 5, and the cooling pipe 5 is rigidly supported by the outer pipe 8. It is possible to prevent the conduction wire 1 from being distorted (deformed) by receiving an electromagnetic force or the like. Therefore, even when a high-temperature superconductor such as MgB ₂ which is vulnerable to strain is used as the material of the superconducting wire 1, deterioration of the superconducting characteristics of the superconducting wire 1 can be suppressed.

(Variation example of the first embodiment)
FIG. 3 is a diagram showing an example of the configuration of the conductor unit 3a of the superconducting power transmission tube 100 according to the modified example of the first embodiment, and FIG. 3A is a diagram showing a first configuration including a central axis of the conductor unit 3a. The cross-sectional view on the cut surface, (b) is a cross-sectional view on the second cut surface including the central axis of the conductor unit 3a and perpendicular to the first cut surface.

Generally, when the superconducting wire 1 is used as a power transmission line, accident countermeasures for the normal conduction transition of the superconducting wire 1 are taken. That is, when the superconducting wire 1 undergoes a normal conduction transition, an excessive Joule heat generation is generated by a large current flowing through the superconducting wire 1, and the superconducting wire 1 is burnt. Therefore, voltage terminals are provided at appropriate multiple points of the superconducting wire 1 to cut off the power supply by detecting an abnormality in the voltage between the plurality of points to prevent the superconducting wire 1 from burning. ..

However, due to problems such as the current capacity of the superconducting wire 1 in the superconducting state and the time delay from the detection of voltage abnormality to the current cutoff, the large current flowing through the superconducting wire 1 is not properly cut off and is momentarily excessive. Joule heat generation may occur, making it difficult to protect the superconducting wire 1. In preparation for such a case, a current detour that bypasses the current flowing through the superconducting wire 1 is often provided.

In the first embodiment described above, the void between the superconducting wire 1 and the sheath 2 is filled with a conductor substance such as solder, and the superconducting wire 1 and the sheath 2 are electrically connected everywhere. In this case, the superconducting wire 1 and the sheath 2 have the same potential everywhere. In such a case, even if a normal conduction transition occurs in the superconducting wire 1, the current flowing through the superconducting wire 1 immediately detours to the sheath 2 made of a good conductor such as copper. .. Therefore, it is possible to prevent an accident in which the superconducting wire 1 is burnt out.

However, when the gap between the superconducting wire 1 and the sheath 2 is filled with an insulating substance or nothing is filled, the superconducting wire 1 and the sheath 2 are not necessarily electrically connected. Is not always. In such a case, when the normal conduction transition occurs in the superconducting wire 1, there is no detour of the current flowing through the superconducting wire 1, so that the superconducting wire 1 may be burnt out.

Therefore, in this modification, the conductor unit 3a is composed of the superconducting wire 1, the sheath 2, and the copper plates 11 provided at both ends thereof, and the superconducting wire 1 and the sheath 2 are both formed on the copper plate 11. It was assumed that it was electrically connected. Further, it is assumed that the sheath 2 is made of a metal of a good conductor such as copper, aluminum, a copper alloy, and an aluminum alloy.

Although the detailed structure of the superconducting wire 1 in the sheath 2 is omitted in FIG. 3, here, the superconducting wire 1 is a stranded wire obtained by twisting a plurality of thin wires 1a of a superconductor. It is supposed to be. Then, it is assumed that the plurality of thin wires 1a are soldered to the copper plate 11. Further, in this case, the gap between the sheath 2 and the superconducting wire 1 may be filled with a conductive metal such as solder or an insulating resin, and further, nothing may be filled. ..

In the superconducting power transmission tube 100 having the conductor unit 3a having the above configuration, the normal conduction transition of the superconducting wire 1 is detected as a voltage abnormality between two copper plates 11 provided at both ends of the conductor unit 3a. .. When the voltage abnormality is detected, the current flowing through the superconducting wire 1 is cut off, but a part or most of the current flowing through the superconducting wire 1 is sheathed during the time delay until the cutoff. It will detour to 2 and flow. Therefore, since it is possible to prevent a large current from flowing through the superconducting wire 1, it is possible to prevent the superconducting wire 1 from burning.

(Second embodiment)
FIG. 4 is a diagram showing an example of a cross-sectional view seen from a cut surface perpendicular to the central axis direction of the superconducting power transmission pipe 100a according to the second embodiment of the present invention. As shown in FIG. 4, the structure of the superconducting power transmission pipe 100a according to the second embodiment is a tubular shield plate 12 in a vacuum space 10 between the cooling pipe 5 and the outer pipe 8 so as to separate the two. Is provided, which is different from the superconducting power transmission pipe 100 according to the first embodiment. Further, in the superconducting power transmission pipe 100 according to the first embodiment, the super insulator 6 is provided at a position in contact with the outside of the cooling pipe 5, but in the superconducting power transmission pipe 100a according to the second embodiment, the shield is provided. It is also different in that it is provided at a position in contact with the outside of the plate 12.

The shield plate 12 functions as a so-called thermal anchor, and is provided to block radiant heat from the outer pipe 8 to the cooling pipe 5. When the temperature of the refrigerant flowing in the cooling pipe 5 is, for example, 10K, the temperature outside the outer pipe 8 is about 300K (normal temperature), so that the temperature difference between the two is large. In such a case, by providing a thermal anchor (shield plate 12) at a position between the two, the amount of radiant heat invading the cooling pipe 5 can be effectively reduced. Further, in this case, the effect of blocking radiant heat is greater when the super insulator 6 is arranged outside than when it is arranged inside the shield plate 12.

Other than that, the effect of the second embodiment is the same as the effect of the first embodiment.

(Third embodiment)
FIG. 5 is a diagram showing an example of a cross-sectional view seen from a cut surface perpendicular to the central axis direction of the superconducting power transmission pipe 100b according to the third embodiment of the present invention. As shown in FIG. 5, the structure of the superconducting power transmission pipe 100b according to the third embodiment is the first embodiment in that two (plurality) conductor units 3 are inserted in the cooling pipe 5. It is different from the superconducting power transmission pipe 100 according to the form.

The two conductor units 3 inserted in the cooling pipe 5 may be in contact with each other, and the superconducting wires 1 of both may be electrically connected to each other. Alternatively, the two conductor units 3 may be separated from each other, and the superconducting wires 1 of both may be electrically insulated from each other. When the two conductor units 3 are insulated from each other, the two superconducting wires 1 can be used as two current paths having different current directions and the like.

Other than that, the effect of the second embodiment is the same as the effect of the first embodiment.

The present invention is not limited to the embodiments and modifications described above, and further includes various modifications. For example, the above-described embodiments and modifications have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of a certain embodiment or modification with the configuration of another embodiment or modification, and the configuration of a certain embodiment or modification can be replaced with another embodiment or modification. It is also possible to add the configuration of. Further, it is also possible to add / delete / replace the configuration included in other embodiments or modifications with respect to a part of the configurations of each embodiment or modification.

1 Superconducting wire 1a Fine wire 2 Sheath 3,3a Conductor unit 4 Fixing member (first support member)
5 Cooling pipe 6 Super insulator 7 Load-bearing member (second support member)
8 Outer pipe 9 Refrigerant flow path 10 Vacuum space 11 Copper plate 12 Shield plate 100, 100a, 100b Superconducting power transmission pipe

Claims (6)

The superconducting wire, the sheath into which the superconducting wire is inserted, and the sheath into which the sheath is inserted are inserted, and
A superconducting power transmission pipe comprising a cooling pipe filled with a refrigerant for cooling the sheath and an outer pipe into which the cooling pipe is inserted and evacuated.
The sheath is rigidly supported by the cooling pipe by a first support member provided in the cooling pipe.
The cooling pipe is rigidly supported by the outer pipe by a second support member provided in the outer pipe , electrically connected to the sheath, and electrically insulated from the outer pipe . A superconducting power transmission tube featuring. The superconducting power transmission tube according to claim 1, wherein the superconducting wire inserted into the sheath is a stranded wire obtained by twisting thin wires made of a superconductor. The superconducting power transmission tube according to claim 1, wherein the void in the sheath into which the superconducting wire is inserted is filled with a resin or a metal. The superconducting power transmission tube according to claim 1, wherein the superconducting wire is composed of MgB ₂ . The sheath is made of any metal of copper, aluminum, a copper alloy and an aluminum alloy, and both ends of the sheath are electrically connected to both ends of the superconducting wire. The superconducting power transmission tube according to claim 1. A claim characterized in that a shield plate for blocking radiant heat is provided at a position between the outside of the cooling pipe and the inside of the outer pipe, and a super insulator is further provided on the outside of the shield plate. Item 1. The superconducting power transmission pipe according to Item 1.

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