JP4330008B2 - Superconducting cable pooling eye and laying method of superconducting cable using pooling eye - Google Patents

Description

The present invention relates to a pooling eye that is attached to a front end portion of a cable when a superconducting cable is drawn into an existing pipeline or a sinus and installed.

  Superconducting cables that transmit large amounts of power with low loss are currently in the development stage, and although production of 500m-class long cables for actual lines is being realized, there has not been a track record in laying cables.

Conventionally, the CV cable is laid by connecting a pooling eye to the end of the cable in order to draw the cable into the pipe without damaging the cable. FIG. 3 shows a connection structure between a CV cable and a conventional pooling eye. In the pooling eye 30 composed of the tension cap 31, the sleeve 32, and the protective tube 33, the copper conductor 21 is exposed from the electrical insulator 22 at the end of the CV cable 20 housed in the metal sheath 23 and inserted into the sleeve 32. Joined by external pressure. When the cable is required to be waterproof, the waterproof processing part 24 is provided and the end of the protective tube 33 and the end of the metal sheath 23 are joined by soldering or welding. According to the connection structure shown in FIG. 3, when laying, the tension generated in the CV cable 20 by pulling the pooling eye 30 is concentrated on the copper conductor 21 of the cable, or when the waterproof treatment part 24 is provided. It is shared by the copper conductor 21 and the metal sheath 23.

As shown in FIG. 1, the 500 m-class superconducting cable currently manufactured includes a former 2, a tape-like superconducting conductor 3 wound around the former 2, an electrically insulating layer 4 attached on the outer side, A cable core made of a protective layer 5 and two flexible coaxial tubes for housing the cable core are used as an inner tube 6 and an outer tube 8 of a heat insulating tube, and a heat insulating material is provided between the inner tube 6 and the outer tube 8. 7 is arranged. When the pooling eye 30 for the CV cable is applied to the superconducting cable 1, the former 2 exposed from the superconducting conductor 3 or the like of the superconducting cable is inserted into the sleeve 32 and joined instead of the copper conductor 21 of the CV cable. Instead of the metal sheath 23 of the CV cable, the heat insulation tube outer tube 8 and the protection tube 33 of the superconducting cable are joined, and the tension for pulling the pooling eye 30 is laid by the former 2 and the heat insulation tube outer tube 8 when laying. Will be. This tension is due to the frictional resistance generated by the friction between the cable and the pipe, and its magnitude is 170 kN in the 500 m class laying currently generally performed. In consideration of the force distribution between the former 2 and the heat insulating outer tube 8, the former 2 and the heat insulating outer tube 8 share the forces of 130 kN and 40 kN, respectively. However, the superconducting cable to which the above-described pooling eye for CV cable is applied has the following problems.

First, a superconductor is a ceramic superconductor placed on a metal (for example, copper), processed into a tape shape, and then wound around a former. It is mechanically weak and has excessive tension and lateral pressure. If applied, the current (critical current) that can flow while maintaining the superconducting state is reduced irreversibly. Actually, according to the investigation results of the inventors, when the tension was applied from 0 kN to the former of the superconducting cable, the critical current did not decrease until the tension reached 110 kN, and gradually decreased from 110 kN. Has deteriorated to half of the state where no tension is applied. Therefore, the above-described superconducting cable has a problem of performance deterioration. In order to avoid this, it is necessary to lay the cable at a short distance and connect the cable with a joint. However, the problem is that the construction period is prolonged and the construction cost increases. On the other hand, the terminal structure is designed to disperse the tension generated when laying the optical fiber cable, attach a cylindrical corrugate to the sleeve that is fixed to the tension member of the cable core, and further has a cylindrical cover on the pooling eye that is fixed to the outer sheath of the cable. Is disclosed in Patent Document 1 below. However, the tension at the time of laying the optical fiber cable is smaller than that of the power cable, and the terminal structure of the optical fiber cable cannot withstand the tension of the power cable.

Next, while the pooling eye is attached to the superconducting cable, airtightness is required in each of the inner space of the inner pipe of the heat insulating pipe and the space surrounded by the inner pipe and the outer pipe. It is necessary to replace the inside of the inner tube with dry air in order to prevent moisture absorption of the electrical insulation layer housed in the inner tube, and the heat insulating material disposed between the inner tube and the outer tube. This is because a high degree of vacuum is required in the space surrounded by the inner tube and the outer tube. However, when the conventional pooling eye for a CV cable is applied to a superconducting cable, the inner tube and the outer tube are not isolated from each other in the heat insulating tube, which causes an air tightness problem inside the heat insulating tube. As a solution to this problem, a terminal structure with a pooling eye for carrying and laying a cable while keeping high vacuum in a heat insulating layer surrounded by an outer tube and an inner tube together with liquid nitrogen enclosed in the inner tube of the heat insulating tube, that is, In the heat insulating pipe, a terminal structure having an inner tube and an outer tube which are mutually airtight is disclosed in Patent Document 2 below. However, this terminal structure is a stepped structure, in which a sealing metal fitting is attached to each of the inner tube and the outer tube, and the inner tube, the outer tube, and the cable core are integrated, so that the inner tube and the outer tube are integrated in the superconducting cable terminal. Although they are isolated from each other and are airtight, they do not have a tension distribution function when a tensile load is applied to the cable. Therefore, excessive tension may be applied to the superconducting conductor during laying to reduce the critical current.

Japanese Utility Model Publication No. 6-77437 Japanese Patent Laid-Open No. 9-15311

The present invention has been made in view of the above problems, and does not apply excessive tension or lateral pressure to the superconducting conductor so as to maintain the superconducting state and not to irreversibly decrease the critical current, and further, heat insulation of the superconducting cable. An object of the present invention is to provide a pooling eye for a superconducting cable that does not impair the performance of the material and the insulating material.

In order to achieve the above object, according to the present invention, as a first invention, in a pooling eye connected to an end portion of a superconducting cable, a sleeve that joins a former exposed from a conductor of the superconducting cable at a central portion of the pooling eye is provided. A portion to be joined to the outer tube of the superconducting cable at the outer end of the sleeve, and a portion to be joined to the outer tube of the superconducting cable at the end of the protective tube disposed on the outer periphery of the pooling eye. The inner pipe of the heat insulation pipe and the sleeve of the pooling eye are welded via a circular straight pipe, and the circular straight pipe is thicker than the thickness of the pipe of the heat insulation pipe and smaller than the thickness of the sleeve, and The insulation pipe outer pipe and the pooling eye protection pipe are welded via a circular straight pipe, and the thickness of the circular straight pipe is intermediate between the thickness of the heat insulation outer pipe and the thickness of the protection pipe. wherein the Rukoto using To provide a pulling eye for superconducting cable to be.

The pooling eye isolates the inner tube and the outer tube of the heat insulating tube at the end of the superconducting cable, and has airtightness in each of the space inside the inner tube and the space surrounded by the inner tube and the outer tube.

Also provided is a superconducting cable laying method characterized in that the pooling eye according to the first invention is used as a pooling eye for a superconducting cable.

According to the first invention, in connection between the end of the superconducting cable and the pooling eye, the sleeve provided at the center of the pooling eye and the former exposed from the conductor of the superconducting cable are joined, and the outer end of the sleeve When the cable is laid, by joining the heat-insulating pipe inner pipe of the superconducting cable and the end of the protective pipe arranged on the outer periphery of the pooling eye and the heat-insulating pipe outer pipe of the superconducting cable. The tension that pulls the eye is shared by the former of the superconducting cable and the inner and outer tubes of the heat insulating tube, and is not concentrated on the cable core, so that the critical current is not irreversibly lowered.

Furthermore, is performed by bonding the welding between the pulling eye and the heat insulating tube, the junction between the sleeve of the inner pipe and pulling eye of the heat-insulated pipe is performed through a circular straight pipe, thick circular type straight pipe of insulation with smaller than the thickness of the larger sleeve than the thickness of the tube in a tube, one or, also joining of the protective tube of the heat insulating tube outer pipe and pulling eye carried out through the same way circular straight pipe, circular type A straight pipe having a thickness intermediate between the thickness of the heat insulating outer pipe and the thickness of the protective pipe is used. This eliminates the difficulty of welding due to the difference in heat capacity, eliminates welding defects, cracks, pinholes, etc. in the welded portion, and further ensures the airtightness inside the heat insulating tube.

In addition, by connecting the pooling eye according to the present invention to the superconducting cable, the inner tube and the outer tube are isolated from each other at the end of the cable, and the inner space of the inner tube and the space surrounded by the inner tube and the outer tube are hermetically sealed. Because of this, there is no leakage between the inner tube and the outer tube, the electrical insulation layer of the cable core housed in the inner tube has excellent insulation performance without absorbing moisture from the outside air, and it is surrounded by the inner tube and the outer tube High vacuum can be maintained in the space to be insulated, and the heat insulation performance is not impaired.

The best mode for carrying out the present invention will be described below.

  FIG. 1 shows a schematic structure of a superconducting cable. The cable core at the center of the superconducting cable 1 is formed by winding a tape-shaped superconducting conductor 3 around a metal (for example, copper) former 2 in a spiral shape, and an electric insulating layer 4 (material is paper or semi-synthetic paper) ), And then formed from a protective layer 5 (eg made of conductive paper or copper braided wire). The cable core is a flexible metal (for example, stainless steel or aluminum) double heat insulation pipe, and is formed between the inner pipe 6 and the outer pipe 8 and between the inner pipe 6 and the outer pipe 8 of the double heat insulation pipe. It is accommodated in the heat insulation pipe | tube which consists of the heat insulating material 7 arrange | positioned. The inside of the heat insulation pipe inner pipe 6 is filled with dry air while the pooling eye is attached, and after the installation is finished, the pooling eye is removed and the terminal portion is attached. Then, liquid nitrogen flows and circulates along the cable core. The cable core is cooled to a liquid nitrogen temperature of 77K. Between the inner tube 6 and the outer tube 8, a heat insulating material called super-insulation is formed by laminating a polymer film of aluminum vapor deposition and a polyethylene net, and a high vacuum of 0.1 MPa or less. The exhaust is maintained at a reduced temperature to reduce heat penetration from room temperature.

FIG. 2 shows a connection structure between a pooling eye and a superconducting cable according to the present invention. The pooling eye 10 (the material is, for example, iron (SS40 or the like)) includes a pulling cap 11, a sleeve 12, and a protective tube 13. When this pooling eye 10 is used to attach to the superconducting cable 1, the cable end processing is performed as the first step. That is, the protective layer 5, then the electrical insulating layer 4, and the superconducting conductor 3 are removed to expose the former 2. The exposed portion of the former is inserted into the metal tubular sleeve 12 at the center of the pooling eye 10 and then compressed and joined by applying pressure from the outside. In addition to compression bonding, methods such as solder bonding and welding bonding may be used. As the next step, the end of the sleeve 12 on the cable side and the heat insulating pipe inner pipe 6 are welded through the circular straight pipe 14 at the welding locations 14a and 14b. In order to eliminate the difficulty of welding due to the difference in heat capacity, when welding the thin heat insulating pipe inner pipe 6 which is usually less than 1 mm and the pooling eye sleeve 12 having a thickness of about 5 mm to 15 mm, The one with a thickness of 2 mm is used. As the next step, the heat insulation pipe outer tube 8 and the cable side end of the protection tube 13 of the pooling eye are welded at the welded portions 15a and 15b via the circular straight tube 15 having a thickness of 2 mm for the same reason as described above. Weld. In this embodiment, the thickness of the heat insulating tube inner tube 6 is 0.6 mm, the thickness of the heat insulating tube outer tube 8 is 0.8 mm, and the thickness of the protective tube 13 is 5 mm. At this time, when the anticorrosion layer 17 using vinyl or polyethylene is provided on the outer tube 8, it is necessary to remove the anticorrosion layer 17 in advance to expose the surface of the outer tube 8. Finally, the protective tube 13 and the sleeve 12 are welded at the welding location 16a, and the superconducting cable 1 and the pooling eye 10 are integrated.

Although not shown in FIG. 2, the sleeve 12 and the pulling cap 11 are processed into a screw shape and fitted together.

Using the pooling eye of Example 1, it was attached to a 500 m superconducting cable, which is a general pipe laying length. When this was energized after drawing it into the pipeline, it was confirmed that there was no decrease in the critical current. In addition, after the pooling eye is attached, in order to check the airtightness, a pressure of 1 MPa is applied to the inner tube 6, then the inner pressure of the inner tube 6 is changed to atmospheric pressure, and a pressure of 1 MPa is applied between the outer tube 8 and the inner tube 6. When each was held for 24 hours, it was confirmed that there was no decrease in pressure and no evidence of leakage from the outer tube 8 into the inner tube 6. Thereby, the airtightness of the superconducting cable to which the pooling eye according to the present invention was attached was confirmed.

Superconducting cable perspective view showing superconducting cable structure The cross-sectional view which shows the connection structure of the pooling eye and superconducting cable concerning this invention Cross-sectional view showing connection structure between conventional pooling eye and CV cable

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Superconducting cable 2 Superconducting cable 1 former 3 Superconducting cable 1 superconducting conductor 4 Superconducting cable 1 electrical insulation layer 5 Superconducting cable 1 protective layer 6 Inner tube of superconducting cable 1 insulation tube 7 Insulating material 8 for superconducting cable 1 The outer tube 10 of the heat insulation tube of the superconducting cable 1 The pooling eye 11 according to the present invention The pulling cap 12 of the pooling eye 10 The sleeve 13 of the pooling eye 10 The protective tube 14 of the pooling eye 10 The circular straight tube connecting the sleeve 12 and the heat insulation tube 6 14a Welded portion 14b of the heat insulating tube inner tube 6 and the circular straight tube 14 Welded portion 15 of the sleeve 12 and the circular straight tube 14 Circular straight tube 15a connecting the protective tube 13 and the heat insulating outer tube 8 The protective tube 13 and the circular straight tube Welded portion 15b of the heat insulating tube 8 and the welded portion 16a of the circular straight tube 15 Welded portion 17 of the protective tube 13 and the sleeve 12 0 CV cable 21 Copper conductor 22 of CV cable 20 Electrical insulator 23 of CV cable 20 Metal sheath 24 of CV cable 20 Waterproof treatment part 30 Conventional pooling eye 31 Pulling eye tension cap 32 Pooling eye sleeve 33 Protection of pooling eye tube

Claims (3)

The pooling eye connected to the end of the superconducting cable has a sleeve that joins the former exposed from the conductor of the superconducting cable at the center of the pooling eye, and the outer end of the sleeve is joined to the heat-insulated pipe inside the superconducting cable And a portion to be joined to the outer tube of the superconducting cable at the end of the protective tube arranged on the outer periphery of the pooling eye, and the inner tube of the heat insulation tube and the sleeve of the pooling eye are connected via a circular straight tube. A circular straight pipe having a thickness greater than the thickness of the inner pipe of the heat insulation pipe and smaller than the thickness of the sleeve, and a circular straight pipe for the outer pipe of the heat insulation pipe and the protection pipe of the pooling eye. through a welded, pulling eye superconducting cable, characterized in Rukoto used as the intermediate position of the thickness and thickness of the protective tube of the circular type linear thickness pipe insulation extravascular tube. Claim isolates the inner and outer tubes of the heat-insulated pipe at the end of the superconducting cable, characterized Rukoto which have a tightness in each space surrounded by the inner space and the inner tube and the outer tube of the inner tube 1 The pooling eye for the superconducting cable described. A superconducting cable laying method using the pooling eye for a superconducting cable according to claim 1.

Images