A high temperature superconducting conductor and a method of making the same

Abstract

The application discloses a high-temperature superconducting conductor and a preparation method thereof, and relates to the technical field of high-temperature superconductivity, wherein the conductor comprises an inner pipe body and an outer pipe body arranged coaxially, a liquid nitrogen convection cooling zone is formed in the inner pipe body, and a vacuum heat insulation cavity is formed between the inner pipe body and the outer pipe body. By forming the liquid nitrogen convection cooling zone in the inner pipe body and the vacuum heat insulation cavity between the inner pipe body and the outer pipe body, the liquid nitrogen can directly soak the superconducting cable for efficient heat exchange, the vacuum heat insulation cavity effectively blocks the radial conduction of environmental heat to the inner pipe body, and the heat load of the refrigeration system is greatly reduced; by electrically connecting the low-temperature end electrode and the superconducting cable and connecting the room-temperature end electrode and the low-temperature end electrode in series to form a loop, the room-temperature end electrode is avoided from directly contacting the superconducting cable, the axial heat leakage along the electrode is reduced, and one end of the liquid nitrogen cooling pipe is communicated with the inner pipe body and the other end of the liquid nitrogen cooling pipe extends to the outside through the outer pipe body, so that the stable supply and the sealing reliability of the liquid nitrogen are ensured.

Description

Technical Field

[0001] This invention relates to the field of high-temperature superconductivity technology, and in particular to a high-temperature superconducting conductor and its preparation method. Background Technology

[0002] High-temperature superconducting conductors are widely used in superconducting magnets for nuclear fusion devices (such as ITER and EAST) and high-voltage superconducting transmission cables. Their core structure generally adopts the traditional design of "superconducting cable + cooling pipe + metal support + armor," relying on cryogenic cooling with liquid nitrogen or liquid helium to maintain the superconducting state and achieve high-current transmission. Specifically, the superconducting cable is made of stacked or wound REBCO or Bi-2212 high-temperature superconducting tape; the cooling pipe is arranged in parallel with the superconducting cable and fixed by metal or ordinary glass fiber supports; the outer stainless steel armor provides structural protection, and the interior of the armor is mostly at atmospheric pressure or a low vacuum environment; the conductor ends are connected to the external circuit through copper electrodes and sealed with rubber or simple metal.

[0003] However, in traditional structures, the armor and superconducting cable are in direct contact through support components. Solid-state heat conduction accounts for over 65% of the total heat leakage. The armor is under normal pressure, and gas convection heat transfer further exacerbates heat leakage, resulting in an overall radial heat leakage of no less than 1.8 W / m. Cooling power consumption accounts for over 40% of the total system power consumption, leading to persistently high operating costs. Simultaneously, the cooling pipes and superconducting cable only achieve partial contact, resulting in uneven cooling medium flow rate, low heat exchange efficiency, and a mismatch between heat leakage and cooling capacity. This causes temperature fluctuations in the superconducting cable to reach ±2.2 K, directly leading to a critical current attenuation of no less than 32% and inducing magnetic flux creep, increasing AC losses to over 2.5 W / m. Summary of the Invention

[0004] This invention provides a high-temperature superconducting conductor and its preparation method, which can solve the problems of high power consumption, high operating costs, low heat exchange efficiency, and mismatch between heat leakage and cooling capacity in the existing technology.

[0005] A high-temperature superconducting conductor includes an inner tube and an outer tube arranged coaxially. A liquid nitrogen convection cooling zone is formed inside the inner tube, and a vacuum-insulated cavity is formed between the inner and outer tubes. A superconducting cable is disposed inside the inner tube. One end of the inner tube is connected to a liquid nitrogen cooling tube, and the other end of the liquid nitrogen cooling tube passes through the outer tube and extends to the outside of the outer tube. Low-temperature end armor is provided at both ends of the inner tube, and a low-temperature end electrode is installed on the low-temperature end armor. The low-temperature end electrode is electrically connected to the superconducting cable. Room-temperature end armor is provided at both ends of the outer tube, and a room-temperature end electrode is installed on the room-temperature end armor. The room-temperature end electrode is electrically connected to the low-temperature end electrode, forming a series circuit. Multiple first support pads are sleeved on the superconducting cable.

[0006] The high-temperature superconducting conductor provided by this invention has, but is not limited to, the following beneficial effects compared to existing technologies: The high-temperature superconducting conductor uses an inner tube and an outer tube arranged coaxially. A liquid nitrogen convection cooling zone is formed inside the inner tube, while a vacuum insulation cavity is formed between the inner and outer tubes. This allows the liquid nitrogen to directly immerse the superconducting cable for efficient heat exchange, while the vacuum insulation cavity effectively blocks the radial conduction of ambient heat to the inner tube, significantly reducing the heat load of the cooling system. By electrically connecting the low-temperature electrode to the superconducting cable and connecting the room-temperature electrode to the low-temperature electrode in series to form a circuit, direct contact between the room-temperature electrode and the superconducting cable is avoided, reducing axial heat leakage along the electrodes. At the same time, one end of the liquid nitrogen cooling pipe is connected to the inner tube, and the other end extends to the outside through the outer tube, ensuring a stable supply of liquid nitrogen and reliable sealing. Multiple first support pads are fitted onto the superconducting cable, providing stable mechanical support and further blocking the solid heat conduction path due to their low thermal conductivity. This significantly reduces the total heat leakage from the environment to the superconducting cable, and the liquid nitrogen cooling capacity matches the heat leakage load, thus effectively solving the problems of high cooling power consumption, high operating costs, low heat exchange efficiency, and mismatch between heat leakage and cooling capacity in existing technologies.

[0007] Furthermore, a first spiral flow channel groove is formed on the first support pad.

[0008] Furthermore, a plurality of second support pads are fitted onto the inner tube body, and the second support pads are provided with second spiral flow channel grooves.

[0009] Furthermore, an inlet pipe is connected to the outer tube, and the outlet end of the inlet pipe is located inside the vacuum insulation cavity.

[0010] Furthermore, both the inner and outer tubes are made of seamless stainless steel tubing, with the inner tube having a wall thickness of 1–2 mm and the outer tube having a wall thickness of 2–3 mm.

[0011] Furthermore, the superconducting cable is formed by stacking and winding REBCO or Bi-2212 high-temperature superconducting tapes, the superconducting tapes having a width of 4 mm and a thickness of 0.1 mm.

[0012] Furthermore, the first support pad and the second support pad are staggered.

[0013] Furthermore, both the first and second support pads are made of G10 epoxy glass cloth laminate, with a thermal conductivity of not more than 0.3 W / (m·K) and a compressive strength of not less than 150MPa.

[0014] A method for preparing a high-temperature superconducting conductor, based on the aforementioned high-temperature superconducting conductor, includes the following steps: S1, stacking and winding high-temperature superconducting tape into a superconducting cable and wrapping it with an insulating layer, fitting multiple first support pads onto the superconducting cable and fixing them, and then inserting the entire assembly into an inner tube; S2, welding the low-temperature end armor to both ends of the inner tube, installing the low-temperature end electrodes and electrically connecting them to the superconducting cable; S3, inserting the entire inner tube into an outer tube, welding the room-temperature end armor to both ends of the outer tube, installing the room-temperature end electrodes and electrically connecting them to the low-temperature end electrodes to form a series circuit; S4: connecting one end of a liquid nitrogen cooling pipe to the inner tube, and having the other end pass through the outer tube and extend to the outside of the outer tube; evacuating the vacuum insulation cavity to a vacuum level not less than 1×10⁻⁶. - The pressure is increased to 3Pa, and then supercooled liquid nitrogen is introduced for testing. Once the test is passed, the finished product is obtained.

[0015] Furthermore, the spacing between the first support pads is 100-150 mm, and the temperature of the supercooled liquid nitrogen is 65-70 K, with a pressure of 0.5-0.8 MPa. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a high-temperature superconducting conductor according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the interior of a high-temperature superconducting conductor according to an embodiment of the present invention; Figure 3 for Figure 1 Schematic diagram of the inner tube structure; Figure 4 for Figure 1 Schematic diagram of the structure of the superconducting cable; Figure 5 for Figure 1 A schematic diagram of the structure of the first support pad; Figure 6 This is a flowchart illustrating a method for preparing a high-temperature superconducting conductor according to an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1. Inner tube; 2. Outer tube; 3. Liquid nitrogen convection cooling zone; 4. Vacuum insulation cavity; 5. Superconducting cable; 6. Low-temperature end armor; 7. Low-temperature end electrode; 8. Room temperature end armor; 9. Room temperature end electrode; 10. First support pad; 11. Liquid nitrogen cooling pipe; 12. First spiral flow channel groove; 13. Second support pad; 14. Second spiral flow channel groove; 15. Liquid inlet pipe. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, specific embodiments of this application are described clearly and completely below with reference to the accompanying drawings. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0019] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," "comprise," etc., in the specification, claims, and accompanying drawings of this application are open-ended terms, indicating that a method comprises one or more steps, or an apparatus comprises one or more elements, but do not exclude the inclusion of other steps or elements. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or primary / secondary relationship. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this application, it should be understood that the terms "upper," "lower," "left," "right," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Similarly, it should be noted that the meanings of the X-axis, Y-axis, and Z-axis are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0021] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0022] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0023] like Figure 1-4 As shown in the figure, a high-temperature superconducting conductor provided by an embodiment of the present invention includes an inner tube 1 and an outer tube 2 arranged coaxially. A liquid nitrogen convection cooling zone 3 is formed inside the inner tube 1, and a vacuum insulation cavity 4 is formed between the inner tube 1 and the outer tube 2. A superconducting cable 5 is disposed inside the inner tube 1. One end of the inner tube 1 is connected to a liquid nitrogen cooling pipe 11, and the other end of the liquid nitrogen cooling pipe 11 passes through the outer tube 2 and extends to the outside of the outer tube 2. Low-temperature end armor 6 is respectively disposed at both ends of the inner tube 1, and a low-temperature end electrode 7 is installed on the low-temperature end armor 6. The low-temperature end electrode 7 is electrically connected to the superconducting cable 5. Room temperature end armor 8 is respectively disposed at both ends of the outer tube 2, and a room temperature end electrode 9 is installed on the room temperature end armor 8. The room temperature end electrode 9 is electrically connected to the low-temperature end electrode 7 to form a series circuit. A plurality of first support pads 10 are sleeved on the superconducting cable 5.

[0024] In this embodiment, an inner tube 1 and an outer tube 2 are coaxially arranged, forming a liquid nitrogen convection cooling zone 3 inside the inner tube 1. At the same time, a vacuum insulation cavity 4 is formed between the inner tube 1 and the outer tube 2, allowing liquid nitrogen to directly immerse the superconducting cable 5 for efficient heat exchange. The vacuum insulation cavity 4 effectively blocks the radial conduction of ambient heat to the inner tube 1, significantly reducing the heat load of the refrigeration system. By electrically connecting the low-temperature electrode 7 to the superconducting cable 5 and connecting the room-temperature electrode 9 to the low-temperature electrode 7 in series to form a circuit, the room-temperature electrode 9 is prevented from directly contacting the superconducting cable 5, reducing axial heat leakage along the electrode. Meanwhile, one end of the liquid nitrogen cooling pipe 11 is connected to the inner tube 1, and the other end extends to the outside through the outer tube 2, ensuring a stable supply of liquid nitrogen and reliable sealing. Multiple first support pads 10 are fitted on the superconducting cable 5, providing stable mechanical support and further blocking the solid heat conduction path due to their low thermal conductivity. This significantly reduces the total heat leakage from the environment to the superconducting cable 5, and the liquid nitrogen cooling capacity matches the heat leakage load, thereby effectively solving the problems of high cooling power consumption, high operating costs, low heat exchange efficiency, and mismatch between heat leakage and cooling capacity in the existing technology.

[0025] like Figure 2 and Figure 5 As shown, a first spiral flow channel groove 12 is provided on the first support pad 10.

[0026] In this embodiment, by creating a first spiral flow channel 12 on the first support pad 10, the spiral flow channel 12 is uniformly distributed along the inner ring or circumferential surface of the first support pad 10. When liquid nitrogen flows in the liquid nitrogen convection cooling zone 3 inside the inner tube 1, the first spiral flow channel 12 guides the liquid nitrogen to form a spiral turbulent flow, disrupting the laminar boundary layer between the liquid nitrogen and the superconducting cable 5, thereby increasing the convective heat transfer coefficient between the liquid nitrogen and the surface of the superconducting cable 5 to 150. W / (m²·K) or higher; at the same time, the presence of the spiral flow channel 12 reduces the contact area between the first support pad 10 and the superconducting cable 5 and the inner wall of the inner tube 1, further reducing the solid heat conduction path and reducing the heat leakage along the first support pad 10; in addition, the spiral structure of the spiral flow channel 12 extends the residence time and flow path of liquid nitrogen on the surface of the superconducting cable 5, ensuring uniform temperature distribution along the entire length of the superconducting cable 5, thereby effectively solving the problem of unstable superconducting performance caused by low heat exchange efficiency and mismatch between heat leakage and cooling capacity in the prior art.

[0027] like Figure 2 and Figure 5 As shown, a plurality of second support pads 13 are fitted on the inner tube body 1, and a second spiral flow channel groove 14 is opened on the second support pads 13.

[0028] In this embodiment, the second support pad 13 is located inside the vacuum insulation cavity 4. Its inner ring fits with the outer wall of the inner tube 1, and its outer ring fits with the inner wall of the outer tube 2, providing stable radial support for the inner tube 1, ensuring the coaxiality of the inner tube 1 and the outer tube 2, and effectively resisting alternating electromagnetic forces of not less than 100 kN. At the same time, the setting of the second spiral flow channel 14 greatly reduces the contact area between the second support pad 13 and the outer wall of the inner tube 1 and the inner wall of the outer tube 2. Since there is no fluid in the vacuum insulation cavity 4, the spiral flow channel 14 is not used for flow guidance, but rather to reduce the solid thermal conduction cross-sectional area and increase the thermal resistance of the solid heat conduction path along the second support pad 13, thereby further optimizing the overall thermal insulation performance of the vacuum insulation cavity 4.

[0029] Specifically, the tortuous structure of the spiral flow channel 14 increases the surface creepage distance of the second support pad 13, effectively preventing insulation breakdown and improving electrical safety under high-voltage conditions. Multiple second support pads 13 are uniformly arranged axially, working in conjunction with the first support pad 10 to simultaneously reduce heat leakage in both radial and axial dimensions. This ensures that the cooling capacity of the liquid nitrogen is entirely used to maintain the superconducting state of the superconducting cable 5, thereby significantly reducing system cooling power consumption and extending the conductor's stable operating life.

[0030] like Figure 1 and Figure 2 As shown, an inlet pipe 15 is connected to the outer tube 2, and the outlet end of the inlet pipe 15 is located inside the vacuum insulation cavity 4.

[0031] In this embodiment, by connecting the liquid inlet pipe 15 to the outer tube 2 and setting the liquid outlet end of the liquid inlet pipe 15 inside the vacuum insulation cavity 4, the liquid inlet pipe 15 can serve as an auxiliary cooling channel to introduce liquid nitrogen or cold nitrogen into the vacuum insulation cavity 4, so that the liquid nitrogen can be directly sprayed or contacted with the outer wall of the inner tube 1, thereby providing external auxiliary cooling for the inner tube 1. This forms a dual cooling effect with the liquid nitrogen convection cooling zone 3 inside the inner tube 1, significantly improving the temperature uniformity of the superconducting cable 5. At the same time, the liquid outlet end of the liquid inlet pipe 15 is located inside the vacuum insulation cavity 4, and can actively absorb the heat transferred from the outer wall of the inner tube 1 and the second support pad 13 by utilizing the phase change heat absorption effect of liquid nitrogen, further reducing heat leakage in the solid heat conduction path, and improving the overall insulation performance of the vacuum insulation cavity 4 by about 15%.

[0032] Specifically, the liquid inlet pipe 15 can serve as a backup cooling channel. In the event of a failure in the main cooling circuit (liquid nitrogen cooling pipe 11) or insufficient cooling capacity, liquid nitrogen can be replenished into the vacuum insulation cavity 4 through the liquid inlet pipe 15 to provide emergency cooling for the inner tube 1. This prevents the superconducting cable 5 from losing its superconductivity due to excessive temperature rise, significantly improving the system safety redundancy and operational reliability of the high-temperature superconducting conductor. It also effectively solves the problems of low reliability and uneven temperature distribution of a single cooling circuit in the prior art.

[0033] like Figure 1 and Figure 2 As shown, both the inner tube 1 and the outer tube 2 are seamless stainless steel tubes. The wall thickness of the inner tube 1 is 1-2 mm, and the wall thickness of the outer tube 2 is 2-3 mm.

[0034] In this embodiment, the stainless steel seamless tube maintains excellent mechanical properties (yield strength ≥ 200 MPa) at liquid nitrogen temperature (77 K), and its thermal conductivity (approximately 15 W / (m·K)) is much lower than that of commonly used thermally conductive materials such as copper and aluminum, which can effectively reduce axial heat leakage along the tube wall. The inner tube 1 has a thinner wall thickness of 1-2 mm, which minimizes the thermal conductivity cross-sectional area and heat capacity of the inner tube 1 while ensuring that it can withstand liquid nitrogen pressure (not less than 2 MPa), thereby reducing the heat conducted from the outer tube 2 through the wall of the inner tube 1 to the superconducting cable 5. The outer tube 2 has a thicker wall thickness of 2-3 mm, which can provide sufficient structural strength to resist external atmospheric pressure (the vacuum insulation cavity 4 is under negative pressure) and alternating electromagnetic force of not less than 100 kN, preventing the outer tube 2 from buckling and deforming. At the same time, the thicker outer tube 2 increases the thermal resistance conducted from room temperature to the inside, reducing radial heat leakage.

[0035] like Figure 1 and Figure 2 As shown, the superconducting cable 5 is made of REBCO or Bi-2212 high-temperature superconducting tape stacked and wound, with a width of 4 mm and a thickness of 0.1 mm.

[0036] In this embodiment, REBCO and Bi-2212 high-temperature superconducting tapes have extremely high critical current densities at liquid nitrogen temperatures (77K). The 4mm wide and 0.1mm thick tapes provide sufficient current-carrying cross-sectional area while ensuring mechanical flexibility. The superconducting cable 5 formed by stacking and winding has a critical current of not less than 15kA under self-field conditions at 77K, and a rated operating current of more than 10kA, meeting the high current requirements of nuclear fusion devices and high-voltage transmission cables. The 0.1mm thin tape helps to reduce eddy current losses inside the tape and reduce heat generation under AC conditions. At the same time, the tape of this size has good bending radius adaptability and is not easy to damage the superconducting layer during winding, ensuring the long-term structural stability of the superconducting cable 5. The cable structure formed by stacking and winding multiple thin tapes increases the surface area of ​​the superconducting cable 5, allowing it to fully contact the liquid nitrogen in the liquid nitrogen convection cooling zone 3 inside the inner tube 1, greatly improving the heat exchange efficiency.

[0037] Specifically, the high-temperature superconducting properties of REBCO or Bi-2212 materials allow the superconducting state to be maintained at relatively high temperatures (65-77K). Combined with the vacuum insulation and liquid nitrogen immersion cooling of this invention, the superconducting cable 5 can operate stably within a temperature fluctuation range of ≤±0.3K, with a critical current attenuation rate of less than 2%, thereby effectively solving the problems of unstable critical current and high AC loss in the prior art.

[0038] like Figure 2 and Figure 3 As shown, the first support pad 10 and the second support pad 13 are staggered.

[0039] In this embodiment, by staggering the first support pad 10 and the second support pad 13 in the axial direction, the support points on the inner and outer sides of the inner tube 1 are staggered, avoiding the overlap of the first support pad 10 and the second support pad 13 in the same axial position, which would lead to local stress concentration or heat leakage superposition. After staggering, the stress points of the inner tube 1 are evenly distributed along the axial direction. When subjected to an alternating electromagnetic force of not less than 100 kN, the bending stress and deformation of the inner tube 1 are significantly reduced, effectively preventing local buckling or fatigue damage to the inner tube 1.

[0040] In this configuration, the first support pad 10 is located inside the inner tube 1 and contacts the superconducting cable 5, while the second support pad 13 is located outside the inner tube 1 and contacts the outer tube 2. The staggered arrangement of the two interrupts the axial heat conduction path along the wall of the inner tube 1. The heat conducted from the superconducting cable 5 through the first support pad 10 to the inner wall of the inner tube 1 must pass through a section of the inner tube 1 wall without the pad before reaching the position of the second support pad 13, and then be conducted to the outer tube 2 through the second support pad 13. This significantly increases the total thermal resistance of the solid heat conduction path, reducing axial heat leakage by approximately 25%.

[0041] like Figure 1 and Figure 2 As shown, the first support pad 10 and the second support pad 13 are both made of G10 epoxy glass cloth laminate, with a thermal conductivity of not more than 0.3 W / (m·K) and a compressive strength of not less than 150MPa.

[0042] In this embodiment, the extremely low thermal conductivity ensures that the first support pad 10 and the second support pad 13, while providing mechanical support, almost do not form a solid heat conduction path. The first support pad 10 reduces the heat leakage between the superconducting cable 5 and the inner wall of the inner tube 1 to a negligible level, and the second support pad 13 also significantly reduces the heat leakage between the outer wall of the inner tube 1 and the inner wall of the outer tube 2, reducing the proportion of solid heat conduction in the total heat leakage from more than 65% in the traditional structure to no more than 10%. The compressive strength of not less than 150 MPa ensures that the first support pad 10 and the second support pad 13 do not undergo compression deformation or brittle fracture when subjected to an alternating electromagnetic force of not less than 100 kN, and maintain dimensional stability even after more than 1000 hours of long-term operation.

[0043] Among them, G10 material has excellent electrical insulation properties (dielectric strength ≥20 kV / mm), which can effectively prevent high voltage breakdown between superconducting cable 5 and inner tube 1, and between inner tube 1 and outer tube 2. Combined with the vacuum environment of vacuum insulation cavity 4, the insulation reliability is further improved. The strength of G10 epoxy glass cloth laminate does not decrease but increases at liquid nitrogen temperature (77K), and its thermal shrinkage rate is similar to that of stainless steel pipe, avoiding loosening of fit or damage of internal stress caused by shrinkage difference at low temperature.

[0044] like Figure 6 As shown, a method for preparing a high-temperature superconducting conductor, based on a high-temperature superconducting conductor, includes the following steps: S1, stacking and winding high-temperature superconducting tape into a superconducting cable 5 and wrapping it with an insulating layer, fitting multiple first support pads 10 onto the superconducting cable 5 and fixing them, and then inserting the whole into an inner tube 1; S2, welding the low-temperature end armor 6 to both ends of the inner tube 1, installing the low-temperature end electrode 7 and electrically connecting it to the superconducting cable 5; S3, inserting the inner tube 1 into an outer tube 2, welding the room temperature end armor 8 to both ends of the outer tube 2, installing the room temperature end electrode 9 and electrically connecting it to the low-temperature end electrode 7, forming a series circuit; S4: connecting one end of a liquid nitrogen cooling pipe 11 to the inner tube 1, and the other end passing through the outer tube 2 and extending to the outside of the outer tube 2; evacuating the vacuum insulation cavity 4 to a vacuum level not less than 1×10⁻⁶. - The pressure is increased to 3 Pa, and then supercooled liquid nitrogen is introduced for testing. Once the test is passed, the finished product is obtained.

[0045] In this embodiment, by stacking and winding high-temperature superconducting tape into a superconducting cable 5 and wrapping it with an insulating layer, and then fitting multiple first support pads 10 onto the superconducting cable 5 and fixing them, the entire assembly is installed into the inner tube 1. This ensures the relative position stability of the first support pads 10 and the superconducting cable 5, preventing displacement due to electromagnetic force during operation. Simultaneously, the insulating layer protects the superconducting tape from damage. By welding the low-temperature end armor 6 to both ends of the inner tube 1 and installing low-temperature end electrodes 7, making them electrically connected to the superconducting cable 5, the sealing of the low-temperature end and current extraction are achieved. The structure ensures the airtightness of the ends of the vacuum insulation cavity 4. By inserting the inner tube 1 entirely into the outer tube 2, welding the room temperature end armor 8, and installing the room temperature end electrode 9, connecting it in series with the low temperature end electrode 7, this series circuit avoids direct contact between the room temperature end electrode 9 and the superconducting cable 5, structurally cutting off the axial heat leakage path along the electrode. By connecting one end of the liquid nitrogen cooling pipe 11 to the inner tube 1 and extending the other end through the outer tube 2 to the outside, the sealing reliability of the liquid nitrogen supply channel is ensured. At the same time, the vacuum insulation cavity 4 is evacuated to a vacuum level of not less than 1×10⁻⁶. - The radial heat leakage was effectively blocked by a pressure of 3Pa. Finally, supercooled liquid nitrogen was introduced for testing, verifying the conductor's cooling efficiency and superconducting performance. Each step was independent and coordinated, ensuring the positioning accuracy of the first support pad 10, the reliability of the end electrode connection, and the sealing of the vacuum cavity. The resulting high-temperature superconducting conductor has the advantages of low heat leakage, high cooling efficiency, stable structure, and reliable end sealing.

[0046] Furthermore, the spacing of the first support pads 10 is 100-150 mm, the temperature of the supercooled liquid nitrogen is 65-70 K, and the pressure is 0.5-0.8 MPa.

[0047] In this embodiment, the first support pads 10 are uniformly spaced on the superconducting cable 5 at intervals of 100-150 mm. This ensures that the radial displacement of the superconducting cable 5 does not exceed 0.1 mm when subjected to an alternating electromagnetic force of not less than 100 kN (too large a spacing will lead to insufficient support and cable bending, while too small a spacing will increase heat leakage points and assembly difficulty). It also keeps the number of pads within a reasonable range, minimizing heat leakage through solid-state heat conduction along the first support pads 10. Simultaneously, the temperature of the supercooled liquid nitrogen is 65-70 K (below the standard boiling point of 77 K), and the pressure is 0.5-0.8 MPa. This supercooling effectively suppresses the vaporization phenomenon caused by localized temperature rise during the flow of liquid nitrogen, preventing bubbles from adhering to the surface of the superconducting cable 5 and forming a gas film insulation layer, thus maintaining the convective heat transfer coefficient stably at 150. The pressure of W / (m²·K) is above 0.5-0.8 MPa, which ensures the driving force for the flow of liquid nitrogen in the inner tube 1 (flow velocity 0.5-1.0 m / s) without placing excessive pressure requirements on the thin-walled inner tube 1 (wall thickness 1-2 mm) (pressure resistance not less than 2 MPa). The supercooled temperature range of 65-70 K allows the superconducting cable 5 to operate in a range far below the critical temperature (REBCO about 90 K), increasing the critical current by about 15-20%, and controlling temperature fluctuations within ±0.3 K. At the same time, the lower operating temperature reduces the AC loss of the superconducting tape.

[0048] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A high-temperature superconducting conductor, characterized in that, It includes an inner tube (1) and an outer tube (2) arranged coaxially. A liquid nitrogen convection cooling zone (3) is formed inside the inner tube (1). A vacuum insulation cavity (4) is formed between the inner tube (1) and the outer tube (2). A superconducting cable (5) is installed inside the inner tube (1). One end of the inner tube (1) is connected to a liquid nitrogen cooling pipe (11). The other end of the liquid nitrogen cooling pipe (11) passes through the outer tube (2) and extends to the outside of the outer tube (2). The inner tube (1) is provided with low-temperature end armor (6) at both ends, and a low-temperature end electrode (7) is installed on the low-temperature end armor (6). The low-temperature end electrode (7) is electrically connected to the superconducting cable (5). The outer tube (2) is provided with room temperature end armor (8) at both ends, and a room temperature end electrode (9) is installed on the room temperature end armor (8). The room temperature end electrode (9) is electrically connected to the low-temperature end electrode (7) to form a series circuit. Multiple first support pads (10) are fitted onto the superconducting cable (5).

2. The high-temperature superconducting conductor as described in claim 1, characterized in that, The first support pad (10) has a first spiral flow channel groove (12).

3. The high-temperature superconducting conductor as described in claim 1, characterized in that, The inner tube (1) is fitted with a plurality of second support pads (13), and the second support pads (13) are provided with second spiral flow channel grooves (14).

4. The high-temperature superconducting conductor as described in claim 1, characterized in that, The outer tube (2) is connected to an inlet pipe (15), and the outlet end of the inlet pipe (15) is located inside the vacuum insulation cavity (4).

5. The high-temperature superconducting conductor as described in claim 1, characterized in that, Both the inner tube (1) and the outer tube (2) are seamless stainless steel tubes. The wall thickness of the inner tube (1) is 1-2 mm, and the wall thickness of the outer tube (2) is 2-3 mm.

6. The high-temperature superconducting conductor as described in claim 1, characterized in that, The superconducting cable (5) is made by stacking and winding REBCO or Bi-2212 high-temperature superconducting tape, the superconducting tape having a width of 4 mm and a thickness of 0.1 mm.

7. The high-temperature superconducting conductor as described in claim 1, characterized in that, The first support pad (10) and the second support pad (13) are staggered.

8. The high-temperature superconducting conductor as described in claim 1, characterized in that, The first support pad (10) and the second support pad (13) are both made of G10 epoxy glass cloth laminate, with a thermal conductivity of not more than 0.3 W / (m·K) and a compressive strength of not less than 150MPa.

9. A method for preparing a high-temperature superconducting conductor, characterized in that, Applied to any one of the high-temperature superconducting conductors as described in claims 1-8, comprising the following steps: S1. Stack and wind high-temperature superconducting tape into a superconducting cable (5) and wrap it with an insulating layer. Place multiple first support pads (10) on the superconducting cable (5) and fix them. Then, insert the whole into the inner tube (1). S2. Weld the low-temperature end armor (6) to both ends of the inner tube (1), install the low-temperature end electrode (7) and make it electrically connected to the superconducting cable (5); S3. The inner tube (1) is installed into the outer tube (2) as a whole. The room temperature end armor (8) is welded to both ends of the outer tube (2). The room temperature end electrode (9) is installed and electrically connected to the low temperature end electrode (7) to form a series circuit. S4: Connect one end of the liquid nitrogen cooling pipe (11) to the inner tube (1), and the other end passes through the outer tube (2) and extends to the outside of the outer tube (2); evacuate the vacuum insulation cavity (4) to a level not lower than 1×10 - The pressure is increased to 3 Pa, and then supercooled liquid nitrogen is introduced for testing. Once the test is passed, the finished product is obtained.

10. The method for preparing a high-temperature superconducting conductor as described in claim 9, characterized in that, The spacing of the first support pad (10) is 100-150 mm, the temperature of the supercooled liquid nitrogen is 65-70 K, and the pressure is 0.5-0.8 MPa.

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