Superconducting cable

Abstract

The invention relates to the technical field of power transmission, in particular to a superconducting cable which comprises a central light unit, a central conductor layer and a superconductor layer which are sequentially arranged in a layered mode from inside to outside, the central light unit comprises a protection tube and a temperature measurement sensing optical fiber arranged in the protection tube in a penetrating mode, and the central conductor layer is formed by twisting a plurality of metal conductor single wires and wraps the protection tube. The superconductor layer wraps the central conductor layer. The temperature measurement sensing optical fiber of the central optical unit is connected with the temperature measurement device, so that temperature monitoring in the full-length range of the central conductor layer can be realized, and effective monitoring of the temperature along the full-length range of the superconducting cable can be conveniently and economically realized under the conditions that the overall structure of the superconducting cable is not influenced and the flexibility and pressure measurement resistance of the superconducting cable are ensured; the temperature of the superconducting cable is measured in a quasi-distributed mode, the positions of operation defects or fault points related to thermal disturbance on the superconducting cable can be found in time, the operation state of the superconducting cable is well monitored, and normal work and safe operation of the superconducting cable are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission, and in particular to a superconducting cable. Background Art

[0002] The structure and operating conditions of superconducting cables are very complex. They must operate below the critical current, critical temperature and critical magnetic field strength to ensure safe operation. Once any critical value is exceeded, the superconducting cable will quench. Once a failure occurs, it may affect the stability of the entire power supply system. Therefore, it is very necessary to provide monitoring and protection for the operation of superconducting cables and power equipment. Its research and development has important theoretical and practical significance.

[0003] For large superconducting cables, the traditional terminal voltage measurement method is easily affected by electromagnetic interference caused by high voltage and large current, and it is impossible to achieve continuous distributed measurement along the length of the cable. The resistance thermal effect generated when the superconducting cable is quenched will cause heat to accumulate rapidly in the local area, causing the temperature of the fault point to continue to rise. Therefore, it is possible to determine whether the superconducting cable has a fault by monitoring the temperature rise of the cable in real time. Traditional electrical temperature detectors are mostly point sensors, which are difficult to meet the needs of long-distance, large-scale distributed detection.

[0004] When superconducting cables are in operation, they are at liquid nitrogen temperature (77K). Traditional low-temperature temperature measurements often use thermal resistors and thermocouple temperature sensors such as PT-100 platinum resistors, but these temperature sensors usually cannot meet the measurement requirements of superconducting cables. There are mainly two problems: First, superconducting cables are usually in a high-voltage and high-current operating environment during operation. Ordinary thermal resistors and thermocouple sensors use voltage sensing. The electromagnetic interference caused by the large voltage will affect the sensing performance and cause the temperature measurement accuracy to decrease; second, superconducting cables are usually used for long-distance power transmission, and the cable length is usually more than 1km. Therefore, the temperature monitoring needs to cover the entire cable length so that the quench fault can be quickly and accurately located when a quench fault occurs. Ordinary sensors are mostly point measurements, which can only measure the temperature of a fixed point and cannot monitor the temperature of the entire length of the cable. If you want to achieve continuous distributed temperature measurement, you need to arrange a large number of temperature sensors, which not only leads to low economic benefits, but also affects the transmission performance of superconducting cables. Therefore, the existing temperature measurement methods such as thermocouples, thermal resistors and other traditional temperature sensors are difficult to install and have complex wiring, which will have a great impact on the superconducting cable structure, and the temperature measurement accuracy is susceptible to electromagnetic interference, and cannot be used for temperature monitoring along the superconducting cable. In addition, superconducting cables have certain operating temperature requirements and need to operate in a closed liquid nitrogen environment. The existing temperature monitoring technology uses temperature monitoring chips, which can only monitor temperature points in a small range, and it is difficult to perform comprehensive and long-term monitoring of superconducting cables over long distances and large areas. Therefore, it is necessary to explore new measurement methods to monitor the real-time operating temperature of superconducting cables.

[0005] At present, there have been studies on applying optical fiber temperature measurement to temperature measurement along superconducting cables, but the research is still at the stage of installing the optical fiber on the outer wall of the superconducting cable skeleton, the insulation layer or the shielding layer. Due to the low thermal conductivity of the insulation layer, the temperature changes on the superconducting cable conductor cannot be sensed by the optical fiber through the insulation layer, and it is still impossible to effectively measure the temperature along the conductor of the superconducting cable. Summary of the invention

[0006] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a superconducting cable, which can realize effective monitoring of the temperature along the entire length of the superconducting cable.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a superconducting cable, comprising a central optical unit, a central conductor layer and a superconductor layer which are sequentially arranged in layers from the inside to the outside, wherein the central optical unit comprises a protective tube and a temperature sensing optical fiber passing through the protective tube, the central conductor layer is formed by twisting a plurality of metal conductor single wires and covering the protective tube, and the superconductor layer covers the central conductor layer.

[0009] Preferably, the cross-section of the metal conductor single wire is arched and gradually expands from the inside to the outside.

[0010] Preferably, the protection tube is a stainless steel tube.

[0011] Preferably, it also includes an inner insulating layer, a shielding layer, an outer insulating layer, a sheath, a liquid nitrogen layer and a vacuum layer which are layered from the outside of the superconductor layer from the inside to the outside, and an optical fiber microcable is arranged in any one or more layers of the superconductor layer, the shielding layer, the liquid nitrogen layer and the vacuum layer, and the optical fiber microcable includes a temperature measuring sensing optical fiber and a high-strength sheath covering the temperature measuring sensing optical fiber.

[0012] Preferably, the surface of the temperature sensing optical fiber is coated with a polyimide cladding.

[0013] Preferably, the superconductor layer comprises one or more superconducting tape layers, each superconducting tape layer is formed by twisting a plurality of superconducting tapes and a gap is formed between two adjacent superconducting tapes, and an optical fiber microcable is laid in the gap between two adjacent superconducting tapes.

[0014] Preferably, the shielding layer includes an inner shielding layer covering the inner insulating layer and an outer shielding layer covering the inner shielding layer, the inner shielding layer is a superconducting tape shielding layer, the outer shielding layer is a copper tape shielding layer, the outer shielding layer is formed by twisting a plurality of copper tapes together and a gap is formed between two adjacent copper tapes, and an optical fiber microcable is laid in the gap between the two adjacent copper tapes.

[0015] Preferably, the liquid nitrogen layer includes a first corrugated tube spaced outside the sheath and liquid nitrogen filled between the first corrugated tube and the sheath, and an optical fiber microcable is arranged in the first corrugated tube.

[0016] Preferably, the vacuum layer includes a cladding covered with a liquid nitrogen layer, a second bellows spaced outside the cladding, and a vacuum cavity formed between the second bellows and the cladding, and an optical fiber microcable is arranged in the cladding and / or the second bellows.

[0017] Preferably, a vibration sensing optical fiber is provided in at least the liquid nitrogen layer and / or the vacuum layer.

[0018] Compared with the prior art, the present invention has significant improvements:

[0019] The present invention arranges a central optical unit inside the central conductor layer of a superconducting cable, wherein the central optical unit includes a temperature sensing optical fiber and a protection tube for protecting the temperature sensing optical fiber. By connecting the temperature sensing optical fiber of the central optical unit with a temperature measuring device, temperature monitoring within the entire length of the central conductor layer can be achieved. Thus, without affecting the overall structure of the superconducting cable and ensuring that the superconducting cable is soft and resistant to pressure measurement, effective monitoring of the temperature along the entire length of the superconducting cable can be conveniently and economically achieved, and quasi-distributed measurement of the temperature of the superconducting cable can be performed. Through quasi-distributed temperature detection along the superconducting cable, the location of operating defects or fault points related to thermal disturbances on the superconducting cable can be discovered in time, thereby effectively monitoring the operating state of the superconducting cable and ensuring the normal operation and safe operation of the superconducting cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic cross-sectional view of a superconducting cable according to Embodiment 1 of the present invention.

[0021] Figure 2 It is a cross-sectional schematic diagram of a central optical unit in a superconducting cable according to the first embodiment of the present invention.

[0022] Figure 3 It is a cross-sectional schematic diagram of an optical fiber microcable in the superconducting cable of the first embodiment of the present invention.

[0023] Figure 4 It is a schematic cross-sectional view of a superconducting cable according to the second embodiment of the present invention.

[0024] Figure 5 It is a cross-sectional schematic diagram of a central optical unit and a central conductor layer in a superconducting cable according to the second embodiment of the present invention.

[0025] The reference numerals are described as follows:

[0026] 100 Center Light Unit

[0027] 101 Protection tube

[0028] 200 Fiber Optic Micro Cable

[0029] 201 High strength protective layer

[0030] 300 Temperature sensing optical fiber

[0031] 301 Polyimide cladding

[0032] 1 Center conductor layer

[0033] 11 Metal conductor single wire

[0034] 2 Superconductor layer

[0035] 21 Superconducting tape layer

[0036] 3 Inner insulation layer

[0037] 4 Shielding layer

[0038] 41 Inner shield

[0039] 42 Outer shield

[0040] 5 Outer insulation layer

[0041] 6 Sheath

[0042] 7 Liquid Nitrogen Layer

[0043] 71 First Bellows

[0044] 72 Liquid Nitrogen

[0045] 8 Vacuum Layer

[0046] 81 Cladding

[0047] 82 Second bellows

[0048] 83 Vacuum chamber

[0049] 91 First protective layer

[0050] 92 Second protection layer

[0051] 93 Third protection layer

[0052] 94 Fourth protection layer

[0053] 95 Fifth protection layer

[0054] 96 Sixth protection layer

[0055] 97 Seventh Protection Layer DETAILED DESCRIPTION

[0056] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0057] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0058] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0060] Embodiment 1

[0061] like Figures 1 to 3 FIG. 1 is a first embodiment of a superconducting cable provided by the present invention.

[0062] See also Figure 1 The superconducting cable of the first embodiment includes a central optical unit 100, a central conductor layer 1 and a superconductor layer 2 which are sequentially arranged in layers from the inside to the outside. Further, the superconducting cable of the first embodiment also includes an inner insulating layer 3, a shielding layer 4, an outer insulating layer 5, a sheath 6, a liquid nitrogen layer 7 and a vacuum layer 8 which are sequentially arranged in layers from the outside of the superconductor layer 2 from the inside to the outside. The central optical unit 100, the central conductor layer 1, the superconductor layer 2, the inner insulating layer 3, the shielding layer 4, the outer insulating layer 5, the sheath 6, the liquid nitrogen layer 7 and the vacuum layer 8 respectively constitute different cable structure layers. Preferably, protective layers are arranged between different cable structure layers to prevent wear and tear between different cable structure layers and cause mutual damage.

[0063] The central light unit 100 is arranged inside the central conductor layer 1. Figure 2 The central optical unit 100 includes a protective tube 101 and a temperature sensing optical fiber 300 inserted into the protective tube 101. One or more temperature sensing optical fibers 300 may be arranged in parallel in the protective tube 101, and there may be a gap between the temperature sensing optical fiber 300 and the tube wall of the protective tube 101. Preferably, the surface of the temperature sensing optical fiber 300 is coated with a polyimide cladding 301 to ensure the mechanical strength and low temperature resistance of the temperature sensing optical fiber 300. The protective tube 101 protects the temperature sensing optical fiber 300 arranged inside the central conductor layer 1 and increases the strength of the central optical unit 100. Preferably, the protective tube 101 is a stainless steel tube. The temperature sensing optical fiber 300 of the central optical unit 100 extends along the axial direction of the superconducting cable and covers the entire length of the superconducting cable. By connecting the temperature sensing optical fiber 300 to the temperature measuring device, temperature monitoring within the entire length range can be achieved.

[0064] The central conductor layer 1 is formed by twisting a number of metal conductor single wires 11, and the metal conductor single wires 11 are preferably copper conductors, that is, the central conductor layer 1 is a copper conductor. The central conductor layer 1 covers the protective tube 101 of the central optical unit 100, so that the central optical unit 100 is arranged inside the central conductor layer 1. A first protective layer 91 is arranged between the central conductor layer 1 and the protective tube 101 of the central optical unit 100, and the first protective layer 91 is made of low-temperature resistant material. The temperature of the central conductor layer 1 can be monitored by the temperature sensing optical fiber 300 of the central optical unit 100, so that the temperature along the entire length of the superconducting cable can be effectively monitored conveniently and economically without affecting the overall structure of the superconducting cable and ensuring the softness and pressure resistance of the superconducting cable. The temperature of the superconducting cable is quasi-distributedly measured. Through the quasi-distributed temperature detection along the superconducting cable, the operation defects or fault points related to thermal disturbance on the superconducting cable can be found in time, so as to monitor the operation status of the superconducting cable well and ensure the normal operation and safe operation of the superconducting cable.

[0065] The superconductor layer 2 covers the central conductor layer 1. A second protective layer 92 is provided between the superconductor layer 2 and the central conductor layer 1. The second protective layer 92 is made of a low-temperature resistant material. The superconductor layer 2 is the power supply part of the superconducting cable. In the event of a quench, the copper conductor of the central conductor layer 1 conducts electricity, which can avoid large-scale failure of the superconducting cable.

[0066] In the first embodiment, further, an optical fiber microcable 200 is provided in any one or more layers of the superconductor layer 2, the shielding layer 4, the liquid nitrogen layer 7 and the vacuum layer 8. Figure 3 , the optical fiber microcable 200 includes a temperature sensing optical fiber 300 and a high-strength sheath 201 covering the temperature sensing optical fiber 300. Preferably, the surface of the temperature sensing optical fiber 300 is coated with a polyimide cladding 301, and the high-strength sheath 201 is extruded, thereby ensuring the mechanical strength and low-temperature resistance of the temperature sensing optical fiber 300, and making the overall outer diameter of the optical fiber microcable 200 smaller, so as to adapt to the smaller placement space in the superconductor layer 2, the shielding layer 4, the liquid nitrogen layer 7 and the vacuum layer 8. The temperature sensing optical fiber 300 of the optical fiber microcable 200 extends along the axial direction of the superconducting cable and covers the entire length of the superconducting cable. By connecting the temperature sensing optical fiber 300 to the temperature measuring device, temperature monitoring within the entire length range can be achieved. By arranging the optical fiber microcable 200 in any one or more layers of the superconductor layer 2, the shielding layer 4, the liquid nitrogen layer 7 and the vacuum layer 8, the temperature detection of the corresponding cable structure layer can be achieved. To ensure that the optical fiber microcable 200 does not affect the overall performance of the superconducting cable when placed in the above-mentioned cable structure layer, the overall outer diameter of the optical fiber microcable 200 should not be too large, and the arrangement of the optical fiber microcable 200 should be considered to reduce the overall anisotropy.

[0067] Preferably, optical fiber microcables 200 are provided in the superconductor layer 2, the shielding layer 4, the liquid nitrogen layer 7 and the vacuum layer 8, so that on the basis of realizing effective temperature monitoring along the entire length of the superconducting cable, effective real-time monitoring of the temperature of the above-mentioned structural layers of the superconducting cable can be realized at the same time, thereby performing more comprehensive quasi-distributed measurement of the temperature along the superconducting cable, and timely discovering the specific location of operating defects or fault points related to thermal disturbances on the superconducting cable, so as to better monitor the operating status of the superconducting cable and ensure the normal operation and safe operation of the superconducting cable.

[0068] Specifically, in the first embodiment, the superconductor layer 2 includes one or more superconducting tape layers 21, and a third protective layer 93 is provided between adjacent superconducting tape layers 21, and the third protective layer 93 is made of polyimide tape. Each superconducting tape layer 21 is formed by twisting a plurality of superconducting tapes, and the superconducting tape is YBCO (yttrium barium copper oxide), and a gap is formed between two adjacent superconducting tapes, and the optical fiber microcable 200 is laid in the gap between the two adjacent superconducting tapes. The size of the gap between the two adjacent superconducting tapes should not only reduce the pressure on the optical fiber microcable 200, but also ensure the integrity of the superconducting tape layer 21. Preferably, an adhesive is filled between the optical fiber microcable 200 and the gap between the two adjacent superconducting tapes to fix and protect the optical fiber microcable 200, and the adhesive is preferably a polyimide resin. By laying the optical fiber microcable 200 in the gap between two adjacent superconducting tapes in the superconducting tape layer 21, the optical fiber microcable 200 can be placed in the superconductor layer 2 to achieve real-time temperature monitoring along the superconductor layer 2 without affecting the main structure of the superconducting cable.

[0069] The inner insulating layer 3 covers the superconductor layer 2, and the inner insulating layer 3 is made of insulating paper tape. A fourth protective layer 94 is provided between the inner insulating layer 3 and the superconductor layer 2, and the fourth protective layer 94 is made of low-temperature resistant material. In the first embodiment, a second protective layer 92 is provided between the innermost superconducting tape layer 21 of the superconductor layer 2 and the central conductor layer 1, and a fourth protective layer 94 is provided between the inner insulating layer 3 and the outermost superconducting tape layer 21 of the superconductor layer 2.

[0070] The shielding layer 4 includes an inner shielding layer 41 and an outer shielding layer 42. The inner shielding layer 41 covers the inner insulating layer 3, and the inner shielding layer 41 is a superconducting tape shielding layer, and the superconducting tape is YBCO (yttrium barium copper oxide). A fifth protective layer 95 is provided between the inner shielding layer 41 and the inner insulating layer 3, and the fifth protective layer 95 is made of a low-temperature resistant material. The outer shielding layer 42 covers the inner shielding layer 41, and the outer shielding layer 42 is a copper tape shielding layer. A sixth protective layer 96 is provided between the outer shielding layer 42 and the inner shielding layer 41, and the sixth protective layer 96 is made of a low-temperature resistant material. The outer shielding layer 42 is formed by twisting a plurality of copper tapes, and a gap is formed between two adjacent copper tapes, and the optical fiber microcable 200 is laid in the gap between the two adjacent copper tapes. The size of the gap between the two adjacent copper tapes should not only reduce the pressure on the optical fiber microcable 200, but also ensure the integrity of the outer shielding layer 42 to avoid magnetic field leakage. Preferably, the gap between the optical fiber microcable 200 and the two adjacent copper tapes is filled with an adhesive to fix and protect the optical fiber microcable 200. The adhesive is preferably a polyimide resin. By laying the optical fiber microcable 200 in the gap between the two adjacent copper tapes of the outer shielding layer 42, the optical fiber microcable 200 can be placed in the outer shielding layer 42 without affecting the main structure of the superconducting cable and the insulation performance of the superconducting cable to achieve real-time temperature monitoring along the outer shielding layer 42 without being affected by electromagnetic interference.

[0071] The outer insulating layer 5 covers the shielding layer 4, and the outer insulating layer 5 is made of insulating paper tape. A seventh protective layer 97 is provided between the outer insulating layer 5 and the shielding layer 4, and the seventh protective layer 97 is made of low temperature resistant material. In the first embodiment, the seventh protective layer 97 is provided between the outer insulating layer 5 and the outer shielding layer 42 of the shielding layer 4.

[0072] The sheath 6 covers the outer insulating layer 5. The liquid nitrogen layer 7 includes a first corrugated tube 71 spaced outside the sheath 6 and liquid nitrogen 72 filled between the first corrugated tube 71 and the sheath 6. The first corrugated tube 71 is a metal corrugated tube. An optical fiber microcable 200 is arranged in the first corrugated tube 71, thereby realizing that the optical fiber microcable 200 is placed in the liquid nitrogen layer 7 without affecting the main structure of the superconducting cable to realize real-time monitoring of the temperature along the liquid nitrogen layer 7, so as to monitor in real time whether the liquid nitrogen leaks. The optical fiber microcable 200 arranged in the first corrugated tube 71 can be located on the inner surface of the first corrugated tube 71, or in the interval space between the first corrugated tube 71 and the sheath 6, or on the outer surface of the sheath 6.

[0073] The vacuum layer 8 includes a cladding 81 covering the liquid nitrogen layer 7, a second bellows 82 spaced outside the cladding 81, and a vacuum cavity 83 formed between the second bellows 82 and the cladding 81. The cladding 81 covers the first bellows 71. The cladding 81 adopts a reflective tape, and the second bellows 82 adopts a metal bellows. An optical fiber microcable 200 is arranged in the cladding 81 and / or in the second bellows 82, thereby placing the optical fiber microcable 200 in the vacuum layer 8 without affecting the main structure of the superconducting cable to realize real-time temperature monitoring along the vacuum layer 8. Preferably, multiple (e.g., two) optical fiber microcables 200 are arranged in the cladding 81, and a layer of optical fiber microcable 200, a layer of reflective tape, a layer of optical fiber microcable 200, and a layer of reflective tape are sequentially wound on the outer surface of the first corrugated tube 71, and the optical fiber microcable 200 is wrapped in the reflective tape and wound on the first corrugated tube 71 layer by layer to form the cladding 81. The optical fiber microcable 200 in the cladding 81 can form a temperature gradient to accurately measure the temperature of different layers of reflective tape in the cladding 81 in real time; at the same time, the optical fiber microcable 200 is arranged in the second corrugated tube 82. In this way, the optical fiber microcable 200 is placed in the vacuum layer 8 without affecting the main structure of the superconducting cable to realize real-time monitoring of the temperature along the vacuum layer 8, so as to observe whether liquid nitrogen leaks and whether the vacuum environment is destroyed. The optical fiber microcable 200 arranged in the second corrugated tube 82 can be located on the inner surface of the second corrugated tube 82, or in the interval space between the second corrugated tube 82 and the cladding 81, that is, in the vacuum chamber 83, or on the outer surface of the cladding 81.

[0074] Embodiment 2

[0075] like Figures 4 to 5 As shown, it is the second embodiment of the superconducting cable provided by the present invention. The second embodiment is basically the same as the first embodiment, and the similarities are not repeated here. The difference is that in the second embodiment, the cross-sectional shape of the metal conductor single wire 11 constituting the central conductor layer 1 is an arcuate shape and is gradually expanded from the inside to the outside. The arcuate shape refers to the fan shape obtained by cutting two concentric circles by two radii, and multiple arcuate shapes can form a complete circular ring. The conventional central conductor layer 1 copper conductor is a compression type, which is intended to reduce the outer diameter of the twisted central conductor layer 1. When the central optical unit 100 is placed inside the central conductor layer 1, the copper conductor will cause compression damage to the central optical unit 100 during the compression process, causing the central optical unit 100 to be crushed. In the second embodiment, the cross-sectional shape of the metal conductor single wire 11 of the central conductor layer 1 is an arch shape, which can effectively reduce the squeezing of the metal conductor single wire 11 (copper conductor) on the central light unit 100, and can play an arch bridge effect inside the central conductor layer 1 while reducing the area, leaving a space in the center to place the central light unit 100, thereby providing good protection for the central light unit 100.

[0076] Embodiment 3

[0077] Embodiment 3 is the third embodiment of the superconducting cable provided by the present invention. Embodiment 3 is basically the same as Embodiment 1 or Embodiment 2, and the similarities are not repeated here. The difference is that, on the basis of Embodiment 1 or Embodiment 2, this embodiment 3 is also provided with a vibration sensing optical fiber in at least the liquid nitrogen layer 7 and / or the vacuum layer 8. By connecting the vibration sensing optical fiber with the vibration measuring device, the vibration monitoring of the superconducting cable can be realized. The monitoring results of the vibration sensing optical fiber and the temperature sensing optical fiber 300 are mutually verified, and the working conditions in the liquid nitrogen layer 7 and the vacuum layer 8 can be monitored more accurately. The gas leakage amount and positioning can be judged by observing the vibration rate and vibration amplitude. If the temperature sensing optical fiber 300 in the vacuum layer 8 detects an increase in temperature, external leakage occurs, that is, the second corrugated tube 82 of the outer layer is broken; if the temperature sensing optical fiber 300 in the vacuum layer 8 detects a decrease in temperature, internal leakage occurs, that is, the first corrugated tube 71 of the inner layer is broken.

[0078] In the third embodiment, the vibration sensing optical fiber in the liquid nitrogen layer 7 is arranged in the first corrugated tube 71, and the vibration sensing optical fiber in the vacuum layer 8 is arranged in the second corrugated tube 82. In addition, vibration sensing optical fibers may also be arranged in other cable structure layers.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A superconducting cable, characterized in that: The invention comprises a central optical unit (100), a central conductor layer (1) and a superconductor layer (2) which are sequentially arranged in layers from the inside to the outside. The central optical unit (100) comprises a protective tube (101) and a temperature sensing optical fiber (300) passing through the protective tube (101). The central conductor layer (1) is formed by twisting a plurality of metal conductor single wires (11) and covers the protective tube (101). The superconductor layer (2) covers the central conductor layer (1).

2. The superconducting cable according to claim 1, characterized in that: The cross-section of the metal conductor single wire (11) is arched and is gradually expanded from the inside to the outside.

3. The superconducting cable according to claim 1, characterized in that: The protection tube (101) is a stainless steel tube.

4. The superconducting cable according to claim 1, characterized in that: The invention also comprises an inner insulating layer (3), a shielding layer (4), an outer insulating layer (5), a sheath (6), a liquid nitrogen layer (7) and a vacuum layer (8) which are sequentially arranged in layers from the inside to the outside of the superconductor layer (2); an optical fiber microcable (200) is arranged in any one or more layers of the superconductor layer (2), the shielding layer (4), the liquid nitrogen layer (7) and the vacuum layer (8); and the optical fiber microcable (200) comprises a temperature measuring sensing optical fiber (300) and a high-strength protective layer (201) covering the temperature measuring sensing optical fiber (300).

5. The superconducting cable according to claim 1 or 4, characterized in that: The surface of the temperature sensing optical fiber (300) is coated with a polyimide cladding (301).

6. The superconducting cable according to claim 4, characterized in that: The superconductor layer (2) comprises one or more superconducting tape layers (21), each of the superconducting tape layers (21) being formed by twisting a plurality of superconducting tapes and a gap being formed between two adjacent superconducting tapes, and the optical fiber microcable (200) is laid in the gap between the two adjacent superconducting tapes.

7. The superconducting cable according to claim 4, characterized in that: The shielding layer (4) comprises an inner shielding layer (41) covering the inner insulating layer (3) and an outer shielding layer (42) covering the inner shielding layer (41); the inner shielding layer (41) is a superconducting tape shielding layer; the outer shielding layer (42) is a copper tape shielding layer; the outer shielding layer (42) is formed by twisting a plurality of copper tapes together and a gap is formed between two adjacent copper tapes; the optical fiber microcable (200) is laid in the gap between the two adjacent copper tapes.

8. The superconducting cable according to claim 4, characterized in that: The liquid nitrogen layer (7) comprises a first corrugated tube (71) arranged at intervals outside the jacket (6) and liquid nitrogen (72) filled between the first corrugated tube (71) and the jacket (6), and the optical fiber microcable (200) is arranged in the first corrugated tube (71).

9. The superconducting cable according to claim 4, characterized in that: The vacuum layer (8) comprises a cladding (81) covering the liquid nitrogen layer (7), a second corrugated tube (82) spaced outside the cladding (81), and a vacuum cavity (83) formed between the second corrugated tube (82) and the cladding (81); the optical fiber microcable (200) is arranged in the cladding (81) and / or in the second corrugated tube (82).

10. The superconducting cable according to claim 4, characterized in that: At least the liquid nitrogen layer (7) and / or the vacuum layer (8) is provided with a vibration sensing optical fiber.

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