CN108428510B - High current density rectangle heap high temperature superconducting degaussing cable structure - Google Patents
High current density rectangle heap high temperature superconducting degaussing cable structure Download PDFInfo
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- CN108428510B CN108428510B CN201810589665.9A CN201810589665A CN108428510B CN 108428510 B CN108428510 B CN 108428510B CN 201810589665 A CN201810589665 A CN 201810589665A CN 108428510 B CN108428510 B CN 108428510B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B12/00—Superconductive or hyperconductive conductors, cables, or transmission lines
- H01B12/02—Superconductive or hyperconductive conductors, cables, or transmission lines characterised by their form
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
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Abstract
The invention relates to a rectangular stacked high-temperature superconducting degaussing cable structure with high current density and capable of bearing large current, and belongs to the field of high-temperature superconducting degaussing cables. The high-temperature superconducting degaussing cable comprises a core body, an insulating layer, an isolation belt, a liquid nitrogen channel, a low-temperature Dewar pipe and an outer protective sleeve from inside to outside in the radial direction, wherein the core body is formed by stacking superconducting strips. The invention adopts the stacked cable core structure, can further improve the current density of the current-carrying conductor, has smaller weight and volume, simplifies the structure and is easy to produce.
Description
Technical Field
The invention relates to a rectangular stacked high-temperature superconducting degaussing cable structure with high current density and capable of bearing large current, and belongs to the field of high-temperature superconducting degaussing cables.
Background
Newly built and repaired ships and ships using the ships for a certain period need to be demagnetized, so that the ships are defended from being attacked by magnetic weapons (such as magnetic induction mines) in water and discovered by a magnetic detection instrument, and the navigation safety of the ships is guaranteed. There are two methods of demagnetization: (1) and (3) a temporary coil demagnetization method: the method is used for counteracting the inherent magnetic field of the ship and is carried out by a degaussing ship and a degaussing station. The degaussing station or the ship is provided with a degaussing generator set, a degaussing coil, a magnetic field detection device, a control device and the like. Generally, a degaussing cable is wound on a vessel of a degaussed ship according to a rule, and a magnetic field is eliminated by electrifying. The degaussing ship can degausse at sea and is flexible. (2) Fixed winding demagnetization method: the demagnetizing coil is used for compensating the induced magnetic field of the ship and is carried out by a fixed demagnetizing winding laid on the ship. Demagnetization mainly aims at the mine of the magnetic fuse, when a plurality of ships are exploded in the second war and the overtime, the magnetic fuse becomes the common fuse of the mine, and the magnetic fuse can be used in a plurality of composite fuse mines except for the water pressure fuse and the sound fuse. So that warship demagnetization becomes a necessary factory measure, how long degaussing is not clear, which is related to the geomagnetic region in the navigation sea area. The submarine needs to be demagnetized, but the action is not as large as that of a surface ship, because a targeted magnetic anomaly detector can basically detect large steel objects only at a certain underwater depth, the submarine demagnetization can only slightly reduce the detectable depth distance of points, and the action is limited.
The high-temperature superconducting demagnetizing cable can be used for improving the magnetic protection capability of a naval vessel. According to the project engineer of the American water surface operation center, the weight of the wire is reduced and the number of coil turns is reduced by replacing a copper wire with a high-temperature superconducting wire in a degaussing system. High temperature superconducting wire from superconducting corporation of america is capable of carrying 150 times more current than copper wire of the same diameter. For a typical military vessel, such as an LPD17 amphibious landing vessel, a demagnetization system using high temperature superconducting wire is 20% lighter in weight than a demagnetization system using copper wire, which not only reduces the system weight, but also reduces the installation cost. The degaussing cable system will be used in vessels used in the world. The high temperature superconducting degaussing cable uses high temperature superconducting wire from superconducting corporation in the United states, and the total length reaches 142 feet. The degaussing cable can deliver 4100 amps of current, which is a level typical of conventional copper degaussing wires used in naval vessels, but the voltage can be less than 0.5 volts, or 1000 times lower than copper wires. And most importantly, the weight of the high-temperature superconducting degaussing cable is only 20 percent of that of the common copper wire degaussing cable. Therefore, the weight and volume advantages of the high-temperature superconducting demagnetizing cable are expected to reduce the installation cost of the high-temperature superconducting demagnetizing cable and a copper wire-based demagnetizing system by 40%. In addition, due to the zero resistance characteristic of the high-temperature superconducting wire, only a small amount of energy is needed to operate the high-temperature superconducting degaussing system. The american superconducting company claims that the company successfully validated the first full-size superconductor-based degaussing cable worldwide. The naval vessels mostly adopt demagnetizing cables to reduce the characteristics of magnetic signals, so that the vessels are not easy to be found, and especially the threat of magnetic induction mines is avoided. The length of the high-temperature superconducting degaussing cable used for verification is 40 meters, in an experiment, the cable passes 4100 amperes of current, which is a typical value of the conventional shipborne copper degaussing cable, but the working voltage is obviously reduced, and the voltage of 0.5 volt is only one thousandth of the working voltage of the copper cable.
Patent CN 102855982A discloses a shielding type longitudinal watertight degaussing cable for ships and warships and a manufacturing method thereof in the field of degaussing cables, wherein tinned copper wires are stranded into stranded copper conductors after being impregnated with sealant, a conductor sealant layer is impregnated on the peripheries of the stranded copper conductors, insulating rubber layers are wrapped on the peripheries of the conductor sealant layers in an extruding mode to form insulating core wires, gaps among the insulating core wires are filled with chloroprene rubber filling strips, a plurality of insulating core wires are integrally stranded into a cable core, and the peripheries of the cable core are sequentially provided with a cable core inner sealant layer, an inner sheath rubber layer, an armored shielding layer and an outer sheath rubber layer. The cable conductor monofilament is impregnated with the sealant, the periphery of the stranded copper conductor is impregnated with the conductor sealing glue layer, the periphery of the cable core is extruded with the sealant layer in the cable core to form multiple sealing, the chloroprene rubber filling strip expands during subsequent vulcanization to completely fill the gap in the cable core, and the insulating core wire are not tangent to each other, so that when the cable core is extruded with the inner sealing glue layer, the sealant can penetrate into the cable core, and the watertight effect is ensured. Patent CN 102751017A discloses a warship enhanced tensile type longitudinal watertight degaussing cable and a manufacturing method thereof in the field of degaussing cables, a plurality of tinned copper wires are stranded into a stranded copper conductor after being impregnated with sealant, a conductor sealing glue layer is impregnated on the periphery of the stranded copper conductor, an insulating rubber layer is extruded on the periphery of the conductor sealing glue layer to form insulating core wires, a gap between every two insulating core wires is filled with a chloroprene rubber filling strip and a plurality of insulating core wires are integrally stranded into a cable core, a cable core sealing glue layer is extruded on the periphery of the cable core, and a sheath rubber layer is extruded on the periphery of the cable core sealing glue layer. The cable conductor monofilament is impregnated with the sealant, the periphery of the stranded copper conductor is impregnated with the conductor sealant layer, the periphery of the cable core is extruded with the cable core sealant layer, multiple sealing is formed, the chloroprene rubber filling strip expands to completely fill a gap in the cable core during subsequent vulcanization, and the insulating core wire are not tangent to each other, so that when the cable core sealant layer is extruded, the sealant can permeate into the cable core, and the watertight effect is ensured. Patent CN 102751020A discloses a longitudinal watertight degaussing cable for ships and a manufacturing method thereof in the field of degaussing cables, a plurality of tinned copper wires are stranded into a stranded copper conductor after being soaked in sealant, a conductor sealant layer is soaked at the periphery of the stranded copper conductor, an insulating rubber layer is extruded at the periphery of the conductor sealant layer to form insulating core wires, a gap between every two insulating core wires is filled with a chloroprene rubber filling strip, the plurality of insulating core wires are integrally stranded into a cable core, a cable core sealant layer is extruded at the periphery of the cable core, and a sheath rubber layer is extruded at the periphery of the cable core sealant layer. This cable conductor monofilament flooding sealant, transposition copper conductor periphery flooding has the conductor sealant, and the periphery of cable core is crowded to be wrapped up with the cable core sealant, has formed multiple sealing, and the chloroprene rubber packing strip inflation can fill the gap in the cable core completely when follow-up vulcanization to can cause no longer tangent between insulating heart yearn and the insulating heart yearn, thereby when making crowded package cable core sealant, inside the sealed glue can permeate into the cable core, guarantee the watertight effect. Patent CN 105469888A discloses a coaxial degaussing cable with a two-conductor structure in the field of degaussing cables, which comprises an inner conductor, a rubber insulating layer, an outer conductor, a rubber isolating layer and an outer sheath from inside to outside; the inner conductor is formed by twisting a bearing core positioned in the center of the inner conductor and a plurality of aluminum alloy conductors which surround the reinforcing core by taking the bearing core as the center of a circle; the outer conductor is formed by combining four reinforcing cores which are symmetrical by the center of the cable and a plurality of copper conductors; a plastic hose is arranged between the rubber isolation layer and the outer sheath; the outer sheath is also provided with a temperature sensing alarm, the height of the temperature sensing alarm is not more than 0.3mm, and the width of the temperature sensing alarm is not more than 0.8 mm; the plastic hose is provided with four convex grooves, and the outer sheath is provided with four grooves corresponding to the convex grooves. The cable has the advantages of self-bearing and compression resistance, good moisture resistance and sealing performance, good flexibility, small attenuation and good shielding effect, and can play a role in monitoring the temperature of the cable. Patent CN 105469888A discloses a laying device and a laying method for degaussing cable trough and marine cable in the field of degaussing cable, relating to the technical field of cable laying. Degaussing cable tray includes: the cable trough body is rectangular in section and is open at the top; the cover plate covers the opening at the top of the cable trough body; and the cable fastening hook is fixed in the cable groove body, the cable fastening hook comprises a U-shaped support formed by two vertical rods and a bottom rod and two lifting rods which are parallel relatively, two grooves are respectively arranged on the inner side of each lifting rod and correspond to the outer side ends of the two vertical rods, and the two lifting rods are connected through a fastening piece. The laying device of the ship cable is formed by connecting a plurality of degaussing cable grooves, and two adjacent degaussing cable grooves are connected through a sleeve. The cable laying method is implemented by using a laying device for a ship cable. According to the invention, the cable is laid in the cable groove body, so that the cable laying work of constructors can be greatly facilitated, and the scraping damage to the cable is reduced.
The degaussing cables disclosed above and existing degaussing cables are mostly based on metal materials, such as copper-aluminum cables, and they are wound by using a resistive cable core, so that they have large volume weight and resistance loss, and require a higher power supply. The high-temperature superconducting cable is formed by winding a superconducting material with high current density and zero resistance loss, and the demagnetizing cable based on the high-temperature superconducting cable has the advantages of small volume, light weight, low loss, low power of a matched power supply and the like.
Patent CN 101069247a discloses a superconducting cable capable of absorbing the amount of shrinkage of a superconducting wire element in cooling with a simple structure. The superconducting cable according to the present invention includes: a superconducting wire element in which superconducting layers (a conductor layer (13) and a return pipe conductor (17)) are formed by spiral winding; stress relaxation layers (an inner stress relaxation layer (12), an insulating layer/an outer stress relaxation layer (16)) provided on the inner side of the superconducting layer; and a cable constituent member (a molding (11)) provided on the inner side of the stress relaxation layer. The cable is configured such that the amount of contraction in the radial direction of the superconducting layer of the refrigerant-cooled superconducting element is absorbed by the stress relaxation layer. Patent CN 101142637a mentions that the invention provides a superconducting cable with further reduced cable diameter and a DC transmission system including the superconducting cable. A superconducting cable (1) has a structure in which two cable cores (2) each having a superconducting conductor layer (4) and an outer superconducting layer (6) both made of a superconducting material are stranded together and housed in a thermal insulation pipe (8). Each cable core (2) has, in order from the center, a former (3), a superconducting conductor layer (4), an insulating layer (5), an outer superconducting layer (6), and a protective layer (7). In unipolar transmission, the superconducting conductor layers (4) of the two cores (2) are used as outgoing lines carrying unipolar currents, and the outer superconducting layers (6) of the two cores (2) are used as return lines carrying return currents. In bipolar transmission, the superconducting conductor layer (4) of one core (2) is used as positive transmission, the superconducting conductor layer (4) of the other core (2) is used as negative transmission, and the outer superconducting layers (6) of the two cores (2) are used as neutral layers. Patent CN 102859613a the present invention discloses a superconducting cable having low material cost and good voltage resistance, which is capable of suppressing dielectric loss. Specifically disclosed is a direct current superconducting cable (10) having an insulating layer (5) on the outer periphery of a conductor, and characterized in that: the insulating layer (5) is formed by a first insulating layer (5a), a second insulating layer (5b) and a third insulating layer (5c) in sequence from the inner layer to the outer layer; the insulating layer (5) is impregnated with liquid nitrogen; the product of the dielectric constant ε 1 and the dielectric loss tangent tan δ 1 of the first insulating layer (5a) and the product of the dielectric constant ε 2 and the dielectric loss tangent tan δ 2 of the second insulating layer (5b) satisfy the relationship of ε 1 × tan δ 1> ε 2 × tan δ 2; and the product of the dielectric constant ε 2 of the second insulating layer (5b) and the dielectric loss tangent tan δ 2 and the product of the dielectric constant ε 3 of the third insulating layer (5c) and the dielectric loss tangent tan δ 3 satisfy the relationship of ε 2 × tan δ 2< ε 3 × tan δ 3. The invention of patent CN 103177815 a relates to a three-axis superconducting cable. The triaxial superconducting cable includes: a cryostat having an inner cryostat and an outer cryostat coaxially disposed with a space interposed therebetween; and a single core disposed in an inner cryostat of the cryostat with a space interposed therebetween, wherein a winding former is disposed at a center of the core, a superconducting conductive layer having each phase is coaxially disposed at an outer periphery of the winding former at an outer side in a radial direction with an insulating layer interposed therebetween, and the insulating layer is coaxially disposed at an outer periphery of an outermost superconducting conductive layer, wherein an outer cryostat of the cryostat is made of an aluminum material and configured to be electrically connected to a neutral line of a neutral electrode (N-pole) at a superconducting cable system. Patent CN 106716558A proposes a superconducting cable characterized in that the diameter (cross-sectional area) or weight of the former can be reduced by increasing the physical strength of the superconducting wire and further diversifying the path of the fault current.
Most of the above-disclosed or conventional high-temperature superconducting cable structures are three-phase coaxial and three-phase concentric superconducting cable structures, and have a skeleton structure of a copper core or a hollow corrugated tube. Compared with a three-phase coaxial and three-phase concentric superconducting cable structure, the stacked high-temperature superconducting cable core structure omits a copper core or a skeleton structure of a hollow corrugated pipe, can further improve the current density of the superconducting cable core, has smaller weight and volume, simplifies the structure and is easy to produce. The stacked structure can enhance the mechanical strength of the high-temperature superconducting tape, particularly the YBCO coating conductor along the C-axis direction. And the existing superconducting cable needs a narrow band to be wound, and the stacked high-temperature superconducting cable can be wound by adopting a wide band, so that the division of the wide band is avoided, and the current-carrying density of the core cable can be further improved.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a rectangular stacked high temperature superconducting degaussing cable structure with high current density, wherein the core current-carrying material of the degaussing cable is a high temperature superconducting tape capable of carrying a large current, so as to increase the power density, and the current density of the current-carrying conductor can be further increased by using the stacked cable core structure. As a degaussing cable for ships, the degaussing cable has good bending property and underwater sealing property.
The purpose of the invention is realized by the following technical scheme:
a high current density rectangle stack type high temperature superconducting degaussing cable structure, the high temperature superconducting degaussing cable is respectively a core body, an insulating layer, an isolation belt, a liquid nitrogen channel, a low temperature Dewar pipe and an outer protective sleeve from inside to outside along the radial direction; wherein:
the core is obtained by stacking n layers of superconducting tapes into a stacked superconductor with a rectangular cross section and twisting the stacked superconductor;
the insulating layer adopts polyimide film, polypropylene laminated paper, cellulose paper or oil-immersed cable paper aramid fiber paper;
the isolation belt is a nylon or fluoroplastic winding pipe, and the nylon or fluoroplastic winding pipe is wound on the outer side of the insulation layer;
the low-temperature Dewar pipe is provided with an inner corrugated pipe and an outer corrugated pipe from inside to outside along the radial direction, two ends of the inner corrugated pipe and the outer corrugated pipe are welded and connected with one end of a stainless steel straight pipe, the inner corrugated pipe, the outer corrugated pipe and the stainless steel straight pipe form a flexible pipeline with a middle interlayer, and the other end of the stainless steel straight pipe is welded with a knife edge flange and connected with a terminal;
and a liquid nitrogen channel is arranged between the low-temperature Dewar pipe and the isolation belt, and an outer protective sleeve is arranged on the outer side of the low-temperature Dewar pipe.
Furthermore, the core body adopts a superconducting tape coated by copper, copper alloy or stainless steel, the thickness of the superconducting tape is not more than 0.3mm, the width of the superconducting tape is not more than 20mm, and the critical current of the superconducting tape is not less than 100A.
Further, the insulating layer has two kinds of wrapping modes: each superconducting strip is wrapped in an insulating mode and then bundled and fixed to form a bundle of core bodies; or all the superconducting strips are directly bundled and fixed into a bundle of cores by using insulating wrapping tapes.
Furthermore, in the low-temperature dewar pipe, the length of outer bellows is greater than the length of inner bellows, the intermediate layer is the vacuum intermediate layer, and the both ends of intermediate layer are equipped with the vacuum pump nozzle respectively, be equipped with thermal insulation material in the vacuum intermediate layer.
Specifically, the heat insulation structure of the Dewar pipe can be accumulation heat insulation, the interlayer is filled with accumulation materials, the selected accumulation materials are expanded perlite, pearlife, aerogel, superfine glass wool or polystyrene foam plastics, and the accumulation materials are filled with gas with the condensation temperature lower than the surface temperature of the inner corrugated pipe;
or the heat insulation structure of the Dewar pipe is high vacuum heat insulation, and the vacuum degree of the intermediate interlayer is lower than 1.3 multiplied by 10- 3Pa, the inner wall surface of the intermediate interlayer is made of copper or aluminum and is subjected to smooth finish treatment;
or the heat insulation structure of the Dewar pipe is vacuum porous heat insulation, the middle interlayer is filled with porous heat insulation materials, the middle interlayer is pumped to low vacuum of 1-10Pa, and the selected porous heat insulation materials are aerogel, vermiculite, pearly-lustre sand or microsphere heat insulation materials;
or the heat insulation structure of the Dewar pipe is high vacuum multi-layer heat insulation, and a plurality of layers of metal foils are wrapped in the interlayer.
Furthermore, the twisted stacked superconductors are formed and fixed through winding of copper wires, and flexible gaskets are used at the joints of the copper wires and the stacked superconductors to disperse stress generated by fixing of the copper wires.
Further, the core body comprises a superconducting layer and a quench protection layer, and the superconducting layer and the quench protection layer are radially arranged along the core body or radially arranged in a layered and alternate manner along the core body; the superconducting layer adopts a superconducting tape, and the quench protection layer adopts a red copper flexible wire.
Furthermore, a quench protection layer is arranged between adjacent superconducting tapes in the stacked superconductor.
Furthermore, a winding protective layer which is contacted with the superconducting layer is wound on the surface of the quenching protective layer, and the winding protective layer is made of materials which are soft in texture and cannot be brittle at low temperature, such as polyimide films and cotton tapes.
The high-temperature superconducting degaussing cable is formed by winding a superconducting material with high current density and zero resistance loss, and has the advantages of small volume, light weight, low loss, low power required to be matched with a power supply and the like. Compared with the structure of a three-phase coaxial and three-phase concentric superconducting cable, the high-temperature superconducting degaussing cable saves a copper core or a skeleton structure of a hollow corrugated pipe, can further improve the current density of a superconducting cable core body, has smaller weight and volume, simplifies the structure and is easy to produce. The stacked core body can be wound by adopting a wide band, so that the wide band is prevented from being cut, and the current-carrying density of the core cable can be further improved. Meanwhile, the mechanical strength of the high-temperature superconducting tape, particularly the YBCO coating conductor, along the C-axis direction can be enhanced by adopting the stacked type.
Drawings
FIG. 1 is a schematic view of a low temperature Dewar configuration;
FIG. 2 is a schematic diagram of a liquid nitrogen circulation system;
FIG. 3a is a schematic diagram of a stacked superconductor structure with a rectangular cross-section;
FIG. 3b is a cross-sectional view of a stacked superconductor with a rectangular cross-section;
FIG. 4 is a schematic view of a radial cross-sectional structure of the superconducting degaussing cable according to the present invention;
the device comprises an inner corrugated pipe 1, an outer corrugated pipe 2, a stainless steel straight pipe 3, a vacuum suction nozzle 4, an intermediate interlayer 5, a superconductive degaussing cable 6, a liquid nitrogen pump 7, a low-temperature valve 8, a liquid nitrogen storage tank 9, a core body 10, an insulating layer 11, a liquid nitrogen channel 12 and an outer protective sleeve 13.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
A high current density stacked high temperature superconducting degaussing cable structure, as shown in fig. 4, the high temperature superconducting degaussing cable comprises a core 10, an insulating layer 11, a separation belt, a liquid nitrogen passage 12, a low temperature dewar pipe and an outer protective sleeve 13 from inside to outside along the radial direction, wherein:
the core body is a core component for bearing current of the high-temperature superconducting degaussing cable and is formed by stacking copper, copper alloy or stainless steel-coated superconducting strips, wherein the thickness of the copper is not more than 0.3mm, the width of the copper is not more than 20mm, and the critical current of the copper is not less than 100A.
Determining the size and the direction of a magnetic field on the core of the high-temperature superconducting demagnetizing cable according to the size and the direction of the running current of the core by utilizing the characteristic that the critical current Ic of the superconducting tape changes along with the magnetic field, and further determining the critical current of the core; and according to the critical current and the operation margin of the core, performing iterative calculation on the operation current of the core and the magnetic field on the core to obtain the optimal operation current of the core, and finally determining the number of the superconducting tapes.
As shown in FIGS. 3a and 3b, the core is obtained by stacking n layers of superconducting tapes with width w and thickness d in parallel into a stacked superconductor with a rectangular cross section, and twisting the stacked superconductors, wherein nd is close to or equal to w. The twisting is constrained by comprehensive experimental values considering twisting stress of the superconducting tapes in the tangential direction and bending diameter of the core body along the length direction. And the twisted stacked superconductors are wound by copper wires to be molded and fixed, and flexible gaskets are used at the joints of the copper wires and the stacked superconductors to disperse the stress generated by fixing the copper wires. The copper wire is fixed and wound by a plurality of turns so as to form the copper wire. After the core body is twisted, not only can the interference of a part of electromagnetic waves from the outside be resisted, but also the mutual interference among the superconducting tapes can be reduced.
The stacked superconductor omits a copper core or a skeleton structure of a hollow corrugated pipe, can further improve the current density of the core body of the superconducting cable, and has smaller weight and volume. Between the stacked superconducting tapes, the degree of delocalization of electrons at the interface is increased, which leads to an increase in the density of electron states near the fermi surface, thereby enhancing the superconducting properties. And the stackable core body is wound by nylon or fluoroplastic to be used as an isolation belt, so that the current-carrying density of the core cable can be further improved.
The insulating layer is used for electrical insulation and bundling fixation in the high-temperature superconducting degaussing cable. The insulating layer has two kinds of package ways around to the core: each superconducting strip is wrapped in an insulating mode and then bundled and fixed to form a bundle of core bodies; or all the superconducting strips are directly bundled and fixed into a bundle of cores by using insulating wrapping tapes. The insulating layer is in a liquid nitrogen environment, a low-temperature-resistant electric insulating material with good compatibility with liquid nitrogen is adopted, and the insulating layer is made of a low-temperature insulating material, mainly polyimide film (PI), polypropylene laminated paper (PPLP), cellulose paper or oil-immersed cable paper aramid fiber paper (Nomex) and the like.
The insulating layer can be selected from polyimide films: polyimide (PI) has excellent physical and chemical properties and heat resistance, has good thermal stability, can keep a good running state within a range of 269 ℃ below zero to 400 ℃, can resist almost all organic solvents and acids, and has the characteristics of good wear resistance, arc resistance and the like. This makes PI thin films the most used thin film material in high temperature superconducting electrical insulation materials. PI film on LN2The ac breakdown field strength at this time was 279kV/mm with a weibull probability value equal to 62%. When the PI film is used for turn-to-turn insulation and the wrapping number is not more than 3, the PI film is on LN2The breakdown field strength of the alternating current and the direct current increases with the number of the winding packages. The PI film has the characteristic of partial discharge under liquid nitrogen, the occurrence of partial discharge can be inhibited at low temperature, the initial voltage of the partial discharge under the liquid nitrogen is two times higher than that under normal temperature, and the partial discharge is enhanced along with the increase of internal defects.
The insulating layer can be selected from polypropylene laminated paper: the polypropylene laminated paper (PPLP) is an insulating paper formed by pressing a porous paper pulp material and a polypropylene film, and has a three-layer structure, wherein the outer two layers are wood fiber paper, the inner layer is polypropylene, the material cost is lower than that of PI, and the PPLP has good impregnation performance, good mechanical performance and high electrical strength at low temperature.
The insulation layer may be chosen from cellulose papers, which are commonly used in low temperature insulation tests and are typically Kraft papers. Cellulose paper has better impregnation property, at 77K LN2The dielectric constant was 2.21 and the dielectric loss tangent was 0.14 under the immersion condition of 1 atm. Electrical strength of impregnated cellulose paper composite insulation with LN2The increase in pressure is non-linearly increasing. At 77K, the ac breakdown field strength saturates when the pressure reaches 8 atmospheres. The AC breakdown field strength of Kraft paper at room temperature is 9.84kV/mm, which is in LN2Is as followsThe AC breakdown field strength was 74kV/m at a Weibull probability value of 63.2%, which is 7.5 times that at room temperature, and Kraft paper was in LN2The DC breakdown field intensity is about 2 times higher than the AC breakdown field intensity, similar to the experimental result in the air, when the Kraft paper is used for turn-to-turn insulation and the wrapping number is not more than 3, the Kraft paper increases in LN along with the increase of the wrapping number2The breakdown field strength of the direct current is increased from 10kV to 25kV, which is 1.1-1.5 times of the breakdown field strength of the alternating current.
The insulating layer can be selected from oil-immersed cable paper polyaramide fiber paper, wherein the oil-immersed cable paper polyaramide fiber paper (Nomex) is synthetic aromatic amide polymer insulating paper and has good flexibility, low-temperature electrical property and mechanical property. Nomex paper on LN2The dc breakdown field strength is about 2 times higher than the ac breakdown field strength, similar to the experimental results in air. When Nomex is used for turn-to-turn insulation and the wrapping number is less than 3, the Nomex is on LN2The breakdown field strength of the alternating current and the direct current increases with the number of the winding packages.
For a single core cable, the insulation thickness can be calculated according to the following formula:
wherein: u is voltage which is 2.6-3.3 times of rated voltage of the superconducting demagnetization cable; the impact test is considered and can be selected according to the protection level. E is the corresponding power frequency breakdown field strength or impact breakdown strength, m is the safety margin corresponding to the power frequency and the impact voltage, and 1.2-1.65 is selected; rcIs the core radius, R is the insulation layer outer radius, R-RcI.e. the thickness of the insulating layer.
After the thickness of the insulating layer is determined, the winding structure of the insulating layer needs to be determined, and the insulating layer is formed by winding a plurality of layers of insulating materials, so that the manufacturing is convenient, the curvature of a cable can be ensured, the weak points in the insulating paper tape are dispersed, the uniformity of the insulating layer is increased, the breakdown strength of the insulating layer is improved, and the dispersity of the breakdown strength of the insulating layer is reduced. The winding method of the insulating layer comprises a lap-cap type winding method and a gap type winding method. The lap-type cable is lower in flexibility and winding tightness than a gap type cable, so that the lap-type cable is only used for abutting against the outermost layers of the cable core and the insulating layer, the surface can be smooth, and the size of a gap can be reduced.
After the insulating layer is wound, the defect eliminating treatment is carried out. The presence of moisture in the insulation layer significantly reduces the dielectric and ageing properties of the impregnated insulation layer, so that the cable insulation layer must be dried. The thickness and gas impermeability of the insulation material have a significant effect on the impulse breakdown strength, and therefore reducing the thickness of the insulation material, increasing the gas impermeability of the insulation material, increases the impact breakdown field strength of the impregnated insulation material. The gaps between the insulating material layers are overlapped, so that the impact breakdown field strength of the impregnated insulating material can be greatly reduced, the power frequency breakdown strength of the impregnated insulating material can be reduced, and the overlapping number of the gaps is strictly limited. In addition, it is considered that, when a high voltage is applied, a partial discharge occurs between the gaps due to the difference in dielectric constants between liquid nitrogen and the insulating material, and this is one of the main causes of deterioration in withstand voltage. Therefore, the insulating layer should avoid partial discharge, and maintain stability of operation for a longer time.
Under the actual operation condition, the superconducting cable is subjected to axial cold shrinkage and contact force between adjacent superconducting tapes, and the superconducting tapes are required to apply proper radial force in the winding process to prevent loosening, and can generate radial compressive force on the superconducting tapes under the action of an insulating layer protection layer and the like. The external loads can cause the performance degradation of the superconducting tape, and the mechanical characteristic analysis is carried out on the superconducting cable to ensure the safe operation of the core body of the degaussing cable.
The isolation belt is a nylon or fluoroplastic winding pipe which is wound on the outer side of the insulating layer and is used for physically isolating and protecting the core body and the insulating layer.
The core body wound with the insulating layer and the isolation belt is integrated inside the low-temperature Dewar pipe, a liquid nitrogen channel is reserved between the low-temperature Dewar pipe and the isolation belt, and an outer protective sleeve is arranged on the outer side of the low-temperature Dewar pipe. The low-temperature Dewar pipe is located the outside of median, and its effect is for holding cryogenic cooling medium, is the liquid nitrogen passageway between median and the Dewar pipe. The design of the low-temperature Dewar pipe is firstly based on the design of a core body of the degaussing cable, and the low-temperature Dewar pipe is in high connection with the core body, so that the economy of the low-temperature Dewar pipe is realized on the basis of ensuring the good integration of the core body and the low-temperature Dewar pipe; secondly, an important link in the design of the Dewar pipe is the size of heat loss of the Dewar pipe, the structure of the Dewar pipe needs to be optimized, and the heat loss of the Dewar pipe is realized in a more reasonable range by an effective method, so that the requirement of the superconducting degaussing cable on low-temperature refrigerating capacity can be reduced; thirdly, in consideration of light weight, the low-temperature dewar tube is an important component of the overall weight of the degaussing cable, and the structure of the degaussing cable needs to be optimized to reduce the weight; finally, in the structural design and manufacturing process of the dewar tube, the material used by the low-temperature dewar tube and the selection of the material need to be considered from the perspective of meeting the market demand, and the processing and manufacturing cost of the low-temperature dewar tube needs to be reduced as much as possible.
As shown in figure 1, the low-temperature Dewar pipe is provided with an inner corrugated pipe 1 and an outer corrugated pipe 2 from inside to outside along the radial direction respectively, two ends of the inner corrugated pipe 1 and the outer corrugated pipe 2 are welded with one end of a stainless steel straight pipe 3, the inner corrugated pipe 1, the outer corrugated pipe 2 and the stainless steel straight pipe 3 form a flexible pipeline with a middle interlayer 5, and the other end of the stainless steel straight pipe 3 is welded with a knife edge flange and connected with a terminal.
In the low-temperature Dewar pipe, the length of outer bellows is greater than the length of inner bellows, the intermediate layer is the vacuum intermediate layer, and the both ends of intermediate layer are equipped with the vacuum suction nozzle respectively, be equipped with thermal insulation material in the vacuum intermediate layer.
The Dewar pipe comprehensively considers heat transfer ways such as convection, conduction and radiation, reduces the transfer of heat from room temperature to the inner pipe as much as possible, and improves the heat insulation effect.
The heat insulation structure of the Dewar pipe can be selected from stacking heat insulation, which is non-vacuum heat insulation, and solid heat conduction and gas heat conduction account for about 90% of the heat flow of the heat insulation structure. To reduce solid heat conduction, a bulk material with low density, such as expanded perlite (pearlite), aerogel, ultra-fine glass wool, polystyrene, foam plastic and the like, is usually selected. In order to prevent the deterioration of the heat insulating property due to the condensation of the gas in the heat insulating material, the packing material is filled with a gas having a condensation temperature lower than the surface temperature of the inner bellows, such as hydrogen or helium. The heat insulation structure has the advantages of simple manufacturing process, low cost and the like, but has the fatal defects of poor heat insulation performance, thick heat insulation layer and the like, and is rarely adopted in high-temperature superconducting cables.
The heat insulation structure of the Dewar pipe can select high vacuum heat insulation which is simple vacuum heat insulation, and the vacuum degree of the heat insulation interlayer is lower than 1.3 multiplied by 10 to achieve good heat insulation effect-3Pa. The radiation heat loss is the main heat loss source of the structure, and in order to reduce the radiation heat loss, the high vacuum wall surface is usually made of copper, aluminum and other materials with low emissivity and is smooth. The simple vacuum heat insulation has the advantages of simple and compact structure, small heat capacity, convenient manufacture and the like, and has the defects of limited reduction degree of radiation heat loss, large heat loss and frequent maintenance for the superconducting cable applied in long-term engineering.
The heat insulation structure of the Dewar pipe can be vacuum porous heat insulation, the heat insulation mode is that porous heat insulation materials are filled in a heat insulation space, then the heat insulation space is pumped to low vacuum of 1-10Pa, and the common porous heat insulation materials comprise aerogel, vermiculite, pearly-lustre sand, microsphere heat insulation materials and the like. The vacuum degree required by vacuum porous heat insulation is low, the heat insulation performance is 2 orders of magnitude better than the accumulation heat insulation performance and 1 order of magnitude better than the high vacuum heat insulation performance, but the vacuum porous heat insulation structure has the defects of large interlayer spacing, complex and heavy structure and the like.
The heat insulation structure of the dewar pipe can select high vacuum multilayer heat insulation, the heat insulation mode is a high heat insulation structure which greatly reduces radiation heat loss by wrapping a plurality of layers of metal foils (such as aluminum foil and the like) in a heat insulation space, the high heat insulation structure is a heat insulation structure with the best heat insulation effect at present, is also called super heat insulation, and is also a heat insulation mode which is most widely applied at present.
The cooling medium liquid nitrogen circulates in the low-temperature Dewar pipe to provide a cooled low-temperature environment for the high-temperature superconducting degaussing cable, and the liquid nitrogen circulating system can meet several technical requirements: reliability: the liquid nitrogen circulating system has reliability, and the fault possibility in operation is reduced to the minimum; and (3) operation control: in the liquid nitrogen circulation process, the temperature and the flow of the liquid nitrogen are effectively controlled, and the stable operation of the high-temperature superconducting degaussing cable is met; and (4) maintenance and inspection: the liquid nitrogen circulating system pipeline is checked regularly, so that the safety is ensured, and liquid nitrogen leakage accidents caused by factors such as pipeline aging are eliminated; the economic efficiency is as follows: the liquid nitrogen circulating system meets the economic requirement on the basis of meeting the operation requirement. When the liquid nitrogen circulating system operates, the above operation principle must be ensured to ensure the stable and safe operation of the high-temperature superconducting degaussing cable. Figure 2 shows a liquid nitrogen circulation system.
Preferably, the core includes a superconducting layer and a quench protection layer. The superconducting layer and the quench protection layer are arranged along the radial direction of the core body; or along the radial direction of the core body, the superconducting layers and the quench protection layers are arranged in a layered and alternate mode; or in the stacked superconductors, the quench protection layers are arranged between the adjacent superconducting tapes. When the superconducting tape is in current-carrying operation, once the superconducting tape is quenched, the through-current capacity of the cable is instantly and greatly reduced, and even the superconducting tape is melted. The quench protection layer is used for sharing a part of current under the condition that the superconducting strip is quenched, protecting the core body from being damaged, and generally adopting a red copper flexible wire with higher current capacity. The surface of the quench protection layer is required to be wound with a protection layer as a winding surface at the joint with the superconducting layer, and a material which is soft in texture and cannot be brittle at low temperature is selected.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A high current density rectangle stack type high temperature superconducting degaussing cable structure is characterized in that the high temperature superconducting degaussing cable is respectively provided with a core body, an insulating layer, an isolation belt, a liquid nitrogen channel, a low temperature dewar pipe and an outer protective sleeve from inside to outside along the radial direction; wherein:
the core is obtained by stacking n layers of superconducting tapes into a stacked superconductor with a rectangular cross section and twisting the stacked superconductor; the twisted stacked superconductors are wound by copper wires to be molded and fixed, and flexible gaskets are used at the joints of the copper wires and the stacked superconductors;
the core body comprises a superconducting layer and a quench protection layer, and the superconducting layer and the quench protection layer are arranged along the radial direction of the core body or are arranged in a layered and alternate manner along the radial direction of the core body; the superconducting layer adopts a superconducting tape, and the quench protection layer adopts a red copper flexible wire; a winding protective layer which is contacted with the superconducting layer is wound on the surface of the quenching protective layer, and the winding protective layer is a polyimide film or a cotton tape;
the insulating layer adopts polyimide film, cellulose paper or oil-immersed cable paper aramid fiber paper;
the isolation belt is a nylon or fluoroplastic winding pipe, and the nylon or fluoroplastic winding pipe is wound on the outer side of the insulation layer;
the low-temperature Dewar pipe is provided with an inner corrugated pipe and an outer corrugated pipe from inside to outside along the radial direction, two ends of the inner corrugated pipe and the outer corrugated pipe are welded and connected with one end of a stainless steel straight pipe, the inner corrugated pipe, the outer corrugated pipe and the stainless steel straight pipe form a flexible pipeline with a middle interlayer, and the other end of the stainless steel straight pipe is welded with a knife edge flange and connected with a terminal;
in the low-temperature Dewar pipe, the length of the outer corrugated pipe is greater than that of the inner corrugated pipe, the middle interlayer is a vacuum interlayer, two ends of the middle interlayer are respectively provided with a vacuum pumping nozzle, and a heat insulating material is arranged in the vacuum interlayer;
the heat insulation structure of the Dewar pipe is accumulation heat insulation, the middle interlayer is filled with accumulation materials, the selected accumulation materials are expanded perlite, pearlife, aerogel, superfine glass wool or polystyrene foam plastics, and the accumulation materials are filled with gas with the condensing temperature lower than the surface temperature of the inner corrugated pipe;
or the heat insulation structure of the Dewar pipe is high vacuum heat insulation, and the vacuum degree of the intermediate interlayer is lower than 1.3 multiplied by 10-3Pa, the inner wall surface of the intermediate interlayer is made of copper or aluminum and is subjected to smooth finish treatment;
or the heat insulation structure of the Dewar pipe is vacuum porous heat insulation, the middle interlayer is filled with porous heat insulation materials, the middle interlayer is pumped to low vacuum of 1-10Pa, and the selected porous heat insulation materials are aerogel, vermiculite, pearly-lustre sand or microsphere heat insulation materials;
or the heat insulation structure of the Dewar pipe is high vacuum multi-layer heat insulation, and a plurality of layers of metal foils are wrapped in the intermediate interlayer;
and a liquid nitrogen channel is arranged between the low-temperature Dewar pipe and the isolation belt, and an outer protective sleeve is arranged on the outer side of the low-temperature Dewar pipe.
2. The rectangular stacked high temperature superconducting degaussing cable structure with high current density according to claim 1, wherein the core is made of a superconducting tape coated with copper, copper alloy or stainless steel with a thickness of not more than 0.3mm, a width of not more than 20mm and a critical current of not less than 100A.
3. The rectangular stacked high temperature superconducting degaussing cable structure with high current density of claim 1, wherein the insulation layer has two wrapping modes: each superconducting strip is wrapped in an insulating mode and then bundled and fixed to form a bundle of core bodies; or all the superconducting strips are directly bundled and fixed into a bundle of cores by using insulating wrapping tapes.
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| CN101069247A (en) * | 2004-12-02 | 2007-11-07 | 住友电气工业株式会社 | Superconducting cable |
| CN102779581A (en) * | 2012-07-04 | 2012-11-14 | 华北电力大学 | Superconducting strand based on ReBCO high-temperature superconducting tape |
| CN107710345A (en) * | 2015-06-30 | 2018-02-16 | Ls电线有限公司 | Superconducting Wire |
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