Aluminum alloy medium voltage cable for new energy charging station with anti-electromagnetic interference

Abstract

The present application relates to the technical field of medium voltage cable, in particular to an anti-electromagnetic interference aluminum alloy medium voltage cable for new energy charging station, which comprises, from inside to outside, an aluminum alloy conductor, an insulation layer, a first shielding layer, a second shielding layer and a sheath layer; the first shielding layer and the second shielding layer are made of the same material, which comprises, by mass percentage, 10-15% absorption-reflection porous composite material, 2-5% crosslinking agent, 1-3% dispersing agent, 1-3% antioxidant 1010 and the balance of polyolefin resin; the absorption-reflection porous composite material is prepared by the following method: preparing a wave-absorbing material; preparing a reflecting material; and ball-milling and mixing the reflecting material with the wave-absorbing material; the absorption-reflection porous composite material is added to the cable to realize a gradient dissipation mechanism of first absorption loss and then reflection blocking, thereby enhancing the anti-electromagnetic interference effect.

Description

Technical Field

[0001] This invention relates to the field of medium-voltage cable technology, specifically to an aluminum alloy medium-voltage cable for new energy charging stations that is resistant to electromagnetic interference. Background Technology

[0002] Cables for new energy charging stations are highly conductive wires designed for new energy vehicle charging systems, possessing characteristics such as high voltage resistance, aging resistance, water resistance, and flame retardancy. Unlike ordinary wires, they can stably carry high currents for extended periods, ensuring a safe and efficient charging process. In outdoor or humid environments, these cables can also effectively prevent leakage and short circuits, making them a core component for energy transmission in electric vehicles.

[0003] Electromagnetic interference is a major cause of electronic system failures. Any control malfunction caused by interference can lead to direct safety risks such as overheating, overvoltage, and electric arcing. If cable shielding is inadequate, the cable will radiate strong electromagnetic noise, severely polluting the surrounding electromagnetic environment. The CAN / LIN / PLC communication signals between the charging pile and the vehicle's BMS are extremely weak but critical; interference can lead to charging handshake failure, parameter misreading, charging interruption, and even safety accidents.

[0004] Therefore, this invention designs an aluminum alloy medium-voltage cable for new energy charging stations that is resistant to electromagnetic interference to solve the above problems. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an aluminum alloy medium-voltage cable for new energy charging stations that is resistant to electromagnetic interference.

[0006] An aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance includes, from the inside out, an aluminum alloy conductor, an insulation layer, a first shielding layer, a second shielding layer, and a sheath layer. The first and second shielding layers are made of the same raw materials, which, by mass percentage, include: 10-15% absorption-reflection porous composite material, 2-5% crosslinking agent, 1-3% dispersant, 1-3% antioxidant 1010, and the balance being polyolefin resin; The method for preparing the absorption-reflection porous composite material is as follows: Porous carbon was ultrasonically dispersed in an ethanol solution with a mass fraction of 40-60% at a solid-liquid ratio of 1g:95-100ml. The ultrasonic frequency was 40-50kHz and the time was 30-60min to obtain a dispersion. Manganese nitrate hexahydrate, ferric nitrate nonahydrate, and sodium citrate were added to the dispersion in sequence at a liquid-solid ratio of 95-100ml:0.1g:0.3g:0.4g and the mixture was stirred continuously for 1-2h. Then, hexamethylenetetramine was added at a solid-liquid ratio of 2g:10-15ml to the dispersion, and the mixture was stirred for another 30-40min to obtain a mixed solution. The mixture is then reacted at 160-180℃ for 6-10 hours, the reaction product is then centrifuged at 8000-9000 rpm for 5-10 minutes, and the precipitate obtained by centrifugation is washed alternately with deionized water and 95% ethanol for 3-5 times. Finally, it is vacuum dried at 60-80℃ for 12-24 hours to obtain the microwave absorbing material. Porous carbon and MXene nanosheets were dispersed in deionized water at a solid-liquid ratio of 1g:1g:180~190ml to obtain a suspension. Then, a polyvinyl alcohol aqueous solution with a mass fraction of 5~10% was added to the suspension at a mass ratio of 4~5:1. The mixture was heated and stirred at 80~85℃ for 1.5~2h to obtain a composite solution. The composite liquid is then directionally frozen in liquid nitrogen for 2-2.5 hours, then freeze-dried at -60 to -50°C for 24-36 hours, and then heated to 300-350°C at a rate of 2-4°C / min under an inert atmosphere and held for 2-3 hours to obtain the reflective material. The reflective material and the absorbing material are ball-milled at a mass ratio of 4 to 5:1, with a ball milling speed of 350 to 450 rpm and a time of 3 to 3.5 hours. The ball-to-material ratio is 10:1 to obtain an absorption-reflection porous composite material.

[0007] Furthermore, the porous carbon is tin-nitrogen dual-doped porous carbon, and the preparation method of the tin-nitrogen dual-doped porous carbon is as follows: N,N-dimethylformamide, triphenyltin-4-carboxylate, and N,N'-carbonyldiimidazole were mixed in a mass ratio of 24-26:1.5:0.6 and stirred and activated at 15-30°C under an inert atmosphere for 0.5-1 h. Then, nanocellulose with a mass ratio of 1:24-26 to N,N-dimethylformamide was added and the reaction was continued for 4-6 h. After the reaction was completed, the reaction product was washed 3-5 times alternately with tetrahydrofuran and 95% ethanol. After washing, the product was dried under vacuum to obtain tin-containing cellulose. Tin-containing cellulose, potassium carbonate, and deionized water are mixed and stirred at a solid-liquid ratio of 1g:2g:45~50ml for 60~70min. Then, 2,4,6-triaminopyrimidine is added at a solid-liquid ratio of 1g:15~20ml to deionized water, and the mixture is stirred continuously for 100~120min to obtain a slurry. This slurry is then spray-dried at an inlet temperature of 180~200℃, an outlet temperature of 90~100℃, and a feed rate of 10~12ml / min to obtain a porous carbon precursor. The porous carbon precursor was heated to 850-900℃ at a rate of 2-4℃ / min and held at that temperature for 2-3h. The resulting product was then impregnated in 1M dilute hydrochloric acid at a solid-liquid ratio of 1g:20-25ml for 4-6h. After impregnation, the impregnated product was removed and washed with deionized water until neutral. After washing, it was vacuum dried to obtain tin-nitrogen dual-doped porous carbon.

[0008] Explanation: Triphenyltin-4-carboxylate was covalently grafted onto nanocellulose via N,N'-carbonyldiimidazole-activated esterification, avoiding filler agglomeration and laying the foundation for the subsequent formation of a uniformly dispersed tin-carbon composite structure. This chemical bonding ensures that the tin source is not prone to segregation or loss during subsequent processing, guaranteeing the accuracy and stability of tin doping in the final product. During high-temperature carbonization, 2,4,6-triaminopyrimidine can efficiently introduce nitrogen atoms into the carbon framework, forming various forms such as pyridine nitrogen and graphitic nitrogen. Nitrogen doping can significantly improve the conductivity of carbon materials and introduce dipole polarization, enhancing dielectric loss. Furthermore, at high temperatures, potassium carbonate etching of carbon produces a large number of micropores and mesopores, further enhancing the conductivity. The porous structure not only increases the multiple reflection and scattering paths of electromagnetic waves within the material, but also optimizes the wave impedance matching between the material and air, reduces surface reflection, and improves absorption efficiency. After high-temperature carbonization, cellulose carbonization forms a conductive carbon network, and nitrogen doping further enhances its conductivity, which is the basis for generating conductive losses and reflecting electromagnetic waves. At high temperatures, tin can act as a polarization center, generating strong interfacial polarization and dipole polarization under alternating electromagnetic fields, providing significant dielectric losses. Dilute hydrochloric acid impregnation can effectively remove residual potassium salts and other impurities, purify the conductive network, and further open up blocked pores, increasing specific surface area and active sites, giving tin-nitrogen dual-doped porous carbon better loss capacity.

[0009] Furthermore, the vacuum drying temperature is 50~60℃ and the time is 12~24h.

[0010] Note: The reaction products such as porous carbon precursors contain coordinated water, crystal water or hydrogen-bonded water. These water molecules with strong binding forces require a certain amount of energy (heat) and sufficient time to desorb. Under this vacuum treatment condition, the water can fully diffuse and escape from the innermost micropores of the material.

[0011] Furthermore, the raw material of the insulating layer is cross-linked polyethylene.

[0012] Note: Polyethylene itself is an excellent insulator with high volume resistivity and low dielectric loss. After cross-linking, a three-dimensional network structure is formed between its molecular chains, which further improves its corona resistance and long-term dielectric stability, meeting the insulation requirements of medium-voltage cables. At the same time, the cross-linked structure endows it with excellent creep resistance, resistance to environmental stress cracking, and mechanical strength, ensuring that the insulation layer does not deform or break under long-term operation, thermal cycling, and mechanical stress.

[0013] Furthermore, the raw material for the sheath layer is polyethylene.

[0014] Note: Polyethylene has excellent wear resistance, impact resistance, and tear resistance, providing physical protection for the internal structure of the cable. It also has good resistance to ultraviolet rays, rain, moisture, and general chemical corrosion, making it very suitable for the laying environment of outdoor charging stations. In addition, polyethylene has good melt flowability, is easy to extrude and process, and has a smooth molding surface. Its raw material cost is relatively low, which can effectively control the overall cost of the cable.

[0015] Furthermore, the crosslinking agent is dicumyl peroxide.

[0016] Note: Dicumyl peroxide is a commonly used organic peroxide crosslinking agent. During processing, it can effectively decompose to generate free radicals, which can induce the formation of strong CC crosslinking bonds between polyethylene molecular chains. It can also prevent the shielding layer material from migrating or agglomerating after long-term use or heating, thereby permanently maintaining the porous structure of the foam layer and the directional arrangement of the magnetic field orientation layer, ensuring the long-term stability of the shielding performance.

[0017] Furthermore, the dispersant is zinc stearate.

[0018] Explanation: Zinc stearate molecules have an affinity for the surface of inorganic fillers at one end and for organic polymers at the other end. This allows it to effectively encapsulate other material particles, reduce their surface energy, prevent agglomeration, and ensure uniform distribution of the absorption-reflection porous composite material in the shielding layer.

[0019] Furthermore, the polyolefin resin is cross-linked polyethylene or ethylene-vinyl acetate copolymer.

[0020] Note: Ethylene-vinyl acetate copolymer helps improve interfacial bonding strength. At the same time, ethylene-vinyl acetate copolymer has excellent flexibility and elasticity, which can give the cable better bending performance; cross-linked polyethylene has rigidity, creep resistance and high temperature resistance.

[0021] Furthermore, the method for manufacturing the cable includes the following steps: S1. Preparation of aluminum alloy conductors Aluminum alloy monofilaments are twisted together to obtain an aluminum alloy conductor; S2, Preparation of the insulating layer The raw material for the insulating layer is extruded and coated onto the outside of the aluminum alloy conductor to obtain the insulating layer; S3. Preparation of the shielding layer S3-1. The absorber-reflector porous composite material, crosslinking agent, dispersant, antioxidant, and the balance polyolefin resin are formulated according to the mass percentage to obtain the raw materials for the first shielding layer and the second shielding layer. S3-2. The raw material of the first shielding layer is placed in a twin-screw extruder, premixed, homogenized, and finally extruded and coated onto the surface of the insulating layer to obtain the first shielding layer. The premixing process is carried out at a temperature of 150~165℃, the homogenization process is carried out at a temperature of 160~175℃, and after homogenization, supercritical carbon dioxide foaming treatment is carried out. The carbon dioxide injection pressure is 10~15 MPa, the foaming treatment temperature is 145~160℃, the time is 30~60s, the extrusion temperature is 130~140℃, and the screw speed of the twin-screw extruder is 200~300rpm. S3-3. The raw material of the second shielding layer is placed in a twin-screw extruder, pre-mixed, homogenized, and finally extruded and coated onto the first shielding layer to obtain the second shielding layer. The premixing process temperature is 155~170℃, the homogenization process temperature is 170~180℃, and a magnetic field of 0.3~0.6T is applied during homogenization, with the magnetic field direction parallel to the extrusion direction, for 1~3 minutes. The extrusion process temperature is 165~180℃, and the screw speed of the twin-screw extruder is 200~300 rpm. S4. Preparation of the sheath layer The raw material of the sheath layer is extruded and coated onto the surface of the second shielding layer to obtain the sheath layer, thus completing the cable preparation.

[0022] Explanation: During the preparation of the first shielding layer, supercritical CO2 was injected for foaming after homogenization and before extrusion, introducing a large number of micron-sized closed pores into the polymer matrix. This significantly reduced the overall equivalent dielectric constant of the first shielding layer, making it more compatible with the wave impedance of air (or the insulating layer). This reduces the direct reflection of electromagnetic waves at the outermost surface of the shielding layer. Furthermore, the foaming process allows the abundant internal pore structure to cause multiple reflections, scattering, and diffractions of incoming electromagnetic waves, greatly extending their propagation path within the material. This provides a more sufficient working space for the absorbing material, converting electromagnetic energy into heat energy through mechanisms such as polarization and magnetic loss, significantly increasing the absorption loss ratio of this layer. During the preparation of the second shielding layer, a strong magnetic field parallel to the extrusion direction is applied during homogenization. Since the reflective material contains sheet-like MXene and porous carbon, these materials will be oriented under the action of the strong magnetic field in the molten homogenization state. Their planar direction tends to be parallel to the direction of the magnetic field. This arrangement can form a denser and more continuous stacked conductive network in the direction perpendicular to the magnetic field (i.e., the radial direction of the cable, which is also the main direction of electromagnetic interference). This orientation structure reflects electromagnetic waves. When electromagnetic waves penetrate the foam layer and reach this high-density, highly oriented conductive layer, they will encounter extremely strong resistance. Most of the energy is directly reflected back. At the same time, the eddy current loss induced in the conductive network will also consume a lot of energy. The two shielding layers form a gradient structure, and the electromagnetic wave undergoes a complex dissipation process of entering, absorbing, reflecting, reflecting multiple times internally, and absorbing again, thereby improving the overall shielding effectiveness.

[0023] Compared with existing medium-voltage cables, the advantages of this invention are: (1) The absorption-reflection porous composite material in the shielding layer of the present invention combines the absorbing material and the reflective material. The high proportion of reflective material ensures that the main body of the composite material is still a continuous high conductivity network, which is the basis for the high shielding efficiency of the cable. The low proportion of absorbing material is used as a functional additive and will not destroy the main conductivity network. When the electromagnetic wave is incident on the shielding layer filled by this composite material, a portion of the electromagnetic wave energy is first consumed by the manganese iron oxide inside the absorbing material through polarization, resonance and other mechanisms. The remaining electromagnetic wave continues to penetrate and encounters the continuous and highly conductive reflective material skeleton. Due to its excellent conductivity and network structure similar to Faraday cage, it will generate strong reflection and eddy current loss on the electromagnetic wave, blocking or reflecting most of it, thereby realizing the gradient dissipation mechanism of first absorbing loss and then reflecting and blocking, thereby strengthening the anti-electromagnetic interference effect.

[0024] (2) The microwave absorbing material of the present invention uses porous carbon as a substrate, and loads manganese iron oxide on its surface and in its channels by a hydrothermal method. In this process, the porous carbon is first fully deagglomerated in an ethanol aqueous solution to expose a large number of surfaces and channels. Then, manganese nitrate and iron nitrate are used to provide metal sources, and sodium citrate is used as a complexing agent and morphology regulator to guide the uniform nucleation of oxides. Finally, hexamethylenetetramine is slowly decomposed under hydrothermal conditions to generate OH- - This process promotes the uniform precipitation of metal ions, while the decomposition products introduce nitrogen doping, enhancing the polarity of the carbon matrix. Thus, the manganese iron oxide generated by the hydrothermal reaction can serve as a dielectric / magnetic loss material. Anchored in nanoparticle form on the highly conductive network of porous carbon, this structure can efficiently convert incident electromagnetic wave energy into heat energy through various mechanisms such as interface polarization, natural resonance, and eddy current loss, forming a high-loss unit. In the reflective material of this invention, MXene possesses high metal-like conductivity and abundant surface functional groups, making it an ideal conductive shielding material. Its combination with porous carbon can complement each other, constructing a denser conductive network. Anisotropic structures are formed by directional freeze-drying, arranging PVA, MXene sheets, and porous carbon into layered or honeycomb-like directional porous structures. This structure can form continuous conductive pathways parallel to the pore direction. Through low-temperature heat treatment, PVA is partially carbonized, enhancing its adhesion and conductivity. At the same time, some impurities are removed, making the contact between MXene and porous carbon tighter, significantly improving the overall conductivity of the framework. This results in a lightweight, highly conductive, three-dimensional network framework with oriented pores. The high conductivity generates strong ohmic loss and surface reflection, blocking or reflecting electromagnetic waves back, thus improving the reflection effect.

[0025] (3) In the process of preparing the cable, the present invention prepares two shielding layers in a gradient manner. In the process of preparing the first shielding layer, supercritical CO2 is injected for foaming after homogenization and before extrusion, introducing a large number of micron-sized closed pores into the polymer matrix. This significantly reduces the overall equivalent dielectric constant of the first shielding layer, making it more compatible with the wave impedance of air (or insulation layer). This reduces the direct reflection of electromagnetic waves on the outermost surface of the shielding layer. Moreover, the foaming process allows the rich internal pore structure to cause multiple reflections, scattering, and diffraction of incoming electromagnetic waves, greatly extending their propagation path within the material. This provides more space for the absorbing material to function, converting electromagnetic energy into heat energy through mechanisms such as polarization and magnetic loss, significantly increasing the absorption loss ratio of this layer. In the process of preparing the second shielding layer, a strong magnetic field parallel to the extrusion direction is applied during homogenization. Since the reflective material contains sheet-like MXene and porous carbon, in the molten homogenized state, Under the influence of a strong magnetic field, these materials will align in a specific direction, with their planar orientation tending to be parallel to the magnetic field direction. This alignment can form a denser and more continuous stacked conductive network in the direction perpendicular to the magnetic field (i.e., the radial direction of the cable, which is also the main direction of electromagnetic interference). This orientation structure reflects electromagnetic waves. When electromagnetic waves penetrate the foam layer and reach this high-density, highly oriented conductive layer, they will encounter extremely strong impedance, and most of the energy will be directly reflected back. At the same time, the eddy current loss induced in the conductive network will also consume a lot of energy. Thus, the two shielding layers form a gradient structure, and the electromagnetic waves successively undergo a complex dissipation process of entry-absorption-reflection-multiple internal reflections-reabsorption, thereby improving the overall shielding effectiveness. Attached Figure Description

[0026] Figure 1 This is a comparison chart of the shielding performance results of Experiment Example 2 of this invention; Figure 2 This is a comparison chart of the shielding performance results of Experiment Example 3 of this invention; Figure 3 This is a comparison chart of the shielding performance results of Experiment Example 4 of this invention; Figure 4 This is a comparison chart of the shielding performance results of Experiment Example 5 of this invention. Detailed Implementation

[0027] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0028] Example 1: An aluminum alloy medium-voltage cable for an anti-electromagnetic interference new energy charging station, comprising, from the inside out, an aluminum alloy conductor, an insulation layer, a first shielding layer, a second shielding layer, and a sheath layer; the insulation layer is made of cross-linked polyethylene, and the sheath layer is made of polyethylene. The first and second shielding layers are made of the same raw materials, each comprising, by mass percentage: 13% absorption-reflection porous composite material, 3.5% crosslinking agent, 2% dispersant, 2% antioxidant 1010, and the balance being polyolefin resin; the crosslinking agent is dicumyl peroxide, the dispersant is zinc stearate, and the polyolefin resin is crosslinked polyethylene. The method for preparing the absorption-reflection porous composite material is as follows: Porous carbon was ultrasonically dispersed in a 50% ethanol solution at a solid-liquid ratio of 1g:98ml at a frequency of 45kHz for 45min to obtain a dispersion. Manganese nitrate hexahydrate, ferric nitrate nonahydrate, and sodium citrate were added to the dispersion in sequence at a liquid-solid ratio of 98ml:0.1g:0.3g:0.4g and the mixture was stirred continuously for 1.5h. Then, hexamethylenetetramine was added at a solid-liquid ratio of 2g:12ml to the dispersion, and the mixture was stirred for another 35min to obtain a mixed solution. The mixture was then reacted at 170°C for 8 hours, and the reaction product was centrifuged at 8500 rpm for 8 minutes. The precipitate obtained by centrifugation was washed four times alternately with deionized water and 95% ethanol. Finally, it was vacuum dried at 700°C for 18 hours to obtain the microwave absorbing material. Porous carbon and MXene nanosheets were dispersed in deionized water at a solid-liquid ratio of 1g:1g:185ml to obtain a suspension. Then, 8% polyvinyl alcohol aqueous solution was added to the suspension at a mass ratio of 4.5:1. The mixture was heated and stirred at 82°C for 1.8h to obtain a composite solution. The composite liquid was then directionally frozen in liquid nitrogen for 2.2 hours, freeze-dried at -55°C for 32 hours, and then heated to 330°C at a rate of 3°C / min under an argon atmosphere and held at that temperature for 2.5 hours to obtain the reflective material. The reflective material and the absorbing material were ball-milled at a mass ratio of 4.5:1, the ball milling speed was 400 rpm, the time was 3.2 h, and the ball-to-material ratio was 10:1 to obtain an absorption-reflection porous composite material. The porous carbon is tin-nitrogen dual-doped porous carbon, and the preparation method of the tin-nitrogen dual-doped porous carbon is as follows: N,N-dimethylformamide, triphenyltin-4-carboxylate, and N,N'-carbonyldiimidazole were mixed in a mass ratio of 25:1.5:0.6 and activated by stirring at 18°C ​​under an argon atmosphere for 0.8 h. Then, nanocellulose with a mass ratio of 1:25 to N,N-dimethylformamide was added and the reaction was continued for 5 h. After the reaction was completed, the reaction product was washed four times alternately with tetrahydrofuran and 95% ethanol. After washing, the product was dried under vacuum to obtain tin-containing cellulose. Tin-containing cellulose, potassium carbonate, and deionized water were mixed and stirred for 65 minutes at a solid-liquid ratio of 1 g: 2 g: 48 ml. Then, 2,4,6-triaminopyrimidine was added at a solid-liquid ratio of 1 g: 18 ml to deionized water, and the mixture was stirred for 110 minutes to obtain a slurry. The slurry was then spray-dried at an inlet temperature of 190°C, an outlet temperature of 95°C, and a feed rate of 11 ml / min to obtain a porous carbon precursor. The porous carbon precursor was heated to 880°C at a rate of 3°C / min and held at that temperature for 2.5 h. The resulting product was then impregnated in 1 M dilute hydrochloric acid at a solid-liquid ratio of 1 g: 22 ml for 5 h. After impregnation, the impregnated product was removed and washed with deionized water until neutral. After washing, it was vacuum dried at a temperature of 55°C for 18 h to obtain tin-nitrogen dual-doped porous carbon.

[0029] Example 2: This example differs from Example 1 in that the method for preparing the cable includes the following steps: S1. Preparation of aluminum alloy conductors Aluminum alloy monofilaments are twisted together to obtain an aluminum alloy conductor; S2, Preparation of the insulating layer Cross-linked polyethylene is melt-extruded at 150°C to coat the outside of the aluminum alloy conductor, thus obtaining an insulating layer; S3. Preparation of the shielding layer S3-1. The absorber-reflector porous composite material, crosslinking agent, dispersant, antioxidant and the balance polyolefin resin are prepared according to the mass percentages described in Example 1 to obtain the raw materials for the first shielding layer and the second shielding layer. S3-2. The raw material of the first shielding layer is placed in a twin-screw extruder, premixed, homogenized, and finally extruded and coated onto the surface of the insulating layer to obtain the first shielding layer. The premixing process temperature is 160℃, the homogenization process temperature is 170℃, and after homogenization, supercritical carbon dioxide foaming treatment is performed. The carbon dioxide injection pressure is 13MPa, the foaming treatment temperature is 150℃, the time is 45s, the extrusion temperature is 135℃, and the screw speed of the twin-screw extruder is 250rpm. S3-3. The raw material of the second shielding layer is placed in a twin-screw extruder, pre-mixed, homogenized, and finally extruded and coated onto the first shielding layer to obtain the second shielding layer. The premixing process temperature is 165°C, the homogenization process temperature is 175°C, and a magnetic field of 0.5T is applied during homogenization, with the magnetic field direction parallel to the extrusion direction for 2 minutes. The extrusion process temperature is 170°C, and the screw speed of the twin-screw extruder is 250 rpm. S4. Preparation of the sheath layer The polyethylene is melt-extruded at 150°C and coated onto the surface of the second shielding layer to obtain the sheath layer, thus completing the cable preparation.

[0030] Example 3: The difference between this example and Example 1 is that the raw materials of the first shielding layer and the second shielding layer are the same, and by mass percentage, they both include: 10% absorption-reflection porous composite material, 5% crosslinking agent, 3% dispersant, 3% antioxidant 1010 and the balance crosslinked polyethylene.

[0031] Example 4: The difference between this example and Example 1 is that the raw materials of the first shielding layer and the second shielding layer are the same, and by mass percentage, they both include: 15% absorption-reflection porous composite material, 2% crosslinking agent, 1% dispersant, 1% antioxidant 1010 and the balance ethylene-vinyl acetate copolymer.

[0032] Example 5: This example differs from Example 1 in that porous carbon is ultrasonically dispersed in a 40% ethanol solution at a solid-liquid ratio of 1g:95ml, the ultrasonic frequency is 40kHz, and the time is 30min to obtain a dispersion. Manganese nitrate hexahydrate, ferric nitrate nonahydrate, and sodium citrate are added to the dispersion in sequence at a liquid-solid ratio of 95ml:0.1g:0.3g:0.4g and the mixture is stirred continuously for 1h. Then, hexamethylenetetramine with a solid-liquid ratio of 2g:10ml to the dispersion is added, and the mixture is stirred for another 30min to obtain a mixed solution.

[0033] Example 6: This example differs from Example 1 in that porous carbon is ultrasonically dispersed in a 60% ethanol solution at a solid-liquid ratio of 1g:100ml, the ultrasonic frequency is 50kHz, and the time is 60min to obtain a dispersion. Manganese nitrate hexahydrate, ferric nitrate nonahydrate, and sodium citrate are added to the dispersion in sequence at a liquid-solid ratio of 100ml:0.1g:0.3g:0.4g and the mixture is stirred continuously for 2h. Then, hexamethylenetetramine with a solid-liquid ratio of 2g:15ml to the dispersion is added, and the mixture is stirred for another 40min to obtain a mixed solution.

[0034] Example 7: The difference between this example and Example 1 is that the mixture is reacted at 160°C for 6 hours, the reaction product is centrifuged at 8000 rpm for 5 minutes, and the precipitate obtained by centrifugation is washed three times alternately with water and ethanol. Finally, it is vacuum dried at 60°C for 12 hours to obtain the microwave absorbing material.

[0035] Example 8: The difference between this example and Example 1 is that the mixture is reacted at 180°C for 10 hours, the reaction product is centrifuged at 9000 rpm for 10 minutes, and the precipitate obtained by centrifugation is washed alternately with water and ethanol 5 times. Finally, it is vacuum dried at 80°C for 24 hours to obtain the microwave absorbing material.

[0036] Example 9: The difference between this example and Example 1 is that porous carbon and MXene nanosheets are dispersed in deionized water at a solid-liquid ratio of 1g:1g:180ml to obtain a suspension. Then, a 5% polyvinyl alcohol aqueous solution is added to the suspension at a mass ratio of 4:1, and the mixture is heated and stirred at 80°C for 1.5h to obtain a composite solution.

[0037] Example 10: This example differs from Example 1 in that porous carbon and MXene nanosheets are dispersed in deionized water at a solid-liquid ratio of 1g:1g:190ml to obtain a suspension. Then, a 10% polyvinyl alcohol aqueous solution is added to the suspension at a mass ratio of 5:1, and the mixture is heated and stirred at 85°C for 2 hours to obtain a composite solution.

[0038] Example 11: The difference between this example and Example 1 is that the composite liquid is further directionally frozen in liquid nitrogen for 2 hours, then freeze-dried at -50°C for 24 hours, and then heated to 300°C at a rate of 2°C / min under an inert atmosphere and held at that temperature for 2 hours to obtain the reflective material.

[0039] Example 12: The difference between this example and Example 1 is that the composite liquid is further directionally frozen in liquid nitrogen for 2.5 hours, then freeze-dried at -60°C for 36 hours, and then heated to 350°C at a rate of 4°C / min under an inert atmosphere and held at that temperature for 3 hours to obtain the reflective material.

[0040] Example 13: The difference between this example and Example 1 is that the reflective material and the absorbing material are ball-milled at a mass ratio of 4:1, the ball milling speed is 350 rpm, the time is 3 hours, and the ball-to-material ratio is 10:1, to obtain an absorption-reflection porous composite material.

[0041] Example 14: The difference between this example and Example 1 is that the reflective material and the absorbing material are ball-milled at a mass ratio of 5:1, the ball milling speed is 450 rpm, the time is 3.5 h, and the ball-to-material ratio is 10:1, to obtain an absorption-reflection porous composite material.

[0042] Example 15: This example differs from Example 1 in that N,N-dimethylformamide, triphenyltin-4-carboxylate, and N,N'-carbonyldiimidazole were mixed in a mass ratio of 24:1.5:0.6 and activated by stirring at 15°C under an inert atmosphere for 0.5 h. Then, nanocellulose with a mass ratio of 1:24 to N,N-dimethylformamide was added and the reaction continued for 4 h. After the reaction was completed, the reaction product was washed three times alternately with tetrahydrofuran and ethanol. After washing, it was vacuum dried to obtain tin-containing cellulose.

[0043] Example 16: This example differs from Example 1 in that N,N-dimethylformamide, triphenyltin-4-carboxylate, and N,N'-carbonyldiimidazole were mixed in a mass ratio of 26:1.5:0.6 and activated by stirring at 30°C under an inert atmosphere for 1 hour. Then, nanocellulose with a mass ratio of 1:26 to N,N-dimethylformamide was added and the reaction continued for 6 hours. After the reaction was completed, the reaction product was washed 5 times alternately with tetrahydrofuran and ethanol. After washing, it was vacuum dried to obtain tin-containing cellulose.

[0044] Example 17: This example differs from Example 1 in that tin-containing cellulose, potassium carbonate, and deionized water are mixed and stirred for 60 minutes at a solid-liquid ratio of 1g:2g:45ml. Then, 2,4,6-triaminopyrimidine with a solid-liquid ratio of 1g:15ml to deionized water is added, and the mixture is stirred continuously for 100 minutes to obtain a slurry. This slurry is then spray-dried at an inlet temperature of 180°C, an outlet temperature of 90°C, and a feed rate of 10ml / min to obtain a porous carbon precursor.

[0045] Example 18: This example differs from Example 1 in that tin-containing cellulose, potassium carbonate, and deionized water are mixed and stirred for 70 minutes at a solid-liquid ratio of 1g:2g:50ml. Then, 2,4,6-triaminopyrimidine with a solid-liquid ratio of 1g:20ml to deionized water is added, and the mixture is stirred continuously for 120 minutes to obtain a slurry. This slurry is then spray-dried at an inlet temperature of 200°C, an outlet temperature of 100°C, and a feed rate of 12ml / min to obtain a porous carbon precursor.

[0046] Example 19: This example differs from Example 1 in that the porous carbon precursor is heated to 850°C at a rate of 2°C / min and held at that temperature for 2 hours. The resulting product is then immersed in 1 M dilute hydrochloric acid at a solid-liquid ratio of 1 g: 20 ml for 4 hours. After immersion, the immersed product is removed and washed with deionized water until neutral. After washing, it is vacuum dried to obtain tin-nitrogen dual-doped porous carbon.

[0047] Example 20: This example differs from Example 1 in that the porous carbon precursor is heated to 900°C at a rate of 4°C / min and held at that temperature for 3 hours. The resulting product is then impregnated in 1 M dilute hydrochloric acid at a solid-liquid ratio of 1 g: 25 ml for 6 hours. After impregnation, the impregnated product is removed and washed with deionized water until neutral. After washing, it is vacuum dried to obtain tin-nitrogen dual-doped porous carbon.

[0048] Example 21: This example differs from Example 2 in that the premixing processing temperature is 150°C, the homogenization processing temperature is 160°C, and after homogenization, supercritical carbon dioxide foaming treatment is performed. The carbon dioxide injection pressure is 10MPa, the foaming treatment temperature is 145°C, the time is 30s, the extrusion temperature is 130°C, and the screw speed of the twin-screw extruder is 200rpm.

[0049] Example 22: This example differs from Example 2 in that the premixing processing temperature is 165°C, the homogenization processing temperature is 175°C, and after homogenization, supercritical carbon dioxide foaming treatment is performed. The carbon dioxide injection pressure is 15MPa, the foaming treatment temperature is 160°C, the time is 60s, the extrusion temperature is 140°C, and the screw speed of the twin-screw extruder is 300rpm.

[0050] Example 23: This example differs from Example 2 in that the premixing processing temperature is 155°C, the homogenization processing temperature is 170°C, and a magnetic field of 0.3T is applied during homogenization, with the magnetic field direction parallel to the extrusion direction for 1 minute. The extrusion processing temperature is 165°C, and the screw speed of the twin-screw extruder is 200 rpm.

[0051] Example 24: This example differs from Example 2 in that the premixing processing temperature is 170°C, the homogenization processing temperature is 180°C, and a magnetic field of 0.6T is applied during homogenization, with the magnetic field direction parallel to the extrusion direction, for 3 minutes. The extrusion processing temperature is 180°C, and the screw speed of the twin-screw extruder is 300 rpm.

[0052] Experimental Example: The description of this experimental example is based on the scheme described in Example 2, and aims to illustrate the practical application effect of the present invention.

[0053] The tensile strength of the aluminum alloy medium-voltage cable prepared in Example 2 was tested according to GB / T8804.2.

[0054] The flame retardancy rating of the aluminum alloy medium-voltage cable prepared in Example 2 was tested in accordance with GB / T19666-2019.

[0055] The shielding performance of the aluminum alloy medium-voltage cables prepared in each embodiment and comparative example was tested.

[0056] Investigation 1: Investigate the comprehensive performance of the cable prepared in Example 2.

[0057] Table 1. Overall performance of the cable in Example 2

[0058] As shown in Table 1, the cable prepared by this invention has excellent comprehensive performance and excellent anti-electromagnetic interference performance.

[0059] Investigation 2: Investigate the effect of the component ratio of the first and second shielding layers on the shielding performance of the cable.

[0060] Depend on Figure 1 The results show that, compared with Examples 1 and 3-4, both too small and too large proportions of the absorption-reflection porous composite material will reduce the shielding performance of the cable. Therefore, from a comprehensive perspective, the parameters of Example 1 are relatively better.

[0061] Inquiry 3: Investigate the influence of the preparation parameters of absorption-reflection porous composite materials on the shielding performance of cables.

[0062] The difference between Comparative Example 1 and Example 1 is that the proportion of absorbing material is greater than that of reflective material; Depend on Figure 2 The results show that if the proportion of absorbing material increases, insufficient reflective material will directly lead to a significant decrease in the shielding performance at low frequencies, making the cable less capable of dealing with low-frequency conducted interference generated by motors and inverters. This will enhance the absorption effect in the mid-to-high frequency bands, but the lack of a sufficient reflective layer to resist electromagnetic waves will cause more energy to directly enter the absorption layer, which may exceed its loss capacity, making it impossible for the overall shielding performance to achieve a better effect. Therefore, the shielding performance of Comparative Example 1 is significantly lower than that of Examples 1 and Examples 5 to 14. Comparing Examples 1 and 5-14, it can be seen that if the preparation parameters of the mixture are too small or too large, the centrifugal drying parameters of the mixture are too small or too large, the preparation parameters of the composite liquid are too small or too large, the freezing parameters are too small or too large, and the proportion of the reflective material is too small or too large, the shielding performance of the cable will be reduced. Therefore, from a comprehensive perspective, the parameters of Example 1 are relatively better.

[0063] Investigation 4: Investigate the influence of the preparation parameters of tin-nitrogen doped porous carbon on the shielding performance of cables.

[0064] Depend on Figure 3 The results show that, compared with Examples 1 and 15 to 20, the shielding performance of the cable is reduced if the preparation parameters of the tin-containing cellulose are too small or too large, the preparation parameters of the porous carbon precursor are too small or too large, and the carbonization impregnation parameters are too small. The shielding performance of Example 20 is the same as that of Example 1, but the carbonization impregnation parameters are higher and the cost is higher. Therefore, from an economic point of view, the parameters of Example 1 are relatively better.

[0065] Investigation 5: Investigate the influence of cable manufacturing parameters on the shielding performance of cables.

[0066] The difference between Comparative Example 2 and Example 2 is that the first shielding layer is not foamed. The difference between Comparative Example 3 and Example 2 is that the second shielding layer is not subjected to a magnetic field treatment; Depend on Figure 4 The results show that Comparative Example 2 lacks foaming treatment, so electromagnetic waves cannot be reflected, scattered, and absorbed and dissipated multiple times at the interface of a large number of foam cells, resulting in a decrease in overall shielding effectiveness and a significant deficiency in high-frequency absorption loss. Comparative Example 3 lacks magnetic field treatment, so the reflective material cannot form a directional and continuous electromagnetic network, resulting in a decrease in reflection loss and a weakening of the shielding ability against low-frequency interference such as motors. The isotropic random distribution leads to electrical weaknesses in the shielding layer, and electromagnetic waves are prone to leakage from weak points. Therefore, the shielding performance of Comparative Example 2 and Comparative Example 3 is significantly lower than that of Examples 2 and 21 to 24. Compared with Examples 2 and 21 to 24, both excessively small or large foaming parameters and excessively small or large magnetic field parameters will reduce the shielding performance of the cable. Therefore, from a comprehensive perspective, the parameters of Example 2 are relatively better.

Claims

1. An aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance, characterized in that, From the inside out, it includes an aluminum alloy conductor, an insulating layer, a first shielding layer, a second shielding layer, and a sheath layer. The first and second shielding layers are made of the same raw materials, which, by mass percentage, include: 10-15% absorption-reflection porous composite material, 2-5% crosslinking agent, 1-3% dispersant, 1-3% antioxidant 1010 and the balance polyolefin resin; The method for preparing the absorption-reflection porous composite material is as follows: Porous carbon was ultrasonically dispersed in an ethanol solution with a mass fraction of 40-60% at a solid-liquid ratio of 1g:95-100ml. The ultrasonic frequency was 40-50kHz and the time was 30-60min to obtain a dispersion. Manganese nitrate hexahydrate, ferric nitrate nonahydrate, and sodium citrate were added to the dispersion in sequence at a liquid-solid ratio of 95-100ml:0.1g:0.3g:0.4g and the mixture was stirred continuously for 1-2h. Then, hexamethylenetetramine was added at a solid-liquid ratio of 2g:10-15ml to the dispersion, and the mixture was stirred for another 30-40min to obtain a mixed solution. The mixture is then reacted at 160-180℃ for 6-10 hours, the reaction product is then centrifuged at 8000-9000 rpm for 5-10 minutes, and the precipitate obtained by centrifugation is washed alternately with deionized water and 95% ethanol for 3-5 times. Finally, it is vacuum dried at 60-80℃ for 12-24 hours to obtain the microwave absorbing material. Porous carbon and MXene nanosheets were dispersed in deionized water at a solid-liquid ratio of 1g:1g:180~190ml to obtain a suspension. Then, a polyvinyl alcohol aqueous solution with a mass fraction of 5~10% was added to the suspension at a mass ratio of 4~5:

1. The mixture was heated and stirred at 80~85℃ for 1.5~2h to obtain a composite solution. The composite liquid is then directionally frozen in liquid nitrogen for 2-2.5 hours, then freeze-dried at -60 to -50°C for 24-36 hours, and then heated to 300-350°C at a rate of 2-4°C / min under an inert atmosphere and held for 2-3 hours to obtain the reflective material. The reflective material and the absorbing material are ball-milled at a mass ratio of 4 to 5:1, with a ball milling speed of 350 to 450 rpm and a time of 3 to 3.5 hours. The ball-to-material ratio is 10:1 to obtain an absorption-reflection porous composite material.

2. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 1, characterized in that, The porous carbon is tin-nitrogen dual-doped porous carbon, and the preparation method of the tin-nitrogen dual-doped porous carbon is as follows: N,N-dimethylformamide, triphenyltin-4-carboxylate, and N,N'-carbonyldiimidazole were mixed in a mass ratio of 24-26:1.5:0.6 and stirred and activated at 15-30°C under an inert atmosphere for 0.5-1 h. Then, nanocellulose with a mass ratio of 1:24-26 to N,N-dimethylformamide was added and the reaction was continued for 4-6 h. After the reaction was completed, the reaction product was washed 3-5 times alternately with tetrahydrofuran and 95% ethanol. After washing, the product was dried under vacuum to obtain tin-containing cellulose. Tin-containing cellulose, potassium carbonate, and deionized water are mixed and stirred at a solid-liquid ratio of 1g:2g:45~50ml for 60~70min. Then, 2,4,6-triaminopyrimidine is added at a solid-liquid ratio of 1g:15~20ml to deionized water, and the mixture is stirred continuously for 100~120min to obtain a slurry. This slurry is then spray-dried at an inlet temperature of 180~200℃, an outlet temperature of 90~100℃, and a feed rate of 10~12ml / min to obtain a porous carbon precursor. The porous carbon precursor was heated to 850-900℃ at a rate of 2-4℃ / min and held at that temperature for 2-3h. The resulting product was then impregnated in 1M dilute hydrochloric acid at a solid-liquid ratio of 1g:20-25ml for 4-6h. After impregnation, the impregnated product was removed and washed with deionized water until neutral. After washing, it was vacuum dried to obtain tin-nitrogen dual-doped porous carbon.

3. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 2, characterized in that, The vacuum drying temperature is 50~60℃ and the time is 12~24h.

4. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 1, characterized in that, The raw material for the insulating layer is cross-linked polyethylene.

5. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 1, characterized in that, The raw material for the sheath layer is polyethylene.

6. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 1, characterized in that, The crosslinking agent is dicumyl peroxide.

7. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 1, characterized in that, The dispersant is zinc stearate.

8. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 1, characterized in that, The polyolefin resin is cross-linked polyethylene or ethylene-vinyl acetate copolymer.

9. The aluminum alloy medium-voltage cable for new energy charging stations with electromagnetic interference resistance as described in claim 1, characterized in that, The method for preparing the cable includes the following steps: S1. Preparation of aluminum alloy conductors Aluminum alloy monofilaments are twisted together to obtain an aluminum alloy conductor; S2, Preparation of the insulating layer The raw material for the insulating layer is extruded and coated onto the outside of the aluminum alloy conductor to obtain the insulating layer; S3. Preparation of the shielding layer S3-1. The absorber-reflector porous composite material, crosslinking agent, dispersant, antioxidant, and the balance polyolefin resin are formulated according to the mass percentage to obtain the raw materials for the first shielding layer and the second shielding layer. S3-2. The raw material of the first shielding layer is placed in a twin-screw extruder, premixed, homogenized, and finally extruded and coated onto the surface of the insulating layer to obtain the first shielding layer. The premixing process is carried out at a temperature of 150~165℃, the homogenization process is carried out at a temperature of 160~175℃, and after homogenization, supercritical carbon dioxide foaming treatment is carried out. The carbon dioxide injection pressure is 10~15 MPa, the foaming treatment temperature is 145~160℃, the time is 30~60s, the extrusion temperature is 130~140℃, and the screw speed of the twin-screw extruder is 200~300rpm. S3-3. The raw material of the second shielding layer is placed in a twin-screw extruder, pre-mixed, homogenized, and finally extruded and coated onto the first shielding layer to obtain the second shielding layer. The premixing process temperature is 155~170℃, the homogenization process temperature is 170~180℃, and a magnetic field of 0.3~0.6T is applied during homogenization, with the magnetic field direction parallel to the extrusion direction, for 1~3 minutes. The extrusion process temperature is 165~180℃, and the screw speed of the twin-screw extruder is 200~300 rpm. S4. Preparation of the sheath layer The raw material of the sheath layer is extruded and coated onto the surface of the second shielding layer to obtain the sheath layer, thus completing the cable preparation.

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