A high current aluminium alloy conductor polypropylene insulated medium voltage power cable

Abstract

The application discloses a large-current aluminum alloy conductor polypropylene insulated medium-voltage power cable and belongs to the technical field of cable preparation, which is used to solve the technical problem that the shielding performance and heat dissipation performance of the polypropylene insulated power cable in the prior art need to be further improved. The polypropylene insulated power cable prepared by the application introduces modified core-shell carbon-nitrogen bodies and silicon-oxygen-nitrogen polypropylene into a polypropylene insulation layer, and a nucleating agent is used to regulate the crystalline structure. The modified core-shell carbon-nitrogen bodies improve the interface heat conduction and charge distribution, the silicon-oxygen-nitrogen polypropylene enhances the chain segment stability and crystalline compactness, and the nucleating agent makes the matrix form a uniform microstructure. Through the structure design, the cable insulation layer maintains a high level in terms of heat distortion temperature, thermal conductivity and volume resistivity, and at the same time, good electromagnetic shielding efficiency is realized, and the heat resistance, thermal conductivity and insulation performance are comprehensively improved.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, specifically to a high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable. Background Technology

[0002] Medium-voltage power cables with aluminum alloy conductors and polypropylene insulation are a type of structure that has been widely used in power transmission in recent years. Research on this topic mainly focuses on improving shielding and heat dissipation performance. With the increase in power grid load and voltage level, electromagnetic leakage and heat accumulation problems generated by cables during operation have become increasingly prominent. Conventional cables often use copper tape, aluminum tape, or composite metal materials as shielding layers to suppress external electromagnetic interference and reduce local overheating caused by uneven internal electric field distribution.

[0003] Meanwhile, in terms of insulation and sheath materials, fillers, composite polymers, or modified polypropylene are being gradually introduced to improve the thermal conductivity of the materials, promote heat dissipation of the cable under high load conditions, and reduce the dielectric performance degradation caused by heat accumulation. Overall, the optimization of materials and structures related to electromagnetic shielding and thermal management has become an important direction in the research of medium-voltage power cables.

[0004] Currently, medium-voltage power cables with aluminum alloy conductors and polypropylene insulation still face some problems during long-term operation: First, the shielding structure, which is mostly made of metal strip or metal wire braid, has limited attenuation effect in high-frequency electromagnetic interference environment, and the interface bonding between the shielding layer and the insulation layer is insufficient, which easily leads to electric field concentration and local breakdown risk; Second, the polypropylene insulation material itself has a low thermal conductivity, and the heat is not easily dissipated in time during cable operation, resulting in excessive temperature rise, which may accelerate material aging and insulation performance degradation.

[0005] Meanwhile, while some modification methods can improve individual properties, they often damage the electrical insulation properties or thermal stability of the material, making it difficult to maintain a balance between thermal conductivity, heat resistance and dielectric properties. These problems are more prominent in application scenarios with high load, long-term operation or complex electromagnetic environment, limiting the application of cables under conditions of higher reliability and longer life. Summary of the Invention

[0006] The purpose of this invention is to provide a high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable to solve the technical problem that the shielding performance and heat dissipation performance of polypropylene insulated power cables in the prior art need to be further improved.

[0007] The objective of this invention can be achieved through the following technical solution: a high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable, comprising an aluminum alloy conductor layer, a conductor shielding layer, and a polypropylene insulation layer arranged from the inside out;

[0008] The aluminum alloy conductor layer is made of aluminum-copper alloy with an aluminum-copper weight ratio of 99:1, a cross-sectional length of 15mm, a width of 3mm, and a rounded corner transition of R=1mm.

[0009] The conductor shielding layer has a thickness of 0.8 mm and is obtained by melting and extruding a mixture of polypropylene and carbon black in a weight ratio of 100:3 onto the surface of an aluminum alloy conductor layer, followed by natural curing.

[0010] The polypropylene insulation layer is 3.5 mm thick and is obtained by melt extrusion of composite polypropylene material onto the surface of the conductor shielding layer and natural curing.

[0011] The reaction principle for preparing polypropylene insulation layers is as follows:

[0012] First, polypropylene is used as the main matrix to give the material good mechanical properties and electrical insulation. On this basis, siloxane-nitro polypropylene is introduced. Its molecular structure contains Si-O-Si, Si-N and other bridging bonds, which can form an organic-inorganic hybrid cross-linking network between polypropylene chains, thereby improving the thermal stability and dielectric strength of the material.

[0013] Meanwhile, the added modified core-shell carbonitride, as an inorganic / carbon-based functional filler, forms a stable interface with the polypropylene matrix, which not only provides additional charge shielding and thermal conduction channels, but also plays a reinforcing role at the microscopic level, improving the dielectric loss control capability and mechanical strength of the insulation layer.

[0014] Furthermore, the composite polypropylene material comprises the following raw material components by weight: 80-90 parts polypropylene, 10-15 parts siloxane-nitrogen polypropylene, 3-5 parts modified core-shell carbonitride, 0.1-0.3 parts antioxidant, 0.1-0.3 parts heat stabilizer, 0.1-0.2 parts lubricant, and 0.2-0.3 parts polypropylene β-nucleating agent;

[0015] Furthermore, the antioxidant is one or both of N,N'-diphenyl-p-phenylenediamine and dioctadecyl thiodipropionate; the heat stabilizer is tris(2,4-di-tert-butylphenyl) phosphite; and the lubricant is one or both of calcium stearate or zinc stearate.

[0016] Furthermore, the preparation method of siloxa-nitro polypropylene includes the following steps:

[0017] A1. Add polypropylene, maleic anhydride, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and di-tert-butyl peroxide to the extruder. Under nitrogen protection, raise the extruder temperature to 190-210℃ and maintain the shear rate at 150-200s. -1 Heat-shear for 2-3 minutes, and then post-process to obtain anhydride-grafted polypropylene;

[0018] A2. Add anhydride-grafted polypropylene, anhydrous ethanol and deionized water to a reaction vessel. Adjust the pH of the reaction system to 4-5 using acetic acid, then raise the temperature of the reaction vessel to 50-60℃ and keep it at this temperature for 8-10 hours with stirring. Post-treatment yields silicon-oxygen-nitrogen hybrid polypropylene.

[0019] The reaction principle for preparing modified core-shell carbonitrides is as follows:

[0020] Under the action of free radical initiators, the polypropylene molecular chain undergoes free radical activation, and maleic anhydride molecules are grafted onto the polypropylene backbone via free radical addition to form a graft copolymer containing anhydride groups. At the same time, the vinyl groups of γ-aminopropyltriethoxysilane and vinyltriethoxysilane can also undergo grafting reactions with free radical active sites, introducing organosilane structural units into the polypropylene chain. This process essentially introduces both polar anhydride groups and hydrolyzable silane groups into the polypropylene molecular chain, providing active sites for subsequent reactions.

[0021] In a moderately acidic and alcohol / water mixed system, the triethoxysilyl groups grafted onto the polypropylene molecular chain undergo hydrolysis to generate silanols. Subsequently, these silanols can undergo further condensation and cross-linking reactions with each other and with the nitrogen atoms on the aminopropyl groups, establishing Si-O-Si chemical bonds between the polypropylene segments. Through this organic-inorganic synergistic cross-linking, the polypropylene matrix is ​​transformed into a composite polymer containing silicon, oxygen, and nitrogen heteroatoms bridging structures, ultimately yielding silicon-oxygen-nitrogen heteropolypropylene.

[0022] Further, in step A1, the ratio of polypropylene, maleic anhydride, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and di-tert-butyl peroxide is 10-12g:1g:0.6-0.8g:0.4g:0.2g. The post-processing includes: after shearing, extruding the material to obtain an extrudate, naturally cooling the extrudate to room temperature, pulverizing it through an 80-mesh sieve, and obtaining anhydride-grafted polypropylene.

[0023] Furthermore, in step A2, the ratio of anhydride-grafted polypropylene, anhydrous ethanol, and deionized water is 4-5 g: 50 mL: 10 mL. The post-treatment includes: after the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction solution to collect the filter cake, wash the filter cake 3-5 times with anhydrous ethanol, and then transfer the filter cake to a drying oven at 80°C and vacuum dry it to constant weight to obtain silicon-oxygen-nitrogen hybrid polypropylene.

[0024] Furthermore, the method for preparing the modified core-shell carbonitride includes the following steps:

[0025] B1. Place the metal coordination polymer solid in a quartz boat, introduce nitrogen into the muffle furnace to purge the air, keep the nitrogen inlet and transfer the quartz boat into the muffle furnace, raise the temperature of the muffle furnace to 650-700℃ and hold for 30-40 min, and then perform post-processing to obtain a metal nitrogen-doped carbon core and shell.

[0026] B2. Add the nitrogen-doped carbon core and shell, N,N-dimethylformamide, trimethylsilyl azide and propylene trifluorochlorosilane to the reactor, purge with nitrogen, raise the temperature of the reactor to 60-80℃ and keep it at that temperature for 4-6 hours, and then proceed with the post-treatment to obtain the modified core-shell carbonitride.

[0027] The reaction principle for preparing modified core-shell carbonitrides is as follows:

[0028] Metal coordination polymers are treated at high temperatures in an inert atmosphere, causing the organic components in the polymer backbone to undergo carbonization reactions and form a continuous carbon structure. At the same time, the nitrogen element originally in the ligand molecules dissolves into the carbon backbone under high temperature conditions, achieving nitrogen doping. Metal ions play a catalytic and structure-inducing role in the carbonization process, ultimately forming a metal-nitrogen-carbon core-shell structure on the carbon phase surface. This core-shell structure has the dual characteristics of a metal center and a nitrogen-doped carbon shell, exhibiting excellent stability.

[0029] Through surface chemical reactions, the carbon shell surface undergoes modification processes such as nitrogen alkylation / silanization, introducing nitrogen-containing groups and fluorine-containing silane groups onto the material surface. These functionalized structures can form a stable organic layer on the carbonitride surface, thereby giving the material better interfacial compatibility, dispersibility and surface activity, and finally preparing modified core-shell carbonitride.

[0030] Furthermore, in step B1, the heating rate of the muffle furnace is 3-5℃ / min, and the post-processing includes: cooling the muffle furnace to room temperature and removing the quartz boat, collecting the powder material, and obtaining a metal nitrogen-doped carbon core and shell.

[0031] Further, in step B2, the ratio of the amount of metal nitrogen-doped carbon core-shell, N,N-dimethylformamide, trimethylsilyl azide, and propylene trifluorochlorosilane is 8-10g:18-20mL:0.2-0.3g:0.2-0.3g. The post-treatment includes: after the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction solution to collect the filter cake, wash the filter cake 3-5 times with anhydrous ethanol, and then transfer the filter cake to a drying oven at 80℃ and vacuum dry it to constant weight to obtain the modified core-shell carbon-nitrogen body.

[0032] Furthermore, the preparation method of the metal coordination polymer includes the following steps:

[0033] C1. Dimethylaminopropylamine, 4-ethynylbenzaldehyde and anhydrous ethanol are added to a reaction vessel. The pH of the reaction system is adjusted to 4-5 using 1 mol / L hydrochloric acid ethanol solution. The temperature of the reaction vessel is raised to 40-60℃ and stirred for 4-6 hours. The ethynyl Schiff base is then obtained after post-treatment.

[0034] C2. Add alkynyl Schiff base, zinc chloride, copper chloride, polyvinylpyrrolidone and anhydrous ethanol to the reactor. After purging with nitrogen, raise the temperature of the reactor to 60-80℃ and keep it at this temperature for 6-8 hours with stirring. Post-treatment yields the metal coordination polymer.

[0035] The reaction principle for preparing metal coordination polymers is as follows:

[0036] First, dimethylaminopropylamine undergoes a condensation reaction with 4-ethynylbenzaldehyde to form a Schiff base ligand containing an alkynyl substituent under acidic conditions. In this process, the amino group and the aldehyde group undergo nucleophilic addition and dehydration condensation to generate a C=N bond structure. At the same time, the alkynyl structure is preserved, so that the ligand has both a nitrogen donor and an alkynyl site, providing conditions for subsequent coordination and structural extension.

[0037] Subsequently, the obtained alkynyl Schiff base was reacted with zinc chloride and copper chloride. The imine nitrogen in the Schiff base molecule and the alkynyl group on the side group of the benzene ring can both serve as coordination sites and undergo stable coordination with metal ions. With the assistance of stabilizers such as polyvinylpyrrolidone, metal ions form bridges between multiple ligands, thereby constructing a three-dimensional network-like coordination polymer skeleton, thus obtaining a metal coordination polymer.

[0038] Further, in step C1, the ratio of dimethylaminopropylamine, 4-ethynylbenzaldehyde, and anhydrous ethanol is 5-6 g: 5-6 g: 100 mL. The post-treatment includes: after the reaction is completed, the reaction solution is transferred to a rotary evaporator at 40 °C, the solvent is removed by vacuum evaporation, 20 times the mass of deionized water is added to the residue, and after precipitation is complete, the filter cake is collected by vacuum filtration, and the filter cake is washed 3-5 times with anhydrous ethanol. The filter cake is then transferred to a drying oven at 40 °C and vacuum dried to constant weight to obtain an ethynyl Schiff base.

[0039] Further, in step C2, the ratio of the alkynyl Schiff base, zinc chloride, copper chloride, polyvinylpyrrolidone, and anhydrous ethanol is 1g:0.4g:0.2-0.3g:0.2g:100mL. The post-treatment includes: after the reaction is completed, the reaction solution is centrifuged to collect the gel, and the gel is replaced three times with three times its mass of anhydrous ethanol, each time for 6-8 hours. After each replacement, the gel is transferred to a drying oven at 60°C and vacuum dried to constant weight to obtain the metal coordination polymer.

[0040] Furthermore, an insulating shielding layer, a metal shielding layer, a wrapping layer, and an outer sheath layer are sequentially provided outside the polypropylene insulation layer;

[0041] Furthermore, the insulation shielding layer has a thickness of 0.5 mm and is obtained by melting and extruding a mixture of polyvinyl chloride, calcium stearate and carbon black in a weight ratio of 100:0.5:3 onto the surface of a polypropylene insulation layer, followed by natural curing.

[0042] Furthermore, the metal shielding layer has a thickness of 0.15 mm and is obtained by wrapping copper strip around the surface of the insulating shielding layer;

[0043] Furthermore, the wrapping layer has a thickness of 1.2 mm, which is obtained by wrapping polyurethane wrapping tape around the surface of the metal shielding layer;

[0044] Furthermore, the outer sheath layer has a thickness of 1.8 mm and is obtained by melting and extruding a mixture of polyvinyl chloride and calcium stearate in a weight ratio of 100:3 onto the surface of the wrapping layer, followed by natural curing.

[0045] The present invention has the following beneficial effects:

[0046] 1. The polypropylene insulated power cable prepared by this invention introduces silicon-oxygen-nitrogen hybrid polypropylene and modified core-shell carbonitride into the polypropylene insulation layer, forming an effective dielectric loss channel inside the material. This absorbs and attenuates incident electromagnetic waves, reducing the propagation intensity of energy in the insulating medium. The polypropylene insulation layer has a moderate thickness and fits tightly with the inner conductor shielding layer and the outer insulating shielding layer, avoiding electric field concentration and leakage channels, further enhancing the dissipation effect of electromagnetic energy. On the outside, the metal shielding layer is made of copper tape, constructing a continuous highly conductive reflection barrier that reflects residual electromagnetic waves back to the inner layer, causing multiple reflections and absorptions between the conductor shielding layer, the polypropylene insulation layer, and the insulating shielding layer. The wrapping layer and the outer sheath layer ensure the tight bonding and overall stability of each layer. Finally, through the synergistic effect of material absorption and structural reflection, the cable achieves a composite shielding mechanism of "absorption-reflection-reabsorption," exhibiting excellent electromagnetic shielding performance.

[0047] 2. The polypropylene insulation layer of the polypropylene insulated power cable prepared by this invention introduces silicon-oxygen-nitrogen hybrid polypropylene, enabling the polymer molecular chains to form a stable cross-linked network structure through silicon-oxygen and silicon-nitrogen bonds. This significantly improves the dimensional stability and heat deformation resistance of the material at high temperatures. Simultaneously, the added modified core-shell carbonitride is uniformly dispersed in the polypropylene matrix, constructing continuous microscopic thermal conductivity channels, effectively improving the heat conduction efficiency within the material and preventing localized overheating. A small amount of β-nucleating agent is used to regulate the crystal morphology, refine spherulites, and increase crystallinity, allowing the material to maintain a more stable physical state in high-temperature environments. The synergistic effect of various additives inhibits thermo-oxidative aging and reduces the adverse effects of interface defects on heat conduction. Ultimately, through the rational matching of the matrix, modified polymer, and inorganic filler, the polypropylene insulation layer achieves a simultaneous improvement in thermal conductivity and thermal stability, ensuring the safety and reliability of the cable during long-term operation.

[0048] 3. The polypropylene insulation layer of the polypropylene insulated power cable prepared by this invention introduces silicon-oxygen-nitrogen heteropolymer polypropylene, which forms silicon-oxygen bonds and silicon-nitrogen bonds between molecular chains, significantly reducing polarization defects and inhibiting carrier migration under high field strength, thereby enhancing dielectric strength. The modified core-shell carbonitride is uniformly dispersed in the polypropylene matrix, forming a stable interface structure, which not only avoids the generation of conductive channels, but also effectively blocks the accumulation and penetration of micro-charges through the interface barrier effect. With the introduction of a small amount of antioxidant and nucleating agent, the purity and crystal integrity of the material are further improved, reducing the adverse effects of free volume and impurity ions on insulation performance. Finally, through the synergistic regulation of the matrix polypropylene, modified polymer and functional filler, the polypropylene insulation layer maintains high resistivity while possessing excellent dielectric strength and stability, thus providing a guarantee for reliable insulation of the cable during long-term operation. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a three-dimensional structural diagram of the liquid-cooled cable prepared according to the present invention;

[0051] In the diagram: 1. Aluminum alloy conductor layer; 2. Conductor shielding layer; 3. Polypropylene insulation layer; 4. Insulating shielding layer; 5. Metal shielding layer; 6. Wrapping layer; 7. Outer sheath layer. Detailed Implementation

[0052] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] In this application, the polypropylene β-nucleating agent used was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd., item number PA46111; the polyvinylpyrrolidone used was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., item number P110607; the polypropylene used was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., item number P110849; the carbon black used was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., item number C742510; the calcium stearate used was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., item number C113301; and the polyvinyl chloride used was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., item number P107107.

[0054] Example 1

[0055] This embodiment provides a method for preparing a modified core-shell carbonitride, comprising the following steps:

[0056] Step ①: Preparation of alkynyl Schiff base

[0057] Weigh out 20.0 g of dimethylaminopropylamine, 20.0 g of 4-ethynylbenzaldehyde, and 400.0 mL of anhydrous ethanol and add them to a reaction vessel. Adjust the pH of the reaction system to 4 using 1 mol / L hydrochloric acid-ethanol solution. Raise the temperature of the reaction vessel to 40 °C and stir for 4 h. After the reaction is complete, transfer the reaction solution to a rotary evaporator at 40 °C. After removing the solvent under reduced pressure, add 20 times the mass of deionized water to the residue. After precipitation is complete, filter the residue and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and then transfer the filter cake to a drying oven at 40 °C and vacuum dry it to constant weight to obtain an ethynyl Schiff base.

[0058] Step 2: Preparation of metal coordination polymers

[0059] Weigh out 20.0 g of alkynyl Schiff base, 8.0 g of zinc chloride, 4.0 g of copper chloride, 4.0 g of polyvinylpyrrolidone, and 2000.0 mL of anhydrous ethanol and add them to a reaction vessel. After purging with nitrogen, raise the temperature of the reaction vessel to 60 °C and keep it at this temperature with stirring for 6 h. After the reaction is complete, centrifuge the reaction liquid to collect the gel. Replace the gel three times with three times its mass of anhydrous ethanol, each time for 6 h. After each replacement, transfer the gel to a drying oven at 60 °C and vacuum dry it to constant weight to obtain the metal coordination polymer.

[0060] Step 3: Preparation of a nitrogen-doped carbon core-shell metal

[0061] Weigh 20.0g of metal coordination polymer solid and place it in a quartz boat. After purging the air by introducing nitrogen into the muffle furnace, continue to introduce nitrogen and transfer the quartz boat into the muffle furnace. Heat the muffle furnace to 650℃ at a heating rate of 3℃ / min and hold for 30min. Then cool the muffle furnace to room temperature and remove the quartz boat. Collect the powder material to obtain a metal nitrogen-doped carbon core and shell.

[0062] Step 4: Preparation of modified core-shell carbonitride

[0063] Weigh out 8.0 g of nitrogen-doped carbon core-shell, 18.0 mL of N,N-dimethylformamide, 0.2 g of trimethylsilyl azide, and 0.2 g of propenyl trifluorochlorosilane and add them to the reaction vessel. After purging with nitrogen for protection, the temperature of the reaction vessel is raised to 60 °C and kept at that temperature for 4 h. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid to collect the filter cake, wash the filter cake three times with anhydrous ethanol, and then transfer the filter cake to a drying oven at 80 °C and vacuum dry it to constant weight to obtain the modified core-shell carbon-nitrogen body.

[0064] Example 2

[0065] This embodiment provides a method for preparing a modified core-shell carbonitride, comprising the following steps:

[0066] Step ①: Preparation of alkynyl Schiff base

[0067] Weigh out 24.0 g of dimethylaminopropylamine, 24.0 g of 4-ethynylbenzaldehyde, and 400.0 mL of anhydrous ethanol and add them to a reaction vessel. Adjust the pH of the reaction system to 4 using 1 mol / L hydrochloric acid-ethanol solution. Raise the temperature of the reaction vessel to 60 °C and stir for 6 h. After the reaction is complete, transfer the reaction solution to a rotary evaporator at 40 °C. After removing the solvent under reduced pressure, add 20 times the mass of deionized water to the residue. After precipitation is complete, filter the residue and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and then transfer the filter cake to a drying oven at 40 °C and vacuum dry it to constant weight to obtain an ethynyl Schiff base.

[0068] Step 2: Preparation of metal coordination polymers

[0069] Weigh out 20.0 g of alkynyl Schiff base, 8.0 g of zinc chloride, 6.0 g of copper chloride, 4.0 g of polyvinylpyrrolidone, and 2000.0 mL of anhydrous ethanol and add them to a reaction vessel. After purging with nitrogen, raise the temperature of the reaction vessel to 80 °C and keep it at this temperature with stirring for 8 h. After the reaction is complete, centrifuge the reaction liquid to collect the gel. Replace the gel three times with three times its mass of anhydrous ethanol, each time for 8 h. Transfer the gel to a drying oven at 60 °C and vacuum dry it to constant weight to obtain the metal coordination polymer.

[0070] Step 3: Preparation of a nitrogen-doped carbon core-shell metal

[0071] Weigh 20.0g of metal coordination polymer solid and place it in a quartz boat. After purging the air by introducing nitrogen into the muffle furnace, continue to introduce nitrogen and transfer the quartz boat into the muffle furnace. Heat the muffle furnace to 700℃ at a heating rate of 5℃ / min and hold for 40min. Then cool the muffle furnace to room temperature and remove the quartz boat. Collect the powder material to obtain a metal nitrogen-doped carbon core and shell.

[0072] Step 4: Preparation of modified core-shell carbonitride

[0073] Weigh out 10.0g of nitrogen-doped carbon core-shell, 20.0mL of N,N-dimethylformamide, 0.3g of trimethylsilyl azide, and 0.3g of propenyl trifluorochlorosilane and add them to the reaction vessel. After nitrogen protection, the temperature of the reaction vessel is raised to 80℃ and kept at that temperature for 6h. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and then transfer the filter cake to a drying oven at 80℃ and vacuum dry it to constant weight to obtain the modified core-shell carbon-nitrogen body.

[0074] Example 3

[0075] This embodiment provides a method for preparing a modified core-shell carbonitride, comprising the following steps:

[0076] Step ①: Preparation of alkynyl Schiff base

[0077] Weigh out 21.0 g of dimethylaminopropylamine, 21.0 g of 4-ethynylbenzaldehyde, and 400.0 mL of anhydrous ethanol and add them to a reaction vessel. Adjust the pH of the reaction system to 4 using 1 mol / L hydrochloric acid-ethanol solution. Raise the temperature of the reaction vessel to 50 °C and stir for 5 h. After the reaction is complete, transfer the reaction solution to a rotary evaporator at 40 °C. After removing the solvent under reduced pressure, add 20 times the mass of deionized water to the residue. After precipitation is complete, filter the residue and collect the filter cake. Wash the filter cake four times with anhydrous ethanol and then transfer the filter cake to a drying oven at 40 °C and vacuum dry it to constant weight to obtain an ethynyl Schiff base.

[0078] Step 2: Preparation of metal coordination polymers

[0079] Weigh out 20.0 g of alkynyl Schiff base, 8.0 g of zinc chloride, 5.0 g of copper chloride, 4.0 g of polyvinylpyrrolidone, and 2000.0 mL of anhydrous ethanol and add them to a reaction vessel. After purging with nitrogen, raise the temperature of the reaction vessel to 70 °C and keep it at this temperature with stirring for 7 h. After the reaction is complete, centrifuge the reaction liquid to collect the gel. Replace the gel three times with three times its mass of anhydrous ethanol, each time for 7 h. Transfer the gel to a drying oven at 60 °C and vacuum dry it to constant weight to obtain the metal coordination polymer.

[0080] Step 3: Preparation of a nitrogen-doped carbon core-shell metal

[0081] Weigh 20.0g of metal coordination polymer solid and place it in a quartz boat. After purging the air by introducing nitrogen into the muffle furnace, continue to introduce nitrogen and transfer the quartz boat into the muffle furnace. Heat the muffle furnace to 680℃ at a heating rate of 4℃ / min and hold for 35min. Then cool the muffle furnace to room temperature and remove the quartz boat. Collect the powder material to obtain a metal nitrogen-doped carbon core and shell.

[0082] Step 4: Preparation of modified core-shell carbonitride

[0083] Weigh out 9.0 g of nitrogen-doped carbon core-shell, 20.0 mL of N,N-dimethylformamide, 0.3 g of trimethylsilyl azide, and 0.3 g of propenyl trifluorochlorosilane and add them to the reaction vessel. After nitrogen protection, the temperature of the reaction vessel is raised to 70 °C and kept at that temperature for 5 h. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake four times with anhydrous ethanol and then transfer the filter cake to a drying oven at 80 °C and vacuum dry it to constant weight to obtain the modified core-shell carbon-nitrogen body.

[0084] Example 4

[0085] This embodiment provides a method for preparing siloxane-nitrogen polypropylene, including the following steps:

[0086] Step I: Preparation of anhydride-grafted polypropylene

[0087] 100.0g polypropylene, 10.0g maleic anhydride, 6.0g γ-aminopropyltriethoxysilane, 4.0g vinyltriethoxysilane, and 2.0g di-tert-butyl peroxide were added to the extruder. Under nitrogen protection, the extruder temperature was raised to 190℃ and the shear rate was maintained for 150s. -1 The material is kept at a constant temperature and sheared for 2 minutes. After shearing, the material is extruded to obtain an extrudate. The extrudate is naturally cooled to room temperature and crushed through an 80-mesh sieve to obtain anhydride-grafted polypropylene.

[0088] Step II: Preparation of silicon-oxygen-nitrogen polypropylene

[0089] Weigh out 40.0 g of anhydride-grafted polypropylene, 500.0 mL of anhydrous ethanol and 100.0 mL of deionized water and add them to the reaction vessel. After adjusting the pH of the reaction system to 4 with acetic acid, raise the temperature of the reaction vessel to 50 °C and keep it at this temperature for 8 h with stirring. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake three times with anhydrous ethanol and then transfer the filter cake to a drying oven at 80 °C and vacuum dry it to constant weight to obtain silicon-oxygen-nitrogen hybrid polypropylene.

[0090] Example 5

[0091] This embodiment provides a method for preparing siloxane-nitrogen polypropylene, including the following steps:

[0092] Step I: Preparation of anhydride-grafted polypropylene

[0093] 120.0g polypropylene, 10.0g maleic anhydride, 8.0g γ-aminopropyltriethoxysilane, 4.0g vinyltriethoxysilane, and 2.0g di-tert-butyl peroxide were added to the extruder. Under nitrogen protection, the extruder temperature was raised to 210℃ and the shear rate was maintained for 200s. -1 The material is kept at a constant temperature and sheared for 3 minutes. After shearing, the material is extruded to obtain an extrudate. The extrudate is naturally cooled to room temperature and crushed through an 80-mesh sieve to obtain anhydride-grafted polypropylene.

[0094] Step II: Preparation of silicon-oxygen-nitrogen polypropylene

[0095] Weigh out 50.0 g of anhydride-grafted polypropylene, 500.0 mL of anhydrous ethanol and 100.0 mL of deionized water and add them to the reaction vessel. After adjusting the pH of the reaction system to 4 with acetic acid, raise the temperature of the reaction vessel to 60 °C and keep it at this temperature for 10 h with stirring. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake 5 times with anhydrous ethanol and then transfer the filter cake to a drying oven at 80 °C and vacuum dry it to constant weight to obtain silicon-oxygen-nitrogen hybrid polypropylene.

[0096] Example 6

[0097] This embodiment provides a method for preparing siloxane-nitrogen polypropylene, including the following steps:

[0098] Step I: Preparation of anhydride-grafted polypropylene

[0099] 120.0g polypropylene, 10.0g maleic anhydride, 7.0g γ-aminopropyltriethoxysilane, 4.0g vinyltriethoxysilane, and 2.0g di-tert-butyl peroxide were added to the extruder. Under nitrogen protection, the extruder temperature was raised to 200℃ and the shear rate was maintained for 180s. -1 The material is kept at a constant temperature and sheared for 3 minutes. After shearing, the material is extruded to obtain an extrudate. The extrudate is naturally cooled to room temperature and crushed through an 80-mesh sieve to obtain anhydride-grafted polypropylene.

[0100] Step II: Preparation of silicon-oxygen-nitrogen polypropylene

[0101] Weigh out 45.0 g of anhydride-grafted polypropylene, 500.0 mL of anhydrous ethanol and 100.0 mL of deionized water and add them to the reaction vessel. After adjusting the pH of the reaction system to 4 with acetic acid, raise the temperature of the reaction vessel to 55 °C and keep it at this temperature for 9 h with stirring. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Wash the filter cake 4 times with anhydrous ethanol and then transfer the filter cake to a drying oven at 80 °C and vacuum dry it to constant weight to obtain silicon-oxygen-nitrogen hybrid polypropylene.

[0102] Example 7

[0103] This embodiment provides a method for preparing a polypropylene insulated power cable, including the following steps:

[0104] Step 1: Prepare the aluminum alloy conductor layer

[0105] An aluminum alloy with an aluminum-copper weight ratio of 99:1 was used to process and prepare an aluminum alloy conductor layer 1 with a cross-sectional length of 15 mm, a width of 3 mm, and a corner radius of R=1 mm.

[0106] Step 2: Prepare the conductor shielding layer

[0107] Polypropylene and carbon black were mixed at a weight ratio of 100:3 and then melt-extruded onto the surface of an aluminum alloy conductor layer. After natural curing, a conductor shielding layer 2 with a thickness of 0.8 mm was obtained.

[0108] Step 3: Preparation of polypropylene insulation layer

[0109] By weight, 80 parts of polypropylene, 10 parts of the siloxane-nitro polypropylene prepared in Example 4, 3 parts of the modified core-shell carbonitride prepared in Example 1, 0.1 parts of dioctadecyl thiodipropionate, 0.1 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.1 parts of calcium stearate and 0.2 parts of polypropylene β nucleating agent were melt-extruded onto the surface of the conductor shielding layer 2 and naturally cured to obtain a polypropylene insulation layer 3 with a thickness of 3.5 mm.

[0110] Step 4: Prepare the insulating shielding layer

[0111] Polyvinyl chloride, calcium stearate and carbon black are mixed in a weight ratio of 100:0.5:3 and then melt-extruded onto the surface of polypropylene insulation layer 3. After natural curing, an insulation shielding layer 4 with a thickness of 0.5 mm is obtained.

[0112] Step 5: Prepare the metal shielding layer

[0113] Copper strips are wrapped around the surface of the insulating shielding layer to obtain the surface of the insulating shielding layer 4, resulting in a metal shielding layer 5 with a thickness of 0.15 mm.

[0114] Step 6: Prepare the cladding layer

[0115] Polyurethane wrapping tape is wrapped around the surface of the metal shielding layer 5 to obtain the wrapping layer 6.

[0116] Step 7: Prepare the outer sheath layer

[0117] Polyvinyl chloride and calcium stearate are mixed in a weight ratio of 100:3 and then melt-extruded onto the surface of the wrapping layer 6. After natural curing, the outer sheath layer 7 is obtained, which is the polypropylene insulated power cable.

[0118] Example 8

[0119] This embodiment provides a method for preparing a polypropylene insulated power cable, including the following steps:

[0120] Step 1: Prepare the aluminum alloy conductor layer

[0121] An aluminum alloy with an aluminum-copper weight ratio of 99:1 was used to process and prepare an aluminum alloy conductor layer 1 with a cross-sectional length of 15 mm, a width of 3 mm, and a corner radius of R=1 mm.

[0122] Step 2: Prepare the conductor shielding layer

[0123] Polypropylene and carbon black were mixed at a weight ratio of 100:3 and then melt-extruded onto the surface of an aluminum alloy conductor layer. After natural curing, a conductor shielding layer 2 with a thickness of 0.8 mm was obtained.

[0124] Step 3: Preparation of polypropylene insulation layer

[0125] By weight, 90 parts of polypropylene, 15 parts of the siloxane-nitro polypropylene prepared in Example 5, 5 parts of the modified core-shell carbonitride prepared in Example 2, 0.3 parts of dioctadecyl thiodipropionate, 0.3 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.2 parts of calcium stearate, and 0.3 parts of polypropylene β-nucleating agent were melt-extruded onto the surface of the conductor shielding layer 2 and naturally cured to obtain a polypropylene insulation layer 3 with a thickness of 3.5 mm.

[0126] Step 4: Prepare the insulating shielding layer

[0127] Polyvinyl chloride, calcium stearate and carbon black are mixed in a weight ratio of 100:0.5:3 and then melt-extruded onto the surface of polypropylene insulation layer 3. After natural curing, an insulation shielding layer 4 with a thickness of 0.5 mm is obtained.

[0128] Step 5: Prepare the metal shielding layer

[0129] Copper strips are wrapped around the surface of the insulating shielding layer to obtain the surface of the insulating shielding layer 4, resulting in a metal shielding layer 5 with a thickness of 0.15 mm.

[0130] Step 6: Prepare the cladding layer

[0131] Polyurethane wrapping tape is wrapped around the surface of the metal shielding layer 5 to obtain the wrapping layer 6.

[0132] Step 7: Prepare the outer sheath layer

[0133] Polyvinyl chloride and calcium stearate are mixed in a weight ratio of 100:3 and then melt-extruded onto the surface of the wrapping layer 6. After natural curing, the outer sheath layer 7 is obtained, which is the polypropylene insulated power cable.

[0134] Example 9

[0135] This embodiment provides a method for preparing a polypropylene insulated power cable, including the following steps:

[0136] Step 1: Prepare the aluminum alloy conductor layer

[0137] An aluminum alloy with an aluminum-copper weight ratio of 99:1 was used to process and prepare an aluminum alloy conductor layer 1 with a cross-sectional length of 15 mm, a width of 3 mm, and a corner radius of R=1 mm.

[0138] Step 2: Prepare the conductor shielding layer

[0139] Polypropylene and carbon black were mixed at a weight ratio of 100:3 and then melt-extruded onto the surface of an aluminum alloy conductor layer. After natural curing, a conductor shielding layer 2 with a thickness of 0.8 mm was obtained.

[0140] Step 3: Preparation of polypropylene insulation layer

[0141] By weight, 88 parts of polypropylene, 12 parts of the siloxane-nitro polypropylene prepared in Example 6, 4 parts of the modified core-shell carbonitride prepared in Example 3, 0.2 parts of dioctadecyl thiodipropionate, 0.2 parts of tris(2,4-di-tert-butylphenyl) phosphite, 0.2 parts of calcium stearate and 0.3 parts of polypropylene β nucleating agent were melt-extruded onto the surface of the conductor shielding layer 2 and naturally cured to obtain a polypropylene insulation layer 3 with a thickness of 3.5 mm.

[0142] Step 4: Prepare the insulating shielding layer

[0143] Polyvinyl chloride, calcium stearate and carbon black are mixed in a weight ratio of 100:0.5:3 and then melt-extruded onto the surface of polypropylene insulation layer 3. After natural curing, an insulation shielding layer 4 with a thickness of 0.5 mm is obtained.

[0144] Step 5: Prepare the metal shielding layer

[0145] Copper strips are wrapped around the surface of the insulating shielding layer to obtain the surface of the insulating shielding layer 4, resulting in a metal shielding layer 5 with a thickness of 0.15 mm.

[0146] Step 6: Prepare the cladding layer

[0147] Polyurethane wrapping tape is wrapped around the surface of the metal shielding layer 5 to obtain the wrapping layer 6.

[0148] Step 7: Prepare the outer sheath layer

[0149] Polyvinyl chloride and calcium stearate are mixed in a weight ratio of 100:3 and then melt-extruded onto the surface of the wrapping layer 6. After natural curing, the outer sheath layer 7 is obtained, which is the polypropylene insulated power cable.

[0150] Comparative Example 1

[0151] The difference between this comparative example and Example 9 is that the use of siloxane-nitrogen polypropylene is omitted in step three.

[0152] Comparative Example 2

[0153] The difference between this comparative example and Example 9 is that the modified core-shell carbonitride is omitted in step three.

[0154] Comparative Example 3

[0155] The difference between this comparative example and Example 9 is that step ④ is omitted in the preparation of the modified core-shell carbonitride used in step 3.

[0156] Performance testing:

[0157] The electromagnetic shielding effectiveness of the polypropylene insulated power cables prepared in Examples 7-9 and Comparative Examples 1-3 was evaluated in accordance with the standard GB / T 32511-2016 "General Technical Requirements for Electromagnetic Shielding Plastics".

[0158] The heat distortion temperature rating of the polypropylene insulation layer in the polypropylene insulated power cables prepared in Examples 7-9 and Comparative Examples 1-3 was determined in accordance with the standard GB / T 32511-2016 "General Technical Requirements for Electromagnetic Shielding Plastics".

[0159] The thermal conductivity of the polypropylene insulation layer in the polypropylene insulated power cables prepared in Examples 7-9 and Comparative Examples 1-3 was determined according to the standard GB / T 10297-2015 "Determination of thermal conductivity of non-metallic solid materials - hot wire method".

[0160] The volume resistivity of the polypropylene insulation layer in the polypropylene insulated power cables prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 31838.2-2019 "Dielectric and resistive properties of solid insulating materials - Part 2: Resistive properties (DC method) - Volume resistivity and volume resistivity". The specific data are shown in Table 1.

[0161] Table 1 - Performance Test Data for Each Sample

[0162]

[0163] Data Analysis:

[0164] Comparative analysis of the data in Table 1 reveals that the electromagnetic shielding effectiveness of the polypropylene insulated power cable prepared by this invention is SE-1, and the heat distortion temperature rating of the polypropylene insulation layer is HDT-1 with a thermal conductivity of 0.38 W·(m·K). -1 At the same time, the volume resistivity is 1.6 × 10⁻⁶. 14 Ω·m, all data are better than the comparative example, indicating:

[0165] After losing the interface regulation brought about by the core-shell structure in Comparative Example 1, the thermal resistance of the filler-matrix interface increased significantly, phonon heat transfer was scattered, heat flow could not be connected, and hot spots were easily formed. At the same time, the interface barrier and deep trap density decreased, and charge carriers were more likely to migrate across the interface and accumulate locally, inducing space charge distortion and local field strength increase. Hot spots and high fields coupled with each other, promoting the propagation of microcracks and dielectric defects, and the breakdown path was opened in advance, which manifested as a synergistic decline in thermal conductivity, dielectric strength and operational stability.

[0166] In Comparative Example 2, after the loss of molecular-level silicon-oxygen / silicon-nitrogen bond construction, the chain segment constraint and network chemical anchoring weaken, the free volume and chain segment relaxation increase, the deformation recovery under thermal field is slow, and the chain cracking induced by thermo-oxidation is more likely to occur; at the same time, the trap energy level distribution becomes shallower, the charge trapping-release cycle intensifies, the accumulation of space charge leads to uneven field strength and increased dielectric loss, crystal defects are difficult to be suppressed by the network, the interface polarization is enhanced, and ultimately the thermal stability, electrical strength and long-term insulation life are systematically reduced;

[0167] The modified core-shell carbonitride particles used in Comparative Example 3 no longer introduce azide / allyl silicon-based active sites on their surface, making it difficult for them to undergo click / condensation and silicon-oxygen crosslinking with "anhydride-grafted PP / silicon-oxygen-nitrogen hybrid PP" during extrusion. As a result, the interface degenerates from chemical bridging to weak physical adsorption. Consequently, the dispersed phase is more prone to aggregation, interfacial voids and debonding increase, interfacial thermal resistance rises, and continuous thermal conduction channels are interrupted. Electrically, the density of deep traps and interfacial barriers decrease, interfacial polarization is enhanced, local field distortion and dielectric loss increase, thermo-electric synergy is destroyed, and the overall performance declines significantly.

[0168] Ultimately, this study demonstrates that the preparation of polypropylene insulated power cables incorporates modified core-shell carbonitride, silicon-oxygen-nitrogen hybrid polypropylene, and nucleation and shaping steps. Each component plays a role at different levels. The modified core-shell carbonitride provides stable thermal conductivity and charge regulation channels at the interface, improving local heat flow and field strength distribution. The silicon-oxygen-nitrogen hybrid polypropylene enhances crystal integrity and chain segment constraint through the chemical structure of molecular chains, reducing the risk of degradation under thermo-oxidative environments. Nucleation regulation enables the polypropylene matrix to achieve a more uniform and dense microstructure. These treatments create a systematic effect in terms of thermal conductivity, dielectric stability, and electromagnetic shielding, maintaining high levels of performance in the cable in terms of thermal conductivity, volume resistivity, and shielding effectiveness. The comparative results show that removing or simplifying any of these components significantly reduces the overall performance, indicating that the rational combination of the various components in this material system is crucial for achieving the desired performance.

[0169] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high-current aluminum alloy conductor, polypropylene insulated medium-voltage power cable, characterized in that, It includes an aluminum alloy conductor layer (1), a conductor shielding layer (2), and a polypropylene insulation layer (3) arranged from the inside out; The aluminum alloy conductor layer (1) is made of aluminum-copper alloy with an aluminum-copper weight ratio of 99:1, a cross-sectional length of 15mm, a width of 3mm, and a rounded corner transition of R=1mm. The conductor shielding layer (2) has a thickness of 0.8 mm and is obtained by melting and extruding a mixture of polypropylene and carbon black in a weight ratio of 100:3 onto the surface of the aluminum alloy conductor layer (1) and then allowing it to cure naturally. The polypropylene insulation layer (3) has a thickness of 3.5 mm and is obtained by melt extrusion of composite polypropylene material onto the surface of conductor shielding layer (2) and natural curing. The composite polypropylene material comprises the following raw materials in parts by weight: 80-90 parts polypropylene, 10-15 parts siloxane-nitro polypropylene, 3-5 parts modified core-shell carbonitride, 0.1-0.3 parts antioxidant, 0.1-0.3 parts heat stabilizer, 0.1-0.2 parts lubricant and 0.2-0.3 parts polypropylene β nucleating agent.

2. The high-current aluminum alloy conductor, polypropylene insulated medium-voltage power cable according to claim 1, characterized in that, The preparation method of the aforementioned siloxane-nitro polypropylene includes the following steps: A1. Add polypropylene, maleic anhydride, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and di-tert-butyl peroxide to the extruder. Under nitrogen protection, raise the extruder temperature to 190-210℃ and maintain the shear rate at 150-200s. -1 Heat-shear for 2-3 minutes, and then post-process to obtain anhydride-grafted polypropylene; A2. Add anhydride-grafted polypropylene, anhydrous ethanol and deionized water to a reaction vessel. Adjust the pH of the reaction system to 4-5 using acetic acid, then raise the temperature of the reaction vessel to 50-60℃ and keep it at this temperature for 8-10 hours with stirring. Post-treatment yields silicon-oxygen-nitrogen hybrid polypropylene.

3. A high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable according to claim 2, characterized in that, In step A1, the ratio of polypropylene, maleic anhydride, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and di-tert-butyl peroxide is 10-12 g: 1 g: 0.6-0.8 g: 0.4 g: 0.2 g; in step A2, the ratio of anhydride-grafted polypropylene, anhydrous ethanol, and deionized water is 4-5 g: 50 mL: 10 mL.

4. A high-current aluminum alloy conductor, polypropylene insulated medium-voltage power cable according to claim 1, characterized in that, The method for preparing the modified core-shell carbon-nitrogen body includes the following steps: B1. Place the metal coordination polymer solid in a quartz boat, introduce nitrogen into the muffle furnace to purge the air, keep the nitrogen inlet and transfer the quartz boat into the muffle furnace, raise the temperature of the muffle furnace to 650-700℃ and hold for 30-40 min, and then perform post-processing to obtain a metal nitrogen-doped carbon core and shell. B2. Add the nitrogen-doped carbon core and shell, N,N-dimethylformamide, trimethylsilyl azide and propylene trifluorochlorosilane to the reactor, purge with nitrogen, raise the temperature of the reactor to 60-80℃ and keep it at that temperature for 4-6 hours, and then proceed with the post-treatment to obtain the modified core-shell carbonitride.

5. A high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable according to claim 4, characterized in that, In step B1, the heating rate of the muffle furnace is 3-5℃ / min; in step B2, the ratio of the amount of metal nitrogen-doped carbon core and shell, N,N-dimethylformamide, trimethylsilyl azide and propylene trifluorochlorosilane is 8-10g:18-20mL:0.2-0.3g:0.2-0.3g.

6. A high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable according to claim 4, characterized in that, The preparation method of the metal coordination polymer includes the following steps: C1. Dimethylaminopropylamine, 4-ethynylbenzaldehyde and anhydrous ethanol are added to a reaction vessel. The pH of the reaction system is adjusted to 4-5 using 1 mol / L hydrochloric acid ethanol solution. The temperature of the reaction vessel is raised to 40-60℃ and stirred for 4-6 hours. The ethynyl Schiff base is then obtained after post-treatment. C2. Add alkynyl Schiff base, zinc chloride, copper chloride, polyvinylpyrrolidone and anhydrous ethanol to the reactor. After purging with nitrogen, raise the temperature of the reactor to 60-80℃ and keep it at this temperature for 6-8 hours with stirring. Post-treatment yields the metal coordination polymer.

7. A high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable according to claim 6, characterized in that, In step C1, the ratio of dimethylaminopropylamine, 4-ethynylbenzaldehyde, and anhydrous ethanol is 5-6 g: 5-6 g: 100 mL; in step C2, the ratio of alkynyl Schiff base, zinc chloride, copper chloride, polyvinylpyrrolidone, and anhydrous ethanol is 1 g: 0.4 g: 0.2-0.3 g: 0.2 g: 100 mL.

8. A high-current aluminum alloy conductor polypropylene insulated medium-voltage power cable according to claim 1, characterized in that, The polypropylene insulation layer (3) is provided with an insulating shielding layer (4), a metal shielding layer (5), a wrapping layer (6), and an outer sheath layer (7) in sequence.

9. A high-current aluminum alloy conductor, polypropylene insulated medium-voltage power cable according to claim 1, characterized in that, The insulating shielding layer (4) has a thickness of 0.5 mm and is obtained by melting and extruding a mixture of polyvinyl chloride, calcium stearate and carbon black in a weight ratio of 100:0.5:3 onto the surface of the polypropylene insulating layer (3) and then curing it naturally. The metal shielding layer (5) has a thickness of 0.15 mm and is obtained by wrapping copper tape around the surface of the insulating shielding layer (4). The wrapping layer (6) has a thickness of 1.2 mm and is obtained by wrapping polyurethane wrapping tape around the surface of the metal shielding layer (5). The outer sheath layer (7) has a thickness of 1.8 mm and is obtained by melting and extruding a mixture of polyvinyl chloride and calcium stearate in a weight ratio of 100:3 onto the surface of the wrapping layer (6) and then curing it naturally.

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