A crosslinked polyethylene insulated power cable suitable for underground laying

Abstract

The application relates to the technical field of power cables, and discloses a cross-linked polyethylene insulated power cable suitable for underground laying. The cross-linked polyethylene insulated power cable comprises, from inside to outside, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, an inner sheath layer, an armor layer and an outer sheath layer; the power cable is protected by a double-layer sheath mode, wherein the inner sheath layer can protect the insulation layer and the shielding layer from mechanical damage, and can cooperate with the armor layer and the outer sheath to form a complete protection system; and the outer sheath layer can significantly improve the comprehensive performance of the outer sheath in a harsh underground environment through the synergistic effect of multiple mechanisms such as physical shielding, chemical repulsion, stress dispersion and dynamic repair.

Description

Technical Field

[0001] This invention relates to the field of power cable technology, and more specifically to a cross-linked polyethylene insulated power cable suitable for underground installation. Background Technology

[0002] Cross-linked polyethylene (XLPE) insulated power cables have become the mainstream choice for medium and high voltage power transmission due to their excellent electrical properties, heat resistance, and mechanical strength, especially in direct burial installations in urban power grids, industrial plants, and municipal engineering projects. To ensure long-term reliable operation of the cable in underground environments characterized by moisture, pressure, and large temperature variations, the outer sheath is typically made of high-density polyethylene or other polyolefin materials, requiring excellent resistance to environmental stress cracking, low water permeability, and chemical corrosion resistance.

[0003] However, in practical engineering applications, conventional polyethylene-based outer sheath materials still face several technical bottlenecks. First, while ordinary high-density polyethylene possesses high strength and water resistance, its resistance to environmental stress cracking is often insufficient. Second, conventional polyethylene sheaths have limited resistance to chemical media, and the sheath surface is easily corroded, accelerating aging. To improve these properties, existing technologies have attempted to modify polyethylene by adding elastomers, nanofillers, or compatibilizers, but it remains difficult to simultaneously meet the comprehensive requirements of high ESCR, low water permeability, chemical corrosion resistance, and good processability. Especially at high addition levels, problems such as filler agglomeration, poor interfacial bonding, and extrusion processing difficulties easily arise. Therefore, developing an outer sheath material for buried cables that combines excellent resistance to environmental stress cracking, water resistance, chemical corrosion resistance, and thermal conductivity has significant engineering application value. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a cross-linked polyethylene insulated power cable suitable for underground installation.

[0005] The objective of this invention can be achieved through the following technical solutions: A cross-linked polyethylene insulated power cable suitable for underground installation includes, from the inside out, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, an inner sheath layer, an armor layer, and an outer sheath layer. The inner sheath layer, by weight, is made by co-extrusion of 60-80 parts linear low-density polyethylene, 10-20 parts ethylene-vinyl acetate copolymer, 4-9 parts POE, 0.1-0.3 parts antioxidant and 0.5-1 parts lubricant; The outer sheath layer comprises the following raw materials in parts by weight: 35-55 parts linear high-density polyethylene, 10-20 parts linear low-density polyethylene, 15-20 parts ethylene-propylene copolymer, 4-7 parts composite reinforcing agent, 2-3 parts carbon black, 6-10 parts ammonium polyphosphate, 8-12 parts magnesium hydroxide, 5-8 parts maleic anhydride grafted polyethylene, 2-3 parts lubricant, 0.5-1 part antioxidant, and 1.5-2.5 parts coupling agent; Furthermore, the outer sheath layer is prepared by the following steps: Weigh the raw materials according to the weight parts, add linear high-density polyethylene, linear low-density polyethylene, ethylene-propylene copolymer and maleic anhydride grafted polyethylene into the mixer and mix for 3-5 minutes, then add composite reinforcing agent, carbon black, ammonium polyphosphate, magnesium hydroxide and coupling agent and mix for 5-8 minutes, finally add lubricant and antioxidant and mix for 1-2 minutes, extrude to obtain the outer sheath layer. Further, the composite reinforcing agent is prepared by the following steps: Step A1: Mix KH550, anhydrous ethanol and deionized water, stir at 55°C for 30 min, then add boron nitride (BN) powder and ball mill, then dry and grind to obtain pretreated BN; Furthermore, in step A1, the ratio of KH550, anhydrous ethanol, deionized water, and BN powder is 0.5-1.5 mL: 3-6 mL: 6-12 mL: 1 g; Step A2: Under nitrogen atmosphere, immerse the pretreated BN in KH560 and heat to 80℃ with stirring for 4-5 hours. Add anhydrous ethanol, KH570, a blend of functionalized silane and fluorosilane, and add deionized water dropwise. Adjust the pH to 4-5 and react at 60℃ for 4.5-6.5 hours. Wash and dry to obtain the composite reinforcing agent. Further, in step A2, the ratio of pretreatment BN, KH560, anhydrous ethanol, KH570, functionalized silane, fluorosilane, and deionized water is 1g:0.04-0.12mol:300mL:0.05-0.15mol:0.02-0.06mol:0.01-0.03mol:25-45mL; Further, the fluorosilane mentioned in step A2 is one of 1H,1H,2H,2H-nonafluorohexyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, or 1H,1H,2H,2H-heptafluorodecyltrimethoxysilane. Furthermore, the functionalized silane is prepared by the following steps: Step B1: Add phenylboronic acid to tetrahydrofuran and stir until homogeneous. Then add 1-thioglycerol and stir until homogeneous. Add anhydrous magnesium sulfate and stir for 24 hours. Filter under vacuum, collect the filtrate, evaporate by rotary evaporation and dry to obtain phenylboronic ester. Furthermore, in step B1, the ratio of phenylboronic acid, tetrahydrofuran, 1-thioglycerol, and anhydrous magnesium sulfate is 0.1-0.2 mol: 200 mL: 0.1-0.2 mol: 15-20 g; Step B2: Mix allyltriethoxysilane, phenylboronic acid ester and benzoin dimethyl ether evenly, then irradiate under 100W, 365nm ultraviolet light for 35-45 minutes. After the reaction is complete, add n-hexane to precipitate, and rotary evaporate to obtain functionalized silane. Furthermore, in step B2, the ratio of allyltriethoxysilane, phenylboronic acid ester, and benzoin dimethyl ether is 0.1-0.2 mol: 0.101-0.202 mol: 0.04-0.08 g.

[0006] The beneficial effects of this invention are: The cross-linked polyethylene insulated power cable of the present invention comprises, from the inside out, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, an inner sheath layer, an armor layer, and an outer sheath layer. The power cable adopts a double-layer sheath method to protect the cable. The inner sheath layer protects the insulation layer and shielding layer from mechanical damage internally, and works with the armor layer and outer sheath to form a three-dimensional protection system externally. The outer sheath layer can significantly improve the overall performance of the outer sheath in harsh underground buried environments through the synergistic effect of multiple mechanisms such as physical shielding, chemical repulsion, stress dispersion, and dynamic repair.

[0007] The outer sheath layer of this invention is made primarily of linear high-density polyethylene and linear low-density polyethylene, with the addition of compatibilizers, composite reinforcing agents, and other functional additives. The composite reinforcing agent introduced into this outer sheath layer improves its waterproof performance, chemical corrosion resistance, and environmental stress cracking resistance. The composite reinforcing agent is made by in-situ grafting functionalized organosilicon structures onto boron nitride nanosheets as a substrate. The boron nitride nanosheets, with their regular layered structure, are uniformly dispersed within the outer sheath, stacking like countless tiny "tiles," significantly extending the "maze path" for water molecules to diffuse into the cable's interior and effectively reducing the material's permeability. The functionalized organosilicon structure is also modified with fluorine segments, which have extremely low surface energy and exhibit strong hydrophobic and oleophobic properties. These fluorine segments accumulate on the material surface, forming a dense "molecular-level waterproof barrier," making it difficult for water molecules to wet and penetrate the sheath surface. Boron nitride nanosheets can also synergistically work with fluorine segments to effectively block the diffusion of acid, alkali, salt ions or organic solvents into the material, thereby improving the material's corrosion resistance. In addition, the functionalized organosilicon structure introduces phenylboronic acid ester rings with dynamic reversible properties. When the molecular chain breaks due to chemical corrosion, the phenylboronic acid ester bonds may undergo a dynamic exchange reaction of "breakage-recombination" under appropriate conditions. This endows the material with self-healing potential, which can maintain the integrity of the sheath structure and thus continuously resist corrosion.

[0008] The functionalized organosilicon on the outer layer of the composite reinforcing agent also has a certain branched structure and free double bonds. It forms a good physical entanglement with the polyethylene matrix or participates in chemical cross-linking. The flexible organosilicon molecular chain can stretch and orient under stress, effectively dispersing and absorbing external energy like a molecular spring. This structure of "rigid nanocenter + flexible polymer brush" can passivate the crack tip in a "rigid and flexible" way, prevent crack propagation, and thus improve the cable's resistance to environmental stress cracking. Detailed Implementation

[0009] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0010] Example 1: Functionalized silanes were prepared by the following steps: Step B1: Add 0.1 mol of phenylboronic acid to 200 mL of tetrahydrofuran and stir until homogeneous. Then add 0.1 mol of 1-thioglycerol and stir until homogeneous. Add 15 g of anhydrous magnesium sulfate and stir for 24 h. Filter under vacuum, collect the filtrate, evaporate by rotary evaporation and dry to obtain phenylboronic acid ester. Step B2: Mix 0.1 mol allyltriethoxysilane, 0.101 mol phenylboronic acid ester and 0.04 g benzoin dimethyl ether until homogeneous, then irradiate under 100 W, 365 nm ultraviolet light for 35 min. After the reaction is complete, add n-hexane to precipitate, and rotary evaporate to obtain functionalized silane.

[0011] The composite reinforcing agent is prepared by the following steps: Step A1: Mix 0.5 mL KH550, 3 mL anhydrous ethanol and 6 mL deionized water, stir at 55 °C for 30 min, then add 1 g boron nitride powder and ball mill, then dry and grind to obtain pretreated BN. Step A2: Under nitrogen atmosphere, 1g of pretreated BN was immersed in 0.04mol KH560 and heated to 80℃ with stirring for 4h. Then, a blend of 300mL anhydrous ethanol, 0.05mol KH570, 0.02mol functionalized silane, and 0.01mol 1H,1H,2H,2H-nonafluorohexyltrimethoxysilane was added dropwise, and 25mL deionized water was added dropwise to adjust the pH to 4. The mixture was then reacted at 60℃ for 4.5h. After washing and drying, the composite reinforcing agent was obtained.

[0012] Example 2: Functionalized silanes were prepared by the following steps: Step B1: Add 0.15 mol of phenylboronic acid to 200 mL of tetrahydrofuran and stir until homogeneous. Then add 0.15 mol of 1-thioglycerol and stir until homogeneous. Add 18 g of anhydrous magnesium sulfate and stir for 24 h. Filter under vacuum, collect the filtrate, evaporate by rotary evaporation and dry to obtain phenylboronic acid ester. Step B2: Mix 0.15 mol allyltriethoxysilane, 0.151 mol phenylboronic acid ester and 0.06 g benzoin dimethyl ether until homogeneous, then irradiate under 100 W, 365 nm ultraviolet light for 40 min. After the reaction is complete, add n-hexane to precipitate, and rotary evaporate to obtain functionalized silane.

[0013] The composite reinforcing agent is prepared by the following steps: Step A1: Mix 1 mL KH550, 4.5 mL anhydrous ethanol and 9 mL deionized water, stir at 55 °C for 30 min, then add 1 g boron nitride powder and ball mill, then dry and grind to obtain pretreated BN. Step A2: Under nitrogen atmosphere, 1g of pretreated BN was immersed in 0.08mol KH560 and heated to 80℃ with stirring for 4.5h. Then, a blend of 300mL anhydrous ethanol, 0.1mol KH570, 0.04mol functionalized silane and 0.02mol tridecafluorooctyltrimethoxysilane was added, and 35mL deionized water was added dropwise to adjust the pH to 4.5. The mixture was then reacted at 60℃ for 5.5h. After washing and drying, the composite reinforcing agent was obtained.

[0014] Example 3: Functionalized silanes were prepared by the following steps: Step B1: Add 0.2 mol of phenylboronic acid to 200 mL of tetrahydrofuran and stir until homogeneous. Then add 0.2 mol of 1-thioglycerol and stir until homogeneous. Add 20 g of anhydrous magnesium sulfate and stir for 24 h. Filter under vacuum, collect the filtrate, evaporate by rotary evaporation and dry to obtain phenylboronic acid ester. Step B2: Mix 0.2 mol allyltriethoxysilane, 0.202 mol phenylboronic acid ester and 0.08 g benzoin dimethyl ether until homogeneous, then irradiate under 100 W, 365 nm ultraviolet light for 45 min. After the reaction is complete, add n-hexane to precipitate, and rotary evaporate to obtain functionalized silane.

[0015] The composite reinforcing agent is prepared by the following steps: Step A1: Mix 1.5 mL KH550, 6 mL anhydrous ethanol and 12 mL deionized water, stir at 55 °C for 30 min, then add 1 g boron nitride powder and ball mill, then dry and grind to obtain pretreated BN. Step A2: Under nitrogen atmosphere, 1g of pretreated BN was immersed in 0.12mol KH560 and heated to 80℃ with stirring for 5h. Then, 300mL of anhydrous ethanol, 0.15mol KH570, 0.06mol of functionalized silane and 0.03mol of 1H,1H,2H,2H-heptadecyltrimethoxysilane were added dropwise, and 45mL of deionized water was added dropwise to adjust the pH to 5. The mixture was then reacted at 60℃ for 6.5h. After washing and drying, the composite reinforcing agent was obtained.

[0016] Example 4: A cross-linked polyethylene insulated power cable suitable for underground installation, comprising, from the inside out, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, an inner sheath layer, an armor layer, and an outer sheath layer; The inner sheath layer, by weight, is made by co-extrusion of 60 parts linear low-density polyethylene, 10 parts ethylene-vinyl acetate copolymer, 4 parts POE, 0.1 parts antioxidant and 0.5 parts lubricant; The outer sheath layer comprises the following raw materials in parts by weight: 35 parts linear high-density polyethylene, 10 parts linear low-density polyethylene, 15 parts ethylene-propylene copolymer, 4 parts composite reinforcing agent prepared in Example 1, 2 parts carbon black, 6 parts ammonium polyphosphate, 8 parts magnesium hydroxide, 5 parts maleic anhydride grafted polyethylene, 2 parts lubricant, 0.5 parts antioxidant, and 1.5 parts coupling agent. Preferably, the lubricant is polyethylene wax; Preferably, the antioxidants are all mixtures of antioxidant 1010 and antioxidant 168, and the mass ratio of the two is 1:1; Preferably, the coupling agent is a silane coupling agent KH560; Preferably, the outer sheath layer is prepared by the following steps: Weigh the raw materials according to the weight parts, add linear high-density polyethylene, linear low-density polyethylene, ethylene-propylene copolymer and maleic anhydride grafted polyethylene into the mixer and mix for 3 minutes, then add the composite reinforcing agent prepared in Example 1, carbon black, ammonium polyphosphate, magnesium hydroxide and coupling agent and mix for 5 minutes, finally add lubricant and antioxidant and mix for 1 minute, extrude to obtain the outer sheath layer.

[0017] Example 5: A cross-linked polyethylene insulated power cable suitable for underground installation, comprising, from the inside out, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, an inner sheath layer, an armor layer, and an outer sheath layer; The inner sheath layer, by weight, is made by co-extrusion of 70 parts linear low-density polyethylene, 15 parts ethylene-vinyl acetate copolymer, 6 parts POE, 0.2 parts antioxidant and 0.8 parts lubricant; The outer sheath layer comprises the following raw materials in parts by weight: 45 parts linear high-density polyethylene, 15 parts linear low-density polyethylene, 18 parts ethylene-propylene copolymer, 6 parts composite reinforcing agent prepared in Example 2, 2.5 parts carbon black, 8 parts ammonium polyphosphate, 10 parts magnesium hydroxide, 6.5 parts maleic anhydride grafted polyethylene, 2.5 parts lubricant, 0.8 parts antioxidant, and 2 parts coupling agent; Preferably, the lubricant is polyethylene wax; Preferably, the antioxidants are all mixtures of antioxidant 1010 and antioxidant 168, and the mass ratio of the two is 1:1; Preferably, the coupling agent is a silane coupling agent KH570; Preferably, the outer sheath layer is prepared by the following steps: Weigh the raw materials according to the weight parts, add linear high-density polyethylene, linear low-density polyethylene, ethylene-propylene copolymer and maleic anhydride grafted polyethylene into a mixer and mix for 4 minutes, then add the composite reinforcing agent prepared in Example 2, carbon black, ammonium polyphosphate, magnesium hydroxide and coupling agent and mix for 6.5 minutes, finally add lubricant and antioxidant and mix for 1.5 minutes, extrude to obtain the outer sheath layer.

[0018] Example 6: A cross-linked polyethylene insulated power cable suitable for underground installation, comprising, from the inside out, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, an inner sheath layer, an armor layer, and an outer sheath layer; The inner sheath layer, by weight, is made by co-extrusion of 80 parts linear low-density polyethylene, 20 parts ethylene-vinyl acetate copolymer, 9 parts POE, 0.3 parts antioxidant and 1 part lubricant; The outer sheath layer comprises the following raw materials in parts by weight: 55 parts of linear high-density polyethylene, 20 parts of linear low-density polyethylene, 20 parts of ethylene-propylene copolymer, 7 parts of the composite reinforcing agent prepared in Example 3, 3 parts of carbon black, 10 parts of ammonium polyphosphate, 12 parts of magnesium hydroxide, 8 parts of maleic anhydride grafted polyethylene, 3 parts of lubricant, 1 part of antioxidant, and 2.5 parts of coupling agent. Preferably, the lubricant is polyethylene wax; Preferably, the antioxidants are all mixtures of antioxidant 1010 and antioxidant 168, and the mass ratio of the two is 1:1; Preferably, the coupling agent is a silane coupling agent KH560; Preferably, the outer sheath layer is prepared by the following steps: Weigh the raw materials according to the weight parts, add linear high-density polyethylene, linear low-density polyethylene, ethylene-propylene copolymer and maleic anhydride grafted polyethylene into the mixer and mix for 5 minutes, then add the composite reinforcing agent prepared in Example 3, carbon black, ammonium polyphosphate, magnesium hydroxide and coupling agent and mix for 8 minutes, finally add lubricant and antioxidant and mix for 2 minutes, extrude to obtain the outer sheath layer.

[0019] Comparative Example 1: This comparative example is a cross-linked polyethylene insulated power cable. The difference between this example and Example 6 is that the composite reinforcing agent prepared in Example 3 was not added to the outer sheath layer. All other aspects are the same.

[0020] Comparative Example 2: This comparative example is a cross-linked polyethylene insulated power cable. The difference between this example and Example 6 is that boron nitride nanosheets are used instead of the composite reinforcing agent prepared in Example 3 in the outer sheath layer. All other aspects are the same.

[0021] Comparative Example 3: This comparative example is a cross-linked polyethylene insulated power cable. The difference from Example 6 is that in the composite reinforcing agent prepared in Example 3 for the outer sheath layer, tetraethyl orthosilicate is used instead of functionalized silane.

[0022] Comparative Example 4: This comparative example is a cross-linked polyethylene insulated power cable. The difference from Example 6 is that in the composite reinforcing agent prepared in Example 3 for the outer sheath layer, tetraethyl orthosilicate is used instead of fluorosilane.

[0023] Comparative Example 5: This comparative example is a cross-linked polyethylene insulated power cable. The difference from Example 6 is that in the composite reinforcing agent prepared in Example 3 for the outer sheath layer, tetraethyl orthosilicate is used instead of functionalized silane and fluorosilane.

[0024] The performance of the outer sheath of the cross-linked polyethylene insulated power cables prepared in Examples 4-6 and Comparative Examples 1-5 was tested: Flame retardant performance test: The oxygen index was determined according to GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics"; Corrosion resistance test: The power cable sample was immersed in 20wt% HCl solution, 20wt% NaOH solution, 20wt% NaCl solution and aqueous solution under the same conditions for 15 days. After immersion, the sample was taken out and the surface was observed to see if there were any bubbles or cracks. Environmental stress cracking resistance test: Refer to GB / T 1842-2008 "Test Method for Environmental Stress Cracking of Polyethylene" to test the cracking time of 50% of the specimen (F50). The test results are shown in Table 1: Table 1: Performance Test Results As can be seen from Table 1, the outer sheath of the cross-linked polyethylene insulated power cable of the present invention not only has excellent flame retardant properties, but also excellent corrosion resistance, water resistance and environmental stress cracking resistance.

[0025] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A cross-linked polyethylene insulated power cable suitable for underground installation, characterized in that, A cross-linked polyethylene insulated power cable suitable for underground installation includes, from the inside out, a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation shielding layer, an inner sheath layer, an armor layer, and an outer sheath layer. The inner sheath layer, by weight, is made by co-extrusion of 60-80 parts linear low-density polyethylene, 10-20 parts ethylene-vinyl acetate copolymer, 4-9 parts POE, 0.1-0.3 parts antioxidant and 0.5-1 parts lubricant; The outer sheath layer comprises the following raw materials in parts by weight: 35-55 parts linear high-density polyethylene, 10-20 parts linear low-density polyethylene, 15-20 parts ethylene-propylene copolymer, 4-7 parts composite reinforcing agent, 2-3 parts carbon black, 6-10 parts ammonium polyphosphate, 8-12 parts magnesium hydroxide, 5-8 parts maleic anhydride grafted polyethylene, 2-3 parts lubricant, 0.5-1 part antioxidant, and 1.5-2.5 parts coupling agent; The composite reinforcing agent is prepared by grafting functionalized organosilicon onto the surface of boron nitride as a base; the functionalized organosilicon is prepared by using KH560, KH570, functionalized silane and fluorosilane as raw materials; the functionalized silane is prepared by reacting allyltriethoxysilane and phenylboronic acid ester; the phenylboronic acid ester is prepared by reacting phenylboronic acid and 1-thioglycerol.

2. The cross-linked polyethylene insulated power cable suitable for underground installation according to claim 1, characterized in that, The outer sheath layer is prepared by the following steps: Weigh the raw materials according to the weight proportions, add linear high-density polyethylene, linear low-density polyethylene, ethylene-propylene copolymer and maleic anhydride grafted polyethylene into the mixer and mix for 3-5 minutes, then add composite reinforcing agent, carbon black, ammonium polyphosphate, magnesium hydroxide and coupling agent and mix for 5-8 minutes, finally add lubricant and antioxidant and mix for 1-2 minutes, extrude to obtain the outer sheath layer.

3. A cross-linked polyethylene insulated power cable suitable for underground installation according to claim 1, characterized in that, The composite reinforcing agent is prepared by the following steps: Step A1: Mix KH550, anhydrous ethanol and deionized water, stir at 55°C for 30 min, then add boron nitride powder and ball mill, then dry and grind to obtain pretreated BN. Step A2: Under nitrogen atmosphere, immerse the pretreated BN in KH560 and heat to 80℃ with stirring for 4-5 hours. Add anhydrous ethanol, KH570, a blend of functionalized silane and fluorosilane, and add deionized water dropwise. Adjust the pH to 4-5 and react at 60℃ for 4.5-6.5 hours. Wash and dry to obtain the composite reinforcing agent.

4. A cross-linked polyethylene insulated power cable suitable for underground installation according to claim 3, characterized in that, In step A1, the ratio of KH550, anhydrous ethanol, deionized water, and BN powder is 0.5-1.5 mL: 3-6 mL: 6-12 mL: 1 g.

5. A cross-linked polyethylene insulated power cable suitable for underground installation according to claim 3, characterized in that, In step A2, the ratio of pretreatment BN, KH560, anhydrous ethanol, KH570, functionalized silane, fluorosilane and deionized water is 1g:0.04-0.12mol:300mL:0.05-0.15mol:0.02-0.06mol:0.01-0.03mol:25-45mL.

6. A cross-linked polyethylene insulated power cable suitable for underground installation according to claim 3, characterized in that, The fluorosilane mentioned in step A2 is one of 1H,1H,2H,2H-nonafluorohexyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, or 1H,1H,2H,2H-heptafluorodecyltrimethoxysilane.

7. A cross-linked polyethylene insulated power cable suitable for underground installation according to claim 3, characterized in that, The functionalized silane is prepared by the following steps: Step B1: Add phenylboronic acid to tetrahydrofuran and stir until homogeneous. Then add 1-thioglycerol and stir until homogeneous. Add anhydrous magnesium sulfate and stir for 24 hours. Filter under vacuum, collect the filtrate, evaporate by rotary evaporation and dry to obtain phenylboronic ester. Step B2: Mix allyltriethoxysilane, phenylboronic acid ester and benzoin dimethyl ether until homogeneous, then irradiate under 100W, 365nm ultraviolet light for 35-45 minutes. After the reaction is complete, add n-hexane to precipitate, and rotary evaporate to obtain functionalized silane.

8. A cross-linked polyethylene insulated power cable suitable for underground installation according to claim 7, characterized in that, Furthermore, in step B1, the ratio of phenylboronic acid, tetrahydrofuran, 1-thioglycerol, and anhydrous magnesium sulfate is 0.1-0.2 mol: 200 mL: 0.1-0.2 mol: 15-20 g.

9. A cross-linked polyethylene insulated power cable suitable for underground installation according to claim 7, characterized in that, In step B2, the ratio of allyltriethoxysilane, phenylboronic acid ester, and benzoin dimethyl ether is 0.1-0.2 mol: 0.101-0.202 mol: 0.04-0.08 g.

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