Crosslinked polyethylene insulated moisture resistant aerial cable

Abstract

This invention relates to the field of cable technology and discloses a cross-linked polyethylene insulated moisture-proof overhead cable. The cable comprises: a core conductor, a conductor shielding layer, a multifunctional composite insulation layer, an insulation shielding layer, and an outer sheath; the multifunctional composite insulation layer, from the inside out, comprises: a charge suppression and bonding layer, a self-healing insulation main layer, and an outer protective hydrophobic layer. Through the above technical solution, this invention can achieve stable moisture-proof insulation performance throughout the cable's entire life cycle, prevent insulation degradation and water treeing caused by moisture intrusion, and effectively extend the cable's service life.

Description

Technical Field

[0001] This invention belongs to the field of cable technology and relates to a cross-linked polyethylene insulated moisture-proof overhead cable. Background Technology

[0002] Overhead cables play a crucial role in modern society as an important carrier of electricity transmission. With the continuous growth of electricity demand and the increasing complexity of application scenarios, higher requirements are being placed on the performance of overhead cables. Traditional cross-linked polyethylene insulated overhead cables have certain limitations in dealing with humid environments. In areas with high humidity or long-term exposure to harsh natural conditions, moisture can easily penetrate the cable's interior through tiny gaps or damage in the outer layer.

[0003] Moisture intrusion can lead to decreased insulation performance, causing safety hazards such as leakage and short circuits, and seriously affecting the stability and reliability of power transmission. Simultaneously, moisture can accelerate the corrosion of the internal metal conductors of the cable, shortening its service life and increasing maintenance costs. Furthermore, existing moisture-proofing measures are often of limited effectiveness, failing to fundamentally solve the problem of moisture intrusion, or increasing the weight and cost of the cable during implementation, hindering large-scale application. Therefore, developing a cross-linked polyethylene insulated overhead cable with highly efficient moisture-proof performance, a reasonable structure, and controllable cost is of significant practical importance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a cross-linked polyethylene insulated moisture-proof overhead cable, which aims to solve the technical contradictions caused by the increase in structural complexity, manufacturing cost, and moisture-proof performance degradation after aging of interlayer interfaces when traditional overhead cables improve moisture-proof performance by adding an independent moisture-proof layer.

[0005] To achieve the above-mentioned objectives, the present invention provides a cross-linked polyethylene insulated moisture-proof overhead cable, comprising, from the inside out, a cable core conductor, a conductor shielding layer, a multifunctional composite insulation layer, and an outer sheath for the insulation shielding layer, characterized in that:

[0006] The multifunctional composite insulation layer is an integrated composite structure formed in one step through a three-layer co-extrusion process, which includes, from the inside out: a charge suppression and bonding layer, a self-healing insulation main layer, and an outer protective hydrophobic layer.

[0007] Preferably, the charge suppression and bonding layer is an insulating sublayer that is in direct contact with the outer surface of the conductor shielding layer. The base polymer of the charge suppression and bonding layer is low-density polyethylene, and maleic anhydride is grafted into the base polymer. Surface-treated nano-sized zinc oxide particles are uniformly dispersed in the low-density polyethylene matrix grafted with maleic anhydride.

[0008] Preferably, the grafting mass percentage of the maleic anhydride into the low-density polyethylene matrix polymer is 0.8% to 2.0%;

[0009] The average particle size of the nano-sized zinc oxide particles is 30~60nm, and the mass percentage of the nano-sized zinc oxide particles in the charge suppression and bonding layer material is 1.5%~4.0%.

[0010] The nano-sized zinc oxide particles are surface-treated with a silane coupling agent.

[0011] Preferably, the main material of the self-healing insulating substrate is a cross-linked polyethylene matrix, in which two synergistic functional micro-units are incorporated, including:

[0012] The healing agent microcapsules are core-shell structured microspheres, independently dispersed in the cross-linked polyethylene matrix;

[0013] The solid catalyst nanoparticles are separated from the healing agent microcapsules and independently dispersed in the cross-linked polyethylene matrix, and the solid catalyst nanoparticles are piezoelectric nanomaterials.

[0014] Preferably, the outer shell material of the healing agent microcapsules is melamine-urea-formaldehyde resin with a wall thickness of 150~400nm;

[0015] The core of the healing agent microcapsule is a low-viscosity, two-component liquid healing agent;

[0016] The healing agent microcapsules have an average particle size of 10~30μm, and the mass percentage of the healing agent microcapsules in the self-healing insulating host layer is 5%~12%.

[0017] Preferably, the two-component liquid healing agent includes a main agent and an accelerator, wherein the main agent is an epoxy-functionalized polydimethylsiloxane, the epoxy equivalent of the polydimethylsiloxane is 200~500g / mol, and the viscosity at 25°C is less than 50cP.

[0018] The accelerator is a latent amine curing agent. The curing agent does not react with the main agent at room temperature, but is activated when it comes into contact with the charge generated by the piezoelectric nanomaterial due to stress.

[0019] Preferably, the piezoelectric nanomaterial used as the solid catalyst nanoparticle is lead zirconate titanate nanowhiskers or barium titanate nanowhiskers.

[0020] The nanocrystals have an average diameter of 50~100nm and a length of 1~2μm, and the mass percentage of the nanocrystals in the self-healing insulating host layer is 0.2%~0.8%.

[0021] Preferably, the matrix material of the outer protective hydrophobic layer is cross-linked polyethylene, and fluorinated oligomers are added to the cross-linked polyethylene matrix.

[0022] Preferably, the fluorinated oligomer is a perfluoropolyether, whose main chain structure does not contain hydrogen atoms and whose two ends are capped by non-reactive groups;

[0023] The perfluoropolyether has an average molecular weight of 2000~4000 g / mol, and its mass percentage added to the outer protective hydrophobic layer material is 0.5%~1.5%.

[0024] Preferably, the base material of the outer sheath is high-density polyethylene copolymerized with hexene-1. In addition to carbon black as an ultraviolet absorber, the base material also contains 1.0% to 2.5% infrared reflective pigment by mass percentage.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention internalizes three core functions—anti-electrical dendrite, microcrack self-healing surface dynamic hydrophobicity—into the insulation system itself by modifying the cross-linked polyethylene insulation layer, replacing the traditional external, passive moisture-proof structure.

[0027] The cable of this invention not only improves the insulation degradation and water treeing problems caused by moisture intrusion, but its self-healing capability also provides redundant safety against sudden mechanical damage. Furthermore, optimized thermal management of the outer sheath further enhances the overall weather resistance and service life of the cable. The technical solution is compact in structure and highly compatible with manufacturing processes, providing a novel technical path for achieving highly reliable, long-life moisture-proof overhead insulated cables. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] The present invention provides a method for preparing a cross-linked polyethylene insulated moisture-proof overhead cable, as follows:

[0030] Steel-cored aluminum stranded wire or all-aluminum alloy stranded wire (JLHA1 / G1A-240 / 30) is selected. After stranding, it needs to be compacted and densified by a special mold to compress the cross section into a compacted circle with a smooth surface and a rounded outline.

[0031] A semi-conductive crosslinkable polyethylene composition is used, with EVA containing 18%~28% VA as the matrix and 35%~45% superconducting furnace black (particle size 20~40nm, DBP>150ml / 100g) added to construct a stable conductive network. The material is tightly coated onto the conductor through an online extrusion process at about 120°C to form a 1mm thick layer. After subsequent crosslinking, the volume resistivity is stable at less than 500Ω·m, ensuring equipotential bonding and shielding the conductor tip effect.

[0032] A seamless, integrated structure is achieved by simultaneously extruding three functional sublayers in one go using a specially designed three-layer co-extrusion die head.

[0033] Charge suppression and bonding layer: The matrix is ​​maleic anhydride-grafted low-density polyethylene (grafting rate 0.8%~2.0%) to enhance the chemical bonding with the conductor shielding layer; and 1.5%~4.0% of nano zinc oxide (particle size 30~60nm, treated with silane) is added as a charge trap to suppress the germination of electrical trees; the thickness is 0.3mm.

[0034] The self-healing insulating substrate is made of ultra-clean low-density polyethylene with 1.7%~2.2% DCP crosslinking agent added. Its innovation lies in the composite of two functional units: 5%~12% microcapsules (melamine-urea-formaldehyde resin shell, coated with epoxy-functionalized polydimethylsiloxane and latent amine curing agent) and 0.2%-0.8% piezoelectric nanocatalysts (such as PZT or BaTiO3 whiskers, 50~100nm in diameter, treated with titanate ester). When microcracks are generated, the instantaneous charge generated by the piezoelectric effect activates the released healing agent, which rapidly polymerizes to achieve molecular-level self-healing; the thickness is 3mm.

[0035] Outer protective hydrophobic layer: The matrix is ​​cross-linked polyethylene with 0.5%~1.5% of perfluoropolyether oligomer (Mn=2000~4000) added; the oligomer continuously and slowly migrates to the surface under the drive of temperature gradient, forming a dynamically renewed superhydrophobic monolayer, preventing water film formation and moisture penetration; thickness 0.5mm.

[0036] The insulating shielding layer material is exactly the same as the conductor shielding layer to ensure interface compatibility, with a thickness of 0.9mm. Subsequently, the cable semi-finished product enters the continuous vulcanization production line, where, in a high-temperature and high-pressure nitrogen environment, all polymer layers from the conductor shielding layer to the outer insulating shielding layer are simultaneously cross-linked to form a chemically bonded integrated structure.

[0037] The outermost layer is extruded with a high-density polyethylene sheath, and its innovation lies in the addition of 1.0% to 2.5% infrared reflective pigment, bismuth titanate yellow or antimony-doped tin dioxide.

[0038] To verify the technical advantages of the cross-linked polyethylene insulated moisture-proof overhead cable of this invention, key performance indicators were selected for testing, including moisture-proof and tree-resistant properties, self-healing properties, weather resistance, and service life. The test conditions are as follows:

[0039] Damp heat cycling test: temperature 85℃, relative humidity 95%, 10kV voltage applied for 1000 hours;

[0040] Self-healing performance test: Artificially pre-fabricated 50μm microcracks were left at room temperature for 24 hours to test the repair effect;

[0041] Weather resistance test: Simulate strong outdoor sunlight exposure, near-infrared intensity 1000W / m², monitor steady-state temperature rise of the surface;

[0042] Thermal aging test: After thermal aging at 135℃ for 1000 hours, the breakdown strength retention rate is tested.

[0043] Example 1, baseline parameters: charge suppression and adhesive layer: maleic anhydride grafting rate 1.4% (low-density polyethylene matrix), nano zinc oxide (silane treated, 50nm) 2.5%;

[0044] Self-healing insulating main layer: 8% healing agent microcapsules (melamine-urea-formaldehyde shell, 20μm), 0.5% piezoelectric nanocrystals (lead zirconate titanate, 80nm×1.5μm), and 350g / mol epoxy equivalent of the main healing agent.

[0045] Outer protective hydrophobic layer: 1.0% perfluoropolyether (molecular weight 3000 g / mol);

[0046] Outer sheath: Hexene-1 copolymer high-density polyethylene, infrared reflective pigment (bismuth titanate yellow) 1.8%.

[0047] Example 2, High Anti-electric Tree Optimization: Charge Suppression and Adhesive Layer: Maleic anhydride grafting rate 2.0%, nano zinc oxide (60nm) 3.5%; other parameters are the same as in Example 1.

[0048] Example 3, optimization of high self-healing efficiency: self-repairing insulating host layer: 10% healing agent microcapsules, 0.8% piezoelectric nanowhiskers (barium titanate, 100nm×2μm); other parameters are the same as in Example 1.

[0049] Example 4, High Dynamic Hydrophobicity Optimization: Outer Protective Hydrophobic Layer: 1.3% Perfluoropolyether, with a molecular weight of 4000 g / mol; other parameters are the same as in Example 1.

[0050] Comparative Example 1, Traditional Single-Insulation Cable: Insulation layer: pure cross-linked polyethylene, without three-layer sublayer structure; Outer sheath: ordinary high-density polyethylene, containing only 2.5% carbon black, without infrared reflective pigment.

[0051] Comparative Example 2, partially functional cable: Insulation layer: only contains inner charge suppression and bonding layer, same as in Example 1; outer ordinary cross-linked polyethylene layer, without self-healing and dynamic hydrophobicity; outer sheath: same as in Comparative Example 1.

[0052] Test data comparison results:

[0053]

[0054] The comparison data in the table above clearly shows that:

[0055] 1. Significant advantages in moisture-proof and tree-resistant performance: Through the synergistic effect of the multifunctional composite insulation layer, the length of water trees in this invention is only 7%~11% of that of traditional cables (Comparative Example 1), and the insulation resistance retention rate is increased by 47%~50%. Specifically:

[0056] Example 2 showed the best water treeing inhibition effect due to increased nano zinc oxide content and maleic anhydride grafting rate, verifying the role of charge inhibition and the bonding layer in capturing space charge through deep traps and enhancing interfacial bonding.

[0057] Although Comparative Example 2 has charge suppression and bonding layers, it lacks self-healing and dynamic hydrophobic functions, and the length of the water tree is still 5 to 7 times that of the Example, demonstrating the necessity of multi-layer functional synergy.

[0058] 2. Self-healing function provides redundant safety: The microcrack self-repair rate of Examples 1-4 all reached over 96%, and the breakdown strength recovery rate exceeded 94%, while traditional cables (Comparative Examples 1 and 2) have no self-healing ability. Example 3 achieved 100% repair by increasing the content of healing agent microcapsules and piezoelectric nanocrystals, indicating that the synergistic triggering mechanism of the healing agent and piezoelectric catalyst can effectively respond to microcrack damage and prevent moisture intrusion.

[0059] 3. Significantly improved weather resistance and lifespan: The infrared reflective pigment in the outer sheath reduces the surface temperature rise of the embodiment by 11-13°C compared to traditional cables. Combined with the self-renewing low surface energy film of the dynamic hydrophobic sublayer, it reduces water film formation and thermal aging rate.

[0060] The breakdown strength retention rate after thermal aging is 25-35% higher than that of traditional cables. According to the Arrhenius criterion, the service life can be extended by 2-3 times.

[0061] 4. Parameter optimization direction: Increasing the content of nano zinc oxide and the grafting rate of maleic anhydride (as in Example 2) can enhance the anti-electric treeing effect;

[0062] Increasing the proportion of healing agent microcapsules (as in Example 3) can improve self-healing reliability;

[0063] Moderately increasing the perfluoropolyether content (as in Example 4) helps maintain long-term hydrophobicity.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cross-linked polyethylene insulated moisture-proof overhead cable, comprising, from the inside out, a cable core conductor, a conductor shielding layer, a multifunctional composite insulation layer, and an outer sheath for the insulation shielding layer, characterized in that: The multifunctional composite insulation layer is an integrated composite structure formed in one step through a three-layer co-extrusion process, which includes, from the inside out: a charge suppression and bonding layer, a self-healing insulation main body layer, and an outer protective hydrophobic layer. The charge suppression and bonding layer is an insulating sublayer that is in direct contact with the outer surface of the conductor shielding layer. The base polymer of the charge suppression and bonding layer is low-density polyethylene, and maleic anhydride is grafted onto the base polymer at a mass percentage of 0.8% to 2.0%. In the low-density polyethylene matrix grafted with maleic anhydride, 1.5% to 4.0% by mass of surface-treated zinc oxide particles with an average particle size of 30 to 60 nm are uniformly dispersed. The main material of the self-healing insulating substrate is a cross-linked polyethylene matrix, in which two synergistic functional micro-units are incorporated, including: The healing agent microcapsules are microspheres with a core-shell structure, consisting of a melamine-urea-formaldehyde resin shell material with a wall thickness of 150~400 nm and a low-viscosity, two-component liquid healing agent core, and are independently dispersed in the cross-linked polyethylene matrix. Solid catalyst nanoparticles are separated from the healing agent microcapsules and independently dispersed in the cross-linked polyethylene matrix, wherein the solid catalyst nanoparticles are piezoelectric nanomaterials. The healing agent microcapsules have an average particle size of 10-30 μm, and the mass percentage of the healing agent microcapsules in the self-healing insulating host layer is 5%-12%. The two-component liquid healing agent includes a main agent and an accelerator, wherein the main agent is epoxy-functionalized polydimethylsiloxane, the epoxy equivalent of the polydimethylsiloxane is 200-500 g / mol, and the viscosity at 25°C is less than 50 cP. The accelerator is a latent amine curing agent, which does not react with the main agent at room temperature but is activated upon contact with the charge generated by the piezoelectric nanomaterial due to stress. The piezoelectric nanomaterial used as the solid catalyst nanoparticle is lead zirconate titanate nanowhiskers or barium titanate nanowhiskers; the average diameter of the nanowhiskers is 50~100nm, the length is 1~2μm, and the mass percentage of the nanowhiskers in the self-healing insulating host layer is 0.2%~0.8%.

2. The cross-linked polyethylene insulated moisture-proof overhead cable according to claim 1, characterized in that, The matrix material of the outer protective hydrophobic layer is cross-linked polyethylene, and fluorinated oligomers are added to the cross-linked polyethylene matrix.

3. The cross-linked polyethylene insulated moisture-proof overhead cable according to claim 2, characterized in that, The fluorinated oligomer is a perfluorinated polyether, whose main chain structure does not contain hydrogen atoms, and whose two ends are capped by non-reactive groups. The perfluoropolyether has an average molecular weight of 2000~4000 g / mol, and its mass percentage added to the outer protective hydrophobic layer material is 0.5%~1.5%.

4. The cross-linked polyethylene insulated moisture-proof overhead cable according to claim 1, characterized in that, The base material of the outer sheath is high-density polyethylene copolymerized with hexene-1. In addition to carbon black as an ultraviolet absorber, 1.0% to 2.5% infrared reflective pigment by mass percentage is also added to the base material.

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