Thermooxidatively aging resistant aerial insulated conductor

Abstract

This invention belongs to the field of insulated conductor technology, specifically disclosing a thermo-oxidative aging resistant overhead insulated conductor. The thermo-oxidative aging resistant overhead insulated conductor of this invention includes a conductor and an insulation layer covering the surface of the conductor. The insulation layer includes a thermo-oxidative protective layer, a transition layer, and a photo-oxidative protective layer, all coaxially arranged in contact. The thermo-oxidative protective layer comprises cross-linked polyethylene, a high molecular weight hindered phenolic heat stabilizer, and dilauryl thiodipropionate; the photo-oxidative protective layer comprises cross-linked polyethylene, an ultraviolet absorber, an initiator, and a hindered amine light stabilizer. Through a "high molecular weight + bonded" design, combined with the synergistic effect of nanofillers, the non-volatility, anti-leakage, and multifunctional protection of the antioxidant are achieved. Furthermore, the multi-layer structure design enables the directional distribution of the antioxidant, with priority protection against internal thermo-oxidative damage and priority blocking of external photo-oxidative damage, synergistically breaking the industry's reliance on homogeneous materials.

Description

Technical Field

[0001] This invention relates to the field of insulated conductor technology, and in particular to an overhead insulated conductor resistant to heat and oxygen aging. Background Technology

[0002] Overhead insulated conductors, as the core carrier for transmitting electrical energy in power distribution networks, have been widely used in the construction and renovation of urban and rural power grids due to their ability to effectively reduce line corridors, improve power supply security, and reduce conflicts between trees and lines. These conductors typically consist of aluminum or aluminum alloy conductors, an inner semi-conductive shielding layer, and cross-linked polyethylene (XLPE) or polyethylene (PE) insulation. Their operating conditions are characterized by both "external exposure" and "internal heating." Externally, the insulation layer is constantly exposed to the atmosphere, continuously enduring the combined effects of natural aging factors such as solar ultraviolet radiation, ozone, humidity, and temperature fluctuations. This photo-oxidative aging rate is significantly accelerated, especially in high-altitude, high-sunlight, or industrially polluted areas. Internally, when load current flows through the conductor, conductor resistance loss generates Joule heat, causing the inner side of the insulation layer to be in a high-temperature field for extended periods (normal operating temperature can reach 90℃, and short-circuit transients can even exceed 250℃), thus triggering thermal-oxidative aging. To slow down the aging process, existing technologies generally add hindered phenolic or amine antioxidants to insulating materials, along with ultraviolet absorbers or light stabilizers, in order to build a synergistic internal and external protection system.

[0003] However, in-depth research reveals two inherent flaws in current anti-aging technologies, which are interconnected and have not yet been effectively resolved. First, there is the issue of antioxidant volatilization and migration loss. Traditional small-molecule antioxidants are physically blended with the polyolefin matrix, resulting in weak intermolecular forces. Under long-term high-temperature operation, antioxidant molecules gain sufficient kinetic energy to diffuse to the material surface, subsequently volatilizing into the gaseous environment or being washed away by external moisture such as rainwater and condensation. This irreversible loss directly leads to a continuous decrease in the antioxidant concentration inside the insulation layer, resulting in an effective protective lifespan far below the material's design lifespan. This is especially pronounced in hot and humid regions, where the migration and loss rate increases exponentially, making the "premature depletion" of antioxidants extremely significant. Second, there is the structural brittleness mismatch caused by the asynchronous aging of the insulation layer's interior and exterior. Because the chemical mechanisms of external photo-oxidative aging and internal thermal aging (thermo-oxidative aging) differ (photo-oxidative aging is mainly characterized by free radical chain reactions initiated by ultraviolet light, accompanied by molecular chain cross-linking and surface hardening; thermo-oxidative aging is mainly characterized by heat-induced peroxide decomposition, leading to molecular chain breakage and the initiation of internal microcracks), a single type of antioxidant cannot simultaneously address both types of aging. In existing technologies, even when thermal antioxidants and light stabilizers are used in combination, the outer layer will rapidly harden and lose elasticity due to photo-oxidative effects, while the inner layer will continuously become brittle and lose toughness due to thermo-oxidative effects, ultimately resulting in a "hard outside, cracked inside" phenomenon. When the line encounters wind vibration, icing, or short-circuit electrodynamic stress, this uneven aging layer is highly susceptible to brittle fracture along the radial interface, leading to insulation breakdown or conductor breakage accidents.

[0004] Therefore, how to provide an overhead insulated conductor that is resistant to heat and oxygen aging, and avoids the volatilization and loss of weather-resistant components and the hardening of the outer layer and cracking of the inner layer of the insulation layer, is a problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides an overhead insulated conductor resistant to thermo-oxidative aging, in order to solve the problems of easy volatilization and loss of weather-resistant components in existing overhead insulated conductors, as well as the problems of brittle failure due to external photo-oxidative aging and internal thermal aging, resulting in external hardening and internal cracking.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A heat- and oxygen-resistant overhead insulated conductor includes a conductor and an insulation layer covering the surface of the conductor. The insulation layer includes a heat- and oxygen-resistant protective layer, a transition layer, and a photo- and oxygen-resistant protective layer that are coaxially wrapped and contacted. The thermal oxidation protection layer is located on the side closer to the conductor, while the photo-oxidation protection layer is located on the side farther from the conductor. The heat-oxidation protective layer comprises cross-linked polyethylene, a high molecular weight hindered phenolic heat stabilizer, and dilauryl thiodipropionate. The photo-oxidation protective layer comprises cross-linked polyethylene, ultraviolet absorber, initiator, and hindered amine light stabilizer.

[0007] Preferably, the conductor comprises compacted round aluminum stranded wire and / or steel-cored aluminum stranded wire.

[0008] Preferably, the thickness ratio of the thermal oxidation protection layer, the transition layer, and the photo-oxidation protection layer in the insulating layer is 3~5:2~4:2~4.

[0009] Preferably, the mass ratio of cross-linked polyethylene, high molecular weight hindered phenolic heat stabilizer, and dilauryl thiodipropionate in the thermo-oxidative protective layer is 100:1~2:0.2~0.8; The high molecular weight hindered phenolic heat stabilizer includes one or more of antioxidants 1010, 1076, and 1330.

[0010] Preferably, the transition layer comprises cross-linked polyethylene and activated nano-silica; The mass ratio of the cross-linked polyethylene to the activated nano-silica is 100:3~8.

[0011] Preferably, the method for preparing the activated nano-silica is as follows: Nano-silica was dispersed in a silane coupling agent solution and a grafting reaction was carried out. After the reaction was completed, activated nano-silica was obtained. The mass ratio of the nano-silica to the silane coupling agent is 1:0.03~0.15; The particle size of the nano-silica is 20~50nm; The grafting reaction is carried out at a temperature of 80~90℃ for 4~6 hours, and the reaction is carried out under stirring conditions at a stirring rate of 300~500 rpm.

[0012] Preferably, the mass ratio of cross-linked polyethylene, ultraviolet absorber, initiator and hindered amine light stabilizer in the photo-oxidation protective layer is 100:0.8~1.2:0.1~0.2:0.2~0.8; The ultraviolet absorber is a carboxyl-modified benzotriazole ultraviolet absorber; The hindered amine light stabilizer includes one or more of light stabilizer 622, light stabilizer 944, and light stabilizer 770.

[0013] Preferably, the method for preparing the ultraviolet absorber is as follows: A benzotriazole UV absorber was reacted with maleic anhydride to obtain a carboxyl-modified benzotriazole UV absorber. The reaction is carried out at a temperature of 55-65°C for 3-5 hours. The benzotriazole ultraviolet absorbers include UV-326 and / or UV-329.

[0014] Preferably, the insulating layer is prepared by a three-channel co-extrusion molding method; The extrusion temperature of the thermo-oxidative protective layer is 150~160℃, the extrusion temperature of the transition layer is 155~165℃, and the extrusion temperature of the photo-oxidative protective layer is 160~170℃.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: 1) This invention, through a "high molecular weight + bonded" design combined with the synergistic effect of nanofillers, achieves non-volatility, anti-leakage, and multifunctional protection of antioxidants; it solves the problems of volatility and limited functionality associated with traditional solutions using single small-molecule antioxidants (such as low-molecular-weight hindered phenols). Traditional insulating layers have a homogeneous structure, which cannot specifically address differences in aging between the interior and exterior. This invention, through a gradient design of a thermal oxidation protection layer, a transition layer, and a photo-oxidation protection layer, achieves the directional distribution of antioxidants, enabling synergistic treatment of priority protection against internal thermal oxidation and priority blocking against external photo-oxidation, breaking the industry's reliance on homogeneous materials.

[0016] 2) The thermo-oxidative protective layer of this invention uses a high-molecular-weight hindered phenolic heat stabilizer. Its high molecular weight significantly reduces high-temperature volatilization, focusing on inhibiting internal thermo-oxidative aging, absorbing free radicals generated by conductor heating, and preventing polymer chain breakage caused by conductor heating. Dilauryl thiodipropionate synergistically works with the heat stabilizer to prolong the oxidation induction period and improve overall antioxidant efficiency. In the photo-oxidative protective layer, ultraviolet absorbers are chemically bonded to the cross-linked polyethylene molecular chains, preventing them from being washed away by rainwater. The ultraviolet absorbers and hindered amine light stabilizers can also form a UV shielding layer, efficiently absorbing UV radiation and blocking external photo-oxidative reactions. The transition layer plays a role in enhancing thermal diffusion, blocking ozone, and increasing mechanical strength. The inner, middle, and outer layers of the insulation layer work synergistically to ultimately demonstrate excellent anti-aging performance and weather resistance. Detailed Implementation

[0017] The present invention provides an overhead insulated conductor resistant to heat and oxygen aging, comprising a conductor and an insulating layer covering the surface of the conductor. The insulating layer includes a heat and oxygen protection layer, a transition layer and a photo-oxidation protection layer that are coaxially wrapped and contacted. The heat and oxygen protection layer is located on the side closer to the conductor, and the photo-oxidation protection layer is located on the side away from the conductor.

[0018] In this invention, the conductor comprises compacted round aluminum stranded wire and / or steel-cored aluminum stranded wire.

[0019] In this invention, the thickness ratio of the thermal oxidation protection layer, the transition layer and the photo-oxidation protection layer in the insulating layer is 3~5:2~4:2~4, preferably 3.5~4.5:2.5~3.5:2.5~3.5, and more preferably 4:3:3.

[0020] In this invention, the thermo-oxidative protective layer comprises cross-linked polyethylene, a high molecular weight hindered phenolic heat stabilizer, and dilauryl thiodipropionate.

[0021] In this invention, the mass ratio of cross-linked polyethylene, high molecular weight hindered phenolic heat stabilizer and dilauryl thiodipropionate in the thermo-oxidative protective layer is 100:1~2:0.2~0.8, preferably 100:1.2~1.8:0.4~0.6, and more preferably 100:1.5:0.5.

[0022] In this invention, the high molecular weight hindered phenolic heat stabilizer includes one or more of antioxidant 1010, antioxidant 1076 and antioxidant 1330.

[0023] In this invention, the transition layer comprises cross-linked polyethylene and activated nano-silica.

[0024] In this invention, the mass ratio of the cross-linked polyethylene to the activated nano-silica is 100:3~8, preferably 100:4~6, and more preferably 100:5.

[0025] In this invention, the method for preparing the activated nano-silica is as follows: Nano-silica was dispersed in a silane coupling agent solution and grafted to obtain activated nano-silica after the reaction was completed.

[0026] In this invention, the mass ratio of nano-silica to silane coupling agent is 1:0.03~0.15, preferably 1:0.05~0.1, and more preferably 1:0.08.

[0027] In this invention, the particle size of the nano-silica is 20~50nm, specifically 25nm, 30nm, 35nm, 40nm, or 45nm.

[0028] In this invention, the grafting reaction temperature is 80~90℃, specifically 82℃, 84℃, 85℃, 86℃, or 88℃; the time is 4~6h, specifically 4.2h, 4.5h, 4.8h, 5h, 5.2h, 5.5h, or 5.8h; the grafting reaction is carried out under stirring conditions, with a stirring rate of 300~500rpm, specifically 320rpm, 350rpm, 380rpm, 400rpm, 420rpm, 450rpm, or 480rpm.

[0029] In this invention, the grafting reaction of nano-silica with silane coupling agent can improve its dispersibility, reduce particle agglomeration, enhance the density of the transition layer, and reduce local stress concentration and uneven concentration. The addition of activated nano-silica to the transition layer can improve the tensile strength of the transition layer and prevent the antioxidant distribution imbalance caused by mechanical stress between the inner and outer layers. The high thermal conductivity of nano-silica accelerates the heat transfer from the inner layer to the outer layer, reduces the thermal aging rate of the inner layer, and indirectly extends the life of the inner layer of the insulation layer. The addition of nano-silica can also enable the transition layer to form a physical barrier, blocking the penetration of external ozone into the interior.

[0030] In this invention, the photo-oxidation protective layer comprises cross-linked polyethylene, ultraviolet absorber, initiator, and hindered amine light stabilizer.

[0031] In this invention, the mass ratio of cross-linked polyethylene, ultraviolet absorber, initiator and hindered amine light stabilizer in the photo-oxidation protective layer is 100:0.8~1.2:0.1~0.2:0.2~0.8, preferably 100:0.9~1.1:0.12~0.18:0.4~0.6, and more preferably 100:1:0.15:0.5.

[0032] In this invention, the ultraviolet absorber is a carboxyl-modified benzotriazole ultraviolet absorber; the hindered amine light stabilizer includes one or more of light stabilizer 622, light stabilizer 944 and light stabilizer 770; the initiator is preferably dicumyl peroxide.

[0033] In this invention, the ultraviolet absorber is prepared as follows: A benzotriazole UV absorber was reacted with maleic anhydride to obtain a carboxyl-modified benzotriazole UV absorber.

[0034] In this invention, the reaction temperature is 55~65℃, specifically 56℃, 58℃, 60℃, 65℃, or 64℃; the reaction time is 3~5h, specifically 3.2h, 3.5h, 3.8h, 4h, 4.2h, 4.5h, or 4.8h.

[0035] In this invention, the benzotriazole ultraviolet absorber includes UV-326 and / or UV-329.

[0036] In this invention, the insulating layer is prepared by a three-channel co-extrusion molding method; the extrusion temperature of the thermo-oxidative protective layer is 150~160℃, specifically 152℃, 154℃, 155℃, 156℃, or 158℃; the extrusion temperature of the transition layer is 155~165℃, specifically 156℃, 158℃, 160℃, 162℃, or 164℃; and the extrusion temperature of the photo-oxidative protective layer is 160~170℃, specifically 162℃, 164℃, 165℃, 166℃, or 168℃.

[0037] In this invention, when the overhead insulated conductor is 10kV or above, it also includes a conductor shielding layer, which is located between the conductor and the insulation layer.

[0038] 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.

[0039] Example 1

[0040] Thermo-oxidative protective layer components: 100 parts cross-linked polyethylene, 1.5 parts antioxidant 1010, and 0.5 parts dilauryl thiodipropionate.

[0041] Transition layer components: 100 parts cross-linked polyethylene, 5 parts activated nano silica.

[0042] Photo-oxidation protective layer components: 100 parts cross-linked polyethylene, 1 part ultraviolet absorber, 0.15 parts dicumyl peroxide, and 0.5 parts light stabilizer 622.

[0043] The preparation steps for activated nano-silica include: Nano-sized silica (20-50 nm) was ultrasonically dispersed in a 5 wt% silane coupling agent ethanol solution; then, the system temperature was maintained at 80 °C, and the reaction was carried out at 350 rpm for 5 h to generate surface-grafted activated nano-silica.

[0044] Treatment steps for ultraviolet absorbers: UV absorber UV-326 and maleic anhydride were thoroughly mixed in acetone solution at a molar ratio of 1:1.2 and the mixture was kept at 60°C for 4 hours to obtain a carboxyl-modified UV absorber. The obtained carboxyl-modified UV absorber was then melt-mixed with cross-linked polyethylene and dicumyl peroxide to undergo graft bonding, and then light stabilizer 622 was added and mixed.

[0045] The above three components were extruded using a three-channel co-extrusion extruder. The extrusion temperatures of the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were controlled at 160℃, 165℃, and 170℃, respectively. This resulted in an overhead insulated conductor resistant to thermal-oxidative aging, in which the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were sequentially coated on the surface of a tightly compressed round aluminum stranded wire. The thicknesses of the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were 4:3:3.

[0046] Example 2

[0047] Thermo-oxidative protective layer components: 100 parts cross-linked polyethylene, 2 parts antioxidant 1076, and 0.6 parts dilaurate thiodipropionate.

[0048] Transition layer components: 100 parts cross-linked polyethylene, 8 parts activated nano silica (same as Example 1).

[0049] Photo-oxidation protective layer components: 100 parts cross-linked polyethylene, 0.8 parts ultraviolet absorber (same as Example 1), 0.15 parts dicumyl peroxide, and 0.6 parts light stabilizer 622.

[0050] The above three components were extruded using a three-channel co-extrusion extruder. The extrusion temperatures of the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were controlled at 155℃, 160℃, and 170℃, respectively. This resulted in an overhead insulated conductor resistant to thermal-oxidative aging, in which the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were sequentially coated on the surface of a tightly compressed round aluminum stranded wire. The thicknesses of the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were 4:3:3.

[0051] Example 3

[0052] Thermo-oxidative protective layer components: 100 parts cross-linked polyethylene, 1.2 parts antioxidant 1010, and 0.5 parts dilaurate thiodipropionate.

[0053] Transition layer components: 100 parts cross-linked polyethylene, 6 parts activated nano silica (same as Example 1).

[0054] Photo-oxidation protective layer components: 100 parts cross-linked polyethylene, 1.2 parts ultraviolet absorber (same as Example 1), 0.12 parts dicumyl peroxide, and 0.4 parts light stabilizer 944.

[0055] The above three components were extruded using a three-channel co-extrusion extruder. The extrusion temperatures of the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were controlled at 160℃, 165℃, and 170℃, respectively. This resulted in an overhead insulated conductor resistant to thermal-oxidative aging, in which the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were sequentially coated on the surface of a tightly compressed round aluminum stranded wire. The thicknesses of the thermal-oxidative protective layer, the transition layer, and the photo-oxidative protective layer were 4:3:3.

[0056] Comparative Example 1

[0057] 100 parts of cross-linked polyethylene and 1.5 parts of antioxidant 1010 are mixed and extruded to obtain an insulation layer.

[0058] Comparative Example 2

[0059] The only difference between this comparative example and Example 1 is that no activated nano-silica is added to the transition layer.

[0060] Comparative Example 3

[0061] The only difference between this comparative example and Example 1 is that no initiator is added to the photo-oxidation protective layer.

[0062] Test samples were cut from the insulation layers of the overhead insulated conductors prepared in Examples 1-3 and Comparative Examples 1-2. The tensile strength of the test samples was tested in accordance with GB / T 2951.11-2008. Then, the same test samples were subjected to aging treatment. After aging treatment, the tensile strength of the test samples was tested again. The test results are shown in Table 1.

[0063] Aging treatment: The side of the test sample away from the conductor is heat-insulated, and then a thermal aging test (135℃±1℃) is carried out using the thermal aging test method in GB / T 2951.12-2008. Then, the other side of the test sample is shielded from light, and a light aging test (1008h) is carried out using the method in GB / T 14049-2008.

[0064] Table 1. Compressive strength results of insulation layer materials before and after aging test

[0065] As can be seen from Table 1, the insulating layer obtained by the embodiments of the present invention has both high initial tensile strength and tensile strength retention rate. After aging test, there is no obvious cracking on the light-exposed surface, and there is no phenomenon of external hardening and internal cracking. Compared with Comparative Example 1 and Comparative Example 2, the tensile strength of the insulating layer obtained by the embodiments of the present invention is significantly improved, which is mainly attributed to the addition of activated nano-silica in the transition layer. Compared with Comparative Example 2, it can be seen that the addition of activated nano-silica not only helps to enhance the tensile strength of the insulating layer, but also effectively improves the tensile strength retention rate.

[0066] Insulation layers of the overhead insulated conductors prepared in Example 1 and Comparative Example 3 were sampled. One side of the photo-oxidation protective layer of the samples underwent a cycle of light irradiation and spraying (102 minutes of light irradiation, 18 minutes of spraying, artificial simulated acid rain (pH = 5.6) sprayed onto the sample surface at a 45° angle with a flow rate controlled at 1 L / min). This treatment was repeated for 10 cycles. Tensile strength was tested before and after treatment, and the tensile strength retention rate was calculated. The results showed that the tensile strength retention rate of the insulation layer in Example 1 was 97.5%, significantly higher than the 77% in Comparative Example 3. This demonstrates that the addition of the initiator can achieve covalent bonding of the components in the photo-oxidation protective layer, preventing the volatilization and loss of effective components, and significantly improving its resistance to rainwater erosion.

[0067] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0068] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heat- and oxygen-resistant overhead insulated conductor, comprising a conductor and an insulation layer covering the surface of the conductor, characterized in that, The insulating layer includes a thermal-oxidative protective layer, a transition layer, and a photo-oxidative protective layer that are coaxially wrapped and contacted. The thermal oxidation protection layer is located on the side closer to the conductor, while the photo-oxidation protection layer is located on the side farther from the conductor. The heat-oxidation protective layer comprises cross-linked polyethylene, a high molecular weight hindered phenolic heat stabilizer, and dilauryl thiodipropionate. The photo-oxidation protective layer comprises cross-linked polyethylene, ultraviolet absorber, initiator, and hindered amine light stabilizer.

2. The heat- and oxygen-resistant overhead insulated conductor according to claim 1, characterized in that, The conductors include compacted round aluminum stranded wire and / or steel-cored aluminum stranded wire.

3. The heat- and oxygen-resistant overhead insulated conductor according to claim 2, characterized in that, The thickness ratio of the thermal oxidation protection layer, the transition layer, and the photo-oxidation protection layer in the insulating layer is 3~5:2~4:2~4.

4. A thermo-oxidative aging resistant overhead insulated conductor according to any one of claims 1 to 3, characterized in that, The mass ratio of cross-linked polyethylene, high molecular weight hindered phenolic heat stabilizer, and dilauryl thiodipropionate in the heat-oxidation protective layer is 100:1~2:0.2~0.

8. The high molecular weight hindered phenolic heat stabilizer includes one or more of antioxidants 1010, 1076, and 1330.

5. The heat- and oxygen-resistant overhead insulated conductor according to claim 4, characterized in that, The transition layer comprises cross-linked polyethylene and activated nano-silica; The mass ratio of the cross-linked polyethylene to the activated nano-silica is 100:3~8.

6. The heat- and oxygen-resistant overhead insulated conductor according to claim 5, characterized in that, The method for preparing the activated nano-silica is as follows: Nano-silica was dispersed in a silane coupling agent solution and a grafting reaction was carried out. After the reaction was completed, activated nano-silica was obtained. The mass ratio of the nano-silica to the silane coupling agent is 1:0.03~0.15; The particle size of the nano-silica is 20~50nm; The grafting reaction is carried out at a temperature of 80~90℃ for 4~6 hours, and the reaction is carried out under stirring conditions at a stirring rate of 300~500 rpm.

7. A thermo-oxidative aging resistant overhead insulated conductor according to claim 5 or 6, characterized in that, The mass ratio of cross-linked polyethylene, ultraviolet absorber, initiator and hindered amine light stabilizer in the photo-oxidation protective layer is 100:0.8~1.2:0.1~0.2:0.2~0.8; The ultraviolet absorber is a carboxyl-modified benzotriazole ultraviolet absorber; The hindered amine light stabilizer includes one or more of light stabilizer 622, light stabilizer 944, and light stabilizer 770.

8. The heat- and oxygen-resistant overhead insulated conductor according to claim 7, characterized in that, The method for preparing the ultraviolet absorber is as follows: A benzotriazole UV absorber was reacted with maleic anhydride to obtain a carboxyl-modified benzotriazole UV absorber. The reaction is carried out at a temperature of 55-65°C for 3-5 hours. The benzotriazole ultraviolet absorbers include UV-326 and / or UV-329.

9. The heat- and oxygen-resistant overhead insulated conductor according to claim 8, characterized in that, The insulating layer is prepared by a three-channel co-extrusion molding method; The extrusion temperature of the thermo-oxidative protective layer is 150~160℃, the extrusion temperature of the transition layer is 155~165℃, and the extrusion temperature of the photo-oxidative protective layer is 160~170℃.

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