Surface treatment method for improving blackbody radiation coefficient of overhead power transmission conductor

Abstract

The present application relates to overhead power transmission conductor technical field, especially point to a kind of surface treatment method for improving overhead power transmission conductor blackbody radiation coefficient.The present application aims at solving the problems that existing overhead power transmission conductor in surface treatment process, process compatibility caused by structural complexity is poor, sandblasting is easy to damage aluminum wire, coating solidification thermal expansion difference leads to cracking, gap gas escape affects coating density etc., simultaneously solve the comprehensive technical problems that high emissivity coating technology in existing high temperature curing damage wire, coating flexibility is insufficient bending cracking, incompatible with production line etc.

Description

Technical Field

[0001] This invention relates to the field of overhead power transmission line technology, and in particular to a surface treatment method for improving the blackbody radiation coefficient of overhead power transmission lines. Background Technology

[0002] With the global energy transition and the continued growth of electricity load, grid operators urgently need to increase the current carrying capacity of existing lines without constructing new transmission line corridors. The radiative heat dissipation capacity of overhead conductors is directly related to their surface blackbody emissivity (emissivity, ε). Traditional bright aluminum conductors have extremely low surface emissivity, typically only 0.2-0.3, and mainly rely on convection for heat dissipation. In recent years, grid operators have explicitly required that overhead conductors achieve an emissivity ≥0.6 (under normal operating temperature) at the time of manufacture.

[0003] Currently, the main technical approaches to improving the transmittance of overhead power lines and their limitations are as follows: Surface physical treatment: Sandblasting can matte the surface of the conductor, which can moderately improve the emissivity. CN102254626A discloses a matte conductor and its preparation method. The matte surface is obtained by sandblasting alone. The emissivity of sandblasting alone is only about 0.4 at 70°C, and the emissivity decreases with increasing temperature.

[0004] Surface chemical treatment: It can improve emissivity to 0.77-0.85, but this method requires the use of acid, which will corrode the steel core in the composite structure wire, and the waste liquid treatment is environmentally costly, making it unsuitable for continuous production of composite wires containing steel cores.

[0005] Coating technologies: (1) Ceramic-based inorganic coating: The emissivity of this method can reach 0.9, but the curing temperature is usually >200℃, which will affect the mechanical properties of aluminum wires; the toughness of ceramic coating is limited, and microcracks are easily generated during repeated bending and stranding of wires; at the same time, special spraying equipment and high-temperature curing line are required, which makes it difficult to integrate with existing stranded wire production lines. (2) Polymer-based organic coating: CN102977700A discloses a fluorocarbon coating composition for overhead wires. (3) Graphene composite coating: CN120809361A discloses a graphene coating on the back side of the wire substrate, and the interface between the wire and the coating is sandblasted, with a surface roughness Ra of 3.2-6.3μm.

[0006] For overhead transmission conductors with composite structures (especially those with special structural designs), the structural feature is an axial gap between the steel core and the outer layer of shaped aluminum wire. This gap design allows the aluminum wire layer to slide freely relative to the steel core during high-temperature operation, effectively controlling sag. However, this structural feature also presents unique challenges for surface treatment. Excessive sandblasting pressure can damage the aluminum wire or disrupt the gap structure; the difference in thermal expansion coefficients between the steel core and the aluminum wire layer may lead to stress concentration during coating curing, causing coating cracking; simultaneously, gas trapped in the gap expands and escapes during heating and curing, potentially forming pores through the incompletely cured coating, affecting coating density and adhesion.

[0007] There is currently no coating process solution specifically designed for this type of conductor with a special structure that balances high emissivity and high flexibility. Therefore, developing a surface treatment process suitable for overhead transmission conductors, balancing high emissivity, high flexibility, low-temperature curing, and integrating online with existing stranded wire production lines, has become a pressing technical challenge in this field. Summary of the Invention

[0008] Therefore, the technical problem to be solved by the present invention is to overcome the problems in the surface treatment of overhead power transmission lines in the prior art, such as poor process compatibility due to structural complexity, easy damage to aluminum wires by sandblasting, cracking caused by thermal expansion differences during coating curing, and gas escape from gaps affecting coating density. At the same time, it solves the technical problems commonly found in existing high emissivity coating technologies, such as high temperature curing damage to conductors, insufficient coating flexibility leading to bending cracks, and incompatibility with production lines.

[0009] To address the aforementioned technical problems, this invention provides a surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines, comprising the following steps: S11: At 95-105℃, a composite coating material is applied to the surface of the pretreated overhead transmission line; the composite coating material includes organosilicon-modified polyester resin, nano-sized silica fume, hexagonal boron nitride, carbon black, additives and solvents. S12: After the overhead transmission line is coated in step S11, heat it at 80-95℃ for 1.5-2.5 min, cure it at 120-135℃ for 2.5-3.5 min, and keep it at 110-125℃ for 0.5-1 min. S13: Cool the overhead power transmission line after heat preservation in step S12 to 40°C or below to complete the surface treatment method.

[0010] The present invention provides a high emissivity surface treatment process that does not damage the steel core, does not disrupt the gap structure, does not reduce the mechanical properties of the aluminum wire, and does not cause the coating to crack during repeated bending and stranding of the conductor. Moreover, this process can be completed continuously and integrally after the stranding process of the overhead transmission conductor, without the need for secondary winding and unwinding.

[0011] Preferably, in step S11, the pretreatment method is to perform sandblasting at 0.5-0.7 MPa and the sandblasting speed is 10-18 m / min.

[0012] Furthermore, during pretreatment, the stranded overhead transmission conductors are continuously passed through a matte finish treatment device and sandblasted with dry diamond abrasive to remove surface oil and natural oxide layers, forming a rough surface with micro-pitted structures to enhance the mechanical anchoring force of subsequent coatings.

[0013] Specifically, during pretreatment, the abrasive material is 80-120 mesh with a Mohs hardness ≥7.5; the sandblasting device consists of three sets of sandblasting chambers, each equipped with four spray guns, with the spray guns at an angle of 45-60° to the wire; the sandblasting air pressure is 0.5-0.7 MPa; the abrasive consumption rate is 3-5% of the container's full capacity per use; regarding surface roughness, the maximum height Rz of the wire surface profile after treatment is controlled at 25-50 μm, which translates to an arithmetic mean roughness Ra of approximately 5-10 μm; the pretreated wire has a uniform matte finish with no missed areas.

[0014] Furthermore, for gap conductors (GAP conductors) with an axial gap between the steel core and the irregular aluminum wire layer, the sandblasting pressure can be appropriately reduced to 0.4-0.6 MPa to prevent sandblasting from damaging the aluminum wire or destroying the axial gap structure.

[0015] This invention precisely controls the roughness range to match the subsequent organic-inorganic hybrid coating, and optimizes the sandblasting air pressure window for irregular aluminum wires and gap structures in gap-type conductors; simple sandblasting can only achieve a matte effect, without considering the risk of damage to the aluminum wires and gaps.

[0016] Preferably, the pretreated conductor immediately enters the high-frequency preheating section with a frequency of 10-30kHz and a preheating length of 2m. The preheating is controlled by a closed-loop infrared thermometer to raise the surface temperature of the conductor to 95-105℃ with an accuracy of ±2℃.

[0017] The purpose of preheating is to: (1) remove residual moisture and fine dust from the surface; (2) improve the initial fluidity and spreadability of the coating; (3) promote cross-linking of the coating from the inside to the outside during subsequent curing, and enhance adhesion; (4) for gap-type wires, preheating can allow the gas in the gap to be heated gradually and evenly released, avoiding the concentrated burst of gas during subsequent high-temperature curing, which would cause pores in the coating.

[0018] Furthermore, the coating is carried out at 98-102°C.

[0019] Preferably, in step S11, the composite coating material comprises, by weight, 40-60 parts of silicone-modified polyester resin, 15-25 parts of nano-sized silica fume, 5-10 parts of hexagonal boron nitride (h-BN), 3-6 parts of carbon black, 1-3 parts of additives, and 20-30 parts of solvent.

[0020] Among them, the silicone-modified polyester resin is the film-forming material, with a silicon content of 10-20 wt%, and is SP506 type resin purchased from Shenzhen Winova Chemical Materials Co., Ltd., with a number average molecular weight (Mn) of 2000-8000.

[0021] The nano-sized silica fume has a particle size of 1-5 μm and a SiO2 content of ≥95%. It is purchased from Shenzhen Jinhaohui Industrial Development Co., Ltd. as coating-grade ultrafine silica fume powder.

[0022] The hexagonal boron nitride has a sheet diameter of 0.5-2 μm and a purity of ≥99%. It is a premium grade hexagonal boron nitride produced by Qingzhou Fangzhou New Materials Co., Ltd., and the product specification is coating grade C.

[0023] The carbon black used is pigment carbon black with a particle size of 20-50 nm, and it is the pigment carbon black product of Tianjin Xinglongtai Chemical Products Technology Co., Ltd.

[0024] Preferably, the additives include dispersant DISPERBYK-163, defoamer BYK-066N, and leveling agent BYK-358N. These three are added independently without a fixed ratio. The amount of dispersant BYK-163 depends on the type and amount of pigments and fillers in the formulation (especially carbon black, which can account for 80-100% of the pigment content). The amount of defoamer BYK-066N is 0.1-0.7 wt% of the total formulation, and the amount of leveling agent BYK-358N is 0.1-1 wt% of the total formulation.

[0025] Preferably, the solvent consists of xylene and butyl ester in a mass ratio of 6-8:3.

[0026] Furthermore, the composite coating material is made by mixing and dispersing silicone-modified polyester resin, nano-sized silica fume, hexagonal boron nitride, carbon black, additives and solvents, grinding them to a fineness of ≤15μm, and then filtering.

[0027] Among them, under heating conditions, the silicone-modified polyester resin undergoes a cross-linking reaction between the silanol and polyesterol to form a dense organic-inorganic hybrid network structure; hexagonal boron nitride and silica fume provide high infrared emissivity and wear resistance, while carbon black assists in improving the emissivity across the entire wavelength band.

[0028] Preferably, in step S11, the coating method is air spraying, and the spraying flow rate is 60-120 mL / min. The preheated wire is continuously passed through an automatic spraying chamber, and the prepared coating is evenly sprayed onto the outer surface of the wire using a non-electrostatic air spraying method.

[0029] Furthermore, during spraying, the equipment length is 1.5-2.0 m, the spray gun is a high-atomization low-pressure spray gun (HVLP), and the air pressure is 0.2-0.35 MPa. The distance between the spray gun and the guide wire is 150-250 mm, the ambient temperature of the spraying chamber is 20-25℃, the relative humidity is ≤65%, and it is equipped with a HEPA air filtration system (filtration accuracy 0.3μm).

[0030] Preferably, in step S11, the coating thickness is 25-40 μm. Real-time monitoring is performed using an online laser thickness gauge, and the thickness deviation is no greater than ±3 μm.

[0031] Preferably, in step S12, the temperature change rate during heating, curing, and heat preservation is 0.5-1.0℃ / min. The coated conductor enters an infrared heating curing oven, employing a segmented heating-heat preservation-cooling process, strictly controlling the maximum temperature to ≤135℃ to avoid damage to the steel core (tempering temperature of steel core is approximately 300℃) and aluminum substrate (over-aging temperature of aluminum >180℃). For gap-type conductors, low-temperature curing can also reduce the internal stress caused by the difference in thermal expansion between the steel core and the shaped aluminum wire.

[0032] Furthermore, in step S12, the methods for heating, curing, and heat preservation are as follows: The curing equipment is 14-16 m long; Segmented control: (1) First zone (heating section): length 4 m, temperature 80-95℃, residence time 1.5-2.5 min, solvent evaporation, initial leveling of coating, and further slow escape of residual gas in the gap; (2) Second zone (curing section): 8 m in length, 120-135℃ in temperature, 2.5-3.5 min in residence time, to complete the cross-linking reaction; (3) Third zone (insulation section): length 2 m, temperature 110-125℃, dwell time 0.5-1 min, to eliminate internal stress; each zone has an independent thermocouple and infrared thermal imager for real-time feedback and adjustment.

[0033] Preferably, in step S13, cooling is performed at a rate of 0.2-0.4℃ / min. A cooling rate of 0.2-0.4℃ / min is significantly slower than the aging cooling of aluminum alloys, which facilitates the full release of internal stress in the coating and improves bending resistance. Further reducing the cooling rate for gap-type conductors can avoid additional stress caused by the difference in cooling shrinkage between the steel core and the aluminum wire layer.

[0034] Furthermore, for gap conductors (GAP conductors) with an axial gap between the steel core and the shaped aluminum wire layer, the cooling rate is further reduced to 0.2-0.3℃ / min to facilitate the slow release of stress caused by the difference in cooling and shrinkage rates between the steel core and the aluminum wire layer.

[0035] After curing, the conductors are cooled to room temperature at a controlled rate through partitioned cooling chambers to prevent stress cracking or reduced adhesion caused by rapid cooling. There are four independent cooling zones, each 1.2 m long. Each cooling zone is equipped with a four-sided, eight-pipe circulating air system with an air velocity of 8-12 m / s and an air temperature of 10-15℃ (controlled by a refrigeration unit).

[0036] Preferably, in step S13, after cooling, a frame stranding machine is used for stranding at a speed of 10-18 m / min. The surface treatment process of the present invention is connected in series after the frame stranding machine and before the take-up machine of the overhead transmission line, realizing integrated continuous production without the need for secondary take-up and unwinding.

[0037] Furthermore, a tension sensor is installed during stranding to maintain the wire tension within the range of 150-300 N; neutral paper is automatically inserted between the wire layers during take-up to prevent scratches on the coating.

[0038] Existing coating technologies are mostly offline coating in factories or on-site robotic coating, and no online integration solution with stranding machines has been disclosed. The integrated solution of this invention can significantly improve production efficiency and reduce the risk of coating scratches.

[0039] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: By employing an organic-inorganic hybrid coating containing hexagonal boron nitride (h-BN) and nano-silica fume, the emissivity of the conductor surface at room temperature is ≥0.90, and at normal operating temperature is ≥0.78, far exceeding the 0.6 required by power grid users. Compared with simple sandblasting, the emissivity temperature stability of this invention is significantly improved.

[0040] In this invention, silicone-modified polyester resin provides excellent flexibility. Combined with an ultra-slow cooling process (0.2-0.4℃ / min) to eliminate internal stress in the coating, the coating's elongation at break is ≥8%, and there is no cracking or peeling during wire bending. In contrast, ceramic coatings are at risk of microcracks under the same bending conditions. The flexibility advantage of this invention is particularly prominent for special structure conductors such as gap conductors. The curing temperature is ≤135℃, far lower than the over-aging temperature of aluminum and the tempering temperature of steel cores, ensuring that the conductors retain their original mechanical and electrical properties after surface treatment. Existing ceramic coatings require curing at temperatures above 200℃, which may cause softening of aluminum conductors or degradation of steel core performance.

[0041] This invention utilizes preheating at 95-105℃ to allow gas within the gaps to gradually escape, preventing the formation of coating pores during curing. Low-temperature curing and ultra-slow cooling reduce internal stress caused by the difference in thermal expansion coefficients between the steel core and the aluminum wire layer, preventing coating cracking. The process of this invention can be directly integrated after the overhead transmission conductor frame stranding machine, achieving integrated continuous production without secondary winding and unwinding, avoiding coating scratches. Production efficiency is increased by approximately 30% compared to offline coating and over 50% compared to robotic on-site coating, while also having lower equipment investment and maintenance costs.

[0042] The coating material of this invention does not contain heavy metals, pyridine, or other harmful substances, and there is no waste acid or waste liquid discharge; both hexagonal boron nitride and silica fume are environmentally friendly materials; silica fume is an industrial by-product and is inexpensive. Accelerated aging tests have verified that the emissivity of the coating of this invention decreases by ≤5%, adhesion remains at level 0, and the estimated actual service life exceeds 40 years, meeting the long-term operation requirements of the power grid. Attached Figure Description

[0043] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0044] Figure 1 This is a physical image of the product of this invention; Figure 2 This is the process route diagram of the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0046] Example 1: Preparation of Overhead Transmission Conductors The overhead transmission line (model JL / G1A) underwent pretreatment. The stranded overhead transmission line was continuously passed through a matte finish treatment device and sandblasted with dry diamond abrasive at 0.6 MPa at a speed of 14 m / min to remove surface oil and natural oxide layers, creating a rough surface with microscopic pit structures to enhance the mechanical anchoring force of subsequent coatings. The diamond abrasive was 100 mesh with a Mohs hardness ≥7.5. The sandblasting device consisted of three sets of sandblasting chambers, each equipped with four spray guns, with the spray guns at a 45° angle to the conductor. The diamond abrasive consumption rate was 4% of the container's full capacity per use. The maximum height Rz of the conductor surface profile after treatment was controlled to be 50 μm.

[0047] The pretreated wires immediately enter the high-frequency preheating section, with a frequency of 10-30kHz and a preheating length of 2m. The infrared thermometer is used for closed-loop control to raise the surface temperature of the wires to 100℃ with an accuracy of ±2℃.

[0048] Simultaneously, 500 g of silicone-modified polyester resin (SP506 type resin from Shenzhen Weinuohua Chemical Materials Co., Ltd., with a number average molecular weight Mn of 5000), 200 g of nano-grade silica fume (particle size of 1-5 μm, purchased from Shenzhen Jinhaohui Industrial Development Co., Ltd. for coating grade ultrafine silica fume powder), 100 g of hexagonal boron nitride (flake size of 0.5-2 μm, purchased from Qingzhou Fangzhou New Materials Co., Ltd. for premium grade hexagonal boron nitride, product specification: coating grade C), 60 g of carbon black (pigment carbon black, particle size of 20-50 nm, using pigment carbon black products from Tianjin Xinglongtai Chemical Products Technology Co., Ltd.), 30 g of additives (including 29.55 g of dispersant BYK-163, 0.20 g of defoamer BYK-066N, and 0.25 g of leveling agent BYK-358N), and 300 g of mixed organic solvent (210 g of xylene and 90 g of styrene) were added. After mixing (g butyl ester), the mixture is dispersed and ground to a fineness of ≤15μm to obtain the prepared coating.

[0049] Under 100℃ heating conditions, the pre-treated wires are passed through an automatic spraying chamber and coated evenly with a prepared coating using a non-electrostatic air spraying method, achieving a coating thickness of 40 μm. During spraying, the equipment length is 1.5m, and a high-atomization, low-pressure spray gun is used with an air pressure of 0.2 MPa. The distance between the spray gun and the wire is 200 mm. The ambient temperature of the spraying chamber is 25℃, the relative humidity is ≤65%, and a HEPA (High-Efficiency Particulate Air) air filtration system is provided.

[0050] After the coating is completed, the overhead transmission line is passed through a 4-meter-long curing device with a heating section at 90°C for 2 minutes. Then, the overhead transmission line is passed through an 8-meter-long curing device with a curing section at 130°C for 3 minutes to complete the cross-linking reaction. Finally, the overhead transmission line is passed through a 2-meter-long curing device with a heat preservation section at 120°C for 1 minute to eliminate internal stress.

[0051] The conductor is cooled to 40°C at a rate of 0.2-0.4°C / min. After cooling, it is stranded using a frame stranding machine at a speed of 14 m / min and a conductor tension of 200 N. Neutral paper is automatically inserted between the conductor layers during the winding process.

[0052] Example 2: Preparation of Overhead Transmission Conductors This embodiment is the same as Embodiment 1, except that 400 g of silicone-modified polyester resin, 150 g of nano-sized silica fume, 50 g of hexagonal boron nitride, 30 g of carbon black, 10 g of additives (including 9.85 g of dispersant BYK-163, 0.05 g of defoamer BYK-066N and 0.10 g of leveling agent BYK-358N) and 300 g of mixed organic solvent (210 g of xylene and 90 g of butyl ester) are mixed, dispersed and ground to a fineness ≤15 μm to obtain the prepared coating.

[0053] Example 3: Preparation of Overhead Transmission Conductors This embodiment is the same as Embodiment 1, except that 600 g of silicone-modified polyester resin, 250 g of nano-sized silica fume, 100 g of hexagonal boron nitride, 60 g of carbon black, 30 g of additives (including 29.55 g of dispersant BYK-163, 0.20 g of defoamer BYK-066N and 0.25 g of leveling agent BYK-358N) and 300 g of mixed organic solvent (210 g of xylene and 90 g of butyl ester) are mixed, dispersed and ground to a fineness ≤15 μm to obtain the prepared coating.

[0054] Comparative Example 1: Preparation of Overhead Transmission Conductors This comparative example is the same as Example 1, except that a polyester resin is used instead of the silicone-modified polyester resin; the resin is purchased from Changxing Chemical and is model ETERKYD 5117 thermoplastic saturated polyester resin.

[0055] Comparative Example 2: Preparation of Overhead Transmission Conductors Without Nanoscale Silica Fume This comparative example is the same as Example 1, except that the coating does not contain nano-sized silica fume.

[0056] Comparative Example 3: Preparation of Overhead Transmission Conductors Without Hexagonal Boron Nitride This comparative example is the same as Example 1, except that the coating does not contain hexagonal boron nitride.

[0057] Comparative Example 4: Preparation of Overhead Transmission Conductors Without Carbon Black This comparative example is the same as Example 1, except that the coating does not contain carbon black.

[0058] Effect evaluation: The following performance tests were performed on the overhead transmission lines prepared in Example 1 and Comparative Examples 1 to 4: (1) Room temperature emissivity was measured using a portable emissivity meter according to ASTM C1371 standard; (2) The emissivity at normal operating temperature (approximately 80°C) was measured using a Fourier transform infrared spectrometer (FTIR) according to ASTM E408 standard; (3) Coating adhesion, determined according to ASTM D3359 cross-cut adhesion test; (4) Bending resistance: bend the rod around a shaft with a diameter of 10 times the outer diameter of the wire by 180° and observe whether the coating cracks or peels off. (5) Elongation at break, determined according to GB / T 1731-2020 standard; (6) Neutral salt spray test (NSS), 1000h test according to ASTM B117 standard, observe whether the coating blister; (7) Ultraviolet accelerated aging test: 1500h test according to ASTM G154 standard, and the emissivity attenuation rate after aging was measured. The final test results are shown in Table 1.

[0059] Table 1. Detailed test data for Example 1 and each comparative example.

[0060] In terms of emissivity, Example 1 showed an emissivity of 0.92 at room temperature and 0.80 at 80°C, both higher than the four comparative examples. Comparative Example 3, which did not contain hexagonal boron nitride, had an emissivity of only 0.58 at 80°C, failing to meet the requirement of 0.6, indicating that hexagonal boron nitride contributed the most to the high-temperature emissivity. Comparative Example 2, which did not contain silica fume, also showed a decrease in emissivity. Comparative Example 4, which did not contain carbon black, showed a slight decrease in emissivity, but the magnitude was limited, with carbon black playing a supplementary reinforcing role. Comparative Example 1, which used ordinary polyester instead of silicone-modified polyester, also showed a significant decrease in emissivity.

[0061] Regarding adhesion, Example 1 was rated at level 0, Comparative Example 1 at level 2, and the rest at level 1. The silanol groups in the silicone-modified polyester resin form chemical bonds with the aluminum matrix surface, playing a key role in adhesion; ordinary polyester resins do not possess this characteristic.

[0062] The bending test and elongation at break results showed that Comparative Example 1 had microcracks and an elongation at break of only 4.2%, while the other samples had no cracks and an elongation at break between 7.8% and 8.5%. This indicates that the Si-O-Si bonds and flexible siloxane segments in the silicone-modified polyester resin molecular chain give the coating good flexibility. Ordinary polyester resin has a high crosslinking density and few flexible segments, and is brittle after curing.

[0063] In the salt spray test, only the edge of Comparative Example 1 showed slight bubbling, while the rest showed no bubbling.

[0064] After UV aging, the emissivity of Example 1 decreased by 4.5%, Comparative Example 1 by 12.0%, and the rest were between 6.0% and 8.0%. The bond energy of Si-O-Si bonds is higher than that of C-C bonds and ester bonds, making them more stable under UV irradiation. Therefore, the aging resistance of silicone-modified polyester resin is better than that of ordinary polyester resin.

[0065] In summary, Example 1 outperformed all the comparative examples in all aspects. The advantages of silicone-modified polyester resin are reflected in adhesion, flexibility, and aging resistance; silica fume and hexagonal boron nitride are key components for improving emissivity, with hexagonal boron nitride playing a decisive role in ensuring that the high-temperature emissivity meets the standard; carbon black, as an auxiliary filler, has a reinforcing effect on emissivity, but its absence alone has a relatively limited impact.

[0066] The overhead transmission conductors treated by this invention have an emissivity of ≥0.90 at room temperature and ≥0.78 at normal operating temperature; the coating does not crack when bent 180° around a shaft with a diameter 10 times the outer diameter of the conductor; the adhesion is grade 0; there is no blistering after 1000h of neutral salt spray; and the emissivity decays by ≤5% after 1500h of ultraviolet aging.

[0067] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines, characterized in that, Includes the following steps: S11: At 95-105℃, a composite coating material is applied to the surface of the pretreated overhead transmission line; the composite coating material includes organosilicon-modified polyester resin, nano-sized silica fume, hexagonal boron nitride, carbon black, additives and solvents. S12: After the overhead transmission line is coated in step S11, heat it at 80-95℃ for 1.5-2.5 min, cure it at 120-135℃ for 2.5-3.5 min, and keep it at 110-125℃ for 0.5-1 min. S13: Cool the overhead power transmission line after heat preservation in step S12 to 40°C or below to complete the surface treatment method.

2. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: In step S11, the pretreatment method is to perform sandblasting at 0.5-0.7 MPa and the sandblasting speed is 10-18 m / min.

3. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: In step S11, the composite coating material, by weight, comprises 40-60 parts of silicone-modified polyester resin, 15-25 parts of nano-sized silica fume, 5-10 parts of hexagonal boron nitride, 3-6 parts of carbon black, 1-3 parts of additives, and 20-30 parts of solvent.

4. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: The additives include dispersants, defoamers, and leveling agents.

5. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: The solvent consists of xylene and butyl ester in a mass ratio of 6-8:

3.

6. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: In step S11, the coating method is air spraying, and the flow rate during spraying is 60-120 mL / min.

7. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: In step S11, the coating thickness is 25-40 μm.

8. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: In step S12, the rate of temperature change between heating, curing, and heat preservation is 0.5-1.0℃ / min.

9. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: In step S13, cooling is performed at a rate of 0.2-0.4℃ / min.

10. The surface treatment method for improving the blackbody radiation coefficient of overhead transmission lines according to claim 1, characterized in that: In step S13, after cooling, the wire mesh is stranded using a frame stranding machine at a speed of 10-18 m / min.

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