Epoxy CCTO gradient coating method for improving flashover characteristic of alternating current insulator and prepared epoxy CCTO gradient non-uniform modified insulator
By using an epoxy CCTO gradient coating method on the surface of insulators, non-uniformly modified insulators were prepared, which solved the problem of easy flashover on the surface of insulators, optimized the electric field distribution and improved the flashover voltage, and reduced the failure rate of high-voltage equipment.
Patent Information
- Application Number
- CN202511856235.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-02-27
AI Technical Summary
Surface flashover is prone to occur on the surface of existing insulators, and traditional methods are difficult to effectively control the electric field distribution, resulting in a high risk of flashover in high-voltage equipment.
An epoxy CCTO gradient coating method was used to divide the insulator into multiple layers, and different amounts of CCTO slurry were coated on each layer to form a non-uniform electric field gradient distribution. By adjusting the amount of CCTO added and the coating hardness, epoxy CCTO gradient non-uniform modified insulators were prepared.
It significantly reduces the flashover failure rate of high-voltage equipment and improves the operational reliability of the power system. By optimizing the electric field distribution on the surface of the insulator through a non-uniform gradient structure, it suppresses the development of partial discharge.
Smart Images
Figure CN121583667A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of high-voltage equipment insulation technology, specifically relating to an epoxy CCTO gradient coating method for improving the flashover characteristics of AC insulators and the prepared epoxy CCTO gradient non-uniform modified insulator. Background Technology
[0002] In high-voltage power transmission and transformation systems, insulators are core components ensuring the insulation reliability of electrical equipment. Their surfaces are prone to surface flashover, which seriously affects the safe operation of the power grid. AC surface flashover refers to a penetrating discharge phenomenon occurring at the gas-solid interface under the influence of the electric field on the insulator surface. Essentially, it is the result of uneven electric field distribution on the insulator surface leading to the gradual development of partial discharge. Particularly in power equipment such as GIS (Gas Insulator System), the distortion of the electric field on the insulator surface is exacerbated, significantly increasing the risk of flashover and becoming a key bottleneck restricting the miniaturization and compact design of high-voltage equipment.
[0003] Traditional methods for improving the flashover voltage of insulators mainly include optimizing the insulator's shape and structure, coating the surface with a uniform insulating coating, or using a semiconductor glaze. However, uniform insulating coatings can only improve the flashover voltage by increasing the properties of the insulating material, and their ability to control the structured electric field distribution is insufficient. While semiconductor glazes can improve the surface conductivity distribution, their linear conductivity characteristics are difficult to adjust gradients over a wide electric field range. In recent years, functionally graded materials (FJTs), due to their ability to continuously or abruptly change their properties along space, can locally adjust electric field distortion, becoming an emerging direction for improving the surface flashover performance of insulators. By coating the insulator surface with a coating that exhibits a gradient distribution of dielectric constant or conductivity, the electric field distortion at the high-voltage end can be alleviated, achieving uniformity of the surface electric field and fundamentally suppressing the development of partial discharge. Summary of the Invention
[0004] The technical problem to be solved by this invention is how to solve the problem of poor performance of existing insulators and the tendency for surface flashover to occur on the surface.
[0005] The present invention solves the above-mentioned technical problems through the following technical means: This invention proposes an epoxy CCTO gradient coating method to improve the flashover characteristics of AC insulators, comprising the following steps: (1) After mixing epoxy resin, calcium copper titanate (CCTO), dispersant and catalyst, add curing agent and stir evenly. By adjusting the amount of calcium copper titanate (CCTO) added, slurries with different CCTO contents can be prepared. (2) Divide the insulator into four layers from bottom to top, which are the first to fourth layers from bottom to top. After coating each layer with a slurry containing different amounts of CCTO, the insulator is cured. (3) Using a hardness tester, randomly select 5 points for each layer to measure the surface hardness of the coating. If the hardness value reaches the target hardness, proceed to the next step. If the hardness value does not meet the standard, perform a second curing. Obtain epoxy CCTO gradient non-uniform modified insulator.
[0006] Preferably, in step (1), the total mass percentage of the epoxy resin, calcium copper titanate (CCTO), dispersant, catalyst, and curing agent is 100%, wherein the mass fraction of calcium copper titanate (CCTO) is 10~25wt%, and the mass ratio of epoxy resin, dispersant, catalyst, and curing agent is 100:(0.5~1.5):(0.3~0.8):(85~95); more preferably, it is 100:1:0.5:90.
[0007] Preferably, in step (1), the epoxy resin is a bisphenol A type epoxy resin, and more preferably a bisphenol A type epoxy resin E51.
[0008] Preferably, in step (1), the dispersant is a polymeric dispersant, more preferably BYK-110.
[0009] Preferably, in step (1), the catalyst is triethanolamine.
[0010] Preferably, in step (1), the curing agent is an acid anhydride curing agent, and more preferably methylhexahydrophthalic anhydride.
[0011] Preferably, in step (1), the stirring is specifically stirring at a speed of 790~810 rpm for 9~11 minutes.
[0012] Preferably, in step (1), the secondary stirring is specifically stirring at a speed of 395~405 rpm for 9~11 minutes.
[0013] Preferably, in step (2), the insulator is a basin-type insulator with a height of 14.8~15.2mm, an upper surface radius of 14.8~15.2mm, and a lower surface radius of 29.8~30.2mm.
[0014] Preferably, in step (2), the first layer area is 0.45~0.55mm, the second layer area is 1.95~2.05mm, the third layer area is 6.45~6.55mm, and the fourth layer area is 5.95~6.05mm; the coating thickness of each layer is the same, which is 0.45~0.55mm.
[0015] Preferably, in step (2), the slurry sprayed in each layer is as follows: the first layer is sprayed with a slurry containing 25% CCTO, the second layer is sprayed with a slurry containing 20% CCTO, the third layer is sprayed with a slurry containing 15% CCTO, and the fourth layer is sprayed with a slurry containing 10% CCTO.
[0016] Preferably, in step (2), the spraying conditions are: pressure of 0.15~0.25MPa.
[0017] Preferably, in step (2), the settling time is 29 to 31 minutes.
[0018] Preferably, in step (2), the curing conditions are: temperature of 55~65℃ and time of 110~130 minutes.
[0019] Preferably, in step (2), the insulator is pretreated before coating: the insulator is ultrasonically cleaned with anhydrous ethanol and then placed in a drying oven for drying.
[0020] Preferably, in step (3), the target hardness of each layer is as follows: the first layer is 180~220HV, the second layer is 135~185HV, the third layer is 90~150HV, and the fourth layer is 70~110HV.
[0021] Preferably, the process further includes immersing the obtained epoxy CCTO gradient non-uniform modified insulator in anhydrous ethanol, ultrasonically cleaning it, and then drying it in a forced-air drying oven.
[0022] This invention also proposes epoxy CCTO gradient non-uniform modified insulators obtained by the above-mentioned epoxy CCTO gradient coating method. The beneficial effects of this invention are as follows: This invention proposes a CCTO (calcium copper titanate) gradient coating technology for precise control of key components of insulators. Compared to traditional linear materials, the nonlinear characteristics of CCTO can achieve more significant electric field attenuation in strong electric field regions and maintain sufficient insulation strength in weak electric field regions, thereby breaking through the performance limit of linear gradient coatings.
[0023] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description
[0024] Figure 1 This is a graph showing the dielectric constant-frequency relationship for different CCTO contents according to the present invention; Figure 2 These are surface electric field distribution diagrams of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 3 These are the broken lines showing the maximum electric field strength and non-uniformity of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 4 These are Weibull distribution diagrams of AC surface flashover voltages in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed Implementation
[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.
[0026] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.
[0027] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.
[0028] Example 1: (1) Insulator pretreatment: Use anhydrous ethanol to ultrasonically clean the basin insulator. The ultrasonic frequency is set to 40kHz and the ultrasonic duration is 15 minutes to remove oil and impurities from the surface of the insulator. After cleaning, place it in an 80℃ forced-air drying oven for 120 minutes to dry the surface completely.
[0029] (2) Preparation of coating slurry: Weigh each raw material according to the mass ratio of epoxy resin E51, dispersant BYK-110, catalyst triethanolamine, and curing agent methylhexahydrophthalic anhydride of 100:1:0.5:90; Then, based on the total mass percentage of epoxy resin E51, calcium copper titanate (CCTO), dispersant BYK-110, catalyst triethanolamine, and curing agent methylhexahydrophthalic anhydride being 100%, the calcium copper titanate (CCTO) mass fraction is 25wt%. Weigh out epoxy resin E51, calcium copper titanate (CCTO), dispersant BYK-110 and catalyst triethanolamine and pour them into a mixer. Mix at 800 rpm for 10 minutes, then add curing agent methyl hexahydrophthalic anhydride and mix at 400 rpm for 10 minutes to obtain 25% CCTO epoxy resin mixed slurry (referred to as 25% CCTO slurry). Similarly, by changing the mass fraction of calcium copper titanate (CCTO) to 20wt%, 15wt%, and 10wt%, while keeping other parameters unchanged, 20% CCTO epoxy resin mixed slurry, 15% CCTO epoxy resin mixed slurry, and 10% CCTO epoxy resin mixed slurry were prepared. (These are referred to as 20% CCTO slurry, 5% CCTO slurry, and 10% CCTO slurry, respectively.) (3) Coating: The basin insulator obtained in step (1) is non-uniformly divided into 4 layers from bottom to top (i.e. along the axial direction (height direction)). The first layer has a height of 0.5 mm, the second layer has a height of 2 mm, the third layer has a height of 6.5 mm, and the fourth layer has a height of 6 mm (i.e. from bottom to top, the layers are the first, second, third, and fourth layers). Each layer of the coating slurry has the same thickness of 0.5mm. Specifically, use a spray gun, set the spraying pressure to 0.2MPa, and the spraying distance to 15cm. First, spray the 25% CCTO slurry onto the first layer area of the insulator, and let it stand for 30 minutes after spraying.
[0030] Second coating: Cover the area of the insulator that has been coated with the first layer with a sticker, and spray the second layer area with 20% CCTO slurry. The spraying process is the same as the first layer. Let it stand for 30 minutes after spraying.
[0031] Third coating: Cover the second layer area of the insulator with stickers, and spray the third layer area with 15% CCTO slurry. The spraying process is the same as the first layer. Let it stand for 30 minutes after spraying.
[0032] Fourth coating: Cover the area of the insulator that has been sprayed with the third layer with a sticker, and spray the fourth layer area with 10% CCTO slurry. The spraying process is the same as the first layer. After spraying, place the insulator in a 60℃ constant temperature oven for 120 minutes to cure.
[0033] (4) Coating inspection: The surface hardness of the obtained insulator coating was measured using a hardness tester. Five points were randomly selected for measurement of each layer (the average of the measurement results was taken). The hardness of the first layer was 200 HV, the second layer was 160 HV, the third layer was 120 HV, and the fourth layer was 90 HV. (If the hardness of each layer meets the target hardness, proceed to the next step; if not, place the insulator in a constant temperature chamber for secondary curing). Thus, the epoxy CCTO gradient non-uniform modified insulator is obtained.
[0034] (5) Immerse the basin insulator obtained in step (4) in anhydrous ethanol and clean it with ultrasonic cleaning. The ultrasonic frequency is set to 40kHz and the ultrasonic duration is 15 minutes. After cleaning, place it in an 80℃ drying oven to dry for 120 minutes.
[0035] Example 2: The difference between this embodiment and Embodiment 1 is that: In step (1), the ultrasonic treatment lasts for 14 minutes; after cleaning, the sample is placed in a 75°C forced-air drying oven for 130 minutes to dry. In step (2), stir at 800 rpm for 9 minutes; then add the curing agent and continue stirring at 400 rpm for 9 minutes. In step (3), the first layer has a height of 0.45 mm, the second layer has a height of 1.95 mm, the third layer has a height of 6.45 mm, and the fourth layer has a height of 5.95 mm. The thickness of each layer of coating is the same, 0.45 mm. The spraying pressure is set to 0.15 MPa and the spraying distance is 14 cm.
[0036] The settling time after each coat is 29 minutes. After spraying, place it in a 55℃ constant temperature oven for curing for 110 minutes.
[0037] In step (4), the hardness of the first layer was measured to be 180 HV, the hardness of the second layer was 135 HV, the hardness of the third layer was 90 HV, and the hardness of the fourth layer was 70 HV.
[0038] In step (5), the ultrasonic treatment lasts for 14 minutes, and after cleaning, the product is placed in a 75°C forced-air drying oven for 130 minutes to dry.
[0039] The rest is the same as in Example 1.
[0040] Example 3: The difference between this embodiment and Embodiment 1 is that: In step (1), the ultrasonic treatment lasts for 16 minutes; after cleaning, the sample is placed in an 85℃ forced-air drying oven for 110 minutes to dry. In step (2), stir at 800 rpm for 11 minutes; then add the curing agent and continue stirring at 400 rpm for 11 minutes. In step (3), the first layer has a height of 0.55 mm, the second layer has a height of 2.05 mm, the third layer has a height of 6.55 mm, and the fourth layer has a height of 6.05 mm. The thickness of each layer of coating is the same, 0.5 mm. The spraying pressure is set to 0.25 MPa and the spraying distance is 16 cm.
[0041] The settling time after each coat is 31 minutes. After spraying, place it in a 65℃ constant temperature oven for curing for 110 minutes.
[0042] In step (4), the hardness of the first layer was measured to be 220 HV, the hardness of the second layer was 185 HV, the hardness of the third layer was 150 HV, and the hardness of the fourth layer was 110 HV.
[0043] In step (5), the ultrasonic treatment lasts for 16 minutes, and after cleaning, the product is placed in an 85°C forced-air drying oven for 110 minutes to dry.
[0044] The rest is the same as in Example 1.
[0045] Comparative Example 1: The difference between this comparative example and Example 1 is that no slurry was applied after the insulator pretreatment.
[0046] Unmodified insulators were obtained.
[0047] Comparative Example 2: The difference between this comparative example and Example 1 is as follows: In step (3), the insulator is divided into four layers from bottom to top, with the height of the first, second, third, and fourth layers all being 3.75 mm. The rest is the same as in Example 1.
[0048] Obtain epoxy CCTO gradient uniformly modified insulators.
[0049] Test (one) Dielectric property testing experiments were conducted under stable conditions created within a broadband dielectric spectrometer. During frequency testing, a logarithmic scan mode was used, starting at 100 Hz and ending at 106 Hz. Frequency-dielectric property testing. (For example...) Figure 1 As shown in the experimental data, the dielectric constant of the AC insulator increases significantly with increasing CCTO content. When the CCTO content is 25%, the dielectric constant is significantly higher than that without CCTO within the frequency range. Furthermore, the dielectric constant of the material varies with frequency for different CCTO contents, which provides the possibility of precisely adjusting the dielectric properties of the insulator according to actual operating conditions. This indicates that appropriate dielectric constant and frequency response characteristics can optimize the electric field distribution on the insulator surface, suppress partial discharge, thereby improving its flashover voltage and insulation reliability, effectively solving the flashover problem of existing AC insulators under complex operating conditions, and ensuring the stable operation of high-voltage transmission systems. (two) Using simulation software, the number of coating layers was set to four, each with a thickness of 0.5 mm. The CCTO ratios were 25%, 20%, 15%, and 10%, and the coating layer heights were set to uniform and non-uniform distributions. The electric field distribution on the insulator surface was simulated. Comparative examples 1, 1, and 2 are shown below. Figure 2 , Figure 3 As shown.
[0051] The results show that the electric field strength in all three cases (unmodified, uniformly modified, and non-uniformly modified) decreases with increasing creepage distance. At the initial stage of creepage distance, near the high-voltage electrode, the electric field strength is significantly higher than the other two modification methods, indicating severe electric field concentration near the high-voltage end in the unmodified insulator, which can easily lead to problems such as partial discharge. In the uniform modification scheme, the electric field strength is significantly reduced compared to the unmodified scheme over the entire creepage distance, and the distribution is relatively gentle, but the electric field non-uniformity is still not ideal. In the non-uniform modification scheme, the reduction in electric field strength is most significant, especially near the high-voltage end, where it further reduces the electric field strength compared to uniform modification, and the electric field strength distribution is more uniform over the entire creepage distance. This indicates that non-uniform modification has the best optimization effect on the electric field distribution and can effectively alleviate electric field distortion at the high-voltage end. (three) Surface flashover experiments were conducted on Example 1, Comparative Example 1, and Comparative Example 2 with different CCTO gradient treatment schemes. The test atmosphere was SF6 gas at 0.1 MPa. The test adopted the stepwise pressure increase method with a pressure increase rate of 1 kV / s. Three samples of each example were tested, and each sample was tested five times. Figure 4 Weibull distribution of surface flashover voltage for basin insulators with different gradient coating treatments.
[0053] Experimental results show that, under SF6 gas conditions at 0.1 MPa and using a step-up voltage method at a rate of 1 kV / s, both uniform and non-uniform modification schemes effectively suppressed surface flashover compared to unmodified insulators. Specifically, uniform modification increased the flashover voltage by 9.7%, while non-uniform modification increased it by 11.3%. This performance improvement stems from the optimization effect of the non-uniform gradient structure on the electric field distribution on the insulator surface. By controlling the CCTO content to create a dielectric constant gradient in different regions, local electric field distortion is effectively suppressed, and the discharge development process is delayed. This technical solution can significantly reduce the flashover failure rate of high-voltage equipment and improve the operational reliability of power systems.
[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for improving the flashover characteristics of AC insulators using epoxy CCTO gradient coating, characterized in that, Includes the following steps: (1) After mixing epoxy resin, calcium copper titanate (CCTO), dispersant and catalyst, add curing agent and stir evenly. By adjusting the amount of calcium copper titanate (CCTO) added, slurries with different CCTO contents can be prepared. (2) Divide the insulator into four layers from bottom to top, which are the first to fourth layers from bottom to top. After coating each layer with a slurry containing different amounts of CCTO, the insulator is cured. (3) Using a hardness tester, randomly select 5 points for each layer to measure the surface hardness of the coating. If the hardness value reaches the target hardness, proceed to the next step; if the hardness value does not meet the standard, perform a second curing. Obtain epoxy CCTO gradient non-uniform modified insulators.
2. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (1), the total mass percentage of the epoxy resin, calcium copper titanate (CCTO), dispersant, catalyst and curing agent is 100%, wherein the mass fraction of calcium copper titanate (CCTO) is 10~25wt%, and the mass ratio of epoxy resin, dispersant, catalyst and curing agent is 100:(0.5~1.5):(0.3~0.8):(85~95).
3. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (1), the epoxy resin is a bisphenol A type epoxy resin; the dispersant is a polymeric dispersant, more preferably BYK-110.
4. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (1), the catalyst is triethanolamine; the curing agent is an acid anhydride curing agent, more preferably methylhexahydrophthalic anhydride.
5. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (1), the stirring is specifically stirring at a speed of 790~810 rpm for 9~11 minutes; the secondary stirring is specifically stirring at a speed of 395~405 rpm for 9~11 minutes.
6. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (2), the first layer area is 0.45~0.55mm, the second layer area is 1.95~2.05mm, the third layer area is 6.45~6.55mm, and the fourth layer area is 5.95~6.05mm; the coating thickness of each layer is the same, which is 0.45~0.55mm.
7. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (2), the slurry sprayed in each layer is as follows: the first layer is sprayed with a slurry containing 25% CCTO, the second layer is sprayed with a slurry containing 20% CCTO, the third layer is sprayed with a slurry containing 15% CCTO, and the fourth layer is sprayed with a slurry containing 10% CCTO.
8. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (2), the spraying conditions are: pressure of 0.15~0.25MPa; standing time of 29~31 minutes; and curing conditions are: temperature of 55~65℃ and time of 110~130 minutes.
9. The epoxy CCTO gradient coating method according to claim 1, characterized in that, In step (3), the target hardness of each layer is as follows: the first layer is 180~220HV, the second layer is 135~185HV, the third layer is 90~150HV, and the fourth layer is 70~110HV.
10. The epoxy CCTO gradient non-uniform modified insulator obtained by the epoxy CCTO gradient coating method according to any one of claims 1-9.