A nonlinear material gradient coating method for improving insulator surface flashover

Abstract

The present invention provides a nonlinear material gradient coating method for improving surface flashover of insulators, belonging to the technical field of high-voltage insulation materials. For pot-type insulators, a nonlinear material SiC is used as a coating material. SiC is added to epoxy resin at different mass fractions as a coating layer and coated on the pot-type insulator surface. The electric field distribution on the insulator surface is simulated using Comsol software. Subsequently, by varying the number, thickness, and height of the coating layer, the electric field distribution patterns of the number, thickness, and height of the coating layer on the insulator surface are summarized. Finally, a coating layer with three layers, a thickness of 0.5 mm, and a non-uniform height distribution (1.1 mm, 2.8 mm, and 11.1 mm) is selected, thus determining the nonlinear material gradient coating method for improving surface flashover of insulators. The present invention uses the above-mentioned nonlinear material gradient coating method for improving surface flashover of insulators to improve the DC surface flashover voltage of pot-type insulators in SF6 atmosphere. The coating method is low in difficulty and highly operable.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage insulating materials, and in particular to a nonlinear material gradient coating method for improving surface flashover of insulators. Background Art

[0002] Epoxy resins are widely used in power equipment due to their excellent electrical, mechanical, and thermal properties, such as pot insulators, which are important supporting and insulating components in ultra-high voltage GIS. However, the surface flashover voltage of pot insulators is much lower than the breakdown voltage of an air gap of the same size or the bulk of the insulating material, which seriously restricts the insulation performance of the electrical system and the miniaturization of high-voltage electrical equipment. When a surface flashover occurs on the surface of a pot insulator, it is accompanied by a large amount of energy loss, causing ablation and degradation at the flashover location, resulting in a decrease in its insulation strength, which then develops into insulation breakdown, leading to system insulation collapse, and ultimately causing electrical equipment failure or even power system paralysis. Therefore, methods to improve the surface flashover performance of insulating materials are of great significance for practical engineering applications.

[0003] At present, the concept of "functionally gradient materials" has been widely introduced in the field of electrical insulation materials. Functionally gradient materials refer to a new type of composite material composed of two or more materials with a continuous gradient change in composition and structure. In the field of insulating materials, it is hoped that the electrical parameters of the material will show a continuous gradient change in space, so as to effectively control the field strength distribution in each area. Traditional gradient modification mainly targets the entire insulator, including lamination method, centrifugal method, 3D printing and flexible casting method, etc., to achieve a gradient distribution of electrical parameters inside the insulator. However, how to combine surface modification technology to achieve a gradient distribution of electrical parameters by gradient coating of nonlinear materials, thereby further improving the surface flashover voltage of the insulator and obtaining specific and effective methods has gradually attracted attention in the engineering field. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a nonlinear material gradient coating method for improving the surface flashover of insulators, thereby improving the DC surface flashover voltage of pot-type insulators in SF6 atmosphere, and the coating method is low in difficulty and highly operable.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A nonlinear material gradient coating method for improving surface flashover of an insulator comprises the following steps: adding nonlinear material SiC in different mass fractions into epoxy resin to obtain a coating layer, adding the coating layer to the surface of an insulator, and inverting the surface trap energy level and density of the insulator by measuring the surface conductivity and surface potential decay of the coating layer.

[0007] Preferably, the coating method comprises the following steps:

[0008] S1. Establish a basin insulator model based on Comsol, add the coating layer to the insulator surface, and simulate to obtain the electric field distribution on the insulator surface;

[0009] S2. Changing the number of coating layers on the surface of the insulator, simulating the electric field distribution on the surface of the insulator using the basin-type insulator model, summarizing the variation pattern of the electric field on the surface of the insulator with the number of coating layers, and determining the number of coating layers;

[0010] S3, changing the thickness of the coating layer on the surface of the insulator, simulating the electric field distribution on the surface of the insulator through the basin insulator model, summarizing the variation pattern of the electric field on the surface of the insulator with the thickness of the coating layer, and determining the thickness of the coating layer;

[0011] S4, changing the height of the coating layer on the insulator surface, simulating the electric field distribution on the insulator surface through the basin insulator model, summarizing the variation pattern of the electric field on the insulator surface with the height of the coating layer, and determining the height of the coating layer;

[0012] S5. According to the determined number of layers, thickness and height of the coating layer on the surface of the insulator, obtain the nonlinear material gradient coating method for improving the surface flashover of the insulator.

[0013] Preferably, in step S1, the coating layer is a composite insulating material, and the mass fractions of the nonlinear material SiC are 5%, 7.5%, 10%, 12.5% and 15% respectively.

[0014] Preferably, in step S1, the type of the insulator is a pot-type insulator, the height of the insulator is 15 mm, the upper surface radius of the insulator is 15 mm, and the lower surface radius of the insulator is 30 mm.

[0015] Preferably, in step S2, the number of layers of the coating layer on the surface of the insulator is 1 layer, 3 layers, or 5 layers respectively.

[0016] Preferably, in step S2, the number of layers of the coating layer is 1, and the mass fraction of the corresponding nonlinear material SiC is 15%; the number of layers of the coating layer is 3, and the mass fractions of the corresponding nonlinear material SiC are 15%, 12.5%, and 10%; the number of layers of the coating layer is 5, and the mass fractions of the corresponding nonlinear material SiC are 15%, 12.5%, 10%, 7.5%, and 5%; wherein the thickness of each coating layer is 0.5 mm, and the height of the coating layer is uniformly distributed.

[0017] Preferably, in step S3, the thickness of the coating layer on the surface of the insulator is 0.1 mm, 0.5 mm, and 1 mm respectively.

[0018] Preferably, in step S3, the number of layers of the coating layer on the surface of the insulator is 3, corresponding to the mass fractions of the nonlinear material SiC of 15%, 12.5% and 10%, and the height of the coating layer is uniformly distributed.

[0019] Preferably, in step S4, the coating layer is uniformly distributed or non-uniformly distributed at the height of the surface of the insulator.

[0020] Preferably, in step S4, the number of layers of the coating layer on the surface of the insulator is 3, corresponding to the mass fraction of the nonlinear material SiC is 15%, 12.5%, 10%, and the thickness of the coating layer is 0.5 mm.

[0021] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] (1) The present invention uses a nonlinear material gradient coating on the surface of a basin insulator, and regulates the number, thickness, and height of the coating layer to modify the surface of the insulator. The surface electric field distribution and surface traps of the prepared insulator undergo significant changes. Compared with unmodified insulators, coatings of different numbers, thicknesses, and heights on the surface of the basin insulator can improve the surface electric field distribution of the insulator to varying degrees and reduce the electric field distortion of the high-voltage pole.

[0023] (2) The present invention adds different mass fractions of nonlinear material SiC to the epoxy resin. Compared with pure epoxy resin, the addition of different mass fractions of nonlinear material SiC can improve the surface charge transport ability of the insulator in a high electric field, promote surface charge dissipation, and reduce surface charge accumulation of the insulator, thereby improving the surface flashover performance of the insulator material.

[0024] (3) The results of DC surface flashover according to the present invention show that: compared with the unmodified insulator sample, the surface flashover voltage of the uniformly modified sample is increased by 17.01%, and the surface flashover voltage of the non-uniformly modified sample is increased by 21.89%. This is because, on the one hand, the gradient coating makes the electric field distribution on the surface of the insulator more uniform and reduces the distortion of the electric field; on the other hand, the nonlinear material SiC coated on the surface of the insulator reduces the surface shallow trap energy level and increases the density, making the charge easier to dissipate and less likely to accumulate, which helps to suppress the field strength distortion of the high-voltage triple junction, thereby making surface flashover relatively less likely to occur, which is ultimately manifested as an increase in surface flashover voltage; this proves that the method proposed in the present invention can improve the DC surface flashover voltage of the basin insulator in SF6 atmosphere, and the coating method is low in difficulty and highly operational. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a flow chart of a method for improving the nonlinear material gradient coating of insulator surface flashover according to the present invention;

[0027] Figure 2 The electric field distribution diagram of the insulator surface with different numbers of coating layers provided by the present invention;

[0028] Figure 3 The electric field distribution diagram of the insulator surface with different coating thicknesses provided by the present invention;

[0029] Figure 4 The electric field distribution diagram of the insulator surface with different coating layer heights provided by the present invention;

[0030] Figure 5 Surface potential attenuation diagram of SiC with different mass fractions provided by the present invention;

[0031] Figure 6 Surface trap energy level density diagram of SiC with different mass fractions provided by the present invention;

[0032] Figure 7 The present invention provides Weibull distribution diagrams of surface flashover voltage of insulators under three different conditions. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings.

[0035] The present invention provides a nonlinear material gradient coating method for improving surface flashover of an insulator. The method comprises adding different mass fractions of nonlinear material SiC into epoxy resin to obtain a coating layer, which is then added to the surface of an insulator. The surface conductivity and surface potential decay of the coating layer are tested, and the surface trap energy level and density of the insulator are inverted to obtain the surface.

[0036] Reference Figure 1 The above coating method specifically comprises the following steps:

[0037] S1. Establish a basin insulator model based on Comsol, add the coating layer to the insulator surface, and simulate to obtain the electric field distribution on the insulator surface;

[0038] S2. Changing the number of coating layers on the surface of the insulator, simulating the electric field distribution on the surface of the insulator using the basin-type insulator model, summarizing the variation pattern of the electric field on the surface of the insulator with the number of coating layers, and determining the number of coating layers;

[0039] S3, changing the thickness of the coating layer on the surface of the insulator, simulating the electric field distribution on the surface of the insulator through the basin insulator model, summarizing the variation pattern of the electric field on the surface of the insulator with the thickness of the coating layer, and determining the thickness of the coating layer;

[0040] S4, changing the height of the coating layer on the insulator surface, simulating the electric field distribution on the insulator surface through the basin insulator model, summarizing the variation pattern of the electric field on the insulator surface with the height of the coating layer, and determining the height of the coating layer;

[0041] S5. According to the determined number of layers, thickness and height of the coating layer on the surface of the insulator, obtain the nonlinear material gradient coating method for improving the surface flashover of the insulator.

[0042] Specifically, in step S1, the coating layer is a composite insulating material, and the mass fractions of the nonlinear material SiC are 5%, 7.5%, 10%, 12.5%, and 15%, respectively; the type of the insulator is a pot insulator, the height of the insulator is 15 mm, the upper surface radius of the insulator is 15 mm, and the lower surface radius of the insulator is 30 mm.

[0043] Specifically, in step S2, the number of coating layers on the surface of the insulator is 1, 3, and 5 layers respectively. When the number of coating layers is 1, the mass fraction of the corresponding nonlinear material SiC is 15%; when the number of coating layers is 3, the mass fractions of the corresponding nonlinear material SiC are 15%, 12.5%, and 10%; when the number of coating layers is 5, the mass fractions of the corresponding nonlinear material SiC are 15%, 12.5%, 10%, 7.5%, and 5%; wherein the thickness of the coating layers is 0.5 mm, and the height of the coating layers is uniformly distributed. Figure 2 , the simulation obtained the electric field distribution diagram of the insulator surface. The comparison found that with the increase of the number of coating layers, the maximum electric field intensity and unevenness gradually decreased, and the surface electric field became more uniform.

[0044] Specifically, in step S3, the thickness of the coating layer on the surface of the insulator is 0.1mm, 0.5mm, and 1mm respectively. The number of layers of the coating layer on the surface of the insulator is 3, and the mass fraction of the corresponding nonlinear material SiC is 15%, 12.5%, and 10%, and the height of the coating layer is uniformly distributed. Figure 3 ,The simulation obtained the electric field distribution diagram on the ,insulator surface. By comparison, it was found that as the coating thickness ,increases, the maximum electric field intensity decreases slightly and the ,uniformity changes very little.

[0045] Specifically, in step S4, the height of the coating layer on the surface of the insulator is uniformly distributed and non-uniformly distributed. The number of layers of the coating layer on the surface of the insulator is 3, and the mass fraction of the corresponding nonlinear material SiC is 15%, 12.5%, and 10%, and the thickness of the coating layer is 0.5 mm. Figure 4 , the simulation results show the electric field distribution on the insulator surface. The comparison shows that the non-uniform distribution has a better modification effect than the uniform distribution.

[0046] In summary, the number of coating layers is selected as 3, the SiC proportions are 15%, 12.5%, and 10%, the thickness of the coating layer is 0.5 mm, and the height of each coating layer is 1.1 mm, 2.8 mm, and 11.1 mm, respectively. A nonlinear material gradient coating method for improving the surface flashover of insulators can be obtained.

[0047] The present invention will be further described below through specific implementation methods.

[0048] (1) SiC with mass fractions of 5%, 7.5%, 10%, 12.5%, and 15% was added to epoxy resin as a coating layer, and the surface potential decay of the composite insulating material was tested, and the surface trap energy level and density were inverted, such as Figure 5 and Figure 6As shown in the figure, by comparison, it is found that the addition of nonlinear material SiC with different mass fractions can reduce the surface shallow trap energy level and increase the trap density, thereby improving the surface charge transport ability of the insulator in high electric field, promoting surface charge dissipation, and reducing the surface charge accumulation of the insulator.

[0049] (2) By changing the parameters of the coating layer, the electric field distribution on the surface of the insulator under different conditions is simulated and compared to determine the parameters of the coating layer.

[0050] Example 1

[0051] In this embodiment, the electric field distribution on the surface of the insulator is simulated and compared by changing the number of coating layers, and the thickness of the coating layer is set to 0.5 mm, and the height of each coating layer is uniformly distributed.

[0052] The number of layers of the above coating layers are 1 layer, 3 layers, and 5 layers, and the SiC ratios are 15% (1 layer), 15%, 12.5%, and 10% (3 layers), and 15%, 12.5%, 10%, 7.5%, and 5% (5 layers). Figure 2 As shown in Figure 1, the simulation results show the electric field distribution on the insulator surface, and the specific parameters of the electric field on the surface of the insulator with different numbers of coating layers are shown in Table 1.

[0053] Table 1 Surface electric field parameters of insulators coated with different numbers of coating layers

[0054]

[0055] Reference Figure 2 Compared with Table 1, it is found that as the number of coating layers increases, the maximum electric field strength and unevenness gradually decrease, the surface electric field becomes more uniform, and the field strength distortion at the high-voltage triple junction decreases. Based on this, in the actual coating method, the number of coating layers is selected as 3.

[0056] Example 2

[0057] In this embodiment, the electric field distribution on the surface of the insulator is simulated and compared by changing the thickness of the coating layer. The number of coating layers is 3, the SiC ratios are 15%, 12.5%, and 10%, and the heights of the coating layers are uniformly distributed.

[0058] The thickness of the coating layer is 0.1mm, 0.5mm and 1mm respectively. Figure 3 As shown in Figure 2, the electric field distribution diagram of the insulator surface is obtained by simulation, and the specific parameters of the electric field on the surface of the insulator with coating layers of different thicknesses are shown in Table 2.

[0059] Table 2 Surface electric field parameters of insulators coated with different coating thicknesses

[0060]

[0061]

[0062] Reference Figure 3 Compared with Table 2, it is found that as the thickness of the coating increases, the maximum electric field intensity decreases slightly and the unevenness changes very little. Since the influence of the coating thickness is very small and combined with the actual process considerations, the final coating thickness is 0.5mm.

[0063] Example 3

[0064] In this embodiment, the electric field distribution on the surface of the insulator is simulated and compared by changing the height of the coating layer. The number of coating layers is 3, the SiC ratios are 15%, 12.5%, and 10%, and the thickness of the coating layers is 0.5 mm.

[0065] The heights of the above coating layers are uniformly distributed (5mm, 5mm, 5mm), non-uniformly distributed, such as Figure 4 As shown in Figure 3, the electric field distribution diagram of the insulator surface is obtained by simulation, and the specific parameters of the electric field on the surface of the insulator coated with different heights are shown in Table 3.

[0066] Table 3 Surface electric field parameters of insulators coated with different coating heights

[0067]

[0068] Reference Figure 4 As shown in Table 3, the comparison shows that the non-uniform distribution has a better modification effect than the uniform distribution. By adjusting the height of the three layers, the best modification effects are 1.1 mm, 2.8 mm, and 11.1 mm.

[0069] Example 4

[0070] In this example, DC surface flashover tests were conducted in an SF6 atmosphere on uncoated insulators and insulator samples with varying coating heights. During the experiment, chamfered electrodes were used, and the SF6 atmosphere pressure reached 0.1 MPa. A step-by-step pressurization method was used for the DC flashover test. The sample was pressurized starting at 5 kV and increasing in 2 kV steps until a stable flashover occurred. The flashover voltage was then recorded. Table 4 shows the measured DC surface flashover voltage in an SF6 atmosphere.

[0071] Table 4 Measurement results of DC surface flashover voltage of samples in SF6 atmosphere

[0072]

[0073] As can be seen from Table 4, coating the insulator surface with coating layers of different heights helps improve the DC surface flashover performance of the insulator in SF6 atmosphere. The flashover voltage of the uniformly modified and non-uniformly modified insulators is greatly improved compared with the unmodified insulators. The flashover performance of the non-uniformly modified specimens (the height of the coating layer is 1.1mm, 2.8mm, 11.1mm) is the best; the flashover voltage of the uniformly modified specimens (the height of the coating layer is 5mm, 5mm, 5mm) is higher than that of the unmodified specimens, but lower than that of the non-uniformly modified specimens. The Weibull distribution diagrams of the surface flashover voltage of the insulators under three different conditions are shown in Figure 4. Figure 7 shown.

[0074] from Figure 7 It can be seen that the surface flashover Weibull characteristic voltages are as follows from large to small: non-uniform modified sample (86.52kV), uniform modified sample (83.06kV), and unmodified sample (70.98kV). Compared with the unmodified insulator sample, the surface flashover voltage of the uniformly modified sample is increased by 17.01%, and the surface flashover voltage of the non-uniformly modified sample is increased by 21.89%.

[0075] Therefore, the method proposed in the present invention of using nonlinear material gradient coating on insulators and regulating coating layer parameters is simple and easy to implement, and can improve the DC surface flashover voltage of the insulator in SF6 atmosphere.

[0076] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0077] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for improving the nonlinear material gradient coating of insulator surface flashover, characterized in that: The coating method comprises the following steps: adding different mass fractions of nonlinear material SiC to epoxy resin to obtain a coating layer, adding the coating layer to the surface of the insulator, and inverting the surface trap energy level and density of the insulator by measuring the surface conductivity and surface potential decay of the coating layer; The coating method comprises the following steps: S1. Establish a basin insulator model based on Comsol, add the coating layer to the insulator surface, and simulate to obtain the electric field distribution on the insulator surface; S2. Changing the number of coating layers on the surface of the insulator, simulating the electric field distribution on the surface of the insulator using the basin-type insulator model, summarizing the variation pattern of the electric field on the surface of the insulator with the number of coating layers, and determining the number of coating layers; S3, changing the thickness of the coating layer on the surface of the insulator, simulating the electric field distribution on the surface of the insulator through the basin insulator model, summarizing the variation pattern of the electric field on the surface of the insulator with the thickness of the coating layer, and determining the thickness of the coating layer; S4, changing the height of the coating layer on the insulator surface, simulating the electric field distribution on the insulator surface through the basin insulator model, summarizing the variation pattern of the electric field on the insulator surface with the height of the coating layer, and determining the height of the coating layer; S5. According to the determined number of layers, thickness and height of the coating layer on the surface of the insulator, obtain the nonlinear material gradient coating method for improving the surface flashover of the insulator.

2. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 1, characterized in that: In step S1, the coating layer is a composite insulating material, and the mass fractions of the nonlinear material SiC are 5%, 7.5%, 10%, 12.5%, and 15% respectively.

3. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 2, characterized in that: In step S1 , the type of the insulator is a pot-type insulator, the height of the insulator is 15 mm, the upper surface radius of the insulator is 15 mm, and the lower surface radius of the insulator is 30 mm.

4. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 1, characterized in that: In step S2, the number of layers of the coating layer on the surface of the insulator is 1 layer, 3 layers, and 5 layers respectively.

5. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 4, characterized in that: In step S2, the number of layers of the coating layer is 1, and the mass fraction of the nonlinear material SiC is 15%; the number of layers of the coating layer is 3, and the mass fractions of the nonlinear material SiC are 15%, 12.5%, and 10%; the number of layers of the coating layer is 5, and the mass fractions of the nonlinear material SiC are 15%, 12.5%, 10%, 7.5%, and 5%; wherein the thickness of each coating layer is 0.5 mm, and the height of the coating layer is uniformly distributed.

6. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 1, characterized in that: In step S3, the thickness of the coating layer on the surface of the insulator is 0.1 mm, 0.5 mm, and 1 mm respectively.

7. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 6, characterized in that: In step S3, the number of layers of the coating layer on the surface of the insulator is 3, corresponding to the mass fractions of the nonlinear material SiC of 15%, 12.5%, and 10%, and the height of the coating layer is uniformly distributed.

8. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 1, characterized in that: In step S4, the coating layer is uniformly distributed or non-uniformly distributed at the height of the surface of the insulator.

9. The method for nonlinear material gradient coating for improving surface flashover of insulators according to claim 8, characterized in that: In step S4, the number of coating layers on the surface of the insulator is 3, corresponding to the mass fractions of the nonlinear material SiC being 15%, 12.5%, and 10%, and the thickness of the coating layers is 0.5 mm.

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