Preparation method for improving flashover performance under atmosphere of 25% SF6 / 75% N2 by coating epoxy composite material on surface of nano Ag

Abstract

The invention discloses a preparation method for improving flashover performance under 25% SF6 / 75% N2 atmosphere by coating an epoxy composite material on the surface of nano Ag, and belongs to the technical field of high-voltage insulating materials. The preparation method comprises the following steps: 1) drying nano Al2O3 and Ag particles at high temperature; 2) preparing an epoxy resin solution, and dividing the solution into two batches for later use; 3) adding Al2O3 into a batch of epoxy resin solution in batches, heating and uniformly stirring, and vacuumizing for later use; 4) adding Ag particles into the epoxy resin solution in batches, heating and uniformly stirring; 5) vacuumizing and defoaming the solution, and heating the solution to a semi-crosslinking state in a vacuum environment; 6) uniformly coating the semi-crosslinked EP / Ag on the surface of the inner side of the insulator mold and heating the semi-crosslinked EP / Ag; and 7) heating the prepared insulator matrix solution, pouring into an insulator mold, and carrying out stepped high-temperature curing. According to the preparation method of the material for inhibiting the surface charge accumulation of the insulator, the surface charge accumulation of the insulator can be obviously improved, and an effective way is provided for inhibiting the surface charge accumulation of the insulator under high field intensity.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-voltage insulating materials, and in particular is a preparation method for nano-Ag surface-coated epoxy composite material to improve flashover performance in a 25% SF6 / 75% N2 atmosphere. Background Art

[0002] As the core insulating component of ultra-high voltage (UHV) gas-insulated metal-enclosed switchgear (GIS), surface flashover caused by surface charge accumulation has become a key factor affecting power system reliability. As voltage levels increase, electric field distortion on the insulator surface intensifies, and charge accumulation becomes more pronounced. Conventional material systems are no longer able to meet the insulation requirements of UHV equipment. In this context, surface functionalization modification technology, due to its flexible operation and significant effectiveness, has become an important research direction for improving the surface electrical resistance of insulators.

[0003] In recent years, metal filler-doped polymer composites have shown great potential in suppressing surface charge accumulation due to their unique conductive properties. Among them, the epoxy resin / silver (Ag) doping system has attracted much attention due to its excellent controllability and stability. Silver nanoparticles (Ag NPs) have high electrical conductivity. When they are uniformly dispersed in the epoxy resin matrix, they can form a conductive network, significantly improving the charge dissipation capacity of the material. Studies have shown that by regulating the content and particle size of the Ag filler, the conductivity of the basin insulator can be adjusted, so that while maintaining good insulation performance, it promotes the dynamic dissipation of surface charge, thereby effectively suppressing local electric field distortion. Therefore, this technical solution proposes a method for preparing an insulator based on epoxy-doped Ag. Summary of the Invention

[0004] The present invention provides a preparation method for improving the flashover performance of nano-Ag surface-coated epoxy composite materials in a 25% SF6 / 75% N2 atmosphere. The method can improve the charge transport characteristics of basin-type insulators, reduce the accumulation of surface charge on the insulator, increase the surface charge dissipation rate, and increase the surface flashover voltage. The improvement effect is significant and the practicability is strong.

[0005] To achieve the above objectives, this paper provides a preparation method for nano-Ag surface-coated epoxy composite material to improve the flashover performance in a 25% SF6 / 75% N2 atmosphere, which specifically includes the following steps:

[0006] S1 dries Al2O3 and Ag particles at high temperature;

[0007] S2: epoxy resin, methyltetrahydrophthalic anhydride, and 2,4,6-tris(dimethyl)phenol are mixed, heated and stirred in a vacuum environment, and the mixture is divided into two batches and placed in a beaker for later use;

[0008] S3 adds the Al2O3 particles in S1 to the mixed solution of S2 in batches, heats and stirs evenly, and then places it in a vacuum dryer to evacuate for later use;

[0009] S4 adds the Ag particles in S1 to the solution in S2 in batches and heats and stirs the resulting solution evenly;

[0010] S5: placing the solution obtained in S4 in a vacuum desiccator for vacuum degassing, and heating to a semi-crosslinked state after the degassing is completed;

[0011] S6: evenly coating the solution obtained in S5 on the inner side of the insulator mold and heating it to a semi-solidified state;

[0012] S7 heats the solution obtained in S3 and pours it into the mold in S6, and performs stage high temperature curing.

[0013] Furthermore, in step S1, the Al2O3 particles are nano-α-alumina with a diameter of 30-40 nm; the Ag particles are nano-silver with a diameter of 15-25 nm, the drying temperature is 80±5°C, and the heating time is 4±0.5 h.

[0014] Furthermore, in step S2, the epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol = 100:80:1, the heating temperature is 75±5° C., and the stirring time is 40±5 min.

[0015] Furthermore, in step S3, the heating temperature is 75±5° C., the stirring speed is 700±50 r / min, the stirring time is 50±10 min, and the vacuum placement time is 120±10 min.

[0016] Furthermore, in step S3, the mass of the Al2O3 particles accounts for 35% of the total mass of the total solution and the particles.

[0017] Furthermore, in step S4, the heating temperature is 75±5° C., the stirring speed is 400±50 r / min, and the stirring time is 40±5 min.

[0018] Furthermore, in step S4, the mass of the Ag particles accounts for 0.5% of the total mass of the total solution and the particle concentration.

[0019] Furthermore, in step S5, the degassing time is 120±10 min, the heating temperature is 85±5° C., and the heating time is 40±5 min.

[0020] Furthermore, in step S6, the heating temperature is 90±5° C. and the heating time is 15±5 min.

[0021] Furthermore, in step S7, the step high temperature curing is performed, with the first stage heating temperature being 80±5°C and the heating time being 2±0.5h; and the second stage heating temperature being 120±5°C and the heating time being 8±0.5h.

[0022] The beneficial effects of the present invention are:

[0023] The present invention can effectively improve electrical conductivity, significantly enhancing bulk conductivity; it increases the dissipation rate of surface charge, reduces the accumulation of surface charge on the insulator, and provides an effective way to improve the surface charge transport properties of insulating materials; the process used is low in difficulty, has obvious effects, is highly operable, and has low operational difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are the surface conductivity curves of insulators processed in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention.

[0025] Figure 2 These are surface charge density diagrams of insulators processed in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention.

[0026] Figure 3 This is a graph showing the surface potential attenuation curves of insulators processed in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention.

[0027] Figure 4 These are test diagrams of surface flashover voltage of insulators processed by Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present application clearer and more complete, the technical solutions in the embodiments of the present invention are clearly and completely described through the following drawings, examples and comparative examples. The following detailed descriptions are all descriptions of the embodiments, which are intended to provide further detailed descriptions of the present invention. The following detailed descriptions of the embodiments of the present invention provided in the accompanying drawings are not intended to limit the scope of the invention claimed for protection, but merely represent selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those commonly understood by ordinary technicians in the field to which this application belongs.

[0029] Example 1 is the middle value, Example 2 is the lower limit, Example 3 is the upper limit, Comparative Example 1 is an undoped Ag epoxy resin insulator, Comparative Example 2 is an insulator with a coating concentration of 0.3% Ag, and Comparative Example 3 is an insulator with a coating concentration of 1% Ag.

[0030] The reagents and materials used in the present invention are as follows:

[0031] The epoxy resin is Phoenix brand E-51 epoxy resin produced by Nantong Xingchen Synthetic Materials Co., Ltd.

[0032] The curing agent used is liquid methyltetrahydrophthalic anhydride from Changzhou Runxiang Chemical Plant.

[0033] The accelerator used was 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) produced by Zhangjiagang Yuanbang Chemical Plant.

[0034] Nano-Ag particles were produced by Beijing Dekedao Gold Company, model DK101-1, with a purity of 99.95% and a particle size of 20±5 nm.

[0035] The Al2O3 particles were produced by Beijing Dekedaojin Company, model DK-Al2O3-A350, with a purity of 99.99% and a particle size of 35±5 μm.

[0036] The insulator mold material is 304 stainless steel. The prepared insulator has an upper bottom radius of 17 mm, a lower bottom radius of 34 mm, a height of 17 mm, and an angle of 45°.

[0037] The following detailed descriptions are all descriptions of embodiments and are intended to provide further detailed descriptions of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which this application belongs.

[0038] Example 1

[0039] This embodiment provides a preparation method for improving the flashover performance of a nano-Ag surface-coated epoxy composite material in a 25% SF6 / 75% N2 atmosphere, comprising the following steps:

[0040] 1) Dry the nano-Al2O3 and nano-Ag particles at 80°C for 4 h to remove surface adsorbed water;

[0041] 2) Pour epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol into a three-necked flask in a mass ratio of 100:80:1, mix, evacuate and stir at 75°C for 40 minutes, and pour into beakers in two batches for later use;

[0042] 3) Al2O3 particles from step 1 were added in batches to a portion of the solution from step 2, with the Al2O3 particles accounting for 35% of the total solution and particle concentration. The mixture was stirred at 75°C and 700 rpm for 50 minutes, and then placed in a vacuum desiccator under vacuum for 120 minutes.

[0043] 4) Add the Ag particles from step 1 to another portion of the solution from step 2 in batches, with the Ag particles accounting for 0.5% of the total solution and particle concentration, and stir at 75°C and 400 rpm for 40 minutes;

[0044] 5) placing the solution obtained in step 4) in a vacuum desiccator and degassing for 120 minutes, followed by heating at 85° C. for 40 minutes until the solution reaches a semi-crosslinked state;

[0045] 6) The solution obtained in step 5) is evenly coated on the inner side of the insulator mold, and placed in an oven and heated at 90° C. for 15 minutes until it is semi-solidified;

[0046] 7) The Al2O3 / epoxy solution obtained in step 3) was heated and poured into a mold, which was then placed in an oven and cured in two stages: the first stage was cured at 80°C for 2 hours, and the second stage was cured at 120°C for 8 hours.

[0047] Example 2

[0048] This embodiment provides a preparation method for improving the flashover performance of a nano-Ag surface-coated epoxy composite material in a 25% SF6 / 75% N2 atmosphere, comprising the following steps:

[0049] 1) Dry the nano-Al2O3 and nano-Ag particles at 75°C for 3.5 hours to remove surface adsorbed water;

[0050] 2) Pour epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol into a three-necked flask in a mass ratio of 100:80:1, stir under vacuum at 70°C for 35 minutes, and pour into beakers in two batches for later use;

[0051] 3) Al2O3 particles from step 1 were added in batches to a portion of the solution from step 2, with the Al2O3 particles accounting for 35% of the total solution and particle concentration. The mixture was stirred at 70°C and 650 rpm for 40 minutes, and then placed in a vacuum desiccator under vacuum for 110 minutes.

[0052] 4) Add the Ag particles from step 1 to another portion of the solution from step 2 in batches, with the Ag particles accounting for 0.5% of the total solution and particle concentration, and stir at 70°C and 350 rpm for 35 minutes;

[0053] 5) placing the solution obtained in step 4) in a vacuum desiccator and degassing for 110 minutes, followed by heating at 80° C. for 35 minutes until the solution reaches a semi-crosslinked state;

[0054] 6) The solution obtained in step 5) is evenly coated on the inner side of the insulator mold, and placed in an oven and heated at 85° C. for 10 minutes until it is semi-solidified;

[0055] 7) The Al2O3 / epoxy solution obtained in step 3) was heated and poured into a mold, which was then placed in an oven and cured in two stages: the first stage was cured at 75°C for 1.5 hours, and the second stage was cured at 115°C for 7.5 hours.

[0056] Example 3

[0057] This embodiment provides a preparation method for improving the flashover performance of a nano-Ag surface-coated epoxy composite material in a 25% SF6 / 75% N2 atmosphere, comprising the following steps:

[0058] 1) Dry the nano-Al2O3 and nano-Ag particles at 85°C for 4.5 hours to remove surface adsorbed water;

[0059] 2) Pour epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol into a three-necked flask in a mass ratio of 100:80:1, stir under vacuum at 85°C for 45 minutes, and pour into beakers in two batches for later use;

[0060] 3) Al2O3 particles from step 1 were added in batches to a portion of the solution from step 2, with the Al2O3 particles accounting for 35% of the total solution and particle concentration. The mixture was stirred at 80°C and 750 rpm for 60 minutes, and then placed in a vacuum desiccator under vacuum for 130 minutes.

[0061] 4) Add the Ag particles from step 1 to another portion of the solution from step 2 in batches, with the Ag particles accounting for 0.5% of the total solution and particle concentration, and stir at 85°C and 450 rpm for 45 minutes;

[0062] 5) placing the solution obtained in step 4) in a vacuum desiccator and degassing for 130 minutes, followed by heating at 90° C. for 45 minutes until the solution reaches a semi-crosslinked state;

[0063] 6) The solution obtained in step 5) is evenly coated on the inner side of the insulator mold, and placed in an oven and heated at 95° C. for 20 minutes until it is semi-solidified;

[0064] 7) The Al2O3 / epoxy solution obtained in step 3) was heated and poured into a mold, which was then placed in an oven and cured in two stages: the first stage was cured at 85°C for 2.5 hours, and the second stage was cured at 125°C for 8.5 hours.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing an epoxy insulator without Ag surface coating, which specifically comprises the following steps:

[0067] 1) Dry the nano-Al2O3 particles at 80°C for 4 hours to remove surface adsorbed water;

[0068] 2) Pour epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol into a three-necked flask in a mass ratio of 100:80:1, mix, evacuate and stir at 75°C for 40 minutes, and pour into a beaker for later use;

[0069] 3) Al2O3 particles from step 1 were added to the solution from step 2 in batches, with the Al2O3 particles accounting for 35% of the total solution and particle concentration. The mixture was stirred at 75°C and 700 rpm for 50 minutes, and then placed in a vacuum desiccator under vacuum for 120 minutes.

[0070] 4) Heat the solution obtained in step 3) at 80°C for 5 min.

[0071] 5) The Al2O3 / epoxy solution obtained in step 4) was heated and poured into a mold, which was then placed in an oven and cured in two stages: the first stage was cured at 80°C for 2 hours, and the second stage was cured at 120°C for 8 hours.

[0072] Comparative Example 2

[0073] This comparative example provides a method for preparing a low-concentration nano-Ag surface coating for inhibiting charge accumulation on the surface of an epoxy composite material, which specifically comprises the following steps:

[0074] 1) Dry the nano-Al2O3 and nano-Ag particles at 80°C for 4 h to remove surface adsorbed water;

[0075] 2) Pour epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol into a three-necked flask in a mass ratio of 100:80:1, mix, evacuate and stir at 75°C for 40 minutes, and pour into beakers in two batches for later use;

[0076] 3) Al2O3 particles from step 1 were added in batches to a portion of the solution from step 2, with the Al2O3 particles accounting for 35% of the total solution and particle concentration. The mixture was stirred at 75°C and 700 rpm for 50 minutes, and then placed in a vacuum desiccator under vacuum for 120 minutes.

[0077] 4) Add the Ag particles from step 1 to another portion of the solution from step 2 in batches, with the Ag particles accounting for 0.5% of the total solution and particle concentration, and stir at 75°C and 400 rpm for 40 minutes;

[0078] 5) placing the solution obtained in step 4) in a vacuum desiccator and degassing for 120 minutes, followed by heating at 85° C. for 40 minutes until the solution reaches a semi-crosslinked state;

[0079] 6) The solution obtained in step 5) is evenly coated on the inner side of the insulator mold, and placed in an oven and heated at 90° C. for 15 minutes until it is semi-solidified;

[0080] 7) The Al2O3 / epoxy solution obtained in step 3) was heated and poured into a mold, which was then placed in an oven and cured in two stages: the first stage was cured at 80°C for 2 hours, and the second stage was cured at 120°C for 8 hours.

[0081] Comparative Example 3

[0082] This comparative example provides a method for preparing a high-concentration nano-Ag surface coating for inhibiting charge accumulation on the surface of an epoxy composite material, which specifically comprises the following steps:

[0083] 1) Dry the nano-Al2O3 and nano-Ag particles at 80°C for 4 h to remove surface adsorbed water;

[0084] 2) Pour epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol into a three-necked flask in a mass ratio of 100:80:1, mix, evacuate and stir at 75°C for 40 minutes, and pour into beakers in two batches for later use;

[0085] 3) Al2O3 particles from step 1 were added in batches to a portion of the solution from step 2, with the Al2O3 particles accounting for 35% of the total solution and particle concentration. The mixture was stirred at 75°C and 700 rpm for 50 minutes, and then placed in a vacuum desiccator under vacuum for 120 minutes.

[0086] 4) Add the Ag particles from step 1 to another portion of the solution from step 2 in batches, with the Ag particles accounting for 1% of the total solution and particle concentration, and stir at 75°C and 400 rpm for 40 minutes;

[0087] 5) placing the solution obtained in step 4) in a vacuum desiccator and degassing for 120 minutes, followed by heating at 85° C. for 40 minutes until the solution reaches a semi-crosslinked state;

[0088] 6) The solution obtained in step 5) is evenly coated on the inner side of the insulator mold, and placed in an oven and heated at 90° C. for 15 minutes until it is semi-solidified;

[0089] 7) The Al2O3 / epoxy solution obtained in step 3) was heated and poured into a mold, which was then placed in an oven and cured in two stages: the first stage was cured at 80°C for 2 hours, and the second stage was cured at 120°C for 8 hours.

[0090] Experimental testing (one)

[0092] The conductivity of epoxy composites was measured using a three-electrode configuration. A Keithley 6517B ammeter and an 8009 resistance box were used. Before the experiment, the upper and lower surfaces of the sample were short-circuited to eliminate residual surface charge. The applied voltage was 1 kV, and the experimental temperature was room temperature (25°C).

[0093] Depend on Figure 2 It can be seen that the surface conductivity of comparative example 3 is greater than that of embodiment 1, and the surface conductivity of comparative example 2 is greater than that of comparative example 1. Surface coating of the epoxy composite material with 0.5% nano-Ag improves the surface conductivity of the insulator. (two)

[0095] The surface charge test was performed on the insulators of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3. The test used a high-voltage DC power supply for charging at a charging voltage of -20 kV to measure the surface charge of the insulator samples. Figure 3 1 is a graph of surface charge density of insulators of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3.

[0096] Figure 1 The charge density is highest in Comparative Example 1, followed by Comparative Example 2, and lowest in Example 1. This shows that Ag particle surface coating can reduce the surface charge density of the insulator. When 0.5% by mass of Ag is used, the surface density of the insulator is further reduced, indicating that the preparation method of epoxy doping with Ag to improve the surface charge of the insulator proposed in this patent can inhibit surface charge accumulation. (three)

[0098] The surface potential decay curves of Comparative Example 1, Comparative Example 2, Comparative Example 3 and Example 1 were measured, and the surface potential decay curves of Comparative Example 2, Comparative Example 1 and Example 1 were tested using the surface potential decay method to analyze the effect of the epoxy composite coating on the surface charge transport characteristics. The test used a needle-gate electrode system to charge the surface of the insulating material, where the needle voltage was -8kV, the gate voltage was -4kV, and the charging time was 2min. Trek542A was used to record the decay curve of the surface potential of the insulating material over time, the test time was 20000s, and the sampling time was 1s. ( Figure 3 In order to show the potential decay curve, every 400 points are selected as a data point in the figure).

[0099] Figure 1 In Example 1, the charge decay rate was the fastest, followed by Comparative Example 2. After surface coating with 0.5% mass fraction of Ag, the surface potential was -1957 V at 20,000 s, while in Comparative Example 1, the surface potential of the uncoated insulator was approximately -2200 V. This indicates that surface coating with nano-Ag particles effectively improves surface charge dissipation and reduces surface charge accumulation, with the optimal effect achieved when using 0.5% mass fraction of Ag particles. (Four)

[0101] The DC surface flashover voltages of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were tested. The tests were conducted in a mixed atmosphere of 25% SF6 and 75% N2. Flat electrodes were used, and three specimens were tested per group. The test voltage ramp rate was 2 kV / s. The Weibull distribution was used to analyze the DC surface flashover voltage distribution of the insulators. Figure 4 This is a statistical diagram of the Weibull distribution of the DC surface flashover voltage of the insulator sample in a mixed atmosphere of 25% SF6 and 75% N2.

[0102] As can be seen from the figure, the use of 0.5% mass fraction Ag particle coating (Comparative Example 2) and 2% mass fraction Ag particle coating (Comparative Example 3) can both improve the surface flashover voltage of the insulator sample (compared with Comparative Example 1), and the use of 0.5% mass fraction Ag particle coating has a higher improvement in flashover voltage, which is higher than the surface flashover voltage of Comparative Examples 2 and 3. This shows that the nano-Ag surface coating preparation method for inhibiting surface charge accumulation of epoxy composite materials proposed in the patent of this invention can effectively improve the surface flashover voltage of insulator samples.

[0103] Therefore, the present invention provides a low-concentration nano-Ag surface coating preparation method for inhibiting surface charge accumulation of epoxy composite materials. It can reduce surface charge accumulation of insulators by synergistically inhibiting bulk charge transport and enhancing surface charge transport, thereby increasing the DC surface flashover voltage of the insulator. The technical method has stable effects, low processing difficulty and strong operability.

[0104] The foregoing description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by any person skilled in the art within the technical scope disclosed herein and within the spirit and principles of the present invention shall be covered by the scope of protection of the present invention. Furthermore, any matters not described in detail in this specification constitute prior art known to those skilled in the art.

[0105] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

Claims

1. A nano-Ag surface coated epoxy composite material increases SF by 25% σ / Preparation method of flashover performance under 75% N2 atmosphere, characterized in that, The following steps are involved: S1 dries Al2O3 and Ag particles at high temperature; S2: epoxy resin, methyltetrahydrophthalic anhydride, and 2,4,6-tris(dimethyl)phenol are mixed, heated and stirred in a vacuum environment, and the mixture is divided into two batches and placed in a beaker for later use; S3 adds the Al2O3 particles in S1 to the mixed solution of S2 in batches, heats and stirs evenly, and then places it in a vacuum dryer to evacuate for later use; S4 adds the Ag particles in S1 to the solution in S2 in batches and heats and stirs the resulting solution evenly; S5: placing the solution obtained in S4 in a vacuum desiccator for vacuum degassing, and heating to a semi-crosslinked state after the degassing is completed; S6: evenly coating the solution obtained in S5 on the inner side of the insulator mold and heating it to a semi-solidified state; S7 heats the solution obtained in S3 and pours it into the mold in S6, and performs stage high temperature curing.

2. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S1, the Al2O3 particles are nano-α-alumina with a diameter of 30-40 nm; the Ag particles are nano-silver with a diameter of 15-25 nm, the drying temperature is 80±5°C, and the heating time is 4±0.5 h.

3. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S2, the epoxy resin: methyltetrahydrophthalic anhydride: 2,4,6-tris(dimethyl)phenol = 100:80:1, the heating temperature is 75±5° C., and the stirring time is 40±5 min.

4. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S3, the heating temperature is 75±5° C., the stirring speed is 700±50 r / min, the stirring time is 50±10 min, and the vacuum placement time is 120±10 min.

5. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S3, the mass of the Al2O3 particles accounts for 35% of the total mass of the total solution and the particles.

6. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S4, the heating temperature is 75±5° C., the stirring speed is 400±50 r / min, and the stirring time is 40±5 min.

7. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S4, the mass of the Ag particles accounts for 0.5% of the total mass of the total solution and the particles.

8. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S5, the degassing time is 120±10 min, the heating temperature is 85±5° C., and the heating time is 40±5 min.

9. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S6, the heating temperature is 90±5° C. and the heating time is 15±5 min.

10. The method for preparing a nano-Ag surface-coated epoxy composite material for improving flashover performance in a 25% SF6 / 75% N2 atmosphere according to claim 1, characterized in that: In step S7, the step high temperature curing is carried out, with the first stage heating temperature being 80±5°C and the heating time being 2±0.5h; the second stage heating temperature being 120±5°C and the heating time being 8±0.5h.

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