A nano - coating method for improving the anti - aging performance of plant insulating oil

Abstract

The present invention relates to a nano - coating method for improving the anti - aging performance of plant insulating oil, specifically as follows: S1: Place the insulating paper in a vapor deposition device, and deposit a layer of poly(ethylene terephthalate) film (PBT film) on the surface of the insulating paper by using vapor deposition technology; S2: Then, use the plasma bombardment treatment technology to treat the poly(ethylene terephthalate) film. The treatment time is 10 - 30 min, the gas is nitrogen or argon or oxygen, the pressure is 0.1 - 1.5 Pa, and the treatment power is 100 - 1000 W to obtain the surface - modified insulating paper; S3: Use the surface - modified insulating paper to prepare an oil - paper insulation system. By depositing a layer of PBT film on the surface of the insulating paper by using vapor deposition technology and performing plasma bombardment treatment, the adhesion between the PBT film and the insulating paper is enhanced, and at the same time, the dielectric properties and anti - aging ability of the insulating oil are improved, thereby enhancing the stability of the oil - paper insulation system.

Description

Technical Field

[0001] The present invention relates to the technical field of organic composite insulating materials, and particularly to a nano - coating method for improving the anti - aging performance of vegetable insulating oil. Background Art

[0002] At present, with the rapid development of the power industry, the requirements for the safety and stability of power equipment are getting higher and higher. Insulating oil and insulating paper, as indispensable components in power equipment, their performance directly affects the reliability and service life of the equipment. Therefore, improving the performance of insulating oil and insulating paper has always been a research hotspot in the power industry.

[0003] Currently, the commonly used methods for improving the performance of insulating oil mainly include adding antioxidants, adding anti - aging agents, adding stabilizers, etc. Although these methods can improve the performance of insulating oil to a certain extent, since they cannot change the electric field distribution at the interface between insulating oil and insulating paper, the effect is limited. In addition, the recovery effect of these methods on aged insulating oil is also very limited. Therefore, developing a method that can improve the electric field distribution at the interface between insulating oil and insulating paper has become one of the current research hotspots.

[0004] In recent years, nanotechnology has been widely applied in the modification research of insulating materials for power equipment. Research shows that nanoparticles have a large specific surface area and interfacial activity, and can form an effective shielding layer at the interface, thereby improving the electric field distribution of the insulation system, and enhancing the dielectric properties and anti - aging ability. Researchers have tried to apply nanomaterials to the modification of insulating oil and insulating paper. Currently, it has been confirmed that adding nanomaterials to insulating oil can effectively improve its dielectric strength and anti - aging ability. However, due to the easy aggregation of nanoparticles after addition and the difficulty in achieving uniform dispersion, the addition amount is limited and the effect is limited. In addition, research shows that nanomaterials also have potential application prospects in the modification of insulating paper. Researchers have found that depositing a nano - coating on the surface of insulating paper can improve the electric field distribution at the interface between insulating paper and insulating oil, and enhance the dielectric strength and anti - aging ability. However, there is currently a lack of a simple, effective, and low - cost method to prepare a nano - coating with stable performance.

[0005] On the other hand, the traditional methods for improving the dielectric properties and anti - aging ability of insulating oil often have some deficiencies. For example, adding a large amount of antioxidant nano - additives may lead to a decrease in the physical properties of insulating oil, and at the same time increase the difficulty and cost of the process operation. In addition, some improved insulating oil coating technologies also face problems such as narrow application range and insufficient adhesion between the coating and the insulating oil.

[0006] Therefore, it is necessary to develop a nano - coating method to improve the anti - aging performance of vegetable insulating oil and solve the problem of weak adhesion between the insulating paper and the coating. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a nano - coating method for improving the anti - aging performance of vegetable insulating oil. A thin film is deposited on the surface of the insulating paper and the surface of the thin film is treated, thereby increasing the surface area and interfacial activity, improving the adhesion between the coating and the insulating oil, and improving the electric field distribution. It has important application value and social and economic benefits.

[0008] To solve the above problems, the technical solution of the present invention is as follows: The nano - coating method for improving the anti - aging performance of vegetable insulating oil specifically includes the following steps:

[0009] S1: Place the insulating paper in a vapor deposition device and deposit a layer of poly (ethylene terephthalate) film on the surface of the insulating paper by using vapor deposition technology;

[0010] S2: Then, use the plasma bombardment treatment technology to treat the poly (ethylene terephthalate) film. The treatment time is 10 - 30 min, the gas is nitrogen or argon or oxygen, the pressure is 0.1 - 1.5 Pa, and the treatment power is 100 - 1000 W to obtain the surface - modified insulating paper;

[0011] S3: Use the surface - modified insulating paper to prepare an oil - paper insulation system.

[0012] Adopting the above technical solution, a layer of polybutylene terephthalate film (referred to as PBT film) is deposited on the surface of the insulating paper by chemical vapor deposition technology, and plasma bombardment treatment is carried out. After the treatment, a certain surface nanostructure is formed on the PBT film, increasing the surface area and interfacial activity, improving the adhesion between the coating and the insulating oil, and improving the electric field distribution; thereby improving the dielectric properties and anti-aging ability of the insulating oil, and further enhancing the stability of the oil-paper insulation system. This method is simple and low-cost, and the prepared coating has good mechanical properties and chemical stability, and can be applied in a wide range of industrial fields, with important application value and social and economic benefits. Among them, the method of using plasma bombardment to treat the PBT film uses energetic particles to bombard the surface of the target material, and atoms and other particles in the target material are ejected through particle momentum transfer; this method has the advantages of good bonding force between the film and the substrate, high sputtering density, few pinholes, good controllability and repeatability of the film layer. Plasma bombardment can effectively remove organic substances and impurities on the surface of the PBT cellulose composite material and form oxygen-containing functional groups on it, thereby improving its hydrophilicity and polarity. At the same time, plasma bombardment can also increase the surface roughness and specific surface area of the PBT cellulose composite material, thereby enhancing the interaction between vegetable insulating oils. These changes are beneficial to improving the interfacial bonding strength and mechanical properties of the PBT cellulose composite material.

[0013] Preferably, the chemical vapor deposition technology in step S1 is chemical vapor deposition or physical vapor deposition or molecular beam epitaxy technology, and the thickness of the deposited polybutylene terephthalate film is 50-200 nm.

[0014] Preferably, when chemical vapor deposition technology is used in step S1, the vacuum degree is 0.1-10 Pa, the sublimation temperature is 220-240 °C, the cracking temperature is 320-340 °C, the deposition temperature is 60-80 °C, the deposition rate is 0.1-1 nm / s, and the deposition time is 10-60 min. The thickness of the prepared PBT film is 100-150 nm, the average particle size is 20-50 nm, the specific surface area is 10-30 m 2 / g, and the surface roughness is 10-30 nm. The adhesion between the PBT film coating and the insulating oil is 3-5 levels, the adhesion between the coating and the insulating paper is 4-6 levels, and the adhesion between the insulating oil and the insulating paper is 7-9 levels.

[0015] Preferably, in step S2, the power of the plasma bombardment treatment is 800 W, the treatment time is 20 min, the gas is nitrogen, and the pressure is 1.0 Pa.

[0016] Preferably, in step S2, the polybutylene terephthalate film is treated by plasma bombardment (PECVD) technology, the ion beam energy is 200-500 eV, and the flux of the ion beam is 1-5 mA / cm2 , the processing time is 10 to 60 minutes.

[0017] Preferably, when the chemical vapor deposition technology is adopted in the step S1, the vacuum degree of the deposition device is 1 Pa, the vapor deposition temperature is 70 °C, the deposition rate is 0.5 nm / s, the deposition time is 30 minutes, and the thickness of the deposited poly (ethylene terephthalate) film is 100 nm.

[0018] Preferably, when the plasma bombardment PECVD technology is adopted in the step S2, the treatment is carried out in an oxygen atmosphere, the ion beam energy is 300 eV, the ion beam flux is 3 mA / cm 2 , the plasma bombardment time is 20 to 30 minutes, the air pressure is 0.1 Pa, and the power is 100 W.

[0019] Preferably, the oil-paper insulation system in the step S3 is an insulating paper modified by a poly (ethylene terephthalate) film (PBT film) and soaked in insulating oil to form an oil-paper composite material. The specific steps are as follows:

[0020] S31: Mix the insulating paper modified by the PBT film and vegetable insulating oil (transformer oil under pressure regulation) in a volume ratio of 1:2 and place them for 24 hours to form an oil-paper composite material; the system composed of the insulating paper modified by the PBT film and vegetable insulating oil is the experimental group; the system composed of the insulating paper not modified by the PBT film and vegetable insulating oil is used as the blank group; they are prepared by the same method;

[0021] S32: Place the prepared sample in an aging oven and age it at a temperature of 130 °C for 80 days; after aging, test the moisture in the oil, the moisture in the paper, the acid value of the oil, the breakdown voltage of the oil, and the dielectric loss of the oil. After the PBT film coating treatment, the dielectric constant of the insulating oil is increased to 2.5 to 3.0, the breakdown voltage is increased to 75 to 85 kV, and the anti-aging performance of the insulating oil is increased to more than twice the original. The application scope of the oil-paper insulation system formed by the insulating paper modified by the PBT film and vegetable insulating oil includes the insulation systems of high-voltage equipment such as power transformers, reactors, and circuit breakers, as well as the insulation and filling oil of power cables.

[0022] Preferably, the material of the insulating paper is polystyrene board paper or Dioscorea cirrhosa paper, and the thickness is 0.1 to 0.5 mm; the insulating oil is vegetable insulating oil of grade A or above, its specific capacitance is 50 to 60 pF / m, the dielectric strength is 50 to 60 kV / mm, and the breakdown voltage is 60 to 70 kV.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: A layer of PBT film is deposited on the surface of the insulating paper by using the vapor deposition technology and then subjected to plasma bombardment treatment, which enhances the adhesion between the PBT film and the insulating paper. At the same time, the dielectric performance and anti-aging ability of the insulating oil are improved, thereby enhancing the stability of the oil-paper insulation system. This method is simple and low in cost. The prepared coating has good mechanical properties and chemical stability and can be applied in a wide range of industrial fields. At the same time, the coating can effectively improve the dielectric performance and anti-aging ability of the insulating oil, thus improving the stability of the oil-paper insulation system, extending the service life of power equipment, reducing the occurrence of power accidents, and having important application value and social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the surface morphology diagram of the insulating paper modified with PBT film in the nano-coating method for improving the anti-aging performance of vegetable insulating oil; Figure 1 (a)- Figure 1 (b) is the surface morphology diagram of the composite insulating paper modified with PBT film without plasma bombardment treatment, where Figure 1 (b) is Figure 1 a partial enlarged view of (a);

[0025] Figure 1 (c)- Figure 1 (d) is the SEM diagram of the insulating paper modified with PBT film prepared by the plasma bombardment treatment method in the nano-coating method for improving the anti-aging performance of vegetable insulating oil of the present invention; where Figure 1 (c) is Figure 1 a partial enlarged view of (d);

[0026] Figure 2 is the diagram of the change law of water content in oil during the accelerated thermal aging process of the insulating paper modified with PBT film and the insulating paper not modified with PBT film in the nano-coating method for improving the anti-aging performance of vegetable insulating oil of the present invention;

[0027] Figure 3 is the diagram of the change law of water content in oil-impregnated paper during the accelerated thermal aging process of the insulating paper modified with PBT film and the insulating paper not modified with PBT film in the nano-coating method for improving the anti-aging performance of vegetable insulating oil of the present invention;

[0028] Figure 4 is the diagram of the change law of acid value of insulating oil during the accelerated thermal aging process of the insulating paper modified with PBT film and the insulating paper not modified with PBT film in the nano-coating method for improving the anti-aging performance of vegetable insulating oil of the present invention;

[0029] Figure 5It is a graph showing the variation law of the dielectric loss of insulating oil during the accelerated thermal aging process of the insulating paper modified with PBT film prepared by the nano - coating method for improving the anti - aging performance of vegetable insulating oil of the present invention and the insulating paper without PBT film modification;

[0030] Figure 6 It is a graph showing the variation law of the breakdown voltage of insulating oil during the accelerated thermal aging process of the insulating paper modified with PBT film prepared by the nano - coating method for improving the anti - aging performance of vegetable insulating oil of the present invention and the insulating paper without PBT film modification. Specific embodiments

[0031] To deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with the drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0032] Embodiment: The nano - coating method for improving the anti - aging performance of vegetable insulating oil specifically includes the following steps:

[0033] S1: Place the insulating paper in a vapor deposition device, and deposit a layer of polybutylene terephthalate film (PBT film) on the surface of the insulating paper by vapor deposition technology;

[0034] The vapor deposition technology in step S1 is chemical vapor deposition or physical vapor deposition or molecular beam epitaxy technology, and the thickness of the deposited polybutylene terephthalate film is 50 - 200 nm;

[0035] When using chemical vapor deposition technology in step S1, the vacuum degree is 0.1 - 10 Pa, the sublimation temperature is 220 - 240 °C, the cracking temperature is 320 - 340 °C, the deposition temperature is 60 - 80 °C, the deposition rate is 0.1 - 1 nm / s, and the deposition time is 10 - 60 min. The thickness of the prepared PBT film is 100 nm, the average particle size is 20 nm, the specific surface area is 10 m 2 / g, and the surface roughness is 10 nm. The adhesion between the PBT film coating and the insulating oil is 3 levels, the adhesion between the coating and the insulating paper is 6 levels, and the adhesion between the insulating oil and the insulating paper is 9 levels;

[0036] When using chemical vapor deposition technology in step S1, the vacuum degree of the deposition device is 1 Pa, the vapor deposition temperature is 70 °C, the deposition rate is 0.5 nm / s, the deposition time is 30 min, and the thickness of the deposited polybutylene terephthalate film is 100 nm;

[0037] S2: Then, use the plasma bombardment treatment technology to treat the poly(ethylene terephthalate) film. The treatment time is 10 - 30 min, the gas is nitrogen, the pressure is 0.1 - 1.5 Pa, and the treatment power is 100 - 1000 W to obtain the surface-modified insulating paper;

[0038] In step S2, the power of the plasma bombardment treatment is 800 W, the treatment time is 20 min, the gas is nitrogen, and the pressure is 1.0 Pa;

[0039] In step S2, use the plasma bombardment (PECVD) technology to treat the poly(ethylene terephthalate) film. The ion beam energy is 200 - 500 eV, and the ion beam flux is 1 - 5 mA / cm 2 , and the treatment time is 10 - 60 min.

[0040] When using the plasma bombardment PECVD technology in step S2, the treatment is carried out in an oxygen atmosphere. The ion beam energy is 300 eV, the ion beam flux is 3 mA / cm 2 , the plasma bombardment time is 20 - 30 min, the air pressure is 0.1 Pa, and the power is 100 W;

[0041] S3: Use the surface-modified insulating paper to prepare an oil-paper insulation system;

[0042] The oil-paper insulation system in step S3 is the insulating paper modified by the PBT film soaked in insulating oil to form an oil-paper composite material. The specific steps are as follows:

[0043] S31: Mix the insulating paper modified by the PBT film and vegetable insulating oil (transformer oil under pressure regulation) in a volume ratio of 1:2 and place it for 24 hours to form an oil-paper composite material; the system composed of the insulating paper modified by the PBT film and vegetable insulating oil is the experimental group; the system composed of the insulating paper not modified by the PBT film and vegetable insulating oil is used as the blank group and is prepared by the same method;

[0044] S32: Place the prepared sample in an aging oven and age it at a temperature of 130 °C for 80 days; after aging, test the moisture in the oil, the moisture in the paper, the acid value of the oil, the breakdown voltage of the oil, and the dielectric loss of the oil. After the PBT film coating treatment, the dielectric constant of the insulating oil is increased to 2.5 - 3.0, the breakdown voltage is increased to 75 - 85 kV, and the anti-aging performance of the insulating oil is increased to more than 2 times the original;

[0045] The material of the insulating paper is polystyrene board paper or Dioscorea cirrhosa paper, and the thickness is 0.1 - 0.5 mm; the insulating oil is vegetable insulating oil of grade A or above, with a specific capacitance of 50 - 60 pF / m, a dielectric strength of 50 - 60 kV / mm, and a breakdown voltage of 60 - 70 kV.

[0046] The following is a detailed description through two specific embodiments.

[0047] Specific Embodiment 1: The method of the nano - coating for improving the anti - aging performance of plant insulating oil specifically includes the following steps:

[0048] S1: Place the insulating paper in a vapor deposition device, and deposit a layer of poly(ethylene terephthalate) film (PBT film) on the surface of the insulating paper by using vapor deposition technology; the material of the insulating paper is electrical insulating paper with a thickness of 0.15 mm.

[0049] When using chemical vapor deposition technology in step S1, the PBT monomer used during deposition is the condensate of dimethyl terephthalate and hydroquinone, with formic acid as the catalyst. It is carried out under the conditions of a vacuum degree of 1 Pa, a sublimation temperature of 250 °C, a cracking temperature of 330 °C, a deposition temperature of 80 °C, a deposition rate of 0.2 nm / s, and a time of 8 min. The deposition time is 8 min, and the thickness of the deposited poly(ethylene terephthalate) film is 100 nm; the average particle size is 20 nm, the specific surface area is 10 m 2 / g, the surface roughness is 10 nm; the adhesion between the PBT film coating and the insulating oil is grade 3, the adhesion between the coating and the insulating paper is grade 6, and the adhesion between the insulating oil and the insulating paper is grade 9.

[0050] S2: Then, use the plasma bombardment treatment technology to treat the poly(ethylene terephthalate) film. The specific parameters are as follows: Use a plasma surface treatment device with a negative ion source to treat the surface of the PBT film in an oxygen or nitrogen environment. The treatment parameters are as follows: The gas flow rate is 20 SCCM, the discharge power is 100 W, the treatment time is 5 minutes, the room temperature is 25 °C, and the pressure is 50 Pa; obtain the surface - modified insulating paper, as Figure 1 shown in its SEM image, as can be seen from Figure 1 (c) - 1(d); the surface of the insulating paper with the PBT film treated by the plasma bombardment treatment technology shows micro - and nano - level roughness, which increases the surface area and improves the adhesion of the coating liquid; at the same time, the deposition of the PBT film on the surface of the insulating paper forms a needle - like structure, and these structures improve the insulation performance by increasing the surface charge density.

[0051] S3: Use the surface - modified insulating paper to prepare an oil - paper insulation system.

[0052] The oil - paper insulation system in step S3 is the insulating paper modified by the PBT film soaked in insulating oil to form an oil - paper composite material. The specific steps are as follows:

[0053] S31: Mix the insulating paper modified by PBT film with vegetable insulating oil (transformer oil under pressure regulation) at a volume ratio of 1:2 and leave it for 24 hours to form an oil-paper composite material; the system composed of the insulating paper modified by PBT film and vegetable insulating oil is the experimental group;

[0054] S32: Place the prepared sample in an aging oven and age it at a temperature of 130 °C for 80 days; after aging, measure the water content in the oil, the water content in the paper, the acid value of the oil, the breakdown voltage of the oil, and the dielectric loss of the oil.

[0055] Comparative Example 1 (blank group):

[0056] This Comparative Example 1 provides a system composed of insulating paper without PBT film modification and vegetable insulating oil as the blank group; mix the insulating paper without PBT film modification with vegetable insulating oil (transformer oil under pressure regulation) at a volume ratio of 1:2 and leave it for 24 hours to form an oil-paper composite material; the system composed of the insulating paper modified by PBT film and vegetable insulating oil is the experimental group;

[0057] S32: Place the prepared sample in an aging oven and age it at a temperature of 130 °C for 80 days; after aging, measure the water content in the oil, the water content in the paper, the acid value of the oil, the breakdown voltage of the oil, and the dielectric loss of the oil.

[0058] Figures 2 to 6 These are all comparison graphs of the aging test results of the insulating paper and vegetable insulating oil systems before and after the treatment of the present invention, including the following parameters:

[0059] As Figure 2 shown, water content in the oil: The water content in the insulating paper and vegetable insulating oil system after being treated by the present invention is lower than that of the blank group during the aging process;

[0060] As Figure 3 shown, water content in the paper: The water content in the insulating paper after being treated by the present invention is lower than that of the blank group during the aging process;

[0061] As Figure 4 shown, acid value of the oil: The acid value in the vegetable insulating oil system after being treated by the present invention is lower than that of the blank group during the aging process;

[0062] As Figure 5 shown, dielectric loss of the oil: The dielectric loss in the vegetable insulating oil system after being treated by the present invention is lower than that of the blank group during the aging process;

[0063] As Figure 6 shown, breakdown voltage of the oil: The breakdown voltage in the vegetable insulating oil system after being treated by the present invention is higher than that of the blank group during the aging process.

[0064] By comparing the changes in parameters such as moisture in oil, moisture in paper, acid value of oil, breakdown voltage of oil, and dielectric loss of oil before and after aging between the experimental group and the blank group, the effects of the present invention are evaluated; the results show that for the system composed of the treated insulating paper and vegetable insulating oil, compared with the blank group, the increasing trends of moisture in oil, moisture in paper, acid value of oil, and dielectric loss of oil before and after aging are all reduced, while the decreasing trend of breakdown voltage is slowed down, indicating that the nano-coating preparation method described in the present invention can effectively improve the stability of the oil-paper insulation system and has good application prospects.

[0065] For those of ordinary skill in the art, the specific embodiments only exemplarily describe the present invention. Obviously, the specific implementation of the present invention is not limited by the above-mentioned manner. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present invention, for example, changes in parameters of plasma bombardment treatment technology, deposition time, deposited thickness, etc., or directly applying the concept and technical solution of the present invention to other occasions without improvement, all fall within the protection scope of the present invention.

Claims

1. A nano - coating method for improving the anti - aging performance of plant insulating oil, characterized in that, it specifically includes the following steps: S1: Place the insulating paper in a vapor deposition device, and deposit a layer of polyterephthalate film on the surface of the insulating paper by using vapor deposition technology; S2: Then, use the plasma bombardment treatment technology to treat the polyterephthalate film. The treatment time is 10 - 30 min, the gas is nitrogen or argon or oxygen, the pressure is 0.1 - 1.5 Pa, and the treatment power is 100 - 1000 W to obtain surface - modified insulating paper; S3: Use the surface - modified insulating paper to prepare an oil - paper insulation system; The vapor deposition technology in step S1 is chemical vapor deposition, and the thickness of the deposited polyterephthalate film is 50 - 200 nm; when using chemical vapor deposition technology in step S1, the vacuum degree is 0.1 - 10 Pa, the sublimation temperature is 220 - 240 °C, the cracking temperature is 320 - 340 °C, the deposition temperature is 60 - 80 °C, the deposition rate is 0.1 - 1 nm / s, and the deposition time is 10 - 60 min; In step S2, the power of the plasma bombardment treatment is 800 W, the treatment time is 20 min, the gas is nitrogen, and the pressure is 1.0 Pa; When using the plasma bombardment technology in step S2, the specific parameters are as follows: Use a plasma surface treatment device with a negative ion source to treat the surface of the PBT film in an oxygen or nitrogen environment. The treatment parameters are as follows: The gas flow rate is 20 SCCM, the discharge power is 100 W, the treatment time is 5 minutes, the room temperature is 25 °C, the pressure is 50 Pa. After treatment, the surface of the PBT film shows micro - nano - scale roughness and needle - like structures, and at the same time, the surface charge density increases, improving the insulation performance and coating adhesion, thus reducing the water adsorption.

2. The nano - coating method for improving the anti - aging performance of plant insulating oil according to claim 1, characterized in that, When using chemical vapor deposition technology in step S1, the vacuum degree of the deposition device is 1 Pa, the vapor deposition temperature is 70 °C, the deposition rate is 0.5 nm / s, the deposition time is 30 min, and the thickness of the deposited polyterephthalate film is 100 nm.

3. The nano - coating method for improving the anti - aging performance of plant insulating oil according to claim 1, characterized in that, In the step S2, when the plasma bombardment PECVD technology is adopted, the treatment is carried out in an oxygen atmosphere, the ion beam energy is 300 eV, and the ion beam flux is 3 mA / cm 2 , the plasma bombardment time is 20 - 30 min, the air pressure is 0.1 Pa, and the power is 100 W.

4. The nano - coating method for improving the anti - aging performance of plant insulating oil according to claim 1, characterized in that, The oil - paper insulation system in step S3 is that the insulating paper modified by the polyterephthalate film is soaked in insulating oil to form an oil - paper composite material. The specific steps are as follows: S31: Mix the insulating paper modified by the PBT film and plant insulating oil in a volume ratio of 1:2 and place for 24 h to form an oil - paper composite material; S32: Place the prepared sample in an aging oven and age at a temperature of 130 °C for 80 days; After aging, test the water content in the oil, the water content in the paper, the acid value of the oil, the breakdown voltage of the oil, and the dielectric loss of the oil.

5. The nano - coating method for improving the anti - aging performance of plant insulating oil according to claim 4, It is characterized in that the material of the insulating paper is polystyrene board paper or Dioscorea cirrhosa paper, and the thickness is 0.1-0.5 mm; the insulating oil is a plant insulating oil of Class A or above, with a specific capacitance of 50-60 pF / m, a dielectric strength of 50-60 kV / mm, and a breakdown voltage of 60-70 kV.

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