Natural ester insulating oil resistant to gas generation and preparation method thereof

Abstract

The present invention discloses a natural ester insulating oil that resists gas generation and a preparation method thereof. The natural ester insulating oil comprises 96 to 98.2 parts of refined vegetable oil and 1 to 4 parts of additives in parts by mass. The additives include antioxidants and anti-gas generation agents, and the anti-gas generation agent is obtained by mixing salicylates and their derivatives with n-octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate. The natural ester insulating oil prepared by the present invention has strong antioxidant properties and can reduce the production of characteristic gases, wherein the production of hydrogen and ethane is significantly reduced, and compared with the natural ester insulating oil to which the anti-gas generation agent is not added, the reduction is 74.92% and 85.31% respectively, and the natural ester insulating oil prepared by the present invention maintains excellent high temperature performance and green environmental protection performance. The present invention provides a method for improving the antioxidant properties of natural ester insulating oil and reducing the production of characteristic gases.

Description

Technical Field

[0001] The invention belongs to the technical field of insulating oils and relates to a natural ester insulating oil resistant to gas generation and a preparation method thereof. Background Art

[0002] Due to rising electricity consumption, substations are gradually expanding, and the number of transformers is also increasing. Transformer oil increases the insulation strength of transformer components, provides heat dissipation and cooling during operation, and prevents corona and arc discharge. The quality of transformer oil directly impacts the safe operation of the transformer. Currently, transformer oil is primarily mineral insulating oil, a petroleum distillation product whose main components include alkanes, cycloalkanes, and aromatic unsaturated hydrocarbons. It is a light yellow, transparent liquid. Mineral insulating oil has a low flash point and poor water resistance, posing certain safety issues. Furthermore, its metabolism in soil or rivers is very slow, and any leakage would cause serious environmental pollution.

[0003] Natural ester insulating oil, also known as vegetable insulating oil, is primarily composed of triglycerides of fatty acids. It exhibits excellent environmental compatibility and biodegradability. It is typically extracted from oilseed crops such as rapeseed, soybeans, and tea seeds. It is used as an insulating fluid in transformers and similar electrical equipment. Natural ester insulating oil boasts advantages such as safety and environmental friendliness, a high flash point, easy degradation, and excellent moisture resistance. As an insulating and heat dissipating medium, it is widely used in the power sector, with natural ester insulating oil transformers being a key end-product. Compared to conventional mineral oil transformers, natural ester insulating oil transformers offer advantages such as longer insulation life, safety and environmental friendliness, and higher load capacity, making them a representative example of green transformers.

[0004] Under electrical or thermal stress, the insulating oil, paper, and other insulating materials within a transformer undergo chemical reactions, producing characteristic gases such as hydrogen, carbon monoxide, carbon dioxide, and low-molecular-weight hydrocarbons. Hydrogen and low-molecular-weight hydrocarbons are flammable gases, and their production in large quantities can pose a serious safety hazard to the transformer. Furthermore, the presence of these gases can accelerate the oxidation of the transformer insulating oil, leading to accelerated aging. However, natural ester insulating oils contain carbon-carbon unsaturated bonds and ester bonds, which predominantly lead to the oxidation mechanism of active olefinic radicals. These oils are rapidly oxidized in the early stages of oxidation and simultaneously initiate subsequent oxidation reactions, making them difficult to terminate once initiated. Therefore, developing a natural ester insulating oil with strong antioxidant properties and resistance to gas generation is of great significance. Summary of the Invention

[0005] To address the problems of poor oxidation resistance and high characteristic gas production in natural ester insulating oil, the present invention provides a gas-resistant natural ester insulating oil and a preparation method thereof. By adding an antioxidant and an anti-gassing agent to refined vegetable oil, the natural ester insulating oil is obtained. The natural ester insulating oil prepared by the present invention significantly reduces hydrogen and ethane production under thermal conditions, by 74.92% and 85.31%, respectively, compared to natural ester insulating oil without the anti-gassing agent. This oil exhibits enhanced oxidation resistance, ensuring safe transformer operation. The present invention provides a method for obtaining natural ester insulating oil with high oxidation resistance and low characteristic gas production under thermal conditions.

[0006] To achieve the technical purpose of the present invention, on the one hand, the present invention provides a natural ester insulating oil, which comprises, by mass, 96 to 98.2 parts of refined vegetable oil and 1 to 4 parts of additives.

[0007] Furthermore, in the natural ester insulating oil provided by the present invention, various parameters of the refined vegetable oil meet the requirements of DL / T 1811. The raw material for preparing the refined vegetable oil is selected from at least one of rapeseed oil, soybean oil, corn oil, sunflower oil, and peanut oil.

[0008] Furthermore, the natural ester insulating oil provided herein includes additives, by weight, including 1 part antioxidant and 0.8-3 parts anti-gassing agent. The antioxidant is selected from at least one of 2,6-di-tert-butyl-p-cresol (BHT), butylated hydroquinone, butylated hydroxyanisole, and tocopherol. The anti-gassing agent is a mixture of component A and component B, wherein component A is selected from a salicylate ester and its derivatives, and component B is n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0009] Furthermore, in the natural ester insulating oil provided by the present invention, the salicylate is specifically isoamyl o-hydroxybenzoate; the salicylate derivative is specifically benzyl o-hydroxybenzoate; and component A is oil-soluble. The mixing ratio of component A to component B is 1:15 to 1:20 by mass.

[0010] The present invention also claims the use of the aforementioned natural ester insulating oil to improve its performance. Improving the performance of natural ester insulating oil includes improving its oxidation resistance and reducing the production of characteristic gases. These characteristic gases are hydrogen (H2), acetylene (C2H2), methane (CH4), ethylene (C2H4), ethane (C2H6), carbon monoxide (CO), and carbon dioxide (CO2).

[0011] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0012] The natural ester insulating oil provided by the present invention possesses enhanced antioxidant properties without sacrificing its excellent high-temperature performance, environmental friendliness, and high flash point, thereby ensuring safe transformer operation. The dielectric loss factor (90°C), kinematic viscosity (40°C), acid value, power frequency breakdown voltage (2.5 mm), and flash point (closed cup) measured after 48 hours at 120°C show minimal changes. However, the increase in the total acid value, dielectric loss factor (90°C), and kinematic viscosity (40°C) measured in the 48-hour oxidation stability test is minimal, demonstrating the enhanced antioxidant properties of the natural ester insulating oil provided by the present invention.

[0013] The natural ester insulating oil provided by the present invention can reduce the production of characteristic gases caused by heat, including hydrogen, acetylene, methane, ethylene, ethane, carbon monoxide, and carbon dioxide. It can significantly reduce the production of hydrogen and ethane by 74.92% and 85.31%, respectively. By reducing the production of these characteristic gases, the serious safety hazards posed to transformers by the excessive production of hydrogen and ethane can be mitigated, preventing the accelerated aging of the natural ester insulating oil caused by these gases. DETAILED DESCRIPTION

[0014] The technical solutions of the present invention are described below with reference to the following examples. However, the present invention is not limited to the following examples. The experimental methods and detection methods described in each example are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0015] Example 1

[0016] This embodiment provides a natural ester insulating oil, which is prepared by the following steps:

[0017] 1) Decolorization: Pour 98 parts by weight of rapeseed oil into a decolorization tank and heat it to 80±5°C. Add 4% of the oil weight of an adsorbent and stir under vacuum for decolorization for 1.5 hours. Then, filter the oil using a filter device with a 1 μm pore size filter membrane to remove solid matter. The decolorized oil sample is obtained and the acid value of the oil sample is tested.

[0018] 2) Alkali refining: Pour the decolorized oil sample into the alkali refining tank and raise the oil temperature to 50±5℃. Under stirring conditions, add 25% of the volume of the oil sample with a potassium hydroxide solution at a flow rate of 3mL / min (the concentration of the potassium hydroxide solution is 15 times the theoretical amount of alkali to neutralize the acidic substances in the oil). After the potassium hydroxide solution is added, continue stirring and react for 2h. Then transfer the reaction mixture into a centrifuge tube for oil-water separation, remove the lower aqueous solution, and obtain the alkali-refined oil sample.

[0019] 3) Water washing: Transfer the alkali-refined oil sample into a water washing tank and heat it to 85±5°C. Add deionized water at the same temperature as the oil sample, which is 25% of the oil volume. React under stirring for 1 hour. Then transfer the reaction mixture into a centrifuge tube for oil-water separation, remove the lower aqueous solution, and obtain refined vegetable oil.

[0020] 4) Preparation of natural ester insulating oil: Weigh 1 part by mass of 2,6-di-tert-butyl-p-cresol, 0.05 part by mass of isoamyl o-hydroxybenzoate, 0.95 part by mass of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and 98 parts by mass of refined vegetable oil and add them to a reaction tank. Raise the temperature to 75±5°C under vacuum conditions, stir and react for 3 hours, and then filter using a filter device with a 1μm pore size filter membrane to obtain 1# natural ester insulating oil.

[0021] Example 2

[0022] This example provides a natural ester insulating oil. Its preparation method is the same as that of Example 1, except that: 96 parts by mass of refined vegetable oil, 0.16 parts by mass of isoamyl o-hydroxybenzoate, and 2.84 parts by mass of n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate are used. The resulting natural ester insulating oil, #2, has a composition shown in Table 1.

[0023] Example 3

[0024] This example provides a natural ester insulating oil. Its preparation method is the same as that of Example 1, except that soybean oil is used for decolorization, 98.2 parts by mass of refined vegetable oil are added, butylated hydroxyanisole is used as an antioxidant, and a mixture of 0.05 parts by mass of benzyl o-hydroxybenzoate and 0.75 parts by mass of n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is used as an anti-gassing agent. The resulting natural ester insulating oil, #3, has a composition as shown in Table 1.

[0025] Example 4

[0026] This example provides a natural ester insulating oil. Its preparation method is the same as that of Example 1, except that peanut oil is used for decolorization, 97.95 parts by weight of refined vegetable oil is added, tocopherol is used as an antioxidant, and 1 part by weight of n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate is added. The resulting natural ester insulating oil, #4, has a composition shown in Table 1.

[0027] Comparative Example 1

[0028] This comparative example provides a natural ester insulating oil, which is prepared by the same method as in Example 1, except that no anti-gas generating agent is added, and the amount of refined vegetable oil added is 99 parts by mass. 5# natural ester insulating oil is prepared, and its component composition is shown in Table 1.

[0029] Comparative Example 2

[0030] This comparative example provides a natural ester insulating oil prepared by the same method as in Example 1, except that isoamyl o-hydroxybenzoate was added as an anti-gassing agent in an amount of 1 part by mass. A 6# natural ester insulating oil was prepared, the composition of which is shown in Table 1.

[0031] Comparative Example 3

[0032] This comparative example provides a natural ester insulating oil prepared by the same method as in Example 1, except that 1 part by mass of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate was added as an anti-gassing agent. The resulting natural ester insulating oil, #7, has a composition shown in Table 1.

[0033] Table 1: Composition of natural ester insulating oil

[0034]

[0035] Example 5

[0036] This example provides a performance index test of the natural ester insulating oil prepared in Examples 1 to 4 and Comparative Examples 1 to 3, which specifically includes the following steps:

[0037] The kinematic viscosity (40°C) was determined in accordance with GB / T 265; the dielectric loss factor (90°C) was determined in accordance with GB / T 5654; ​​the acid value was determined in accordance with GB / T 5009.229; the breakdown voltage (2.5 mm) was determined in accordance with GB / T 507; the flash point was determined in accordance with GB / T 261; and the 48-hour oxidation stability was determined in accordance with NB / SH / T 0811. The conditions were modified to place a 25g sample in an oil bath at 110°C in the presence of a copper catalyst, with air introduced at a flow rate of 1 L / h. After 48 hours of oxidation, the total acid value (the sum of the oil-soluble acid value (SA) and the volatile acid value (VA)), dielectric loss factor (90°C), and kinematic viscosity (40°C) of the insulating oil were determined. The results are shown in Table 2.

[0038] The antioxidant capacity of natural ester insulating oil is measured by the total acid value (TA), dielectric loss factor (90°C), and increase in kinematic viscosity (40°C) after a 48-hour oxidation stability test. Lower TA, lower dielectric loss factor (90°C), and smaller increase in kinematic viscosity (40°C) indicate stronger antioxidant capacity, while lower values ​​indicate weaker antioxidant capacity.

[0039] Table 2: Performance test results of natural ester insulating oil

[0040]

[0041] Table 2 shows that the natural ester insulating oil provided by the present invention can reduce the increase in total acid value, dielectric loss factor (90°C), and kinematic viscosity (40°C) after a 48-hour oxidation stability test, indicating that the natural ester insulating oil provided by the present invention has improved antioxidant properties. The natural ester insulating oil prepared by the present invention does not change its other properties (dielectric loss factor (90°C), kinematic viscosity (40°C), acid value, power frequency breakdown voltage (2.5 mm), and flash point (closed cup)). This means that the natural ester insulating oil prepared by the present invention maintains its excellent high-temperature performance and environmentally friendly properties while also improving its antioxidant properties, ensuring safe operation of transformers.

[0042] Example 6

[0043] This example provides a performance index test of the natural ester insulating oil prepared in Examples 1 to 4 and Comparative Examples 1 to 3, which specifically includes the following steps:

[0044] The determination of dissolved gas (characteristic gas) in natural ester insulating oil shall refer to GB / T 17623.

[0045] Simulated temperature rise test: Equal amounts of 1#, 2#, 3#, 4#, 5#, 6#, and 7# natural ester insulating oils that comply with DL / T 1811 standard were loaded into a sealable glass reactor with a lid. Dry nitrogen was then passed through the reaction vessel for 1 minute, and the vessel was sealed with a lid. The reaction was then placed in a 90°C oven for reaction for 24 hours. The vessel was then taken out and cooled to room temperature, and the dissolved gas (characteristic gas) in the insulating oil was tested (Tables 3 and 4).

[0046] Table 3: Comparison of dissolved gases in natural ester insulating oil before and after simulated temperature rise test

[0047]

[0048] Table 4: Comparison of dissolved gases in natural ester insulating oil before and after simulated temperature rise test

[0049]

[0050] As shown in Tables 3 and 4, the natural ester insulating oil provided by the present invention has a lower dissolved gas production before and after temperature rise compared to the 5# natural ester insulating oil without the addition of an anti-gas generation agent. The 6# and 7# natural ester insulating oils, to which only isoamyl o-hydroxybenzoate or n-octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is added, also have a lower dissolved gas production before and after temperature rise compared to the 5# natural ester insulating oil, but the reduction effect is not significant. This indicates that isoamyl o-hydroxybenzoate and n-octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate can reduce the dissolved gas production in natural ester insulating oil when used alone, but the effect is poor. When these two are mixed and used as an anti-gas generation agent, the dissolved gas production in the natural ester insulating oil can be greatly reduced, with the production of hydrogen and ethane being significantly reduced by 74.92% and 85.31%, respectively. The natural ester insulating oil provided by the present invention generates less characteristic gas during use and has higher safety performance. At the same time, it can slow down the oxidation of transformer insulating oil and reduce the aging speed.

[0051] The embodiments described above are part of the embodiments of the present invention, rather than all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but merely represents selected embodiments of the present invention. All other embodiments obtained without creative effort and through deduction and substitution by a person of ordinary skill in the art based on the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A natural ester insulating oil, characterized in that: Calculated by mass, it comprises 96 to 98.2 parts of refined vegetable oil and 1 to 4 parts of additives; The raw material for preparing the refined vegetable oil is selected from at least one of rapeseed oil, soybean oil, corn oil, sunflower oil, peanut oil and hemp oil; In parts by mass, the additives include: 1 part of antioxidant and 0.8 to 3 parts of anti-gas generating agent; The anti-gas generation agent is obtained by mixing component A and component B; The component A is selected from salicylates and their derivatives; The component B is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; The salicylate is specifically isoamyl o-hydroxybenzoate; The salicylate derivative is specifically benzyl o-hydroxybenzoate.

2. The natural ester insulating oil according to claim 1, characterized in that In terms of mass ratio, the mixing ratio of the component A to the component B is 1:15 to 1:

20.

3. The natural ester insulating oil according to claim 1, characterized in that The antioxidant is selected from at least one of 2,6-di-tert-butyl-p-cresol, butylated hydroquinone, butylated hydroxyanisole and tocopherol.

4. Use of the natural ester insulating oil according to any one of claims 1 to 3 in improving the performance of natural ester insulating oil, characterized in that: The improved performance of natural ester insulating oil includes improving oxidation resistance and reducing the amount of characteristic gas generated.

5. The use according to claim 4, characterized in that The characteristic gases are hydrogen, acetylene, methane, ethylene, ethane, carbon monoxide, and carbon dioxide.

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