A compounded additive and its use in removing corrosive sulfur products from mineral insulating oil

Abstract

This invention discloses a compound additive and its application in removing corrosive sulfur from mineral insulating oil, relating to the field of insulating oil additives. It includes a first inhibitor, a second inhibitor, a first antioxidant, and a second antioxidant. The first inhibitor is a benzotriazole derivative, and the second inhibitor is a thiadiazole derivative and / or methylbenzotriazole. The first antioxidant is pyrogallol, and the second antioxidant is butylated hydroxytoluene and / or tert-butylhydroquinone. This additive uses a compound inhibitor and a compound antioxidant. When applied to mineral insulating oil, the synergistic effect of the compound inhibitor improves the insulating oil's resistance to corrosive sulfur. Simultaneously, the compound antioxidant and compound inhibitor are balanced to maximize the insulating oil's oxidation resistance, providing continuous and efficient protection for mineral insulating oil in actual operation, resulting in excellent physical and electrical properties.

Description

Technical Field

[0001] This invention relates to the field of insulating oil additives, and more particularly to a compound additive and its application in removing corrosive sulfur products from mineral insulating oils. Background Technology

[0002] Currently, the insulating oil used in oil-immersed transformers is mainly divided into mineral insulating oil and ester-based insulating oil. Among them, the presence of corrosive sulfur in mineral insulating oil has attracted widespread attention due to its deterioration in the insulation performance of transformers and reactors, leading to insulation faults. Corrosive sulfur refers to elemental sulfur or unstable sulfides that can react with metals under certain conditions to form metal sulfides, exhibiting strong corrosiveness to metals. Corrosive sulfur mainly includes elemental sulfur, hydrogen sulfide, thiols, and some small-molecule sulfides. These react with copper metal to form light blue and dark gray deposits (cuprous sulfide), a semi-conductive substance that seeps into the oil-paper insulation system, causing insulation breakdown and thus degrading the transformer's insulation performance, significantly affecting the safe and stable operation of the transformer.

[0003] Currently, the main methods for removing corrosive sulfur from mineral oil include replacing the oil, filtering the oil, and adding inhibitors. Among these, adding inhibitors is relatively economical and effective, and has been widely used to remove corrosive sulfur from mineral insulating oil. Common inhibitors include T551, T561, TTA, and BTA, all of which are benzotriazole and its derivatives. Their inhibition mechanism is a film-forming reaction mechanism. During the reaction, the branch chain attached to the nitrogen atom on the benzotriazole ring breaks, and the nitrogen atom chelates with copper to form a benzotriazole-copper coordination compound. This film can protect the copper winding from corrosion by corrosive sulfur in the oil.

[0004] However, while inhibitors remove corrosive sulfur from mineral oils, they also affect the oil's antioxidant capacity, reducing its service life. There is an urgent need to find technologies that can balance the corrosive sulfur content in mineral oils while ensuring their antioxidant capacity for industrial applications. Summary of the Invention

[0005] This invention provides a compound additive and its application in removing corrosive sulfur from mineral insulating oil. By using compound inhibitors and compound antioxidants, when added to mineral insulating oil, the corrosion resistance and oxidation resistance of the insulating oil can be maximized, providing continuous and efficient protection for mineral insulating oil in actual operation.

[0006] To address the aforementioned technical problems, one objective of this invention is to provide a compound additive comprising an inhibitor and an antioxidant. The inhibitor comprises a first inhibitor and a second inhibitor, wherein the first inhibitor is a benzotriazole derivative and the second inhibitor is a thiadiazole derivative and / or methyltriazole; the antioxidant comprises a first antioxidant and a second antioxidant, wherein the first antioxidant is pyrogallol and the second antioxidant is butylated hydroxytoluene and / or tert-butylhydroquinone; the first inhibitor accounts for more than 40 wt% of the compound additive by mass, and the first antioxidant accounts for more than 20 wt% of the compound additive by mass.

[0007] By adopting the above scheme, this application addresses the problem of reduced antioxidant capacity and shortened service life of mineral insulating oil in previous studies on desulfurization inhibitors. The additive uses a compound inhibitor and a compound antioxidant. Among them, the pyrogallol antioxidant has a lower dissociation energy, stronger antioxidant activity, the largest number of effective phenolic hydroxyl groups per unit mass, and a higher DPPH scavenging rate. The benzotriazole derivative inhibitor has strong anti-corrosion sulfur ability and low impact on the antioxidant capacity of insulating oil. When applied to the field of mineral insulating oil, the synergistic effect of the compound inhibitor improves the anti-corrosion sulfur ability of the insulating oil. Through the breakage of the branch chain attached to the nitrogen atom on the benzotriazole ring of the inhibitor during the reaction process, the nitrogen atom chelates with the metal to form a benzotriazole-metal coordination compound. The film formed can protect the metal from corrosion by corrosive sulfur in the oil. At the same time, the compound antioxidant and compound inhibitor are balanced to maximize the antioxidant capacity of the insulating oil. It has a good effect on improving the physical and electrical properties of mineral insulating oil, providing continuous and efficient protection for mineral insulating oil in actual operation, with excellent comprehensive performance.

[0008] As a preferred embodiment, the first inhibitor accounts for 40wt%-50wt% of the mass fraction in the compound additive, and the first antioxidant accounts for 20wt%-25wt% of the mass fraction in the compound additive.

[0009] As a preferred option, it includes an inhibitor and an antioxidant in a mass ratio of (3-5):(2-3).

[0010] By adopting the above scheme, this application controls the addition ratio of inhibitors and antioxidants, which can maximize the anti-corrosion sulfur ability and anti-oxidation ability of insulating oil, avoid the inhibitor from affecting the anti-oxidation ability of insulating oil, and at the same time ensure that the insulating oil has excellent anti-corrosion sulfur ability and excellent overall performance.

[0011] As a preferred embodiment, it includes a first inhibitor, a second inhibitor, a first antioxidant, and a second antioxidant in a mass ratio of (2-4):1:(1-2):1.

[0012] As a preferred embodiment, the mass ratio of the first inhibitor, the second inhibitor, the first antioxidant, and the second antioxidant is 4:1:2:1.

[0013] As a preferred embodiment, the second inhibitor is methyltriazole and the second antioxidant is butylated hydroxytoluene.

[0014] To address the aforementioned technical problems, a second objective of this invention is to provide the application of a compound additive in the removal of corrosive sulfur from mineral insulating oil.

[0015] To address the aforementioned technical problems, a third objective of this invention is to provide a mineral insulating oil with good sulfur resistance, comprising a compound additive with a mass fraction of 0.1wt%-1wt%.

[0016] As a preferred embodiment, it further includes 90wt%-99.9wt% mineral oil matrix and 1wt%-9wt% functional additives, wherein the functional additives are at least one of preservatives, antifoaming agents, deemulsifiers, and detergents.

[0017] As a preferred embodiment, the mineral oil matrix is ​​Xinjiang Karamay No. 25 mineral oil.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This application uses a compound inhibitor and a compound antioxidant as additives. When applied to mineral insulating oils, the synergistic effect of the compound inhibitors improves the insulating oil's resistance to corrosive sulfur. During the reaction process, the side chains attached to the nitrogen atoms on the benzotriazole ring of the inhibitor break, and the nitrogen atoms chelate with the metal to form a benzotriazole-metal coordination compound. This compound forms a film that protects the metal from corrosion by the corrosive sulfur in the oil. At the same time, the compound antioxidants and compound inhibitors are balanced to maximize the antioxidant capacity of the insulating oil, providing continuous and efficient protection for mineral insulating oils in actual operation. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms "comprising," "including," "having," and "containing" used in this article are all open-ended, meaning they include but are not limited to. Unless otherwise specified, all raw materials used are commercially available, and the same raw materials were used in parallel experiments.

[0025] Example 1

[0026] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and a thiadiazole derivative (T561), and the antioxidant is pyrogallol (PY) and butylated hydroxytoluene (BHT). Specifically, it includes benzotriazole derivative (T551), thiadiazole derivative (T561), pyrogallol (PY), and butylated hydroxytoluene (BHT) in a mass ratio of 4:1:2:1.

[0027] Example 2

[0028] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and methyltriazole (TAA), and the antioxidant is pyrogallol (PY) and tert-butylhydroquinone (TBHQ). Specifically, it includes a benzotriazole derivative (T551), methyltriazole (TTA), pyrogallol (PY), and tert-butylhydroquinone (TBHQ) in a mass ratio of 4:1:2:1.

[0029] Example 3

[0030] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and a thiadiazole derivative (T561), and the antioxidant is pyrogallol (PY) and tert-butylhydroquinone (TBHQ). Specifically, it includes benzotriazole derivative (T551), thiadiazole derivative (T561), pyrogallol (PY), and tert-butylhydroquinone (TBHQ) in a mass ratio of 4:1:2:1.

[0031] Example 4

[0032] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and methyltriazole (TAA), and the antioxidant is pyrogallol (PY) and butylated hydroxytoluene (BHT). Specifically, it includes a benzotriazole derivative (T551), methyltriazole (TTA), pyrogallol (PY), and butylated hydroxytoluene (BHT) in a mass ratio of 4:1:2:1.

[0033] Example 5

[0034] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and a thiadiazole derivative (T561), and the antioxidant is pyrogallol (PY) and butylated hydroxytoluene (BHT). Specifically, it includes benzotriazole derivative (T551), thiadiazole derivative (T561), pyrogallol (PY), and butylated hydroxytoluene (BHT) in a mass ratio of 2:1:1:1.

[0035] Example 6

[0036] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and methyltriazole (TAA), and the antioxidant is pyrogallol (PY) and tert-butylhydroquinone (TBHQ). Specifically, it includes a benzotriazole derivative (T551), methyltriazole (TTA), pyrogallol (PY), and tert-butylhydroquinone (TBHQ) in a mass ratio of 2:1:1:1.

[0037] Example 7

[0038] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and a thiadiazole derivative (T561), and the antioxidant is pyrogallol (PY) and tert-butylhydroquinone (TBHQ). Specifically, it includes benzotriazole derivative (T551), thiadiazole derivative (T561), pyrogallol (PY), and tert-butylhydroquinone (TBHQ) in a mass ratio of 2:1:1:1.

[0039] Example 8

[0040] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and methyltriazole (TAA), and the antioxidant is pyrogallol (PY) and butylated hydroxytoluene (BHT). Specifically, it includes a benzotriazole derivative (T551), methyltriazole (TTA), pyrogallol (PY), and butylated hydroxytoluene (BHT) in a mass ratio of 2:1:1:1.

[0041] Comparative Example 1

[0042] A compound additive includes an inhibitor and an antioxidant in a mass ratio of 3:2, wherein the inhibitor is a benzotriazole derivative (T551) and the antioxidant is pyrogallol (PY).

[0043] Comparative Example 2

[0044] A compound additive includes an inhibitor and an antioxidant in a mass ratio of 5:3, wherein the inhibitor is a benzotriazole derivative (T551) and the antioxidant is pyrogallol (PY).

[0045] Comparative Example 3

[0046] An additive comprising an inhibitor, wherein the inhibitor is a benzotriazole derivative (T551).

[0047] Comparative Example 4

[0048] An additive comprising an inhibitor, wherein the inhibitor is a thiadiazole derivative (T561).

[0049] Comparative Example 5

[0050] An additive that includes an inhibitor, wherein the inhibitor is methyltriazole (TAA).

[0051] Comparative Example 6

[0052] An additive that includes an antioxidant, wherein the antioxidant is pyrogallol (PY).

[0053] Comparative Example 7

[0054] An additive includes an antioxidant, wherein the antioxidant is butylated hydroxytoluene (BHT).

[0055] Comparative Example 8

[0056] An additive includes an antioxidant, wherein the antioxidant is tert-butylhydroquinone (TBHQ).

[0057] Comparative Example 9

[0058] A compound additive includes an inhibitor and an antioxidant. The inhibitor is 2,6-di-tert-butyl-p-cresol (DBPC) and methyltriazole (TAA), and the antioxidant is pyrogallol (PY) and butylated hydroxytoluene (BHT). Specifically, it includes 2,6-di-tert-butyl-p-cresol (DBPC), methyltriazole (TTA), pyrogallol (PY), and butylated hydroxytoluene (BHT) in a mass ratio of 2:1:1:1.

[0059] Comparative Example 10

[0060] A compound additive includes an inhibitor and an antioxidant. The inhibitor is 1,2,3-benzotriazole (BTA) and methyltriazole (TAA), and the antioxidant is pyrogallol (PY) and butylated hydroxytoluene (BHT). Specifically, it includes 1,2,3-benzotriazole (BTA), methyltriazole (TTA), pyrogallol (PY), and butylated hydroxytoluene (BHT) in a mass ratio of 2:1:1:1.

[0061] Comparative Example 11

[0062] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and methyltriazole (TAA), and the antioxidant is 2,6-di-tert-butyl-p-cresol (T501) and butylated hydroxytoluene (BHT). Specifically, it includes a benzotriazole derivative (T551), methyltriazole (TTA), 2,6-di-tert-butyl-p-cresol (T501), and butylated hydroxytoluene (BHT) in a mass ratio of 2:1:1:1.

[0063] Comparative Example 12

[0064] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and methyltriazole (TAA), and the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester (1076) and butylated hydroxytoluene (BHT). Specifically, it includes a benzotriazole derivative (T551), methyltriazole (TTA), β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester (1076) and butylated hydroxytoluene (BHT) in a mass ratio of 2:1:1:1.

[0065] Comparative Example 13

[0066] A compound additive includes an inhibitor and an antioxidant. The inhibitor is a benzotriazole derivative (T551) and methyltriazole (TAA), and the antioxidant is pyrogallol (PY) and butylated hydroxytoluene (BHT). Specifically, it includes a benzotriazole derivative (T551), methyltriazole (TTA), pyrogallol (PY), and butylated hydroxytoluene (BHT) in a mass ratio of 8:2:2:1.

[0067] Application Example 1-8 and Comparative Application Example 1-12

[0068] The application of a compound additive in the removal of corrosive sulfur from mineral insulating oil includes the following steps:

[0069] Add 0.8% by mass of the additives from Examples 1-8 or Comparative Examples 1-12 to the mineral insulating oil. The mineral insulating oil is Xinjiang Karamay No. 25 mineral oil. At room temperature, the oil sample is placed on a magnetic stirrer and stirred thoroughly for 6 hours to ensure that the solid particles of the compounded additives are fully dissolved in the oil sample. After dissolution, the oil sample is clear and free of suspension, and the color is slightly darker.

[0070] Comparative Application Example 13

[0071] The application of a compound additive in the removal of corrosive sulfur from synthetic ester insulating oil includes the following steps:

[0072] Add 0.8% by mass of the additive from Example 4 to the synthetic ester insulating oil. The synthetic ester insulating oil selected was Midel 7131. The oil sample was placed on a magnetic stirrer and stirred thoroughly for 6 hours at room temperature using a small to medium-sized oval stir bar to ensure that the solid particles of the compounded additive were fully dissolved in the oil sample. After dissolution, the oil sample was clear and free of suspension, and the color was slightly darker.

[0073] Comparative Application Example 14

[0074] The application of a compound additive in the removal of corrosive sulfur from natural ester insulating oil includes the following steps:

[0075] Additive from Example 4 at a mass fraction of 0.8% was added to the natural ester insulating oil. The natural ester insulating oil selected was FR3. The oil sample was placed on a magnetic stirrer and stirred thoroughly for 6 hours at room temperature using a small to medium-sized oval stir bar to ensure that the solid particles of the compounded additive were fully dissolved in the oil sample. After dissolution, the oil sample was clear and free of suspension, and the color was slightly darker.

[0076] Comparative Application Example 15

[0077] The application of a compound additive in the removal of corrosive sulfur from mineral insulating oil includes the following steps:

[0078] Additive 13 of Comparative Example 13 was added to the mineral insulating oil at a mass fraction of 1.3%. The mineral insulating oil was Xinjiang Karamay No. 25 mineral oil. The oil sample was placed on a magnetic stirrer and stirred thoroughly for 6 hours at room temperature using a small to medium-sized oval stir bar to ensure that the solid particles of the compound additive were fully dissolved in the oil sample. After dissolution, the oil sample was clear and free of suspension, and the color was slightly darker.

[0079] Performance testing

[0080] 1. Mineral insulating oil, natural ester insulating oil, and synthetic ester insulating oil without additives were used as blank insulating oil samples. The oil samples from the application examples and comparative application examples, after processing, were used as test oil samples, according to GB standards.

[0081] The standard 2536--2011, "Unused Mineral Insulating Oil for Electrical Fluid Transformers and Switches," adopts the SH / T0804 test method for corrosive sulfur in electrical insulating oil using a silver sheet. The treated silver sheet is kept in insulating oil at 100°C for 18 hours. After the experiment, the potential corrosive sulfur in the tested oil sample is determined by observing the surface changes of the silver sheet. The determination method is shown in Table 1 below. The effects of different additives in removing corrosive sulfur from insulating oil in the examples and comparative examples are compared, and the test results are shown in Table 2 below.

[0082] Table 1 - Criteria for Judging the Corrosivity of Silver Sheets in the Silver Sheet Test Method

[0083]

[0084] Table 2 - Silver sheet test results of insulating oil in application examples and comparative application examples of this application

[0085]

[0086]

[0087]

[0088] 2. Mineral insulating oil without additives was used as the blank insulating oil sample. The oil samples processed from the application examples and comparative application examples were used as test oil samples. The initial oxidation temperature of the oil samples was measured according to DL / T 1977-2019 "Determination of Oxidation Stability of Mineral Insulating Oils - Differential Scanning Calorimetry". According to GB / T 7595-2008 "Quality Standard for Transformer Oil in Operation", the oil samples were sealed and placed in a forced-air drying oven for a 15-day oxidation experiment at a temperature of 180℃. The acid value, viscosity, and dielectric loss at 90℃ of the oil samples after the oxidation experiment were tested. The test results are shown in Table 3 below.

[0089] Table 3 - Oxidation test results of insulating oil in application examples and comparative application examples of this application

[0090]

[0091]

[0092] As shown in Table 1-2, comparing Application Examples 1-4 with Comparative Application Example 2 and Application Examples 5-8 with Comparative Application Example 1, it can be seen that when Application Examples 1-8 use compound inhibitors and composite antioxidants added to the insulating oil, the insulating oil has high resistance to sulfur corrosion, no discoloration occurs in the silver sheet test, and after oxidation testing, the insulating oil has a higher initial oxidation temperature, lower acid value, lower dielectric loss, and lower viscosity compared to the blank mineral insulating oil, indicating excellent antioxidant performance. In contrast, Comparative Application Examples 1-2 use a single inhibitor and a single antioxidant added to the insulating oil, resulting in a significant golden discoloration in the silver sheet test, indicating insufficient resistance to sulfur corrosion. After oxidation testing, the initial oxidation temperature of the insulating oil is lower than that of Application Examples 1-8, while the acid value of Comparative Application Example 1 increases and the dielectric loss is lower than that of Application Examples 1-8, indicating that the antioxidant capacity of the insulating oil in Comparative Application Examples 1-2 is not as good as that in Examples 1-8.

[0093] As shown in Table 1-2, comparing Application Examples 1-8 with Comparative Application Examples 3-5 and 6-8 reveals that Comparative Application Examples 3-5, which only added a single inhibitor, resulted in insufficient sulfur resistance of the insulating oil, causing a golden discoloration in the silver sheet test. Furthermore, no antioxidant was added, as the inhibitor reduces the insulating oil's inherent antioxidant capacity, leading to lower oxidation resistance, lower initial oxidation temperature, higher acid value, and higher dielectric loss and viscosity compared to the blank insulating oil. Comparative Application Examples 6-8, which did not add an inhibitor, showed significantly poor sulfur resistance of the insulating oil, but the increased proportion of antioxidant in the insulating oil resulted in better oxidation resistance.

[0094] As shown in Table 1-2, comparing Application Example 8 with Comparative Application Examples 9-10 and 11-12, it can be seen that when the inhibitor T551 in Comparative Application Examples 9-10 was replaced in equal amounts with other inhibitors such as DBPC or BTA, a significant golden-yellow discoloration was observed in the silver sheet test, indicating a decrease in the ability to resist sulfur corrosion. This shows that the addition of inhibitor T551 can effectively improve the sulfur corrosion resistance of insulating oil compared to other inhibitors. When the antioxidant PY in Comparative Application Examples 11-12 was replaced in equal amounts with other antioxidants such as T501 or 1076, the antioxidant capacity of the insulating oil decreased, indicating that the antioxidant PY used in this application is better than other antioxidants.

[0095] As shown in Table 1-2, comparing Application Example 4 and Comparative Application Example 15, it can be seen that the total amount of inhibitor in the insulating oil of Comparative Application Example 15 is higher than that of Application Example 14. With the same antioxidant content, the increased total amount of inhibitor leads to a decrease in the antioxidant capacity of the insulating oil, a lower initial oxidation temperature, and an increase in acid value and dielectric loss. This indicates that the content of inhibitor affects the antioxidant capacity of the insulating oil. By controlling the addition ratio of inhibitor and antioxidant in this application, the corrosion resistance and antioxidant capacity of the insulating oil can be maximized, resulting in excellent overall performance.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. The application of a compound additive in the removal of corrosive sulfur from mineral insulating oil, characterized in that, The compound additive comprises an inhibitor and an antioxidant in a mass ratio of (3-5):(2-3). The inhibitor comprises a first inhibitor and a second inhibitor, wherein the first inhibitor is a benzotriazole derivative and the second inhibitor is a thiadiazole derivative and / or methyltriazole. The antioxidant comprises a first antioxidant and a second antioxidant, wherein the first antioxidant is pyrogallol and the second antioxidant is butylated hydroxytoluene and / or tert-butylhydroquinone. The first inhibitor accounts for 40wt%-50wt% of the mass fraction in the compound additive, and the first antioxidant accounts for 20wt%-25wt% of the mass fraction in the compound additive. When the second inhibitor is methyltriazole, the second antioxidant is tert-butylhydroquinone; Or, when the second inhibitor is a thiadiazole derivative, the second antioxidant is butylated hydroxytoluene.

2. The application of the compound additive as described in claim 1 in the removal of corrosive sulfur from mineral insulating oil, characterized in that, It includes a first inhibitor, a second inhibitor, a first antioxidant, and a second antioxidant in a mass ratio of (2-4):1:(1-2):

1.

3. The application of the compound additive as described in claim 1 in the removal of corrosive sulfur from mineral insulating oil, characterized in that, The mass ratio of the first inhibitor, the second inhibitor, the first antioxidant, and the second antioxidant is 4:1:2:

1.

4. A mineral insulating oil with good sulfur resistance, characterized in that, The compound additives described in any one of claims 1-3 include those with a mass fraction of 0.1wt%-1wt%.

5. The mineral insulating oil with good sulfur resistance as described in claim 4, characterized in that, It also includes 90wt%-99.9wt% mineral oil matrix and 1wt%-9wt% functional additives, wherein the functional additives are at least one of preservatives, antifoaming agents, deemulsifiers, and detergents.

6. The mineral insulating oil with good sulfur resistance as described in claim 5, characterized in that, The mineral oil matrix is ​​Xinjiang Karamay No. 25 mineral oil.

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