A Cu-based insulating fluid for transformers and its preparation method and application

Abstract

The present invention provides a Cu-based insulating fluid for mitigating misjudgments of transformer discharge faults, as well as a preparation method and application thereof. The preparation method comprises the following steps: 1) mixing a NaOH solution with a CuSO4 solution, then adding an ascorbic acid aqueous solution, and stirring to obtain a suspension; 2) centrifuging and washing the suspension obtained in step 1) in sequence to obtain a copper-based catalyst; 3) wrapping the copper-based catalyst obtained in step 2) with insulating paper, and then immersing the copper-based catalyst in mineral oil after arc discharge, thereby preparing a Cu-based insulating fluid for mitigating misjudgments of transformer discharge faults. The Cu-based insulating fluid of the present invention can quantify the conversion content of acetylene, hydrogen, and ethylene gases, which is beneficial for mitigating false alarms and omissions of the three-ratio method from a catalytic perspective.

Description

Technical Field

[0001] The present invention relates to the field of fault early warning of dissolved gas in transformer oil, and in particular to a Cu-based insulating fluid for transformers, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of high-voltage technology, power transformers, as key components of power grids, play a vital role in their safe operation and maintenance. Dissolved gas analysis (DGA) has been widely used to assess the condition of power transformers. When a transformer overheats or experiences a discharge defect, the solid insulation material decomposes to produce CO and CO2, and the insulating oil decomposes to produce gases such as H2, CH4, C2H2, C2H4, and C2H6, which dissolve in the oil and reduce its dielectric strength. Arc discharges generate large amounts of hydrogen and acetylene. Under the action of metallic copper, acetylene undergoes catalytic hydrogenation, partially converting the acetylene into ethylene, which can even be further hydrogenated to produce ethane. This can lead to misjudgments using the three-ratio method. If not detected promptly, this poses a significant challenge to the safe operation and maintenance of existing transformers. Summary of the Invention

[0003] The purpose of the present invention is to provide a Cu-based insulating fluid for transformers and its preparation method and application, so as to solve the problems existing in the above-mentioned prior art, reduce the frequent false alarms and missed alarms of the transformer three-ratio method, and ensure the safe operation of the transformer.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a Cu-based insulating fluid for alleviating misjudgment of transformer discharge faults, comprising the following steps:

[0006] 1) Mixing NaOH solution and CuSO4 solution, then adding ascorbic acid aqueous solution and stirring to obtain a suspension;

[0007] 2) centrifuging and washing the suspension obtained in step 1) to obtain a copper-based catalyst;

[0008] 3) Wrapping the copper-based catalyst obtained in step 2) with insulating paper, and then immersing it in mineral oil after arc discharge, thereby preparing a Cu-based insulating fluid that reduces the misjudgment of transformer discharge faults.

[0009] Preferably, the volume ratio of the NaOH solution, CuSO4 solution and ascorbic acid aqueous solution added in step 1) is 10-150 mL: 5-40 mL: 20-350 mL.

[0010] Preferably, the concentration of the NaOH solution is 0.1-2.5 mol / L, the concentration of the CuSO4 solution is 0.1-3 mol / L, and the concentration of the ascorbic acid aqueous solution is 0.05-1 mol / L.

[0011] Preferably, the stirring is performed at 25-65° C., with a stirring speed of 200-800 r / min and a stirring time of 10-120 min.

[0012] Preferably, the centrifugation time in step 2) is 10-30 min, and the centrifugation speed is 1000-4000 r / min; the detergent used in the washing is deionized water and anhydrous ethanol, and the number of washing times is 2-8 times.

[0013] Preferably, a drying step is required after the washing is completed, and the drying time is 3 to 15 hours and the drying temperature is 40 to 120°C.

[0014] Preferably, in step 3), the usage ratio of the insulating paper, the copper-based catalyst and the mineral oil is 10-40 g: 25-80 g: 400 mL.

[0015] Preferably, the insulating paper in step 3) needs to be vacuum degassed before use, wherein the vacuum degree is 20-150 Pa, the temperature is 50-120° C., and the time is 24-72 h.

[0016] Preferably, the arc discharge time of the mineral oil is 15 hours.

[0017] Preferably, the immersion time is 15 to 30 hours.

[0018] Another object of the present invention is to provide a Cu-based insulating fluid prepared by the preparation method for mitigating misjudgment of transformer discharge faults.

[0019] Another object of the present invention is to provide an application of a Cu-based insulating fluid in the field of early warning of dissolved gas faults in transformer oil to mitigate misjudgment of transformer discharge faults.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The interaction between the insulating paper and the copper-based catalyst surface forms active species that catalyze the selective hydrogenation of acetylene. (2) Quantifying the conversion content of acetylene, hydrogen, and ethylene gases helps to mitigate the false positives and false negatives of the three-ratio method from a catalytic perspective. DETAILED DESCRIPTION

[0022] The present invention provides a method for preparing a Cu-based insulating fluid for alleviating misjudgment of transformer discharge faults, comprising the following steps:

[0023] 1) Mixing NaOH solution and CuSO4 solution, then adding ascorbic acid aqueous solution and stirring to obtain a suspension;

[0024] 2) centrifuging and washing the suspension obtained in step 1) to obtain a copper-based catalyst;

[0025] 3) Wrapping the copper-based catalyst obtained in step 2) with insulating paper, and then immersing it in mineral oil after arc discharge, thereby preparing a Cu-based insulating fluid that reduces the misjudgment of transformer discharge faults.

[0026] In the present invention, the volume ratio of the NaOH solution, CuSO4 solution and ascorbic acid aqueous solution added in step 1) is preferably 10-150 mL:5-40 mL:20-350 mL, more preferably 10-100 mL:10-40 mL:50-300 mL.

[0027] In the present invention, the concentration of the NaOH solution is preferably 0.1-2.5 mol / L, more preferably 0.5-2 mol / L.

[0028] In the present invention, the concentration of the CuSO4 solution is preferably 0.1-3 mol / L, more preferably 1-2.5 mol / L.

[0029] In the present invention, the concentration of the ascorbic acid aqueous solution is preferably 0.05 to 1 mol / L, more preferably 0.05 to 0.6 mol / L.

[0030] In the present invention, the stirring is preferably carried out at 25-65°C, wherein the stirring speed is preferably 200-800 r / min, more preferably 200-600 r / min; the stirring time is preferably 10-120 min, more preferably 10-60 min.

[0031] In the present invention, the centrifugation time in step 2) is preferably 10 to 30 min, more preferably 10 to 20 min; the centrifugation speed is preferably 1000 to 4000 r / min, more preferably 1000 to 3000 r / min; the detergent used for washing is deionized water and anhydrous ethanol, and the number of washings is preferably 2 to 8 times, more preferably 2 to 6 times.

[0032] In the present invention, a drying step is required after the washing is completed. The drying time is preferably 3 to 15 hours, more preferably 3 to 10 hours; the drying temperature is preferably 40 to 120°C, more preferably 40 to 100°C.

[0033] In the present invention, the usage ratio of the insulating paper, copper-based catalyst and mineral oil in step 3) is 10-40 g:25-80 g:400 mL, more preferably 10-30 g:30-65 g:400 mL.

[0034] In the present invention, the insulating paper in step 3) needs to be vacuum degassed before use, wherein the vacuum degree is preferably 20-150 Pa, more preferably 20-100 Pa; the temperature is preferably 50-120°C, more preferably 50-100°C; and the time is preferably 24-72 h, more preferably 40-60 h.

[0035] In the present invention, the arc discharge time of the mineral oil is 15 hours.

[0036] In the present invention, the immersion time is 15 to 30 hours.

[0037] Another object of the present invention is to provide a Cu-based insulating fluid prepared by the preparation method for mitigating misjudgment of transformer discharge faults.

[0038] Another object of the present invention is to provide an application of a Cu-based insulating fluid in the field of early warning of dissolved gas faults in transformer oil to mitigate misjudgment of transformer discharge faults.

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present description and examples are intended to be illustrative only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] Unless otherwise specified, the "room temperature" and "normal temperature" mentioned in the present invention are all calculated as 25±2°C.

[0045] The raw materials used in the following examples of the present invention are all commercially available.

[0046] Example 1

[0047] (1) Preparation of copper-based insulating fluid

[0048] A 25 mL volume of 0.4 mol / L aqueous NaOH solution was added to a 20 mL volume of 0.6 mol / L aqueous CuSO₄ solution and stirred. Then, a 40 mL volume of 0.06 mol / L aqueous ascorbic acid solution was added dropwise to the solution and stirred at 45°C for 40 min at 450 rpm. The resulting suspension was centrifuged at 2500 rpm for 20 min. The precipitate was removed and washed four times with deionized water and anhydrous ethanol. The final product was dried at 60°C for 8 h. The insulating paper sample was placed in a beaker and degassed in an oven at 65°C at a vacuum of 80 Pa for 30 h to ensure the removal of moisture from the paper. A 40 g volume of the above copper-based catalyst was then wrapped with 15 g of insulating paper to prepare an insulating paper-wrapped copper-based catalyst. 400 mL of fresh mineral oil was subjected to arc discharge for 15 h using a high-temperature and high-voltage aging test apparatus. A copper-based catalyst wrapped in insulating paper was immersed in the discharged oil sample for 24 h to prepare a copper-based insulating fluid.

[0049] (2) C2H2, H2 and C2H4 gas content test

[0050] The insulating fluid was heated at 130°C for 3 hours. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the gas content in the fluid before and after heating. The concentrations of C2H2 and H2 decreased by 8.3% and 7.9%, respectively, while the C2H4 content increased by 7.8%.

[0051] Example 2

[0052] (1) Preparation of copper-based insulating fluid

[0053] 80 mL of 1.5 mol / L aqueous NaOH solution was added to 30 mL of 2.5 mol / L aqueous CuSO₄ solution and stirred. 40 mL of 0.25 mol / L aqueous ascorbic acid solution was added dropwise to the solution and stirred at 35°C for 55 minutes at 500 rpm. The resulting suspension was centrifuged at 1500 rpm for 20 minutes. The precipitate was removed and washed three times with deionized water and anhydrous ethanol. The final product was dried at 80°C for 8 hours. The insulating paper sample was placed in a beaker and degassed in an oven at 75°C at a vacuum of 90 Pa for 55 hours to ensure the removal of moisture from the paper. A 50 g copper-based catalyst was prepared by wrapping 15 g of insulating paper around 50 g of the above copper-based catalyst. 400 mL of fresh mineral oil was subjected to arc discharge for 15 h using a high-temperature and high-voltage aging test apparatus. A copper-based catalyst wrapped in insulating paper was immersed in the discharged oil sample for 24 h to prepare a copper-based insulating fluid.

[0054] (2) C2H2, H2 and C2H4 gas content test

[0055] The insulating fluid was heated at 130°C for 3 hours. Gas-oil chromatography was used to analyze the changes in gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 34.5% and 32.8%, respectively, while the C2H4 content increased by 32.6%.

[0056] Example 3

[0057] (1) Preparation of copper-based insulating fluid

[0058] A 65 mL solution of 2 mol / L aqueous NaOH was added to a 50 mL solution of 1.5 mol / L aqueous CuSO₄ solution with stirring. A 30 mL solution of 0.3 mol / L aqueous ascorbic acid was added dropwise to the solution and stirred at 40°C for 40 min at 600 rpm. The resulting suspension was centrifuged at 2500 rpm for 10 min. The precipitate was removed and washed four times with deionized water and anhydrous ethanol. The final product was dried at 60°C for 5 h. The insulating paper sample was placed in a beaker and degassed in an oven at 70 Pa and 80°C for 45 h to ensure the removal of moisture from the paper. A 60 g copper-based catalyst was prepared by wrapping 30 g of insulating paper around 60 g of the above copper-based catalyst. 400 mL of fresh mineral oil was subjected to arc discharge for 15 h using a high-temperature and high-voltage aging test apparatus. A copper-based catalyst wrapped in insulating paper was immersed in the discharged oil sample for 24 h to prepare a copper-based insulating fluid.

[0059] (2) C2H2, H2 and C2H4 gas content test

[0060] The insulating fluid was heated at 130°C for 3 hours. Gas-oil chromatography was used to analyze the changes in gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 21.8% and 21.5%, respectively, while the C2H4 content increased by 21.4%.

[0061] Example 4

[0062] (1) Preparation of copper-based insulating fluid

[0063] A 35 mL volume of 1 mol / L aqueous NaOH solution was added to a 40 mL volume of 1.5 mol / L aqueous CuSO₄ solution and stirred. Then, a 50 mL volume of 0.1 mol / L aqueous ascorbic acid solution was added dropwise to the solution and stirred at 50°C for 30 minutes at 500 rpm. The resulting suspension was centrifuged at 2000 rpm for 15 minutes. The precipitate was removed and washed five times with deionized water and anhydrous ethanol. The final product was dried at 50°C for 10 hours. The insulating paper sample was placed in a beaker and degassed in an oven at 80°C at a vacuum of 50 Pa for 40 hours to ensure the removal of moisture from the paper. A 45 g volume of the above copper-based catalyst was wrapped with 25 g of insulating paper to prepare an insulating paper-wrapped copper-based catalyst. 400 mL of fresh mineral oil was subjected to arc discharge for 15 h using a high-temperature and high-voltage aging test apparatus. A copper-based catalyst wrapped in insulating paper was immersed in the discharged oil sample for 24 h to prepare a copper-based insulating fluid.

[0064] (2) C2H2, H2 and C2H4 gas content test

[0065] The insulating fluid was heated at 130°C for 3 hours. Gas chromatography (GC) was used to analyze the gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 13.9% and 12.6%, respectively, while the C2H4 content increased by 12.9%.

[0066] Example 5

[0067] (1) Preparation of copper-based insulating fluid

[0068] A 100 mL volume of 2 mol / L aqueous NaOH solution was added to a 50 mL volume of 3 mol / L aqueous CuSO₄ solution and stirred. A 50 mL volume of 0.1 mol / L aqueous ascorbic acid solution was added dropwise to the above solution and stirred at 40°C for 60 min at 350 rpm. The resulting suspension was centrifuged at 2500 rpm for 20 min. The precipitate was removed and washed five times with deionized water and anhydrous ethanol. The final product was dried at 60°C for 5 h. The insulating paper sample was placed in a beaker and degassed in an oven at 60°C at a vacuum of 50 Pa for 60 h to ensure the removal of moisture from the paper. A 45 g volume of the above copper-based catalyst was then wrapped with 10 g of insulating paper to prepare an insulating paper-wrapped copper-based catalyst. 400 mL of fresh mineral oil was subjected to arc discharge for 15 h using a high-temperature and high-voltage aging test apparatus. A copper-based catalyst wrapped in insulating paper was immersed in the discharged oil sample for 24 h to prepare a copper-based insulating fluid.

[0069] (2) C2H2, H2 and C2H4 gas content test

[0070] The insulating fluid was heated at 130°C for 3 hours. Gas-oil chromatography was used to analyze the gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 28.4% and 26.7%, respectively, while the C2H4 content increased by 26.6%.

[0071] Example 6

[0072] (1) Preparation of copper-based insulating fluid

[0073] A 50 mL volume of 1.5 mol / L aqueous NaOH solution was added to a 40 mL volume of 1.6 mol / L aqueous CuSO₄ solution and stirred. A 40 mL volume of 0.15 mol / L aqueous ascorbic acid solution was added dropwise to the above solution and stirred at 45°C for 40 min at 450 rpm. The resulting suspension was centrifuged at 3000 rpm for 10 min. The precipitate was removed and washed four times with deionized water and anhydrous ethanol. The final product was dried at 80°C for 6 h. The insulating paper sample was placed in a beaker and degassed in an oven at 80 Pa and 65°C for 50 h to ensure the removal of moisture from the insulating paper. A 50 g volume of the above copper-based catalyst was wrapped with 20 g of insulating paper to prepare an insulating paper-wrapped copper-based catalyst. 400 mL of fresh mineral oil was subjected to arc discharge for 15 h using a high-temperature and high-voltage aging test apparatus. A copper-based catalyst wrapped in insulating paper was immersed in the discharged oil sample for 24 h to prepare a copper-based insulating fluid.

[0074] (2) C2H2, H2 and C2H4 gas content test

[0075] The insulating fluid was heated at 130°C for 3 hours. Gas-oil chromatography was used to analyze the changes in gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 22.9% and 21.7%, respectively, while the C2H4 content increased by 21.6%.

[0076] Example 7

[0077] Same as Example 1, except that the concentration of the CuSO4 aqueous solution is adjusted to 0.05 mol / L.

[0078] The insulating fluid was heated at 130°C for 3 hours. Gas-oil chromatography was used to analyze the gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 4.3% and 3.9%, respectively, while the C2H4 content increased by 3.8%.

[0079] Example 8

[0080] Same as Example 1, except that the arc discharge time is 5 h.

[0081] The insulating fluid was heated at 130°C for 3 hours. Gas-oil chromatography was used to analyze the gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 2.3% and 2.2%, respectively, while the C2H4 content increased by 2.2%.

[0082] Comparative Example 1

[0083] (1) Same as Example 1, except that the insulating paper is directly placed in the above-mentioned discharge oil sample.

[0084] (2) C2H2, H2 and C2H4 gas content test

[0085] The insulating fluid was heated at 130°C for 3 hours. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the gas content in the insulating fluid before and after heating. No significant changes were observed in the C2H2, H2, and C2H4 contents.

[0086] Comparative Example 2

[0087] (1) Same as Example 2, except that the centrifugation step is omitted.

[0088] (2) C2H2, H2 and C2H4 gas content test

[0089] The insulating fluid was heated at 130°C for 3 hours. Gas-oil chromatography (GC-O-GC) was used to analyze the gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 17.5% and 17.4%, respectively, while the C2H4 content increased by 17.4%.

[0090] Comparative Example 3

[0091] (1) Same as Example 2, except that the insulating fluid heating temperature is 90°C.

[0092] (2) C2H2, H2 and C2H4 gas content test

[0093] The insulating fluid was heated at 90°C for 3 hours. Gas-oil chromatography was used to analyze the gas content in the insulating fluid before and after heating. The concentrations of C2H2 and H2 decreased by 1.5% and 1.4%, respectively, while the C2H4 content increased by 1.4%.

[0094] It can be seen from the above embodiments and comparative examples that the Cu-based insulating fluid of the present invention for mitigating misjudgment of transformer discharge faults has a certain catalytic conversion activity for the selective hydrogenation of dissolved acetylene, which is of great significance for identifying false alarms and missed alarms in the three-ratio method and ensuring the safe and stable operation of the transformer.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a Cu-based insulating fluid for mitigating misjudgment of transformer discharge faults, characterized in that: The following steps are involved: 1) Mixing NaOH solution and CuSO4 solution, then adding ascorbic acid aqueous solution and stirring to obtain a suspension; 2) centrifuging and washing the suspension obtained in step 1) to obtain a copper-based catalyst; 3) Wrapping the copper-based catalyst obtained in step 2) with insulating paper, and then immersing the copper-based catalyst in mineral oil after arc discharge, thereby preparing a Cu-based insulating fluid that reduces misjudgment of transformer discharge faults; The volume ratio of the NaOH solution, CuSO4 solution, and ascorbic acid aqueous solution added in step 1) is 10-150 mL:5-40 mL:20-350 mL; the concentration of the NaOH solution is 0.1-2.5 mol / L, the concentration of the CuSO4 solution is 0.1-3 mol / L, and the concentration of the ascorbic acid aqueous solution is 0.05-1 mol / L; In step 3), the ratio of the insulating paper, copper-based catalyst, and mineral oil is 10-40 g: 25-80 g: 400 mL; The insulating paper in step 3) needs to be vacuum degassed before use, wherein the vacuum degree is 20-150 Pa, the temperature is 50-120°C, and the time is 24-72 hours; The arc discharge time of the mineral oil is 15 hours; The immersion time is 15 to 30 hours.

2. The method for preparing a Cu-based insulating fluid for mitigating misjudgment of transformer discharge faults according to claim 1, characterized in that: The stirring is performed at 25-65° C., with a stirring speed of 200-800 r / min and a stirring time of 10-120 min.

3. The method for preparing a Cu-based insulating fluid for mitigating misjudgment of transformer discharge faults according to claim 1, characterized in that: The centrifugation time in step 2) is 10-30 min, and the centrifugation speed is 1000-4000 r / min; the detergents used in the washing are deionized water and anhydrous ethanol, and the number of washing times is 2-8 times.

4. The method for preparing a Cu-based insulating fluid for mitigating misjudgment of transformer discharge faults according to claim 1, characterized in that: After the washing is completed, a drying step is required. The drying time is 3 to 15 hours and the drying temperature is 40 to 120°C.

5. A Cu-based insulating fluid for mitigating misjudgment of transformer discharge faults, prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the Cu-based insulating fluid for mitigating misjudgment of transformer discharge faults as claimed in claim 5 in the field of early warning of dissolved gas faults in transformer oil.