Method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas and metal in equipment

Abstract

The invention relates to a method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas and metal in equipment. The method comprises the following steps of gas thermal stability test, metal interface compatibility test and equipment optimization. The gas thermal stability test comprises the steps of gas storage tank pretreatment, ternary mixed gas feeding, test process control, reaction gas sampling and treatment analysis; the metal interface compatibility test comprises the steps of test platform building, ternary mixed gas inflation and tank entering, test control and test result analysis. The equipment optimization is to optimize and improve according to the proportion of the ternary mixed gas obtained in the gas thermal stability test and the metal obtained in the metal interface compatibility test. The optimization method for effectively improving the compatibility of the C4F7N / CO2 / O2 ternary mixed gas and the metal is provided, and corresponding optimization method choices are provided for electrical equipment under different use conditions, so that the safety and reliability of the equipment are enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of insulating gas detection in electrical engineering, and in particular to a method for optimizing the compatibility of a C4F7N / CO2 / O2 ternary mixed gas with metals in equipment. Background Art

[0002] With the widespread application of high-voltage equipment, gas insulation technology has gradually become an important part of electrical equipment. Among them, C4F7N / CO2 / O2 ternary mixed gas has attracted attention due to its excellent insulation performance and low environmental impact. However, the compatibility problem between the gas and the metal materials inside the equipment (such as aluminum, copper, stainless steel, etc.) has become increasingly prominent, which may lead to corrosion, failure and safety hazards of the equipment.

[0003] In the prior art, the research on the compatibility of gas and metal mainly focuses on the optimization of gas composition and surface treatment technology. However, the method for improving the compatibility of C4F7N / CO2 / O2 mixed gas is still insufficient. Especially in practical applications, how to effectively reduce the chemical reactivity of gas and metal materials and extend the service life of equipment is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies in the prior art, thereby providing a method for optimizing the compatibility of a C4F7N / CO2 / O2 ternary mixed gas with metals in equipment.

[0005] To achieve the above objectives, the specific technical scheme is as follows: A method for optimizing the compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment, comprising the following steps: gas thermal stability test, metal interface compatibility test and equipment optimization; The gas thermal stability test includes: gas tank pretreatment, ternary mixed gas entering the tank, test process control, reaction gas sampling and processing analysis; The mixed gas is introduced into the tank by sequentially introducing C4F7N, O2 and CO2 into the gas chamber according to Dalton's law of partial pressure, and the volume fraction ratio of C4F7N:O2:CO2 is 15%:0%~10%:85%~75%; The test process control is temperature and humidity controlled heating process control. The temperature control system is used to stabilize the experimental temperature at 500°C before starting the heating experiment and continuing heating for 12 hours, keeping the ambient temperature and humidity unchanged. The processing and analysis includes: analyzing and recording the properties of the products before and after the test, changing the O2 oxygen content of the mixed gas, repeating the above gas thermal stability test process, comparing the amount and change trend of corrosive products under different O2 ratios, and obtaining the ratio of the ternary mixed gas with good compatibility with the metal; The metal interface compatibility test includes: test platform construction, filling the tank with ternary mixed gas, test control, and test result analysis; The test platform construction includes: using a temperature control box to control the temperature, using a metal sleeve to simulate the current-carrying busbar in the gas-insulated equipment, the metal sleeve is embedded with a K-type thermocouple, and the temperature control box is connected to the K-type thermocouple through a line to monitor the actual temperature of the metal sleeve surface; The test control is to carry out three groups of 40h constant temperature heating process control tests at three metal interface temperature points of 120℃, 170℃ and 220℃; The test result analysis includes: analyzing the morphology of the metal sleeve and the gas condition in the temperature control box after the test, changing different types of metal sleeves, repeating the above metal interface compatibility test process, comparing the morphology of the metal sleeve and the gas condition in the temperature control box under different types of metals, and obtaining the corresponding metal with good compatibility with the filled ternary mixed gas; The equipment optimization is optimized and improved based on the ratio of the ternary mixed gas obtained from the gas thermal stability test and the metal obtained from the metal interface compatibility test.

[0006] Before the experiment, use anhydrous ethanol to wipe the surface of the tank, sealing cover and heating element.

[0007] The gas tank pretreatment includes: using 99% pure CO2 gas to flush into the tank until the gas pressure reaches 0.1MPa, leaving it to stand for 30 minutes, vacuuming again and leaving it to stand for a period of time, repeating the above process 3-4 times to fully discharge impurities and residual air, moisture, etc. that may exist in the tank.

[0008] The reaction gas sampling is to collect the experimental gas using a PVF sampling bag every 2 hours during the experiment; The processing and analysis is performed using a gas chromatography-mass spectrometer GC-MS for detection and analysis, and pure helium is introduced into the gas chromatography-mass spectrometer GC-MS before measurement to eliminate the influence of impurities brought by the previous measurement process.

[0009] Three groups of 40h constant temperature heating process control tests were conducted. The metal sleeve was replaced before each test to avoid the influence of the previous group of tests.

[0010] The filling of the ternary mixed gas into the tank includes: filling a mixed gas with a volume fraction ratio of 15% C4F7N, 4% O2, and 81% CO2.

[0011] The morphology of the metal casing after the test is analyzed, specifically: If there is no obvious difference between the metal sleeve and the untreated sample, it means that the metal has not been corroded and the C4F7N / CO2 / O2 ternary mixture gas has good compatibility with the metal; if there is a significant difference between the metal sleeve and the untreated sample and the color distribution is uneven, it means that the metal has been corroded and the C4F7N / CO2 / O2 ternary mixture gas has poor compatibility with the metal.

[0012] After the test, the gas conditions in the temperature control box are analyzed, specifically: At the same time, the gas collected in the temperature control box is analyzed by gas chromatography-mass spectrometry. The compatibility of C4F7N / CO2 / O2 with the metal is judged according to the appearance temperature and characteristic peak area of ​​the characteristic decomposition products of C4F7N / CO2 / O2. If the appearance temperature of the decomposition characteristic products is high and the characteristic peak area is low, it means that the compatibility with the metal is good, otherwise it means that the compatibility with the metal is poor.

[0013] The optimization and improvement are carried out according to the ratio of the ternary mixed gas obtained from the gas thermal stability test and the metal obtained from the metal interface compatibility test, specifically: For electrical equipment that has not been used yet, before it is put into production, the metal parts that need to be frequently closed are treated with surface electroplating using metals with good compatibility with the ternary mixed gas selected by the metal interface compatibility test. At the same time, the ratio of the ternary mixed gas in the insulating gas chamber is adjusted to the ratio of the ternary mixed gas with good compatibility with the metal selected by the gas thermal stability test, so as to increase the service life of the electrical equipment; For electrical equipment that has been put into use, when there is no need to adjust the gas in the gas chamber, during maintenance, the corroded parts or key parts of the electrical equipment can be surface electroplated with metals that are compatible with the ternary mixed gas selected through the metal interface compatibility test to increase the service life. For equipment that needs to replenish the gas chamber gas, the service life can be increased by adjusting the ratio of the ternary mixed gas in the insulating gas chamber to the ratio of the ternary mixed gas that has good compatibility with the metal selected through the gas thermal stability test.

[0014] The present invention conducts an in-depth study on the compatibility of C4F7N / CO2 / O2 ternary mixed gas under different oxygen ratios and metal materials, revealing the influence of oxygen ratio and metal materials on the compatibility of the mixed gas. The study determines the optimal ratio of oxygen in the C4F7N / CO2 / O2 ternary mixed gas, as well as the metal materials that show good compatibility with the mixed gas. This study aims to improve the compatibility of gas and metal materials, enhance the safety and reliability of equipment in high voltage environments, and effectively extend its service life.

[0015] The present invention studies the compatibility of C4F7N / CO2 / O2 ternary mixed gas under different oxygen ratios and different metal materials, determines the optimal ratio of oxygen in the C4F7N / CO2 / O2 ternary mixed gas, and the metal materials showing good compatibility with the mixed gas, proposes a variety of optimization methods for effectively improving the compatibility of the C4F7N / CO2 / O2 ternary mixed gas and metals, and provides corresponding optimization method selections for electrical equipment in different usage situations, thereby enhancing the safety and reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Optimize the compatibility of electrical equipment under different usage conditions; Figure 2 It is a thermal stability test platform; Figure 3 It is a metal interface compatibility testing platform; Figure 4 The experimental flow chart is shown in Figure 2. DETAILED DESCRIPTION

[0017] The following examples are combined with Figure 1-4 The technical solution of this method is further specifically described.

[0018] Build a C4F7N / CO2 / O2 ternary mixed gas and thermal stability test platform Figure 2 , and metal interface compatibility test platforms, such as Figure 3 The experimental platform is as follows Figure 2~3 shown.

[0019] like Figure 4 , Gas thermal stability test: Before the experiment begins, use anhydrous ethanol to wipe the surface of the tank, sealing cover and heating element, mainly to wipe the product and moisture residue after the previous experiment is completed, so as to avoid the interference of impurities on the next experiment.

[0020] Use 99% pure CO2 gas to flush the tank until the pressure reaches 0.1MPa, then let it stand for 30 minutes, evacuate again and let it stand for a while. Repeat the whole process 3-4 times to fully discharge the impurities and air, moisture and other residues that may exist in the tank. According to Dalton's law of partial pressure, C4F7N, O2 and CO2 are introduced into the gas chamber in turn. First, 15% C4F7N gas is slowly introduced into the tank, and then different contents of O2 and CO2 are filled in. The content of O2 filled is 0%~10%, and the content of CO2 filled is 85%~75%.

[0021] Connect the experimental circuit, use the temperature control system to stabilize the experimental temperature at 500℃, then start the heating experiment and continue heating for 12 hours, keeping the ambient temperature and humidity unchanged.

[0022] During the experiment, PVF sampling bags were used to collect experimental gas samples for detection every 2 hours, and pure helium was introduced into the gas chromatography-mass spectrometry (GC-MS) before measurement to eliminate the influence of impurities brought by the previous measurement process. Then the sample gas of this experiment was introduced into the GC-MS for detection and analysis.

[0023] By analyzing the generation and change trend of each product, we can determine the relationship between the O2 ratio and the compatibility of the C4F7N / CO2 / O2 ternary mixed gas and metals. We can change the O2 oxygen content of the mixed gas, repeat the above gas thermal stability test process, and compare the number of corrosive products and their change trends under different O2 ratios. If the number of corrosive products generated is less and the change trend is smaller, then the C4F7N / CO2 / O2 ternary mixed gas under the O2 ratio has good compatibility with metals. After processing the experimental data, we give an optimization method, that is, when the C4F7N content in the gas insulation medium used for medium-voltage gas-insulated equipment is 15%, the optimal O2 addition amount is 4%-6%, which can ensure the insulation strength while improving the service life of electrical equipment.

[0024] Metal interface compatibility test: The temperature control box method is adopted. A metal sheath (copper or aluminum) is used to simulate the current-carrying busbar in the gas-insulated equipment and serve as the interaction interface in the gas-solid interface stability test. A K-type thermocouple is embedded in the metal sheath as a heat source, and the temperature sensor is used to monitor the actual temperature of the metal sheath surface.

[0025] Different metals were selected to carry out gas-solid interface compatibility tests for 40 hours at three metal interface temperature points: 120°C, 170°C and 220°C. The metal sleeve was replaced before the test to avoid the influence of the previous set of tests.

[0026] After the test, the morphology of the metal casing was analyzed and the indoor gas was collected for GC-MS analysis.

[0027] If there is no obvious difference between the metal sleeve and the untreated sample, it means that the metal has not been corroded and the C4F7N / CO2 / O2 ternary mixture gas has good compatibility with the metal; if there is a significant difference between the metal sleeve and the untreated sample and the color distribution is uneven, it means that the metal has been corroded and the C4F7N / CO2 / O2 ternary mixture gas has poor compatibility with the metal.

[0028] At the same time, the indoor gas is analyzed by gas chromatography-mass spectrometry. The compatibility of C4F7N / CO2 / O2 with the metal is judged according to the appearance temperature and characteristic peak area of ​​the characteristic decomposition products of C4F7N / CO2 / O2. If the appearance temperature of the decomposition characteristic products is high and the characteristic peak area is low, it means that the compatibility with the metal is good, otherwise it means that the compatibility with the metal is poor. Through experimental comparison, the experimental results of copper, silver and aluminum are obtained. It is found that the gas-solid interface compatibility of the mixed gas with aluminum and silver is good, and the interaction process will not cause metal corrosion. Therefore, the second optimization method is proposed to use silver plating treatment on key parts of electrical equipment to reduce corrosion of key parts and increase the service life of equipment.

[0029] Combining the conclusions drawn from the two embodiments, we propose the following Figure 1 The compatibility optimization schemes for electrical equipment under different usage conditions shown in the figure are: first, changing the O2 content in the ternary mixed gas to 4~6%, and second, silver-plating key metal parts to increase the service life of electrical equipment. For electrical equipment that has not yet been used, we can silver-plate metal parts that need to be frequently closed before production, and adjust the O2 ratio of the ternary mixed gas in the insulating gas chamber to 4~6% to increase the service life of electrical equipment. For electrical equipment that has been put into use, if the gas in the gas chamber does not need to be adjusted, we can silver-plate the corroded parts or key parts of the electrical equipment during maintenance to increase the service life. For equipment that needs to supplement the gas in the gas chamber, we can adjust the O2 ratio in the ternary mixed gas to 4~6% to increase the service life.

Claims

1. A method for optimizing the compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment, characterized in that: The following steps are involved: Gas thermal stability test, metal interface compatibility test and equipment optimization; The gas thermal stability test includes: gas tank pretreatment, ternary mixed gas entering the tank, test process control, reaction gas sampling and processing analysis; The mixed gas is introduced into the tank by sequentially introducing C4F7N, O2 and CO2 into the gas chamber according to Dalton's law of partial pressure, and the volume fraction ratio of C4F7N:O2:CO2 is 15%:0%~10%:85%~75%; The test process control is temperature and humidity controlled heating process control. The temperature control system is used to stabilize the experimental temperature at 500°C before starting the heating experiment and continuing heating for 12 hours, keeping the ambient temperature and humidity unchanged. The processing and analysis includes: analyzing and recording the properties of the products before and after the test, changing the O2 oxygen content of the mixed gas, repeating the above gas thermal stability test process, comparing the amount and change trend of corrosive products under different O2 ratios, and obtaining the ratio of the ternary mixed gas with good compatibility with the metal; The metal interface compatibility test includes: test platform construction, filling the tank with ternary mixed gas, test control, and test result analysis; The test platform construction includes: using a temperature control box to control the temperature, using a metal sleeve to simulate the current-carrying busbar in the gas-insulated equipment, the metal sleeve is embedded with a K-type thermocouple, and the temperature control box is connected to the K-type thermocouple through a line to monitor the actual temperature of the metal sleeve surface; The test control is to carry out three groups of 40h constant temperature heating process control tests at three metal interface temperature points of 120℃, 170℃ and 220℃; The test result analysis includes: analyzing the morphology of the metal sleeve and the gas condition in the temperature control box after the test, changing different types of metal sleeves, repeating the above metal interface compatibility test process, comparing the morphology of the metal sleeve and the gas condition in the temperature control box under different types of metals, and obtaining the corresponding metal with good compatibility with the filled ternary mixed gas; The equipment optimization is optimized and improved based on the ratio of the ternary mixed gas obtained from the gas thermal stability test and the metal obtained from the metal interface compatibility test.

2. The method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment according to claim 1, characterized in that: Before the experiment, use anhydrous ethanol to wipe the surface of the tank, sealing cover and heating element.

3. The method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment according to claim 1, characterized in that: The gas tank pretreatment includes: using 99% pure CO2 gas to flush into the tank until the gas pressure reaches 0.1MPa, leaving it to stand for 30 minutes, vacuuming again and leaving it to stand for a period of time, repeating the above process 3-4 times to fully discharge impurities and residual air, moisture, etc. that may exist in the tank.

4. The method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment according to claim 1, characterized in that: The reaction gas sampling is to collect the experimental sample gas every 2 hours using a PVF sampling bag during the experiment; The processing and analysis is performed using a gas chromatography-mass spectrometer GC-MS for detection and analysis, and pure helium is introduced into the gas chromatography-mass spectrometer GC-MS before measurement to eliminate the influence of impurities brought by the previous measurement process.

5. The method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment according to claim 1, characterized in that: Three groups of 40h constant temperature heating process control tests were conducted. The metal sleeve was replaced before each test to avoid the influence of the previous group of tests.

6. The method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment according to claim 1, characterized in that: The filling of the ternary mixed gas into the tank includes: filling a mixed gas with a volume fraction ratio of 15% C4F7N, 4% O2, and 81% CO2.

7. The method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment according to claim 1, characterized in that: The morphology of the metal casing after the test is analyzed, specifically: If there is no obvious difference between the metal sleeve and the untreated sample, it means that the metal has not been corroded and the C4F7N / CO2 / O2 ternary mixture gas has good compatibility with the metal; if there is a significant difference between the metal sleeve and the untreated sample and the color distribution is uneven, it means that the metal has been corroded and the C4F7N / CO2 / O2 ternary mixture gas has poor compatibility with the metal.

8. The method for optimizing compatibility of C4F7N / CO2 / O2 ternary mixed gas with metals in equipment according to claim 1, characterized in that: After the test, the gas conditions in the temperature control box are analyzed, specifically: At the same time, the gas collected in the temperature control box is analyzed by gas chromatography-mass spectrometry. The compatibility of C4F7N / CO2 / O2 with the metal is judged according to the appearance temperature and characteristic peak area of ​​the characteristic decomposition products of C4F7N / CO2 / O2. If the appearance temperature of the decomposition characteristic products is high and the characteristic peak area is low, it means that the compatibility with the metal is good, otherwise it means that the compatibility with the metal is poor.

9. The method for optimizing compatibility between C4F7N / CO2 / O2 ternary mixed gas and metals in equipment according to claim 1, characterized in that: The optimization and improvement are carried out according to the ratio of the ternary mixed gas obtained from the gas thermal stability test and the metal obtained from the metal interface compatibility test, specifically: For electrical equipment that has not been used yet, before it is put into production, the metal parts that need to be frequently closed are treated with surface electroplating using metals with good compatibility with the ternary mixed gas selected by the metal interface compatibility test. At the same time, the ratio of the ternary mixed gas in the insulating gas chamber is adjusted to the ratio of the ternary mixed gas with good compatibility with the metal selected by the gas thermal stability test, so as to increase the service life of the electrical equipment; For electrical equipment that has been put into use, when there is no need to adjust the gas in the gas chamber, during maintenance, the corroded parts or key parts of the electrical equipment can be surface electroplated with metals that are compatible with the ternary mixed gas selected through the metal interface compatibility test to increase the service life. For equipment that needs to replenish the gas chamber gas, the service life can be increased by adjusting the ratio of the ternary mixed gas in the insulating gas chamber to the ratio of the ternary mixed gas that has good compatibility with the metal selected through the gas thermal stability test.

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