Method for detecting characteristic decomposition product N2O of mixed gas in electrical equipment

Abstract

The invention discloses a method for detecting a characteristic decomposition product N2O of mixed gas in electrical equipment, which comprises the following steps of: setting a target Fourier transform output wavelength of a Fourier infrared spectrometer by determining an infrared absorption wavelength corresponding to the characteristic decomposition product N2O of SF6 / N2 mixed gas when a local overheating problem occurs; by setting the output wavelength of the Fourier infrared spectrometer, the Fourier infrared spectrometer is used for detecting the characteristic decomposition product N2O gas when the SF6 / N2 mixed gas in the power equipment has the local overheating defect, so that field staff can conveniently and quickly detect the concentration of the N2O gas.

Description

Technical Field

[0001] The present invention relates to the technical field of SF6 / N2 mixed gas electrical equipment fault detection, and in particular to a method for detecting N2O, a characteristic decomposition product of the mixed gas in electrical equipment. Background Art

[0002] SF6 gas is the most widely used insulating gas in power equipment due to its excellent insulation and arc-extinguishing capabilities. However, due to its extremely high GWP (global warming potential), SF6 is listed as one of the six greenhouse gases whose emissions are prohibited in the Kyoto Protocol. N2 has the advantages of low environmental pollution, low price, and stable chemical properties. In recent years, N2 and SF6 mixed gas has been widely used as a gas insulation medium in power equipment.

[0003] However, SF6 / N2 mixed gas electrical equipment typically has numerous joints. Due to manufacturing process issues, these joints may exhibit defects such as detachment, uneven coating, or surface oxidation. These issues can reduce the effective contact area of the joints or lead to poor contact, which in turn causes excessive circuit contact resistance, leading to localized overheating, affecting the safe operation of the equipment and even threatening the safe operation of the power grid. The inventors discovered that when localized overheating occurs, the SF6 / N2 mixed gas decomposes to produce characteristic decomposition products, and they have come up with the idea of using these characteristic decomposition products to determine whether localized overheating has occurred in electrical equipment.

[0004] Therefore, how to detect characteristic decomposition products simply and quickly has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] An embodiment of the present application provides a method for detecting N2O, a characteristic decomposition product of a mixed gas in electrical equipment. The method determines the infrared absorption wavelength corresponding to N2O, a characteristic decomposition product of the SF6 / N2 mixed gas when a local overheating problem occurs, sets a target Fourier transform output wavelength of a Fourier transform infrared spectrometer, and uses the Fourier transform infrared spectrometer to detect N2O gas, a characteristic decomposition product of the SF6 / N2 mixed gas when a local overheating defect occurs in the electrical equipment, by setting the output wavelength of the Fourier transform infrared spectrometer. This allows on-site staff to quickly and conveniently detect the concentration of N2O gas.

[0006] The present invention provides a method for detecting N2O, a characteristic decomposition product of mixed gas in electrical equipment, comprising: determining a target Fourier transform output wavelength corresponding to a characteristic decomposition product of the SF6 / N2 mixed gas under an overheat defect condition, wherein the characteristic decomposition product is N2O gas; At a work site, the concentration of N2O gas in the SF6 / N2 mixed gas in the power equipment is detected using a Fourier transform infrared spectrometer set with the target Fourier transform output wavelength.

[0007] In some embodiments, the method further comprises: The detected SF6 / N2 mixed gas is transported to a gas recovery device, so that the gas recovery device purifies and stores the detected SF6 / N2 mixed gas.

[0008] In some embodiments, the step of purifying and storing the detected SF6 / N2 mixed gas includes: Purifying and filtering the detected SF6 / N2 mixed gas through a purification filter device to obtain purified and filtered gas; drying the purified and filtered gas through a drying and purification device to obtain dried gas; The dried gas is compressed and cooled, and then stored in a gas storage cylinder.

[0009] In some embodiments, before the step of storing the gas in the gas storage cylinder, the method further comprises: extracting the gas in the gas storage cylinder using a vacuum pump.

[0010] In some embodiments, the decomposition products of the SF6 / N2 mixed gas under the overheating defect condition include CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2; and the step of determining the target Fourier transform output wavelength corresponding to N2O gas in the characteristic decomposition products of the SF6 / N2 mixed gas under the overheating defect condition includes: Determine the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2 respectively; The Fourier transform output wavelength corresponding to N2O is screened out to be different from the Fourier transform output wavelength corresponding to CS2, COS, H2S, SO2, SOF2, CO2 and SO2F2, and is used as the target Fourier transform output wavelength corresponding to N2O gas.

[0011] In some embodiments, the step of determining the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2, respectively, comprises: Look up the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2 from the NIST database.

[0012] In some embodiments, gas chromatography-mass spectrometry is used to determine that decomposition products of the SF6 / N2 mixed gas under overheating defect conditions include CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2.

[0013] In some embodiments, the gas chromatograph-mass spectrometer uses 99.9995% pure helium as a carrier gas, and the column oven control program in the gas chromatograph in the gas chromatograph-mass spectrometer includes stabilizing the temperature at 40°C within 0 to 7 minutes; heating to 220°C at a rate of 15°C per minute, and maintaining at 220°C for 2 minutes; the gas chromatograph parameters of the gas chromatograph are set as: total flow rate of 111.5 mL / min, split ratio of 30:1, inlet temperature of 200°C, pressure of 167.6 kPa, maximum column temperature of 300°C, column flow rate of 3.5 mL / min, linear velocity of 47.7 cm / s, and purge flow rate of 3.0 mL / min.

[0014] In some embodiments, the parameters of the mass spectrometer in the gas chromatograph-mass spectrometer are set as follows: the gas chromatograph and mass spectrometer interface temperature is 220°C, the solvent delay time is 0 minute, the scanning interval is 0.3s, the micro-scan width is 0u, the detector voltage is 0.1kV, the ion source is an electron ionization source, and the ion source temperature is 200°C; the detector uses an isolated dynode electron multiplier.

[0015] In some embodiments, the method further comprises: determining the extent of the overheating defect based on the concentration of the N2O gas; The step of determining the degree of overheating defect according to the concentration of the N2O gas includes: If it is higher than 0 and lower than 0.5 ppm, the degree of the overheating defect is determined to be a mild overheating defect; If it is not less than 0.5 ppm, determine whether the concentration of the N2O gas is higher than 1.5 ppm; If it is not higher than 1.5 ppm, the degree of the overheating defect is determined to be a normal overheating defect; if it is higher than 1.5 ppm, the degree of the overheating defect is determined to be a severe overheating defect.

[0016] In some embodiments, the method further comprises: generating decomposition products of the SF6 / N2 mixed gas under an overheat defect condition using a local overheat simulation device; The local overheating simulation device includes: a shell, an air inlet pipe, an air outlet pipe, a vacuum pump, a pressure gauge, a heating rod, a temperature control distribution box and a power supply; The air inlet pipe and the air outlet pipe are respectively communicated with the interior of the housing, the pressure gauge is arranged on the air inlet pipe, and the vacuum pump is arranged on the air outlet pipe; The heating rod is located inside the shell to provide heat energy to the inside of the shell, and the heating rod is connected to the power supply through the temperature control distribution box; A cover plate is movably provided on the upper end of the shell.

[0017] In some embodiments, the step of generating decomposition products of the SF6 / N2 mixed gas under an overheating defect condition using a local overheating simulation device includes: Presetting N preset strategies, and using the first of the N preset strategies as the target strategy, wherein the preset strategy includes a heating temperature and a preset heating time when the heating rod is heating; The SF6 / N2 mixed gas is introduced into the housing through an air intake pipe to a preset pressure, and a heating rod in the local overheating simulation device is controlled to heat under the target strategy, and decomposition products of the SF6 / N2 mixed gas are detected when heated under the target strategy; Determine the kth preset strategy as the target strategy, repeat the steps of inputting the SF6 / N2 mixed gas into the local overheating simulation device to a preset gas pressure, controlling the heating rod in the local overheating simulation device to heat under the target strategy, and detecting the decomposition products of the SF6 / N2 mixed gas when heated under the target strategy, wherein k is a positive integer between 2 and N.

[0018] In some embodiments, the method further comprises: screening out characteristic decomposition products from the decomposition products.

[0019] In some embodiments, before the step of inputting the SF6 / N2 mixed gas into the housing through the air inlet pipe to a preset pressure, the method further includes: Filling high-purity N2 to clean the interior of the local overheating simulation device, repeating several times; The interior of the local overheating simulation device was evacuated.

[0020] In some embodiments, before the step of controlling the heating rod in the local overheating simulation device to heat under the target strategy, the method further includes: The local overheating simulation device filled with the SF6 / N2 mixed gas is left to stand for several hours; before and after standing still, the internal pressure of the local overheating simulation device is determined using the pressure gauge in the local overheating simulation device; based on the internal pressure before and after standing still, it is judged whether the interior of the local overheating simulation device is airtight; if the airtightness is good, the step of controlling the heating rod in the local overheating simulation device to heat under the target strategy is executed.

[0021] The present invention provides a method for detecting N2O, a characteristic decomposition product of mixed gas in electrical equipment. The method determines the infrared absorption wavelength corresponding to N2O, a characteristic decomposition product of the SF6 / N2 mixed gas when a local overheating problem occurs, sets a target Fourier transform output wavelength of a Fourier transform infrared spectrometer, and uses the Fourier transform infrared spectrometer to detect N2O, a characteristic decomposition product of the SF6 / N2 mixed gas when a local overheating defect occurs in the electrical equipment. This method allows on-site staff to quickly and conveniently detect the concentration of N2O gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart illustrating a method for detecting N2O, a characteristic decomposition product of mixed gas in electrical equipment, according to some embodiments is exemplified; Figure 2 The following is a schematic structural diagram of a local overheating simulation device provided according to some embodiments; Figure 3 A histogram showing the variation of the concentration of N2O generated as a characteristic decomposition product with temperature and time according to some embodiments is shown as an example; Figure 4 Schematic diagram of the absorption wavelength of SO2 infrared spectrum; Figure 5 Schematic diagram of CO2 infrared spectrum absorption wavelength; Figure 6 Schematic diagram of N2O infrared spectrum absorption wavelength; Figure 7 Schematic diagram of wavelength setting and detection results when using Fourier transform infrared spectrometer to detect characteristic decomposition product N2O standard gas; Figure 8 Schematic diagram of the full wavelength band of N2O gas and the detection results in the Fourier infrared spectrometer; Figure 9 This is a schematic diagram of the full wavelength range of the Fourier transform infrared spectrometer and the detection results of CO2, SO2, and N2O mixed gases. DETAILED DESCRIPTION

[0023] In order to better understand the above technical solution, the technical solution of this application is described in detail below through specific implementation methods.

[0024] In order to solve the above technical problems, an embodiment of the present application provides a method for detecting N2O, a characteristic decomposition product of mixed gas in electrical equipment. The method determines the infrared absorption wavelength corresponding to N2O, a characteristic decomposition product of the SF6 / N2 mixed gas when a local overheating problem occurs, sets the target Fourier transform output wavelength of a Fourier transform infrared spectrometer, and uses the Fourier transform infrared spectrometer to detect N2O gas, a characteristic decomposition product of the SF6 / N2 mixed gas in the power equipment when a local overheating defect occurs, by setting the output wavelength of the Fourier transform infrared spectrometer. This facilitates on-site staff to quickly and conveniently detect the concentration of N2O gas. Figure 1 A flow chart of a method for detecting N2O, a characteristic decomposition product of mixed gas in electrical equipment according to some embodiments is exemplified, the method comprising S100-S200.

[0025] S100: Determine a target Fourier transform output wavelength corresponding to a characteristic decomposition product of the SF6 / N2 mixed gas under an overheating defect condition, where the characteristic decomposition product is N2O gas.

[0026] In the embodiments of the present application, a localized overheating simulation device is used to simulate an overheating defect (i.e., a localized overheating problem) in power equipment, and the decomposition products of the SF6 / N2 gas mixture under the overheating defect are determined. Characteristic decomposition products are then screened from the decomposition products. Specifically, the localized overheating simulation device is used to generate decomposition products of the SF6 / N2 gas mixture under the overheating defect condition.

[0027] The structure of the local overheating simulation device is introduced below.

[0028] In some embodiments, Figure 2 The following is a schematic diagram illustrating the structure of a local overheating simulation device according to some embodiments. The local overheating simulation device includes a housing 1, an air inlet pipe 2, an air outlet pipe 3, a vacuum pump 4, a pressure gauge 5, a heating rod 6, a temperature control distribution box 7, and a power supply 8.

[0029] The air inlet pipe and the air outlet pipe are respectively communicated with the interior of the shell, the pressure gauge is arranged on the air inlet pipe, and the vacuum pump is arranged on the air outlet pipe.

[0030] In some embodiments, the air inlet pipe and the air outlet pipe are arranged on the same side of the shell, and the SF6 / N2 mixed gas enters the shell from the air inlet pipe and is discharged from the shell from the air outlet pipe.

[0031] The pressure gauge is used to measure the gas pressure in the housing. The vacuum pump can extract gas from the interior of the housing to make the interior of the housing present a vacuum state.

[0032] The heating rod is located inside the shell and provides heat energy to the inside of the shell. The heating rod is connected to the power supply through the temperature control distribution box. In the embodiment of the present application, the power supply provides electrical energy to the heating rod through the temperature control distribution box and the power cord 9. In addition, the temperature control distribution box is also connected to the heating rod through a temperature measuring line 10. The temperature measuring line is used to detect the temperature of the heating rod and transmit the temperature signal to the temperature control distribution box. The temperature control distribution box further controls the power supply to the heating rod through the obtained temperature signal to adjust the temperature of the heating rod. The temperature control distribution box can display the real-time temperature and set temperature inside the shell. When the real-time temperature does not reach the set temperature, it controls the heating rod to increase the heating temperature.

[0033] The upper end of the shell is movably provided with a cover plate, and the cover plate is movably provided on the upper end of the shell. The cover plate can be removed from the upper end of the shell as needed, and can also be covered on the upper end of the shell.

[0034] In this embodiment, a SF6 / N2 mixed gas is introduced into the housing through an air inlet pipe, the heating temperature of the heating rod is controlled, and samples are taken through an air outlet pipe at preset intervals. The sampled gas is then tested using a gas chromatograph-mass spectrometer. For example, the gas chromatograph-mass spectrometer may be a Shimadzu GCMS-QP2020 NX model.

[0035] In the embodiment of the present application, gas chromatography-mass spectrometry is used to determine that the decomposition products of the SF6 / N2 mixed gas under overheating defect conditions include CS2, COS, H2S, SO2, N2O, SOF2, CO2 and SO2F2.

[0036] In some embodiments, the gas chromatograph-mass spectrometer uses 99.9995% pure helium as a carrier gas, and the column oven control program in the gas chromatograph in the gas chromatograph-mass spectrometer includes stabilizing the temperature at 40°C within 0 to 7 minutes; increasing the temperature to 220°C at a rate of 15°C per minute, and maintaining at 220°C for 2 minutes; the entire program time is 21 minutes.

[0037] The gas chromatograph parameters were set as follows: total flow rate of 111.5 mL / min, split ratio of 30:1, inlet temperature of 200°C, pressure of 167.6 kPa, maximum column temperature of 300°C, column flow rate of 3.5 mL / min, linear velocity of 47.7 cm / s, and purge flow rate of 3.0 mL / min. The details are shown in Table 1. For example, the column model is a CP-Sil 5 CB column.

[0038] Table 1

[0039] In some embodiments, the parameters of the mass spectrometer in the gas chromatography-mass spectrometry instrument are set as follows: the gas chromatography-mass spectrometry interface temperature is 220°C, the solvent delay time is 0 minutes, the scan interval is 0.3 seconds, the micro-scan width is 0u, the detector voltage is 0.1kV, the ion source is an electron ionization source, and the ion source temperature is 200°C. For details, see Table 2. The detector uses an isolated dynode electron multiplier. The mass analyzer in the mass spectrometer is composed of a quadrupole rod with a length of approximately 20 cm, which can effectively separate ions according to their mass-to-charge ratio. The mass spectrometer can effectively separate various decomposition products such as CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2 in SF6 / N2 mixed gas.

[0040] Table 2

[0041] After building a local overheating simulation device, the local overheating simulation device was used to determine the characteristic decomposition products for identifying local overheating defects in SF6 / N2 mixed gas electrical equipment.

[0042] Specifically, the step of determining characteristic decomposition products for identifying local overheating defects of SF6 / N2 mixed gas electrical equipment by the local overheating simulation device includes S101-S104.

[0043] S101 , pre-setting N preset strategies, and taking the first of the N preset strategies as the target strategy, wherein the preset strategy includes a heating temperature and a preset heating time when the heating rod is heating.

[0044] For example, the N preset strategies may include 11 preset strategies, wherein the first ten preset strategies have a heating temperature of 200° C., the next preset strategy has a heating temperature 25° C. higher than the previous preset strategy, and the eleventh preset strategy has a heating temperature of 450° C. The preset duration in each preset strategy is 10 hours.

[0045] S102. Input the SF6 / N2 mixed gas into the shell through the air intake pipe to a preset air pressure, control the heating rod in the local overheating simulation device to heat under the target strategy, and detect the decomposition products of the SF6 / N2 mixed gas when heated under the target strategy.

[0046] In the embodiments of the present application, in order to ensure the accuracy of the experimental results, that is, to determine the characteristic decomposition products, the temperature and humidity of the laboratory where the local overheating simulation device is located are controlled during the experiment so that the temperature and humidity are roughly the same as the environment at the work site, and are exemplarily maintained at 20±2°C and 50±3% relative humidity.

[0047] In the embodiments of the present application, it was found through investigation that the operating pressure of the SF6 / N2 mixed gas equipment in the pilot operation is 0.6 MPa, and the mixing ratio of SF6 and N2 in the SF6 / N2 mixed gas is 3:7. Therefore, in order to be more similar to the actual scene at the work site, in this step, SF6 / N2 mixed gas with a mixing ratio of SF6 and N2 of 3:7 is filled into the local overheating simulation device, so that the air pressure in the shell is 0.6 MPa, that is, the preset air pressure is 0.6 MPa.

[0048] In one example, the decomposition product may be collected from the gas outlet pipe once per hour using a collection bag, that is, the decomposition product is collected 10 times in this example.

[0049] The decomposition products were detected by gas chromatography-mass spectrometry, and the decomposition products were qualitatively and quantitatively analyzed.

[0050] In one example, when the target strategy is 200°C, the SF6 / N2 mixed gas is input into the shell to 0.6 MPa, and the heating rod in the local overheating simulation device is controlled to heat at 200°C for 10 hours, and the decomposition products of the SF6 / N2 mixed gas are detected every hour under the target strategy.

[0051] In some embodiments, before the step of inputting the SF6 / N2 mixed gas into the housing through the air inlet pipe to a preset pressure, the method further includes: Filling high-purity N2 to clean the interior of the local overheating simulation device, repeating several times; The interior of the local overheating simulation device was evacuated.

[0052] For example, high-purity nitrogen can be injected to a pressure of 0.2-0.3 MPa inside the local overheating simulation device, and the inside of the local overheating simulation device can be cleaned three times. This ensures that all gas impurities inside the local overheating simulation device are completely discharged, ensuring the accuracy and reliability of subsequent experiments.

[0053] In some embodiments, before repeatedly flushing the interior of the local overheating simulation device with high-purity N2 several times, the method further includes: removing the cover and wiping the interior of the local overheating simulation device with an antistatic dust-free cloth moistened with anhydrous ethanol to ensure that the interior walls of the local overheating simulation device are clean and free of impurities to avoid any impact on the experimental results. The cover is then reinstalled on the upper end of the local overheating simulation device, and the interior of the local overheating simulation device is evacuated to ensure that the device is airtight.

[0054] In some embodiments, before the step of controlling the heating rod in the local overheating simulation device to heat under the target strategy, the method further includes: The local overheating simulation device filled with the SF6 / N2 mixed gas is left to stand for several hours; before and after standing still, the internal pressure of the local overheating simulation device is determined using the pressure gauge in the local overheating simulation device; based on the internal pressure before and after standing still, it is judged whether the interior of the local overheating simulation device is airtight; if the airtightness is good, the step of controlling the heating rod in the local overheating simulation device to heat under the target strategy is executed.

[0055] In some embodiments, after heating the SF6 / N2 gas mixture under the target strategy and detecting decomposition products using a gas chromatography-mass spectrometer, the process further includes: evacuating the interior of the local overheating simulation device, illustratively to -0.1 MPa, and then filling and purging the device with nitrogen several times. This prevents the release of decomposition products from the device when the cover is removed, ensuring the safety of experimenters. In one example, nitrogen is filled to a pressure of 0.3-0.4 MPa, and the purge is repeated three times.

[0056] S103. Determine the kth preset strategy as the target strategy, repeat step S102, the steps of inputting the SF6 / N2 mixed gas into the local overheating simulation device to a preset gas pressure, controlling the heating rod in the local overheating simulation device to heat under the target strategy, and detecting the decomposition products of the SF6 / N2 mixed gas when heated under the target strategy, wherein k is a positive integer between 2 and N.

[0057] In the embodiment of the present application, since there may be multiple preset strategies, it is necessary to detect the decomposition products of the SF6 / N2 mixed gas during heating under each preset strategy.

[0058] S104: Screening out characteristic decomposition products from the decomposition products. In the embodiment of the present application, characteristic decomposition products for identifying local overheating defects are screened out from the decomposition products of the SF6 / N2 mixed gas.

[0059] In the example mentioned above where N preset strategies could be 11 preset strategies, no sulfur- and nitrogen-containing decomposition products were detected in the SF6 / N2 mixture at 175°C, and only trace amounts of CO2 and CO were detected. This is likely due to the influx of air during gas collection or the influence of impurities in the fresh gas, and can be ignored. Therefore, it is believed that the SF6 / N2 mixture did not decompose at this temperature. When the temperature was raised to 200°C, small amounts of SO2 and N2O were detected after 10 hours, indicating that the SF6 / N2 mixture begins to thermally decompose within this temperature range. This also shows that the thermal decomposition temperature of the SF6 / N2 mixture is roughly consistent with the initial decomposition temperature of SF6 alone. This study conducted 10 sets of experiments, including nine sets of experiments at 25°C intervals from 200°C to 400°C, and one high-temperature experiment at 450°C. The results show that the decomposition products of SF6 / N2 mixed gas under overheating conditions are CS2, COS, H2S, SO2, N2O, SOF2, CO2 and SO2F2. In this overheating fault simulation test, the nitrogen-containing decomposition product detected is N2O, which can be used as a characteristic decomposition product for identifying local overheating defects, that is, the characteristic decomposition product of overheating defects of SF6 / N2 mixed gas is different from that of pure SF6 gas. The bar graph of the concentration of the characteristic decomposition product N2O changing with temperature and time is shown in the figure below. Figure 3 shown.

[0060] In some embodiments, it is determined that decomposition products of the SF6 / N2 mixed gas under an overheating defect condition include CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2; the step of determining the target Fourier transform output wavelength corresponding to N2O gas among the characteristic decomposition products of the SF6 / N2 mixed gas under the overheating defect condition includes: determining the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2, respectively; and screening out the Fourier transform output wavelengths corresponding to N2O that are different from the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, SOF2, CO2, and SO2F2, and using them as the target Fourier transform output wavelengths corresponding to N2O gas.

[0061] In the embodiment of the present application, the Fourier transform output wavelength corresponding to N2O is screened out from the Fourier transform output wavelength corresponding to CS2, COS, H2S, SO2, SOF2, CO2 and SO2F2, and is used as the target Fourier transform output wavelength corresponding to N2O gas. This can avoid interference of other products in the detection results during subsequent detection of N2O gas.

[0062] For example, the absorption wavelength of N2O, a characteristic decomposition product of SF6 / N2 mixed gas, is searched through the NIST database. The absorption wavelength of N2O is compared with the wavelengths of other decomposition products. It is found that CO2 and SO2 have similar absorption wavelengths to the characteristic decomposition products. The infrared absorption wavelengths of the characteristic decomposition products N2O and CO2 and SO2 are as follows: Figure 4-6 As shown, Figure 4 Schematic diagram of SO2 infrared spectrum absorption wavelength, Figure 5 Schematic diagram of CO2 infrared spectrum absorption wavelength, Figure 6 Schematic diagram of N2O infrared spectrum absorption wavelength.

[0063] In this embodiment, the Fourier transform output wavelengths of different gases may exist in multiple bands. Here, selecting a Fourier transform output wavelength that is distinct from CS2, COS, H2S, SO2, SOF2, CO2, and SO2F2 refers to selecting a target Fourier transform output wavelength that is distinct from any band of CS2, COS, H2S, SO2, SOF2, CO2, and SO2F2. In some embodiments, one or more bands of the Fourier transform output wavelength of N2O that are distinct from any band of CS2, COS, H2S, SO2, SOF2, CO2, and SO2F2 can be directly found in the NIST database and used as the target Fourier transform output wavelength. In other embodiments, one or more bands of the Fourier transform output wavelength of N2O that are distinct from any band of CS2, COS, H2S, SO2, SOF2, CO2, and SO2F2 can be found in the NIST database and, after adjustment to better suit practical applications, determined as the target Fourier transform output wavelength.

[0064] Using a Fourier transform infrared spectrometer with a set target Fourier transform output wavelength to detect N2O standard gas, it was found that the concentration of the characteristic product N2O can be accurately detected based on the infrared spectrum absorption principle. The test results and the wavelength set by the infrared spectrometer are as follows Figure 7 and 8 As shown, Figure 7 The upper middle figure shows the wavelength setting when using Fourier infrared spectrometer to detect the characteristic decomposition product N2O. Figure 7 The figure in the lower middle is a schematic diagram of the detection results of the characteristic decomposition product N2O gas standard gas. Figure 8 The upper middle picture shows the full wavelength of N2O gas in the Fourier infrared spectrometer. Figure 8 The figure in the lower middle is a schematic diagram of the N2O gas detection results.

[0065] Through the NIST database analysis of the absorption wavelengths of N2O and other SF6 / N2 mixed gas decomposition products, it is known that the gases that interfere with the detection of N2O gas are mainly (SO2, CO2). When using a Fourier transform infrared spectrometer for detection, the interference of interfering gases on the detection results is removed by selecting the wavelength and setting the method, thereby improving the detection accuracy and preventing the interference gases with infrared absorption wavelengths similar to those of the characteristic decomposition products from affecting the detection accuracy of the Fourier transform infrared spectrometer. The Fourier transform infrared spectrometer with the target Fourier transform output wavelength is used to detect the SO2, CO2, and N2O mixed gas. The detection results are as follows: Figure 9 As shown, Figure 9 The upper middle picture shows the full wavelength range of the Fourier infrared spectrometer. Figure 9 The top line in the lower middle figure is a schematic diagram of N2O concentration when using a Fourier transform infrared spectrometer to detect N2O mixed gas containing interfering gases (CO2, SO2). The middle line is a schematic diagram of CO2 when using a Fourier transform infrared spectrometer to detect N2O mixed gas containing interfering gases (CO2, SO2). The bottom line is a schematic diagram of SO2 concentration when using a Fourier transform infrared spectrometer to detect N2O mixed gas containing interfering gases (CO2, SO2). The results show that by setting the output wavelength of the instrument, SO2, CO2, and N2O can be distinguished and the concentration of each gas can be detected separately. Therefore, this Fourier transform infrared spectrometer can be used to successfully detect N2O, a characteristic decomposition product of SF6 / N2 mixed gas, and can prevent interference from gases with similar absorption wavelengths to N2O.

[0066] In some embodiments, the step of determining the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2 and SO2F2 respectively includes: searching for the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2 and SO2F2 respectively from the NIST database.

[0067] S200 . At a work site, using a Fourier transform infrared spectrometer set with the target Fourier transform output wavelength, detect the concentration of N 2 O gas in the SF 6 / N 2 mixed gas in the power equipment.

[0068] In the embodiments of the present application, the SF6 / N2 gas mixture can be used for fault diagnosis and maintenance of insulating dielectric power equipment. By detecting N2O gas in the SF6 / N2 gas mixture in power equipment, it is possible to determine whether the power equipment is experiencing local overheating. If the concentration is above 0, it is determined that the power equipment has an overheating defect.

[0069] In the embodiment of the present application, by setting the target Fourier transform output wavelength of the Fourier transform infrared spectrometer, it is possible to prevent other gases in the decomposition gas of the SF6 / N2 mixed gas from affecting the detection of N2O gas and reducing the detection accuracy.

[0070] In some embodiments, the method further includes: transporting the detected SF6 / N2 mixed gas to a gas recovery device, so that the gas recovery device purifies and stores the detected SF6 / N2 mixed gas.

[0071] In the embodiment of the present application, a gas recovery device is added after the detection is completed to prevent toxic gases and non-environmentally friendly gases produced by the decomposition products of the SF6 / N2 mixed gas from polluting the atmosphere and threatening the health of workers.

[0072] In some embodiments, the step of purifying and storing the detected SF6 / N2 mixed gas includes: Purifying and filtering the detected SF6 / N2 mixed gas through a purification filter device to obtain purified and filtered gas; drying the purified and filtered gas through a drying and purification device to obtain dried gas; The dried gas is compressed and cooled, and then stored in a gas storage cylinder.

[0073] For example, the model of the equipment for purifying and storing the detected SF6 / N2 mixed gas may be KDZD-66.

[0074] In some embodiments, before the step of storing the gas in the gas storage cylinder, the method further comprises: extracting the gas in the gas storage cylinder using a vacuum pump.

[0075] In this embodiment, the gas in the gas storage cylinder is extracted by using a vacuum pump, which can ensure that the substances subsequently stored in the gas storage cylinder are not contaminated.

[0076] In some embodiments, the method further comprises: determining the extent of the overheating defect based on the concentration of the N2O gas; The step of determining the degree of overheating defect according to the concentration of the N2O gas includes: If it is higher than 0 and lower than 0.5 ppm, the degree of the overheating defect is determined to be a mild overheating defect; If it is not less than 0.5 ppm, determine whether the concentration of the N2O gas is higher than 1.5 ppm; If it is not higher than 1.5ppm, the degree of the overheating defect is determined to be a normal overheating defect; If it is higher than 1.5 ppm, the degree of the overheating defect is determined to be a severe overheating defect.

[0077] In this embodiment, electrical equipment overheating defects are classified into three severity levels: mild, normal, and severe. The severity of an electrical equipment overheating defect is determined by measuring the concentration of the characteristic decomposition product, N2O. The relationship between the concentration of the characteristic decomposition product, N2O, temperature, and heating time, was determined by conducting an overheating defect test on a SF6 / N2 mixed gas at a temperature between 200°C and 450°C (with a temperature interval of 25°C, a heating time of 10 hours per group, and testing every hour). Figure 3 As shown. Analysis of the test results indicates that the concentration of the characteristic decomposition product, N2O, shows a positive correlation with heating time. A higher concentration of the characteristic decomposition product, N2O, indicates a longer duration of overheating in electrical equipment, which in turn has a greater impact on the equipment's insulation performance. Current test results show that when the characteristic decomposition product, N2O, is detected at a concentration below 0.5 ppm, the overheating duration is shorter; when the concentration is between 0.5 ppm and 1.5 ppm, the overheating duration is longer; and when the concentration is greater than 1.5 ppm, the overheating duration is very long. Therefore, a concentration below 0.5 ppm is considered a mild overheating defect; a concentration between 0.5 ppm and 1.5 ppm is considered a moderate overheating defect; and a concentration greater than 1.5 ppm is considered a severe overheating defect. By detecting the presence and concentration of the characteristic decomposition product, the presence and severity of overheating in electrical equipment can be determined, laying the foundation for online fault diagnosis of electrical equipment. Different levels of overheating can be addressed using different solutions. For example, if there are general or severe overheating defects, staff should be notified immediately to address them. If there are minor overheating defects, the handling can be appropriately delayed.

[0078] The method in the embodiments of the present application is the first to apply an N2O sensor that uses the infrared spectral absorption principle to detect N2O, namely a Fourier transform infrared spectrometer, to the diagnosis of power equipment defects. Compared with traditional gas chromatography, the detection method is simple, the detection equipment is portable, the detection time is shortened, and the limitation of the detection location is solved. The detection can be performed at the equipment working site, thereby improving the efficiency of subsequent operation and maintenance, reducing the risk of major equipment failures, and improving the safety of power grid operation. After comparing the infrared absorption wavelengths of overheating defect decomposition products, the selection of light source wavelength is added to the Fourier transform infrared spectrometer to prevent other decomposition products from interfering with the detection results, thereby improving the detection accuracy of the Fourier transform infrared spectrometer, making the power equipment defect diagnosis more accurate and better guiding equipment operation and maintenance. A gas recovery device is added to prevent environmentally harmful and toxic substances in the decomposition products of the mixed gas from flowing into the atmosphere, thereby achieving accurate detection while contributing to environmental protection.

[0079] The method described in the embodiments of the present application accurately and promptly diagnoses and maintains overheating defects in electrical equipment using SF6 / N2 mixed gas as the insulating medium. It also avoids the cumbersome decomposition product detection steps currently required, which are often limited by site constraints. For the first time, a N2O sensor based on infrared spectroscopy absorption is used in power equipment maintenance. This allows on-site gas detection of electrical equipment to determine whether a defect has occurred. The severity of any defect can also be determined based on the detected N2O gas concentration. This facilitates timely fault diagnosis and maintenance of power equipment by on-site personnel, preventing more serious defects or even failures that could impact the safe operation of the power grid. The present invention also adds a step for selecting a specific infrared absorption wavelength (i.e., the target Fourier transform output wavelength) and a gas recovery device to a conventional Fourier transform infrared spectrometer, improving detection accuracy and preventing the emission of environmentally harmful gases.

[0080] In summary, the present invention provides a method for detecting N2O, a characteristic decomposition product of mixed gas in electrical equipment. The method determines the infrared absorption wavelength corresponding to N2O, a characteristic decomposition product of the SF6 / N2 mixed gas when a local overheating problem occurs, sets a target Fourier transform output wavelength of a Fourier transform infrared spectrometer, and uses the Fourier transform infrared spectrometer to detect N2O gas, a characteristic decomposition product of the SF6 / N2 mixed gas when a local overheating defect occurs in the electrical equipment, by setting the output wavelength of the Fourier transform infrared spectrometer. This allows on-site staff to quickly and conveniently detect the concentration of N2O gas.

[0081] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application. The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application. These improvements and variations should also be regarded as the scope of protection of the present application.

Claims

1. A method for detecting N2O, a characteristic decomposition product of mixed gas in electrical equipment, characterized in that: include: determining a target Fourier transform output wavelength corresponding to a characteristic decomposition product of the SF6 / N2 mixed gas under an overheat defect condition, wherein the characteristic decomposition product is N2O gas; At a work site, the concentration of N2O gas in the SF6 / N2 mixed gas in the power equipment is detected using a Fourier transform infrared spectrometer set with the target Fourier transform output wavelength.

2. The method according to claim 1, characterized in that Also includes: The detected SF6 / N2 mixed gas is transported to a gas recovery device, so that the gas recovery device purifies and stores the detected SF6 / N2 mixed gas.

3. The method according to claim 2, characterized in that The step of purifying and storing the detected SF6 / N2 mixed gas comprises: Purifying and filtering the detected SF6 / N2 mixed gas through a purification filter device to obtain purified and filtered gas; drying the purified and filtered gas through a drying and purification device to obtain dried gas; The dried gas is compressed and cooled, and then stored in a gas storage cylinder.

4. The method according to claim 3, characterized in that Before the step of storing the gas in the gas storage cylinder, the method further comprises: extracting the gas in the gas storage cylinder by using a vacuum pump.

5. The method according to claim 1, wherein Determining that the decomposition products of the SF6 / N2 mixed gas under the overheating defect condition include CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2; the step of determining the target Fourier transform output wavelength corresponding to the N2O gas in the characteristic decomposition products of the SF6 / N2 mixed gas under the overheating defect condition comprises: Determine the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2 respectively; From the Fourier transform output wavelength corresponding to N2O, the Fourier transform output wavelength that is different from that corresponding to CS2, COS, H2S, SO2, SOF2, CO2 and SO2F2 is screened out and used as the target Fourier transform output wavelength corresponding to N2O gas.

6. The method according to claim 5, characterized in that The step of determining the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2 and SO2F2 respectively comprises: Look up the Fourier transform output wavelengths corresponding to CS2, COS, H2S, SO2, N2O, SOF2, CO2, and SO2F2 from the NIST database.

7. The method according to claim 5, characterized in that Gas chromatography-mass spectrometry was used to determine that the decomposition products of SF6 / N2 mixed gas under overheating defect conditions included CS2, COS, H2S, SO2, N2O, SOF2, CO2 and SO2F2.

8. The method according to claim 7, characterized in that The gas chromatograph-mass spectrometer uses 99.9995% pure helium as a carrier gas. The column oven control program in the gas chromatograph in the gas chromatograph-mass spectrometer includes stabilizing the temperature at 40°C within 0 to 7 minutes; increasing the temperature to 220°C at a rate of 15°C per minute, and maintaining it at 220°C for 2 minutes; the gas chromatograph parameters of the gas chromatograph are set as: total flow rate of 111.5 mL / min, split ratio of 30:1, inlet temperature of 200°C, pressure of 167.6 kPa, maximum column temperature of 300°C, column flow rate of 3.5 mL / min, linear velocity of 47.7 cm / s, and purge flow rate of 3.0 mL / min.

9. The method according to claim 7, characterized in that The parameters of the mass spectrometer in the gas chromatography-mass spectrometry instrument are set as follows: the gas chromatography and mass spectrometry interface temperature is 220°C, the solvent delay time is 0 minute, the scan interval is 0.3s, the microscan width is 0u, the detector voltage is 0.1kV, the ion source is an electron ionization source, and the ion source temperature is 200°C; the detector uses an isolated dynode-type electron multiplier.

10. The method according to claim 1, characterized in that Also includes: determining the degree of overheating defect according to the concentration of the N2O gas; The step of determining the degree of overheating defect according to the concentration of the N2O gas includes: If it is higher than 0 and lower than 0.5 ppm, the degree of the overheating defect is determined to be a mild overheating defect; If it is not less than 0.5 ppm, determine whether the concentration of the N2O gas is higher than 1.5 ppm; If it is not higher than 1.5 ppm, the degree of the overheating defect is determined to be a normal overheating defect; if it is higher than 1.5 ppm, the degree of the overheating defect is determined to be a severe overheating defect.

11. The method according to claim 1, wherein Also includes: The decomposition products of SF6 / N2 mixed gas under overheating defect conditions were generated using a local overheating simulation device; The local overheating simulation device includes: a shell, an air inlet pipe, an air outlet pipe, a vacuum pump, a pressure gauge, a heating rod, a temperature control distribution box and a power supply; The air inlet pipe and the air outlet pipe are respectively communicated with the interior of the housing, the pressure gauge is arranged on the air inlet pipe, and the vacuum pump is arranged on the air outlet pipe; The heating rod is located inside the shell to provide heat energy to the inside of the shell, and the heating rod is connected to the power supply through the temperature control distribution box; A cover plate is movably provided on the upper end of the shell.

12. The method according to claim 11, characterized in that The step of using the local overheating simulation device to generate decomposition products of the SF6 / N2 mixed gas under overheating defect conditions includes: Presetting N preset strategies, and using the first of the N preset strategies as the target strategy, wherein the preset strategy includes a heating temperature and a preset heating time when the heating rod is heating; The SF6 / N2 mixed gas is introduced into the housing through an air intake pipe to a preset pressure, and a heating rod in the local overheating simulation device is controlled to heat under the target strategy, and decomposition products of the SF6 / N2 mixed gas are detected when heated under the target strategy; Determine the kth preset strategy as the target strategy, repeat the steps of inputting the SF6 / N2 mixed gas into the local overheating simulation device to a preset gas pressure, controlling the heating rod in the local overheating simulation device to heat under the target strategy, and detecting the decomposition products of the SF6 / N2 mixed gas when heated under the target strategy, wherein k is a positive integer between 2 and N.

13. The method according to claim 12, characterized in that Also includes: From the decomposition products, characteristic decomposition products are screened out.

14. The method according to claim 12, characterized in that Before the step of inputting the SF6 / N2 mixed gas into the housing through the air inlet pipe to a preset pressure, the method further includes: Filling high-purity N2 to clean the interior of the local overheating simulation device, repeating several times; The interior of the local overheating simulation device was evacuated.

15. The method according to claim 12, characterized in that Before the step of controlling the heating rod in the local overheating simulation device to heat under the target strategy, the method further includes: The local overheating simulation device filled with the SF6 / N2 mixed gas is left to stand for several hours; before and after standing still, the internal pressure of the local overheating simulation device is determined using the pressure gauge in the local overheating simulation device; based on the internal pressure before and after standing still, it is judged whether the interior of the local overheating simulation device is airtight; if the airtightness is good, the step of controlling the heating rod in the local overheating simulation device to heat under the target strategy is executed.

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