Overheating Fault Analysis Method Based on Insulating Gas Fault Simulation Detection Platform

Abstract

The present invention discloses an overheating fault analysis method based on an insulating gas fault simulation detection platform, including: sampling the mixed insulating gas input into the stainless steel gas tank, and determining the total ion current chromatogram of C4F7N pure gas before heating through chromatographic detection; performing stepwise heating on the mixed insulating gas in the stainless steel gas tank within the temperature range of 200°C - 700°C, and sampling the mixed insulating gas using a gas chromatography-mass spectrometry instrument to obtain samples after each overheating temperature gradient is completed; detecting the samples obtained step by step to obtain the total ion current chromatogram of C4F7N gas after heating, and comparing the total ion current chromatogram of C4F7N gas after heating with the total ion current chromatogram of C4F7N gas before heating, and determining that when gases of CO and C3F6 appear, a local overheating fault has occurred. The present invention provides a basis for overheating fault diagnosis of mixed gas insulated equipment and research on gas-solid material compatibility.

Description

Technical Field

[0001] The present invention relates to a method for analyzing overheating faults based on an insulating gas fault simulation detection platform, which is applied to the overheating protection of gas-insulated electrical equipment. Background Art

[0002] When problems such as poor joint contact, internal electrical circuit failures, or poor insulating media occur in gas-insulated electrical equipment, the equipment often generates heat and causes overheating faults. Overheating faults may cause the decomposition of gas-insulating media, which not only endangers the stable operation of electrical equipment but also poses risks to the surrounding environment and the personal safety of operation and maintenance personnel. Therefore, it is necessary to monitor overheating faults and take effective solutions. In recent years, online monitoring and fault diagnosis of gas-insulated electrical equipment based on the decomposition gas method have received much attention. Monitoring characteristic information such as the types and contents of decomposition products of gas-insulating media under insulation faults of electrical equipment can achieve the monitoring and diagnosis of the types and severity of insulation faults. However, a large amount of experimental research data is required to implement the decomposition gas method for monitoring electrical equipment. Therefore, it is necessary to simulate overheating faults in a laboratory environment to provide a basis for fault diagnosis based on the decomposition gas method.

[0003] Perfluoroisobutyronitrile C4F7N is considered to be the most promising new environmentally friendly insulating gas at present. Its insulation performance is twice that of sulfur hexafluoride gas under normal pressure. However, the liquefaction temperature of C4F7N is -4.7°C, and it is extremely easy to liquefy in cold winter weather and high-altitude areas. When applied, it needs to be mixed with buffer gases such as CO2 or CO2 and O2 to reduce the liquefaction temperature of the gas. The structural properties of the C4F7N / CO2 / O2 mixed gas are complex. Under overheating faults, insulating gases often decompose to produce gas decomposition products, and the decomposition mechanism is not yet clear. Summary of the Invention

[0004] The object of the present invention is to propose a method for analyzing overheating faults based on an insulating gas fault simulation detection platform, in order to better study the reaction mechanism of C4F7N / CO2 mixed gas with trace amounts of moisture, oxygen, and materials such as metal and rubber in the gas chamber during equipment overheating faults, accurately detect gas decomposition products after faults, and provide a basis for overheating fault diagnosis and research on the compatibility of gas-solid materials.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] Overheating Fault Analysis Method Based on an Insulating Gas Fault Simulation Detection Platform. The simulation detection platform includes a gas chromatography-mass spectrometry (GC-MS) instrument, a scanning electron microscope / X-ray energy spectrometer, three gas cylinders for storing C4F7N, O2, and CO2 insulating gases, a stainless-steel gas tank, a vacuum pump, and a temperature controller. An electric heating rod and a temperature sensor are provided in the stainless-steel gas tank, and the electric heating rod and the temperature sensor are connected to the temperature controller through insulated connecting wires. A gas inlet / outlet interface and a solid sampling interface are provided in the stainless-steel gas tank. The gas inlet / outlet interface is connected to the GC-MS instrument, the three gas cylinders storing insulating gases, and the vacuum pump through valves respectively. A solid sampling stage is provided at the solid sampling interface, and the scanning electron microscope / X-ray energy spectrometer is used to perform elemental analysis on the samples taken from the solid sampling stage. The steps of the analysis method include:

[0007] First, use the vacuum pump to evacuate the stainless-steel gas tank.

[0008] Second, input the C4F7N:O2:CO2 mixed insulating gas into the stainless-steel gas tank according to the actual application ratio, and place it at room temperature for at least 12 hours to fully mix the three gases.

[0009] Third, take a sample of the mixed insulating gas input into the stainless-steel gas tank, and determine the total ion current chromatogram of pure C4F7N gas before heating through chromatographic detection.

[0010] Fourth, perform stepped heating on the mixed insulating gas in the stainless-steel gas tank within the temperature range of 200°C - 700°C, with a heating temperature gradient of 50°C. The overheating time at each overheating temperature gradient is 5 hours. After each overheating temperature gradient is completed, use the GC-MS instrument to take a sample of the mixed insulating gas to obtain a sample.

[0011] Fifth, detect the samples obtained step by step to obtain the total ion current chromatogram of C4F7N gas after heating, compare the total ion current chromatogram of C4F7N gas after heating with the total ion current chromatogram of C4F7N gas before heating, and determine whether the newly appeared decomposed gases are CO and C3F6 gases. Since CO gas is produced by the decomposition of CO2 at high temperatures and impurities in pure C4F7N gas will decompose to produce C3F6 gas; when CO and C3F6 gases appear, and since it is at an overheating temperature ≥200°C, CO gas is produced by the decomposition of CO2 and impurities in pure C4F7N gas will decompose to produce C3F6 gas; therefore, it is determined that when CO and C3F6 gases appear, a local overheating fault has occurred.

[0012] The solution is further: The method further includes: judging the severity of the local overheating fault through the content ratio of CO and C3F6 R Calculation formula 1

[0013] R= c[CO] / c[C3F6], Formula 1

[0014] Wherein, c[CO] is the content of CO; c[C3F6] is the content of C3F6;

[0015] R When it gradually decreases, it indicates that the overheating temperature gradually increases. When R > 6, the overheating temperature range is [200°C, 450°C]; 4 < R < 6, the overheating temperature range is [450°C, 500°C]; When R continues to decrease, it indicates that the overheating temperature is greater than 500°C; When R ≤ 2, it indicates that the overheating temperature is higher than 650°C.

[0016] A further aspect of the solution is: The method further includes: When R ≤ 2, remove the solid sampling stage, and use a scanning electron microscope / X-ray energy spectrometer to perform elemental analysis on the surface of the solid sampling stage to detect whether there are new elemental components, and thereby judge whether solid deposits have occurred.

[0017] A further aspect of the solution is: When the fluorine (F) element is detected, it indicates that the decomposition products of the overheating fault have undergone a chemical reaction with the material. At this time, the overheating fault is serious and attention and early warning should be caused.

[0018] A further aspect of the solution is: The method further includes: Based on the external standard quantitative method, obtain the content of each impurity component in the sample. According to the chromatographic peak area of the characteristic mass-to-charge ratio of different impurity gas components, the chromatographic peak area of the characteristic mass-to-charge ratio of the corresponding standard gas, and the content of the standard gas, calculate the content of each impurity gas component according to Formula 2:

[0019] C i = (S i / S I ) × C I Formula 2

[0020] Wherein, S i is the peak area corresponding to the characteristic mass-to-charge ratio of a certain component in the overheating decomposition products of the insulating gas, S I is the peak area corresponding to the same characteristic mass-to-charge ratio of the standard gas of the component to be determined, C I is the content of the standard gas of the component to be determined, and C i is the content of the component to be determined.

[0021] A further aspect of the solution is: When R ≤ 2, the impurity gases generated in addition to CO and C3F6 also include C3F8, CNCN, CF3CN, and C2F5CN, indicating that C4F7N begins to decompose and a serious overheating fault occurs.

[0022] The further solution is that the vacuum pumping treatment is as follows: First, a certain amount of CO2 gas is filled into the stainless-steel gas tank, and then vacuum is pumped, repeating 4 times.

[0023] The further solution is that the judgment on whether the newly appeared decomposed gas is CO and C3F6 gas is as follows: The decomposed gas at different retention times is compared with the CO gas in the NIST mass spectrometry database for the matching degree. When the matching degree is 95% or above at a certain retention time, and the characteristic fragment ions and their relative abundances of this gas have the same retention time as the CO standard gas under the same chromatographic method setting conditions, it is determined that the gas at this retention time is CO gas; similarly, after comparing with the NIST mass spectrometry database and the mass spectrum peak of C3F6 standard substance, when the matching degree is 95% or above at a certain retention time, and the characteristic fragment ions and their relative abundances of this gas have the same retention time as the C3F6 standard gas under the same chromatographic method setting conditions, it is determined that the gas at this retention time is C3F6 gas.

[0024] The further solution is that the input of the C4F7N:O2:CO2 mixed insulating gas into the stainless-steel gas tank according to the actual application ratio is as follows: Based on Dalton's law of partial pressures, C4F7N gas is filled into the stainless-steel gas tank until the pressure reaches 0.05 MPa, then O2 is filled until the pressure reaches 0.1 MPa, and finally CO2 is filled into the gas chamber until the pressure reaches 0.5 MPa. The mixing ratio of C4F7N:O2:CO2 is 1:1:8.

[0025] The further solution is that the gas inlet and outlet interface is connected to the first passage of a four-way pipe through a first valve. The second passage of the four-way pipe is connected to the input interface of the gas chromatography-mass spectrometry (GC-MS) instrument through a second valve. The input interface of the GC-MS instrument 1 uses a six-port valve input interface of gas chromatography; the third passage of the four-way pipe is connected to the vacuum pump through a third valve, and the fourth passage of the four-way pipe is connected to three gas cylinders through three fourth valves respectively.

[0026] The beneficial effect of the present invention is that through the method of the present invention, it is possible to better study the reaction mechanism of the C4F7N / O2 / CO2 mixed gas with trace amounts of moisture, oxygen, and materials such as metal and rubber in the gas chamber during the overheating failure of the mixed gas insulated equipment, accurately detect the gas decomposition products after the failure, and provide a basis for the overheating failure diagnosis of the mixed gas insulated equipment and the study of the gas-solid material compatibility.

[0027] The present invention will be described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0028] Figure 1 is a schematic structural diagram of the simulation detection platform of the present invention;

[0029] Figure 2It is the total ion current chromatogram of pure C4F7N gas before the experiment.

[0030] Figure 3 It is the total ion current chromatogram of the decomposed gas under the overheating fault at 200°C - 650°C.

[0031] Figure 4 It is the total ion current chromatogram of the decomposed gas under the overheating fault at 650°C - 700°C.

[0032] Figure 5 It is the relationship between the content ratio c[CO] / c[C3F6] of CO and C3F6 gases and the overheating temperature.

[0033] Figure 6 It is the scanning electron microscope / X-ray energy spectrum detection of the surface of the solid material after the high-temperature overheating fault. Specific implementation mode

[0034] An overheating fault analysis method based on an insulating gas fault simulation detection platform. The simulation detection platform includes a gas chromatography-mass spectrometry instrument 1, a scanning electron microscope / X-ray energy spectrometer 2, three gas cylinders 3 for storing C4F7N, O2, and CO2 insulating gases, a stainless steel gas tank 4, a vacuum pump 5, and a temperature controller 6. The stainless steel gas tank is provided with a gas inlet / outlet interface 401 and a solid sampling interface 402. The gas inlet / outlet interface 401 is connected to the gas chromatography-mass spectrometry instrument, the three gas cylinders 3 for storing insulating gases, and the vacuum pump 5 through valves respectively, as Figure 1 shown. The gas inlet / outlet interface 401 is connected to the first passage of a four-way pipe 8 through a first valve 7. The second passage of the four-way pipe 8 is connected to the input interface 101 of the gas chromatography-mass spectrometry instrument 1 through a second valve 9. The input interface 101 of the gas chromatography-mass spectrometry instrument 1 uses a gas chromatography six-way valve input interface. The third passage of the four-way pipe 8 is connected to the vacuum pump 5 through a third valve 10. The fourth passage of the four-way pipe 8 is connected to the three gas cylinders 3 through three fourth valves 11 respectively. A solid sampling stage 12 is provided at the solid sampling interface 402. The solid sampling stage 12 is connected to the scanning electron microscope / X-ray energy spectrometer 2 through a probe 13. The scanning electron microscope / X-ray energy spectrometer is used for elemental analysis of the samples on the solid sampling stage. An electric heating rod 14 and a temperature sensor 15 are provided in the stainless steel gas tank 4. The electric heating rod 14 and the temperature sensor 15 are connected to the temperature controller 6 through insulated connecting wires.

[0035] Among them: A central hole 403 is provided at the center point of the upper cover of the stainless steel gas tank. Through holes 404 are respectively provided on both sides of the central hole. An epoxy resin flange 16 is provided on the through hole, and a terminal post 17 is fixed on the flange. The terminal post passes through the through hole and extends into the stainless steel gas tank 4. The outer shell material of the electric heating rod 14 is austenitic chromium-nickel stainless steel. The two extreme ends of the electric heating rod 14 are respectively connected and fixed to the two terminal posts and are suspended at the center of the stainless steel gas tank. A stainless steel flange 18 is provided on the central hole 403 of the upper cover, and the temperature sensor connecting wire is hermetically fixed and led out from the stainless steel flange; the temperature sensor is a K-type thermocouple, and the temperature measuring probe of the K-type thermocouple is located directly above the heating rod and close to the heating rod.

[0036] An air vent hole 405 is provided on the upper cover of the stainless steel gas tank, and the air vent hole is connected to a pressure gauge 19. A flange cover 20 is provided at the solid sampling interface, and the solid sampling table 12 is connected and fixed to the flange cover 20. The temperature controller 6 is connected to an AC voltage regulator 21, and the temperature controller is connected to the temperature sensor through an intelligent digital display temperature controller 22; the intelligent digital display temperature controller is a standard product that displays the temperature value and has a temperature setting function. The intelligent digital display temperature controller is connected to the K-type thermocouple to form a temperature negative feedback adjustment loop of the temperature controller. The temperature controller 6 integrates a voltage stabilizing circuit, a relay, a temperature negative feedback adjustment circuit, a voltmeter and an ammeter, and is used to detect the voltage and current of the heating rod and maintain the temperature of the heating rod stable. The shape of the stainless steel tank 4 is a cuboid with an open top; a square sealing groove is provided around the top end of the stainless steel tank body, and an O-ring is provided in the sealing groove. The upper cover 405 of the stainless steel gas tank presses the O-ring to form a seal for the stainless steel tank 4. The steps of the analysis method include:

[0037] One, perform a vacuum pumping treatment on the stainless steel gas tank with a vacuum pump: First, fill a certain amount of CO2 gas into the stainless steel gas tank, and then pump the vacuum, repeating 4 times;

[0038] Two, input the C4F7N:O2:CO2 mixed insulating gas into the stainless steel gas tank according to the actual application ratio, and place it at room temperature for at least 12 hours to fully mix the three gases. The process is as follows: Based on Dalton's law of partial pressures, fill C4F7N gas into the stainless steel gas tank until the pressure is 0.05 MPa, then fill O2 until the pressure is 0.1 MPa, and finally fill CO2 into the gas chamber until the pressure is 0.5 MPa. The mixing ratio of C4F7N:O2:CO2 is 1:1:8;

[0039] Three, sample the mixed insulating gas input into the stainless steel gas tank, and determine the total ion current chromatogram of pure C4F7N gas before heating through chromatographic detection;

[0040] Fourth, perform stepwise heating on the mixed insulating gas in the stainless steel gas tank within the temperature range of 200°C - 700°C, with a heating temperature gradient of 50°C. The overheating time at each overheating temperature gradient is 5 hours. After each overheating temperature gradient is completed, use a gas chromatography - mass spectrometry instrument to sample the mixed insulating gas to obtain samples;

[0041] Fifth, detect the samples obtained step by step to obtain the total ion current chromatogram of C4F7N gas after heating. Compare the total ion current chromatogram of C4F7N gas after heating with that before heating, and determine whether the newly appeared decomposed gases are CO and C3F6 gases. Since CO gas is produced by the decomposition of CO2 at high temperatures, and impurities in pure C4F7N gas will decompose to produce C3F6 gas; when CO and C3F6 gases appear, and since it is at an overheating temperature ≥ 200°C, CO gas is produced by the decomposition of CO2, and impurities in pure C4F7N gas will decompose to produce C3F6 gas; therefore, it is determined that when CO and C3F6 gases appear, a local overheating fault has occurred.

[0042] Among them: Before the experiment, sample and detect the pure C4F7N gas in the test gas chamber. It is found that the fragment ions and their relative abundances contained in the impurity with a chromatographic detection retention time of 22.76 min are: m / z = 69 (CF3+, 100%), m / z = 151 (C3HF6+, 22%), m / z = 82 (CF2CHF+, 18%), m / z = 51 (CHF2+, 12%), m / z = 31 (CF+, 4%) and m / z = 101 (CF3CHF+, 2%). These characteristic fragment ions and their relative abundances are the same as the fragment peaks of the heptafluoropropane CF3CHFCF3 (C3HF7) reference substance, and this impurity has the same retention time as C3HF7 under the same chromatographic detection method settings. Therefore, it is determined that the impurity with a retention time of 22.76 min is C3HF7 gas; and in this way, it is determined that the substance with a retention time of 24.82 min is C4F7N gas.

[0043] Moreover, the determination of whether the newly appeared decomposed gas is CO and C3F6 gas is as follows: The decomposed gas at different retention times is compared with the CO gas in the NIST mass spectrometry database for the matching degree. When the matching degree is 95% or above at a certain retention time, and the characteristic fragment ions and their relative abundances of this gas have the same retention time as the CO standard gas under the same chromatographic method setting conditions, then the gas at this retention time is determined to be CO gas; similarly, after comparison with the NIST mass spectrometry database and the mass spectrum peak of C3F6 standard substance, when the matching degree is 95% or above at a certain retention time, and the characteristic fragment ions and their relative abundances of this gas have the same retention time as the C3F6 standard gas under the same chromatographic method setting conditions, then the gas at this retention time is determined to be C3F6 gas; where: The retention time when the decomposed gas of the CO gas appears is 1.175 min; The retention time when the decomposed gas of the C3F6 gas appears is 9.65 min.

[0044] The method further includes: by the content ratio of CO and C3F6 R Calculate the severity of the local overheating fault according to formula 1,

[0045] R =c[CO] / c[C3F6] Formula 1

[0046] where, c[CO] is the content of CO; c[C3F6] is the content of C3F6;

[0047] R When it gradually decreases, it indicates that the overheating temperature gradually increases. When R >6, the overheating temperature range is [200℃, 450℃]; 4 < R <6, the overheating temperature range is [450℃, 500℃]; When R continues to decrease, it indicates that the overheating temperature is greater than 500℃; When R≤2, it indicates that the overheating temperature has been higher than 650℃.

[0048] The method further includes: when R≤2, remove the solid sampling stage, and use a scanning electron microscope / X-ray energy spectrometer to perform elemental analysis on the surface of the solid sampling stage to detect whether there are new elemental components, and accordingly judge whether there are solid deposits. And when the fluorine (F) element is detected, it indicates that the decomposition product of the overheating fault has a chemical reaction with the material. At this time, the overheating fault is serious and attention should be paid and a warning should be given.

[0049] When the overheat temperature is greater than 650 °C, it is detected by a gas chromatography-mass spectrometry that in addition to CO and C3F6, decomposition gases such as C3F8 (retention time 4.62 min), CF3CN (retention time 7.06 min), C2F5CN (retention time 20.15 min), and CNCN (22.61 min) are newly added. This indicates that C4F7 N begins to decompose, and the overheat failure at this time is already very serious. Therefore: The method further includes: Based on the external standard quantitative method, obtain the content of each impurity component in the sample. According to the chromatographic peak area of the characteristic mass-to-charge ratio of different impurity gas components, the chromatographic peak area of the characteristic mass-to-charge ratio of the corresponding standard gas, and the content of the standard gas, calculate the content of each impurity gas component according to Formula 2:

[0050] C i =(S i / S I )×C I Formula 2

[0051] where S i is the peak area corresponding to the characteristic mass-to-charge ratio of a certain component in the overheated decomposition products of the insulating gas, S I is the peak area corresponding to the same characteristic mass-to-charge ratio of the standard gas of the component to be determined, C I is the content of the standard gas of the component to be determined, and C i is the content of the component to be determined.

[0052] Therefore, when R ≤ 2, the generated impurity gases in addition to CO and C3F6 also include C3F8, CNCN, CF3CN, and C2F5CN, indicating that C4F7N begins to decompose and a serious overheat failure occurs.

[0053] The method further includes: After the detection of the gas decomposition products is completed, evacuate the stainless-steel gas cylinder. Remove the circular sealing cover on the side wall of the above-mentioned stainless-steel gas cylinder, place it on the sample stage of the scanning electron microscope / X-ray energy spectrometer, and use the scanning electron microscope / X-ray energy spectrometer to analyze the surface morphology and elemental composition of the solid sampling stage to detect whether solid deposits are generated.

[0054] Combined with Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 and Figure 6 , when the decomposition products of CO and C3F6 gases are detected, it indicates that a local overheat failure has occurred, and the overheat temperature range is [200 °C, 700 °C]. As the overheat temperature rises, the ratio of the decomposition gas content CO / C3F6 shows a downward trend. R When it gradually decreases, it indicates that the overheat temperature is gradually increasing. RWhen it is >6, the overheat temperature range is [200°C, 450°C]; when 4 < R < 4, the overheat temperature range is [450°C, 500°C]; as R continues to decrease, it indicates that the overheat temperature is greater than 500°C; when R ≤ 2, it indicates that the overheat temperature has exceeded 650°C. Since it involves stainless steel metal materials, when the overheat temperature is higher than 650°C, the test results of scanning electron microscope / X-ray energy spectrum show that the solid powder mainly contains fluorine element and iron (Fe) element, which mainly comes from the reaction of HF gas with Fe oxide in the inner wall oxide layer of stainless steel.

[0055] The above embodiments of the overheat fault analysis method based on the insulation gas fault simulation detection platform can be used to better study the reaction mechanism of C4F7N / O2 / CO2 mixed gas with trace moisture, oxygen and materials such as metal and rubber in the gas chamber during the overheat fault of the mixed gas insulated equipment, accurately detect the gas decomposition products after the fault, and provide a basis for the overheat fault diagnosis of the mixed gas insulated equipment and the research on the gas-solid material compatibility.

Claims

1. An overheating fault analysis method based on an insulating gas fault simulation detection platform, the simulation detection platform includes a gas chromatography-mass spectrometry instrument, a scanning electron microscope / X-ray energy spectrometer, three gas cylinders for storing insulating gases of C4F7N, O2, and CO2, a stainless steel gas tank, a vacuum pump, and a temperature controller. An electric heating rod and a temperature sensor are arranged in the stainless steel gas tank, and the electric heating rod and the temperature sensor are connected to the temperature controller through insulating connecting wires; a gas inlet / outlet interface and a solid sampling interface are arranged on the stainless steel gas tank. The gas inlet / outlet interface is respectively connected to the gas chromatography-mass spectrometry instrument, the three gas cylinders storing insulating gases, and the vacuum pump through valves. A solid sampling table is arranged at the solid sampling interface, and the scanning electron microscope / X-ray energy spectrometer is used for elemental analysis of the samples on the solid sampling table; characterized in that, The steps of the analysis method include: First, evacuate the stainless-steel gas tank with a vacuum pump. Second, input the C4F7N:O2:CO2 mixed insulating gas into the stainless-steel gas tank according to the actual application ratio, and place it at room temperature for at least 12 hours to fully mix the three gases. Third, take a sample of the mixed insulating gas input into the stainless-steel gas tank, and determine the total ion current chromatogram of pure C4F7N gas before heating through chromatographic detection. Fourth, perform stepwise heating on the mixed insulating gas in the stainless-steel gas tank within the temperature range of 200°C - 700°C, with a heating temperature gradient of 50°C, and the overheating time at each overheating temperature gradient is 5 hours. After each overheating temperature gradient is completed, use a gas chromatography-mass spectrometry (GC-MS) instrument to take a sample of the mixed insulating gas to obtain a sample. Fifth, detect the samples obtained step by step to obtain the total ion current chromatogram of C4F7N gas after heating, compare the total ion current chromatogram of C4F7N gas after heating with the total ion current chromatogram of C4F7N gas before heating, and determine whether the newly appeared decomposed gases are CO and C3F6 gases. Because CO gas is produced by the decomposition of CO2 at high temperature, and impurities in pure C4F7N gas will decompose to produce C3F6 gas; when CO and C3F6 gases appear, and since it is at an overheating temperature ≥ 200°C, CO gas is produced by the decomposition of CO2, and impurities in pure C4F7N gas will decompose to produce C3F6 gas; therefore, it is determined that when CO and C3F6 gases appear, a local overheating fault has occurred. The method further includes: by the content ratio of CO and C3F6 R judging the severity of the local overheating fault according to Calculation formula 1 R = c[CO] / c[C3F6] Formula 1 Among them, c[CO] is the content of CO; c[C3F6] is the content of C3F6. R When it gradually decreases, it indicates that the overheat temperature gradually increases. When R > 6, the overheat temperature range is [200°C, 450°C]; 4 < R < 6, the overheat temperature range is [450°C, 500°C]; When R continues to decrease, it indicates that the overheat temperature is greater than 500°C; When R ≤ 2, it indicates that the overheat temperature is already higher than 650°C; The method further includes: when R ≤ 2, remove the solid sampling stage, and use a scanning electron microscope / X-ray energy spectrometer to perform elemental analysis on the surface of the solid sampling stage to detect whether there are new elemental components, and thereby judge whether solid deposits have occurred. When the fluorine (F) element is detected, it indicates that the decomposition product of the overheating fault has undergone a chemical reaction with the material. At this time, the overheating fault is serious and attention should be paid and a warning should be issued.

2. The overheat fault analysis method according to claim 1, wherein The method further includes: based on the external standard quantitative method, obtain the content of each impurity component in the sample. According to the chromatographic peak area of the characteristic mass-to-charge ratio of different impurity gas components, the chromatographic peak area of the characteristic mass-to-charge ratio of the corresponding standard gas, and the content of the standard gas, calculate the content of each impurity gas component according to formula 2: C i =(S i / S I )×C I Formula 2 Among them, S i is the peak area corresponding to the characteristic mass-to-charge ratio of a certain component in the overheated decomposition products of the insulating gas, and S I is the peak area corresponding to the same characteristic mass-to-charge ratio of the standard gas of the component to be determined, C I is the content of the standard gas of the component to be determined, and C i is the content of the component to be determined.

3. The overheat fault analysis method according to claim 1, characterized in that When R ≤ 2, the impurity gases generated in addition to CO and C3F6 also include C3F8, CNCN, CF3CN, and C2F5CN, indicating that C4F7N begins to decompose and a serious overheating fault occurs.

4. The overheat fault analysis method according to claim 1, characterized in that, The evacuation treatment is: first, fill a certain amount of CO2 gas into the stainless-steel gas tank, and then evacuate the vacuum, repeating 4 times.

5. The overheat fault analysis method according to claim 1, wherein The method for determining whether the newly appeared decomposition gas is CO and C3F6 gas is as follows: the decomposition gas at different retention times is compared with the CO gas in the NIST mass spectrum database for matching. When the matching degree at one retention time is 95% or above, and the characteristic fragment ions and relative abundance of the gas have the same retention time as the CO standard gas under the same chromatographic method setting conditions, the gas at the retention time is determined to be CO gas; similarly, after comparing with the NIST mass spectrum database and the C3F6 standard material spectrum peak, when the matching degree at one retention time is 95% or above, and the characteristic fragment ions and relative abundance of the gas have the same retention time as the C3F6 standard gas under the same chromatographic method setting conditions, the gas at the retention time is determined to be C3F6 gas.

6. The overheat fault analysis method according to claim 1, characterized in that, The C4F7N:O2:CO2 mixed insulating gas is input into the stainless steel gas tank according to the actual application ratio: based on Dalton's law of partial pressures, C4F7N gas is filled into the stainless steel gas tank to a pressure of 0.05MPa, then O2 is filled to a pressure of 0.1MPa, and finally CO2 is filled into the gas chamber to a pressure of 0.5MPa. The mixing ratio of C4F7N:O2:CO2 is 1:1:

8.

7. The overheat fault analysis method according to claim 1, characterized in that The gas inlet and outlet interface is connected to the first passage of a four-way tube through a first valve, the second passage of the four-way tube is connected to the gas chromatograph-mass spectrometer input interface through a second valve, and the input interface of the gas chromatograph-mass spectrometer 1 uses the gas chromatograph six-way valve input interface; the third passage of the four-way tube is connected to the vacuum pump through a third valve, and the fourth passage of the four-way tube is connected to three gas cylinders respectively through three fourth valves.

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