An online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS

Abstract

An online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS includes a first gas circuit unit, a decomposition product detection unit, a third gas circuit unit, and a gas supply unit. The first gas circuit unit includes a connected CO2 detection module and a H2O detection module. The CO2 detection module's air inlet is connected to the air outlet of the GIS main air chamber, while the H2O detection module's air outlet is connected to the decomposition product detection unit. One end of the third gas circuit unit is connected to the air outlet of the detection unit, and the other end is connected to the air inlet of the GIS main air chamber. Infrared light emitted by the laser light source of the decomposition product detection unit is refracted several times in the reflective air chamber before entering the detector. This device effectively eliminates interference from CO2 and H2O, resulting in more accurate test results and meeting the long optical path requirements of infrared detection.

Description

Technical Field

[0001] The invention belongs to the technical field of high-voltage electrical equipment detection, and relates to an online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS. Background Art

[0002] There are various methods for detecting the decomposition products of SF6 gas, such as gas chromatography, mass spectrometry, infrared detection, photoacoustic spectroscopy, and gas sensors. Gas chromatography and mass spectrometry are suitable for offline detection, featuring accurate detection and high sensitivity. Infrared, photoacoustic spectroscopy, and gas sensors are suitable for online detection, featuring fast detection speeds, and play an important guiding role in the rapid location and detection of on-site faults. Due to the high global warming potential (GMP) of SF6 gas and its life cycle of up to 3,200 years, research on alternative gases to SF6 is gaining increasing attention. Among them, C4F7N is considered one of the most promising alternative gases. A C4F7N / N2 gas mixture can be used as an insulating medium for environmentally friendly GIS. Research on decomposition products under insulation defect conditions plays an important supporting role in fault diagnosis of environmentally friendly alternative gas-insulated equipment.

[0003] Infrared spectroscopy utilizes the principle that there is a linear relationship between the intensity of a substance's absorption of infrared light and its concentration, generating an infrared absorption spectrum to reflect the content of characteristic products. While infrared detection offers advantages such as online detection, it also has limitations. Different substances absorb infrared light of different wavelengths, leading to overlapping absorption peaks in the absorption spectrum and interference. Interference sources include CO2 and H2O, whose absorption peaks overlap significantly with those of the decomposition components of C4F7N. Background gases also interfere with the absorption spectrum. For example, when CO2 is used as a background gas, compared to N2, the absorbance of CO2 in some wavelength bands is saturated, failing to exhibit a consistent pattern. When the proportion of C4F7N in a mixed gas exceeds a certain value, its absorbance in most wavelength bands of the infrared absorption spectrum tends to saturate, making it difficult to detect decomposition products.

[0004] Current research on the decomposition products of C4F7N, the SF6 alternative gas, primarily focuses on simulating the decomposition mechanisms of C4F7N / N2 or C4F7N / CO2 mixtures based on chemical and physical theories. Furthermore, experimental platforms are established to pre-determine specific fault types and utilize existing detection technologies (primarily gas chromatography-mass spectrometry) to qualitatively analyze the gas decomposition characteristics, identifying characteristic products or spectral features that can characterize the fault type. Quantitative research on decomposition products is limited, primarily using experimental data to develop quantitative analysis models. Quantitative analysis of the effects of temperature or pressure on decomposition product content is limited, with more focus on trend analysis. Research on infrared detection of C4F7N / N2 or C4F7N / CO2 mixtures has primarily focused on selecting the wavelengths corresponding to characteristic absorption peaks and using algorithms to improve the accuracy of C4F7N volume fraction detection. Less attention has been paid to the improvement and application of infrared detection devices. Furthermore, to ensure sensitivity and accuracy, the gas cell used in infrared detection must be designed to meet the requirement for a long optical path length, typically achieved by increasing the cell volume. The increase in the space occupied by the gas chamber increases the difficulty of on-site detection and makes it even more difficult to meet the needs of online detection. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides an online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS, thereby solving the technical problems that when the prior art uses infrared spectroscopy to test C4F7N / N2 decomposition products, there is interference between CO2 and H2O. At the same time, when the gas chamber used for infrared detection in the prior art meets the requirement of a longer optical path, the gas chamber volume is large, which increases the difficulty of online detection.

[0006] The present invention is achieved through the following technical solutions:

[0007] An online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS, comprising a first gas path unit, a decomposition product detection unit, a third gas path unit, and a gas supply unit;

[0008] The first gas circuit unit includes a CO2 detection module and a H2O detection module connected to each other. The air inlet of the CO2 detection module is connected to the air outlet of the GIS main air chamber, and the air outlet of the H2O detection module is connected to the decomposition product detection unit.

[0009] One end of the third air path unit is connected to the air outlet of the detection unit, and the other end is connected to the air inlet of the GIS main air chamber;

[0010] One end of the air supply unit is connected to the air source to be supplied, and the other end is connected to the third air path unit;

[0011] The decomposition product detection unit includes a laser light source, a reflective gas chamber and a detector. The laser light source is arranged on one side of the reflective gas chamber, and the detector and the signal acquisition terminal are connected and arranged in sequence on the other side of the reflective gas chamber; the infrared light emitted by the laser light source is refracted several times in the reflective gas chamber and enters the detector.

[0012] Preferably, the first gas circuit unit also includes a first solenoid valve and a first pressure reducing valve connected thereto; the free end of the first solenoid valve is connected to the air outlet of the GIS main air chamber; the free end of the first pressure reducing valve is connected to the CO2 detection module.

[0013] Preferably, the online detection device further comprises a second air path unit, one end of which is connected to the air outlet of the GIS main air chamber, and the other end of which is connected to the air inlet of the decomposition product detection unit.

[0014] Preferably, the second gas circuit unit includes a second pressure reducing valve, a first pressure sensor and a regulating valve that are connected together; the high-pressure end of the second pressure reducing valve is connected to the air outlet of the GIS main air chamber, and the air outlet of the regulating valve is connected to the air inlet of the decomposition product detection unit; the air outlet of the H2O detection module is arranged between the second pressure reducing valve and the first pressure sensor.

[0015] Preferably, the online detection device further comprises a three-way stopcock; the three interfaces of the three-way stopcock are respectively connected to the air outlet of the GIS main air chamber, the high-pressure end of the second pressure reducing valve and the air outlet of the third air circuit unit.

[0016] Preferably, a fiber optic collimator is further provided on one side of the reflective air chamber, and the laser light source is connected to the fiber optic collimator; a fiber optic splitter is further provided on the other side of the reflective air chamber, and the detector is connected to the fiber optic splitter.

[0017] Preferably, the reflective air chamber is also connected to a second pressure sensor and a constant temperature device.

[0018] Preferably, the third air circuit unit includes a booster pump and a third pressure sensor connected thereto; the low-pressure end of the booster pump is connected to the air outlet of the decomposition product detection unit, and the high-pressure end of the booster pump is connected to the air inlet of the GIS main air chamber; the third pressure sensor is arranged between the high-pressure end of the booster pump and the air inlet of the GIS main air chamber.

[0019] Preferably, an exhaust gas treatment device is further provided between the decomposition product detection unit and the booster pump.

[0020] Preferably, the air supply unit includes an air supply device and a second solenoid valve that are connected to each other; the air outlet of the second solenoid valve is connected to the low-pressure end of the booster pump.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] An online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS is provided with a CO2 detection module and an H2O detection module. During the test process, the interference of CO2 and H2O can be effectively eliminated, making the test results more accurate. At the same time, in the decomposition product detection unit, the infrared light emitted by the laser light source is refracted several times in the reflective gas chamber and enters the detector, effectively meeting the requirement for a long optical path in infrared detection. The provision of the gas replenishment unit ensures that the tested gas meets the mixing ratio requirement of the C4F7N / N2 mixed gas, effectively realizing online gas detection.

[0023] Furthermore, the provision of the first solenoid valve and the first pressure reducing valve makes the control of the testing process more convenient and effective.

[0024] Furthermore, the setting of the second gas circuit unit can effectively determine the impact of the test process of the CO2 detection module and the H2O detection module on the decomposition product test results during the test.

[0025] Furthermore, the setting of the three-way stopcock makes the connection of the device gas circuit and the switching control of the gas circuit during the test process more convenient and effective.

[0026] Furthermore, the fiber collimator can convert the light from the laser light source into parallel light, so that the light path in the reflective gas chamber satisfies the law of reflection and the optimal reflection path can be obtained through design and optimization.

[0027] Furthermore, the provision of the second pressure sensor and the constant temperature device makes it more convenient to control the constant temperature and pressure process of the reflective air chamber during the test.

[0028] Furthermore, the setting of the booster pump effectively ensures that the pressure of the gas after the test meets the requirements when it returns.

[0029] Furthermore, the exhaust gas treatment device effectively treats the exhaust gas produced during the test, namely the gas decomposition products and some residual interfering gases.

[0030] The accompanying drawings further illustrate:

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 The figure is a schematic structural diagram of an online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS in the present invention.

[0033] Among them: 1. GIS main gas chamber, 2. First solenoid valve, 3. First pressure reducing valve, 4. CO2 detection module, 5. H2O detection module, 6. First pressure sensor, 7. Control valve, 8. Reflective gas chamber, 9. Second pressure sensor, 10. Fiber optic splitter, 11. Detector, 12. Signal acquisition terminal, 13. Exhaust gas treatment device, 14. Constant temperature device, 15. Second solenoid valve, 16. Gas supply device, 17. Fiber optic collimator, 18. Laser light source, 19. Booster pump, 20. Second pressure reducing valve, 21. Third pressure sensor, 22. Three-way stopcock. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0036] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0037] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0039] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0040] The present invention is described in further detail below with reference to the accompanying drawings:

[0041] like Figure 1As shown, an online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS includes a first gas circuit unit, a decomposition product detection unit, a third gas circuit unit and an air supply unit; the first gas circuit unit includes a CO2 detection module 4 and a H2O detection module 5 connected together, the air inlet of the CO2 detection module 4 is connected to the air outlet of the GIS main air chamber 1, and the air outlet of the H2O detection module 5 is connected to the decomposition product detection unit; in addition, the first gas circuit unit also includes a first solenoid valve 2 and a first pressure reducing valve 3 connected together; the free end of the first solenoid valve 2 is connected to the air outlet of the GIS main air chamber 1; the free end of the first pressure reducing valve 3 is connected to the CO2 detection module 4; one end of the third gas circuit unit is connected to the air outlet of the detection unit, and the other end is connected to the GI The air inlet of the S main air chamber 1 is connected; one end of the air supply unit is connected to the air source to be supplied, and the other end is connected to the third air path unit. The decomposition product detection unit includes a laser light source 18, a reflective air chamber 8, and a detector 11. The laser light source 18 is located on one side of the reflective air chamber 8, and the detector 11 and the signal acquisition terminal 12 are connected to the other side of the reflective air chamber 8 in sequence. The infrared light emitted by the laser light source 18 is refracted several times in the reflective air chamber 8 and enters the detector 11. In addition, a fiber optic collimator 17 is also located on one side of the reflective air chamber 8, and the laser light source 18 is connected to the fiber optic collimator 17. A fiber optic splitter 10 is also located on the other side of the reflective air chamber 8, and the detector 11 is connected to the fiber optic splitter 10. To achieve constant temperature and pressure control of the reflective air chamber 8 during the test, a second pressure sensor 9 and a constant temperature device 14 are also connected to the reflective air chamber 8. The air supply unit includes an air supply tank 16 and a second solenoid valve 15 that are connected to each other; the air outlet of the second solenoid valve 15 is connected to the low-pressure end of the booster pump 19.

[0042] In another preferred embodiment of the present invention, the online detection device further includes a second gas circuit unit, one end of which is connected to the outlet of the GIS main gas chamber 1 and the other end is connected to the inlet of the decomposition product detection unit. Further preferably, the second gas circuit unit includes a second pressure reducing valve 20, a first pressure sensor 6, and a regulating valve 7. The high-pressure end of the second pressure reducing valve 20 is connected to the outlet of the GIS main gas chamber 1, and the outlet of the regulating valve 7 is connected to the inlet of the decomposition product detection unit. The outlet of the H2O detection module 5 is located between the second pressure reducing valve 20 and the first pressure sensor 6. In the present invention, gas circuit switching is achieved via a three-way stopcock 22, the three ports of which are respectively connected to the outlet of the GIS main gas chamber 1, the high-pressure end of the second pressure reducing valve 20, and the outlet of the third gas circuit unit.

[0043] In another preferred embodiment of the present invention, the third gas circuit unit includes a booster pump 19 and a third pressure sensor 21. The low-pressure end of the booster pump 19 is connected to the outlet of the decomposition product detection unit, and the high-pressure end of the booster pump 19 is connected to the inlet of the GIS main air chamber 1. The third pressure sensor 21 is installed between the high-pressure end of the booster pump 19 and the inlet of the GIS main air chamber 1. Furthermore, an exhaust gas treatment device 13 is installed between the decomposition product detection unit and the booster pump 19.

[0044] The present invention designs an online detection device for the decomposition products of a C4F7N / N2 mixed gas, suitable for environmentally friendly GIS. The device reduces interference from interference sources and background gases through the coordination of a sensor and a solenoid valve. A reflective gas chamber is also designed to further minimize infrared light energy loss caused by excessive reflections. Specifically, the device comprises: solenoid valves (a first solenoid valve 2 and a second solenoid valve 15), pressure reducing valves (a first pressure reducing valve 3 and a second pressure reducing valve 20), pressure sensors (a first pressure sensor 6, a second pressure sensor 9, and a third pressure sensor 21), a reflective gas chamber 8, a laser light source 18, a fiber splitter 10, a fiber collimator 17, a signal acquisition terminal 12, and a booster pump 19. The device consists of a GIS main gas chamber 1, a first solenoid valve 2, a first pressure reducing valve 3, a CO2 detection module 4, a H2O detection module 5, a first pressure sensor 6, and a regulating valve 7, all connected in series to a reflective gas chamber 8. A laser light source 18 emits infrared light, which is corrected by a fiber collimator 17. After reflection within the reflective gas chamber 8, the light is received by a fiber splitter 10. The optical signal is converted into an electrical signal by a detector 11 and transmitted to a signal acquisition terminal 12, which stores and analyzes the data and processes it to produce an infrared spectrum of the gas decomposition products. After passing through the gas chamber and receiving gas replenishment from an exhaust gas treatment device 13 and a gas replenishment device 16, the measured gas is returned to the GIS main gas chamber 1 via a three-way stopcock 22, driven by a booster pump 19. The high-pressure end of a second pressure reducing valve 20 is connected to the three-way stopcock 22, while the low-pressure end is connected between the H2O detection module 5 and the first pressure sensor 6.

[0045] The operation process of online detection of decomposition products of C4F7N / N2 mixed gas in the present invention includes:

[0046] Detection Operation 1: By opening the first solenoid valve 2 and regulating valve 7 and controlling the first pressure-reducing valve 3, the measured gas, after being depressurized, passes through the CO2 detection module 4 and the H2O detection module 5 to measure the CO2 and H2O concentrations, respectively. After the flow rate is adjusted by the regulating valve 7, it enters the reflective gas chamber 8. A pressure sensor 9 and a thermostat 14 maintain constant temperature and pressure. A laser light source 18 outputs infrared light, which is converted into parallel light by a fiber collimator 17. After five reflections in the gas chamber, it is received by the fiber splitter 10. The detector 11 detects the optical signal transmitted by the optical fiber and converts it into an electrical signal. The signal acquisition terminal 12 determines the type and concentration of the gas in the gas chamber. Simultaneously, the measured gas is treated by the exhaust gas treatment device 13 and the gas replenishment device 16 to meet the requirements for the C4F7N / N2 mixed gas ratio. After being pressurized by the booster pump 19, the three-way stopcock 22 is operated to allow the gas to flow back to the equipment through the outlet, achieving online gas detection.

[0047] Test Operation 2: By operating the three-way stopcock 22, the measured gas passes through the second pressure-reducing valve 20 and enters the reflective gas chamber 8. The signal acquisition terminal 12 obtains the types and concentrations of the decomposition products of the original gas, which have not been detected by the CO2 detection module 4 and the H2O detection module 5. After passing through the exhaust gas treatment device 13 and the air supply device 16, the gas is pressurized and returned to the equipment. This operation can be used to determine the impact of the absorption of the measured gas by the CO2 detection module 4 and the H2O detection module on the test results.

[0048] Detection operation three: Connect the GIS main gas chamber 1 to gas tanks with different C4F7N / N2 mixing ratios, and enter the reflective gas chamber 8 through the three-way stopcock 22 and the second pressure reducing valve 20. The signal acquisition terminal 12 obtains the infrared absorption reference spectrum of gases with different C4F7N / N2 mixing ratios. Similarly, the mixed gas is recovered.

[0049] This device uses operations one and two to determine the concentrations of trace amounts of CO2 and H2O. Based on the Lambert-Beer law, which states that absorbance is proportional to gas concentration under constant temperature and pressure, comparative analysis of the spectra from operations one and two reveals the interference of CO2 and H2O on the absorption spectrum of the decomposition products of the C4F7N / N2 gas mixture, as well as the loss of product content caused by adsorption of gas components by the detection unit. Operation three allows for the study of the varying effects of varying C4F7N proportions in the gas mixture on the infrared absorption spectrum.

[0050] Furthermore, the present invention is explained through specific operations 1 to 3:

[0051] Test Operation 1: C₄FₐN / N₂ gas at a pressure of 0.5 MPa, with C₄FₐN comprising 6%, is drawn from the GIS main gas chamber. The first pressure reducing valve reduces the pressure to 0.15 MPa. The pressure in the chamber is maintained at 0.15 MPa using the regulating valve 7 and the first pressure sensor 6. The gas flows through the reflective gas chamber 8, where it absorbs infrared light, before entering the exhaust gas treatment device 13. The concentration of its main decomposition products, after adsorption by the adsorbent, meets the impurity content requirement under normal operating conditions. Due to pipeline leakage and absorption, the pressure in the main detection pipeline is less than 0.15 MPa. The gas replenishment device 16 is connected to the main detection pipeline via a one-way valve. Pure C₄FₐN gas within the device is added to the gas being tested until the pressure reaches equilibrium, effectively replacing any C₄FₐN lost during the test. N₂ is chemically stable and roughly matches the amount of C₄FₐN leaked from the pipeline. Therefore, ignoring pipeline leakage, online detection of the C₄FₐN / N₂ mixture is possible. After the air is replenished, the mixed gas is pressurized to 0.5 MPa by the booster pump and then flows back to the outlet through the three-way stopcock.

[0052] Detection operation 2: Draw out C4F7N / N2 gas at a pressure of 0.5MPa from the GIS main gas chamber, reduce the pressure to 0.15MPa through the second pressure reducing valve, and maintain a constant temperature and pressure state in the reflective gas chamber 8. After infrared detection and exhaust gas treatment, the gas is replenished to the pressure balance on both sides of the one-way valve, and then pressurized to 0.5MPa and flows back to the equipment. There is no need to re-replenish the gas after the test.

[0053] Test Operation Three: The GIS main gas chamber is connected to C4F7N and N2 cylinders via a mixed gas distributor, outputting C4F7N / N2 mixed gases with gas distribution ratios of 2%, 4%, 6%, 8%, and 10%. After each gas introduction and circulation for a specified period, the reflective chamber is maintained at a constant temperature and pressure. The laser light source is then activated for infrared detection, and the signal acquisition terminal stores the spectrum and test run data. After changing the gas distribution ratio, continuous ventilation is performed for a period of time, known as a purge, to minimize the impact of residual gas on the mixture ratio. During this purge phase, the gas outlet is connected to a collection tank to prevent residual gas from introducing impurities into the pure gas in the cylinder, potentially reducing purity.

[0054] Taking detection operation 1 as an example, the detection steps of the decomposition products of C4F7N / N2 mixed gas are as follows:

[0055] S1. Start the first solenoid valve 2 and the first pressure reducing valve 3, pre-start the CO2 detection module 4 and the H2O detection module 5, set the gas chamber to constant temperature and pressure, start the second solenoid valve 15, the booster pump 19 and the three-way stopcock 22, and put the signal acquisition terminal 12 into a ready state;

[0056] S2, connect the GIS main air chamber 1 and the first solenoid valve 2;

[0057] S3. After a certain period of ventilation, the laser light source 18 is activated to emit infrared light. The fiber collimator 17 converts the infrared light into parallel light. After five reflections in the gas chamber, the light is received by the fiber splitter 10. The optical signal transmitted by the optical fiber is detected by the detector 11 and converted into an electrical signal. The signal acquisition terminal 12 obtains the type and concentration of the gas in the gas chamber.

[0058] S4, after the detection is completed, the laser light source 18 is turned off and the next detection operation is waited for;

[0059] S5. The gas to be tested enters the detection pipeline, and the detection process is the same as S3.

[0060] S6. Complete the second and third detection operations, and the detection ends.

[0061] In a preferred embodiment of the present invention, the regulating valve can be an electric regulating valve, and the pressure reducing valve is a direct-acting pressure reducing valve. The reflective gas chamber 8 has a rectangular cross-section, measuring 30 mm in length and 20 mm in width. The angle between the output light from the fiber collimator 17 and the horizontal is 74.23°. After correction by the collimator 17, the total optical path length of the infrared beam within the chamber reaches 108.32 mm, meeting the optical path length requirement of 100 mm. The laser light source is configured to emit laser light with a wavelength of 2.0 μm to 5.0 μm. Furthermore, the inner wall of the reflective gas chamber 8 is preferably coated with a high-reflectivity aluminum film. The aluminum oxide formed on the surface has a low adsorption energy when interacting with C₄FₐN, thereby reducing the absorption of infrared light by the reflective surface material. The air inlet and outlet of the GIS main gas chamber 1 are respectively connected to two pipes of a three-way stopcock 22, allowing for simultaneous input of the measured gas from the C₄FₐN / N₂ mixed gas device and return of the gas to the device. The gas filled in the gas supply device is pure C4F7N gas. By setting the air pressure in the gas supply tank, the pure C4F7N gas is quantitatively added to the measured gas to maintain the air pressure balance on both sides of the one-way valve.

[0062] In another preferred embodiment of the present invention, CF4, CF3CN, C2F4, and C3F6, which are decomposition products of C4F7N / N2 under local overheating fault conditions, are selected as detection gases, wherein the characteristic absorption peak band of CF4 is 1210-1250 cm -1 The characteristic absorption peak band of CF3CN is 1150~1190cm -1 The characteristic absorption peak of C2F4 is in the range of 1300-1340 cm -1 The characteristic absorption peak of C3F6 is in the range of 1780-1820 cm -1 The tail gas treatment device is equipped with a main decomposition product adsorbent, which uses a molecular sieve adsorbent with a significant adsorption effect on the main decomposition products to achieve the C4F7N / N2 component content standard under normal operating conditions.

[0063] The CO2 detection module utilizes optical waveguide technology, resulting in a compact design and ease of manufacture. The H2O detection module incorporates a humidity sensor composed of polymer film capacitors. Based on the principle that the dielectric constant of polymer materials varies significantly with water absorption, this sensor offers high precision and sensitivity.

[0064] Compared with existing technologies, the present invention can reduce the interference of CO2 and H2O on infrared absorption spectra, quantitatively analyze the impact of different C4F7N ratios on infrared spectrum band selection, and simultaneously achieve online detection of C4F7N / N2 mixed gas decomposition products and online gas recovery, making it suitable for rapid on-site testing. The reflective gas chamber is compact while ensuring the optical path length, which helps to achieve gas chamber miniaturization. At the same time, reducing the number of reflections can further reduce the energy loss of the infrared beam during the reflection process, reducing the impact of energy attenuation caused by reflection on infrared light intensity, and thus reducing the measurement error of the product concentration corresponding to the absorption peak in the infrared spectrum.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS, characterized by: It includes a first gas circuit unit, a decomposition product detection unit, a third gas circuit unit and a gas supply unit; The first gas circuit unit comprises a CO2 detection module (4) and a H2O detection module (5) which are connected to each other, the air inlet of the CO2 detection module (4) being connected to the air outlet of the GIS main air chamber (1), and the air outlet of the H2O detection module (5) being connected to the decomposition product detection unit; One end of the third air path unit is connected to the air outlet of the detection unit, and the other end is connected to the air inlet of the GIS main air chamber (1); One end of the air supply unit is connected to the air source to be supplied, and the other end is connected to the third air path unit; The decomposition product detection unit comprises a laser light source (18), a reflective gas chamber (8), and a detector (11), wherein the laser light source (18) is arranged on one side of the reflective gas chamber (8), and the detector (11) and the signal acquisition terminal (12) are sequentially connected and arranged on the other side of the reflective gas chamber (8); infrared light emitted by the laser light source (18) is refracted several times in the reflective gas chamber (8) and enters the detector (11); The online detection device further comprises a second gas path unit, one end of which is connected to the gas outlet of the GIS main gas chamber (1), and the other end of which is connected to the gas inlet of the decomposition product detection unit; The second gas circuit unit comprises a second pressure reducing valve (20), a first pressure sensor (6) and a regulating valve (7) which are connected to each other; the high-pressure end of the second pressure reducing valve (20) is connected to the gas outlet of the GIS main gas chamber (1), and the gas outlet of the regulating valve (7) is connected to the gas inlet of the decomposition product detection unit; the gas outlet of the H2O detection module (5) is arranged between the second pressure reducing valve (20) and the first pressure sensor (6).

2. The online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS according to claim 1, characterized in that: The first gas circuit unit further comprises a first solenoid valve (2) and a first pressure reducing valve (3) which are connected to each other; the free end of the first solenoid valve (2) is connected to the gas outlet of the GIS main gas chamber (1); and the free end of the first pressure reducing valve (3) is connected to the CO2 detection module (4).

3. The online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS according to claim 1, characterized in that: The online detection device further comprises a three-way stopcock (22); the three interfaces of the three-way stopcock (22) are respectively connected to the gas outlet of the GIS main gas chamber (1), the high-pressure end of the second pressure reducing valve (20), and the gas outlet of the third gas circuit unit.

4. The online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS according to claim 1, characterized in that: A fiber collimator (17) is further provided on one side of the reflective air chamber (8), and the laser light source (18) is connected to the fiber collimator (17); a fiber splitter (10) is further provided on the other side of the reflective air chamber (8), and the detector (11) is connected to the fiber splitter (10).

5. The online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS according to claim 1, characterized in that: The reflective air chamber (8) is also connected to a second pressure sensor (9) and a constant temperature device (14).

6. The online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS according to claim 1, characterized in that: The third gas circuit unit comprises a booster pump (19) and a third pressure sensor (21) which are connected and arranged; the low-pressure end of the booster pump (19) is connected and arranged with the gas outlet of the decomposition product detection unit, and the high-pressure end of the booster pump (19) is connected and arranged with the gas inlet of the GIS main gas chamber (1); the third pressure sensor (21) is arranged between the high-pressure end of the booster pump (19) and the gas inlet of the GIS main gas chamber (1).

7. The online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS according to claim 6, characterized in that: An exhaust gas treatment device (13) is also provided between the decomposition product detection unit and the booster pump (19).

8. The online detection device for C4F7N / N2 decomposition products suitable for environmentally friendly GIS according to claim 6, characterized in that: The air supply unit comprises an air supply device (16) and a second electromagnetic valve (15) which are connected to each other; the air outlet of the second electromagnetic valve (15) is connected to the low-pressure end of the booster pump (19).

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