SF6 decomposer measuring system and method based on multi-optical-path double-resonant-cavity photoacoustic spectrometry

Abstract

The invention belongs to the technical field of photoacoustic spectrometry gas detection, and particularly discloses an SF6 decomposer measuring system and method based on a multi-optical-path double-resonant-cavity photoacoustic spectrometry. The system comprises an infrared light source and a photoacoustic cell, the infrared light source is an infrared blackbody radiation source, the infrared blackbody radiation source is used for generating infrared light with continuous wavelength, and the infrared blackbody radiation source is connected with an infrared optical fiber through an infrared light processing unit; the photoacoustic cell comprises a to-be-detected gas buffer cavity and double resonant cavities; a reflection unit for increasing the infrared light distance is arranged in the to-be-detected gas buffer cavity; the double resonant cavities are used for amplifying the photoacoustic signals and transmitting the photoacoustic signals to the computer system. According to the SF6 decomposer measurement system and method based on the multi-optical-path double-resonant-cavity photoacoustic spectrometry, multi-component gas in the SF6 decomposer can be measured, the cost is lower, the optical path of infrared light can be increased, the photoacoustic action effect can be improved, and then the gas measurement sensitivity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photoacoustic spectroscopy gas detection, and in particular to a system and method for measuring SF6 decomposition products based on multi-optical path double-resonance cavity photoacoustic spectroscopy. Background Art

[0002] Transformer oil in power systems is susceptible to aging and produces some low-molecular hydrocarbon compounds after being affected by electricity and heat. Gas chromatography and electrochemical sensing are currently commonly used to detect these compounds. Gas chromatography requires the use of expensive gas chromatographs, and online detection cannot be achieved because the chromatographic column needs to be replaced and cleaned; electrochemical sensing has problems such as low measurement accuracy and severe cross-interference. At present, spectral measurement technology represented by photoacoustic spectroscopy has developed rapidly and has become an important means of trace gas measurement.

[0003] The light source of the existing photoacoustic spectroscopy generally uses a tunable laser or laser. The price of a tunable laser is generally expensive. The wavelength of an ordinary infrared laser is fixed and expensive, making it difficult to achieve the requirements for multi-component gas measurement. The photoacoustic cell is the core device for photoacoustic spectroscopy measurement. At present, it is usually a "straight" photoacoustic cell, an "H-type" photoacoustic cell, and a "T-type" photoacoustic cell. The existing photoacoustic cells are divided into two types: resonant and non-resonant. Due to the shortcomings of the non-resonant photoacoustic cell, such as low gas detection sensitivity and poor resistance to environmental interference, its application is limited. The resonant photoacoustic cell has the advantages of high sensitivity and strong noise suppression, so its system detection limit is better and it is widely used in trace gas detection.

[0004] At present, the beam incident windows of the existing photoacoustic cell are usually located at both ends of the cylinder, the effective optical path is relatively short, and the photoacoustic signal is weak; secondly, the current single resonant cavity structure has a weak effective photoacoustic signal for the measurement of trace gases with weak photoacoustic signals. Therefore, it is necessary to design a new photoacoustic spectroscopy measurement device to enable it to achieve: 1. Multi-component gas testing requirements; 2. Infrared multi-optical path requirements to effectively improve the photoacoustic interaction effect; 3. Enhance the resonance effect to achieve high measurement sensitivity. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a SF6 decomposition product measurement system and method based on multi-optical path dual-resonance cavity photoacoustic spectroscopy, which can measure multi-component gases in SF6 decomposition products, has lower cost, can increase the optical path of infrared light, improve the photoacoustic effect, and thus improve the gas measurement sensitivity.

[0006] The present invention adopts the following technical solution.

[0007] In the first aspect, the present invention provides an SF6 decomposition product measurement system based on multi-optical path dual-resonance cavity photoacoustic spectroscopy, comprising: an infrared light source and a photoacoustic cell, wherein the infrared light source is an infrared blackbody radiation source, which is used to generate continuous wavelength infrared light based on the blackbody radiation principle, and the infrared blackbody radiation source is connected to the infrared optical fiber through an infrared light processing unit; the photoacoustic cell comprises a gas buffer cavity to be measured and a dual-resonance cavity; the gas buffer cavity to be measured is arranged on a side of the infrared optical fiber away from the infrared light processing unit, and an infrared window is arranged at a position opposite to the infrared light injection position; a reflection unit for increasing the infrared optical path is arranged inside the gas buffer cavity to be measured; the dual-resonance cavity is symmetrically arranged on opposite sides of the gas buffer cavity to be measured, and both are connected to the inside of the gas buffer cavity to be measured, and the dual-resonance cavity is used to amplify the photoacoustic signal, and transmit the photoacoustic signal to the computing and processing system, and calculate the concentration of SF6 decomposition products based on the photoacoustic signal.

[0008] Preferably, the reflection unit comprises two arc-shaped infrared reflectors arranged opposite to each other, wherein the back side of one of the arc-shaped infrared reflectors faces the infrared window, and the arc-shaped infrared reflector is provided with micro-holes for infrared light to pass through at positions corresponding to infrared light incident positions.

[0009] Preferably, each of the resonant cavities is provided with a built-in microphone; the built-in microphone transmits the acoustic signal generated by the gas to be measured absorbing infrared light to the computing and processing system through a filter amplifier, a phase-locked amplifier and a data acquisition card.

[0010] Preferably, the infrared light processing unit comprises: a chopper and a plurality of sets of infrared bandpass filters; the infrared blackbody radiation source, the chopper, the plurality of sets of infrared bandpass filters and the infrared optical fiber are connected in sequence.

[0011] Preferably, an infrared light collimator is further provided between the infrared optical fiber and the infrared window; the infrared light collimator is used to direct the infrared light entering the infrared optical fiber vertically toward the infrared window.

[0012] Preferably, the system further comprises: a power supply controller connected to the infrared black body radiation source, and used for regulating the wavelength of infrared light radiated by the infrared black body radiation source by controlling the magnitude of the current.

[0013] Preferably, the buffer chamber for the gas to be measured is provided with a buffer chamber air inlet, the buffer chamber air inlet is provided with an air inlet mass flowmeter, and the buffer chamber air inlet is used to be connected to a source of the gas to be measured.

[0014] Preferably, a buffer chamber gas outlet is provided at the bottom of the gas buffer chamber to be measured, and the buffer chamber gas outlet is connected to the tail gas collector.

[0015] Preferably, the buffer chamber air outlet is provided with an air outlet mass flow meter.

[0016] In a second aspect, the present invention provides a method for measuring SF6 decomposition products based on multi-path double-resonance cavity photoacoustic spectroscopy, using the aforementioned SF6 decomposition product measurement system based on multi-path double-resonance cavity photoacoustic spectroscopy, comprising the following steps:

[0017] Using an infrared blackbody radiation source to emit infrared light of continuous wavelength, and periodically modulating the infrared light to obtain infrared light of a set wavelength;

[0018] The modulated infrared light source enters the gas buffer chamber to be measured and is reflected multiple times inside the gas buffer chamber to be measured;

[0019] The SF6 gas to be tested is introduced into the gas buffer chamber to be tested. Each component in the decomposition product of the SF6 gas absorbs infrared light of a specific wavelength, and the optical signal is converted into an acoustic signal.

[0020] The double resonant cavity is used to amplify the acoustic wave signal inside the gas buffer cavity to be measured, and the acoustic wave signal is transmitted to the computing and processing system;

[0021] The calculation and processing system extracts the average value of the received sound wave signal and calculates the concentration of each component in the SF6 decomposition product.

[0022] The beneficial effect of the present invention is that, compared with the prior art, the present invention provides an SF6 decomposition product measurement system based on multi-optical path dual-resonance cavity photoacoustic spectroscopy, and by adopting a black body infrared radiation light source, continuous wavelength infrared light can be obtained, and at the same time, the infrared light generated by its radiation can be processed by an infrared light processing unit to obtain periodically modulated infrared light of a specific wavelength, which is applied to the photoacoustic spectroscopy technology, and utilizes the different absorption intensities of different components in the decomposition products of SF6 gas in infrared light of different wavelengths. By modulating infrared light of different wavelengths, the measurement requirements of multi-component gases decomposed from SF6 gas are achieved, and compared with traditional tunable infrared lasers, a significant price reduction is achieved.

[0023] In addition, the present invention sets a reflection unit in the photoacoustic cell, and the infrared light entering the photoacoustic cell is reflected back and forth multiple times inside the reflection unit, which effectively increases the optical path of the infrared light, enhances the interaction intensity between the infrared light and the measured gas, obtains a larger excitation signal, and enables the photoacoustic signal to be multiply amplified in the dual resonant cavity, thereby improving the sensitivity of the photoacoustic system.

[0024] At the same time, the present invention uses a completely consistent dual-resonance cavity system, which can reduce the measurement error caused by environmental factors by averaging, making the system more resistant to noise and further improving the sensitivity of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1It is a schematic diagram of the SF6 decomposition product measurement system based on multi-optical path double-resonance cavity photoacoustic spectroscopy in the present invention.

[0026] Reference numerals in the figures:

[0027] 1: power controller; 2: infrared blackbody radiation source; 3: chopper; 4: multiple sets of infrared bandpass filters; 5: infrared optical fiber; 6: infrared light collimator; 7: buffer cavity air inlet; 8: infrared window; 9: micropore; 10: curved infrared reflector; 11: red light; 12: first resonant cavity; 13: first microphone; 14: second resonant cavity; 15: first microphone; 16: buffer cavity for gas to be measured; 17: buffer cavity air outlet; 18: air outlet mass flow meter; 19: mechanical pump; 20: tail gas collector; 21: filter amplifier; 22: phase-locked amplifier; 23: data acquisition card; 24: computer display terminal; 25: air inlet mass flow meter; 26: source of gas to be measured. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0029] like Figure 1 As shown, Example 1 of the present invention discloses a multi-optical path dual-resonance cavity photoacoustic spectroscopy system for measuring SF6 gas decomposition products, including: an infrared blackbody radiation source 2, a chopper 3, multiple groups of infrared bandpass filters 4, an infrared optical fiber 5 and a photoacoustic cell.

[0030] The infrared blackbody radiation source 2 is used as a light source, and a continuous wavelength infrared light source can be obtained by using the blackbody radiation principle. The infrared blackbody radiation source 2 is connected to the power controller 1, and the temperature of the infrared blackbody radiator is regulated by the current of the power controller 1. The temperature of the infrared blackbody radiation source is regulated according to the current, and a continuous wavelength infrared light is obtained by using the blackbody radiation principle.

[0031] The chopper 3 and multiple groups of infrared bandpass filters 4 constitute an infrared light processing unit. The infrared blackbody radiation source 2, the chopper 3, and multiple groups of infrared bandpass filters 4 are connected in sequence. The infrared light radiated by the infrared blackbody radiation source 2 is processed by the chopper 3 and multiple groups of infrared bandpass filters 4 in sequence to obtain infrared light of a specific wavelength that is periodically modulated. Different components in the decomposition product of SF6 gas have different absorption intensities in infrared light of different wavelengths. By modulating the infrared light of the required set wavelength by the infrared light processing unit, it is convenient to detect different components in the decomposition product of SF6.

[0032] The photoacoustic cell includes a double resonant cavity and a gas buffer cavity 16 to be measured, and an infrared window 8 for infrared light to pass through is arranged on the left side of the gas buffer cavity 16 to be measured. One end of the infrared optical fiber 5 is connected to multiple groups of infrared bandpass filters 4, and the other end is connected to an infrared light collimator 6. The infrared light collimator 6 is used to vertically direct the infrared light entering the infrared optical fiber 5 toward the infrared window 8, and enter the photoacoustic cell through the infrared window 8.

[0033] The dual resonant cavity includes a first resonant cavity 12 and a second resonant cavity 14 with completely identical structures and sizes. The first resonant cavity 12 and the second resonant cavity 14 are respectively located on the upper and lower sides of the gas buffer cavity 16 to be measured, and are symmetrically placed. The first resonant cavity 12 and the second resonant cavity 14 are respectively equipped with a first microphone 13 and a second microphone 15 for amplifying the photoacoustic signal and transmitting the photoacoustic signal to a computing and processing system. The embodiment of the present invention is preferably a computer terminal system, which calculates the concentration of each component in the SF6 decomposition product based on the photoacoustic signal.

[0034] Furthermore, a buffer chamber air inlet 7 is provided at the top of the gas buffer chamber 16 to be tested, and the buffer chamber air inlet 7 is provided with an air inlet mass flowmeter 25 and is connected to the gas source 26 to be tested. The gas source 26 to be tested released by the gas source 26 to be tested passes through the air inlet mass flowmeter 25 and the buffer chamber air inlet 7 and enters into the gas buffer chamber 16 to be tested.

[0035] A reflection unit for increasing the infrared optical path is provided inside the gas buffer chamber 16 to be measured, and the reflection unit includes two arc-shaped infrared reflectors 10 arranged opposite to each other, and the back of one of the arc-shaped infrared reflectors 10 faces the infrared window 8, and the arc-shaped infrared reflector 10 corresponds to the infrared window 8, and a micro-hole 9 for infrared light to pass through is provided at a position perpendicular to the infrared light. The infrared light entering the photoacoustic cell passes through the micro-hole 9 of the arc-shaped infrared reflector 10, and is reflected multiple times between the two arc-shaped infrared reflectors 10, which effectively increases the optical path of the infrared light, and at the same time increases the optical path inside the photoacoustic cell, which enhances the photoacoustic effect between the strong infrared light and the gas to be measured, and significantly improves the sensitivity of the photoacoustic spectrum measurement.

[0036] The gas to be measured inside the gas buffer chamber 16 absorbs the infrared light of the characteristic frequency after periodic modulation, and converts the optical information into an acoustic wave signal, which is detected by the built-in first microphone 13 and second microphone 15. The photoacoustic cell has two completely identical resonant cavities and microphones built in, and takes the average of the two completely identical microphone signals, thereby reducing the measurement error and background noise, and further improving the sensitivity of the photoacoustic spectroscopy measurement.

[0037] The first microphone 13 and the second microphone 15 are both connected to the filter amplifier 21, and the filter amplifier 21, the phase-locked amplifier 22, the data acquisition card 23 and the computer display terminal 24 are connected in sequence. The two microphones filter and amplify the detected electrical signals through the filter amplifier 21, and then enter the phase-locked amplifier 22, extract the average value, and then enter the data acquisition card 23, and finally enter the computer display terminal 24, and complete the operation and concentration calculation of the photoacoustic signal through the computer terminal system, so as to achieve accurate measurement of SO2F2, SO2F4, SOF2, SO2, and HF, the characteristic products of SF6 gas decomposition.

[0038] In a preferred but non-limiting embodiment of the present invention, a buffer chamber outlet 17 is provided at the bottom of the gas buffer chamber 16 to be tested, and the buffer chamber outlet 17 is provided with an outlet mass flowmeter 18. After the buffer chamber outlet 17 passes through the outlet mass flowmeter 18, it is connected to the exhaust gas collector 20 through a mechanical pump 19, so that the exhaust gas obtained from the test can be collected and the exhaust gas mass flow can be monitored.

[0039] Embodiment 2 of the present invention provides a method for measuring SF6 gas decomposition products by multi-light-path dual-resonance cavity photoacoustic spectroscopy, using the multi-light-path dual-resonance cavity photoacoustic spectroscopy system for measuring SF6 gas decomposition products in Embodiment 1, the method comprises the following steps:

[0040] Step 1: using an infrared black body radiation source 2 to emit infrared light of a continuous wavelength, and periodically modulating the infrared light to obtain infrared light of a set wavelength;

[0041] Step 2, the modulated infrared light source enters the gas buffer chamber 16 to be measured of the photoacoustic cell, and is reflected multiple times inside the gas buffer chamber 16 to be measured, which significantly increases the optical path of the infrared light;

[0042] Step 3: The SF6 gas to be tested is introduced into the gas buffer chamber to be tested. Each component in the decomposition product of the SF6 gas absorbs infrared light of a specific wavelength, and converts the optical information into an acoustic wave signal.

[0043] Step 4: using two built-in microphones in the dual resonant cavity to absorb the sound wave signal inside the gas buffer cavity to be measured, processing the sound wave signal, and transmitting the sound wave signal to the computer terminal system;

[0044] Step 5: The computer terminal system extracts the average value of the received sound wave signal and completes the operation of the photoacoustic signal to calculate the concentration of each component in the decomposition product of SF6 gas.

[0045] The beneficial effect of the present invention is that, compared with the prior art, the present invention provides a SF6 decomposition product measurement system based on multi-optical path dual-resonance cavity photoacoustic spectroscopy. By adopting a blackbody infrared radiation light source, continuous wavelength infrared light can be obtained. At the same time, the infrared light generated by its radiation can be processed by an infrared light processing unit to obtain periodically modulated infrared light of a specific wavelength. When applied to the photoacoustic spectroscopy technology, the different absorption intensities of different components in the decomposition products of SF6 gas in infrared light of different wavelengths are utilized. By modulating infrared light of different wavelengths, the measurement requirements of multi-component gases decomposed from SF6 gas are realized. Compared with traditional tunable infrared lasers, a significant price reduction is achieved.

[0046] In addition, the present invention sets a reflection unit in the photoacoustic cell, and the infrared light entering the photoacoustic cell is reflected back and forth multiple times inside the reflection unit, which effectively increases the optical path of the infrared light, enhances the interaction intensity between the infrared light and the measured gas, obtains a larger excitation signal, and enables the photoacoustic signal to be multiply amplified in the dual resonant cavity, thereby improving the sensitivity of the photoacoustic system.

[0047] At the same time, the present invention uses a completely consistent dual-resonance cavity system, which can reduce the measurement error caused by environmental factors by averaging, making the system more resistant to noise and further improving the sensitivity of the test.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. SF6 decomposition product measurement system based on multi-path dual-resonance cavity photoacoustic spectroscopy, including: Infrared light source and photoacoustic cell, characterized in that: The infrared light source is an infrared blackbody radiation source (2), which is used to generate infrared light of continuous wavelength based on the blackbody radiation principle, and the infrared blackbody radiation source (2) is connected to the infrared optical fiber (5) through an infrared light processing unit; The photoacoustic cell comprises a gas buffer chamber (16) to be measured and a double resonance cavity; The gas buffer chamber (16) to be measured is arranged on a side of the infrared optical fiber (5) away from the infrared light processing unit, and an infrared window (8) is arranged at a position directly opposite to the infrared light injection position; a reflection unit for increasing the infrared light path is arranged inside the gas buffer chamber (16); The dual resonant cavities are symmetrically arranged on opposite sides of the gas buffer chamber (16) to be measured, and are both connected to the interior of the gas buffer chamber (16) to be measured. The dual resonant cavities are used to amplify the photoacoustic signal and transmit the photoacoustic signal to a computing and processing system, and the concentration of SF6 decomposition products is calculated based on the photoacoustic signal.

2. The SF6 decomposition product measurement system based on multi-optical path double-resonance cavity photoacoustic spectroscopy according to claim 1 is characterized in that: The reflection unit comprises two arc-shaped infrared reflectors (10) arranged opposite to each other, wherein the back side of one of the arc-shaped infrared reflectors (10) faces the infrared window (8), and a micro-hole (9) for infrared light to pass through is arranged on the arc-shaped infrared reflector (10) corresponding to the infrared light incident position.

3. The SF6 decomposition product measurement system based on multi-optical path double-resonance cavity photoacoustic spectroscopy according to claim 1 is characterized in that: Each of the resonant cavities is provided with a built-in microphone; The built-in microphone transmits the acoustic signal generated by the gas to be measured absorbing infrared light to the computing and processing system through a filter amplifier (21), a phase-locked amplifier (22) and a data acquisition card (23).

4. The SF6 decomposition product measurement system based on multi-optical path double-resonance cavity photoacoustic spectroscopy according to claim 1 is characterized in that: The infrared light processing unit comprises: a chopper (3) and a plurality of groups of infrared bandpass filters (4); The infrared blackbody radiation source (2), the chopper (3), multiple groups of infrared bandpass filters (4) and the infrared optical fiber (5) are connected in sequence.

5. The SF6 decomposition product measurement system based on multi-optical path double-resonance cavity photoacoustic spectroscopy according to claim 4 is characterized in that: An infrared light collimator (6) is also provided between the infrared optical fiber (5) and the infrared window (8); The infrared light collimator (6) is used to direct the infrared light entering the infrared optical fiber (5) vertically toward the infrared window (8).

6. The SF6 decomposition product measurement system based on multi-optical path dual-resonance cavity photoacoustic spectroscopy according to any one of claims 1 to 5, characterized in that: The system further comprises: a power supply controller (1), which is connected to the infrared black body radiation source (2) and is used to adjust the wavelength of infrared light radiated by the infrared black body radiation source by controlling the magnitude of current.

7. The SF6 decomposition product measurement system based on multi-optical path dual-resonance cavity photoacoustic spectroscopy according to any one of claims 1 to 5, characterized in that: The measured gas buffer chamber (16) is provided with a buffer chamber air inlet (7), the buffer chamber air inlet (7) is provided with an air inlet mass flow meter (25), and the buffer chamber air inlet (7) is used to be connected to a measured gas source (26).

8. The SF6 decomposition product measurement system based on multi-optical path dual-resonance cavity photoacoustic spectroscopy according to any one of claims 1 to 5, characterized in that: A buffer chamber gas outlet (17) is provided at the bottom of the gas buffer chamber (16) to be measured, and the buffer chamber gas outlet (17) is connected to the tail gas collector (20).

9. The multi-optical path dual-resonance cavity photoacoustic spectroscopy system for measuring SF6 gas decomposition products according to claim 8, characterized in that: The buffer chamber air outlet (17) is provided with an air outlet mass flow meter (18).

10. A method for measuring SF6 decomposition products based on multi-path double-resonance cavity photoacoustic spectroscopy, using the SF6 decomposition product measurement system based on multi-path double-resonance cavity photoacoustic spectroscopy according to any one of claims 1 to 9, characterized in that: The following steps are involved: Using an infrared black body radiation source (2) to emit infrared light of a continuous wavelength, and periodically modulating the infrared light to obtain infrared light of a set wavelength; The modulated infrared light source enters the gas buffer chamber (16) to be measured and is reflected multiple times inside the gas buffer chamber (16) to be measured; The SF6 gas to be tested is introduced into the interior of the gas buffer chamber (16) to be tested, and each component in the decomposition product of the SF6 gas absorbs infrared light of a specific wavelength, thereby converting the optical signal into an acoustic wave signal; Amplifying the acoustic wave signal inside the gas buffer chamber (16) to be measured by using a double resonant cavity, and transmitting the acoustic wave signal to a computing and processing system; The calculation and processing system extracts the average value of the received sound wave signal and calculates the concentration of each component in the SF6 decomposition product.

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