A low-cost method and device for diagnosing faults in dissolved gas in oil

Abstract

The application discloses a low-cost oil dissolved gas fault diagnosis method and a fault diagnosis device. The method comprises the following steps: filling a to-be-detected gas into a photoacoustic cell, turning on a DFB laser light source, detecting the acetylene content in the photoacoustic cell, turning off the DFB laser light source, waiting for the to-be-detected gas to return to an initial temperature, turning on a pulsed infrared light source, and directly introducing the infrared light source into the photoacoustic cell after the infrared light source passes through a single optical filter, detecting the methane, ethane and ethylene gas content in the photoacoustic cell, transmitting a detection signal to a data acquisition module through a microphone and a lock-in amplifier, transmitting the detection signal to a terminal device for processing to obtain the oil dissolved gas concentration, comparing the oil dissolved gas concentration with the gas concentration in a normal working state, completing equipment working state judgment, and obtaining the total hydrocarbon concentration. Through the low-cost oil dissolved gas fault diagnosis method and the fault diagnosis device, the oil supply equipment can be diagnosed.

Description

Technical Field

[0001] This invention relates to the field of gas detection device technology, specifically to a low-cost method and device for diagnosing dissolved gas faults in oil. Background Technology

[0002] Analyzing the types and amounts of dissolved gases in transformer oil is an effective means of monitoring the operating status of oil-using equipment and determining the type and magnitude of equipment faults. The accuracy of gas analysis data directly affects the accurate evaluation of the operating status of the corresponding equipment and the correct diagnosis of faults. As transformers age, material aging and insulation deterioration become increasingly prominent, threatening the safe and stable operation of the equipment. Dissolved gas analysis in oil is one of the most effective means of timely detection of equipment faults. However, according to the industry standard "Guidelines for Dissolved Gas Analysis and Judgment in Transformer Oil" (DL / T 722-2014), the offline oil chromatography testing cycle for 110kV transformers is once a year. This means that these transformers will lack effective monitoring during the inspection cycle. Some faults that could have been detected and resolved early on may escalate due to the lack of effective monitoring, eventually leading to tripping or even damage. Therefore, it is necessary to strengthen the effective monitoring capabilities of 110kV transformers, especially those in key substations, those with latent faults, and those with long operating times, which should receive greater attention. However, to achieve full coverage of oil chromatography devices for a large number of 110kV transformers, in addition to the huge investment required for the initial procurement of the equipment, such a large number of devices will also bring huge maintenance costs and management work. How to effectively solve the monitoring needs of these transformers and reduce the resulting costs and maintenance burden is a major challenge at present.

[0003] Currently, there are two main types of equipment used for monitoring dissolved gases in oil, both domestically and internationally: (1) Multi-component dissolved gas online monitoring devices for oil commonly employ technical principles including gas chromatography, photoacoustic spectroscopy, and infrared absorption spectroscopy. These products are relatively mature, covering all seven gases, with some even including air (oxygen + nitrogen) and moisture. However, the main problem with these products is their high price. Furthermore, achieving accurate detection of all components requires complex structure and functions, leading to reduced reliability and increased failure rate. To improve the efficiency of these devices, some manufacturers have proposed "one-to-two" type online dissolved gas monitoring devices based on photoacoustic spectroscopy, such as NARI-GE's "DUALTRANS" and KEMET's "TOTUS G9," which are currently being used in the field. However, these devices are all imported and primarily used in ultra-high voltage applications. While price is not a primary concern, their use in low-voltage transformers presents a cost-effectiveness problem.

[0004] (2) Online monitoring equipment for dissolved gases in low-component oils: Online monitoring technology for low-component oils has been developed and used for a relatively long time. It typically monitors only one or a few components, such as hydrogen or the total amount of combustible gases. For example, the Hydron M2-X typically uses membrane permeation for oil-gas separation, followed by detection of hydrogen and hydrocarbon gases via electrochemical sensors. Currently, online monitoring devices for low-component oils are largely obsolete. The main problems are that the accuracy and stability of these devices do not meet requirements. Furthermore, these devices can only monitor components such as hydrogen and CO, and cannot detect the content of the critical component acetylene alone. Due to the lack of a critical component, the monitoring results are relatively insignificant and lack practicality.

[0005] Characteristic gases play a crucial role in predicting the presence of faults and diagnosing fault types; however, different types of gases play different roles. According to the industry standard "Guidelines for Dissolved Gas Analysis and Judgment in Transformer Oil" (DL / T 722-2014), during fault identification, only specific index values ​​for hydrogen, acetylene, and total hydrocarbons are provided for both newly commissioned and operating equipment. In actual transformer operation, the concentration of these three gases is primarily monitored, and operational procedures are determined based on their indices. Currently, the important role of online monitoring devices is also to monitor the real-time content of acetylene, hydrogen, and total hydrocarbons, providing timely alarms when the absolute amount or growth rate reaches a warning threshold. In other words, early warning of equipment faults mainly relies on these three components: hydrogen, acetylene, and total hydrocarbons. The performance evaluation of online monitoring devices in operation only assesses hydrogen, acetylene, and total hydrocarbons. The content of methane, ethylene, ethane, carbon monoxide, and carbon dioxide is used both to calculate the total hydrocarbon content (the sum of the contents of methane, ethane, ethylene, and acetylene) and primarily for diagnosing equipment fault types. Since the detection accuracy of offline chromatography is significantly higher than that of online monitoring devices, the current method of determining equipment failure type is still based on the analysis and calculation of offline chromatography data. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the issue that current photoacoustic spectroscopy detection devices require multiple filters, corresponding filter disks and filter disk drivers to detect various hydrocarbon gases dissolved in oil, and mechanical choppers to modulate the light beam. This results in large detection devices, high costs, and low accuracy in monitoring 110kV and below equipment and in online equipment fault diagnosis.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A low-cost method for diagnosing dissolved gas faults in oil involves filling a photoacoustic cell 100 with the gas to be tested, turning on a DFB laser source 200 to detect the acetylene content in the photoacoustic cell 100, turning off the DFB laser source 200, and waiting for the gas to be tested to return to its initial temperature. Then, a pulsed infrared source 300 is turned on, and the infrared light passes through a single filter 800 before entering the photoacoustic cell 100 to detect the methane, ethane, and ethylene gas contents. The detection signal is transmitted through a microphone 400, then through a lock-in amplifier 500 to a data acquisition module 600, and finally to a terminal device 700 for processing to obtain the dissolved gas concentration in the oil. This concentration is then compared with the gas concentration under normal operating conditions to determine the equipment's operating status and obtain the total hydrocarbon concentration. The process of obtaining the content of methane, ethane, and ethylene gases includes the following steps: Establish a calibration model for mixed gas concentration; Three sets of mixed gases of known different concentrations were respectively filled into the photoacoustic cell 100; Using the power conversion method, the pulsed infrared light source 300 measures the content of methane, ethane and ethylene gas in each group of mixed gases with different concentrations at three different working power levels. The three sets of photoacoustic signals corresponding to each group of mixed gases with different concentrations at each power level are obtained and fed back to the mixed gas concentration calibration model for parameter calibration. Based on the calibration model of mixed gas concentration after parameter calibration, the contents of methane, ethane and ethylene gases are obtained under any set of gas concentrations at three working power levels of the signal excitation source.

[0008] In one embodiment of the present invention, the mixed gas concentration calibration model is obtained by the following formula: ; ; ; ; ; ; ; ; ; In the formula, The signal conversion coefficient of the microphone. , , These are three optical powers for pulsed infrared light sources. , , The effective power coefficient of methane under different light powers for the same gas concentration. , , The effective power coefficient of ethane under different light powers for the same gas concentration. , , The effective power coefficient of ethylene under different light powers for the same group of gas concentrations; , , These are represented as three groups of methane concentrations; , , These are represented by three groups of ethane concentrations. , , These are represented by three groups of ethylene concentrations. ~ These represent the absorption coefficients for the corresponding absorption spectral bands of methane, ethane, and ethylene, respectively. ~ , ~ , ~ These represent the three sets of photoacoustic signals corresponding to different light powers for each gas concentration.

[0009] In one embodiment of the present invention, the contents of methane, ethane and ethylene gases obtained by inverting the mixed gas concentration calibration model after calibration according to the parameters are added together, and then added to the acetylene concentration to obtain the total hydrocarbon concentration.

[0010] In one embodiment of the present invention, the DFB laser source 200 is incident into the photoacoustic cell 100 via the fiber collimator 210 to excite the photoacoustic effect. Combined with the absorption spectrum of acetylene gas, and based on the stable operating temperature of the DFB, rapid wavelength scanning is achieved by current tuning; and the center wavelength of the DFB laser source 200 is adjusted by setting the center current of the DFB laser source 200.

[0011] In one embodiment of the present invention, the pulsed infrared light source 300 supplies power to the infrared light source controller through the adjustable power supply module 310, and controls the drive signal through the infrared light source controller 320. By setting different drive signals, the output power of the light source is controlled.

[0012] This invention also provides a low-cost oil dissolved gas fault diagnosis device, applied to the aforementioned low-cost oil dissolved gas fault diagnosis method, comprising a photoacoustic cell 100, a DFB laser source 200, a pulsed infrared source 300, a microphone 400, a lock-in amplifier 500, a data acquisition module 600, and a terminal device 700; the DFB laser source 200 is located on the side of the photoacoustic cell 100, so that the laser beam emitted by the DFB laser source 200 enters the photoacoustic cell 100 in a side-projection manner; the pulsed infrared source 300 faces one end of the photoacoustic cell 100, and the pulsed infrared source 300 is coaxial with the photoacoustic cell 100; the microphone 400 is located on the other side of the photoacoustic cell 100; the lock-in amplifier 500, the data acquisition module 600, and the terminal device 700 are sequentially connected to the microphone 400; wherein, a single filter 800 is located between the pulsed infrared source 300 and the photoacoustic cell 100.

[0013] In one embodiment of the present invention, the internal cavity of the photoacoustic cell 100 is cylindrical, with a diameter of 8-16 mm and a length of 30-40 mm.

[0014] In one embodiment of the present invention, the microphone mounting hole on the photoacoustic cell 100 is located at the center of one side, and the microphone mounting hole is at a 90-degree angle to the central axis of the inner cavity of the photoacoustic cell 100.

[0015] In one embodiment of the present invention, the laser incident angle of the DFB laser source 200 is 5~15°.

[0016] In one embodiment of the present invention, the structure of the pulsed infrared light source 300 includes an infrared light source body 341, an infrared light source heat dissipation module 342, an infrared light source base 343, and an interface flange 344; the infrared light source body 341 is connected to the infrared light source base 343 through positioning holes and positioning slots on the infrared light source heat dissipation module 342; a filter slot is provided in the infrared light source base 343, and a single filter 800 is fixed in the filter slot by a set screw; the infrared light source base 343 is connected to the interface flange 344 through multiple positioning holes, and is connected to the photoacoustic cell 100 through the interface flange 344.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: It employs a dual-light source single photoacoustic cell design, utilizing a pulsed infrared light source, a single filter, and a DFB laser light source for gas detection, which requires a time-division multiplexing approach. Specifically, the working principle is as follows: For dissolved gases in the oil from the degassing module, the DFB laser light source is first turned on. Based on the working principle of the DFB laser light source, the acetylene content in the gas is detected. Then, the DFB laser light source is turned off, and the pulsed infrared light source is turned on. Based on the working principle of the pulsed infrared light source and the single filter, the contents of methane, ethane, and ethylene are detected. Hydrogen content detection can be performed synchronously through another gas path. The signals acquired by the sensors are transmitted to the host computer software via a data acquisition module for processing, thereby completing the detection of dissolved gas concentration in the oil for equipment fault diagnosis.

[0018] The single filter detection technology is achieved through the structural coordination of the pulsed infrared light source, the light source heat dissipation module, the light source base, and the interface flange.

[0019] The geometry, materials, fabrication process, and optical and acoustic properties of the photoacoustic cell directly affect the performance of gas photoacoustic measurements. Based on photoacoustic spectroscopy theory, the design and optimization of its structure and modes directly impact the detection sensitivity and stability of the photoacoustic spectroscopy detection system. Following this technical approach, a dual-source multiplexed photoacoustic cell structure is designed. By arranging different components, the detection module is integrated, increasing space utilization and resolving the high cost associated with multiple filters.

[0020] The pulsed infrared light source photoacoustic spectroscopy technology, single-filter multi-component gas comprehensive detection technology, and composite detection module technologies developed in this invention patent will help realize the development of miniaturized detection devices and achieve economical and reliable monitoring of low-voltage oil-filled equipment.

[0021] This invention patent proposes using an electrically modulated pulsed infrared light source combined with a single filter to detect methane, ethane, and ethylene in a three-way gas path, and employing a DFB laser for highly sensitive acetylene detection. Simultaneously, to reduce the gas sample requirements of the detector, a dual-light source excitation single-photoacoustic cell multiplexing detection method was developed. By optimizing the device structure and replacing the rotating components in the photoacoustic spectroscopy with a modulated light source, the reliability of the device is effectively improved. The use of a single filter to detect multiple gases effectively reduces device cost and subsequent maintenance costs.

[0022] The application of this invention patent will generate significant direct and indirect economic benefits. Direct benefits include sales revenue from technology transfer to products; savings in equipment and power costs due to early warning of equipment failures, preventing equipment damage and major accidents such as large-scale power outages; and savings in labor costs due to reduced manual operation. Indirect economic benefits include the socio-economic benefits of reducing large-scale power outages; and the economic benefits of technological innovation driving industry progress. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a low-cost oil dissolved gas fault diagnosis method according to an embodiment of the present invention.

[0024] Figure 2 This is a flowchart illustrating the process of obtaining the content of methane, ethane, and ethylene gases according to an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the DFB laser source driving and data acquisition according to an embodiment of the present invention.

[0026] Figure 4 This is a schematic diagram of the pulsed infrared light source driving and data acquisition according to an embodiment of the present invention.

[0027] Figure 5 This is a schematic diagram of the infrared light source body according to an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of the infrared light source heat dissipation module according to an embodiment of the present invention.

[0029] Figure 7 This is a schematic diagram of the infrared light source base according to an embodiment of the present invention.

[0030] Figure 8 This is a schematic diagram of the interface flange according to an embodiment of the present invention.

[0031] Figure 9 This is a schematic diagram of the pulsed infrared light source and photoacoustic cell in an embodiment of the present invention.

[0032] Figure 10 This is a schematic diagram of the photoacoustic cell according to an embodiment of the present invention. Detailed Implementation

[0033] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0034] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0035] Please see Figures 1 to 4 As shown, this invention provides a low-cost method for diagnosing dissolved gas faults in oil. The gas to be tested is filled into a photoacoustic cell 100. A DFB (Distributed Feedback Laser) light source 200 is turned on to detect the acetylene content in the photoacoustic cell 100. The DFB laser light source 200 is then turned off, and the gas to be tested is allowed to return to its initial temperature. A pulsed infrared light source 300 is then turned on. The infrared light source passes through a single filter 800 and enters the photoacoustic cell 100 to detect the methane, ethane, and ethylene gas contents. The detection signal is amplified by a microphone 400 and a lock-in amplifier 500 before being transmitted to a data acquisition module 600. The signal is then transmitted to a terminal device 700 for processing to obtain the dissolved gas concentration in the oil, and subsequently the total hydrocarbon concentration. This concentration is compared with the gas concentration under normal operating conditions to determine the equipment's operating status.

[0036] The process of obtaining the content of methane, ethane, and ethylene gases includes the following steps: S100, establish a calibration model for the concentration of mixed gas.

[0037] S200, three sets of mixed gases of known different concentrations are respectively filled into the photoacoustic cell 100.

[0038] In this embodiment, the mixed gases of different concentrations are known to be methane, ethane, and ethylene.

[0039] S300 employs a power conversion method, enabling the pulsed infrared light source 300 to measure the content of methane, ethane, and ethylene gases in each group of mixed gases with different concentrations at three different operating power levels. This acquires three sets of photoacoustic signals corresponding to each group of mixed gases with different concentrations at each power level, and feeds them back to the mixed gas concentration calibration model for parameter calibration.

[0040] S400, based on the mixed gas concentration calibration model after parameter calibration, obtains the content of methane, ethane and ethylene gases at any set of gas concentrations under three working power conditions for the signal excitation source.

[0041] In one embodiment of the present invention, a power conversion method is used to detect multiple gas components with a single filter. The basic principle is that as the working power (temperature) of the thermal light source increases or decreases, the light power generated in different infrared bands does not change linearly, but varies. Therefore, a multivariate calibration model can be established, that is, a mixed gas concentration calibration model can be established, as shown in the following set of equations (1): ; ; ; ; ; ; ; ; ; In the formula, The signal conversion coefficient of the microphone. , , These are three optical powers for pulsed infrared light sources. , , The effective power coefficient of methane under different light powers for the same gas concentration. , , The effective power coefficient of ethane under different light powers for the same gas concentration. , , The effective power coefficient of ethylene under different light powers for the same group of gas concentrations; , , These are represented as three groups of methane concentrations; , , These are represented by three groups of ethane concentrations. , , These are represented by three groups of ethylene concentrations. ~ These represent the absorption coefficients for the corresponding absorption spectral bands of methane, ethane, and ethylene, respectively. ~ , ~ , ~ These represent the three sets of photoacoustic signals corresponding to different light powers for each gas concentration.

[0042] In one embodiment of the present invention, the power of the incident light from the pulsed infrared light source 300 is varied. Different photoacoustic signals are obtained based on the varying absorption effects of different gas components at different operating powers. Three known mixed gases of different concentrations are used, and a single filter 800 has been selected, meaning the absorption coefficients for the corresponding absorption bands are determined. The light source powers are as follows: These correspond to the photoacoustic signals obtained from the three measurements.

[0043] By using three sets of mixed gases with different concentrations, and stabilizing the signal excitation light source at three different operating temperatures, and measuring at least nine times, the nine parameters of the model can be calibrated. Then, for any set of three gas concentrations, the signal excitation light source only needs to measure the photoacoustic signal once at each of the three operating temperatures to invert the concentrations of the three gases according to the calibration formula. The total hydrocarbons can be detected by adding the three concentrations together with the acetylene gas concentration, and the concentrations of each component can also be obtained.

[0044] The first group of mixed gases, the light source power of the pulsed infrared light source 300 are respectively , , The three sets of photoacoustic signals are S 11 S 21 S 31

[0045] (2); Simplify the system of equations (2) by knowing the coefficients: (3); The second group of mixed gases, the light source power of the pulsed infrared light source (300) are respectively , , The three sets of photoacoustic signals are S 12 S 22 S 32 .

[0046] (4); Simplify the system of equations (4) by considering the known coefficients: (5); The power of the pulsed infrared light source (300) for the third group of mixed gases is respectively... , , The three sets of photoacoustic signals are S 13 S 23 S 33 .

[0047] (6); Similarly, the known coefficients of equation system (6) are simplified as follows: (7); Solve the system of equations (3), (5), and (7): (10); In the system of equations (10) A , B , C Given quantities D For measurement, the rest are about coefficients. The 9 unknowns can be solved. .

[0048] Depend on By substituting the known and measured data, the solution can be found. 11 , 12 and 13 .

[0049] Similarly, from It can be solved 21 , 22 and 23 .

[0050] Similarly, from It can be solved 31 , 32 and 33 .

[0051] The solution will yield the coefficients. Substituting the nine unknowns back into equations (2), (4), and (6), and changing the power of the light source, the concentrations of the three mixed gases can be solved, as shown in equation (2). , , The concentrations of methane, ethane, and ethylene gases were measured, and the total hydrocarbon concentration was obtained by adding these concentrations to the acetylene gas concentration.

[0052] Please see Figures 1 to 4As shown, in one embodiment of the present invention, the pulsed infrared light source 300, after being modulated, is filtered by a single filter 800 and then enters the photoacoustic cell 100 to excite the photoacoustic effect. The adjustable power supply module 310 supplies power to the infrared light source controller 320, which is driven by a PWM signal. By setting different controller drive signals 330, the output power of the light source is controlled.

[0053] Please see Figures 1 to 4 As shown, in one embodiment of the present invention, a DFB laser source 200 is incident into the photoacoustic cell 100 via an optical fiber collimator 210 to excite the photoacoustic effect. Combined with the absorption spectrum of acetylene gas, and based on the stable temperature of the DFB current, rapid wavelength scanning is achieved through current tuning. The DFB laser source 200 is driven by a DFB driving circuit. The center wavelength of the DFB laser source 200 can be adjusted by setting the center current passing through it. Combined with the sine wave, sawtooth wave, and DC bias in the driving circuit, scanning of the acetylene molecule absorption spectrum can be achieved.

[0054] Please see Figures 1 to 10 As shown, this invention also provides a low-cost dissolved gas fault diagnosis device for oil, applied to the aforementioned low-cost dissolved gas fault diagnosis method for oil, comprising a photoacoustic cell 100, a DFB laser source 200, a pulsed infrared source 300, a microphone 400, a lock-in amplifier 500, a data acquisition module 600, and a terminal device 700; the DFB laser source 200 is located on the side of the photoacoustic cell 100, so that the laser beam emitted by the DFB laser source 200 enters the photoacoustic cell 100 in a side-projection manner. The pulsed infrared source 300 faces one end of the photoacoustic cell 100, and the pulsed infrared source 300 is coaxial with the photoacoustic cell 100. The microphone 400 is located on the other side of the photoacoustic cell 100, and the lock-in amplifier 500, the data acquisition module 600, and the terminal device 700 are sequentially connected to the microphone 400. A single filter 800 is located between the pulsed infrared source 300 and the photoacoustic cell 100.

[0055] Please see Figures 5 to 10As shown, in one embodiment of the present invention, the photoacoustic cell 100 is a key component of the core module of the photoacoustic spectrometer, and the photoacoustic effect is generated within it. The geometry, materials, processing technology, optical and acoustic characteristics of the photoacoustic cell 100 directly affect the performance of gas photoacoustic measurement. According to photoacoustic spectroscopy theory, the design and optimization of its structure and mode can directly affect the detection sensitivity and stability of the photoacoustic spectroscopy detection system. In addition, the selection of its materials should also be combined with the physicochemical properties of the gas to be detected, such as adsorption and hydrolysis, to ensure that it meets the requirements of versatility. According to the relationship between the modulation frequency of the incident light and the resonant frequency of the lowest-order normal mode of the photoacoustic cell 100, the generation of photoacoustic signals can be divided into non-resonant and resonant types. When the modulation frequency is much lower than the resonant frequency, the photoacoustic cell operates in non-resonant mode. When the modulation frequency is equal to the resonant frequency, the photoacoustic cell operates in resonant mode. This embodiment uses a non-resonant photoacoustic cell, where the sound pressure is basically equal at all points within the non-resonant photoacoustic cell. Considering the coupling of the light source and the installation requirements of the microphone 400. To meet the requirements of light source coupling and microphone 400 configuration, the present invention designs a cylindrical cavity structure for photoacoustic cell 100 and keeps it coaxial with pulsed infrared light source 300 to improve the coupling efficiency of incident light.

[0056] A smaller cavity cross-section has a significant effect on improving the photoacoustic signal. However, when the photoacoustic cell 100 is used in conjunction with the pulsed infrared light source 300, the limitation of the light source's focusing effect means that the cavity cross-section is usually much larger than the theoretical limit. The parabolic reflector can focus the main light energy, preferably within a circular area of ​​Ф12~15mm. After optical path simulation, considering tolerances, the cavity diameter of the photoacoustic cell 100 is determined to be 8~16mm. Theoretically, the cavity length has little impact on the photoacoustic signal, but in practice, a larger cavity volume is significant in reducing the photoacoustic signal loss rate, effectively eliminating the acoustic signal loss caused by the microphone 400's mounting holes and air inlet / outlet passages. Additionally, the overall volume of the photoacoustic cavity must be considered. In this embodiment, the cavity length of the photoacoustic cell 100 is preferably 30~40mm.

[0057] Please see Figures 5 to 10 As shown, in one embodiment of the present invention, the laser beam entrance aperture design of the DFB laser source 200 is described. A reasonable design of the laser entrance aperture plays a crucial role in the subsequent laser-excited acetylene gas to generate a photoacoustic effect, significantly impacting the final acetylene detection result. To avoid mutual interference between the laser source and the infrared source, given that the infrared source is certain to enter, it is installed from the side of the photoacoustic cell 100, allowing the laser source to enter the photoacoustic cell 100 from the side, thus completing the dual-source single-photoacoustic-cell design.

[0058] In the design of the laser incident aperture angle, the photoacoustic cell 100 is incident at a small angle with the horizontal plane, preferably 5~15°.

[0059] In this embodiment, the pulsed infrared light source 300 should be used in conjunction with the photoacoustic cell 100. The infrared light source entrance aperture is designed at the end facing the photoacoustic cell 100 to ensure the excitation effect of the light source on the gas and improve the coupling efficiency of the incident light.

[0060] In this embodiment, the microphone mounting hole is designed on the side wall of the photoacoustic cell, at a 90-degree angle to the central axis of the inner cavity of the photoacoustic cell 100, while not interfering with the propagation of the laser beam. The size of the microphone mounting hole should allow the microphone 400 to pass through smoothly without affecting the internal sealing of the photoacoustic cell 100 and the generation of the photoacoustic signal. The size of the microphone mounting hole is designed according to the dimensions of the microphone 400 and the structure of the photoacoustic cell 100 to achieve optimal signal effect and sealing performance. The microphone 400 is mounted by opening an opening at the center of the side of the photoacoustic cell 100.

[0061] In one embodiment of the present invention, an inlet / outlet port and a solenoid valve mounting hole are provided on another side of the photoacoustic cell 100. At the initial stage of detection, the gas to be tested needs to be introduced into the photoacoustic cell 100 through the inlet port. At the end of detection, the gas in the photoacoustic cell 100 needs to be discharged through the outlet port to prepare for the next detection. A solenoid valve needs to be installed in the inlet / outlet pipeline to control the inlet / outlet timing. Generally, the location of the inlet / outlet port should allow the gas inside the photoacoustic cell to flow smoothly without affecting the generation and detection of the photoacoustic signal, and should be as far away as possible from the laser beam and microphone mounting hole. The size of the inlet / outlet port should allow the gas to flow smoothly without affecting the detection accuracy of the photoacoustic signal. The size of the inlet / outlet port should be designed according to actual needs. With a roughly determined gas flow rate, the size of the inlet / outlet port should be matched to the flow rate to achieve optimal gas flow and signal performance.

[0062] The solenoid valves on the inlet and outlet gas pipelines are controlled by the control program of the photoacoustic spectroscopy system to complete the final gas intake and exhaust. The photoacoustic cell 100, through structural optimization and in conjunction with sensors and other components, completes gas concentration detection, ultimately providing structural support for judging the equipment status.

[0063] In one embodiment of the present invention, the DFB laser source 200 is driven by a driver and emits periodic laser light. The laser light is transmitted through an optical fiber to an EDFA for power amplification, and then enters the photoacoustic cell 100 through an optical fiber collimator 210 in a side-firing manner to excite a photoacoustic signal. The angle of incidence between the incident angle and the central axis of the photoacoustic cell 100 is 5-15°. The sound pressure of the photoacoustic signal is received by a microphone 400 and converted into an electrical signal, which is then transmitted to a lock-in amplifier 500 for processing. The processed signal is acquired by a data acquisition card and transmitted to a computer.

[0064] In one embodiment of the present invention, the structure of the pulsed infrared light source 300 includes an infrared light source body 341, an infrared light source heat dissipation module 342, an infrared light source base 343, and an interface flange 344. The infrared light source body 341 is connected to the infrared light source base 343 through positioning holes and positioning slots on the infrared light source heat dissipation module 342 to ensure the stability of the relative position of the light source during use. The infrared light source base 343 is provided with a filter slot and has an M2 hole on the side, and a single filter 800 is fixed in the filter slot by a set screw. The infrared light source base 343 is made of a material with low thermal conductivity to minimize the influence of the temperature of the infrared light source heat dissipation module 342 on the temperature of the photoacoustic cell 100. The infrared light source base 343 is connected to the interface flange 344 through the four positioning holes on the top, and is connected to the photoacoustic cell 100 through the interface flange 344, and the connection is sealed by a window and an O-ring. Specifically, in this embodiment, the pulsed infrared light source 300 is an electrically modulated infrared light source, avoiding the large size caused by mechanical modulation, reducing costs, and miniaturizing the instrument.

[0065] In one embodiment of the present invention, the lock-in amplifier 500 uses cross-correlation detection technology to detect the signal under test, which can extract extremely weak signals.

[0066] In one embodiment of the present invention, the data acquisition module 600 is implemented using a 16-bit AD conversion chip. The signal data obtained by the data acquisition module 600 is processed and analyzed by the terminal device 700. First, the signal is filtered and denoised to eliminate the influence of external noise. Then, the signal mean is written as a variable into the calibrated equation, and the concentration of each component gas is obtained by inversion.

[0067] In one embodiment of the present invention, the fault diagnosis device further includes a temperature control module 910, a hydrogen sensor 920, and an oil sampling and degassing module 930. The temperature control module 910 is connected to the photoacoustic cell 100 and monitors the temperature inside the photoacoustic cell 100. The hydrogen sensor 920 detects the hydrogen content of the gas to be tested in the gas path and transmits the hydrogen content signal to the data acquisition module 600. The oil sampling and degassing module 930 is connected to the inlet and outlet of the photoacoustic cell 100 to sample the gas to be tested and deliver it into the photoacoustic cell 100, and to extract the tested gas from the photoacoustic cell 100 after testing.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0069] The above embodiments are merely examples of implementation methods of the invention. The scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A low-cost method for diagnosing dissolved gas faults in oil, characterized in that, The gas to be tested is filled into the photoacoustic cell (100), the DFB laser source (200) is turned on, and the acetylene content in the photoacoustic cell (100) is detected. The DFB laser source (200) is turned off, and the gas to be tested is allowed to return to its initial temperature. The pulse infrared source (300) is turned on, and the infrared source passes through a single filter (800) and enters the photoacoustic cell (100) to detect the methane, ethane and ethylene gas content in the photoacoustic cell (100). The detection signal is transmitted through a microphone (400), through a lock-in amplifier (500) to a data acquisition module (600), and then to a terminal device (700) for processing to obtain the dissolved gas concentration in the oil. The concentration is compared with the gas concentration under normal operating conditions to complete the equipment working status judgment. The process of obtaining the content of methane, ethane, and ethylene gases includes the following steps: Establish a calibration model for mixed gas concentration: ； ； ； ； ； ； ； ； ； In the formula, The signal conversion coefficient of the microphone. , , These are three optical powers for pulsed infrared light sources. , , The effective power coefficient of methane under different light powers for the same gas concentration. , , The effective power coefficient of ethane under different light powers for the same gas concentration. , , The effective power coefficient of ethylene under different light powers for the same group of gas concentrations; , , These are represented as three groups of methane concentrations; , , These are represented by three groups of ethane concentrations. , , These are represented by three groups of ethylene concentrations. ~ These represent the absorption coefficients for the corresponding absorption spectral bands of methane, ethane, and ethylene, respectively. ~ , ~ , ~ These represent the three sets of photoacoustic signals corresponding to different light powers for each gas concentration. Three sets of mixed gases of known different concentrations were respectively filled into the photoacoustic cell (100); Using the power conversion method, the pulsed infrared light source (300) measures the content of methane, ethane and ethylene gas in each group of mixed gas with different concentrations at three working power levels, obtains the three sets of photoacoustic signals corresponding to each group of mixed gas with different concentrations at each power level, and feeds them back to the mixed gas concentration calibration model for parameter calibration. Based on the calibration model of mixed gas concentration after parameter calibration, the contents of methane, ethane and ethylene gases are obtained under any set of gas concentrations to be measured at three working power levels of the signal excitation source.

2. The low-cost oil dissolved gas fault diagnosis method according to claim 1, characterized in that, The methane, ethane, and ethylene gas contents derived from the mixed gas concentration calibration model based on the parameters are added together, and then added to the acetylene concentration to obtain the total hydrocarbon concentration.

3. The low-cost oil dissolved gas fault diagnosis method according to claim 1, characterized in that, The DFB laser source (200) is incident into the photoacoustic cell (100) via the fiber collimator (210) to excite the photoacoustic effect. Combined with the absorption spectrum of acetylene gas, and based on the stable operating temperature of the DFB, the current tuning is used to achieve rapid wavelength scanning; and the center wavelength of the DFB laser source (200) is adjusted by setting the center current through the DFB laser source (200).

4. The low-cost oil dissolved gas fault diagnosis method according to claim 1, characterized in that, The pulsed infrared light source (300) supplies power to the infrared light source controller through the adjustable power supply module (310), and controls the drive signal through the infrared light source controller (320). By setting different drive signals, the output power of the light source can be controlled.

5. A low-cost oil dissolved gas fault diagnosis device, characterized in that, The method for diagnosing dissolved gas faults in oil according to any one of claims 1-4 includes a photoacoustic cell (100), a DFB laser source (200), a pulsed infrared source (300), a microphone (400), a lock-in amplifier (500), a data acquisition module (600), and a terminal device (700); the DFB laser source (200) is located on the side of the photoacoustic cell (100), so that the laser beam emitted by the DFB laser source (200) enters the photoacoustic cell in a side-projection manner. (100); a pulsed infrared light source (300) is positioned opposite one end of the photoacoustic cell (100), and the pulsed infrared light source (300) and the photoacoustic cell (100) are coaxial; a microphone (400) is located on the other side of the photoacoustic cell (100); a lock-in amplifier (500), a data acquisition module (600) and a terminal device (700) are connected to the microphone (400) in sequence; wherein, a single filter (800) is located between the pulsed infrared light source (300) and the photoacoustic cell (100).

6. The low-cost oil dissolved gas fault diagnosis device according to claim 5, characterized in that, The internal cavity of the photoacoustic cell (100) is cylindrical, with a diameter of 8~16mm and a length of 30~40mm.

7. The low-cost oil dissolved gas fault diagnosis device according to claim 5, characterized in that, The microphone mounting hole on the photoacoustic cell (100) is located at the center of one side, and the microphone mounting hole is at a 90-degree angle to the central axis of the inner cavity of the photoacoustic cell (100).

8. The low-cost oil dissolved gas fault diagnosis device according to claim 5, characterized in that, The laser incident angle of the DFB laser source (200) is 5~15°.

9. The low-cost oil dissolved gas fault diagnosis device according to claim 5, characterized in that, The structure of the pulsed infrared light source (300) includes an infrared light source body (341), an infrared light source heat dissipation module (342), an infrared light source base (343), and an interface flange (344). The infrared light source body (341) is connected to the infrared light source base (343) through the positioning holes and positioning slots on the infrared light source heat dissipation module (342). A filter slot is provided in the infrared light source base (343), and a single filter (800) is fixed in the filter slot by a set screw. The infrared light source base (343) is connected to the interface flange (344) through multiple positioning holes, and is connected to the photoacoustic cell (100) through the interface flange (344).

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