A method and system for detecting dissolved gases in transformer oil

Abstract

This invention proposes a method and system for detecting dissolved gases in transformer oil, belonging to the field of gas detection technology. The system includes: a gas chamber and an oil-gas separation membrane; the gas chamber is connected to a bypass in the transformer oil circuit, and a tuning fork is installed in the gas chamber; the oil-gas separation membrane is located between the bypass interface of the transformer oil circuit and the gas chamber; one side of the oil-gas separation membrane is oil in the transformer oil circuit, and the other side is gas; dissolved gases in the oil in the transformer oil circuit diffuse into the gas chamber through the oil-gas separation membrane; the dissolved gases in the oil in the transformer oil circuit under test generate sound waves, i.e., photoacoustic signals, in the gas chamber due to the photoacoustic effect; these sound waves are detected by the tuning fork and processed to determine the gas concentration value.

Description

Technical Field

[0001] This invention belongs to the field of gas detection technology, and in particular relates to a method and system for detecting dissolved gases in transformer oil. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Dissolved gas detection in transformer oil is a core technical means for transformer condition monitoring and is of great significance for ensuring the safe and stable operation of the power grid.

[0004] Photoacoustic spectroscopy, with its advantages of high sensitivity, good selectivity, and ability to detect multi-component gases, has become the preferred solution for dissolved gas detection in oil. Traditional photoacoustic spectroscopy uses a photoacoustic cell combined with a microphone to detect photoacoustic signals. However, the photoacoustic cell is usually large, resulting in relatively high gas consumption. At the same time, the microphone has a wide response bandwidth, and the photoacoustic cell usually operates in the low-frequency range, making it very susceptible to interference from low-frequency noise and vibration in substation applications.

[0005] Tuning fork-enhanced photoacoustic spectroscopy, as an improved technique of photoacoustic spectroscopy, uses a miniaturized, high-resonance-frequency, high-quality-factor tuning fork to detect photoacoustic signals. It has the advantages of small size, low gas consumption, and strong anti-interference ability, and has great application potential in the field of dissolved gas detection in oil.

[0006] When detecting dissolved gases in oil, the gases must first be separated from the oil before being introduced into a gas chamber for detection. Therefore, a degassing device is typically installed at the front end of the photoacoustic spectroscopy detection system. Degassing methods include vacuum degassing, headspace degassing, and membrane degassing. Vacuum degassing and headspace degassing systems are complex and cumbersome to operate. Therefore, with the development of related polymer materials technologies, membrane degassing has begun to be gradually applied to the detection of dissolved gases in oil.

[0007] Currently, photoacoustic spectroscopy detection systems based on membrane degassing often first separate dissolved gases from oil using an oil-gas separation membrane, and then introduce them into the gas chamber through a gas pipe. This reduces degassing efficiency, increases response time, and increases device size. In addition, if the oil-gas separation structure is directly installed on the transformer body, it will result in a large size and susceptibility to noise interference. How to combine the tuning fork with the oil-gas separation membrane is a major issue that needs to be considered. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention provides a method and system for detecting dissolved gases in transformer oil, which can reduce the size of the device, shorten the response time, improve the detection accuracy, and enhance the anti-interference capability.

[0009] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In a first aspect, a system for detecting dissolved gases in transformer oil is disclosed, comprising: Gas chamber and oil-gas separation membrane; The gas chamber is connected to the bypass of the transformer oil circuit, and a tuning fork is installed in the gas chamber. The oil-gas separation membrane is located between the bypass interface of the transformer oil circuit and the gas chamber. One side of the oil-gas separation membrane is oil in the transformer oil circuit, and the other side is gas. Dissolved gas in the oil in the transformer oil circuit diffuses into the gas chamber through the oil-gas separation membrane. The dissolved gas in the oil circuit of the transformer under test generates sound waves, i.e., photoacoustic signals, in the gas chamber due to the photoacoustic effect. These sound waves are detected and processed by the tuning fork to determine the concentration value of the gas.

[0010] As a further technical solution, the tuning fork includes two symmetrically arranged tuning fork arms, with a gap between the tuning fork arms.

[0011] As a further technical solution, it also includes: a laser driver, an excitation light source, a collimator, a high-transmittance lens, and a high-reflectance lens; The excitation light source is driven and modulated by the laser driver to emit modulated laser light. After the beam is collimated by the collimator, it enters the gas chamber through the high-transmittance lens, passes through the gap between the arms of the tuning fork, and is reflected by the high-reflectance lens before passing through the gap between the arms of the tuning fork again, thereby doubling the intensity of the photoacoustic signal.

[0012] As a further technical solution, the gas chamber is connected to the bypass of the oil circuit via a flange, so that the oil-gas separation membrane is located between the bypass interface of the oil circuit and the gas chamber.

[0013] As a further technical solution, the chamber also includes a base, on which the tuning fork is fixed; The base is fixed to the inner wall of the air chamber by a sealed mounting seat; when fixing the tuning fork, the gap between its two arms is precisely aligned with the laser beam path; The base of the tuning fork is equipped with electrical leads, which pass through a sealed interface on the gas chamber wall and connect to an external processor; or The base of the tuning fork is equipped with an optical fiber lead, which passes through a sealed interface on the gas chamber wall and connects to an external processor.

[0014] As a further technical solution, the oil-gas separation membrane is a composite membrane of polytetrafluoroethylene and alumina.

[0015] As a further technical solution, the signal processing unit processes the signal detected by the tuning fork to retrieve the gas concentration value.

[0016] As a further technical solution, the laser driver controls the temperature and current of the excitation light source so that its center wavelength is aligned with the center of the absorption spectrum of the gas to be measured. At the same time, the current is modulated by a sine wave with a frequency half that of a tuning fork resonant frequency, thereby achieving wavelength modulation of the laser.

[0017] As a further technical solution, the signal processing unit includes a processor and a lock-in amplifier; The lock-in amplifier is used to improve the detection signal-to-noise ratio. It operates in second harmonic demodulation mode. The frequency of the photoacoustic signal is the resonant frequency of the tuning fork. The lock-in amplifier demodulates this photoacoustic signal, and the demodulated signal is output to the processor.

[0018] Secondly, a method for detecting dissolved gases in transformer oil is disclosed, including: The excitation light source is driven and modulated by the laser driver to emit modulated laser light. After the beam is collimated by the collimator, it enters the gas chamber through the high-transmittance lens, passes through the gap between the arms of the tuning fork, and is reflected by the high-reflectance lens before passing through the gap between the arms of the tuning fork again. Dissolved gases in the transformer oil circuit diffuse through the oil-gas separation membrane into the gas chamber; The dissolved gas in the oil circuit of the transformer under test generates sound waves, i.e., photoacoustic signals, in the gas chamber due to the photoacoustic effect. These sound waves are detected and processed by the tuning fork to determine the concentration value of the gas.

[0019] The above one or more technical solutions have the following beneficial effects: The technical solution of this invention involves connecting a gas chamber to the bypass of the transformer oil circuit. A tuning fork is installed in the gas chamber, and an oil-gas separation membrane is located between the bypass interface of the transformer oil circuit and the gas chamber. One side of the oil-gas separation membrane is oil in the transformer oil circuit, and the other side is gas. Dissolved gas in the oil in the transformer oil circuit diffuses into the gas chamber through the oil-gas separation membrane, allowing gas detection to be directly connected to the bypass of the transformer oil circuit. This eliminates the need for gas pipes and additional degassing units, and has the advantages of simple device, convenient use, short response time, high degassing efficiency, and no damage to the transformer body.

[0020] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a schematic diagram of the system for detecting dissolved gases in transformer oil according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the bypass connection between the tuning fork and the oil circuit in an embodiment of the present invention; In the diagram, 1 is the laser driver; 2 is the excitation light source; 3 is the collimator; 4 is the gas chamber; 5 is the tuning fork; 6 is the oil-gas separation membrane; 7 is the high-transmittance lens; 8 is the high-reflectance lens; and 9 is the signal processing unit. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0025] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0026] Example 1 See appendix Figure 1-2 As shown, this embodiment discloses a dissolved gas detection system in transformer oil, comprising: Gas chamber and oil-gas separation membrane; The gas chamber is connected to the bypass of the transformer oil circuit, and a tuning fork is installed in the gas chamber. The oil-gas separation membrane is located between the bypass interface of the transformer oil circuit and the gas chamber. One side of the oil-gas separation membrane is oil in the transformer oil circuit, and the other side is gas. Dissolved gas in the oil in the transformer oil circuit diffuses into the gas chamber through the oil-gas separation membrane. The dissolved gas in the oil circuit of the transformer under test generates sound waves, i.e., photoacoustic signals, in the gas chamber due to the photoacoustic effect. These sound waves are detected and processed by the tuning fork to determine the concentration value of the gas.

[0027] In this embodiment, by integrating a high-efficiency oil-gas separation membrane with a miniaturized, highly sensitive tuning fork-enhanced photoacoustic spectroscopy detection, the oil-gas separation membrane used for detection is directly connected to the bypass of the transformer oil circuit, eliminating the need for gas pipes and additional degassing units. This method has the advantages of simple device, convenient use, short response time, high degassing efficiency, and no damage to the transformer body.

[0028] In one embodiment, the tuning fork includes two symmetrically arranged tuning fork arms with a gap between them.

[0029] In one implementation example, more specifically, it also includes: a laser driver, an excitation source, a collimator, a high-transmittance lens, and a high-reflectance lens.

[0030] The laser driver is connected to the excitation light source; the collimator is located between the excitation light source and the gas chamber.

[0031] High-transmittance lenses and high-reflectance lenses are placed on the gas chamber and located on two surfaces perpendicular to the oil-gas separation membrane. They are used to transmit and reflect light, respectively, while isolating external noise.

[0032] The excitation light source is driven and modulated by a laser driver to emit modulated laser light. After the beam is collimated by the collimator, it enters the air chamber through a high-transmittance lens, passes through the gap between the arms of the tuning fork, and is reflected by the high-reflectance lens before passing through the gap between the arms of the tuning fork again, thereby doubling the intensity of the photoacoustic signal.

[0033] The gas chamber is connected to the bypass of the oil circuit via a flange, so that the oil-gas separation membrane is located between the bypass interface of the oil circuit and the gas chamber. One side of the oil-gas separation membrane is oil, and the other side is gas. The dissolved gas in the oil diffuses into the gas chamber through the oil-gas separation membrane. The gas to be tested generates sound waves in the gas chamber due to the photoacoustic effect, that is, a photoacoustic signal. The sound waves are detected by the tuning fork and processed by the signal processing unit to retrieve the concentration value of the gas.

[0034] In one embodiment, in order to fix the gas chamber and the oil-gas separation membrane, a connecting block is also included, and the connecting block is connected to the transformer oil circuit bypass pipe by a flange, which is usually a standard industrial interface. The gas chamber is fixed to the connecting block by a flange and is tightly connected to the oil-gas separation membrane.

[0035] In one implementation example, in order to fix the tuning fork and avoid the gap between the two vibrating arms being unable to be precisely aligned with the laser beam path due to shaking during use, thereby failing to enhance the intensity of the photoacoustic signal, the air chamber also includes a base, on which the tuning fork is fixed. The base is fixed to the inner wall of the air chamber by a sealed mounting seat; when fixing the tuning fork, the gap between its two arms is precisely aligned with the laser beam path.

[0036] It should be noted that when the two arms of the tuning fork are excited by sound waves, they vibrate in opposite phases, one inward and the other outward. This mode effectively cancels out interference from environmental common-mode noise, responding only to sound signals of a specific frequency. A gap exists between the tuning fork arms, serving as a laser channel. The modulated laser beam, after collimation, passes precisely through this gap. When the gas absorbs light energy and generates sound waves, these sound waves drive the tuning fork arms to vibrate. In one embodiment, if the signal processing unit uses an electrical measurement unit, the tuning fork base is equipped with electrical leads that pass through a sealed interface on the gas chamber wall and connect to the external signal processing unit. The tuning fork is typically made of a piezoelectric material (such as quartz crystal). When the arms vibrate, a weak alternating electrical signal is generated on the electrodes of the tuning fork due to its piezoelectric effect. This signal is extracted and transmitted to the signal processing unit for amplification and demodulation.

[0037] In one embodiment, the signal processing unit includes a processor and a lock-in amplifier; A lock-in amplifier is used to improve the detection signal-to-noise ratio. It operates in second harmonic demodulation mode and demodulates the photoacoustic signal at the resonant frequency of the tuning fork 5.

[0038] The oil-gas separation membrane 6 uses a composite membrane of polytetrafluoroethylene (PTFE) and alumina. The low surface energy of PTFE repels oil molecules, while the gas affinity of alumina promotes the preferential permeation of gas molecules. This combination of materials can effectively reduce the risk of oil adhesion on the membrane, improve oil-gas separation efficiency, and extend membrane life.

[0039] Specifically, the signal processing unit 9 is an electrical measuring device or an optical measuring device used to detect the vibration displacement of the tuning fork generated by photoacoustic signal excitation. The electrical measuring device is suitable for tuning forks made of piezoelectric materials, while the optical measuring device is suitable for tuning forks made of any material.

[0040] Specifically, the laser driver 1 controls the temperature and current of the excitation light source 2 so that its center wavelength is aligned with the center of the absorption spectrum of the gas to be tested. At the same time, the current is modulated by a sine wave with a frequency half that of a tuning fork resonant frequency, thereby achieving wavelength modulation of the laser.

[0041] Specifically, to further improve the detection sensitivity, the tuning fork 5 can be equipped with a miniature resonant tube, including but not limited to dual-tube on-axis configuration, single-tube on-axis configuration, and single-tube off-axis configuration.

[0042] In this embodiment of the invention, the resonant frequency of the tuning fork is 2kHz~35kHz, and the quality factor is 3000~15000.

[0043] The system in this embodiment only includes a laser driver, excitation light source, collimator, gas chamber, tuning fork, oil-gas separation membrane, high-transmittance lens, high-reflectance lens, and signal processing unit. It does not require an additional degassing device, has a simple structure, small size, and is easy to install. Dissolved gas in the oil diffuses directly into the miniaturized gas chamber from the bypass of the oil circuit through the high-efficiency oil-gas separation membrane. It has a short response time, low gas consumption, and does not damage the transformer body.

[0044] By integrating a high-efficiency oil-gas separation membrane with tuning fork-enhanced photoacoustic spectroscopy, the advantages of the oil-gas separation membrane (small size and easy operation) and the tuning fork-enhanced photoacoustic spectroscopy (small size and low gas consumption) are fully combined, thereby achieving the goals of reducing device size, shortening response time, and improving degassing efficiency.

[0045] Example 2 The purpose of this embodiment is to provide a method for detecting dissolved gases in transformer oil, including: The excitation light source is driven and modulated by the laser driver to emit modulated laser light. After the beam is collimated by the collimator, it enters the gas chamber through the high-transmittance lens, passes through the gap between the arms of the tuning fork, and is reflected by the high-reflectance lens before passing through the gap between the arms of the tuning fork again. Dissolved gases in the transformer oil circuit diffuse through the oil-gas separation membrane into the gas chamber; The dissolved gas in the oil circuit of the transformer under test generates sound waves, i.e., photoacoustic signals, in the gas chamber due to the photoacoustic effect. These sound waves are detected and processed by the tuning fork to determine the concentration value of the gas.

[0046] The specific operation method of the above system includes the following steps: S1. The gas chamber 4 is set at one end of the oil-gas separation membrane 6 and connected to the bypass of the oil circuit through a flange. The dissolved gas in the oil diffuses directly into the gas chamber 4 through the oil-gas separation membrane 6. S2. The laser emitted by the excitation light source 2, modulated by the laser driver 1, is collimated by the collimator 3, and then incident into the gas chamber 4 through the high-transmittance lens 7. It passes through the gap between the arms of the tuning fork 5. The gas in the gas chamber 4 generates sound waves, i.e., photoacoustic signals, due to the photoacoustic effect, which are detected by the tuning fork 5. The laser beam is reflected by the high-reflectance lens 8 and passes through the gap between the arms of the tuning fork 5 again, thus amplifying the photoacoustic signal by 1 time. The signal processing unit 9 is used to process the signal of the tuning fork 5 to realize the inversion of gas concentration.

[0047] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A transformer oil dissolved gas detection system characterized by, include: Gas chamber and oil-gas separation membrane; The gas chamber is connected to the bypass of the transformer oil circuit, and a tuning fork is installed in the gas chamber. The oil-gas separation membrane is located between the bypass interface of the transformer oil circuit and the gas chamber. One side of the oil-gas separation membrane is oil in the transformer oil circuit, and the other side is gas. Dissolved gas in the oil in the transformer oil circuit diffuses into the gas chamber through the oil-gas separation membrane. The dissolved gas in the oil circuit of the transformer under test generates sound waves in the gas chamber due to the photoacoustic effect. These sound waves are detected and processed by the tuning fork to determine the concentration value of the gas.

2. The dissolved gas detection system in transformer oil as described in claim 1, characterized in that, The tuning fork includes two symmetrically arranged tuning fork arms with a gap between them.

3. The dissolved gas detection system in transformer oil as described in claim 1, characterized in that, Also includes: Laser driver, excitation source, collimator, high-transmittance lens and high-reflectance lens; The excitation light source is driven and modulated by the laser driver to emit modulated laser light. After the beam is collimated by the collimator, it enters the gas chamber through the high-transmittance lens, passes through the gap between the arms of the tuning fork, and is reflected by the high-reflectance lens before passing through the gap between the arms of the tuning fork again, thereby doubling the intensity of the photoacoustic signal.

4. The dissolved gas detection system in transformer oil as described in claim 1, characterized in that, The gas chamber is connected to the bypass of the oil circuit via a flange, so that the oil-gas separation membrane is located between the bypass interface of the oil circuit and the gas chamber.

5. The dissolved gas detection system in transformer oil as described in claim 1, characterized in that, The chamber also includes a base, on which the tuning fork is fixed; The base is fixed to the inner wall of the air chamber by a sealed mounting seat; when fixing the tuning fork, the gap between its two arms is precisely aligned with the laser beam path; The base of the tuning fork is equipped with electrical leads, which pass through a sealed interface on the gas chamber wall and connect to an external processor; or The base of the tuning fork is equipped with an optical fiber lead, which passes through a sealed interface on the gas chamber wall and connects to an external processor.

6. The dissolved gas detection system in transformer oil as described in claim 1, characterized in that, The oil-gas separation membrane is a composite membrane of polytetrafluoroethylene and alumina.

7. The dissolved gas detection system in transformer oil as described in claim 1, characterized in that, The signal processing unit processes the signal detected by the tuning fork to retrieve the gas concentration value.

8. The dissolved gas detection system in transformer oil as described in claim 3, characterized in that, The laser driver controls the temperature and current of the excitation light source so that its center wavelength is aligned with the center of the absorption spectrum of the gas to be measured. At the same time, the current is modulated by a sine wave with a frequency half that of a tuning fork, thereby achieving wavelength modulation of the laser.

9. The dissolved gas detection system in transformer oil as described in claim 7, characterized in that, The signal processing unit includes a processor and a lock-in amplifier; The lock-in amplifier is used to improve the detection signal-to-noise ratio. It operates in second harmonic demodulation mode. The frequency of the photoacoustic signal is the resonant frequency of the tuning fork. The lock-in amplifier demodulates this photoacoustic signal, and the demodulated signal is output to the processor.

10. A detection method based on the dissolved gas detection system in transformer oil according to any one of claims 1-9, characterized in that, include: The excitation light source is driven and modulated by the laser driver to emit modulated laser light. After the beam is collimated by the collimator, it enters the gas chamber through the high-transmittance lens, passes through the gap between the arms of the tuning fork, and is reflected by the high-reflectance lens before passing through the gap between the arms of the tuning fork again. Dissolved gases in the transformer oil circuit diffuse through the oil-gas separation membrane into the gas chamber; The dissolved gas in the oil circuit of the transformer under test generates sound waves in the gas chamber due to the photoacoustic effect. These sound waves are detected and processed by the tuning fork to determine the concentration value of the gas.

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