Method and system for detecting dissolved gas in time division multiplexing transformer oil

Abstract

The invention provides a method and system for detecting dissolved gas in transformer oil by time division multiplexing, and the method comprises the steps: enabling an online monitoring device to sequentially detect oil samples in a plurality of transformer phases through a valve control strategy; according to the valve control strategy, when an oil sample in a transformer phase is detected, only an oil inlet valve of the current detected phase and an oil inlet valve in the online monitoring device are opened, and the oil sample enters a degassing system in the online monitoring device; after oil feeding is completed, the oil feeding valve at the corresponding phase and the oil feeding valve in the online monitoring device are closed; after degassing is completed, an oil return valve of the current phase and an oil return valve in the online monitoring device are opened, the oil sample is discharged back into the transformer of the same phase, and gas of the current phase is detected; and after the main control board receives that the detection of the current phase is completed, the next phase is automatically switched for detection. The method has the advantages of high reliability, high practicability and the like, and the detection efficiency and accuracy can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of transformer online monitoring, and in particular to a time-sharing multiplexing transformer oil dissolved gas detection method and system. Background Art

[0002] With the increase in the number of large oil-filled power transformers and the increase in voltage levels, their safe and stable operation is directly related to the stable operation of the power grid. The gases dissolved in transformer oil mainly include hydrogen (H2), methane (CH4), ethane (C2H6), ethylene (C2H4), acetylene (C2H2), carbon monoxide (CO) and carbon dioxide (CO2), which are byproducts of the decomposition of the insulation materials inside the transformer under fault conditions such as overheating and discharge. The presence and content changes of these gases can reflect whether there are potential faults inside the transformer, such as local overheating, arc discharge, etc., and then help operation and maintenance personnel take timely measures to prevent accidents.

[0003] In the prior art, each transformer is usually equipped with a dedicated transformer oil spectrum online monitoring device. However, this configuration will lead to equipment redundancy in the case of multiple transformers, increase costs and reduce resource utilization efficiency. Summary of the invention

[0004] The technical problem to be solved by the present invention is: in view of the above-mentioned problems in the prior art, a time-sharing multiplexing transformer oil dissolved gas detection method and system with high detection efficiency and simple structure are provided.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A time-division multiplexing method for detecting dissolved gas in transformer oil enables an online monitoring device to detect oil samples in multiple transformer phases in sequence through a valve control strategy; the valve control strategy is to open only the oil inlet valve of the currently detected phase and the oil inlet valve inside the online monitoring device when detecting the oil sample in the transformer phase, so that the oil sample enters the degassing system inside the online monitoring device; after the oil inlet is completed, the oil inlet valve of the corresponding phase and the oil inlet valve inside the online monitoring device are closed; after the degassing is completed, the oil return valve of the current phase and the oil return valve inside the online monitoring device are opened, so that the oil sample is discharged back into the transformer of the same phase, and the gas in the current phase is detected; after the main control board receives the completion of the current phase detection, it automatically switches to the next phase for detection.

[0007] Furthermore, when switching to the next phase for detection, it also includes opening the oil inlet valve of the next phase so that the oil in the next phase discharges the residual oil in the pipeline into the oil-gas separation tank. After a specified period of time, the oil return valve of the previous phase is opened to discharge the residual oil back to the previous phase, and after closing the oil return valve, the oil sample in the next phase is detected.

[0008] Furthermore, the method also includes starting the oil sample in the next phase of the transformer to enter the degassing system inside the online monitoring device for degassing after the oil sample in the current phase enters the degassing system inside the online monitoring device to complete degassing.

[0009] Furthermore, it also includes controlling the volume ratio between the gas chamber and the oil sample according to a preset volume ratio to shorten the time to reach distribution equilibrium and improve degassing efficiency. The distribution equilibrium refers to the gas concentration in the gas phase and the concentration of the dissolved gas in the oil reaching a dynamic equilibrium point.

[0010] Furthermore, it also includes controlling the action logic of the oil inlet valve and the oil return valve through the main control board to ensure the correct operation sequence of the oil inlet valve and the oil return valve to prevent cross contamination between oil samples.

[0011] Furthermore, the detection method uses tunable semiconductor laser absorption spectroscopy technology, passes a frequency-scanned laser beam through the gas medium to be measured, and utilizes the high-resolution characteristics of the semiconductor laser light source to measure the gas concentration.

[0012] Furthermore, the detection method uses wavelength modulation spectroscopy technology to determine the concentration of the gas by modulating the wavelength of the laser, using the transmitted light signal received by the photodetector, and sending the signal to a phase-locked amplifier for demodulation.

[0013] A time-division multiplexing transformer oil dissolved gas detection system comprises a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute the time-division multiplexing transformer oil dissolved gas detection method.

[0014] A computer-readable storage medium stores a computer program / instruction, wherein the computer program / instruction is programmed or configured to execute the time-division multiplexing transformer oil dissolved gas detection method through a processor.

[0015] A computer program product comprises a computer program / instruction, wherein the computer program / instruction is programmed or configured to execute the time-division multiplexing transformer oil dissolved gas detection method through a processor.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] The present invention uses a valve control strategy to realize that one online monitoring device can detect oil samples in multiple transformer phases in sequence, without the need to configure independent detection equipment for each phase, which greatly improves the utilization rate of the equipment, reduces the investment cost of the equipment, and reduces the operating cost, especially in large-scale deployment, with significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of a method for detecting dissolved gas in transformer oil using time-sharing multiplexing according to an embodiment of the present invention.

[0019] Figure 2 It is a structural schematic diagram of a time-sharing multiplexed transformer oil dissolved gas detection system in a specific application embodiment of the present invention.

[0020] Figure 3 Schematic diagram of an online transformer oil spectrum monitoring device according to an embodiment of the present invention.

[0021] Figure 4 This is the head space degassing model of the embodiment of the present invention.

[0022] Figure 5 It is a schematic diagram of degassing results of the degassing model according to an embodiment of the present invention.

[0023] Figure 6 Schematic diagram of the wavelength modulation spectroscopy technology according to an embodiment of the present invention.

[0024] Figure 7 This is a gas detection optical path design diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 1As shown, in this embodiment, a time-division multiplexing method for detecting dissolved gas in transformer oil is used, and a valve control strategy is used so that an online monitoring device can detect oil samples in multiple transformer phases in sequence; the valve control strategy is that when detecting the oil sample in the transformer phase, only the oil inlet valve of the current detected phase and the oil inlet valve inside the online monitoring device are opened to allow the oil sample to enter the degassing system inside the online monitoring device; after the oil inlet is completed, the oil inlet valve of the corresponding phase and the oil inlet valve inside the online monitoring device are closed; after the degassing is completed, the oil return valve of the current phase and the oil return valve inside the online monitoring device are opened to discharge the oil sample back to the transformer of the same phase, and detect the gas in the current phase; after the main control board receives the completion of the current phase detection, it automatically switches to the next phase for detection.

[0027] like Figure 2 As shown, in a specific application embodiment, the step of detecting different phases of a multi-phase transformer includes:

[0028] Step 1, when detecting the transformer oil in phase A of #1 main transformer, the oil inlet valve of phase A of #1 main transformer is opened, the oil inlet valve inside the transformer oil spectrum online monitoring device is opened, and the oil enters the internal degassing system of the online monitoring device. After the oil is inlet, the oil inlet valve of phase A of #1 main transformer is closed, and the oil inlet valve inside the transformer oil spectrum online monitoring device is closed.

[0029] Step 2, after the detection is completed, the #1 main transformer A phase return oil valve is opened, the internal oil return valve of the transformer oil spectrum online monitoring device is opened, the oil is discharged back to the #1 main transformer A phase, and the detection is completed.

[0030] Step 3, after the main control board receives the detection of phase A of #1 main transformer, it starts to detect the transformer oil in phase B of #1 main transformer, the oil inlet valve of phase B of #1 main transformer is opened, the oil inlet valve inside the transformer oil spectrum online monitoring device is opened, and the oil enters the internal degassing system of the online monitoring device. After the oil is inlet, the oil inlet valve of phase B of #1 main transformer is closed, and the oil inlet valve inside the transformer oil spectrum online monitoring device is closed.

[0031] Step 4, after the detection is completed, the #1 main transformer B phase return oil valve is opened, the internal oil return valve of the transformer oil spectrum online monitoring device is opened, the oil is discharged back to the #1 main transformer B phase, and the detection is completed.

[0032] Step 5: After the main control board receives the detection of phase B of #1 main transformer, it starts to detect the transformer oil in phase C of #1 main transformer. The oil inlet valve of phase C of #1 main transformer is opened, and the oil inlet valve inside the transformer oil spectrum online monitoring device is opened, and the oil enters the internal degassing system of the online monitoring device. After the oil is inlet, the oil inlet valve of phase C of #1 main transformer is closed, and the oil inlet valve inside the transformer oil spectrum online monitoring device is closed.

[0033] Step 6, after the detection is completed, the oil return valve of phase C of #1 main transformer is opened, the internal oil return valve of the transformer oil spectrum online monitoring device is opened, and the oil is discharged back to phase C of #1 main transformer. At this point, the transformer oil detection in the three-phase main transformer A, B, and C of #1 main transformer is completed.

[0034] In this embodiment, when switching to the next phase for detection, it also includes opening the oil inlet valve of the next phase so that the oil in the next phase discharges the residual oil in the pipeline into the oil-gas separation tank. After a specified period of time, the oil return valve of the previous phase is opened to discharge the residual oil back to the previous phase. After closing the oil return valve, the oil sample in the next phase is detected.

[0035] Specifically, Figure 3 As shown, in order to prevent cross contamination between oil samples, the oil inlet valve of phase A of #1 main transformer is opened, and the oil inlet valves of the other two phases are kept closed. The oil sample can only enter the testing equipment through the oil inlet pipe to prevent the oil in phase A of #1 main transformer from entering other transformers. The common pipeline of the oil inlet pipe and the oil return pipe is as short as possible to reduce the residual oil from the previous test entering the transformer tested this time. Phase A test of #1 main transformer: open the oil inlet valve, the oil pump in the testing equipment rotates forward, and the oil in phase A of #1 main transformer enters the oil-gas separation tank. The oil inlet valve is closed after 20 seconds. It can be understood that the oil valve closing time can be adjusted according to actual production needs. Open the phase A return valve of #1 main transformer, and the oil pump reverses to discharge the oil back to phase A of #1 main transformer. Close the oil return valve, open the oil inlet valve, the oil pump rotates forward, and the oil enters the oil-gas separation tank. After the test is completed, open the phase A return valve of #1 main transformer, and the oil pump reverses to discharge the oil sample back to phase A of #1 main transformer. At this time, the phase A test of #1 main transformer is completed.

[0036] #1 main transformer B phase detection: open the oil inlet valve, the oil pump in the detection equipment rotates forward, the oil in the B phase of the #1 main transformer discharges the residual oil in the pipeline into the oil-gas separation tank, close the oil inlet valve after 20 seconds, open the A phase oil return valve of the #1 main transformer, and the oil pump reverses to discharge the residual oil back to the A phase of the #1 main transformer. Close the oil return valve, open the B phase oil inlet valve of the #1 main transformer, the oil pump rotates forward, and the oil enters the oil-gas separation tank. After the detection is completed, open the B phase oil return valve of the #1 main transformer, and the oil pump reverses to discharge the oil sample back to the B phase of the #1 main transformer. At this time, the B phase detection of the #1 main transformer is completed. #1 main transformer C phase detection: open the oil inlet valve, the oil pump in the detection equipment rotates forward, the oil in the C phase of the #1 main transformer discharges the residual oil in the pipeline into the oil-gas separation tank, close the oil inlet valve after 20 seconds, open the B phase oil return valve of the #1 main transformer, and the oil pump reverses to discharge the residual oil back to the B phase of the #1 main transformer. Close the oil return valve, open the #1 main transformer C phase oil inlet valve, the oil pump rotates forward, and the oil enters the oil-gas separation tank. After the detection is completed, open the #1 main transformer C phase oil return valve, and the oil pump reverses to discharge the oil sample back to the #1 main transformer C phase. At this time, the #1 main transformer C phase detection is completed.

[0037] In this embodiment, after the oil sample in the current phase enters the degassing system inside the online monitoring device and completes degassing, the oil sample in the next phase of the transformer is started to enter the degassing system inside the online monitoring device for degassing.

[0038] Specifically, after the degassing of phase A of the #1 main transformer is completed, when the gas detection of phase A of the #1 main transformer is proceeding normally, the oil and gas injection of phase B of the #1 main transformer begins. After the degassing of phase B of the #1 main transformer is completed, when the gas detection of phase B of the #1 main transformer is proceeding normally, the oil and gas injection of phase C of the #1 main transformer begins. This can greatly save detection time.

[0039] In this embodiment, the negative pressure constant temperature dynamic headspace method is used to degas the transformer oil sample. A certain method (negative pressure, stirring, constant temperature to 50 degrees) is used to make the dissolved gas in the oil quickly reach a distribution equilibrium in the gas-liquid two phases, calculate the concentration of each component in the gas phase, and calculate the concentration of each component of the dissolved gas in the oil based on the Ostwald coefficient derived from the gas-liquid equilibrium principle. The Ostwald coefficient is defined as:

[0040]

[0041] In the above formula, C oi and C gi is the concentration of component i distributed in the liquid and gas phases under equilibrium conditions; ki represents the Ostwald coefficient of component i.

[0042] For the online detection device for dissolved gas in transformer oil, the higher the concentration of the gas separated when the gas-liquid two-phase concentration ratio reaches equilibrium, the better. At the same time, the shorter the equilibrium time, the better, which can shorten the instrument detection interval and more effectively monitor the development of internal transformer faults. Therefore, the degassing rate and equilibrium time of the transformer oil degassing device are the most important.

[0043] The degassing rate is defined as:

[0044]

[0045] In the above formula, U gi and U oi are the concentrations of component i in the escaping gas in the gas phase and in the liquid phase, respectively.

[0046] like Figure 4As shown, in a closed container, the lower part is the transformer oil to be degassed, and the upper part is the air chamber. Under the action of free diffusion and stirring and other disturbances, the gas dissolved in the oil enters the top air chamber through the contact surface between the oil and the top gas, and gradually reaches equilibrium. If there is no stirring, the process of the gas dissolved in the oil escaping to the headspace mainly relies on the free diffusion of molecular thermal motion. According to Fico's law, the speed of gas molecule escape is proportional to the concentration difference on both sides of the oil surface and the headspace interface (the free diffusion process of gas molecules from oil to gas is relatively slow), and the resistance to escape lies in the adsorption of oil on gas molecules. From the above, it can be seen that the transfer rate equation of gas molecules at the interface, that is, the rate of change equation of the amount of gas molecules in the air chamber, is:

[0047]

[0048] In the above formula, n gi is the amount of substance of gas component i; and Respectively represent the concentration of gas component i in the oil and the concentration of gas component i in the gas phase at time t, kmol / m 3 ;k i is the Ostwald coefficient; D i It represents the diffusion coefficient of gas component i escaping from the interface to the gas chamber. It is a function of temperature, pressure, and interface area. When disturbances such as stirring are introduced, corrections need to be introduced.

[0049] When the volume of the oil sample is fixed, the total amount of gas component i is conserved, that is:

[0050]

[0051] In formula (6), V o and V g Represent the volumes of oil sample and gas chamber respectively; Combining equations (3) and (4), and considering the initial conditions t = 0, ng = 0, we can obtain the relationship between the amount of gas component i in the gas chamber and time:

[0052]

[0053] From formula (5), we can get that when t→∞, the equilibrium concentration of gas component i in the air chamber is:

[0054]

[0055] like Figure 5As shown, ideally, as the degassing time increases, the concentration of a certain component gas in the gas chamber continues to increase until it tends to a stable value, and the growth rate gradually decreases with the degassing time (of course, the curve obtained will be different due to different devices and parameters, but the overall trend should be consistent with the theoretical model). Generally, when the gas chamber concentration is 90% of the theoretical equilibrium concentration, it can be considered that the gas-liquid two phases have reached equilibrium. Assuming that the time of definition is the equilibrium time τ, that is:

[0056]

[0057] It can be clearly seen from equations (6) and (7) that the equilibrium concentration is only related to the original concentration of a certain component gas in the oil sample and the volume ratio of the gas chamber and the oil sample. g / V o , which can increase the gas phase concentration at the equilibrium moment and obtain a higher degassing rate; the specific structure of the degassing device (gas chamber volume and oil sample volume) determines the time required for equilibrium. The smaller the gas chamber volume and oil sample volume, the shorter the time required to reach equilibrium.

[0058] Therefore, under the premise of meeting the gas sample volume required by the gas detector, the size of the degassing bottle should be minimized. This embodiment controls the volume ratio between the gas chamber and the oil sample according to a preset volume ratio to shorten the time to reach distribution equilibrium and improve the degassing efficiency. Distribution equilibrium refers to the gas concentration in the gas phase and the concentration of the dissolved gas in the oil reaching a dynamic equilibrium point.

[0059] In this embodiment, the detection method uses tunable semiconductor laser absorption spectroscopy technology, passes a frequency-scanned laser beam through the gas medium to be measured, and uses the high-resolution characteristics of the semiconductor laser light source to measure the gas concentration.

[0060] In this embodiment, the detection method uses wavelength modulation spectroscopy technology to determine the concentration of the gas by modulating the wavelength of the laser, using the transmitted light signal received by the photodetector, and sending the signal to a phase-locked amplifier for demodulation.

[0061] Specifically, tunable semiconductor laser absorption spectroscopy (TDLAS) technology utilizes the ultra-narrow linewidth and tuning characteristics of the laser to scan a single absorption line of the gas. It has a very high spectral resolution and can effectively eliminate cross-interference from other gas spectral lines, ensuring the accuracy of multi-component gas feature identification.

[0062] TDLAS is essentially an absorption spectroscopy technique that obtains gas concentration by analyzing the selective absorption of light by the gas. However, unlike traditional infrared spectroscopy, the spectral width of the semiconductor laser light source it uses is much smaller than the broadening of the gas absorption spectrum. TDLAS is a high-resolution absorption spectroscopy technique. The attenuation of the light intensity of the semiconductor laser passing through the measured gas can be described by the Lambert-Beer law.

[0063] Assuming that the frequency-scanned laser beam passes through a gas medium with a length of L and a concentration of C, the absorption of laser energy by this gas medium satisfies the Lambert-Beer relationship:

[0064] I(V)=I0(V)exp(-α(V)CL), (8)

[0065] In the above formula, I(V) represents the light intensity after passing through the gas medium, I0 represents the light intensity incident on the gas medium, and α(V) represents the gas absorption coefficient.

[0066] Since the gas absorption coefficient is very small in the near-infrared band, it satisfies:

[0067] α(V)CL<<1,

[0068] Therefore, the right-hand side holds:

[0069] exp(-α(V)CL)=1-α(V)CL,

[0070] Therefore, the right formula can be used to approximate the absorption of gas

[0071] I(V)=I0(V)(1-α(V)CL),

[0072] The greater the gas concentration, the greater the attenuation of light. Therefore, the gas concentration can be measured by measuring the attenuation of the gas to the laser.

[0073] TDLAS can be divided into direct absorption spectroscopy and wavelength modulation absorption spectroscopy (WMS). Compared with direct absorption spectroscopy, WMS technology can effectively improve the stability of the system by setting a higher modulation frequency to improve detection accuracy and sensitivity.

[0074] like Figure 6 , Figure 7 As shown in the figure, the working principle of wavelength modulation spectroscopy technology is as follows: the wavelength of the laser is not only scanned within a certain range, but is also modulated by a high-frequency sinusoidal signal with a frequency of f. The photodetector receives the transmitted light absorbed by the gas to be measured, and converts the modulated light signal into an electrical signal, which is sent to the phase-locked amplifier. At the same time, a reference signal is input to the phase-locked amplifier, and the input modulated signal can be demodulated. The concentration of the gas can be determined based on the demodulated second harmonic 2f signal.

[0075] In addition, considering that the separate spectroscopic elements used in the wavelength division multiplexing technology for multi-component gas detection reduce the compactness and stability of the system, and the use of diffraction elements may also introduce standard tool noise, and there is cross interference between the detection channels of the frequency division modulation multiplexing technology, and the number of multi-channel lasers is limited. Time division multiplexing technology not only has a simple optical structure, only requires one set of signal conversion and processing system, but also has no technical limit on the number of lasers. Therefore, the time division multiplexing technology based on time-sharing scanning is used in the embodiment to realize real-time detection of multi-component gas.

[0076] It can be understood that, in addition to performing online monitoring of dissolved gas in oil for different phases of a transformer, the present invention can also perform online monitoring of dissolved gas in oil for transformer oils in multiple transformers using the above method.

[0077] In a specific application embodiment, according to the prior art solution, three sets of separate online monitoring devices are required to monitor the dissolved gas in the oil of a three-phase discrete transformer. The method of the present invention only requires one set, saving the cost of two sets. In addition, in the prior art, it takes six hours to obtain the data of the online monitoring device for dissolved gas in the oil of a three-phase discrete transformer. With the technical solution of the present invention, it only takes two hours to obtain all the data of three sets, which greatly saves time and saves precious time for early detection of faults.

[0078] This embodiment also provides a time-division multiplexing transformer oil dissolved gas detection system, including a microprocessor and a memory connected to each other, and the microprocessor is programmed or configured to execute the time-division multiplexing transformer oil dissolved gas detection method.

[0079] This embodiment also provides a computer-readable storage medium, in which a computer program / instruction is stored. The computer program / instruction is programmed or configured to execute a time-division multiplexing method for detecting dissolved gas in transformer oil through a processor.

[0080] This embodiment also provides a computer program product, including a computer program / instruction, which is programmed or configured to execute a time-division multiplexing method for detecting dissolved gas in transformer oil through a processor.

[0081] Those skilled in the art will appreciate that the above-mentioned embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the functions in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

[0082] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A time-division multiplexing method for detecting dissolved gas in transformer oil, characterized in that: Through the valve control strategy, an online monitoring device can detect oil samples in multiple transformer phases in turn; the valve control strategy is that when detecting the oil sample in the transformer phase, only the oil inlet valve of the current detected phase and the oil inlet valve inside the online monitoring device are opened to allow the oil sample to enter the degassing system inside the online monitoring device; after the oil inlet is completed, the oil inlet valve of the corresponding phase and the oil inlet valve inside the online monitoring device are closed; after the degassing is completed, the oil return valve of the current phase and the oil return valve inside the online monitoring device are opened to discharge the oil sample back to the transformer of the same phase, and the gas of the current phase is detected; after the main control board receives the completion of the current phase detection, it automatically switches to the next phase for detection.

2. The time-division multiplexing transformer oil dissolved gas detection method according to claim 1, characterized in that: When switching to the next phase for detection, it also includes opening the next phase oil inlet valve so that the oil in the next phase discharges the residual oil in the pipeline into the oil-gas separation tank. After a specified period of time, the previous phase oil return valve is opened to discharge the residual oil back to the previous phase. After closing the oil return valve, the oil sample in the next phase is detected.

3. The time-division multiplexing transformer oil dissolved gas detection method according to claim 1, characterized in that: The method further includes starting the degassing system for the oil sample in the next phase of the transformer to enter the degassing system inside the online monitoring device for degassing after the oil sample in the current phase enters the degassing system inside the online monitoring device to complete degassing.

4. The time-division multiplexing method for detecting dissolved gas in transformer oil according to any one of claims 1 to 3, characterized in that: It also includes controlling the volume ratio between the gas chamber and the oil sample according to a preset volume ratio to shorten the time to reach distribution equilibrium and improve degassing efficiency. The distribution equilibrium refers to the gas concentration in the gas phase and the concentration of the dissolved gas in the oil reaching a dynamic equilibrium point.

5. The time-division multiplexing method for detecting dissolved gas in transformer oil according to any one of claims 1 to 3, characterized in that: It also includes controlling the action logic of the oil inlet valve and the oil return valve through the main control board to ensure the correct operation sequence of the oil inlet valve and the oil return valve to prevent cross contamination between oil samples.

6. The time-division multiplexing transformer oil dissolved gas detection method according to claim 1, characterized in that: The detection method uses tunable semiconductor laser absorption spectroscopy technology, passes a frequency-scanned laser beam through the gas medium to be measured, and utilizes the high-resolution characteristics of the semiconductor laser light source to measure the gas concentration.

7. The time-division multiplexing transformer oil dissolved gas detection method according to claim 1, characterized in that: The detection method uses wavelength modulation spectroscopy technology to determine the concentration of the gas by modulating the wavelength of the laser, using the transmitted light signal received by the photodetector, and sending the signal to a phase-locked amplifier for demodulation.

8. A time-division multiplexing transformer oil dissolved gas detection system, comprising a microprocessor and a memory connected to each other, characterized in that: The microprocessor is programmed or configured to execute the time-division multiplexing method for detecting dissolved gas in transformer oil as described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program / instruction stored therein, characterized in that: The computer program / instruction is programmed or configured to execute the time-division multiplexing method for detecting dissolved gas in transformer oil through a processor.

10. A computer program product comprising a computer program / instructions, characterized in that The computer program / instruction is programmed or configured to execute the time-division multiplexing method for detecting dissolved gas in transformer oil through a processor.

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