Online monitoring system and method for dissolved gas in transformer oil

Abstract

The invention relates to the technical field of power equipment monitoring and fault diagnosis, and discloses a transformer oil dissolved gas online monitoring system and method, and the method comprises the steps: separating gas in oil through a degassing film at constant temperature and constant pressure, alternately separating seven key gas components through a dual-channel chromatographic column, and carrying out high-sensitivity detection through a mass spectrum unit, and high-temperature baking and inert purging self-cleaning are automatically executed in a chromatography switching gap. The system comprises a gas collection and pretreatment module, a two-channel chromatographic separation module, a mass spectrometry detection module, a self-cleaning maintenance module and a central control module, and full-process closed-loop control is realized. Through double-channel rotation and an intelligent self-cleaning mechanism, long-term stable operation is guaranteed, unattended full-automatic monitoring is supported, and the fault early warning capability and the equipment operation and maintenance efficiency are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power equipment monitoring and fault diagnosis, and particularly relates to an online monitoring system and method for transformer oil dissolved gas. BACKGROUND

[0002] With the continuous expansion of the scale of the power system and the increasing demand for intelligent operation and maintenance, the real-time sensing capability of the operation state of the transformer as the core power transmission and transformation equipment is directly related to the safety of the power grid and the reliability of power supply. The oil-immersed transformer will produce trace characteristic gases such as hydrogen, methane and acetylene due to partial discharge, overheating or insulation deterioration during long-term operation, and the changes in their components and concentrations are the key basis for judging internal latent faults. Traditional laboratory detection relies on offline sampling and large chromatography-mass spectrometry equipment, which has high resolution and high sensitivity, but is limited by equipment size, environmental requirements and operation complexity, and cannot be deployed on site in the substation to realize continuous online monitoring, resulting in a lag in fault warning.

[0003] Among them, for the online monitoring technology of dissolved gas in transformer oil, the current mainstream scheme mostly uses a single sensor array or a simplified chromatography structure, which can realize qualitative identification of part of the gas components, but has obvious shortcomings in multi-component synchronous separation capability, trace gas (such as ppb acetylene) quantitative precision and long-term stability. Especially under complex working conditions, gas cross interference, sensor drift and baseline noise accumulation often occur, which is difficult to meet the strict requirements of power equipment state evaluation on data accuracy and repeatability.

[0004] At the same time, the existing online device generally uses continuous or high-frequency sampling mode, without considering the pollution accumulation effect of the detection unit when exposed to the complex component environment of the oil in the industrial field for a long time, resulting in accelerated performance degradation of the core sensor element, shortened maintenance period and rising operation cost.

[0005] The existing technology faces three problems in realizing high-precision online monitoring: First, the physical conflict between laboratory-level separation detection capability and the demand for small size and low power consumption in field deployment; Second, the reliability conflict between irreversible accumulation of detection unit pollution and long-term stable operation under continuous sampling mode; Third, the efficiency conflict between the rapid response requirement of sudden fault gas and the energy saving and consumption reduction operation strategy under normal state.

[0006] The above contradictions together constitute the core technical bottleneck that needs to be broken through in the current online monitoring field of transformer oil dissolved gas. SUMMARY

[0007] The application provides a transformer oil dissolved gas online monitoring system and method, which realizes continuous, stable and high-sensitivity online monitoring of trace gases dissolved in transformer oil in a transformer substation or industrial site by constructing a set of high-precision gas separation and detection architecture with field deployment capability. The system adopts modular design in structure and comprises a gas collection and pretreatment unit, a double-channel chromatographic separation unit, a mass spectrometric detection unit, a self-cleaning maintenance unit and a central control and data processing unit. The units are physically connected and data are exchanged through standardized interfaces to form a closed-loop control system. The gas collection and pretreatment unit is responsible for extracting oil samples from the transformer body oil circuit and separating dissolved gases from the oil phase through a degassing membrane device. The degassing process adopts constant temperature and pressure control to ensure the stability and repeatability of gas release. After the degassed gas sample is adjusted to a constant flow rate by a precision flow controller, it enters the double-channel chromatographic separation unit.

[0008] Further, the double-channel chromatographic separation unit comprises a first chromatographic column and a second chromatographic column, which are arranged in parallel and operated alternately. The first chromatographic column is used for separation and analysis of the current batch of gas samples, and the second chromatographic column is in standby or self-cleaning state. The switching of the two chromatographic columns is automatically triggered by the central control unit according to the preset time period or the detection task completion state, ensuring that when the first chromatographic column completes separation and enters the regeneration stage, the second chromatographic column immediately takes over the sample injection and separation task of the next gas sample, thereby realizing uninterrupted continuous monitoring.

[0009] The first chromatographic column and the second chromatographic column are both filled with fixed phase materials of a specific polarity, the particle size distribution range is 3-5 μm, the column temperature control accuracy is ±0.1°, and the carrier gas flow rate is stabilized in the range of 1-3 ml / min, so as to ensure effective separation of seven key fault gases, i.e. hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide and carbon dioxide, and the retention time deviation of each component is less than 0.5%.

[0010] Further, the mass spectrometric detection unit is arranged at the downstream outlet end of the double-channel chromatographic separation unit, the ion source thereof adopts electron impact ionization mode, the ionization energy is set to 70 eV, the mass analyzer is a quadrupole structure, the mass scan range covers 1-150 atomic mass units, and the scan speed is greater than 10 times per second for full spectrum acquisition. The mass spectrometric detection unit is directly connected to the chromatographic column outlet through a zero dead volume joint to avoid diffusion or adsorption loss of the gas during transmission. After the detection signal is enhanced by a preamplifier, it is converted into a digital signal by a high-speed analog-to-digital converter and sent to the central control and data processing unit for spectrum analysis and component quantitative calculation. To prevent pollution of the ion source and detector caused by continuous sampling, the system automatically starts the self-cleaning maintenance unit during the interval of each chromatographic column switching.

[0011] Further, the self-cleaning maintenance unit comprises a high-temperature baking module and an inert gas purging module. The high-temperature baking module heats the chromatographic column and the ion source region of the mass spectrometer to 300℃ by resistance wire heating method, and the duration is 30 minutes, so that the high-boiling point residues adsorbed on the inner wall are volatilized and desorbed. The inert gas purging module then introduces high-purity nitrogen after the baking is completed, and the flow rate is set to 5 ml per minute, and the purging lasts for 10 minutes, so that the volatilized substances are completely discharged from the system. The self-cleaning process is monitored by the central control unit throughout the temperature and pressure parameters to ensure the cleaning effect while avoiding thermal stress damage to the precision components. After the self-cleaning is completed, the system automatically performs baseline calibration and sensitivity verification on the chromatographic column, and allows it to be put into operation again after confirming that it has returned to the initial performance indicators.

[0012] Further, the central control and data processing unit is the core operation and scheduling center, the hardware platform of which adopts an industrial-grade embedded processor, is equipped with a real-time operating system, and the software architecture comprises a task scheduling module, a data acquisition module, a spectrum analysis module, a concentration calculation module, an alarm judgment module and a remote communication module. The task scheduling module coordinates the timing execution of the gas collection, chromatographic separation, mass spectrometric detection and self-cleaning processes according to the preset monitoring period or external trigger instructions.

[0013] The data acquisition module synchronously records all process parameters such as chromatographic retention time, mass spectrometric ion intensity, temperature, pressure, flow rate, etc. The spectrum analysis module adopts a standard spectrum library matching algorithm, combines retention time window and characteristic ion peak intensity ratio double criteria, and identifies each gas component. The concentration calculation module quantifies according to the external standard method, converts the ion intensity into a gas concentration value in μL / L through a standard curve established in advance. The alarm judgment module compares the calculated concentration value with the preset threshold value, and if the concentration of any component exceeds the first threshold value, a warning signal is triggered; if it exceeds the second threshold value, a fault diagnosis report is immediately generated and pushed to the operation and maintenance platform. The remote communication module supports Ethernet and wireless communication protocols, realizes real-time uploading of monitoring data and remote parameter configuration.

[0014] As a preferred embodiment of the present application, the degassing membrane device adopts a polytetrafluoroethylene hollow fiber membrane structure, the membrane pore size is 0.2 μm, the membrane area is 50 m 2 A stirring paddle is arranged inside the degassing cavity, and the rotating speed is 60 revolutions per minute, so as to accelerate the mass transfer process of the gas in the oil phase to the membrane surface. The degassing temperature is controlled at 60℃, and the pressure is maintained at 0.1 MPa, so as to ensure that the single oil sample degassing operation is completed within 10 minutes.

[0015] As a preferred embodiment of the present application, the stationary phase of the first and second chromatographic columns is bonded polyethylene glycol, the column length is 30 m, the inner diameter is 0.32 mm, and the film thickness is 0.25 μm. The carrier gas is high-purity helium. The chromatographic column box is wrapped with multiple layers of thermal insulation material, and three groups of independent temperature control heating sheets are arranged inside to realize axial temperature gradient compensation and eliminate the retention time drift caused by environmental temperature fluctuations.

[0016] As a preferred embodiment of the present application, the detector of the mass spectrometry detection unit is an electron multiplier, and the gain coefficient is set to 10 6 , and the dynamic range covers 5 orders of magnitude. To improve the detection sensitivity of low-concentration components, in the mass-to-charge ratio interval corresponding to acetylene and hydrogen, the system automatically switches to selected ion monitoring mode, only collects specific ion peaks, reduces background noise interference, and the minimum detection limit reaches 0.1 μL / L.

[0017] As a preferred embodiment of the present application, the high-temperature baking module of the self-cleaning maintenance unit adopts a partitioned temperature control design, and the chromatographic column region and the ion source region are independently heated to avoid local overheating caused by uneven heat conduction. The baking temperature curve increases in three stages: the first stage increases from room temperature to 150℃ at a rate of 5℃ per minute; the second stage maintains a constant temperature for 10 minutes; and the third stage increases to 300℃ and maintains for 30 minutes. In addition to nitrogen, argon can also be used as a purge gas, with a purity higher than 99.995%, to ensure an oxygen-free environment to prevent oxidation of components.

[0018] As a preferred embodiment of the present application, the spectrum analysis module of the central control and data processing unit is built-in with an adaptive baseline correction algorithm, which can automatically identify and deduct the baseline drift before and after the chromatographic peak. The concentration calculation module supports dynamic calibration function, when the system detects standard gas samples, automatically updates the standard curve slope and intercept, compensates for the sensitivity decay caused by detector aging or environmental changes. The alarm judgment module adopts a multi-level threshold system, the first level threshold corresponds to the attention value, the second level threshold corresponds to the warning value, and the third level threshold corresponds to the action value, which are respectively associated with different response strategies.

[0019] As a preferred embodiment of the present application, two-stage filtering devices are arranged between the gas collection and pretreatment unit and the transformer oil circuit, the first stage is a stainless steel sintered filter element with a pore size of 10 μm for intercepting solid particles in the oil, and the second stage is a cellulose deep filter element with a pore size of 1 μm for removing gum and moisture. A pressure sensor is installed at the front end of the filtering device, and when the pressure difference exceeds 0.05 MPa, the system automatically sends a filter replacement prompt.

[0020] As a preferred embodiment of the present application, the connecting pipeline between the dual-channel chromatographic separation unit and the mass spectrometric detection unit adopts a silanized quartz capillary with an inner diameter of 0.1 mm and a length of not more than 20 cm, and the inert treatment of the pipe wall can effectively inhibit the adsorption of active components. The pipeline is wrapped with a heating belt outside, and the temperature is set consistent with the chromatographic column box to prevent gas condensation during transmission.

[0021] As a preferred embodiment of the present application, the remote communication module supports seamless docking with the substation monitoring system and can receive dispatching instructions to adjust the monitoring frequency. During the peak load period of the power grid, the system automatically switches to the fast scanning mode, shortening the single analysis period to 15 minutes; during the load valley period, the standard mode is restored, extending the analysis period to 30 minutes, and both the monitoring density and the equipment life are taken into account.

[0022] As a preferred embodiment of the present application, the central control and data processing unit is equipped with a local storage module, which can save original spectrum and concentration data for at least one year. The data uses a cyclic coverage mechanism, and when the storage space is full, the earliest data is automatically deleted. At the same time, the data export function is supported, and the historical data can be copied to an external storage device through a universal serial bus interface, which is convenient for offline analysis and audit traceability.

[0023] Compared with the prior art, the present application has the advantages and positive effects that: The present application realizes the high-precision gas component separation and detection capability close to the laboratory level in the industrial field environment for the first time by constructing a dual-channel alternating chromatographic separation architecture and cooperating with a full-automatic self-cleaning maintenance mechanism.

[0024] During continuous operation, the system effectively avoids the fixed phase degradation and detector pollution caused by long-term sampling of a single detection channel through the rotation and regeneration of the chromatographic column, prolongs the service life of the core components, and reduces the maintenance cost.

[0025] The mass spectrometric detection unit adopts a selected ion monitoring mode and a dynamic baseline correction algorithm, so that the detection sensitivity of key fault gases such as acetylene and hydrogen reaches the order of 0.1 μL / L, meeting the early latent fault diagnosis demand.

[0026] The central control unit integrates intelligent scheduling and adaptive calibration functions, which can dynamically adjust the monitoring strategy according to the power grid operation state to improve the system resource utilization efficiency.

[0027] The whole system can complete the whole process operation from oil sample collection, gas separation, component detection to data reporting without manual intervention, truly realizes unattended full-automatic online monitoring, and provides high-reliability data support for power equipment condition-based maintenance. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the overall technical scheme architecture diagram of the transformer oil dissolved gas online monitoring system and method provided by the present application; Figure 2 is the core principle framework diagram of the dual-channel chromatographic separation and self-cleaning maintenance cooperative operation in the present application; Figure 3 is the logic flow framework diagram of the gas collection pretreatment to mass spectrometry detection whole process in the present application; Figure 4 is the internal modular function interaction relationship diagram of the central control and data processing unit in the present application; Figure 5 is the multi-level interaction relationship and data flow diagram of the system and external power grid monitoring platform in the present application; DETAILED DESCRIPTION

[0029] Please refer to Figures 1-5 , the present application provides a kind of transformer oil dissolved gas online monitoring system and method, its core target is in substation or industrial field environment, realize the continuous, stable, high sensitivity online monitoring of trace gas dissolved in transformer oil, while solving the problem of detection unit pollution and service life attenuation caused by continuous sampling in prior art.The system is modular in structure, including gas collection pretreatment unit, dual-channel chromatographic separation unit, mass spectrometry detection unit, self-cleaning maintenance unit and central control and data processing unit.Each unit is connected and data is exchanged through standardized interface, forming a closed-loop control system to ensure long-term stable operation of the system under unattended conditions.

[0030] Gas collection pretreatment unit is responsible for extracting oil sample from transformer body oil circuit, and separating dissolved gas from oil phase by degassing membrane device.The degassing process adopts constant temperature and pressure control to ensure the stability and repeatability of gas release.After the degassed gas sample is adjusted to constant flow rate by precision flow controller, it enters the dual-channel chromatographic separation unit.The degassing membrane device adopts polytetrafluoroethylene hollow fiber membrane structure, with a membrane aperture of 0.2 μm and a membrane area of 50 m 2 .

[0031] Stirring paddle is arranged inside the degassing cavity, with a rotation speed of 60 revolutions per minute to accelerate the mass transfer process of gas in oil phase to the membrane surface.The degassing temperature is controlled at 60 DEG C, and the pressure is maintained at 0.1 MPa, to ensure that a single oil sample degassing operation is completed within 10 minutes.Two-stage filter device is arranged between the gas collection pretreatment unit and the transformer oil circuit, the first stage is stainless steel sintered filter element with a pore size of 10 μm for intercepting solid particles in oil, and the second stage is cellulose deep filter element with a pore size of 1 μm for removing gum and moisture.Pressure sensor is installed at the front end of the filter device, and the system automatically sends filter replacement prompt when the pressure difference exceeds 0.05 MPa.

[0032] The double-channel chromatographic separation unit comprises a first chromatographic column and a second chromatographic column, which are arranged in parallel and alternately operated. The first chromatographic column is used for separation and analysis of the current batch of gas samples, and the second chromatographic column is in standby or self-cleaning state. The switching of the two chromatographic columns is automatically triggered by the central control unit according to the preset time period or the detection task completion state, ensuring that when the first chromatographic column completes separation and enters the regeneration phase, the second chromatographic column immediately takes over the sample injection and separation task of the next gas sample, thereby realizing uninterrupted continuous monitoring.

[0033] The first chromatographic column and the second chromatographic column are both filled with fixed phase material of a specific polarity, with a particle size distribution range of 3-5 μm, a column temperature control accuracy of ±0.1°, and a carrier gas flow rate stabilized within 1-3 ml / min, to ensure effective separation of seven key fault gases, namely hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide and carbon dioxide, with a retention time deviation of less than 0.5% for each component. The fixed phase of the first chromatographic column and the second chromatographic column is bonded polyethylene glycol, with a column length of 30 m, an inner diameter of 0.32 mm, and a film thickness of 0.25 μm. The carrier gas is high-purity helium.

[0034] The chromatographic column box is wrapped with multiple layers of thermal insulation material, and three independent temperature control heating sheets are arranged inside to realize axial temperature gradient compensation and eliminate retention time drift caused by environmental temperature fluctuations. The connecting pipeline between the double-channel chromatographic separation unit and the mass spectrometric detection unit uses a silanized quartz capillary with an inner diameter of 0.1 mm and a length of not more than 20 cm, and the inert treatment of the pipe wall can effectively inhibit the adsorption of active components. The pipeline is wrapped with a heating band outside, with a temperature setting consistent with that of the chromatographic column box, to prevent gas condensation during transmission.

[0035] The mass spectrometric detection unit is arranged at the downstream outlet end of the double-channel chromatographic separation unit, its ion source adopts electron impact ionization mode with an ionization energy of 70 eV, and the mass analyzer is a quadrupole structure with a mass scan range covering 1-150 atomic mass units and a scan speed higher than 10 times per second for full spectrum acquisition. The mass spectrometric detection unit is directly connected to the chromatographic column outlet through a zero dead volume joint to avoid diffusion or adsorption loss of the gas during transmission. After the detection signal is enhanced by a preamplifier, it is converted into a digital signal by a high-speed analog-to-digital converter and sent to the central control and data processing unit for spectrum analysis and component quantitative calculation.

[0036] The detector of the mass spectrometric detection unit is an electron multiplier with a gain coefficient set to 10 6 , covering a dynamic range of 5 orders of magnitude. To improve the detection sensitivity of low-concentration components, the system automatically switches to selected ion monitoring mode in the mass-to-charge ratio range corresponding to acetylene and hydrogen, only collecting specific ion peaks to reduce background noise interference, so that the minimum detection limit reaches 0.1 μL / L.

[0037] The self-cleaning maintenance unit includes a high-temperature baking module and an inert gas purging module. The high-temperature baking module heats the chromatographic column and the mass spectrometry ion source region to 300°C by resistance wire heating for 30 minutes, so that high-boiling point residues adsorbed on the inner wall are volatilized and desorbed. The inert gas purging module then introduces high-purity nitrogen after the baking is completed, with a flow rate set at 5 ml per minute, and continues to purge for 10 minutes to completely remove the volatiles from the system. The self-cleaning process is monitored by the central control unit throughout the temperature and pressure parameters to ensure the cleaning effect while avoiding thermal stress damage to the precision components. After the self-cleaning is completed, the system automatically performs baseline calibration and sensitivity verification on the chromatographic column, and confirms that it returns to the initial performance indicators before allowing it to be put back into operation.

[0038] The high-temperature baking module adopts a zoned temperature control design, with the chromatographic column region and the ion source region heated independently to avoid local overheating caused by uneven heat conduction. The baking temperature curve increases in three stages: the first stage rises from room temperature to 150°C at a rate of 5°C per minute; the second stage maintains a constant temperature for 10 minutes; and the third stage rises to 300°C and maintains for 30 minutes. In addition to nitrogen, argon can also be used as the purging gas to ensure an oxygen-free environment to prevent oxidation of the components.

[0039] The central control and data processing unit is the core operation and scheduling center, with an industrial-grade embedded processor as its hardware platform and a real-time operating system. The software architecture includes a task scheduling module, a data acquisition module, a spectrum analysis module, a concentration calculation module, an alarm judgment module, and a remote communication module. The task scheduling module coordinates the timing execution of gas collection, chromatographic separation, mass spectrometry detection, and self-cleaning processes according to the preset monitoring period or external trigger instructions.

[0040] The data acquisition module synchronously records all process parameters such as chromatographic retention time, mass spectrometry ion intensity, temperature, pressure, and flow rate. The spectrum analysis module uses a standard spectrum library matching algorithm combined with a retention time window and a characteristic ion peak intensity ratio double criterion to identify each gas component. The concentration calculation module quantifies by external standard method, converts ion intensity to gas concentration value in μL / L through a pre-established standard curve. The alarm judgment module compares the calculated concentration value with the preset threshold value, and if the concentration of any component exceeds the first threshold value, a warning signal is triggered; If the secondary threshold is exceeded, a fault diagnosis report is immediately generated and pushed to the operation and maintenance platform. The remote communication module supports Ethernet and wireless communication protocols, enabling real-time uploading of monitoring data and remote parameter configuration. The spectrum analysis module has a built-in adaptive baseline correction algorithm that can automatically identify and deduct baseline drift before and after the chromatographic peak. The concentration calculation module supports dynamic calibration. When the system detects a standard gas sample, it automatically updates the standard curve slope and intercept to compensate for sensitivity decay caused by detector aging or environmental changes. The alarm judgment module uses a multi-level threshold system, with the first threshold corresponding to the attention value, the second threshold corresponding to the warning value, and the third threshold corresponding to the action value, each associated with a different response strategy.

[0041] The central control and data processing unit is equipped with a local storage module that can save at least one year of raw spectrum and concentration data. The data uses a circular coverage mechanism, automatically deleting the earliest data when the storage space is full. It also supports data export function, which can copy historical data to external storage devices through USB interface, facilitating offline analysis and audit traceability. The remote communication module supports seamless integration with the substation monitoring system and can receive dispatching instructions to adjust the monitoring frequency. During peak load periods, the system automatically switches to fast scanning mode, shortening the single analysis period to 15 minutes; during the load valley period, it restores to the standard mode, extending the analysis period to 30 minutes, balancing monitoring density and equipment life.

[0042] During system startup, the central control and data processing unit first performs a self-test program, which sequentially detects the pressure sensor status of the gas collection and pretreatment unit, the temperature and stirring mechanism operating status of the degassing membrane device, the carrier gas flow rate and column temperature stability of the dual-channel chromatographic separation unit, the ion source voltage and detector gain coefficient of the mass spectrometry detection unit, and the heating resistance and purge gas path tightness of the self-cleaning maintenance unit. After passing the self-test, the system enters standby mode, waiting for the first oil sample collection instruction.

[0043] The first collection is triggered by a timer or initiated by a remote instruction from the external monitoring platform. The gas collection and pretreatment unit starts the oil pump to extract 50 ml of oil sample from the transformer body oil line. After passing through two-stage filtration devices, the oil sample enters the degassing cavity. The degassing cavity operates at a constant temperature of 60°C, with a stirring paddle rotating at a speed of 60 revolutions per minute, while maintaining a cavity pressure of 0.1 MPa. The degassing process lasts for 10 minutes, during which the dissolved gas passes through the polytetrafluoroethylene hollow fiber membrane into the gas phase space, and is introduced into the first chromatographic column after being adjusted to a flow rate of 2 ml per minute by a precision flow controller.

[0044] The first chromatographic column operates in the thermostat body, and the column temperature is accurately controlled in the range of 50±0.1℃. The carrier gas is high-purity helium, and the flow rate is stabilized at 2ml per minute. The gas sample is separated in the chromatographic column according to the difference in the interaction force between each component and the stationary phase. Hydrogen is first discharged, followed by methane, carbon monoxide, ethane, ethylene, acetylene, and carbon dioxide in turn. The retention time of each component is recorded in real time by the central control unit and compared with the pre-stored standard retention time table. If the deviation exceeds 0.5%, an abnormal performance alarm of the chromatographic column is triggered.

[0045] The separated gas components enter the mass spectrometry detection unit in turn. The ion source ionizes the molecules at an energy of 70eV. The quadrupole mass analyzer collects ion current signals with a mass-to-charge ratio ranging from 1 to 150 according to a pre-set scanning program. For acetylene and hydrogen, the system automatically switches to the selected ion monitoring mode, and only collects characteristic ion peaks with a mass-to-charge ratio of 26 and 2 to improve the signal-to-noise ratio. The detection signal is enhanced by a preamplifier and converted into a digital signal by a 12-bit high-speed analog-to-digital converter at a sampling rate of 100,000 times per second, and then sent to the spectrum analysis module.

[0046] The spectrum analysis module first performs adaptive baseline correction. The baseline drift trend before and after the chromatographic peak is identified by a sliding window algorithm, and the trend component is deducted from the original signal. Subsequently, the module identifies the components according to the retention time window and the characteristic ion peak intensity ratio double criteria. After identification, the concentration calculation module substitutes the ion current intensity peak value of each component into the pre-stored standard curve according to the external standard method to calculate the corresponding gas concentration. The standard curve is established by the system using standard gas samples before leaving the factory, and the slope and intercept are stored in the non-volatile memory. The concentration calculation module supports dynamic calibration function. When the system detects the built-in standard gas sample, it automatically collects its ion current intensity and re-fits the standard curve to update the slope and intercept values to compensate for the decay of detector sensitivity over time.

[0047] The calculated concentration value is sent to the alarm judgment module and compared with a three-level threshold system. The first threshold is the attention value, corresponding to 100μL / L of hydrogen, 120μL / L of methane, and 1μL / L of acetylene; the second threshold is the warning value, corresponding to 500μL / L of hydrogen, 200μL / L of methane, and 5μL / L of acetylene; and the third threshold is the action value, corresponding to 1000μL / L of hydrogen, 500μL / L of methane, and 10μL / L of acetylene. If the concentration of any component exceeds the first threshold, the system displays a yellow warning icon on the local human-machine interface and records the event log; if it exceeds the second threshold, the system generates a fault diagnosis report containing the name of the over-standard component, the concentration value, the over-standard multiple, and the recommended treatment measures, and pushes it to the operation and maintenance platform through the remote communication module; if it exceeds the third threshold, the system not only pushes the report, but also automatically sends an emergency shutdown recommendation instruction to the substation monitoring system.

[0048] After the first chromatographic column completes the gas separation task, the central control unit triggers the chromatographic column switching instruction immediately, switches the gas sample flow path to the second chromatographic column, and starts the self-cleaning process of the first chromatographic column. The self-cleaning process includes two stages: high-temperature baking and inert gas purging. In the high-temperature baking stage, the central control unit activates the independent heating sheet of the chromatographic column region and the ion source region, and heats according to a three-stage temperature curve: in the first stage, the temperature is raised from room temperature to 150°C at a rate of 5°C per minute, which takes 30 minutes; in the second stage, the temperature is kept constant for 10 minutes; in the third stage, the temperature continues to rise to 300°C and maintains for 30 minutes. During the baking process, the system monitors the temperature of each region in real time, and if the temperature rise rate deviates from the set value by more than 10%, the heating is suspended and a heating sheet fault alarm is triggered.

[0049] After baking, the system turns off the heating sheet, starts the inert gas purging module, and introduces high-purity nitrogen at a flow rate of 5 ml per minute for 10 minutes. The purging gas is discharged outside the system through a special exhaust pipeline to avoid environmental pollution. After purging, the system performs baseline calibration and sensitivity verification on the first chromatographic column: injects a small amount of standard gas sample, collects its chromatographic peak area and retention time, and compares it with the historical baseline value. If the peak area decays by more than 5% or the retention time drifts by more than 0.5%, the cleaning is not complete and the self-cleaning process is repeated; if the verification is passed, the first chromatographic column is marked as "on standby" state, waiting for the next switching instruction.

[0050] The second chromatographic column repeats the above separation, detection, calculation, and alarm process after receiving the gas sample. The two chromatographic columns operate alternately to ensure that one chromatographic column is always in working state and the other is in cleaning or standby state during continuous monitoring. The task scheduling module of the central control unit dynamically adjusts the monitoring period according to the load state of the power grid: during the peak load period, the single analysis period is shortened to 15 minutes to increase the data update frequency; during the valley load period, the analysis period is extended to 30 minutes to reduce equipment wear. All raw spectra, concentration data, alarm records, and self-cleaning logs are stored in the local storage module, which uses a circular coverage mechanism to manage the storage space.

[0051] Users can connect external storage devices through a universal serial bus interface to export all data within a specified time period for offline analysis or audit traceability. The remote communication module supports Ethernet and wireless communication protocols, and can receive parameter adjustment instructions issued by the substation monitoring system, such as modifying alarm thresholds, adjusting monitoring periods, and forcing the start of the self-cleaning process, to realize remote operation and maintenance and centralized management.

[0052] The present application realizes the high-precision gas component separation and detection ability close to the laboratory level in the industrial field environment for the first time by constructing a double-channel alternating operation chromatographic separation architecture and cooperating with a full-automatic self-cleaning maintenance mechanism. In the continuous operation process, the system effectively avoids the fixed phase degradation and detector pollution caused by long-term sampling of a single detection channel through the rotation and regeneration of the chromatographic column, prolongs the service life of the core components, and reduces the maintenance cost. The mass spectrometry detection unit adopts the selected ion monitoring mode and the dynamic baseline correction algorithm, so that the detection sensitivity of key fault gases such as acetylene and hydrogen reaches the 0.1 μL / L level, meeting the early latent fault diagnosis demand.

[0053] The central control unit integrates intelligent scheduling and adaptive calibration functions, which can dynamically adjust the monitoring strategy according to the power grid operation state, and improve the system resource utilization efficiency. The whole system can complete the whole process operation from oil sample collection, gas separation, component detection to data reporting without manual intervention, and truly realizes the unattended full-automatic online monitoring, and provides high-reliability data support for power equipment condition-based maintenance.

[0054] It should be noted that, in this text, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the term "include" "contain" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0055] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An on-line monitoring method of dissolved gases in transformer oil, characterized in that, The application relates to a transformer oil gas chromatography and mass spectrometry detection system. The system comprises the following steps: An oil sample is extracted from a transformer body oil circuit through a gas collection pretreatment unit, and dissolved gas is separated from the oil phase under constant temperature and pressure conditions through a degassing membrane device; The degassed gas sample is introduced into a double-channel chromatographic separation unit after being adjusted to a constant flow rate by a precision flow controller, the double-channel chromatographic separation unit comprises a first chromatographic column and a second chromatographic column, and the two columns are alternately operated, wherein when one chromatographic column performs a current gas sample separation task, the other chromatographic column is in standby or self-cleaning state; Each gas component after chromatographic separation is detected through a mass spectrometry detection unit, the mass spectrometry detection unit is arranged at the outlet end of the chromatographic column, adopts an electron impact ionization mode and a quadrupole mass analyzer, and the mass scanning range covers 1-150 atomic mass units; In the chromatographic column switching gap, a self-cleaning maintenance unit is started to perform high-temperature baking and inert gas blowing on the chromatographic column just completing the separation task and the mass spectrometry ion source area; The chromatographic retention time, mass spectrometry ion flow intensity, temperature, pressure and flow parameters are synchronously collected through a central control and data processing unit, a standard spectrum library matching algorithm is adopted to identify the gas components in combination with a retention time window and a characteristic ion peak intensity ratio double criterion, and the ion flow intensity is converted into a gas concentration value according to an external standard method; 2. The transformer oil dissolved gas online monitoring method of claim 1, wherein, The degassing membrane device adopts a polytetrafluoroethylene hollow fiber membrane structure, the membrane aperture is 0.2 μm, the membrane area is 50 cm 2 , a stirring paddle is arranged in the degassing cavity, the rotating speed is 60 revolutions per minute, the degassing temperature is controlled at 60 DEG C, the pressure is maintained at 0.1 MPa, and a single degassing operation is completed within 10 minutes.

3. The transformer oil dissolved gas online monitoring method of claim 2, wherein, Based on the comparison result of the calculated gas concentration value and the preset multi-level threshold value, a corresponding level of early warning or fault diagnosis report is triggered, and the report is uploaded to an operation and maintenance platform through a remote communication module.

4. The transformer oil dissolved gas online monitoring method of claim 3, wherein, The first chromatographic column and the second chromatographic column are filled with bonded polyethylene glycol stationary phase, the column length is 30 m, the inner diameter is 0.32 mm, the film thickness is 0.25 mu m, the carrier gas is high-purity helium, the flow rate is stabilized at 1-3 ml per minute, the column temperature control precision is +0.1 DEG, and the retention time deviation of each component is less than 0.5%.

5. The transformer oil dissolved gas online monitoring method of claim 4, wherein, The mass spectrometry detection unit is automatically switched to a selected ion monitoring mode when detecting acetylene and hydrogen, only the characteristic ion peaks with mass-to-charge ratios of 26 and 2 are collected, the detector is an electron multiplier, the gain coefficient is 10 to the power of 6, the dynamic range covers 5 orders of magnitude, and the minimum detection limit reaches 0.1 mu l / L.

6. The transformer oil dissolved gas online monitoring method of claim 5, wherein, When the self-cleaning maintenance unit performs high-temperature baking, a partition temperature control design is adopted, the chromatographic column area and the ion source area are independently heated, the baking temperature curve is increased in three stages: the first stage is from room temperature to 150 DEG C at a rate of 5 DEG C per minute; the second stage is constant temperature keeping for 10 minutes; the third stage is increased to 300 DEG C and maintained for 30 minutes; after the baking is completed, high-purity nitrogen or argon is introduced, the flow rate is 5 ml per minute, and the blowing is continued for 10 minutes.

7. The transformer oil dissolved gas online monitoring method of claim 6, wherein, The central control and data processing unit is internally provided with an adaptive baseline correction algorithm, baseline drifts before and after chromatographic peaks are identified and deducted through a sliding window; the concentration calculation module supports a dynamic calibration function, and when a standard gas sample is detected, the standard curve slope and intercept are automatically updated. The hardware platform of the central control and data processing unit adopts an industrial-grade embedded processor, is equipped with a real-time operating system, and the software architecture comprises a task scheduling module, a data acquisition module, a spectrum analysis module, a concentration calculation module, an alarm judgment module and a remote communication module. The alarm judgment module adopts a three-level threshold system: the first level threshold corresponds to the attention value, the second level threshold corresponds to the warning value, and the third level threshold corresponds to the action value; when the hydrogen concentration exceeds 100 muL / L, the methane exceeds 120 muL / L, or the acetylene exceeds 1 muL / L, the first level early warning is triggered; when the hydrogen exceeds 500 muL / L, the methane exceeds 200 muL / L, or the acetylene exceeds 5 muL / L, the second level report is triggered; when the hydrogen exceeds 1000 muL / L, the methane exceeds 500 muL / L, or the acetylene exceeds 10 muL / L, the third level emergency response is triggered.

8. The transformer oil dissolved gas online monitoring method of claim 7, wherein, The task scheduling module of the central control and data processing unit dynamically adjusts the monitoring period according to the power grid load state: shortens the single analysis period to 15 minutes during the load peak period, and extends to 30 minutes during the load valley period; The local storage module saves at least one year of original spectrum and concentration data, uses a cyclic coverage mechanism to manage the storage space, and supports exporting historical data through a universal serial bus interface.

9. An on-line transformer oil dissolved gas monitoring system characterized by, It comprises: A gas collection and pretreatment unit is used to extract oil samples from the transformer body oil circuit and separate dissolved gas from the oil phase under constant temperature and pressure conditions through a degassing membrane device; A dual-channel chromatographic separation unit includes a first chromatographic column and a second chromatographic column, which are alternately operated. When one chromatographic column performs the current gas sample separation task, the other chromatographic column is in standby or self-cleaning state; A mass spectrometry detection unit is arranged at the outlet end of the chromatographic column and is used to detect each gas component after chromatographic separation. Electron impact ionization and quadrupole mass analyzer are used, and the mass scan range covers 1 to 150 atomic mass units; A self-cleaning and maintenance unit is used to perform high-temperature baking and inert gas purging on the chromatographic column and mass spectrometry ion source area that have just completed the separation task during the chromatographic column switching gap; A central control and data processing unit is used to synchronously collect chromatographic retention time, mass spectrometry ion current intensity, temperature, pressure, and flow parameters. Standard spectrum library matching algorithm is used in combination with retention time window and characteristic ion peak intensity ratio double criterion to identify gas components. Ion current intensity is converted into gas concentration value according to external standard method. According to the comparison result of the calculated gas concentration value and the preset multi-level threshold value, the corresponding level of early warning or fault diagnosis report is triggered, and is uploaded to the operation and maintenance platform through the remote communication module.

10. The transformer oil dissolved gas online monitoring system of claim 9, wherein, Two-stage filter devices are arranged between the gas collection and pretreatment unit and the transformer oil circuit. The first stage is a stainless steel sintered filter element with a pore size of 10 muM, and the second stage is a cellulose deep filter element with a pore size of 1 muM. A pressure sensor is installed at the front end. When the pressure difference exceeds 0.05 MPa, an automatic filter replacement prompt is sent. A silanized quartz capillary is used to connect the dual-channel chromatographic separation unit and the mass spectrometry detection unit. The inner diameter is 0.1 mm, the length is not more than 20 cm, and the outside is wrapped with a heating band with the same temperature as the chromatographic column box.

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