Online monitoring system for gas dissolved in oil and headspace elution split-flow concentration oil-gas separation method thereof

Abstract

The invention relates to the technical field of analysis and detection of gas dissolved in oil in an electric power system, and discloses an online monitoring system for gas dissolved in oil and a headspace elution split-flow concentration oil-gas separation method thereof, the system comprises an oil cylinder, a stepping motor, a buffer chamber, a chromatographic analysis module, a standard gas steel cylinder, a heating control module, a valve, a gas pump and a pipeline; wherein the oil cylinder and the stepping motor are horizontally arranged, a lead screw of the stepping motor is connected with a piston in the oil cylinder, and the heating control modules are arranged on the outer sides of the oil cylinder and the chromatographic analysis module; the invention also provides a headspace elution split-flow concentration oil-gas separation method of the online monitoring system for dissolved gas in oil, the headspace elution split-flow concentration oil-gas separation does not need to complete rapid headspace degassing under an ultimate vacuum condition, the degassing time is effectively shortened, and the method is similar to a conventional offline degassing method, so that the cost is reduced. The influence of the vacuum degree and the vacuum degassing rate on an analysis result does not need to be considered, and the device has the advantages of simple structure and good repeatability.

Description

Technical Field

[0001] This invention relates to the field of dissolved gas analysis and detection technology in power systems, and more specifically, to an online monitoring system for dissolved gases in oil and a headspace elution, diversion, and concentration method for oil-gas separation. Background Technology

[0002] Transformers are among the most important electrical devices in a power system, and ensuring their reliable operation is of great significance for improving the power supply reliability of the system. Dissolved gas analysis (DGA) in oil is recognized in the industry as one of the most effective methods for preventing failures in oil-filled electrical equipment. The standard DL / T 596-2005 "Preventive Testing Procedures for Power Equipment" lists gas chromatography analysis as the first of all test items.

[0003] Laboratory gas chromatography is currently one of the main methods for analyzing dissolved gases in oil. With technological advancements, online dissolved gas detection in oil has gradually gained wider application. This method involves connecting an online dissolved gas analyzer to a transformer to monitor the composition and content of dissolved gases in the oil in real time.

[0004] Oil-gas separation is an indispensable step in the analysis of dissolved gases in oil. Currently, commonly used oil-gas separation methods include membrane degassing, dynamic headspace degassing, and vacuum degassing. Membrane degassing has a long equilibrium time and low degassing efficiency, failing to meet the requirements for time-sensitive aging. Dynamic headspace degassing mainly suffers from the following problems: it requires gas replenishment during degassing, and waste oil needs to be treated before being pumped back to the main transformer. Vacuum degassing has a complex device structure, a long degassing time, and its degassing rate is easily affected by the gas content in the oil, resulting in poor repeatability.

[0005] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0006] To address the problems in related technologies, this invention proposes an online monitoring system for dissolved gases in oil and a headspace elution and diversion concentration method for oil-gas separation, in order to overcome the aforementioned technical problems existing in the prior art.

[0007] Therefore, the specific technical solution adopted by the present invention is as follows:

[0008] According to one aspect of the present invention, an online monitoring system for dissolved gases in oil is provided, comprising a hydraulic cylinder, a stepper motor, a buffer chamber, a chromatographic analysis module, a standard gas cylinder, and a heating control module; wherein the hydraulic cylinder and the stepper motor are horizontally arranged, and the lead screw of the stepper motor is connected to the piston inside the hydraulic cylinder; a heating control module is provided on the outside of both the hydraulic cylinder and the chromatographic analysis module; one side of the bottom of the hydraulic cylinder is connected in sequence to a solenoid valve V1, a three-way valve V15, and the oil port of a transformer via an oil inlet pipe; another side of the bottom of the hydraulic cylinder is also connected in sequence to a solenoid valve V2, a three-way valve V16, and the oil port of the transformer via a return oil pipe; the other side of the bottom of the hydraulic cylinder is connected in sequence to a solenoid valve V13, a gas pump B1, a solenoid valve V4, and the top of the buffer chamber via a pipe; the top of the hydraulic cylinder is connected in sequence to a solenoid valve V3 and the bottom of the buffer chamber via a pipe; the buffer chamber... The top of the buffer chamber is connected to solenoid valve V12 and port I of the six-way valve via pipelines. The top of the buffer chamber is also connected to solenoid valve V14 via pipelines. Port II of the six-way valve is connected to solenoid valves V6, V5, and V9 via pipelines. The other end of solenoid valve V6 is connected to the chromatographic analysis module. The other end of solenoid valve V5 is connected to the standard gas cylinder. The other end of solenoid valve V9 is connected to solenoid valves V10, V13, and air pump B1. The other end of solenoid valve V10 is connected to air pump B2. The top of the cylinder is equipped with a left limit sensor, a middle limit sensor, and a right limit sensor in sequence. Pressure sensor P1 and temperature sensor T1 are installed on the oil inlet and return pipelines. Pressure sensor P2 and liquid level sensor L1 are installed on one side of the bottom of the buffer chamber. Pressure sensor P3 is connected to the pressure stabilizing valve.

[0009] Furthermore, the chromatographic analysis module includes a carrier gas generator, a pressure regulating valve, a gas detector, a chromatographic column, a six-way valve, a solenoid valve V8, and a solenoid valve V11. One side of the carrier gas generator is connected sequentially via piping to the pressure regulating valve, solenoid valve V8, gas detector, chromatographic column, and the interface V of the six-way valve. The interface IV of the six-way valve is connected via piping to the solenoid valve V11, the pressure regulating valve, and the solenoid valve V6. The gas detector and the chromatographic column together constitute the chromatographic analysis component, and a heating control module is located on the outer side of the chromatographic analysis component.

[0010] Furthermore, in the injection state, the pressure regulating valve is connected via tubing to port IV, port III, the metering tube in the six-way valve, port VI, port V, the chromatographic column, and the gas detector. The buffer chamber is connected via tubing to port I and port II of the six-way valve. In the degassing state, the pressure regulating valve is connected via tubing to port IV, port V, the chromatographic column, and the gas detector. The buffer chamber is connected via tubing to port I, port VI, the metering tube in the six-way valve, port III, and port II of the six-way valve.

[0011] According to another aspect of the present invention, an oil-gas separation method using headspace elution splitting concentration in an online monitoring system for dissolved gases in oil is provided, comprising the following steps:

[0012] S1. By controlling the stepper motor to drive the piston of the oil cylinder to move left and right, and in conjunction with solenoid valve V1, solenoid valve V2, pressure sensor, limit sensor and liquid level sensor, the circulation and quantitative control of oil sample are completed.

[0013] S2. Control the stepper motor to pull the piston to the right limit, forming a gas and liquid two-phase system inside the oil cylinder; the gas dissolved in the oil is transferred from the liquid phase to the gas phase by the air pump B1, and accumulates at the top of the oil cylinder and in the buffer chamber; after the bubbling degassing is completed, the piston position is adjusted by controlling the stepper motor to push the piston rod, and the sample gas accumulated in the oil cylinder is transferred to the buffer chamber and the metering tube in the six-way valve.

[0014] S3. Use a multi-objective optimization algorithm to determine the heating parameters of the chromatographic analysis component at each heating stage, and control the heating control module to heat the chromatographic analysis component according to the determined heating parameters so that the temperature of the chromatographic analysis component meets the detection requirements at different stages.

[0015] S4. After degassing is completed, switch the six-way valve to the injection state so that the degassed gas enters the heated chromatographic analysis unit and the concentration of each component in the gas sample is obtained by analysis of the chromatographic analysis unit.

[0016] Furthermore, prior to step S1, there are also processes for initialization, airtightness check, and gas path cleaning.

[0017] The initialization process includes:

[0018] Initialize the six-way valve to the degassing state, initialize and close all valves and pumps, and start the aging process of the chromatography analysis module;

[0019] The airtightness inspection process includes:

[0020] Determine the piston position. If it is at the left limit, perform a cylinder airtightness test; if it is not at the left limit, open solenoid valve V2 and perform a cylinder reset.

[0021] The stepper motor is controlled to pull the cylinder piston from the left limit to the right limit. The initial value of the pressure sensor P1 is read, and the secondary value of the pressure sensor P1 is read after a preset time. It is determined whether the change in the pressure sensor P1 is less than the preset threshold. If it is, the cylinder is determined to be airtight, and the buffer chamber airtightness detection action is executed. If not, a warning signal is issued to indicate that the cylinder is airtight, the cylinder seal ring is replaced in time, and the operation is stopped.

[0022] Open solenoid valves V10, V9, V12, air pump B2, and air pump B1. After evacuation, read the initial value of pressure sensor P2 and read the secondary value of pressure sensor P2 after a preset time. Determine whether the change in pressure sensor P2 is less than a preset threshold. If so, the buffer chamber is considered to have good airtightness, and the air path cleaning action is performed. If not, a warning signal is issued, indicating poor airtightness of the buffer chamber. Check the airtightness of the buffer chamber in time, and close solenoid valves V10, V9, V12, air pump B2, and air pump B1 in sequence to stop operation.

[0023] The gas line cleaning process includes:

[0024] Open solenoid valves V6, V12, and V14. After purging for a preset time, close solenoid valve V6. Wait for the pressure in the buffer chamber to drop to normal pressure, then close solenoid valves V12 and V14 to complete the cleaning of the gas path, metering tube, and buffer chamber.

[0025] Furthermore, by controlling the stepper motor to drive the piston of the oil cylinder to move left and right, and in conjunction with solenoid valves V1 and V2, pressure sensor, limit sensor, and level sensor, the circulation and quantitative control of the oil sample are completed, including the following steps:

[0026] S11. Open solenoid valve V1 to control the stepper motor to pull the cylinder piston from the left limit to the right limit until the pressure sensor P1 is stable and unchanged, then close the stepper motor and solenoid valve V1.

[0027] S12. Open solenoid valve V2 to control the stepper motor to pull the cylinder piston from the right limit to the left limit until the pressure sensor P1 is stable and unchanged, then close the stepper motor and solenoid valve V2.

[0028] S13. Repeat steps S11 and S12 a preset number of times to complete the oil sample circulation and cleaning of the oil cylinder;

[0029] S14. Open solenoid valve V2 to control the stepper motor to push the cylinder piston from the right limit to the middle limit until the pressure sensor P1 is stable. Then close the stepper motor and solenoid valve V2 to complete the oil sample quantification process.

[0030] Furthermore, the stepper motor is controlled to pull the piston to the right limit, forming a gas-liquid two-phase system inside the cylinder. The dissolved gas in the oil is transferred from the liquid phase to the gas phase by the gas pump B1, accumulating at the top of the cylinder and in the buffer chamber. After degassing is complete, the piston position is adjusted by controlling the stepper motor to push the piston rod, transferring the accumulated sample gas in the cylinder to the buffer chamber and the metering tube in the six-way valve. This process includes the following steps:

[0031] S21. The heating control module heats the oil in the cylinder to a preset temperature and keeps it constant. At the same time, during the heating period, the cylinder pressure sensor P1 judges the pressure in the cylinder and the stepper motor pulls the piston to control the pressure within a predetermined range.

[0032] S22. Control the stepper motor to pull the piston to the right limit, forming a gas and liquid two-phase system inside the cylinder;

[0033] S23. The dissolved gas in the oil is transferred from the liquid phase to the gas phase by bubbling with air pump B1, and accumulates at the top of the oil cylinder and in the buffer chamber; solenoid valves V3, V4, and V13 are opened, air pump B1 is started, and after bubbling and circulating for a preset time, air pump B1, solenoid valves V13, V4, and V3 are closed, and the mixture is left to stand for a preset time to achieve dynamic equilibrium between the concentration of components in the extracted gas and the oil.

[0034] S24. After the bubbling degassing is completed, open solenoid valves V3 and V12, and control the stepper motor to push the piston rod to adjust the piston position, transferring the sample gas accumulated in the oil cylinder to the buffer chamber and the quantitative tube in the six-way valve until the buffer chamber level sensor L1 detects the level signal, and then close the stepper motor and solenoid valves V3 and V12.

[0035] S25. Open solenoid valves V12, V4, and V9, start air pump B1, and after a preset circulation time, close air pump B1, solenoid valves V12, V4, and V9 to fully mix the sample gas accumulated in the buffer chamber and the metering tube.

[0036] Furthermore, a multi-objective optimization algorithm is used to determine the heating parameters of the chromatographic analysis component at each heating stage, and the heating control module is controlled to heat the chromatographic analysis component according to the determined heating parameters so that the temperature of the chromatographic analysis component meets the detection requirements at different stages. This includes the following steps:

[0037] S31. Based on the separation logic of the chromatographic column, the heating process is divided into several key stages, the optimization parameters of each key stage are extracted, and the value range of the optimization parameters is defined.

[0038] The key stages include the initial heating stage, the initial isothermal stage, the gradient heating stage I, the intermediate isothermal stage, the gradient heating stage II, and the high-temperature isothermal stage.

[0039] S32. Construct a multi-objective optimization model based on the optimization parameters of each key stage, and use a non-dominated sorting genetic algorithm to optimize the parameters of the multi-objective optimization model to obtain several Pareto solution sets of parameters.

[0040] S33. Determine the weight of each optimization objective based on the objective priority of the actual application scenario, and calculate the comprehensive score of each Pareto solution based on the objective weight; determine the optimal heating parameters for each heating stage based on the comprehensive score of each Pareto solution.

[0041] S34. Based on the optimal heating parameters for each heating stage, the heating temperature of the corresponding chromatographic analysis component is adjusted by the heating control module to ensure that the temperature of the chromatographic analysis component meets the optimal detection requirements for different stages.

[0042] Furthermore, the expression for the objective function in the multi-objective optimization model is:

[0043]

[0044] The formula for calculating the overall score is:

[0045]

[0046] In the formula, F1 represents the separation degree, max() represents taking the maximum value, and min(R) represents the maximum value. ij F1 represents the minimum resolution of all component pairs, F2 represents the detection cycle, F3 represents the stationary phase loss, v1 represents the heating rate of the initial heating stage, v2 represents the heating rate of the gradient heating stage I, v3 represents the heating rate of the gradient heating stage II, T0 represents room temperature, T1 represents the isothermal temperature of the initial isothermal stage, t1 represents the duration of the initial isothermal stage, T2 represents the isothermal temperature of the intermediate isothermal stage, t2 represents the duration of the intermediate isothermal stage, T3 represents the isothermal temperature of the high-temperature isothermal stage, t3 represents the duration of the high-temperature isothermal stage, and S represents the overall score. These represent the weights of separation degree, detection cycle, and stationary phase loss, respectively. These represent the normalized separation degree, detection cycle, and stationary phase loss, respectively.

[0047] Furthermore, after degassing is complete, the six-way valve is switched to the injection state, allowing the degassed gas to enter the heated chromatographic analysis unit. The concentration of each component in the gas sample is then obtained through analysis using the chromatographic analysis unit, including the following steps:

[0048] S41. After the degassing process is completed, switch the six-way valve to the injection state so that the degassed gas enters the heated chromatographic analysis component and the concentration of each component in the gas sample is obtained by analysis through the chromatographic analysis component.

[0049] S42. Control the stepper motor to pull the piston to the right limit; open solenoid valves V10, V4, V3, air pump B2, and air pump B1, and after evacuation, close solenoid valves V3, V4, B1, V10, and B2 in sequence; open solenoid valve V3, control the stepper motor to push the piston to the left until the level sensor L1 in the buffer chamber detects the level signal, and close solenoid valve V3 and the stepper motor; open solenoid valve V2, control the stepper motor to push the piston to the left limit, and close solenoid valve V2 and the stepper motor.

[0050] The beneficial effects of this invention are as follows:

[0051] 1) This invention eliminates the need for an oil circulation pump, achieving oil sample circulation solely through an oil cylinder and stepper motor. Under negative pressure, the circulation pump bubbles the oil chamber, rapidly removing dissolved gases from the oil, shortening degassing time and improving degassing efficiency. The optimized degassing system structure reduces investment costs. This system can perform real-time online monitoring of oil-immersed electrical equipment, detecting latent faults through chromatographic analysis of dissolved gas content in the oil and preventing the escalation of equipment failures.

[0052] 2) This invention provides a gas sample verification interface, which performs periodic verification of the chromatographic analysis module through a periodic verification function, thereby improving the accuracy of the system's analysis results; it also provides a dedicated oil sample verification interface, which facilitates on-site verification of the system's performance indicators using reference oil samples.

[0053] 3) This invention does not require headspace degassing under extreme vacuum conditions. It accelerates oil-gas separation through bubbling, thereby achieving the highest degassing efficiency. Similar to conventional offline degassing methods, it does not need to consider the influence of vacuum degree and vacuum degassing rate on the analysis results. It has the advantages of simple structure and good repeatability.

[0054] 4) This invention calculates the volume of the degassing gas by using the volume and pressure of the buffer chamber. Combined with the gas component concentration given by the chromatographic analysis module, the concentration of dissolved gas in the oil can be calculated by using the partition theorem (Oswald coefficient) and referring to relevant formulas. It does not need to consider the influence of degassing pressure and degassing rate on the gas analysis results.

[0055] 5) This invention improves the reliability of the system by vacuuming the return oil to prevent carrier gas from entering the main transformer and causing the gas relay to activate.

[0056] 6) This invention eliminates the interference of residual gas on the detection results by purging the gas path system with carrier gas and evacuating it, thereby improving the accuracy and rapid detection capability of the system.

[0057] 7) This invention utilizes a multi-objective optimization algorithm to determine chromatographic column heating parameters, achieving synergistic optimization of multi-dimensional technical effects. This not only ensures sufficient separation of each characteristic gas component, meeting the accuracy requirements of detection, but also effectively shortens the detection cycle, adapts to the real-time requirements of online monitoring, and reduces stationary phase loss, extending equipment lifespan. Simultaneously, it can generate optimized schemes suitable for different application scenarios, and combined with precise temperature control, it can stably control column temperature fluctuations, balancing the stability of the detection process with the long-term reliability of the equipment. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 This is a schematic diagram of an online monitoring system for dissolved gases in oil according to an embodiment of the present invention;

[0060] Figure 2 This is a schematic diagram illustrating the principle of heating and temperature control in an online monitoring system for dissolved gases in oil according to an embodiment of the present invention.

[0061] Figure 3 This is a flowchart of heating and temperature control in an online monitoring system for dissolved gases in oil according to an embodiment of the present invention.

[0062] In the picture:

[0063] 1. Transformer; 2. Hydraulic cylinder; 3. Stepper motor; 4. Buffer chamber; 5. Standard gas cylinder; 6. Carrier gas generator; 7. Pressure regulating valve; 8. Gas detector; 9. Chromatographic column; 10. Six-way valve; 11. Heating control module. Detailed Implementation

[0064] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0065] According to embodiments of the present invention, an online monitoring system for dissolved gases in oil and a method for oil-gas separation by headspace elution and diversion concentration are provided.

[0066] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figures 1-3 As shown, according to an embodiment of the present invention, an online monitoring system for dissolved gases in oil is provided, including an oil cylinder 2, a stepper motor 3, a buffer chamber 4, a chromatographic analysis module, a standard gas cylinder 5, and a heating control module 11; wherein, the oil cylinder 2 and the stepper motor 3 are horizontally arranged, and the lead screw of the stepper motor 3 is connected to the piston inside the oil cylinder 2; the heating control module 11 is provided on the outside of both the oil cylinder 2 and the chromatographic analysis module, and the heating control module 11 can precisely control the heating by controlling the heating plate, temperature sensor, and temperature switch through a control board. Heating and maintaining a constant temperature; the bottom side of cylinder 2 is connected in sequence to solenoid valve V1, three-way plug valve V15, and the oil port of transformer 1 via an oil inlet pipe; the bottom side of cylinder 2 is also connected in sequence to solenoid valve V2, three-way plug valve V16, and the oil port of transformer 1 via a return oil pipe; the other bottom side of cylinder 2 is connected in sequence to solenoid valve V13, air pump B1, solenoid valve V4, and the top side of buffer chamber 4 via a pipe; the top of cylinder 2 is connected in sequence to solenoid valve V3 and the bottom of buffer chamber 4 via a pipe; the top of buffer chamber 4 is connected to... The buffer chamber 4 is connected in sequence to interface I of solenoid valve V12 and six-way valve 10 via pipelines. The top of the buffer chamber 4 is also connected to solenoid valve V14 via pipelines. Interface II of six-way valve 10 is connected in sequence to solenoid valves V6, V5, and V9 via pipelines. The other end of solenoid valve V6 is connected to the chromatographic analysis module. The other end of solenoid valve V5 is connected to standard gas cylinder 5. The other end of solenoid valve V9 is connected to solenoid valves V10, V13, and gas pump B1. The other end of solenoid valve V10 is connected to gas pump B1. 2. Connected in phase; Specifically, the standard gas cylinder 5 is equipped with a gas pressure reducing valve and a pressure transmitter, which can collect the remaining gas pressure in the standard gas cylinder in real time through the control board to prevent the gas from running out and send early warning information; The top of the oil cylinder 1 is equipped with a left limit sensor, a middle limit sensor and a right limit sensor in sequence; Pressure sensor P1 and temperature sensor T1 are installed on the oil inlet pipe and the oil return pipe, Pressure sensor P2 and liquid level sensor L1 are installed on one side of the bottom of the buffer chamber 4, and Pressure sensor P3 is connected to the pressure regulating valve 7.

[0067] like Figure 2 As shown, the heating control module includes control elements, solid-state relays (SSRs), temperature switches, heating plates, temperature sensors (PT100), temperature data acquisition and amplification, and A / D conversion circuits.

[0068] Specifically, the PT100 temperature sensor was selected. Its resistance-temperature relationship conforms to the international standard IEC751. Manufactured using platinum wire winding or thin-film sputtering processes, it features high precision, good stability, and a wide temperature range (-200℃ to 850℃). A solid-state relay was chosen as the heating isolation control device. A solid-state relay is an electronic switching device without mechanical contacts, perfectly isolating the low-voltage control signal from the high-voltage controlled circuit. It has advantages such as fast response, long lifespan, and strong anti-interference capabilities, overcoming the potential shortcomings of traditional relays.

[0069] The heating control module employs a microcontroller to directly control the output of a solid-state relay, efficiently driving the heating plate with current. The system utilizes a composite control algorithm (Fuzzy-PID control). Fuzzy-PID control monitors system performance in real time and dynamically adjusts PID parameters based on fuzzy logic, achieving faster system response and smaller overshoot. Fuzzy-PID control does not require a precise model of the controlled object, making it suitable for controlling uncertain and nonlinear objects. It selects an intelligent controller based on the deviation between the given and measured values, and chooses the appropriate control method based on changes in the deviation. The microcontroller receives real-time data from a temperature sensor (PT100), compares it with the set target temperature, and selects the appropriate control method based on changes in the deviation. The algorithm ultimately controls the signal at the input of the solid-state relay, thereby precisely controlling the current output at the relay's output.

[0070] like Figure 3 The heating and temperature control process of the online monitoring system for dissolved gases in oil is shown below.

[0071] When the system starts heating, it performs initialization. After initialization, it enters parameter setting. If no parameters need to be set, it directly reads the default parameters stored in the EEPROM. Then, it starts the heating and temperature control program. The measured temperature value is displayed in the interrupt service routine. Since the entire program runs relatively fast, continuous temperature display would be indistinguishable to the human eye. Therefore, a timer interrupt with a duration of 1 second is defined to display the temperature value every 1 second. After acquiring the temperature, the host computer communication program is called to transmit the measured temperature value to the host computer. The host computer software plots the temperature curve and saves the data. Then, the temperature control subroutine is called to continuously adjust the output signal through a composite control algorithm. The heating plate is controlled by a solid-state relay to achieve the temperature control purpose. Finally, it determines whether to end the temperature control. If yes, the heating and temperature control process ends; otherwise, it returns to the temperature measurement program, and this cycle continues.

[0072] The system in this embodiment provides heating and temperature control, which provides heating and temperature control functions for the chromatographic analysis module and the oil cylinder. Through the temperature compensation mechanism, the stability of the oil-gas balance is ensured, the temperature of the chromatographic analysis module is maintained, and the accuracy and stability of the analysis results are ensured.

[0073] In one embodiment, the chromatographic analysis module includes a carrier gas generator 6, a pressure regulating valve 7, a gas detector 8, a chromatographic column 9, a six-way valve 10, a solenoid valve V8, and a solenoid valve V11. One side of the carrier gas generator 6 is connected sequentially to the interface V of the pressure regulating valve 7, the solenoid valve V8, the gas detector 8, the chromatographic column 9, and the six-way valve 10 via pipelines. The interface IV of the six-way valve 10 is connected to the solenoid valve V11, the pressure regulating valve 7, and the solenoid valve V6 via pipelines. The gas detector 8 and the chromatographic column 9 together constitute the chromatographic analysis component, and a heating control module 11 is provided on the outside of the chromatographic analysis component. This module can precisely control the heating of the module and maintain a constant temperature of 60°C by controlling the heating plate, temperature sensor, and temperature switch via a control board.

[0074] In practical applications, the chromatography analysis module can also have a column backflush function. In the backflush state, the gas inlet of V8 is connected to the pressure regulator 7 via a gas line, and the outlet of V8 is connected to the outlet of the gas detector. The gas is discharged after passing through the column, six-way valve interface V, quantitative tube, six-way valve interface IV, and three-way valve V11.

[0075] In one embodiment, when in the injection state, the pressure regulating valve 7 is connected via pipeline to port IV, port III, the metering tube in the six-way valve 10, port VI, port V, the chromatographic column 9, and the gas detector 8. The buffer chamber 4 is connected via pipeline to port I and port II of the six-way valve 10. When in the degassing state, the pressure regulating valve 7 is connected via pipeline to port IV, port V, the chromatographic column 9, and the gas detector 8. The buffer chamber 4 is connected via pipeline to port I, port VI, the metering tube in the six-way valve 10, port III, and port II of the six-way valve 10.

[0076] In practical applications, stepper motor 3, gas detector 8, six-way valve 10, valves V1-V14, air pumps B1 / B2, pressure sensors P1-P3, liquid level sensor L1, temperature sensor T1, as well as oil cylinder, chromatographic analysis module, and heating control module 11 are all connected to the control board via wiring. The control board controls the on / off state of valves, pumps, and stepper motors, as well as the high-precision constant temperature control of oil cylinder and chromatographic analysis module heating.

[0077] The principle of oil-gas separation in this embodiment is as follows: by adjusting the gas-liquid two-phase volume ratio, oil-gas separation is achieved by bubbling with an air pump under negative pressure conditions; before bubbling circulation, it is also necessary to ensure that the space above the oil surface is gas in order to achieve the bubbling effect; negative pressure is not a necessary condition. It is mainly achieved by adjusting the gas-liquid two-phase volume ratio to increase the contact area between the gas and liquid phases, and by accelerating the oil-gas separation process by bubbling and eluting with an air pump. Increasing the gas-liquid two-phase volume ratio will inevitably generate negative pressure, but negative pressure is not a necessary condition for oil-gas separation.

[0078] The system in this embodiment provides an oil sample verification interface to meet the needs of regular on-site oil sample verification; it also provides a gas verification interface to enable gas verification; and it has a column backflush function, which can be used to backflush the column with carrier gas, effectively extending the service life of the column. The backflush function can be set to purge at a fixed period or to automatically perform backflush based on changes in the resolution or retention time of the chromatographic peak.

[0079] According to another embodiment of the present invention, an oil-gas separation method using headspace elution splitting concentration in an online oil dissolved gas monitoring system is provided, comprising the following steps:

[0080] S1. By controlling the stepper motor to drive the piston of the oil cylinder to move left and right, and in conjunction with solenoid valve V1, solenoid valve V2, pressure sensor, limit sensor and liquid level sensor, the circulation and quantitative control of oil sample are completed.

[0081] Specifically, before step S1, there are also processes for initialization, airtightness check and air circuit cleaning;

[0082] The initialization process includes:

[0083] Initialize the six-way valve to the degassing state, initialize and close all valves and pumps, and start the aging process of the chromatography analysis module;

[0084] The airtightness inspection process includes:

[0085] Hydraulic cylinder reset: Determine the piston position. If it is at the left limit, perform a hydraulic cylinder airtightness test; if it is not at the left limit, open solenoid valve V2 and perform a hydraulic cylinder reset.

[0086] Hydraulic cylinder air tightness check: Control the stepper motor to pull the hydraulic cylinder piston from the left limit to the right limit, read the initial value of the pressure sensor P1, and read the secondary value of the pressure sensor P1 after a preset time. Determine whether the change in pressure sensor P1 is less than the preset threshold. If so, the hydraulic cylinder air tightness is good, and the buffer chamber air tightness test is performed. If not, a warning signal is issued to indicate poor hydraulic cylinder air tightness, the hydraulic cylinder seal ring is replaced in time, and the operation is stopped.

[0087] Buffer chamber airtightness check: Open solenoid valves V10, V9, V12, air pump B2, and air pump B1. After evacuation, read the initial value of pressure sensor P2 and read the secondary value of pressure sensor P2 after a preset time. Determine whether the change in pressure sensor P2 is less than the preset threshold. If so, the buffer chamber is considered to be airtight, and the air circuit cleaning action is performed. If not, a warning signal is issued, indicating that the buffer chamber is not airtight. Check the airtightness of the buffer chamber in time, and close solenoid valves V10, V9, V12, air pump B2, and air pump B1 in sequence to stop operation.

[0088] The gas line cleaning process includes:

[0089] Open solenoid valves V6, V12, and V14. After purging for a preset time, close solenoid valve V6. Wait for the pressure in the buffer chamber to drop to normal pressure, then close solenoid valves V12 and V14 to complete the cleaning of the gas path, metering tube, and buffer chamber.

[0090] The process of controlling the stepper motor to drive the piston of the oil cylinder to move left and right, and cooperating with solenoid valves V1 and V2, pressure sensor, limit sensor and liquid level sensor to complete the circulation and quantitative control of oil sample includes the following steps:

[0091] S11, Oil Inlet: Open solenoid valve V1 to control stepper motor to pull oil cylinder piston from left limit to right limit until pressure sensor P1 stabilizes and remains unchanged, then close stepper motor and solenoid valve V1;

[0092] S12, Oil return: Open solenoid valve V2 to control the stepper motor to pull the cylinder piston from the right limit to the left limit until the pressure sensor P1 is stable and unchanged, then close the stepper motor and solenoid valve V2.

[0093] S13. Repeat steps S11 and S12 a preset number of times to complete the oil sample circulation and cleaning of the oil cylinder;

[0094] S14. Oil sample quantitative measurement: Open solenoid valve V2 to control the stepper motor to push the cylinder piston from the right limit to the middle limit until the pressure sensor P1 is stable. Then close the stepper motor and solenoid valve V2 to complete the oil sample quantitative measurement process.

[0095] S2. Control the stepper motor to pull the piston to the right limit, forming a gas and liquid two-phase system inside the oil cylinder; the gas dissolved in the oil is transferred from the liquid phase to the gas phase by the air pump B1, and accumulates at the top of the oil cylinder and in the buffer chamber; after the bubbling degassing is completed, the piston position is adjusted by controlling the stepper motor to push the piston rod, and the sample gas accumulated in the oil cylinder is transferred to the buffer chamber and the metering tube in the six-way valve.

[0096] The process involves controlling a stepper motor to pull the piston to the right limit position, forming a gas-liquid two-phase system inside the oil cylinder. The dissolved gas in the oil is transferred from the liquid phase to the gas phase via bubbling by the gas pump B1, accumulating at the top of the oil cylinder and in the buffer chamber. After bubbling degassing is completed, the piston position is adjusted by controlling the stepper motor to push the piston rod, transferring the accumulated sample gas in the oil cylinder to the buffer chamber and the metering tube in the six-way valve. This process includes the following steps:

[0097] S21. Oil sample heating: The oil in the oil cylinder is heated to a preset temperature (50°C in this embodiment) and kept constant by the heating control module. At the same time, the pressure in the oil cylinder is judged by the oil cylinder pressure sensor P1 during heating, and the piston is pulled by the stepper motor to control the pressure within a predetermined range.

[0098] S22. Adjust the gas-liquid ratio: Control the stepper motor to pull the piston to the right limit, forming a gas and liquid two-phase system inside the cylinder;

[0099] S23, Dynamic Bubbling Degassing: The dissolved gas in the oil is transferred from the liquid phase to the gas phase by bubbling through the air pump B1, and accumulates at the top of the oil cylinder and in the buffer chamber; the solenoid valves V3, V4, and V13 are opened, the air pump B1 is started, and after the bubbling cycle is completed for a preset time, the air pump B1, solenoid valves V13, V4, and V3 are closed, and the mixture is left to stand for a preset time, so that the concentration of the components in the extracted gas and the oil are dynamically balanced;

[0100] S24. Sample gas quantification: After the bubbling degassing is completed, open solenoid valves V3 and V12, and control the stepper motor to push the piston rod to adjust the piston position, transferring the sample gas accumulated in the oil cylinder to the buffer chamber and the quantitative tube in the six-way valve until the buffer chamber level sensor L1 detects the level signal, and then close the stepper motor and solenoid valves V3 and V12.

[0101] S25. Quantitative tube circulation: Open solenoid valves V12, V4, and V9, start air pump B1, and after the preset circulation time, close air pump B1, solenoid valves V12, V4, and V9 to fully mix the sample gas accumulated in the buffer chamber and quantitative tube.

[0102] S3. Use a multi-objective optimization algorithm to determine the heating parameters of the chromatographic analysis component at each heating stage, and control the heating control module to heat the chromatographic analysis component according to the determined heating parameters so that the temperature of the chromatographic analysis component meets the detection requirements at different stages.

[0103] The process of determining the heating parameters of the chromatographic analysis component at each heating stage using a multi-objective optimization algorithm, and controlling the heating control module to heat the chromatographic analysis component according to the determined heating parameters so that the temperature of the chromatographic analysis component meets the detection requirements at different stages, includes the following steps:

[0104] S31. Based on the separation logic of the chromatographic column (elution according to the gas boiling point gradient), the heating process is divided into several key stages, the optimization parameters of each key stage are extracted, and the value range of the optimization parameters is defined.

[0105] The key stages include the initial heating stage, the initial isothermal stage, the gradient heating stage I, the intermediate isothermal stage, the gradient heating stage II, and the high-temperature isothermal stage.

[0106] In this embodiment, the heating rate during the initial heating stage is 5-25℃ / min (affecting the temperature stability of low-boiling-point components before elution).

[0107] The initial isothermal stage is maintained at a temperature of 40-60℃ for 1-5 minutes (for the separation of low-boiling-point components such as H2 and O2).

[0108] The heating rate in the gradient heating stage I is 5-20℃ / min (affecting the elution rhythm of the medium-boiling-point components).

[0109] The isothermal stage is maintained at a temperature of 100-120℃ for 1-5 minutes (used for the separation of medium-boiling-point components such as CO and CH4).

[0110] The heating rate in the gradient heating stage II is 5-15℃ / min (affecting the desorption efficiency of high-boiling-point components).

[0111] The constant temperature during the high-temperature isothermal stage is 150-180℃, and the duration is 1-5min (used for the separation of high-boiling-point components such as C2H2 and C2H4).

[0112] Before step S31, the following steps are required: clarifying the core detection requirements and hardware constraints for column heating. This step is a prerequisite for subsequent optimization and requires quantifying the core target of dissolved gas detection in oil, while defining insurmountable limitations based on the actual capabilities of the equipment. Regarding detection requirements, it is necessary to ensure that the resolution of key component pairs such as H2 and O2, CH4 and CO, and C2H2 and C2H4 is ≥1.5 (meeting industry separation standards), the single analysis cycle (including heating, isothermal, and cooling) is ≤45 minutes (meeting real-time online monitoring requirements), and the cumulative duration of column temperature ≥150℃ is ≤5 minutes / cycle (to avoid rapid aging of the stationary phase and extend the column life to more than 2 years). Regarding hardware constraints, it is necessary to specify that the maximum heating rate of the heating module is ≤25℃ / min, the column oven temperature control accuracy is ±0.1℃, the longest isothermal duration in the high-temperature section (≥150℃) is ≤10 minutes, and the initial isothermal temperature range is 40-60℃ (suitable for separating low-boiling-point components). This step helps to anchor the optimization direction and avoid subsequent algorithms generating invalid parameters that exceed the equipment's capabilities or do not meet the detection requirements.

[0113] S32. Construct a multi-objective optimization model based on the optimization parameters of each key stage, and use a non-dominated sorting genetic algorithm to optimize the parameters of the multi-objective optimization model to obtain several Pareto solution sets of parameters.

[0114] Specifically, based on the multi-objective, multi-variable, and nonlinear characteristics of the problem, an adaptive algorithm (such as NSGA-II) is selected, and a Pareto optimal solution set that takes into account all objectives is generated through iterative calculation.

[0115] Algorithm selection and parameter settings: NSGA-II (non-dominated sorting genetic algorithm) is adopted because it can efficiently handle multi-objective conflict problems. Specific parameters are: population size 80 (to balance diversity and computational cost), number of iterations 100 generations (to verify convergence through pre-experiments), crossover probability 0.85 (to promote the diversity of parameter combinations), and mutation probability 0.02 (to avoid local optima).

[0116] Optimize execution process:

[0117] Initialize the population: Randomly generate 80 sets of parameter combinations that satisfy the constraints (e.g., v1=10, T1=50, t1=3...).

[0118] Fitness calculation: Simulate the separation effect of each set of parameters using chromatographic simulation software (such as ChemStation) and output F1, F2, and F3 values;

[0119] Non-dominated sorting: The population is divided into multiple levels, with the first level being the Pareto optimal solution (no other solution is better than the other in all objectives).

[0120] Iterative optimization: The next generation of population is generated through selection, crossover, and mutation. The fitness calculation and non-dominated sorting steps are repeated for up to 100 generations to finally obtain the Pareto solution set (containing 10-15 sets of high-quality parameters).

[0121] S33. Determine the weight of each optimization objective based on the objective priority of the actual application scenario, and calculate the comprehensive score of each Pareto solution based on the objective weight; determine the optimal heating parameters for each heating stage based on the comprehensive score of each Pareto solution.

[0122] In this embodiment, when the actual application scenario is online monitoring of substations (which needs to balance accuracy and real-time performance), The values ​​are 0.5, 0.3, and 0.2 respectively; when the actual application scenario is high-precision analysis in the laboratory (precision priority), The values ​​are 0.7, 0.2, and 0.0.

[0123] S34. Based on the optimal heating parameters for each heating stage, the heating temperature of the corresponding chromatographic analysis component is adjusted by the heating control module to ensure that the temperature of the chromatographic analysis component meets the optimal detection requirements for different stages.

[0124] Specifically, the expression for the objective function in the multi-objective optimization model is:

[0125]

[0126] The formula for calculating the overall score is:

[0127]

[0128] In the formula, F1 represents the separation degree, max() represents taking the maximum value, and min(R) represents the maximum value. ij F1 represents the minimum resolution of all component pairs, F2 represents the detection cycle, F3 represents the stationary phase loss (only the duration of the high-temperature section affects the stationary phase loss), v1 represents the heating rate of the initial heating stage, v2 represents the heating rate of the gradient heating stage I, v3 represents the heating rate of the gradient heating stage II, T0 represents room temperature, T1 represents the isothermal temperature of the initial isothermal stage, t1 represents the duration of the initial isothermal stage, T2 represents the isothermal temperature of the intermediate isothermal stage, t2 represents the duration of the intermediate isothermal stage, T3 represents the isothermal temperature of the high-temperature isothermal stage, t3 represents the duration of the high-temperature isothermal stage, and S represents the overall score. These represent the weights of separation degree, detection cycle, and stationary phase loss, respectively. These represent the normalized separation degree, detection cycle, and stationary phase loss, respectively.

[0129] S4. After degassing is completed, switch the six-way valve to the injection state so that the degassed gas enters the heated chromatographic analysis unit and the concentration of each component in the gas sample is obtained by analysis of the chromatographic analysis unit.

[0130] After degassing is completed, the six-way valve is switched to the injection state, allowing the degassed gas to enter the heated chromatographic analysis component. The concentration of each component in the gas sample is then obtained through analysis using the chromatographic analysis component, including the following steps:

[0131] S41. Sample Injection and Detection: After the degassing process is completed, switch the six-way valve to the sample injection state, so that the degassing gas enters the chromatographic analysis component under the drive of the carrier gas. The concentration of each component in the gas sample is obtained through chromatographic analysis. The volume of the degassing gas and the concentration of the component gas analyzed by the chromatographic analysis module, as well as the gas solubility distribution coefficient between the gas and liquid at the current temperature and pressure, are calculated according to the ideal gas equation. The concentration of dissolved gas in the oil is calculated by the gas distribution law in GB / T17623-2017 and the material balance calculation formula.

[0132] S42. Oil discharge process: Control the stepper motor to pull the piston to the right limit; open solenoid valves V10, V4, V3, air pump B2, and air pump B1, and after vacuuming, close solenoid valves V3, V4, B1, V10, and B2 in sequence; open solenoid valve V3, control the stepper motor to push the piston to the left until the level sensor L1 in the buffer chamber detects the level signal, and close solenoid valve V3 and the stepper motor; open solenoid valve V2, control the stepper motor to push the piston to the left limit, and close solenoid valve V2 and the stepper motor.

[0133] The headspace elution split concentration oil-gas separation method in this embodiment can complete headspace degassing without extreme vacuum conditions. It accelerates oil-gas separation by bubbling, thereby achieving the highest degassing efficiency. Similar to conventional offline degassing methods, it does not need to consider the influence of vacuum degree and vacuum degassing rate on the analysis results. It has the advantages of simple structure and good repeatability.

[0134] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An online monitoring system for dissolved gas in oil, characterized in that, The oil cylinder, the stepping motor, the buffer chamber, the chromatographic analysis module, the standard gas steel bottle and the heating control module are included. The oil cylinder and the stepping motor are horizontally arranged, and the screw rod of the stepping motor is connected with the piston inside the oil cylinder. The bottom side of the oil cylinder is connected with the oil port of the electromagnetic valve V1, the three-way stopcock valve V15 and the transformer through the oil inlet pipeline in sequence. The bottom side of the oil cylinder is also connected with the oil port of the electromagnetic valve V2, the three-way stopcock valve V16 and the transformer through the oil return pipeline in sequence. The other side of the bottom of the oil cylinder is connected with the electromagnetic valve V13, the air pump B1, the electromagnetic valve V4 and the top side of the buffer chamber through the pipeline in sequence. The top of the buffer chamber is connected with the electromagnetic valve V12 and the interface I of the six-way valve through the pipeline in sequence. The interface II of the six-way valve is connected with the electromagnetic valve V6, the electromagnetic valve V5 and the electromagnetic valve V9 through the pipeline in sequence. The other end of the electromagnetic valve V6 is connected with the chromatographic analysis module, the other end of the electromagnetic valve V5 is connected with the standard gas steel bottle, and the other end of the electromagnetic valve V9 is connected with the electromagnetic valve V10, the electromagnetic valve V13 and the air pump B1 respectively.

2. The on-line oil dissolved gas monitoring system of claim 1, wherein, The top of the oil cylinder is sequentially provided with the left limit sensor, the middle limit sensor and the right limit sensor. The oil inlet pipeline and the oil return pipeline are provided with the pressure sensor P1 and the temperature sensor T1, the bottom side of the buffer chamber is provided with the pressure sensor P2 and the liquid level sensor L1, and the pressure stabilizing valve is connected with the pressure sensor P3. The chromatographic analysis module includes the carrier gas generator, the pressure stabilizing valve, the gas detector, the chromatographic column, the six-way valve, the electromagnetic valve V8 and the battery valve V11.

3. An online oil dissolved gas monitoring system according to claim 2, wherein, The side of the carrier gas generator is connected with the pressure stabilizing valve, the electromagnetic valve V8, the gas detector, the chromatographic column and the interface V of the six-way valve through the pipeline in sequence. The gas detector and the chromatographic column jointly constitute the chromatographic analysis component, and the outer side of the chromatographic analysis component is provided with the heating control module.

4. A headspace elution split and concentrated oil gas separation method for an online monitoring system of a gas dissolved in oil, implemented based on the online monitoring system of a gas dissolved in oil according to claim 3, characterized in that, When in the sampling state, the pressure stabilizing valve is connected with the interface IV of the six-way valve, the interface III of the six-way valve, the dosing tube in the six-way valve, the interface VI of the six-way valve, the interface V of the six-way valve, the chromatographic column and the gas detector through the pipeline, and the buffer chamber is connected with the interface I of the six-way valve and the interface II of the six-way valve through the pipeline. When in the degassing state, the pressure stabilizing valve is connected with the interface IV of the six-way valve, the interface V of the six-way valve, the chromatographic column and the gas detector through the pipeline, and the buffer chamber is connected with the interface I of the six-way valve, the interface VI of the six-way valve, the dosing tube in the six-way valve, the interface III of the six-way valve and the interface II of the six-way valve through the pipeline. The method includes the following steps: S1, through the control step motor drives the oil cylinder piston left and right movement, and cooperate with electromagnetic valve V1, electromagnetic valve V2, pressure sensor, limit sensor and liquid level sensor, complete oil sample circulation and quantitative control; S2, control step motor pull piston right to right limit, form gas, liquid two phase in the oil cylinder;Through the air pump B1 bubble, the dissolved gas in oil is transferred from the liquid phase to the gas phase, and accumulated in the top of the oil cylinder and the buffer chamber;After the completion of the bubble degassing, through the control step motor push rod adjustment piston position, the accumulated sample gas in the oil cylinder is transferred to the buffer chamber and the six-way valve in the quantitative pipe; S3, using multi-objective optimization algorithm to determine the heating parameters of the chromatographic analysis component in each heating stage, and controlling the heating control module to heat the chromatographic analysis component according to the determined heating parameters, so that the temperature of the chromatographic analysis component meets the detection requirements of different stages; S4, after degassing, switch the six-way valve to the sampling state, so that the outgassed gas enters the heated chromatographic analysis component, and the concentration of each component in the gas sample is obtained by chromatographic analysis.

5. The headspace purge split condenser oil gas separation method of an online oil- dissolved gas monitoring system according to claim 4, characterized in that, Before step S1, there are also initialization, air tightness check and air path cleaning process; The initialization process includes: Initialize the six-way valve to the degassing state, initialize to close all valves and pumps, and start the chromatographic analysis module aging; The air tightness check process includes: Determine the position of the piston, if it is in the left limit, execute the oil cylinder air tightness detection action;If not in the left limit, open electromagnetic valve V2, execute the oil cylinder reset action; Control step motor pull oil cylinder piston from left limit to right limit, read the initial value of current pressure sensor P1, and read the second value of pressure sensor P1 after a predetermined time, judge whether the change of pressure sensor P1 is less than the preset threshold, if yes, determine that the oil cylinder air tightness is good, then execute the buffer chamber air tightness detection action;If not, send a warning signal, prompt the oil cylinder air tightness is poor, replace the oil cylinder seal ring in time, and stop working; Open electromagnetic valve V10, electromagnetic valve V9, electromagnetic valve V12, air pump B2, air pump B1, read the initial value of current pressure sensor P2 after vacuumizing, and read the second value of pressure sensor P2 after a predetermined time, judge whether the change of pressure sensor P2 is less than the preset threshold, if yes, determine that the buffer chamber air tightness is good, then execute the air path cleaning action, if not, send a warning signal, prompt the buffer chamber air tightness is poor, check the buffer chamber air tightness in time, and close electromagnetic valve V10, electromagnetic valve V9, electromagnetic valve V12, air pump B2 and air pump B1 in turn, stop working; The air path cleaning process includes: Open electromagnetic valve V6, electromagnetic valve V12, electromagnetic valve V14, purge for a predetermined time, close electromagnetic valve V6, wait for the buffer chamber pressure to drop to normal pressure, close electromagnetic valve V12 and electromagnetic valve V14, complete the cleaning of the air path, quantitative pipe and buffer chamber.

6. The headspace purge split condenser oil gas separation method of an online oil- dissolved gas monitoring system according to claim 4, wherein, The oil sample circulation and quantitative control by controlling the step motor to drive the oil cylinder piston left and right movement, and cooperating with electromagnetic valve V1, electromagnetic valve V2, pressure sensor, limit sensor and liquid level sensor includes the following steps: S11, open electromagnetic valve V1, control the stepper motor to pull the oil cylinder piston from the left limit to the right limit, until the pressure sensor P1 is stable, close the stepper motor and electromagnetic valve V1; S12, open electromagnetic valve V2, control the stepper motor to pull the oil cylinder piston from the right limit to the left limit, until the pressure sensor P1 is stable, close the stepper motor and electromagnetic valve V2; S13, repeat steps S11 and S12 for a predetermined number of times, complete the oil sample circulation and oil cylinder cleaning; S14, open electromagnetic valve V2, control the stepper motor to push the oil cylinder piston from the right limit to the middle limit, until the pressure sensor P1 is stable, close the stepper motor and electromagnetic valve V2, complete the oil sample quantitative process.

7. The headspace purge split condenser oil gas separation method of an online oil- dissolved gas monitoring system according to claim 4, characterized in that, The control step motor pulls the piston to the right limit, and the gas-liquid two-phase is formed in the oil cylinder; the dissolved gas in the oil is transferred from the liquid phase to the gas phase by bubbling through the air pump B1, and is accumulated in the top of the oil cylinder and the buffer chamber; after the bubbling degassing is completed, the accumulated sample gas in the oil cylinder is transferred to the buffer chamber and the quantitative pipe in the six-way valve by adjusting the position of the piston through the control step motor. S21, use the heating control module to heat the oil in the oil cylinder to a predetermined temperature and keep it constant, and judge the pressure in the oil cylinder through the oil cylinder pressure sensor P1 during heating, and control the pressure in the predetermined range by pulling the piston through the step motor; S22, control the step motor to pull the piston to the right limit, and form gas-liquid two-phase in the oil cylinder; S23, the dissolved gas in the oil is transferred from the liquid phase to the gas phase by bubbling through the air pump B1, and is accumulated in the top of the oil cylinder and the buffer chamber; open electromagnetic valve V3, electromagnetic valve V4, electromagnetic valve V13, start air pump B1, after bubbling cycle for a predetermined time, close air pump B1, electromagnetic valve V13, electromagnetic valve V4, electromagnetic valve V3, stand for a predetermined time, so that the concentration of outgassed gas and oil components is dynamically balanced; S24, after the bubbling degassing is completed, open electromagnetic valve V3, electromagnetic valve V12, adjust the position of the piston by controlling the step motor to push the piston rod, transfer the accumulated sample gas in the oil cylinder to the buffer chamber and the quantitative pipe in the six-way valve, until the liquid level sensor L1 detects the liquid level signal, close the step motor and electromagnetic valve V3, electromagnetic valve V12; S25, open electromagnetic valve V12, electromagnetic valve V4, electromagnetic valve V9, start air pump B1, after a predetermined time, close air pump B1, electromagnetic valve V12, electromagnetic valve V4, electromagnetic valve V9, mix the accumulated sample gas in the buffer chamber and the quantitative pipe.

8. The headspace purge split condenser oil gas separation method of an online oil- dissolved gas monitoring system according to claim 4, wherein, The heating parameters of the chromatographic analysis component in each heating stage are determined by using a multi-objective optimization algorithm, and the heating control module is controlled according to the determined heating parameters to heat the chromatographic analysis component, so that the temperature of the chromatographic analysis component meets the detection requirements of different stages, which includes the following steps: S31, based on the separation logic of the chromatographic column, divide the heating process into several key stages, extract the optimization parameters of each key stage, and determine the value range of the optimization parameters; The key stages include an initial temperature rising stage, an initial constant temperature stage, a gradient temperature rising I stage, an intermediate constant temperature stage, a gradient temperature rising II stage, and a high temperature constant temperature stage. S32, constructing a multi-objective optimization model according to the optimization parameters of each key stage, and performing parameter optimization on the multi-objective optimization model by using a non-dominated sorting genetic algorithm to obtain a Pareto solution set of a plurality of groups of parameters; S33, determining the weights of each optimization target according to the target priority of the actual application scenario, and calculating a comprehensive score of each Pareto solution in combination with the target weights; and determining the optimal heating parameters of each heating stage based on the comprehensive score of each Pareto solution; S34, based on the optimal heating parameters of each heating stage, the heating control module is combined to regulate and control the heating temperature of the corresponding stage chromatographic analysis component, so that the temperature of the chromatographic analysis component meets the optimal detection requirements of different stages.

9. The headspace purge split condenser oil gas separation method of an online oil- dissolved gas monitoring system according to claim 8, wherein, The expression of the objective function in the multi-objective optimization model is: ； The calculation formula of the comprehensive score is: ； wherein F1 represents the resolution, max() represents the maximum value, min(R ij ) represents the minimum resolution of all component pairs, F2 represents the detection period, F3 represents the stationary phase loss, v1 represents the ramp rate of the initial temperature ramping phase, v2 represents the ramp rate of the gradient temperature I phase, v3 represents the ramp rate of the gradient temperature II phase, T0 represents the room temperature, T1 represents the isothermal temperature of the initial isothermal phase, t1 represents the time length of the initial isothermal phase, T2 represents the isothermal temperature of the intermediate isothermal phase, t2 represents the time length of the intermediate isothermal phase, T3 represents the isothermal temperature of the high temperature isothermal phase, t3 represents the time length of the high temperature isothermal phase, S represents the comprehensive score, respectively represent the resolution, the detection period and the stationary phase loss, respectively represent the normalized resolution, the detection period and the stationary phase loss.

10. The headspace purge split condenser oil gas separation method of an online oil- dissolved gas monitoring system of claim 4, wherein, After the degassing is completed, the six-way valve is switched to the sampling state, so that the outgassed gas enters the heated chromatographic analysis component, and the concentration of each component in the gas sample is obtained by analyzing the chromatographic analysis component. S41, after the degassing process is completed, the six-way valve is switched to the sampling state, so that the outgassed gas enters the heated chromatographic analysis component, and the concentration of each component in the gas sample is obtained by analyzing the chromatographic analysis component; S42, control the stepper motor to pull the piston to move right to the right limit; open the electromagnetic valve V10, the electromagnetic valve V4, the electromagnetic valve V3, the air pump B2 and the air pump B1, and after vacuumizing, sequentially close the electromagnetic valve V3, the electromagnetic valve V4, the air pump B1, the electromagnetic valve V10 and the air pump B2; open the electromagnetic valve V3, control the stepper motor to push the piston to move left to the buffer chamber liquid level sensor L1 detects the liquid level signal, close the electromagnetic valve V3 and the stepper motor; open the electromagnetic valve V2, control the stepper motor to push the piston to move left to the left limit, close the electromagnetic valve V2 and the stepper motor.

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