A device and method for testing the oxidation deterioration and oxygen dissolution characteristics of a vegetable ester insulating oil

Abstract

The application discloses a kind of plant ester insulating oil oxidation deterioration and oxygen dissolving characteristic testing device and testing method, testing device includes: box, vacuum sealed tank, gas sampling system, temperature control system, sampling system and control system;The tank body bottom of vacuum sealed tank is equipped with sampling port, tank body top is equipped with inlet valve, exhaust valve and water inlet;Gas sampling system includes vacuum pump, pressure gauge, motor cylinder and gas mixing unit;Temperature control system includes temperature sensor, heating device arranged on the outside of tank body and liquid cooling device sleeved on the outside of heating device;Sampling system includes sampling port, sampling valve and external sampler, sampling port is arranged on the bottom of box and is connected with tank body bottom pipeline, sampling valve is arranged in the box between sampling port and tank body;Control system includes controller and man-machine interface.The device uses integrated box model to simulate the oxidation deterioration process of insulating oil under different temperature, pressure and gas environment in long-period operation.

Description

Technical Field

[0001] This invention relates to the field of transformer insulating oil performance testing technology, and in particular to a testing device and method for testing the oxidation degradation and oxygen dissolution characteristics of plant ester insulating oil. Background Technology

[0002] Insulating oil plays a crucial role in the insulation and cooling functions of transformers, and its performance evolution significantly impacts the overall lifespan and condition of the equipment. During actual transformer operation, insulating oil is constantly exposed to a complex environment of sealing, high temperature, and localized overheating, gradually undergoing chemical reactions such as oxidation and hydrolysis, leading to oil deterioration. These changes not only weaken the insulating strength of the oil but also reduce its heat dissipation efficiency, thereby affecting the overall thermal stability and operational safety of the transformer, resulting in decreased insulation performance and even the risk of insulation failure. Insulating oils, especially vegetable ester oils, have relatively poor oxidative stability and are prone to oxidation under high temperature and oxygen catalysis, generating acidic substances, peroxides, and polymers, accompanied by gas release. Simultaneously, vegetable ester oils are hydrophilic; under high temperature or electric field conditions, esters hydrolyze, generating free fatty acids, further exacerbating oil acidification and reducing insulation performance.

[0003] Currently, the evaluation of insulating oil performance mainly relies on a combination of on-site sampling and laboratory analysis. However, conducting tests in the actual operating environment of transformers presents many inconveniences and limitations. On-site sampling is often limited by the energized operating state of the equipment, the sampling points are singular and lack representativeness, making it difficult to comprehensively reflect the true state of the insulating ester oil inside the transformer. Parameters such as temperature and pressure in actual operation are dynamically changing and difficult to control precisely, resulting in unstable on-site test conditions and making it impossible to effectively isolate and systematically study individual influencing factors.

[0004] In contrast, laboratory simulation tests provide a highly controllable, safe, and efficient technical approach for studying the performance of insulating ester oils. The laboratory environment allows for independent or coupled precise control of key parameters such as temperature, pressure, and gas composition, enabling researchers to systematically investigate the degradation mechanisms of insulating ester oils under predetermined conditions. Accelerated aging test methods, such as increasing temperature or oxygen concentration, can simulate the state of insulating oil after long-term operation in a shorter time, significantly shortening the test cycle and saving valuable time for new oil development and performance evaluation. Furthermore, the test process is safer and facilitates condition intervention and process observation.

[0005] However, existing testing devices suffer from problems such as limited functionality and low system integration, making it difficult to meet the comprehensive testing needs of long-term, multi-condition testing. For example, common oven aging tests focus on the evolution of oil chemical indicators, resulting in low system integration, poor sealing, and low control precision, failing to simulate the dynamic operating conditions such as pressure and oscillation in actual transformer operation. While some flow and heat transfer testing platforms can simulate oil flow states, they fail to fully consider the impact of dynamic changes in key physical properties of insulating oil during oxidation and aging, and lack the ability to monitor gas dissolution and release processes in real time. Summary of the Invention

[0006] Objective: To overcome the shortcomings of existing technologies, this invention provides a testing device and method for testing the oxidation degradation and oxygen dissolution characteristics of plant ester insulating oil, enabling the study of the oxidative aging behavior of insulating oil under different operating conditions and the analysis of gas dissolution kinetics.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a testing device for the oxidation degradation and oxygen dissolution characteristics of plant ester insulating oil, comprising: a housing, a vacuum sealed container, a gas injection system, a temperature control system, a sampling system, and a control system; The vacuum sealing container is installed inside the box. The bottom of the vacuum sealing container is equipped with a sampling port, and the top of the container is equipped with an air inlet valve, an air outlet valve, and a water inlet. The gas injection system includes a vacuum pump, a pressure gauge, a motor cylinder, and a gas mixing unit installed inside the chamber. The vacuum pump is used to degas the inside of the chamber. The motor cylinder is used to balance the pressure inside the chamber. The gas mixing unit includes a mass flow meter and a one-way inlet valve. The mass flow meter is used to regulate the mass and / or flow rate of the gas introduced into the chamber, and the one-way inlet valve is used to control the introduction of the test gas. The detection end of the pressure gauge extends into the chamber. The temperature control system includes a temperature sensor, a heating device located on the outside of the tank, and a liquid cooling device sleeved on the outside of the heating device; the temperature sensor includes a first temperature sensor closely attached to the outside of the tank and a second temperature sensor inserted into the inside of the tank. The sampling system includes a sampling port, a sampling valve, and an external sampler; the sampling port is located at the bottom of the housing and connected to a pipeline at the bottom of the tank; the sampling valve is located next to the housing between the sampling port and the tank. The control system includes a controller and a human-machine interface. The controller receives data from the temperature sensor and controls the temperature control system to adjust the temperature inside the tank, receives data from the mass flow meter and operates the one-way air inlet valve to introduce test gas into the tank, and receives data from the pressure gauge and controls the motor cylinder to balance the pressure inside the tank. The human-machine interface is installed outside the enclosure and is used for users to set test parameters and test procedures, and transmits the operation data to the controller.

[0009] The water inlet allows for the injection of a certain amount of water into the tank, simulating the impact of trace water content on oil during actual operation. The vacuum pump and gas mixing unit of the gas sampling system achieve precise control of the gas composition and pressure within the tank. Based on real-time feedback from the pressure gauge, it provides micro-adaptive dynamic compensation for consumed gas during long-cycle oxidation tests, maintaining a constant partial pressure of specific gases within the tank. The temperature control system regulates the tank temperature through heating and liquid cooling devices, simulating the "step heating / cooling" or "periodic temperature cycle" conditions of a transformer. The heating and liquid cooling devices work together, receiving PID closed-loop pulse regulation from the controller to simulate rapid heating / cooling dynamic conditions and achieve dynamic heat balance over long periods. The oscillation system promotes gas-liquid mass transfer balance. The sampling system supports oil sample extraction without disrupting the gas-liquid balance. The control system achieves multi-parameter synchronous monitoring and dynamic process control, acquiring pressure and temperature parameters in real time and recording the gas dissolution kinetics process. Based on the pressure drop signal detected by the pressure gauge (which is caused by the oxidation of insulating oil and consumption of oxygen over a long period), the control system automatically activates the mass flow meter in the gas mixing unit to inject a small amount of target gas, thereby achieving constant pressure compensation for gas-liquid dissolution kinetics over a long period.

[0010] The plant ester insulating oil oxidation degradation and oxygen dissolution characteristics testing device provided by this invention breaks through the limitations of traditional laboratories where multi-factor coupling testing is impossible due to the dispersed equipment. It can simulate the oxidation degradation process of insulating oil under different temperature, pressure and gas environments during long-term operation, and simultaneously study gas dissolution and release behavior, providing a reliable experimental platform for the study of transformer insulating oil aging mechanism, condition assessment and life prediction.

[0011] In some embodiments, the testing apparatus further includes an oscillation system; The oscillation system is mounted on a support frame around the enclosure and includes an ultrasonic oscillator; the ultrasonic oscillator operates at a frequency of 40kHz, has a maximum output power of 100W, and the power is continuously adjustable.

[0012] In some embodiments, the ultrasonic oscillator is connected to the housing via a coupling agent.

[0013] In some embodiments, the vacuum sealing tank has a volume of 1-5 L and a pressure of -0.1 to +0.3 MPa; the top of the tank has a flange sealing structure, and an O-ring is provided at the sealing surface.

[0014] In some embodiments, the vacuum sealing container is made of stainless steel, and the inner wall of the vacuum sealing container is coated with a nano-level oleophobic and anti-fouling coating; the bottom of the container has a 15°-30° conical angle. The piping in the testing device is made of stainless steel.

[0015] Applying a nano-level oleophobic and anti-fouling coating can effectively prevent plant ester insulating oil with high kinematic viscosity from adhering to the tank wall after high-temperature oxidation, thereby eliminating the error in gas phase volume calculation caused by changes in liquid phase volume.

[0016] The vacuum sealing tank is made of stainless steel, which provides high sealing performance and pressure resistance.

[0017] In some embodiments, the temperature control range of the temperature control system is 20-150℃; The heating device is a silicone heating strip or a thin-film heating sheet.

[0018] The temperature control system has a temperature control accuracy of ±1℃, used to simulate the step temperature fluctuations and long-term constant temperature control in actual transformer operation, suppressing the slight thermal runaway during oxidation. The heating and liquid cooling devices work together under the PID closed-loop pulse regulation of the controller, enabling the simulation of dynamic operating conditions such as rapid heating and cooling, as well as the dynamic balance of heat over long periods.

[0019] In some embodiments, the liquid cooling device includes a liquid cooling shell and a heat preservation device. The liquid cooling shell is sleeved outside the heating device and forms a liquid cooling interlayer between the liquid cooling shell and the heating device. The liquid cooling shell has a liquid inlet at the bottom and a liquid outlet at the top for introducing coolant into the liquid cooling interlayer. The heat preservation device is located outside the liquid cooling shell.

[0020] In some embodiments, the sampling valve is a needle valve with an interface adapted to a syringe interface or a standard Luer connector; the sampling valve is provided with a dust cap on the outside; The external sampler is a syringe; In some embodiments, the mass flow meter and the one-way inlet valve are electrically connected to the controller to replenish inert gas into the vacuum-sealed container during sampling based on the negative pressure change monitored by the pressure gauge. Therefore, the sampling system also has a micro-volume compensation function. During sampling, as the oil sample in the vacuum-sealed container decreases and the pressure inside the container changes, the pressure gauge detects the negative pressure change and transmits the pressure data to the controller. The controller then controls the one-way inlet valve to open and controls the inert gas mass flow meter, such as a nitrogen mass flow meter, to replenish inert gas into the vacuum-sealed container, performing isobaric volume compensation to maintain the original gas-liquid dissolution balance inside the container and prevent transient disruption of the total pressure field.

[0021] Secondly, the present invention provides a method for testing the oxidative degradation and oxygen dissolution characteristics of plant ester insulating oil, using the plant ester insulating oil oxidative degradation and oxygen dissolution characteristics testing device as described in the first aspect; the testing method includes: The pretreated insulating oil is injected into a vacuum sealing tank, sealed, and the program is set in the human-machine interface to open the exhaust valve and start the vacuum pump to degas. Close the exhaust valve, first introduce oxygen, then nitrogen, until the pressure gauge shows that the gas pressure inside the tank is equal to the atmospheric pressure, then close the inlet valve. Start the motor cylinder to add water into the tank through the water inlet; Set the target temperature and start the heating and liquid cooling devices; Start the ultrasonic oscillator and apply periodic vibrations; Real-time monitoring of pressure and temperature changes inside the tank, recording gas dissolution or release kinetic data; dynamic adjustment of the working status of the heating device and liquid cooling jacket according to temperature changes to maintain the stability of the test temperature.

[0022] Oil samples are extracted through a sampling valve for gas composition and moisture analysis. Inert gas protection is used during sampling. After the test was completed, the oil sample was drained from the tank, and the composition and volume of the gas phase were tested.

[0023] In some embodiments, the degassing time is ≥2 hours.

[0024] In some embodiments, the tank is cleaned with alcohol after the test is completed.

[0025] Beneficial effects:

[0026] High degree of integration: It integrates functions such as oxidation simulation and gas dissolution, and supports the free combination and setting of various test parameters such as temperature, pressure, and oscillation mode to meet the comprehensive testing needs under different working conditions; Supports long-term continuous testing: It has good sealing performance and stable temperature and pressure control capabilities, and can operate stably and continuously under unattended conditions, providing reliable data support for the study of the evolution law of insulating oil aging performance. High control precision: Temperature control precision ±0.5℃, pressure control precision ±0.5kPa. Through the coordinated adjustment of the external heating device and the liquid cooling jacket, combined with the periodic vibration function, it can simulate the complex operating conditions of transformers, such as temperature fluctuations, pressure changes, and mechanical vibrations. High safety: Equipped with a complete protection system, it has good airtightness and will not have problems with air or oil leakage, further ensuring the safety of the system and the reliability of test data. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the overall structure of the plant ester insulating oil oxidation degradation and oxygen dissolution characteristics testing device in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the test process for the plant ester insulating oil oxidation degradation and oxygen dissolution characteristics test device in an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the temperature control system in an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the structure of the motor cylinder in an embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram of the gas component detector in an embodiment of the present invention.

[0033] In the diagram: 1. Nitrogen inlet valve; 11. Nitrogen mass flow meter; 2. Oxygen inlet valve; 22. Oxygen mass flow meter; 12. Pressure gauge; 13. One-way inlet valve; 3. Vacuum pump; 31. Anti-backflow valve; 32. Exhaust valve; 4. Motor cylinder; 41. Gas component detector; 42. Inlet valve; 43. Cylinder pressure gauge; 44. Volume adjustment piston; 5. Water inlet; 51. One-way valve; 6. Human-machine interface; 61. Temperature control system; 62. First temperature sensor; 63. Second temperature sensor; 101. Liquid inlet; 102. Liquid outlet; 103. Heating device; 104. Liquid-cooled jacket; 105. Insulation device; 106. Liquid-cooled shell; 7. Sampling port; 72. Sampling valve; 71. Sampler; 8. Ultrasonic oscillator; 9. Vacuum sealed container; 10. Box body. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use.

[0035] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may include different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0036] Example 1:

[0037] This embodiment provides a device for testing the oxidation degradation and oxygen dissolution characteristics of vegetable ester insulating oil, such as... Figures 1 to 4 As shown, it includes: a housing 10, a vacuum sealing container 9, a gas injection system, a temperature control system, a sampling system, an oscillation system, and a control system.

[0038] The vacuum sealing container 9 is installed inside the housing 10. The container has a volume of 1L and a pressure of -0.1 to +0.3MPa. The bottom of the container 9 has a sampling port 7, and the top has a flange sealing structure with an O-ring at the sealing surface. The top of the container has an air inlet valve 13, an air outlet valve 32, and a water inlet 5. The water inlet 5 contains a one-way valve 51. The vacuum sealing container 9 is made of stainless steel, and the inner wall is coated with a nano-level oleophobic and anti-fouling coating. The bottom of the container has a 15° conical angle.

[0039] The gas injection system includes a vacuum pump 3, a pressure gauge 12, a motor cylinder 4, and a gas mixing unit. The vacuum pump 3 and the motor cylinder 4 are installed inside the housing 10. The gas mixing unit includes a nitrogen inlet valve 1, an oxygen inlet valve 2, a nitrogen mass flow meter 11, an oxygen mass flow meter 22, and a one-way inlet valve 13. The detection end of the pressure gauge 12 extends into the tank. The vacuum pump 3 is a two-stage rotary vane type with an internal anti-backflow valve 31. The motor cylinder 4 is connected to the sealed gas path of the vacuum sealing tank 9 and has an internal motor-driven volume adjustment piston 44. The motor cylinder 4 has an internal anti-backflow valve. The pressure gauge 12 is a high-precision electronic vacuum pressure gauge used to monitor the gas pressure inside the tank in real time. When the plant ester insulating oil undergoes an oxidation reaction that consumes oxygen or when gas dissolution causes a slight drop in the pressure inside the tank, the controller, based on the pressure feedback signal, drives the motor cylinder 4 to push the volume adjustment piston 44 to compress the gas phase volume to maintain the set absolute constant pressure inside the tank, and calculates the gas dissolution and consumption kinetic volume in real time based on the motor displacement. A gas component detector 41 and an inlet valve 42 are sequentially installed between the motor cylinder 4 and the vacuum sealing tank 9; the structure of the gas component detector 41 is as follows: Figure 5 As shown, the intake valve 42 is in the open state during the operation of the motor cylinder 4. The motor cylinder 4 also includes a cylinder pressure gauge 43 for monitoring the pressure inside the motor cylinder.

[0040] The temperature control system 61 includes a first temperature sensor 62, a second temperature sensor 63, a heating device 103 disposed on the outside of the vacuum-sealed container 9, and a liquid cooling device sleeved on the outside of the heating device. The first temperature sensor 62 is in close contact with the outside of the vacuum-sealed container 9, and the second temperature sensor 63 is inserted into the inside of the vacuum-sealed container 9. The temperature control range of the temperature control system 61 is 20-150℃. In this embodiment, the heating device 103 is a silicone heating strip or a thin-film heating sheet. The liquid cooling device includes a liquid cooling shell 106 and a heat preservation device 105. The liquid cooling shell 106 is sleeved on the outside of the heating device 103, forming a liquid cooling interlayer 104 between them. A liquid inlet 101 is opened on the lower side of the liquid cooling shell 106, and a liquid outlet 102 is opened on the upper side of the liquid cooling shell 106 for introducing coolant into the liquid cooling interlayer 104. The heat preservation device 105 is disposed on the outside of the liquid cooling shell 106.

[0041] The sampling system includes a sampling port 7, a sampling valve 72, and an external sampler 71. The sampling port 7 is located at the bottom of the housing 10 and connected to the bottom pipeline of the vacuum-sealed container 9. The sampling valve 72 is located beside the housing 10 between the sampling port 7 and the container. The external sampler 71 is a syringe. The sampling valve 72 is a needle valve with an interface adapted to a syringe interface or a standard Luer connector; the sampling valve 72 is equipped with a dust cap. The sampling system also has a gas micro-volume compensation function, which can automatically replenish inert gas according to the monitored negative pressure changes. Specifically, the nitrogen mass flow meter 11 and the one-way inlet valve 13 are electrically connected to the controller. During the synchronous process of extracting a preset volume of oil sample, the controller controls the one-way inlet valve 13 to open and controls the nitrogen mass flow meter 11 to replenish nitrogen into the vacuum-sealed container for isobaric volume compensation.

[0042] The oscillation system is mounted on supports around the enclosure 10 and includes an ultrasonic oscillator 8, which is connected to the enclosure 10 via a coupling agent. The ultrasonic oscillator 8 operates at a frequency of 40kHz, has a maximum output power of 100W, and the power is continuously adjustable.

[0043] The control system includes a controller and a human-machine interface (HMI). The controller receives data from the temperature sensor and controls the temperature control system 61 to adjust the temperature inside the vacuum sealing tank 9; receives data from the nitrogen mass flow meter 11 and the oxygen mass flow meter 22 and operates the test gas check valve 13 to introduce gas into the tank; and receives data from the pressure gauge 12 and controls the motor cylinder 4 to balance the pressure inside the tank. The HMI is installed outside the housing 10 and is used by the user to set test parameters and test procedures, and transmits the operation data to the controller 6.

[0044] In this embodiment, all pipelines are made of stainless steel.

[0045] Example 2:

[0046] This embodiment provides a method for testing the oxidation degradation and oxygen dissolution characteristics of vegetable ester insulating oil, using the testing device for the oxidation degradation and oxygen dissolution characteristics of vegetable ester insulating oil as described in Embodiment 1. The testing method includes:

[0047] Step 1: Take 800 mL of FR3 plant ester insulating oil, pre-treat it by dehydration and degassing, and then inject it into vacuum sealing container 9 and seal it. The pre-treatment method includes: heating the plant ester insulating oil until the oil temperature rises uniformly to 60-70℃, using a vacuum oil filter to dehydrate and degas it, and filtering out small solid particles with a filter element (1-5 μm). After sampling and testing, the oil is injected into the vacuum container.

[0048] Step 2: Set the degassing program in the human-machine interface, open the exhaust valve 32 and start the vacuum pump 3 for degassing. The degassing time is 2 hours.

[0049] Step 3: After degassing, set the gas composition (20% O2, 80% N2), target pressure, and test temperature (80℃) on the human-machine interface; the system automatically closes the exhaust valve 32, opens the nitrogen inlet valve 1, oxygen inlet valve 2, and one-way inlet valve 13 to inject gas; the motor cylinder 4 is started to balance the pressure inside the tank; water is added to the tank through the water inlet 5; the heating device 61 and ultrasonic oscillator 8 are started to begin the test.

[0050] Step 4: Record pressure changes every 24 hours and take samples for analysis every 7 days, with a cycle of 42 days.

[0051] Step 5: After the test, the system stops heating and oscillation, and slowly exhausts the gas through the human-machine interface 6. Finally, the oil sample is discharged and the vacuum-sealed container is cleaned with alcohol.

[0052] Step 6: Set different operating conditions (intake volume, temperature) and repeat steps 1 to 5.

[0053] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "up," "down," "front," "rear," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to explain the relative positional relationship and movement between components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. These terms are used only for the convenience of describing the invention and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0054] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0055] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A device for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil, characterized in that, include: Box housing, vacuum sealing container, gas injection system, temperature control system, sampling system and control system; The vacuum sealing container is installed inside the box. The bottom of the vacuum sealing container is equipped with a sampling port, and the top of the container is equipped with an air inlet valve, an air outlet valve, and a water inlet. The gas injection system includes a vacuum pump, a pressure gauge, a motor cylinder, and a gas mixing unit installed inside the chamber. The vacuum pump is used to degas the inside of the chamber. The motor cylinder is used to balance the pressure inside the chamber. The gas mixing unit includes a mass flow meter and a one-way inlet valve. The mass flow meter is used to regulate the flow rate of gas introduced into the chamber, and the one-way inlet valve is used to control the introduction of the test gas. The detection end of the pressure gauge extends into the chamber. The temperature control system includes a temperature sensor, a heating device located on the outside of the tank, and a liquid cooling device sleeved on the outside of the heating device; the temperature sensor includes a first temperature sensor closely attached to the outside of the tank and a second temperature sensor inserted into the inside of the tank. The sampling system includes a sampling port, a sampling valve, and an external sampler; the sampling port is located at the bottom of the housing and connected to a pipeline at the bottom of the tank; the sampling valve is located next to the housing between the sampling port and the tank. The control system includes a controller and a human-machine interface. The controller receives data from the temperature sensor and controls the temperature control system to adjust the temperature inside the tank, receives data from the mass flow meter and operates the one-way air inlet valve to introduce test gas into the tank, and receives data from the pressure gauge and controls the motor cylinder to balance the pressure inside the tank. The human-machine interface is installed outside the enclosure and is used for users to set test parameters and test procedures, and transmits the operation data to the controller.

2. The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil according to claim 1, characterized in that, It also includes oscillation systems; The oscillation system is installed around the enclosure and includes an ultrasonic oscillator; the ultrasonic oscillator is connected to the enclosure via a coupling agent; the ultrasonic oscillator operates at a frequency of 40kHz, has a maximum output power of 100W, and the power is continuously adjustable.

3. The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil according to claim 1, characterized in that, The vacuum sealing tank has a volume of 1-5 L and a pressure of -0.1 to +0.3 MPa; the top of the tank has a flange sealing structure and an O-ring is provided at the sealing surface.

4. The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil according to claim 1 or 3, characterized in that, The vacuum sealing container is made of stainless steel, and the inner wall of the container is coated with a nano-level oleophobic and anti-fouling coating; the bottom of the container has a 15°-30° conical angle. The piping in the testing device is made of stainless steel.

5. The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil according to claim 1, characterized in that, The temperature control system has a temperature control range of 20-150℃; The heating device is a silicone heating strip or a thin-film heating sheet.

6. The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil according to claim 1 or 5, characterized in that, The liquid cooling device includes a liquid cooling shell and a heat preservation device. The liquid cooling shell is fitted outside the heating device and forms a liquid cooling interlayer between the liquid cooling shell and the heating device. The liquid-cooled housing has a liquid inlet at the bottom and a liquid outlet at the top for introducing coolant into the liquid-cooled jacket. The heat preservation device is located outside the liquid-cooled shell.

7. The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil according to claim 1, characterized in that, The sampling valve is a needle valve with an interface adapted to a syringe interface or a standard Luer connector; the sampling valve is equipped with a dust cap on the outside. The external sampler is a syringe.

8. The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil according to claim 1 or 7, characterized in that, The mass flow meter and the one-way inlet valve are electrically connected to the controller and are used to replenish inert gas into the vacuum sealed container according to the negative pressure change monitored by the pressure gauge during sampling.

9. A method for testing the oxidative degradation and oxygen solubility characteristics of vegetable ester insulating oil, characterized in that, The apparatus for testing the oxidative degradation and oxygen dissolution characteristics of vegetable ester insulating oil as described in any one of claims 1-8 is used; the test method includes: Inject insulating oil into the vacuum sealing tank, seal it, set the program on the human-machine interface, open the exhaust valve and start the vacuum pump to degas; Close the exhaust valve, first introduce oxygen, then nitrogen, until the pressure gauge shows that the gas pressure inside the tank is equal to the atmospheric pressure, then close the inlet valve. Start the motor cylinder to add water into the tank through the water inlet; Set the target temperature and start the heating and liquid cooling devices; Start the ultrasonic oscillator and apply periodic vibrations; Real-time monitoring of pressure and temperature changes inside the tank, recording gas dissolution or release kinetic data; dynamic adjustment of the working status of the heating device and liquid cooling jacket according to temperature changes to maintain the stability of the test temperature; Oil samples are extracted through a sampling valve for gas composition and moisture analysis. Inert gas protection is used during sampling. After the test was completed, the oil sample was drained from the tank, and the composition and volume of the gas phase were tested.

10. The test method according to claim 9, characterized in that, The degassing time is ≥2 hours, and the tank is cleaned with alcohol after the test is completed.

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