Transformer oil circulation plasma enhancement method and system

Abstract

The invention relates to a transformer oil circulation plasma enhancement method and system, a dielectric barrier discharge plasma device is arranged in an oil duct of a transformer oil tank, the ionic wind effect generated by the dielectric barrier discharge plasma device is used for driving oil to accelerate flow circulation, and therefore traditional mechanical oil pump driving is replaced. The high-voltage electrode of the dielectric barrier discharge plasma device is completely wrapped in the dielectric barrier layer so as to ensure discharge safety, the control unit adaptively adjusts the discharge intensity through the sensor, and rapid cut-off protection is carried out when abnormity occurs. The dielectric barrier discharge plasma device synchronously decomposes fault gas in oil in the process of driving the oil to accelerate circulation, and integration of dual functions of transformer oil cooling and insulation purification is achieved. The device does not need moving parts, is low in power consumption, long in service life, intelligent and suitable for a high-voltage-class oil-immersed transformer.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of transformer thermal management, in particular to a method and system for enhancing transformer oil circulation heat dissipation. BACKGROUND

[0002] With the continuous improvement of voltage level and transmission capacity of power system, the thermal management performance of oil-immersed transformer as the core equipment of power grid is directly related to the operation reliability and service life. The traditional oil-immersed transformer generally adopts mechanical oil pump to drive transformer oil circulation heat dissipation. This method has exposed many inherent defects in decades of application: first, as a moving part, the mechanical oil pump has problems such as bearing wear and seal aging during long-term operation, and the failure rate accounts for more than 30% of the auxiliary equipment failure of the transformer, and maintenance needs power-off operation, affecting power supply reliability; second, the power consumption of oil pump motor is significant, and for extra-high voltage transformer, the annual power consumption of cooling system can reach tens of thousands of degrees, which does not meet the energy saving and consumption reduction requirements of power grid; third, the noise and vibration of oil pump cause environmental disturbance to urban substations and densely populated areas; finally, the existing mechanical oil pump is mostly operated at a constant speed, which is difficult to adapt to the dynamic changes of transformer load, resulting in excessive cooling at light load and insufficient cooling at heavy load, and cannot be intelligently adjusted.

[0003] In recent years, some researches have tried to use electric field or magnetic field to drive oil circulation to avoid mechanical parts, but there are still technical obstacles to be overcome. Whether it is electric field or magnetic field driving, the existing solutions need to add a large number of conductive or magnetic particles to the oil, which significantly reduces the insulation strength of the oil, and the latter (magnetic particles) will interact with the external strong magnetic field to cause electromagnetic interference to the transformer protection device.

[0004] In addition, during the long-term operation of the transformer, partial discharge and overheating will cause the insulation oil to crack, continuously generating fault characteristic gases such as C2H2, C2H4, CH4, etc. The accumulation of these gases in the oil will significantly reduce the insulation strength of the oil and accelerate the deterioration of the oil quality. The existing technology mostly uses offline or independent online degassing devices to process the oil, but such devices have complex structure and cannot work cooperatively with the transformer cooling system.

[0005] Therefore, the industry needs a better solution for the oil driving and fault gas problems of the transformer. SUMMARY

[0006] To solve at least one of the technical problems in the background art, the present application provides a transformer oil circulation plasma enhancement method and system.

[0007] The solution of the present application is as follows:

[0008] A transformer oil circulation plasma enhanced method, the transformer comprises an oil tank, the oil outlet of the oil tank is arranged on the upper portion of the oil tank, and the oil inlet is arranged on the lower portion of the oil tank, characterized in that a dielectric barrier discharge plasma device is additionally arranged in the oil tank, and the ion wind effect generated by the dielectric barrier discharge plasma device is used to drive the oil to accelerate and flow to the oil outlet, so that the mechanical oil pump oil circulation driving scheme is replaced; the dielectric barrier discharge plasma device comprises a high-voltage electrode and a ground electrode matched with each other, the high-voltage electrode is completely wrapped by a dielectric barrier layer, and the safety of discharge is ensured.

[0009] The dielectric barrier discharge plasma device of the application generates non-equilibrium low-temperature plasma to drive the transformer oil to accelerate and circulate, and the active particles in the plasma automatically decompose the fault characteristic gas dissolved in the oil, so that the cooling efficiency is improved and the online purification of the transformer oil insulation is realized.

[0010] Another solution of the application is as follows:

[0011] A transformer oil circulation plasma enhanced system comprises a transformer and an external heat sink, the transformer comprises an oil tank, a winding and an iron core are arranged in the oil tank, and the spacing between the winding and the iron core and the top and bottom of the oil tank is respectively a top main oil passage and a bottom main oil passage, an oil outlet and an oil inlet are respectively arranged on the upper portion and the lower portion of the side wall of the oil tank, and the external heat sink is in communication with the top main oil passage and the bottom main oil passage through the top main oil passage and the bottom main oil passage.

[0012] The enhanced system further comprises a dielectric barrier discharge plasma device, the dielectric barrier discharge plasma device comprises an alternating power supply and an electrode pair, the electrode pair comprises a high-voltage electrode and a ground electrode, the high-voltage electrode and the ground electrode are respectively connected with the alternating power supply through insulation power conductors sealed and passed out of the oil tank, the high-voltage electrode is a needle electrode and is completely wrapped by a dielectric barrier layer, and the ground electrode is an arc-shaped plate electrode, the needle electrode and the plate electrode are oppositely arranged in the top main oil passage, and the plate electrode is used to receive hot oil from the winding and the iron core of the transformer and guide the hot oil to flow to the oil outlet.

[0013] The enhanced system is an application of the enhanced method. After the needle electrode and the plate electrode of the enhanced system are started, non-equilibrium low-temperature plasma is generated between the needle electrode and the plate electrode, the ion wind effect is formed, a horizontal velocity component is generated, and the oil is driven to accelerate and flow to the oil outlet. The arc-shaped plate electrode of the application plays two roles, one is to guide the hot oil to flow in a specified direction as a flow guide plate, and the other is to generate non-equilibrium low-temperature plasma with the needle electrode and generate a horizontal velocity component to drive the oil to accelerate and circulate. In the environment of the oil-immersed transformer, the flow guide plate is a necessary component for guiding the hot oil to flow in a specified direction and avoiding flow dead zones. In the application, the arc-shaped plate electrode plays two roles, so the number of components can be reduced, and the space occupied by the components in the oil tank of the transformer can be reduced.

[0014] As a preferred embodiment of the present application: the arc-shaped plate electrode has an introduction end and a leading-out end, both of which are formed by gradually bending horizontally and downward, wherein the introduction end has a larger curvature, and the needle electrode is arranged close to the leading-out end to facilitate the flow of the driven oil to the oil outlet.

[0015] As a further optimization scheme: the enhancement system further comprises a plasma control unit and a sensor for monitoring the oil temperature, the sensor is connected to the plasma control unit through an insulated signal lead wire sealed out of the oil tank, and the plasma control unit is connected to the alternating power supply;

[0016] The plasma control unit adjusts the output power of the alternating power supply according to the obtained oil temperature to determine the cooling requirement.

[0017] The enhancement system is also provided with a sensor for monitoring the oil quality, which is also connected to the plasma control unit through an insulated signal lead wire sealed out of the oil tank, and the plasma control unit adjusts the output power of the alternating power supply according to the fault characteristic gas concentration information obtained through the sensor.

[0018] The enhancement system is also provided with a sensor for monitoring the oil flow rate, which is also connected to the plasma control unit through an insulated signal lead wire sealed out of the oil tank, and the plasma control unit also adjusts the output power of the alternating power supply according to the oil flow rate information obtained through the sensor.

[0019] The enhancement system further comprises a redundant circuit breaker arranged in the connection line between the high-voltage electrode and the alternating power supply, and the plasma control unit is connected to the redundant circuit breaker, which is controlled to be disconnected within <10 ms when the plasma control unit monitors abnormal oil temperature, oil flow rate or fault characteristic gas concentration, thereby better ensuring the safety of the system.

[0020] The optimization scheme improves the intelligence of the enhancement system of the present application and better ensures the safety of the enhancement system of the present application.

[0021] The top of the oil tank is provided with a gas collection chamber communicating with the inside of the oil tank, and the gas collection chamber is controlled to discharge gas through a gas discharge valve.

[0022] Beneficial effects:

[0023] Compared with the prior art, the present application avoids mechanical moving parts, realizes safe, low-energy-consumption, long-life, intelligent oil circulation enhancement, and simultaneously solves the problem of fault gas accumulation, which is specifically manifested as follows:

[0024] 1) The application utilizes the ion wind effect generated by dielectric barrier discharge to drive transformer oil acceleration circulation, realizes oil circulation enhancement without mechanical moving parts, ensures discharge safety by completely wrapping the high-voltage electrode in the dielectric barrier layer, completely solves the problems of bearing wear, seal aging, noise vibration and energy consumption of traditional oil pumps, the total energy consumption of the system is only 5%-8% of that of the traditional oil pump cooling, the failure rate is reduced by more than 90%, the maintenance-free long-life operation of the transformer is realized, the overall reliability of the transformer can be significantly improved, compared with the electric field or magnetic field driving scheme, the behavior of adding conductive or magnetic particles to the transformer oil which affects the safety control of the transformer is avoided;

[0025] 2) The application utilizes the non-equilibrium low-temperature plasma driven by dielectric barrier discharge to drive oil acceleration circulation, and the active particles in the plasma automatically decompose the fault characteristic gases such as C2H2, C2H4, CH4 dissolved in the oil, realizing the integration of cooling efficiency improvement and online purification of transformer oil insulation, compared with independent oil treatment device, the equipment cost and maintenance complexity are reduced;

[0026] 3) The plasma control unit judges the load change through oil temperature, oil quality, oil flow rate and other parameters, realizes self-adaptive intelligent adjustment of cooling power, solves the problem of excessive cooling or insufficient cooling caused by fixed-speed operation of mechanical oil pump, and optimizes the transformer operation temperature curve. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 , 2 The figure is a structural schematic diagram of the transformer oil circulation plasma enhancement system of the preferred embodiment of the application.

[0028] Mark explanation:

[0029] 1. Transformer oil tank; 2. Top main oil way; 3. Electrode pair; 4. Alternating power supply; 5. Plasma control unit; 6. Temperature sensor array; 7. Oil quality monitoring sensor; 8. Flow rate sensor; 9. Insulation signal wire; 10. Dielectric barrier layer; 11. High-voltage electrode; 12. Insulation power wire; 13. Sealing rubber ring; 14. Ground electrode; 15. Redundant circuit breaker; 16. Gas collection chamber; 17. Transformer oil; 18. Winding; 19. Core; 20. Exhaust valve; 21. Oil inlet; 22. Oil outlet. DETAILED DESCRIPTION

[0030] The application scheme will be further described in detail below in combination with specific embodiments and drawings. In the application scheme, the core, the iron core, the magnetic core and the magnetic core are not distinguished.

[0031] Example one

[0032] ​This embodiment addresses the oil-driven and fault gas problems in existing transformer technologies by proposing a solution that achieves safe, long-life, and low-energy-consumption oil circulation enhancement while avoiding mechanical moving parts, and simultaneously solves the problem of fault gas accumulation.

[0033] A method for enhancing transformer oil circulation with plasma is disclosed. The transformer includes an oil tank with an oil outlet at the top and an oil inlet at the bottom. A dielectric barrier discharge plasma device is added inside the oil tank. The ion wind effect generated by the plasma device drives the oil to flow faster towards the oil outlet, thereby replacing the mechanical oil pump circulation drive scheme. The dielectric barrier discharge plasma device includes a high-voltage electrode and a ground electrode. The high-voltage electrode is completely wrapped by a dielectric barrier layer to ensure discharge safety.

[0034] This embodiment primarily replaces the traditional mechanical oil pump drive system with a non-equilibrium low-temperature plasma driven by a dielectric barrier discharge plasma device to accelerate oil circulation. By completely encasing the high-voltage electrodes with a dielectric barrier layer, the system's discharge safety is ensured, completely resolving the issues of bearing wear, seal aging, noise, vibration, and energy consumption inherent in traditional oil pumps. The system's total energy consumption can be reduced to 5%-8% of that of traditional oil pump cooling, and the failure rate can be reduced by over 90%, enabling maintenance-free, long-life operation of the transformer and significantly improving its overall reliability. Compared to electric or magnetic field drive systems, this avoids the addition of conductive or magnetic particles to the transformer oil, which could compromise transformer safety control.

[0035] In this embodiment, a non-equilibrium low-temperature plasma is generated by a dielectric barrier discharge plasma device to drive the transformer oil to accelerate circulation. At the same time, the active particles in the plasma automatically decompose the fault characteristic gases dissolved in the oil, such as C2H2, C2H4, and CH4, into harmless small molecules, avoiding gas accumulation that leads to a decrease in oil insulation strength. This achieves the integration of dual functions: improving cooling efficiency and online purification of transformer oil insulation. Compared with a separate oil treatment device, this reduces equipment costs and maintenance complexity.

[0036] Example 2

[0037] This embodiment aims to provide an application of the enhanced method of Embodiment 1.

[0038] The transformer oil circulation plasma enhancement system in this embodiment is as follows: Figure 1 As shown, the transformer mainly includes an oil tank 1 and an iron core 19 and windings 18 disposed therein. The gaps between the iron core 19 and windings 18 and the top and bottom of the oil tank 1 respectively form the top main oil passage 2 and the bottom main oil passage of the oil tank 1. The oil outlet 22 and the oil inlet 21 are respectively located on the upper and lower parts of the side wall of the oil tank 1, and are connected to the top main oil passage 2 and the bottom main oil passage respectively.

[0039] Transformer oil 17 enters the oil tank 1 from the bottom oil inlet 21, flows upward through the iron core 19 and winding 18 and absorbs heat. After the density decreases, it naturally rises to the top of the oil tank 1 and collects in the top main oil channel 2. Then it flows from the oil outlet 22 through the radiator return oil pipe into the radiator for cooling and then flows back to the oil tank 1 from the oil inlet 21.

[0040] The above is actually a common configuration for transformers in this embodiment and in the prior art. Compared with the prior art, this embodiment also makes the following improvements:

[0041] like Figure 1 , 2 As shown, the transformer in this embodiment is also equipped with a dielectric barrier discharge plasma device. The dielectric barrier discharge plasma device in this embodiment consists of a plasma control unit 5, an alternating power supply 4, various sensors, and electrode pairs 3.

[0042] Electrode pair 3 includes a high-voltage electrode 11 and a ground electrode 14, which are sealed through the top wall of the oil tank 1 and connected to the alternating power supply 4 via insulated power wires 12. The high-voltage electrode 11 is a needle electrode (in this embodiment, a needle electrode refers to an electrode structure with a discharge tip, not limited to a long, thin, pointed structure), completely encased in a dielectric barrier layer 10. The ground electrode 14 is an arc-shaped plate electrode, connected to the transformer oil tank 1 as a reference ground potential. The needle and plate are arranged vertically opposite each other in the main oil passage 2 at the top of the oil tank 1. Upon startup, a non-equilibrium low-temperature plasma is generated between them, forming an ion wind effect and producing a horizontal velocity component, driving the oil to accelerate towards the oil outlet 22.

[0043] In this embodiment, the arc-shaped plate electrode has two functions. On the one hand, it acts as a flow guide plate to receive hot oil from the transformer winding 18 and the iron core 19 and guide the hot oil to flow in a specified direction. On the other hand, it is paired with the needle electrode to generate non-equilibrium low-temperature plasma and generate a horizontal velocity component to drive the oil to accelerate its flow and circulation.

[0044] In an oil-immersed transformer environment, the flow guide plate is an essential component that guides the hot oil to flow in a designated direction and avoids flow dead zones. In this embodiment, an arc-shaped plate electrode serves a dual function, which can reduce the number of components and the space occupied in the transformer tank.

[0045] In this embodiment, electrode pair 3 can be arranged in more than one pair as needed.

[0046] like Figure 2 As shown, in this embodiment, one end of the arc-shaped plate electrode is the inlet end and the other end is the outlet end. The outlet end points to the oil outlet 22 of the oil tank 1. Both ends are formed by gradually bending downwards from the horizontal. The inlet end has a larger curvature and the needle electrode is set closer to the outlet end to facilitate the flow of oil towards the outlet.

[0047] In this embodiment, the needle electrode is made of tungsten alloy, with a diameter of 2mm and a tip curvature radius of 50μm. The plate electrode is made of stainless steel, with dimensions of 50mm × 30mm × 2mm.

[0048] The dielectric barrier layer 10 is recommended to be an alumina ceramic layer or a polyimide film with a thickness of 0.5 mm or more, or other materials, to ensure that the discharge between the two electrodes is a micro-discharge rather than an arc discharge. Specifically, in this embodiment, the coating layer of the needle electrode is formed by plasma spraying, and the material is alumina ceramic with a purity of 99%, a thickness of 0.5 mm ± 0.05 mm, a dielectric constant of 9.8, and a withstand field strength > 20 kV / mm.

[0049] The sensors used in this embodiment include a temperature sensor array 6, an oil quality monitoring sensor 7, and a flow rate sensor 8. These sensors are connected to the plasma control unit 5 via insulated signal wires 9, which pass through a sealed section on the top wall of the oil tank 1. The plasma control unit 5 uses these sensors to monitor the oil temperature, dissolved gas concentration and dielectric strength, and oil flow rate in real time. The plasma control unit 5 is also connected to an alternating power supply 4 and a redundant circuit breaker 15 via signal wires 9. The redundant circuit breaker 15 is installed in the connection line between the high-voltage electrode 11 and the alternating power supply 4.

[0050] The plasma control unit 5 dynamically adjusts the discharge of electrode pair 3 by controlling the alternating power supply 4 based on oil temperature, oil flow rate, and the concentration of fault-characteristic gases. For example, if the plasma control unit 5 predicts the cooling demand based on the oil temperature, it activates the alternating power supply 4 to apply a high-frequency pulse voltage to electrode pair 3, causing it to generate micro-discharge and form an ion wind, driving hot oil from oil outlet 22 to the radiator for cooling. The flow rate is recommended to be controlled at 0.1-0.5 m / s. Compared to natural oil convection, this can increase the speed by 10%-30%, comparable to using an oil pump. For example, when the plasma control unit 5 detects that the transformer oil temperature exceeds the limit, it gradually increases the power of the alternating power supply 4; when the concentration of fault characteristic gases such as C2H2, C2H4, and CH4 is detected to be >1ppm, the discharge intensity is increased up to 50W to strengthen gas decomposition; when the load is reduced or the oil quality is good, the dielectric barrier discharge plasma device automatically reduces the power or goes into sleep mode to avoid excessive processing and energy consumption; when an abnormality is detected, such as oil temperature >90℃ or oil flow rate >1m / s or oil flow rate <0.05m / s (determined as drive failure), the redundant circuit breaker 15 cuts off the current supplied by the alternating power supply 4 to the electrode pair 3 within <10ms to prevent the fault from expanding and better ensure system safety.

[0051] The alternating power supply 4 outputs high-frequency, high-voltage pulses. In this embodiment, its frequency range is 10-100kHz, pulse width range is 0.1-5μs, voltage amplitude range is 5-15kV, pulse rise time is <50ns, and the average output power is controlled to ≤50W per electrode group. The plasma control unit 5 achieves adaptive matching of output power by dynamically adjusting the pulse width, voltage amplitude, and frequency of the output waveform of the alternating power supply 4.

[0052] In this embodiment, the average power consumption of a single electrode group is ≤50W, and the total energy consumption of the system is only 5%-8% of that of traditional oil pump cooling. The annual power saving can reach tens of thousands of kWh, which greatly reduces the operating cost of the substation and meets the requirements of green power grid energy conservation and consumption reduction.

[0053] The gas collection chamber 16 is located at the top of the oil tank 1 and is connected to the main oil passage 2. It is used to collect the non-condensable gases produced by decomposition and the original (pre-decomposition) gases in the oil. The exhaust valve 20 on it is used for periodic exhaust.

[0054] In this embodiment, the insulated power conductor 12 has a withstand voltage rating of 30kV. The insulated power conductor 12 is sealed to the tank wall with a double sealing ring 13. The inner ring of the double sealing ring 13 is a fluororubber O-ring, and the outer ring is a polytetrafluoroethylene V-ring, which can ensure that the annual leakage rate of the tank is <0.1%.

[0055] This embodiment is an application of Embodiment 1. Based on Embodiment 1, the following design has been optimized:

[0056] 1) The electrode pair structure has been optimized: In this embodiment, the arc plate electrode performs two functions, which reduces the number of components and reduces the space occupied by the transformer tank.

[0057] 2) Intelligentization is achieved: The plasma control unit judges the load change by parameters such as oil temperature, oil quality, and oil flow rate, and realizes adaptive intelligent adjustment of cooling power, which solves the problem of over-cooling or under-cooling caused by the fixed speed operation of mechanical oil pump, and optimizes the transformer operating temperature curve.

[0058] 3) Further enhances system safety: By monitoring anomalies through the plasma control unit and combining redundant circuit breakers for rapid disconnection protection within <10ms, the risk of arc igniting transformer oil can be fundamentally eliminated, thus better ensuring system safety.

[0059] In summary, this invention achieves low power consumption, long lifespan, and intelligent cooling while simultaneously improving the insulation performance and operational safety of transformers. It is particularly suitable for thermal management of transformers in ultra-high voltage, large-capacity, and unattended substations, providing a revolutionary solution for oil-immersed transformer cooling technology. Furthermore, the driving efficiency of this invention's drive scheme is unaffected by changes in oil viscosity with temperature, avoiding the problem of uneven flow rates when dealing with hot and cold oil in traditional oil pumps, resulting in a more stable oil flow rate.

Claims

1. A method for plasma enhancement of transformer oil circulation, wherein the transformer includes an oil tank, the oil outlet of which is located at the upper part and the oil inlet at the lower part, characterized in that, A dielectric barrier discharge plasma device is added inside the oil tank, and the ion wind effect generated by it drives the oil to flow faster toward the oil outlet. The dielectric barrier discharge plasma device includes a high-voltage electrode and a ground electrode, and the high-voltage electrode is completely wrapped by a dielectric barrier layer.

2. A transformer oil circulating plasma enhancement system, comprising a transformer and an external radiator, wherein the transformer includes an oil tank, and windings and a core are disposed inside the oil tank. The intervals between the windings and the top and bottom of the oil tank are respectively the top main oil passage and the bottom main oil passage. The oil outlet and the oil inlet are respectively located on the upper and lower parts of the side wall of the oil tank. The external radiator is connected to the top main oil passage and the bottom main oil passage through them respectively. Its features are, The enhancement system also includes a dielectric barrier discharge plasma device, which includes an alternating power supply and an electrode pair. The electrode pair includes a high-voltage electrode and a ground electrode, which are respectively sealed through an insulated power wire after exiting the oil tank and connected to the alternating power supply. The high-voltage electrode is a needle electrode, which is completely wrapped by a dielectric barrier layer. The ground electrode is an arc-shaped plate electrode. The needle and plate electrodes are arranged opposite each other in the top main oil channel. The plate electrode is used to receive hot oil from the transformer windings and core and guide the hot oil to the oil outlet.

3. The enhancement system according to claim 2, characterized in that, The arc-shaped plate electrode has an inlet end and an outlet end, both of which are formed by gradually bending downwards from the horizontal. The inlet end has a greater curvature, and the needle electrode is positioned close to the outlet end.

4. The enhancement system according to claim 3, characterized in that, The enhancement system also includes a plasma control unit and a sensor for monitoring oil temperature. The sensor is connected to the plasma control unit after passing through the oil tank in an insulated signal wire. The plasma control unit is connected to the alternating power supply. The plasma control unit determines the cooling requirement based on the acquired oil temperature and adjusts the output power of the alternating power supply.

5. The enhancement system according to claim 4, characterized in that, The enhancement system is also equipped with a sensor for monitoring oil quality. This sensor is also connected to the plasma control unit after passing through the oil tank in an insulated signal wire. The plasma control unit adjusts the output power of the alternating power supply based on the fault characteristic gas concentration information obtained through the sensor.

6. The enhancement system according to claim 5, characterized in that, The enhancement system is also equipped with a sensor for monitoring oil flow rate. This sensor is also connected to the plasma control unit after passing through the oil tank in an insulated signal wire. The plasma control unit adjusts the output power of the alternating power supply based on the oil flow rate information obtained through the sensor.

7. The enhancement system according to claim 6, characterized in that, The enhancement system also includes a redundant circuit breaker, which is installed in the connection line between the high-voltage electrode and the alternating power supply. The plasma control unit is connected to the redundant circuit breaker and controls the redundant circuit breaker to disconnect within <10ms when it detects abnormal oil temperature, oil flow rate or fault characteristic gas concentration.

8. The enhancement system according to claim 2, characterized in that, The top of the oil tank is equipped with a gas collection chamber that communicates with its interior, and the gas collection chamber is controlled to release gas through an exhaust valve.

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