Transformer oil changing device, oil changing method and application

Abstract

The application discloses a transformer oil changing equipment and method, which comprises a coaxial pipe, one end of the coaxial pipe is provided with a flexible elbow pipe, a stretching cylinder is arranged outside the coaxial pipe, and the driving end of the stretching cylinder is connected to the inside of the tail end of the flexible elbow pipe through a flexible steel cable. The coaxial pipe oil-gas two-way separation mode is adopted to discharge and inject oil for the transformer. When discharging oil, the starting position of the coaxial pipe and the injection pipe is at the bottom of the transformer, nitrogen is filled to balance the internal pressure, and the oil can be completely discharged; when injecting oil, the starting position of the exhaust pipe in the coaxial pipe is at the top of the transformer shell, the internal gas of the transformer can be exhausted, and the oil can be fully injected; the internal pressure of the transformer shell can be controlled and the load of the oil-immersed transformer can be monitored during operation; the transformer oil and nitrogen can guarantee the insulation effect during the oil changing process; the inert gas nitrogen and the safety monitoring can reduce the safety hidden danger during the oil changing process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformer, in particular to transformer oil changing equipment. BACKGROUND

[0002] Oil-immersed transformer is a new type of high-performance transformer with more reasonable structure and better performance. The high-voltage end is at the top of the oil-immersed transformer, and the limited height at the top cannot be operated in any way, so the only place that can be operated is the oil outlet at the bottom. During the oil changing process, the core of the oil-immersed transformer will switch between two insulation cooling forms of insulation oil and gas. Due to the poor gas cooling, the transformer load needs to be limited to reduce safety hazards.

[0003] 10kV oil-immersed transformer belongs to a common oil-immersed transformer model, and is a transformer that can be changed in a conventional power-off manner. When changing oil, a standby transformer is usually changed first to prevent the power-off time from being too long. The changed transformer is transported to a transformer maintenance point or a transformer manufacturer for oil changing, and is changed back to the original use location after passing the detection. The replacement of the transformer will cause power outage and affect office, production, and life electricity use. Moreover, the 10kV high-voltage side power outage needs to be reported to the power supply department in advance, and the corresponding procedures need to be coordinated and handled. Meanwhile, the transformer needs to be disassembled and transported during construction, which requires a large amount of labor and transportation costs. SUMMARY

[0004] The present application aims to provide transformer oil changing equipment to solve the problem of continuous power supply oil changing of 10kV oil-immersed transformer. The present application can realize continuous power supply oil changing of transformer at the original use location through gas and insulation oil exchange of coaxial pipe, which can continuously power the user, reduce the oil changing construction cost, reduce the handling of corresponding high-voltage power-off procedures, save labor costs, and shorten the construction time.

[0005] To achieve the above-mentioned purpose, on the one hand, the present application provides a transformer oil changing equipment, which comprises a double-channel pipe, one end of the double-channel pipe is provided with a flexible elbow pipe, the outer side of the double-channel pipe is provided with a stretching structure connected with the flexible elbow pipe, and the end of the double-channel pipe away from the flexible elbow pipe is provided with a pressurized gas channel and an oil discharge port.

[0006] Preferably, the double-channel pipe of the present application is a coaxial pipe. The flexible elbow pipe of the present application is composed of a serpentine elbow pipe with a flexible insulating material outside, and the bending angle of the flexible elbow pipe is less than or equal to 90°.

[0007] Preferably, the stretching structure of the present application comprises a first stretching cylinder, a second stretching cylinder, and a rope, and the driving ends of the first stretching cylinder and the second stretching cylinder are connected to the inside of the end of the flexible elbow pipe through the rope.

[0008] Further preferably, the rope of the application is a flexible steel rope. The flexible steel rope is fastened to the inside of the flexible elbow end by a connector, and the connector is made of insulating material, one end of the connector is connected to the coaxial tube, and the other end of the connector is movably connected to the flexible steel rope.

[0009] Preferably, the oil discharge port of the application is provided with a conversion head, and the outside of the conversion head is connected to the oil injection interface and the oil extraction interface through the positive pressure connection pipe and the negative pressure connection pipe respectively, and the oil injection interface or the oil extraction interface is connected to the oil pump for oil injection or oil discharge.

[0010] The transformer oil changing device of the application further comprises a transformer load monitoring module. When the oil is changed under voltage, the gas heat dissipation capacity is lower than that of the oil, and the transformer load monitoring module is used to monitor that the load on the oil-immersed transformer outlet cabinet is within the range that can be borne by the nitrogen heat dissipation and pressure resistance.

[0011] Preferably, the coaxial tube of the application is provided with an external manifold, and the external manifold is provided with a sealing structure. The sealing structure is preferably provided with a tracheal interface structure with a one-way control valve. The tracheal interface with the one-way control valve is connected to a compressed air or compressed nitrogen supply device. The one-way control valve can select a one-way valve in the gas flow one-way flow control component.

[0012] The transformer oil changing device of the application further comprises an endoscope. The endoscope and the external manifold are adaptively arranged. The sealing structure between the endoscope and the external manifold enables the endoscope to be stably fixed in the external manifold, and prevents oil and gas leakage. The coaxial tube is preferably a polytetrafluoroethylene tube. The polytetrafluoroethylene tube is provided with a scale outside, which is used to confirm that the insertion depth is unchanged after the endoscope is taken out.

[0013] In another aspect, the application further provides a transformer oil changing method. The method uses the device described above, and comprises an oil discharging link and an oil injecting link.

[0014] The oil discharging link comprises:

[0015] (1) connecting the transformer load monitoring module to the transformer outlet cabinet for power detection. After the transformer load detection is controlled, one end of the coaxial tube with the flexible elbow is inserted into the inside of the transformer tank. The flexible elbow is bent downward to the bottom of the transformer through the rope of the stretching structure.

[0016] (2) nitrogen is filled through the external manifold to control the oil discharging pressure. Oil is pumped from the oil extraction interface by the oil pump. The discharged oil is uniformly collected and measured in volume.

[0017] The oil injecting link comprises:

[0018] (1) For the transformer of emptying oil, the flexible elbow is bent upward by the rope of the stretching structure, the coaxial tube with scale and endoscope is inserted into the transformer, the image is confirmed by visual image to confirm that the flexible elbow is inserted into the top of the transformer tank and the original transformer oil is emptied, the insertion length is recorded, and the endoscope is taken out;

[0019] (2) The coaxial tube is inserted into the same length, the oil injection is started, the oil injection is stopped when the total amount of oil injection is the same as the oil volume, or the oil injection is stopped when the transformer insulation oil level scale is adjusted to the normal liquid level, the coaxial tube is removed, the oil discharge port is blocked, and the oil replacement is completed.

[0020] Preferably, the angle of the flexible elbow bending upward and downward in the present application is 90 degrees;

[0021] Preferably, the pressure of the nitrogen filled in the oil discharge link is controlled at 25 kilopascals; the transformer of emptying oil is vacuumized to-30 kilopascals; when the transformer is injected with oil, the oil injection pressure is controlled at 0.5-0.8 megapascals by frequency conversion constant pressure, the exhaust pressure is greater than 25 kilopascals; and the negative pressure is extracted to-25 kilopascals after the oil injection is stopped.

[0022] In the present application, the pressure and flow monitoring and control of the oil and gas two-way are adopted by the first monitoring assembly and the second monitoring assembly.

[0023] Further preferably, the negative pressure extraction adopts a vacuum pump, the oil extraction and injection adopts an oil pump, the nitrogen addition adopts a compressed nitrogen gas source, an oil replacement equipment shell is further arranged outside the oil pump, a display is arranged outside the oil replacement equipment shell, a control assembly is integrated inside the display, and the control assembly is electrically connected with the oil pump, the first stretching cylinder, the first monitoring assembly, the second monitoring assembly and the second stretching cylinder.

[0024] Specifically, the first monitoring assembly and the second monitoring assembly both include a pressure sensor and a flow sensor.

[0025] Further preferably, the display, the vacuum pump, the oil pump, the first stretching cylinder, the first monitoring assembly, the second monitoring assembly and the second stretching cylinder are respectively electrically connected with an external power source.

[0026] In a third aspect, the present application further provides a transformer with uninterrupted oil replacement, wherein an oil outlet is arranged on the transformer shell, a detachable transformer oil replacement equipment or a sealing plug is arranged on the oil outlet, and a sealing clamping structure is arranged between the oil outlet and the detachable transformer oil replacement equipment.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) In the oil outlet at the bottom of the transformer shell, the coaxial tube oil-gas two-way separation mode is adopted to discharge and inject oil. When the oil is discharged from the bottom of the transformer shell, the flexible elbow of the coaxial tube is at the bottom of the transformer. Nitrogen is filled at the same time to balance the internal pressure of the transformer, and the oil can be completely discharged.

[0029] (2) When the oil is injected into the transformer shell, the coaxial tube is at the top of the transformer shell. The gas in the transformer can be emptied and the oil can be filled.

[0030] (3) When discharging and injecting oil, the internal pressure of the transformer shell is controlled, which can effectively prevent the transformer shell from being damaged by excessive positive and negative pressure.

[0031] (4) During the oil change process, the transformer oil and inert gas nitrogen can ensure the insulation capacity, and at the same time, the poor gas heat dissipation capacity can be solved by reducing the load of the oil-immersed transformer to solve the safety hidden danger.

[0032] (5) The transformer load monitoring module is used to detect the power on the transformer outlet cabinet. When the power is too large, it can be limited early to reduce the external load and improve the safety of the oil change process. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of the present application;

[0034] Figure 2 It is a schematic diagram of the coaxial tube structure of the present application;

[0035] Figure 3 It is a schematic diagram of the upward bending structure of the coaxial tube of the present application;

[0036] Figure 4 It is a schematic diagram of the downward bending structure of the coaxial tube of the present application;

[0037] Figure 5 It is a schematic diagram of the connection structure of the coaxial tube and the endoscope of the present application;

[0038] In the figure: 1 - transformer shell, 2 - oil outlet, 3 - oil change equipment shell, 4 - display, 5 - oil pump, 6 - coaxial tube, 7 - oil injection interface, 8 - oil extraction interface, 9 - positive pressure connection pipe, 10 - negative pressure connection pipe, 11 - conversion head, 12 - first stretching cylinder, 13 - external manifold, 14 - flexible elbow, 15 - first monitoring component, 16 - second monitoring component, 17 - air pipe interface with one-way control valve, 18 - second stretching cylinder, 19 - flexible steel cable, 20 - connecting piece, 21 - endoscope, 22 - oil discharging and injecting port. DETAILED DESCRIPTION

[0039] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0040] Please refer to Figures 1-5 The present application provides a technical solution:

[0041] The present application provides a transformer oil replacement equipment, the equipment includes a double-channel pipe, one end of the double-channel pipe is provided with a flexible elbow 14, a stretching structure connected with the flexible elbow 14 is arranged outside the double-channel pipe, and the end of the double-channel pipe away from the flexible elbow 14 is provided with a pressurized gas channel.

[0042] The present application also provides a transformer oil replacement method, the method includes an oil discharge link and an oil injection link.

[0043] The oil discharge link includes:

[0044] (1) connecting a transformer load monitoring module to a transformer outlet cabinet for power detection, after the transformer load detection is controlled, inserting one end of the coaxial pipe 6 with the flexible elbow 14 into the transformer box, and bending the flexible elbow downward through the rope of the stretching structure.

[0045] (2) inserting an endoscope into the bottom of the transformer through an external manifold, filling nitrogen gas through the coaxial pipe 6, controlling the oil discharge pressure, and collecting and measuring the discharged oil.

[0046] The oil injection link includes:

[0047] (1) for the transformer with empty oil, bending the flexible elbow 14 upward through the rope of the stretching structure, inserting the coaxial pipe 6 with a scale and an endoscope 21 into the transformer, visually inserting the image into the top of the transformer box and confirming that the transformer oil is empty, recording the insertion length, and removing the endoscope.

[0048] (2) confirming that the coaxial pipe 6 is inserted to the same length, vacuumizing to-30 kilopascals, and monitoring and controlling the pressure and flow of the oil and gas two-way;

[0049] (3) stopping oil injection when the total oil injection volume is the same as the oil discharge volume, or adjusting to the normal liquid level according to the transformer insulating oil liquid level scale to stop, maintaining the safety pressure to the transformer filled with oil; after stopping oil injection, vacuumizing to-25 kilopascals, removing the coaxial pipe 6, plugging the oil discharge port, and completing the oil replacement.

[0050] In a third aspect, the application further provides a transformer for oil change without power interruption, wherein the transformer housing 1 is provided with an oil outlet 2, the oil outlet 2 is provided with a detachable transformer oil change device or a sealing plug, and a sealing clamping structure is arranged between the oil outlet and the detachable transformer oil change device.

[0051] Embodiment 1

[0052] During the oil change of the 10kV grade transformer without power interruption, the transformer load monitoring module is connected to the transformer outlet cabinet for power detection. The coaxial tube 6 with the oil-gas two-way separation structure is used for oil change in this embodiment, the outer diameter of the outer tube of the coaxial tube 6 is 10-50mm, the coaxial tube 6 is connected with a flexible elbow pipe 14 in front, the flexible elbow pipe 14 is a serpentine elbow pipe with a flexible insulating material outside, and in use, the flexible elbow pipe 14 is inserted into the transformer housing 1 through the oil outlet 2 at the bottom of the transformer housing 1, and the flexible elbow pipe 14 can be bent 90 degrees up and down through the cooperation of the first stretching cylinder 12 and the second stretching cylinder 18, the flexible steel cable 19 and the connecting piece 20.

[0053] The coaxial tube 6 is provided with an external manifold 13 interface, the end of the external manifold 13 is provided with a gas pipe interface 17 with a one-way control valve, and the internal manifold 13 is further provided with a endoscope 21; the coaxial tube 6 is provided with a length scale on the surface, and the outer sleeve material of the endoscope 21 is polytetrafluoroethylene, which has good insulation, corrosion resistance, high temperature resistance and flexibility.

[0054] When the transformer is drained, the flexible steel cable 19 of the second stretching cylinder 12 bends the flexible elbow pipe 14 downward to maximize the drainage of the bottom oil, fills nitrogen into the transformer housing 1, controls the oil drainage under the pressure of 25kPa in the transformer housing 1, and collects the drained oil to measure the volume, which provides a reference for the amount of oil injection.

[0055] When the transformer housing 1 is emptied, the flexible elbow pipe 14 of the coaxial tube 6 in the transformer housing 1 is bent 90 degrees upward under the cooperation of the second stretching cylinder 18, the flexible steel cable 19 and the connecting piece 20. The endoscope 21 is inserted into the external manifold 13 of the coaxial tube 6, the visual image is inserted into the coaxial tube 6 to the top of the transformer housing 1, and it is confirmed that the oil has been drained. The insertion length is recorded, the endoscope 21 is taken out, the coaxial tube 6 is inserted into the same length, and the vacuum pump is used to vacuum to-30kPa. The first monitoring assembly 15 and the second monitoring assembly 16 on the outside of the coaxial tube 6 are used to monitor the pressure and flow of the oil-gas two-way in real time.

[0056] When the transformer shell 1 is injected, the injection pressure frequency constant pressure control is 0.5-0.8 MPa, when the exhaust pressure is greater than 25 kPa, the negative pressure can be extracted to accelerate the exhaust, the total amount of injection can be stopped when the oil injection and the oil discharge volume are the same through the metering control, the oil injection can also be stopped according to the transformer insulation oil level scale to adjust to the normal liquid level, and the safety pressure is maintained until the transformer is filled with oil. Finally, the negative pressure is extracted to 25 kPa, the coaxial tube 6 is removed, the oil discharge port is blocked, and the oil change is completed.

[0057] Example 2

[0058] Different from example 1, the double-channel pipe of the embodiment is a polytetrafluoroethylene double-hole pipe, and the stretching structure adopts the brake system structure of a bicycle or an electric vehicle, including a handle and a brake wire, the brake wire is connected with the polytetrafluoroethylene double-hole pipe through a nylon screw rod nut close to the side of the transformer shell.

[0059] The upper and lower bending angles of the flexible elbow pipe in the embodiment are less than 90°.

[0060] The transformer load monitoring module of the embodiment is a current meter and a current limiting air switch arranged in the transformer outlet cabinet, when the transformer output current reaches a certain value, the current limiting air switch of part of the output circuit is disconnected, the load of the whole transformer is reduced, the load of the transformer does not exceed the range that can be borne by the nitrogen heat dissipation and pressure resistance, and the safety of the oil change process is ensured.

[0061] The end of the polytetrafluoroethylene double-hole pipe in the embodiment is provided with an oil discharge port 22, the oil discharge port 22 is provided with a conversion head 11, the outer side of the conversion head 11 is connected to an oil injection interface 7 and an oil extraction interface 8 through a positive pressure connecting pipe 9 and a negative pressure connecting pipe 10 respectively, the oil injection interface 7 and the oil extraction interface 8 are connected to an oil pump 5, and the oil injection and oil discharge are controlled by using the oil pump 5. An external manifold 13 is connected with a compressed air or compressed nitrogen providing device. The oil discharge port 22 is communicated with one hole of the polytetrafluoroethylene double-hole pipe, and the external manifold 13 is communicated with the other hole of the polytetrafluoroethylene double-hole pipe.

[0062] Sealing rings are arranged between the endoscope and the external manifold 13 in the embodiment, so that the endoscope can be stably fixed in the external manifold 13, and oil and gas leakage is avoided, the endoscope 21 is selected to be a polytetrafluoroethylene pipe sleeve, and the polytetrafluoroethylene double-hole pipe and the endoscope 21 are externally marked with scales.

[0063] In the embodiment, the pressure and flow monitoring and control of the oil and gas two-way are realized by using a first monitoring component 15 and a second monitoring component 16, the first monitoring component 15 and the second monitoring component 16 both include pressure sensors and flow sensors, when the pressure is detected, the pressure on the pipeline and the pressure in the transformer shell are calibrated in advance, and the pressure in the transformer shell can be known according to the pressure on the polytetrafluoroethylene double-hole pipe.

[0064] In this embodiment, the vacuum pump is used for extracting negative pressure, the oil pump 5 is used for discharging and injecting oil, and the compressed air or nitrogen is used for adding compressed air or nitrogen. The oil pump 5 is further provided with an oil changing device shell 3 outside, and the display 4 is provided outside the oil changing device shell 3. The control assembly is integrated inside the display 4, and the control assembly is electrically connected with the oil pump 5, the first stretching cylinder 12, the first monitoring assembly 15, the second monitoring assembly 16 and the second stretching cylinder 18. The display 4, the oil pump 5, the first stretching cylinder 12 and the second stretching cylinder 18 can be controlled by the control assembly. The values of the first monitoring assembly 15 and the second monitoring assembly 16 can be displayed by the control assembly on the display 5. The display 4, the oil pump 5, the first stretching cylinder 12, the first monitoring assembly 15, the second monitoring assembly 16 and the second stretching cylinder 18 are respectively electrically connected with an external power supply.

[0065] Embodiment 3

[0066] In this embodiment, the flexible steel cable 19 is fixedly connected with the inner end of the coaxial pipe 6 near the transformer shell side through the connecting piece 20, and the connecting piece 20 is made of insulating material. One end of the connecting piece 20 is connected with the coaxial pipe 6, and the other end of the connecting piece 20 is movably connected with the flexible steel cable 19.

[0067] Embodiment 4

[0068] In this embodiment, a transformer with uninterrupted oil changing is provided. Different from the embodiment 1, the transformer shell is provided with an oil outlet 2, and the oil outlet 2 is provided with a detachable transformer oil changing device or a sealing plug. The sealing plug ensures that the transformer insulation oil will not leak after the transformer oil changing is completed. The sealing clamping structure includes a conical sealing ring and a screw cap. The conical sealing ring is fixedly sleeved outside the coaxial pipe 6, and the screw cap is provided with threads matched with the oil outlet 2. The screw cap is movably sleeved outside the coaxial pipe 6. The conical sealing ring is inserted into the oil outlet 2, and the coaxial pipe 6 and the conical sealing ring are pressed into the oil outlet 2 together by rotating the screw cap on the oil outlet 2. The sealing clamping structure prevents the oil or gas from leaking during the oil discharging and injecting process, and ensures the sealing property during the transmission process.

[0069] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein and are part of the invention. Any reference signs in the claims should not be construed as limiting the scope of the claims.

[0070] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent substitutions or changes according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A transformer oil changing device, characterized in that: The tube includes a dual-channel pipe, one end of which is provided with a flexible bend, and a tension structure connected to the flexible bend is provided on the outside of the dual-channel pipe. The end of the dual-channel pipe away from the flexible bend is provided with a pressurized gas channel and an oil discharge port. The dual-channel tube is a coaxial tube; The tensioning structure includes a first tensioning cylinder, a second tensioning cylinder, and a flexible steel cable. The drive ends of the first tensioning cylinder and the second tensioning cylinder are respectively connected to the inside of the end of the flexible bend via the flexible steel cable. The oil inlet / outlet is equipped with a converter, which is connected to the oil inlet and the oil outlet via a positive pressure connecting pipe and a negative pressure connecting pipe, respectively. It also includes a transformer load monitoring module; An external manifold is provided on the pressurized gas channel, and a sealing structure is provided inside the external manifold; When draining oil from a transformer, the flexible steel cable of the first tension cylinder causes the flexible bend to bend downwards, maximizing the drainage of the bottom oil. Nitrogen gas is then injected into the transformer casing to control the oil drainage under the internal air pressure. The drained oil is collected and measured in a unified manner. When the oil inside the transformer housing is drained, the flexible bend of the coaxial tube, which extends into the transformer housing, bends upward with the help of the second tension cylinder, flexible steel cable, and connecting parts.

2. The transformer oil changing equipment according to claim 1, characterized in that: It also includes an endoscope, which is adapted to an external manifold.

3. The oil changing method of a transformer oil changing device according to any one of claims 1-2, characterized in that, The method includes an oil draining stage and an oil injection stage; the oil draining stage includes: (1) Connect the transformer load monitoring module to the transformer outgoing cabinet for power detection. After the transformer load detection is controlled, insert one end of the coaxial tube with the flexible bend into the transformer box. The flexible steel cable of the tensioning structure makes the flexible bend bend downward and penetrate into the bottom of the transformer. (2) Nitrogen gas is introduced through an external manifold to control the oil discharge pressure. Oil is pumped from the oil extraction port using an oil pump, and the discharged oil is collected and measured in a unified manner. The oil injection process includes: (1) For a transformer that has drained oil, the flexible steel cable of the tensioning structure is used to bend the flexible bend, and the coaxial tube with an endoscope in the external manifold is inserted into the transformer. Visually confirm that the flexible bend is inserted to the top of the transformer tank and that the original transformer oil has been drained. Record the insertion length and remove the endoscope. (2) Insert the coaxial tube to the same length and start filling with oil. Stop filling with oil when the total amount of oil filled is the same as the volume of oil drained, or adjust the transformer insulating oil level to the normal level and stop filling with oil. Remove the coaxial tube, seal the drain port, and the oil change is complete.

4. The transformer oil change method according to claim 3, characterized in that: The flexible bend is bent upwards and downwards at angles of 90 degrees. The pressure of nitrogen gas introduced during the oil drainage process is controlled at 25 kPa; the transformer for draining oil is evacuated to -30 kPa. When filling the transformer with oil, the filling pressure is controlled by frequency converter constant pressure at 0.5~0.8 MPa, and the exhaust pressure is >25 kPa; after stopping the filling, the negative pressure is drawn down to -25 kPa.

5. A transformer that allows for uninterrupted oil replacement, characterized in that: The transformer housing is provided with an oil outlet, and the oil outlet is provided with a detachable transformer oil changing device or a sealing plug; a sealing snap-fit ​​structure is provided between the oil outlet and the detachable transformer oil changing device; the detachable transformer oil changing device is the transformer oil changing device according to any one of claims 1-2.

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