Connection changing device and method for a transformer

Abstract

The invention relates to a connection change device and method for a transformer. A connection changing apparatus for a transformer includes: a plurality of connection points, each connection point being connected to a different coil tap of a plurality of coil taps of a high voltage side winding of the transformer; a plurality of voltage-sharing balls, each voltage-sharing ball being configured to accommodate one of the plurality of connection nodes and to be electrically connected to the corresponding connection point so as to homogenize an electric field around the corresponding connection point; each connecting line is configured to be connected with two connecting points in the multiple connecting points through the corresponding voltage-sharing ball in the multiple voltage-sharing balls, and the voltage capable of being borne by the high-voltage side winding of the transformer is changed by changing the connecting mode of the more than one connecting line and the multiple connecting points; and the insulating oil is configured to immerse each connecting line and the plurality of voltage-sharing balls so as to carry out insulating packaging on each connecting line and the plurality of voltage-sharing balls. The cost of the connection change of the transformer is thus significantly reduced.

Description

Technical Field

[0001] The present invention relates to the field of transformers, and more particularly, to a connection changing device and method for a transformer. Background Art

[0002] Transformers are typically used to convert high-voltage electricity in the power grid into voltages suitable for distribution to consumers or use in industrial equipment. When the operating conditions of the power grid change, such as when new loads are connected to the power grid or the topology of the power grid changes, it is necessary to adjust the tap of the high-voltage side winding of the transformer so that the output voltage of the transformer adapts to the new power grid requirements, maintaining the continuity and stability of the power supply.

[0003] In the prior art, a no-load switch is used to adjust the tap of the high-voltage side winding of the transformer, so that the output voltage of the transformer adapts to the new power grid requirements. However, the design and operation requirements of no-load switches are very high. In a high-voltage environment, they usually require special insulation and operating mechanisms, which makes them large in size, heavy in weight and high in cost. Summary of the Invention

[0004] In view of the situation and deficiencies of the prior art, an object of the present invention is to provide a connection changing device and method for a transformer, which sets connection points on each tap of the high-voltage side winding of the transformer, and uses equalizing spheres to cover and accommodate the connection points to equalize the electric field around the connection points. By connecting different connection points via the equalizing spheres in different ways with connection lines, the tap of the high-voltage side winding coil of the transformer is adjusted, so that the output voltage of the transformer adapts to the new power grid requirements. In this way, the cost of changing the connection of the transformer is significantly reduced. In addition, since the connection points are arranged inside the equalizing spheres, no additional insulation treatment is required when adjusting the connection of the transformer, which simplifies the on-site operation, improves the work efficiency, and at the same time ensures the safety and reliability of the electrical performance.

[0005] According to an embodiment of the present invention, there is provided a connection changing device for a transformer. The transformer includes a high-voltage side winding. The connection changing device for the transformer includes: a plurality of connection points, each connection point being connected to a different coil tap among a plurality of coil taps of the high-voltage side winding of the transformer; a plurality of equalizing spheres, each equalizing sphere being configured to accommodate one connection node among the plurality of connection nodes and being electrically connected to the corresponding connection point to equalize the electric field around the corresponding connection point; more than one connection line, each connection line being configured to connect two connection points among the plurality of connection points via the corresponding equalizing sphere among the plurality of equalizing spheres, wherein the voltage that can be borne on the high-voltage side winding of the transformer is changed by changing the connection mode of more than one connection line with the plurality of connection points; and insulating oil, which is configured to immerse each connection line and the plurality of equalizing spheres to perform insulation encapsulation on each connection line and the plurality of equalizing spheres.

[0006] The connection change device for a transformer according to an embodiment of the present invention significantly reduces the cost of connection change of the transformer. In addition, since the connection points are arranged inside the grading spheres, no additional insulation treatment is required when adjusting the connections of the transformer, which simplifies on-site operations, improves work efficiency, and at the same time ensures the safety and reliability of electrical performance.

[0007] The connection change device for a transformer according to an embodiment of the present invention further includes: a cavity, which is arranged at a position on the transformer higher than the tank cover of the transformer, wherein a plurality of connection points, a plurality of grading spheres, more than one connecting wire, and insulating oil are accommodated in the cavity.

[0008] The design of arranging the connection change device for a transformer independently of the transformer tank and at a position higher than the tank cover of the transformer enables, when changing the connections of the transformer, only the insulating oil in the cavity of the connection change device for a transformer to be drained, without draining the insulating oil in the transformer tank, thus simplifying on-site operations and improving work efficiency.

[0009] In the connection change device for a transformer according to an embodiment of the present invention, a plurality of connection points, a plurality of grading spheres, more than one connecting wire, and insulating oil are accommodated in the transformer tank.

[0010] In the above manner, the design of the connection change device for a transformer can be simplified.

[0011] In the connection change device for a transformer according to an embodiment of the present invention, the plurality of connection points include terminal blocks, bolts, welding points or crimping points.

[0012] In the above manner, specific examples of the connection points are provided.

[0013] The connection change device for a transformer according to an embodiment of the present invention further includes: insulating paper wrapped around the outside of each connecting wire.

[0014] In the above manner, the electrical insulation between the connecting wire and other components is ensured, preventing short circuits.

[0015] In a connection change device for a transformer according to an embodiment of the present invention, each connection line is configured to connect two connection points among a plurality of connection points via a corresponding grading sphere among a plurality of grading spheres in a predetermined manner, and the predetermined manner includes one of the following manners: connecting the start end and the end of a coil of the high-voltage side winding of the transformer to the two ends of a connection line respectively; connecting at least two coils of the high-voltage side winding of the transformer in parallel; connecting at least two coils of the high-voltage side winding of the transformer in series; connecting at least two coils of the high-voltage side winding of the transformer in parallel and then connecting in series with another coil; and connecting at least two coils of the high-voltage side winding of the transformer in series and then connecting in parallel with another coil.

[0016] By the above manner, specific examples of changing the connection manner of the transformer are provided.

[0017] In a connection change device for a transformer according to an embodiment of the present invention, the cavity is in communication with the oil tank of the transformer.

[0018] By the above manner, it is convenient for the connection points of the connection change device for the transformer to be connected to the coil taps of the high-voltage side winding of the transformer and for the connection change device for the transformer to share the insulating oil in the transformer.

[0019] According to another embodiment of the present invention, a connection change method for a transformer is provided. The method uses a connection change device for a transformer to change the connection of the transformer, and the transformer includes a high-voltage side winding. Among them, the connection change device for a transformer includes: a plurality of connection points, each connection point is connected to each coil tap among a plurality of coil taps of the high-voltage side winding of the transformer; a plurality of grading spheres, each grading sphere is configured to accommodate one connection node among a plurality of connection nodes and is electrically connected to the corresponding connection point to make the electric field around the corresponding connection point uniform; more than one connection line, each connection line is configured to connect two connection points among a plurality of connection points via a corresponding grading sphere among a plurality of grading spheres, wherein the voltage that can be borne on the high-voltage side winding of the transformer is changed by changing the connection manner of more than one connection line and a plurality of connection points; and insulating oil, which is configured to immerse each connection line and a plurality of grading spheres to perform insulation encapsulation on each connection line and a plurality of grading spheres. When it is necessary to change the connection of the transformer, the method includes: discharging at least a part of the insulating oil in the connection change device for the transformer until the plurality of grading spheres and at least more than one connection line are not immersed in the insulating oil; removing all existing connection lines from the plurality of grading spheres; connecting new connection lines to the connection points in the corresponding grading spheres via the corresponding grading spheres among the plurality of grading spheres in a predetermined manner; and injecting insulating oil into the connection change device for the transformer until the plurality of grading spheres and the new connection lines are immersed in the insulating oil.

[0020] The method for changing the connection of a transformer according to an embodiment of the present invention significantly reduces the cost of changing the connection of the transformer. In addition, since the connection points are arranged inside the grading spheres, no additional insulation treatment is required when adjusting the connection of the transformer, which simplifies on-site operations, improves work efficiency, and at the same time ensures the safety and reliability of the electrical performance.

[0021] In another embodiment of the method for changing the connection of a transformer according to the present invention, the predetermined manner includes one of the following manners: connecting the head end and the tail end of one coil of the high-voltage side winding of the transformer to both ends of a connection wire respectively; connecting at least two coils of the high-voltage side winding of the transformer in parallel; connecting at least two coils of the high-voltage side winding of the transformer in series; connecting at least two coils of the high-voltage side winding of the transformer in parallel and then connecting them in series with another coil; and connecting at least two coils of the high-voltage side winding of the transformer in series and then connecting them in parallel with another coil.

[0022] By the above manner, specific examples of changing the connection manner are provided. Description of the Drawings

[0023] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figures 1A to 1C A schematic diagram of a device for changing the connection of a transformer according to an embodiment of the present invention is shown, wherein, Figure 1A is a front view of the device for changing the connection of a transformer, Figure 1B is a top view of the device for changing the connection of a transformer, Figure 1C is a side view of the device for changing the connection of a transformer.

[0025] Figures 2A to 2B Another connection manner of the device for changing the connection of a transformer according to an embodiment of the present invention is shown, wherein, Figure 2A is a top view of the device for changing the connection of a transformer, Figure 2B is a side view of the device for changing the connection of a transformer.

[0026] Figure 3 A flowchart of a method for changing the connection of a transformer according to another embodiment of the present invention is shown.

[0027] Wherein, the reference numerals are as follows:

[0028] 1: Device for changing the connection of a transformer

[0029] 12: Multiple grading spheres

[0030] 14: More than one connecting wire

[0031] 16: Insulating oil

[0032] 121: First grading ball

[0033] 122: Second grading ball

[0034] 123: Third grading ball

[0035] 124: Fourth grading ball

[0036] 18: Cavity

[0037] 181: Cavity wall

[0038] 183: Cavity cover

[0039] S1 - S4: Steps Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The present invention provides a connection changing device for a transformer. Figures 1A to 1C A schematic diagram of a connection changing device for a transformer according to an embodiment of the present invention is shown in Figure 2A and Figure 2B Another connection manner of the connection changing device for a transformer according to an embodiment of the present invention is shown in. Next, with reference to Figures 1A to 1C and Figures 2A to 2B , the connection changing device for a transformer according to an embodiment of the present invention will be described.

[0042] As Figures 1A to 1C shown, the connection changing device 1 for a transformer includes a plurality of connection points, a plurality of grading balls 12, more than one connecting wire 14, and insulating oil 16.

[0043] In Figures 1A to 1C , since the plurality of connection points are respectively wrapped and accommodated in the plurality of grading balls 12, the plurality of connection points are not shown in Figures 1A to 1C . The positions where the plurality of grading balls 12 are located can be regarded as the positions of the plurality of connection points.

[0044] Each of the plurality of connection points is connected to a different coil tap of the plurality of coil taps of the high-voltage side winding of the transformer. That is, each coil tap of the high-voltage side winding of the transformer is connected to a connection point, which may include a terminal, a bolt, a welding point or a crimping point. The terminal provides a reliable interface between electrical equipment, circuit boards or cables to fix the wires, thereby connecting or disconnecting the current path. The terminal may include a screw terminal, a spring terminal, a welding terminal, a crimping terminal, a plug-in terminal, etc. A welding point refers to a part in an electronic circuit or electrical connection where a wire, a component pin or other conductive material is firmly bonded to a connector through a welding process. A crimping point refers to an electrical connection between two conductors formed by pressure rather than welding or bolting, and this connection method is widely used in high-voltage power systems and occasions that require frequent maintenance or disassembly.

[0045] exist Figures 1A to 1C 4 coil taps of the high voltage side winding of the transformer are shown as an example.

[0046] Each of the multiple voltage-equalizing balls 12 is configured to accommodate one of the multiple connection points and is electrically connected to the corresponding connection point, so that the electric field around the corresponding connection point is uniform. The voltage-equalizing ball is a component used to improve the electric field distribution in high-voltage equipment. For example, when the connection point is a bolt, the electric field strength at its sharp edge will increase significantly, which may cause partial discharge or electrical breakdown. By covering and accommodating the bolt with the voltage-equalizing ball, the electric field around the bolt can be made more uniform, reducing these local effects.

[0047] exist Figures 1A to 1C In the figure, it is shown that the plurality of equalizing balls 12 include four equalizing balls, namely, a first equalizing ball 121, a second equalizing ball 122, a third equalizing ball 123 and a fourth equalizing ball 124. A connection point connected to a coil connector of a high-voltage side winding of a transformer is contained in each of the first equalizing ball 121, the second equalizing ball 122, the third equalizing ball 123 and the fourth equalizing ball 124. However, the present invention is not limited thereto, and the number of equalizing balls can be set according to the number of coil connectors of the high-voltage side winding of the transformer.

[0048] Each connection line 14 is configured to connect two connection points among the plurality of connection points via corresponding pressure equalizing balls among the plurality of pressure equalizing balls 12 in a predetermined manner. Figures 1A to 1COne connecting wire 14 is shown, with the first grading sphere 121 covering and accommodating the connection point connected to the head end of the first coil of the high-voltage coil side winding of the transformer, the second grading sphere 122 covering and accommodating the connection point connected to the tail end of this first coil, the third grading sphere 123 covering and accommodating the connection point connected to the head end of the second coil of the high-voltage coil side winding of the transformer, and the fourth grading sphere 124 covering and accommodating the connection point connected to the tail end of this second coil. Both ends of the connecting wire 14 are respectively connected via the first grading sphere 121 and the second grading sphere 122 to the corresponding connection points within the first grading sphere 121 and the second grading sphere 122, and then connected to the head end and the tail end of the first coil of the high-voltage coil side winding of the transformer, thereby connecting the first coil of the high-voltage coil side winding of the transformer to the power grid.

[0049] The voltage that can be withstood on the high-voltage side winding of the transformer is changed by changing the connection mode of more than one connecting wire to multiple connection points.

[0050] Although in Figures 1A to 1C an example is shown where one connecting wire 14 is connected via the first grading sphere 121 and the second grading sphere 122 to the head end and the tail end of the first coil of the high-voltage coil side winding of the transformer, the present invention is not limited thereto.

[0051] As Figure 2A and Figure 2B shown, two connecting wires 14 are shown. Both ends of the first connecting wire 14 are connected via the first grading sphere 121 and the third grading sphere 123 to the head end of the first coil and the head end of the second coil, and both ends of the second connecting wire 14 are connected via the second grading sphere 122 and the fourth grading sphere 124 to the tail end of the first coil and the tail end of the second coil, so that the first coil and the second coil are connected in parallel. In addition to Figures 1A to 1C and Figures 2A to 2B the connection modes shown, the connecting wire 14 can also connect two connection points among multiple connection points via the corresponding grading spheres among multiple grading spheres in a manner including but not limited to the following: connecting at least two coils of the high-voltage side winding of the transformer in series; connecting at least two coils of the high-voltage side winding of the transformer in parallel and then connecting in series with another coil; and connecting at least two coils of the high-voltage side winding of the transformer in series and then connecting in parallel with another coil. The specific connection mode can be set as required.

[0052] The insulating oil 16 is configured to submerge each connecting wire 14 and multiple grading spheres 12 to perform insulation encapsulation on each connecting wire 14 and multiple grading spheres 12. The insulating oil usually plays the roles of insulation and cooling in the transformer. Common insulating oils include mineral oil, vegetable oil, synthetic oil, fluorinated liquid, nano oil, etc.

[0053] As Figures 1A to 1CAs shown, the connection changing device 1 for a transformer may further include a cavity 18, which includes a cavity wall 181 and a cavity cover 183. The cavity cover 183 covers above the cavity wall 181 and together with the cavity wall 181 forms an internal space surrounded by the cavity wall 181 and the cavity cover 183. A plurality of connection points, a plurality of grading balls 12, more than one connecting wire 14, and insulating oil 16 are accommodated in this internal space.

[0054] The cavity 18 may be disposed at a position on the transformer higher than the tank cover of the transformer. This design enables, when changing the connection of the transformer, only the insulating oil 16 in the cavity 18 of the connection changing device 1 for the transformer to be drained, without the need to drain the insulating oil in the transformer tank, thus simplifying on-site operations and improving work efficiency.

[0055] The cavity 18 is in communication with the transformer tank, and the insulating oil 16 in the cavity 18 is the same as the insulating oil in the transformer tank. In this way, it facilitates the connection between the connection points of the connection changing device 1 for the transformer and the coil taps of the high-voltage side winding of the transformer, as well as the sharing of the insulating oil between the connection changing device 1 for the transformer and the transformer tank.

[0056] Optionally, a plurality of connection points, a plurality of grading balls 12, more than one connecting wire 14, and insulating oil 16 may be accommodated in the transformer tank. That is, the transformer tank is used as the cavity of the connection changing device 1 for the transformer, which can relatively simplify the design of the connection changing device 1 for the transformer.

[0057] The connection changing device 1 for a transformer may further include insulating paper wrapped around the outside of each connecting wire 14, which ensures electrical insulation between the connecting wire and other components and prevents short circuits.

[0058] The connection changing device for a transformer according to an embodiment of the present invention significantly reduces the cost of changing the connection of the transformer. In addition, since the connection points are arranged inside the grading balls, no additional insulation treatment is required when adjusting the connection of the transformer, which simplifies on-site operations, improves work efficiency, and at the same time ensures the safety and reliability of electrical performance.

[0059] According to another embodiment of the present invention, there is provided a method for changing the connection of a transformer, which uses the connection changing device 1 for a transformer described above in combination Figures 1A to 1C and Figures 2A to 2B to change the connection of the transformer. For clarity, the structural details related to the above-described connection changing device for a transformer will not be repeated in the following description, that is, the above description of the connection changing device for a transformer equally applies to the description of the method for changing the connection of a transformer below.

[0060] Figure 3 The figure shows a flowchart of a connection change method for a transformer according to another embodiment of the present invention.

[0061] As Figure 3 shown, when it is necessary to change the connection of the transformer, the connection change method for the transformer according to another embodiment of the present invention includes steps S1 to S4.

[0062] In step S1, at least a part of the insulating oil in the connection change device 1 for the transformer is drained until the plurality of grading balls 12 and at least one or more connecting wires 14 are not immersed in the insulating oil 16.

[0063] Combined Figures 1A to 1C and Figures 2A to 2B , specifically, a part of the insulating oil 16 in the cavity 18 of the connection change device 1 for the transformer is drained until the plurality of grading balls 12 and at least one or more connecting wires 14 are exposed. By controlling the oil level of the insulating oil, it can be ensured that in the following steps, the operator can safely contact and adjust the connecting wires.

[0064] In step S2, all the existing connecting wires 14 are removed from the plurality of grading balls 12.

[0065] Specifically, after the oil level of the insulating oil 16 is reduced to such an extent that the plurality of grading balls 12 and at least one or more connecting wires 14 are exposed, all the existing connecting wires 14 can be removed from the plurality of grading balls 12.

[0066] In step S3, the new connecting wires are connected to the connection points in the corresponding grading balls via the corresponding grading balls among the plurality of grading balls in a predetermined manner.

[0067] Specifically, the connection mode of the coils of the high-voltage side winding of the transformer is determined according to the coil requirements of the high-voltage side winding of the transformer to which the transformer is to be connected to the power grid. According to the determined connection mode, the plurality of grading balls are connected with new connecting wires, and then the connection points in the corresponding grading balls are connected, thereby connecting the desired coils of the high-voltage side winding into the power grid.

[0068] In step S4, insulating oil 16 is injected into the connection change device 1 for the transformer until the plurality of grading balls 12 and the new connecting wires are immersed in the insulating oil 16.

[0069] Specifically, after the reconnection of all the connecting wires is completed, the insulating oil 16 is reinjected into the connection change device 1 for the transformer until the plurality of grading balls 12 and the new connecting wires are completely immersed in the insulating oil 16. The reinjection of the insulating oil not only ensures the insulation between the components in the connection change device 1 for the transformer, but also ensures the cooling and protection of the components in the connection change device 1 for the transformer by the insulating oil, guaranteeing the stable operation of the transformer after the connection change.

[0070] The connection change method for the transformer according to the embodiment of the present invention significantly reduces the cost of the connection change of the transformer. In addition, since the connection points are arranged in the grading balls, no additional insulation treatment is required when adjusting the connection of the transformer, which simplifies the on-site operation, improves the work efficiency, and at the same time ensures the safety and reliability of the electrical performance.

[0071] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A connection changing device (1) for a transformer, the transformer comprising a high-voltage side winding, characterized in that, The connection change device (1) for a transformer includes: a plurality of connection points, each connection point being connected to a different coil tap among a plurality of coil taps of the high-voltage side winding of the transformer; a plurality of grading balls (12), each grading ball being configured to accommodate one of the plurality of connection nodes and being electrically connected to the corresponding connection point to equalize the electric field around the corresponding connection point; more than one connecting wire (14), each connecting wire being configured to connect two of the plurality of connection points via a corresponding one of the plurality of grading balls (12), wherein the voltage that can be withstood on the high-voltage side winding of the transformer is changed by changing the connection mode of the more than one connecting wire to the plurality of connection points; and insulating oil (16), being configured to immerse each connecting wire and the plurality of grading balls to perform insulation encapsulation on each connecting wire and the plurality of grading balls.

2. The connection change device (1) for a transformer according to claim 1, characterized in that, Further included is: a cavity (18), provided at a position on the transformer higher than the tank cover of the transformer, wherein the plurality of connection points, the plurality of grading balls (12), the more than one connecting wire (14), and the insulating oil (16) are accommodated in the cavity (18).

3. The connection change device (1) for a transformer according to claim 2, characterized in that the plurality of connection points, the plurality of grading balls (12), the more than one connecting wire (14), and the insulating oil (16) are accommodated in the tank of the transformer.

4. The connection changing device (1) for a transformer according to claim 1 or 2, characterized in that, The plurality of connection points include terminal blocks, bolts, welding points, or crimping points.

5. The connection change device (1) for a transformer according to claim 1 or 2, characterized in that, Further included is: insulating paper coated on the outside of each connecting wire.

6. The connection changing device (1) for a transformer according to claim 1 or 2, characterized in that, Each connecting wire is configured to connect two of the plurality of connection points via a corresponding one of the plurality of grading balls in a predetermined manner, and the predetermined manner includes one of the following manners: connecting the head end and the tail end of a coil of the high-voltage side winding of the transformer to the two ends of a connecting wire respectively; connecting at least two coils of the high-voltage side winding of the transformer in parallel; connecting at least two coils of the high-voltage side winding of the transformer in series; connecting at least two coils of the high-voltage side winding of the transformer in parallel and then connecting in series with another coil; and connecting at least two coils of the high-voltage side winding of the transformer in series and then connecting in parallel with another coil.

7. The connection changing device (1) for a transformer according to claim 2, characterized in that, The cavity (18) communicates with the tank of the transformer.

8. A method for changing the connection of a transformer, the method using a connection changing device (1) for the transformer to change the connection of the transformer, the transformer including a high-voltage side winding, wherein, The connection change device (1) for a transformer includes: a plurality of connection points, each connection point being connected to a different coil tap among a plurality of coil taps of the high-voltage side winding of the transformer; a plurality of voltage equalizing balls (12), each voltage equalizing ball being configured to accommodate one connection node among the plurality of connection nodes and being electrically connected to the corresponding connection point to equalize the electric field around the corresponding connection point; more than one connection line (14), each connection line being configured to connect two connection points among the plurality of connection points via the corresponding voltage equalizing ball among the plurality of voltage equalizing balls, wherein the voltage that can be withstood on the high-voltage side winding of the transformer is changed by changing the connection mode of the more than one connection line with the plurality of connection points; and insulating oil (16), being configured to immerse each connection line and the plurality of voltage equalizing balls to insulate and encapsulate each connection line and the plurality of voltage equalizing balls. When it is necessary to change the connection of the transformer, the method includes: Discharging at least a part of the insulating oil in the connection change device for the transformer until the plurality of voltage equalizing balls and the at least more than one connection line are not immersed in the insulating oil (S1); Removing all existing connection lines from the plurality of voltage equalizing balls (S2); Connecting a new connection line to the connection point in the corresponding voltage equalizing ball via the corresponding voltage equalizing ball among the plurality of voltage equalizing balls in a predetermined manner (S3); and Injecting the insulating oil into the connection change device for the transformer until the plurality of voltage equalizing balls and the new connection line are immersed in the insulating oil (S4).

9. The method according to claim 8, characterized in that The predetermined manner includes one of the following manners: Connecting the head end and the tail end of a coil of the high-voltage side winding of the transformer to the two ends of a connection line respectively; Connecting at least two coils of the high-voltage side winding of the transformer in parallel; Connecting at least two coils of the high-voltage side winding of the transformer in series; Connecting at least two coils of the high-voltage side winding of the transformer in parallel and then connecting them in series with another coil; and Connecting at least two coils of the high-voltage side winding of the transformer in series and then connecting them in parallel with another coil.

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