Transformer maintenance method

Abstract

To provide a transformer maintenance method capable of reducing the time required to temporarily remove a closing member from a connecting pipe.SOLUTION: A disclosed transformer maintenance method includes: a step S1 of cooling an insulating oil L located inside the connecting pipe 30; a step S2 of vacuuming a tank 20; and a step S3 of removing the closing member 40 from the connecting pipe 30 in the state that the insulating oil L located inside the connecting pipe 30 is cooled and the tank 20 is vacuumed.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for maintaining a transformer.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2018-78211 (Patent Document 1) discloses a natural circulation type transformer filled with vegetable oil. The natural circulation type transformer filled with vegetable oil has a structure in which a plurality of transformer bodies are housed in a transformer tank and sealed in a state where vegetable oil as an insulating liquid is injected and impregnated inside. Radiators for cooling are provided on opposite side portions of the transformer tank. The radiator includes communication pipes that communicate with the inside of the transformer tank at two upper and lower locations on the side wall of the transformer tank, and a plurality of heat dissipation plates branched from the communication pipes. The vegetable oil in the transformer tank is cooled by the heat dissipation plates by circulating through the communication pipes and the heat dissipation plates at the two upper and lower locations. Japanese Patent Application Laid-Open No. 61-260503 (Patent Document 2) discloses an oil-filled electrical apparatus using vegetable oil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional transformer, a closing member such as a valve may be provided at the tip of a connecting pipe connected to a tank. And, for maintenance of the transformer, the closing member may be temporarily removed from the connecting pipe. For example, by temporarily removing the closing member from the connecting pipe, it becomes possible to replace a seal member located between the closing member and the connecting pipe. Here, when the closing member is removed from the connecting pipe with the insulating oil filled in the tank, there is a risk that the insulating oil will flow out from the connecting pipe. For this reason, in order to temporarily remove the closing member from the connecting pipe, it was necessary to previously extract the insulating oil from the tank. The work of extracting the insulating oil takes a relatively long time.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a method for maintaining a transformer that can shorten the time required for the work of temporarily removing a closing member from a connecting pipe.

Means for Solving the Problems

[0006] The method for maintaining a transformer according to the present disclosure is a method for maintaining a transformer including a transformer body, a tank, a connecting pipe, and a closing member. The tank houses the transformer body and is filled with insulating oil. The connecting pipe is connected to the outside of the tank and allows the insulating oil filled in the tank to flow in. The closing member is attached to the connecting pipe on the side opposite to the tank when viewed from the connecting pipe. The method for maintaining a transformer according to the present disclosure includes a step of cooling the insulating oil located inside the connecting pipe, a step of evacuating the tank, and a step of removing the closing member from the connecting pipe in a state where the insulating oil located inside the connecting pipe is cooled and the tank is evacuated.

Effects of the Invention

[0007] According to the present disclosure, by cooling the insulating oil located inside the connecting pipe and evacuating the tank, the flow of the insulating oil in the connecting pipe can be suppressed. Therefore, it is possible to suppress the outflow of the insulating oil from the connecting pipe to the outside when the closing member is temporarily removed. Further, the cooling time and the evacuation time are shorter than the time for extracting the insulating oil from the tank. Thus, the time required for the preparation work for temporarily removing the closing member from the connecting pipe can be shortened.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 9

Embodiments for Carrying Out the Invention

[0009] Hereinafter, a method for maintaining a transformer according to an embodiment of the present disclosure will be described with reference to the drawings. In the following description of the embodiment, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated. In this specification, "vacuum" refers to a state within a space filled with a gas at a pressure lower than atmospheric pressure (for example, an inert gas or vaporized insulating oil described later). The degree of vacuum of the "vacuum" is preferably 100 Pa or more and 100 kPa or less.

[0010] First, in the maintenance method of the present disclosure, a transformer in which inspection, repair, maintenance, or replacement of some parts is performed will be described. FIG. 1 is a front view of a transformer according to an embodiment of the present disclosure. FIG. 2 is a plan view of a transformer according to an embodiment of the present disclosure. FIG. 3 is a schematic partial cross-sectional view of the transformer of FIG. 2 viewed from the direction of the arrow III-III. As shown in FIGS. 1 to 3, a transformer 1 according to an embodiment of the present disclosure includes a transformer main body 10, a tank 20, a connecting pipe 30, and a closing member 40.

[0011] The tank 20 houses the transformer main body 10 and is filled with insulating oil L. The insulating oil L is vegetable oil. Typically, natural ester oil is mentioned as the vegetable oil. The tank 20 is filled with an inert gas G. The inert gas G is typically nitrogen gas.

[0012] The tank 20 has an attachment portion 21 to which a vacuum pumping device such as a vacuum pump can be attached. The vacuum pumping device attached to the attachment portion 21 communicates with the inside of the tank 20 via the attachment portion 21 and can evacuate the inside of the tank 20. The attachment portion 21 is typically located on the upper surface of the tank 20. In the example shown in FIGS. 1 to 3, no vacuum pumping device is attached to the attachment portion 21, and the attachment portion 21 is in a closed state.

[0013] The tank 20 has a filling port 22 through which the tank 20 can be filled with gas. The filling port 22 is typically located on the upper surface of the tank 20. In the example shown in FIGS. 1 to 3, the filling port 22 is in a closed state.

[0014] The connecting pipe 30 is connected to the outside of the tank 20 so that the insulating oil L filled in the tank 20 can flow in. The connecting pipe 30 has an outer peripheral surface 31. The transformer 1 may include a plurality of connecting pipes 30. In the example shown in FIGS. 1 to 3, the connecting pipe 30 is located below the liquid level of the insulating oil L in the tank 20.

[0015] The closing member 40 is attached to the connecting pipe 30 on the side opposite to the tank 20 when viewed from the connecting pipe 30. The closing member 40 is typically a valve. The closing member 40 may be a closing plate or other device capable of closing the connecting pipe 30. A sealing material (not shown) called packing may be provided between the closing member 40 and the connecting pipe 30. Through the closing member 40, the connecting pipe 30 is configured to be connectable to various devices.

[0016] The transformer 1 further includes a radiator 50. In the example shown in FIGS. 1 to 3, the radiator 50 is located on the side opposite to the connecting pipe 30 when viewed from the tank 20. During the operation of the transformer 1, the insulating oil L in the tank 20 flows into the radiator 50, and the insulating oil L that has flowed into the radiator 50 is returned to the tank 20 again. The insulating oil L is cooled in the radiator 50. Thereby, it is possible to suppress the temperature of the transformer 1 from rising excessively during the operation of the transformer 1. Note that the radiator 50 is not shown in FIG. 3.

[0017] Next, a maintenance method for a transformer according to an embodiment of the present disclosure will be described. FIG. 4 is a flowchart showing a maintenance method for a transformer according to an embodiment of the present disclosure. As shown in FIG. 4, the maintenance method for a transformer according to an embodiment of the present disclosure includes a cooling step S1, a vacuum evacuation step S2, a removal step S3, an attachment step S4, a filling step S5, and a heating step S6.

[0018] FIG. 5 is a schematic partial cross-sectional view showing the state of the transformer immediately after the cooling process in one embodiment of the present disclosure. As shown in FIG. 5, in the cooling process S1, the insulating oil L located inside the connecting pipe 30 is cooled. As a result, the kinematic viscosity of the insulating oil L located inside the connecting pipe 30 increases. By cooling the connecting pipe 30 from the outer peripheral surface side of the connecting pipe 30, the insulating oil L located inside the connecting pipe 30 is cooled. As a result, among the insulating oil L located inside the tank 20 and the connecting pipe 30, the kinematic viscosity of the insulating oil L located inside the connecting pipe 30 partially increases. Typically, the cooling member 2 is wound around the outer peripheral surface of the connecting pipe 30 so as to cover the connecting pipe 30, whereby the insulating oil L located inside the connecting pipe 30 is cooled. The insulating oil L located inside the connecting pipe 30 is cooled to approximately near 0°C. A refrigerant flows inside the cooling member 2, and the refrigerant is typically liquid nitrogen.

[0019] FIG. 6 is a schematic partial cross-sectional view showing the state of the transformer immediately after the evacuation process in one embodiment of the present disclosure. As shown in FIG. 6, in the evacuation process S2, the tank 20 is evacuated. More specifically, by sucking the inert gas G inside the tank 20, the space above the insulating oil L filled inside the tank 20 is made into a vacuum state. The space above the insulating oil L filled inside the tank 20 is evacuated by attaching the evacuation device 3 to the mounting portion 21 of the tank 20. The evacuation device 3 is typically a vacuum pump.

[0020] Also, in the evacuation process S2, the space above the insulating oil L inside the tank 20 is made into a vacuum state so that the pressure exerted by the insulating oil L and the inert gas inside the tank 20 on the insulating oil L inside the connecting pipe 30 becomes approximately equal to the atmospheric pressure or smaller than the atmospheric pressure. The pressure inside the tank 20 can be confirmed by a pressure gauge (not shown) provided on the tank 20.

[0021] FIG. 7 is a schematic partial cross-sectional view showing the state of the transformer immediately after the removal process in one embodiment of the present disclosure. As shown in FIG. 7, in the removal process S3, the insulating oil L located inside the connecting pipe 30 is cooled, and the closing member 40 is removed from the connecting pipe 30 while the tank 20 is being evacuated. At this time, the insulating oil L continues to be located inside the tank 20. However, the kinematic viscosity of the insulating oil L inside the connecting pipe 30 increases due to cooling, and the pressure exerted by the insulating oil L and the inert gas inside the tank 20 on the insulating oil L inside the connecting pipe 30 is approximately equal to the atmospheric pressure or less than the atmospheric pressure due to the evacuation. Therefore, the outflow of the insulating oil inside the tank 20 to the outside through the connecting pipe 30 is suppressed. Further, in the removal process S3, it is preferable that the evacuation of the inside of the tank 20 continues from the evacuation process S2. Thereby, the outflow of the insulating oil inside the tank 20 to the outside through the connecting pipe 30 is further suppressed.

[0022] Further, the sealing material disposed between the connecting pipe 30 and the closing member 40 may be further removed from the closing member 40 and the connecting pipe 30. Thereby, it becomes possible to inspect, correct, maintain, or replace the closing member 40 and the sealing material disposed between the closing member 40 and the connecting pipe 30.

[0023] FIG. 8 is a schematic partial cross-sectional view showing the state of the transformer immediately after the attachment process in one embodiment of the present disclosure. As shown in FIG. 8, in the attachment process S4, with the insulating oil L located inside the connection pipe 30 being cooled and the tank 20 being evacuated, the replacement closing member 40A is attached to the connection pipe 30 from which the closing member 40 has been removed. The replacement closing member 40A is typically a member of the same type as the closing member 40, and more typically a valve. The replacement closing member 40A may be a new replacement part different from the closing member 40. The replacement closing member 40A may be the closing member 40 after inspection, repair, or maintenance, etc. The replacement closing member 40A may be a closing plate or other device capable of closing the connection pipe 30. When the sealing material disposed between the connection pipe 30 and the closing member 40 is removed from the closing member 40 and the connection pipe 30, a replacement sealing material (not shown) is disposed. The replacement sealing material may be a new replacement part different from the sealing material. The replacement sealing material may be the sealing material after inspection, repair, or maintenance, etc. Also, in the attachment process S4, it is preferable that the evacuation of the inside of the tank 20 be continuously carried out continuously from the removal process S3. Thereby, the outflow of the insulating oil inside the tank 20 to the outside through the connection pipe 30 is more suppressed.

[0024] In the filling process S5, with the replacement closing member 40A attached to the connection pipe 30, while continuously evacuating the tank 20, an inert gas is filled into the tank 20 through the filling port 22. The inert gas to be filled is preferably of the same type as the inert gas filled in the tank 20 before the evacuation process S2, and is typically nitrogen.

[0025] FIG. 9 is a schematic partial cross-sectional view showing the state of the transformer immediately after the heating process in one embodiment of the present disclosure. As shown in FIG. 9, in the heating process S6, the connecting pipe 30 to which the reattachment closing member 40A is attached is heated. As a result, the temperature of the insulating oil L located inside the connecting pipe 30 rises relatively quickly. Typically, the heating member 4 of the connecting pipe 30 is wound so as to cover the outer peripheral surface of the connecting pipe 30, whereby the insulating oil L located inside the connecting pipe 30 is heated. A high-temperature liquid flows inside the heating member 4, and the liquid is typically hot water.

[0026] By the above maintenance method, inspection, repair, maintenance, or replacement of the closing member 40 or the sealing material located between the closing member 40 and the connecting pipe 30 can be carried out.

[0027] [Appendix] As described above, the embodiments of the present disclosure include the following disclosures.

[0028] (Configuration 1) A maintenance method for a transformer (1) comprising a transformer main body (10), a tank (20) that houses the transformer main body (10) and is filled with insulating oil (L), a connecting pipe (30) connected to the outside of the tank (20) through which the insulating oil L filled in the tank (20) can flow, and a closing member (40) attached to the connecting pipe (30) on the side opposite to the tank (20) when viewed from the connecting pipe (30), the method comprising: a step (S1) of cooling the insulating oil (L) located inside the connecting pipe (30); a step (S2) of evacuating the tank (20); a step (S3) of removing the closing member (40) from the connecting pipe (30) in a state where the insulating oil (L) located inside the connecting pipe (30) is cooled and the tank (20) is evacuated; A maintenance method for a transformer comprising the above steps.

[0029] According to the above Configuration 1, the insulating oil (L) located inside the connection pipe (30) is cooled, and the tank (20) is evacuated, so that the flow of the insulating oil (L) in the connection pipe (30) can be suppressed. Therefore, when the closing member (40) is temporarily removed, it is possible to suppress the insulating oil (L) from flowing out of the connection pipe (30) to the outside. Further, the cooling time and the evacuation time are shorter than the time for extracting the insulating oil (L) from the tank (20). Thus, the time required for the preparatory work for temporarily removing the closing member (40) from the connection pipe (30) can be shortened.

[0030] (Configuration 2) The method for maintaining a transformer according to Configuration 1, wherein the insulating oil (L) located inside the connection pipe (30) is cooled by cooling the connection pipe (30) from the outer peripheral surface side of the connection pipe (30).

[0031] According to the above Configuration 2, the insulating oil (L) inside the connection pipe (30) can be cooled more efficiently as compared with the case of cooling the entire tank (20) and the connection pipe (30).

[0032] (Configuration 3) The method for maintaining a transformer according to Configuration 1 or Configuration 2, wherein the insulating oil (L) is vegetable oil.

[0033] According to the above Configuration 3, the kinematic viscosity of the insulating oil (L) becomes relatively high as compared with the case where the insulating oil (L) is mineral oil. Therefore, in the cooling step (S1), the cooling temperature for preventing the insulating oil (L) from flowing out of the connection pipe (30) to the outside can be set relatively high. Thereby, the insulating oil (L) inside the connection pipe (30) can be cooled efficiently.

[0034] (Configuration 4) The method for maintaining a transformer according to any one of Configurations 1 to 3, further comprising a step (S4) of attaching a closing member for reattachment (40A) to the connection pipe (30) from which the closing member (40) has been removed in a state where the insulating oil (L) located inside the connection pipe (30) is cooled and the tank (20) is evacuated.

[0035] According to the above-described configuration 4, the operation of injecting the insulating oil (L) again into the tank (20) from which the insulating oil (L) has been withdrawn can be omitted. Therefore, the time required for maintaining the transformer (1) can be further shortened.

[0036] (Configuration 5) The method for maintaining a transformer according to Configuration 4, further comprising a step (S6) of heating the connecting pipe (30) to which the reattachment closing member (40A) is attached.

[0037] According to the above-described configuration 5, the temperature of the insulating oil (L) can reach the operable temperature of the transformer (1) earlier as compared with the case where the cooled insulating oil (L) is naturally heated. Therefore, the time required for maintaining the transformer (1) can be further shortened.

[0038] It should be noted that the above-described embodiments disclosed this time are illustrative in all respects and are not a basis for limiting interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description in the claims. Further, all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0039] 1 Transformer, 2 Cooling member, 3 Vacuum pumping device, 4 Heating member, 10 Transformer body, 20 Tank, 21 Mounting portion, 22 Filling port, 30 Connecting pipe, 31 Outer peripheral surface, 40 Closing member, 40A Reattachment closing member, 50 Radiator, G Inert gas, L Insulating oil.

Claims

1. A method for maintaining a transformer, comprising: a transformer body; a tank that houses the transformer body and is filled with insulating oil; a connecting pipe connected to the outside of the tank through which the insulating oil filled in the tank can flow in; and a closing member attached to the connecting pipe on the side opposite to the tank when viewed from the connecting pipe. The method includes: a step of cooling the insulating oil located inside the connecting pipe; a step of evacuating the tank; a step of removing the closing member from the connecting pipe while the insulating oil located inside the connecting pipe is cooled and the tank is evacuated; The method for maintaining a transformer, comprising the above steps.

2. The method for maintaining a transformer according to claim 1, wherein the insulating oil located inside the connecting pipe is cooled by cooling the connecting pipe from the outer peripheral surface side of the connecting pipe.

3. The method for maintaining a transformer according to claim 1 or claim 2, wherein the insulating oil is vegetable oil.

4. The method for maintaining a transformer according to claim 1 or claim 2, further comprising a step of attaching a closing member for reattachment to the connecting pipe from which the closing member has been removed while the insulating oil located inside the connecting pipe is cooled and the tank is evacuated.

5. The method for maintaining a transformer according to claim 4, further comprising a step of heating the connecting pipe to which the closing member for reattachment is attached.

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