Oil-filled transformer

Abstract

To suppress deterioration of insulating oil with a simple structure and to reduce the size.SOLUTION: The oil-immersed transformer includes a transformer tank for storing a transformer content, and an expansion chamber provided on an outer upper surface of the transformer tank and having a space communicating with the transformer tank inside. The transformer tank is filled with an amount of insulating oil which does not come into contact with the inner upper surface of the transformer tank when the liquid level reaches the maximum height position, and the transformer tank and the expansion chamber are filled with inert gas in a space other than the insulating oil.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an oil-immersed transformer. [Background technology]

[0002] In oil-filled transformers, the transformer tank is filled with insulating oil as a cooling medium. When insulating oil comes into contact with oxygen and moisture in the air, it deteriorates and its electrical properties decline. For this reason, the transformer tank is sometimes sealed to block out outside air. However, since insulating oil expands and contracts due to temperature changes during transformer operation, it is necessary to absorb the volumetric changes of the insulating oil in order to maintain a constant internal pressure in the sealed transformer tank.

[0003] Known methods for absorbing volumetric changes in insulating oil while blocking outside air include the non-pressure sealed type with a conservator and the nitrogen sealed type. In the case of the non-pressure sealed type with a conservator, the conservator is connected to the transformer tank and is filled with insulating oil just like the inside of the transformer tank. The conservator contains an air bag, which contracts when the insulating oil expands, and expands when the insulating oil contracts, thereby absorbing the volumetric changes in the insulating oil. The non-pressure sealed type with a conservator does not involve gas, so it is effective in preventing deterioration of insulating oil, but it has a complex structure and is expensive.

[0004] In contrast, the gas-sealed type has a gas space filled with an inert gas such as nitrogen at the top of the transformer tank. The inert gas filled in this gas space absorbs the expansion and contraction of the insulating oil due to temperature changes. The gas-sealed type has a simpler structure and fewer parts than the non-pressure-sealed type with a conservator, making it cheaper to manufacture. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-33256 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the gas-sealed type requires a gas space at the top of the transformer tank, which makes it difficult to miniaturize the transformer.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an oil-filled transformer that has a simple configuration, is capable of suppressing deterioration of insulating oil, and is also capable of being made smaller. [Means for solving the problem]

[0008] The oil-filled transformer of the present embodiment includes a transformer tank that accommodates the contents of the transformer, and an expansion chamber that is provided on the outer upper surface of the transformer tank and has an internal space that communicates with the transformer tank. The transformer tank is filled with insulating oil in an amount that does not contact the inner upper surface of the transformer tank when the liquid level is at its maximum height, and the transformer tank and the expansion chamber are filled with an inert gas in the space other than the insulating oil. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view showing a schematic configuration of an oil-immersed transformer according to an embodiment; [Figure 2] FIG. 1 is a side view showing a schematic configuration of an oil-immersed transformer according to an embodiment. [Figure 3] FIG. 1 is a front cross-sectional view showing a schematic configuration of an oil-immersed transformer according to an embodiment. [Figure 4] FIG. 1 is a cross-sectional side view showing a schematic configuration of an oil-immersed transformer according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An oil-immersed transformer according to one embodiment will be described below with reference to the drawings. Note that although the present embodiment will be described using a three-phase transformer as an example, the design concept of the present embodiment can also be applied to a single-phase transformer.

[0011] The oil-filled transformer 10 of this embodiment is a gas-sealed oil-filled transformer filled with an inert gas such as nitrogen gas. As shown in FIGS. 1 to 4, the oil-filled transformer 10 includes a transformer tank 20, a transformer inner casing 30, a bushing 40, a heat sink 50, and an expansion chamber 60. The transformer tank 20 is configured as, for example, a rectangular box in plan view. As shown in FIGS. 3 and 4, the transformer tank 20 houses the transformer inner casing 30 therein. The transformer inner casing 30 includes a coil 31 and an iron core 32. Although not shown in detail, the coil 31 includes a high-voltage side coil and a low-voltage side coil wound around the iron core 32.

[0012] As shown in Fig. 3, the transformer tank 20 is filled with insulating oil L as a cooling medium. The amount of insulating oil L filled in the transformer tank 20 is set so that the transformer contents 30 will not be exposed from the insulating oil L when the liquid level S reaches its minimum height, that is, when the insulating oil L cools and contracts and the liquid level S drops to its lowest position. The amount of insulating oil L filled in the transformer tank 20 is also set so that the insulating oil L will not come into contact with the inner upper surface 21 of the transformer tank 20 when the liquid level S reaches its maximum height, that is, when the insulating oil L heats and expands and the liquid level S reaches its highest position.

[0013] The bushing 40 is provided on the outer upper surface 22 of the transformer tank 20. As shown in Fig. 3, the bushing 40 is inserted into the transformer tank 20 by penetrating the upper surfaces 21 and 22 of the transformer tank 20. The tip portion 41, i.e., the lower end portion 41, of the bushing 40 is immersed in insulating oil L inside the transformer tank 20 and is connected to the coil 31 via wiring.

[0014] The oil-immersed transformer 10 includes a plurality of radiators 50. The radiators 50 have the function of radiating heat from the insulating oil L. The radiators 50 are provided outside the transformer tank 20, on the side surfaces of the transformer tank 20. In the present embodiment, the radiators 50 are provided on the side surfaces of the longer sides of the transformer tank 20. As shown in FIGS. 2 and 4, the radiators 50 are connected to the inside of the transformer tank 20 via upper piping 51 and lower piping 52.

[0015] The upper pipe 51 is located higher than the lower pipe 52. The upper pipe 51 is provided at a position where it is not exposed from the insulating oil L even when the liquid level S of the insulating oil L reaches the minimum height position, that is, when the insulating oil L cools and contracts, causing the liquid level to drop to the lowest position.

[0016] When the oil-immersed transformer 10 is in operation, the transformer internals 30 generate heat, causing the temperature of the insulating oil L around the transformer internals 30 to rise. As the temperature of the insulating oil L rises, it expands, and the relatively hotter portion moves upward within the transformer tank 20. The upwardly moving insulating oil L then pushes up the liquid level S, and some of it flows through the upper piping 51 into the radiator 50. The insulating oil L that flows into the radiator 50 is cooled by heat exchange with the outside air in the radiator 50, and its temperature drops. The insulating oil L that has been cooled within the radiator 50 contracts, and the relatively cooler portion moves downward within the radiator 50. The insulating oil L that has moved downward within the radiator 50 then returns to the transformer tank 20 through the lower piping 52. In this way, the insulating oil L undergoes natural convection between the inside of the transformer tank 20 and the inside of the radiator 50, thereby removing Joule heat generated from the inside of the transformer 30 and cooling the inside of the transformer 30.

[0017] The expansion chamber 60 is provided on the outer upper surface of the transformer tank 20. The expansion chamber 60 is configured in a box shape with a space 61 inside. The boundary between the expansion chamber 60 and the transformer tank 20 is connected in an airtight manner. The space 61 inside the expansion chamber 60 communicates with the inside of the transformer tank 20. For example, as shown in Figures 3 and 4, the transformer tank 20 and the expansion chamber 60 communicate with each other via a communication part 11. The space 61 inside the expansion chamber 60 is not open to the outside, i.e., not open to the atmosphere.

[0018] In the transformer tank 20 and the expansion chamber 60, the spaces other than the insulating oil L are filled with an inert gas G such as nitrogen. That is, the space in the transformer tank 20 above the liquid level S of the insulating oil L is defined as a gas space 23 in the transformer tank 20. The gas space 23 and the expansion chamber 60 are filled with the inert gas G. The inert gas G can move between the transformer tank 20 and the expansion chamber 60 through the communication portion 11. When the liquid level S is displaced due to the expansion and contraction of the insulating oil L, the inert gas G compresses and expands in response to the volume change of the spaces other than the insulating oil L in the transformer tank 20 and the expansion chamber 60. As a result, the inert gas G absorbs the expansion and contraction of the insulating oil L due to temperature changes filled in the transformer tank 20, which is isolated from the outside air, and can maintain the pressure in the transformer tank 20 within a constant range while preventing the insulating oil L from contacting the outside air.

[0019] 1, the height dimension from the outer upper surface 22 of the transformer tank 20 to the upper end of the expansion chamber 60 is defined as the height dimension H1 of the expansion chamber 60. Furthermore, for the bushing 40 with the highest height dimension from the outer upper surface 22 of the transformer tank 20 among the multiple bushings 40, the height dimension from the outer upper surface 22 to the upper end of that bushing 40 is defined as the maximum height dimension H2 of the bushing 40. In this case, the height dimension H1 of the expansion chamber 60 is set to a value smaller than the maximum height dimension H2 of the bushing 40. In other words, the expansion chamber 60 is set lower than the largest bushing 40.

[0020] The oil-filled transformer 10 also includes an oil level gauge 70. The oil level gauge 70 measures the position of the liquid level S of the insulating oil L in the transformer tank. The oil level gauge 70 has a display 71 and a float 72. The float 72 is disposed so as to float on the liquid level S of the insulating oil L. The display 71 displays the height position of the liquid level S in analog or digital form according to the movement of the float 72. The display 71 of the oil level gauge 70 is provided on the side surface of the expansion chamber 60. In this case, the interval W1 between adjacent radiators 50 is set to be smaller than the width dimension W2 of the display 71.

[0021] The oil-immersed transformer 10 also includes a reinforcing member 80. The reinforcing member 80 is provided on a side surface of the transformer tank 20 and has the function of reinforcing the transformer tank 20. In this case, the reinforcing member 80 is attached to a side surface of the transformer tank 20 on which the radiator 50 is not provided. The reinforcing member 80 can be made of, for example, a long steel material, and is arranged so that the longitudinal direction of the reinforcing member 80 is horizontal along the side surface of the transformer tank 20.

[0022] In this embodiment, the reinforcing member 80 can be formed, for example, by welding a U-shaped steel beam having a U-shaped cross section into a bag shape. That is, the reinforcing member 80 can be formed by covering the open portion of a U-shaped steel beam with a steel plate and welding it. The reinforcing member 80 has an auxiliary chamber 81 inside. The auxiliary chamber 81 is a space provided inside the reinforcing member 80 that is not open to the outside, and is connected to the inside of the expansion chamber 60 via a connecting pipe 90.

[0023] According to the embodiment described above, the oil-immersed transformer 10 includes a transformer tank 20 and an expansion chamber 60. The transformer tank 20 accommodates the transformer internals 30. The expansion chamber 60 is provided on the outer upper surface of the transformer tank 20 and has an internal space 61 that communicates with the transformer tank 20. The transformer tank 20 is filled with insulating oil L in an amount that does not contact the inner upper surface 21 of the transformer tank 20 when the liquid level S is at the maximum height position. The transformer tank 20 and the expansion chamber 60 are filled with an inert gas G in the spaces other than the insulating oil L.

[0024] According to this, by adopting a gas-tight type transformer tank 20 that blocks outside air, it is possible, with a simple configuration, to prevent the insulating oil L from coming into contact with the outside air and suppress deterioration of the insulating oil L. Furthermore, in the oil-filled transformer 10 of this embodiment, by providing the expansion chamber 60 on the outer upper surface of the transformer tank 20, it is possible to reduce the gas space 23 inside the transformer tank 20. As a result, it is possible to reduce the size of the transformer tank 20.

[0025] The oil-immersed transformer 10 further includes a bushing 40 that is passed through the upper surfaces 21 and 22 of the transformer tank 20. The height H1 from the outer upper surface 22 of the transformer tank 20 to the upper end of the expansion chamber 60 is set to be equal to or less than the maximum height H2 from the outer upper surface 22 of the transformer tank 20 to the upper end of the bushing 40.

[0026] Because the bushing 40 is an essential component of the oil-filled transformer 10, providing the expansion chamber 60 on the outer upper surface 22 of the transformer tank 20 makes it possible to effectively utilize the dead space where the bushing 40 is not provided. Furthermore, by making the height dimension H1 of the expansion chamber 60 equal to or less than the maximum height dimension H2 of the bushing 40, that is, by ensuring that the height dimension H1 of the expansion chamber 60 does not exceed the maximum height dimension H2 of the bushing 40, it is possible to prevent an increase in the height dimension due to the provision of the expansion chamber 60. In other words, this makes it possible to prevent the oil-filled transformer 10 from becoming larger due to the provision of the expansion chamber 60.

[0027] 3, the tip 41 of the bushing 40 needs to be immersed in insulating oil L. In this case, if the bushing 40 is installed through the top surfaces 21 and 22 of the transformer tank 20, the overall length of the bushing 40 needs to be increased by the amount of the gas space 23 of the transformer tank 20, making it difficult to use a standard bushing 40 with a short overall length. In contrast, according to this embodiment, the gas space 23 of the transformer tank 20 can be minimized, making it possible to use a standard bushing 40 with a short overall length. As a result, the component cost of the bushing 40 can be reduced, and the bushing 40 can be more easily maintained.

[0028] Here, in order to monitor the position of the liquid level S of the insulating oil L in the transformer tank 20, it is necessary to provide an oil level gauge 70 in the oil-filled transformer 10. In this case, since the radiators 50 are provided on the side of the transformer tank 20, if the indicator 71 of the oil level gauge 70 is to be provided on the side of the transformer tank 20, it must be provided between the adjacent radiators 50. However, if the indicator 71 of the oil level gauge 70 is provided between the radiators 50, the radiators 50 will get in the way and make it difficult for the user to see.

[0029] Therefore, in the oil-filled transformer 10 of this embodiment, the display 71 of the oil level gauge 70 is provided on the side surface of the expansion chamber 60. This ensures that the radiator 50 does not get in the way when the user looks at the display 71, thereby improving the visibility of the display 71 of the oil level gauge 70.

[0030] Furthermore, the oil-filled transformer 10 of the embodiment includes a plurality of radiators 50. Here, when the indicator 71 of the oil level gauge 70 is provided on the side of the transformer tank 20, the interval W1 between adjacent radiators 50 needs to be equal to or greater than the width W2 of the indicator 71 to ensure the visibility of the indicator 71. In contrast, by providing the indicator 71 of the oil level gauge 70 on the side of the expansion chamber 60, the limitation on the interval W1 between the radiators 50 due to the indicator 71 is eliminated, and the interval W1 between the radiators 50 can be made smaller than the width W2 of the indicator 71. That is, in the present embodiment, the interval W1 between adjacent radiators 50 is made smaller than the width W2 of the indicator 71 of the oil level gauge 70. This allows the radiators 50 to be made larger, thereby improving their heat dissipation performance.

[0031] The oil-filled transformer 10 of the embodiment also includes a reinforcing member 80. The reinforcing member 80 is provided on the side surface of the transformer tank 20 and serves to reinforce the transformer tank 20. The reinforcing member 80 is formed by welding U-shaped steel bars into a bag shape, and has an auxiliary chamber 81 inside the reinforcing member 80 that communicates with the transformer tank 20 via the expansion chamber 60.

[0032] In this way, the reinforcing member 80 of this embodiment can reinforce the transformer tank 20 while ensuring a larger space for the inert gas G to escape when the insulating oil L expands. In other words, the gas space 23 of the transformer tank 20 can be made smaller, which in turn allows the transformer tank 20 to be made smaller, and ultimately the entire oil-filled transformer 10 to be made smaller.

[0033] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure. [Explanation of symbols]

[0034] 10... oil-filled transformer, 20... transformer tank, 21... inner upper surface, 22... outer upper surface, 30... transformer contents, 40... bushing, 50... radiator, 60... expansion chamber, 61... space, 70... oil level gauge, 80... reinforcing member, 81... auxiliary chamber

Claims

1. a transformer tank containing the transformer contents; an expansion chamber provided on an outer upper surface of the transformer tank and having a space therein communicating with the transformer tank, The transformer tank is filled with insulating oil in an amount such that the insulating oil does not come into contact with the inner upper surface of the transformer tank when the liquid level is at a maximum height position, In the transformer tank and the expansion chamber, the spaces other than the insulating oil are filled with an inert gas. Oil-filled transformer.

2. a bushing passed through an upper surface of the transformer tank; a height dimension from an upper surface of the transformer tank to an upper end of the expansion chamber is equal to or less than a height dimension from the upper surface of the transformer tank to an upper end of the bushing; The oil-immersed transformer according to claim 1.

3. a radiator provided outside the transformer tank, through which the insulating oil passes and which radiates heat of the insulating oil; an oil level gauge that measures the oil level of the insulating oil in the transformer tank, The oil level gauge is provided on a side surface of the expansion chamber. The oil-immersed transformer according to claim 1.

4. A plurality of the heat sinks are provided, The interval between the radiators is smaller than the width dimension of the oil level gauge. The oil-immersed transformer according to claim 3.

5. a reinforcing member provided on a side surface of the transformer tank to reinforce the transformer tank, the reinforcing member is formed by welding a U-shaped steel bar into a bag shape, and has an auxiliary chamber inside the reinforcing member that communicates with the transformer tank via the expansion chamber. The oil-immersed transformer according to claim 4.

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