JP7548857B2 - Oil-filled transformer - Google Patents

Description

The present invention relates to an oil-immersed transformer.

In the high-frequency transformer described in Patent Document 1, both the primary and secondary windings are covered with Kapton tape, with the primary winding on the inside and the secondary winding on the outside. The primary winding is inserted inside the secondary winding, and a thick Nomex sheet is sandwiched between the adjacent windings to maintain an insulating distance.

Patent Publication 2017-174958

The windings of a distribution transformer generate heat due to power loss, and the windings cool that heat through the circulation of insulating oil inside the tank. As the temperature of the insulating oil rises, its density decreases and it moves to the top, while as the insulating oil cools, its density increases and it moves to the bottom of the tank, where it is drawn into the windings, absorbing heat from the windings and moving to the top. The windings have a heat distribution similar to the temperature distribution of the insulating oil circulating up and down.

In the series of cooling systems in oil-filled transformers described above, there is always a difference in temperature between the upper and lower windings, with the upper winding always operating at a higher temperature than the lower winding, causing faster thermal degradation. Also, the inner winding (low voltage) has a smaller area in contact with the insulating oil than the outer winding (high voltage), and because its temperature is higher, thermal degradation occurs more quickly.

Patent document 1 takes into consideration maintaining the insulation distance between windings, but does not consider suppressing differences in thermal degradation of windings in oil-filled transformers.

The object of the present invention is to provide an oil-immersed transformer that suppresses differences in thermal degradation of windings.

In this invention, the winding is divided into upper and lower parts, insulating oil is introduced through the gap, and insulating paper with different heat resistance classes is used for each part.

The present invention makes it possible to realize an oil-immersed transformer that suppresses differences in thermal degradation of windings.

FIG. 2 is an external view of a winding and an iron core according to the first embodiment. FIG. 4 is an external view of a winding and an iron core in a comparative example. FIG. 3 is a diagram illustrating a winding and insulating paper according to the first embodiment. FIG. 11 is a diagram illustrating a winding and insulating paper according to a second embodiment. FIG. 11 is a diagram illustrating a winding and insulating paper according to a third embodiment.

The following describes the examples using the drawings.

Figure 1 is an external view of the core-winding assembly having the core and windings in Example 1, seen from an angle. The core consists of an outer core 1 and an inner core 2. In this example, the coil (winding) is composed of an upper winding 4 and a lower winding 5. Figure 2 is an external view of the core-winding assembly in the comparative example, seen from an angle. In the comparative example, the winding 3 is not divided into an upper winding 4 and a lower winding 5.

The three-phase, three-legged oil-filled transformer to which this embodiment is applied contains insulating oil and the core-winding assembly shown in Figure 1 inside the tank. The tank and insulating oil are omitted from Figure 1.

The core-winding assembly has three-phase (U-phase, V-phase, W-phase) coils (upper winding 4 and lower winding 5) attached to the multiple legs of the core (outer core 1 and inner core 2) from the left in Figure 1. The coils are made up of a primary winding section and a secondary winding section.

In this embodiment, the winding 3 is divided in the height direction, and oil is drawn into the upper winding 4 through the gap (the divided portion) formed between the upper winding 4 and the lower winding 5 to cool it. However, the upper winding 4 and the lower winding 5 are electrically connected.

Insulating oil is introduced into the gap formed between the upper winding 4 and the lower winding 5 to cool the heat generated by the upper winding 4. This reduces the difference in thermal degradation of the winding compared to the comparative example shown in Figure 2.

Figure 3 is a diagram explaining the windings and insulating paper in Example 1. Figure 3(a) is a diagram showing the arrangement of insulating paper 6 in the lower winding 5 when the lower winding 5 in Figure 1 is cut horizontally. Figure 3(b) is a diagram showing the arrangement of insulating paper 7 of the upper winding 4 when the upper winding 4 in Figure 1 is cut horizontally.

In FIG. 3, the upper winding 4, which has a higher temperature, is wrapped with insulating paper 7 of a higher grade of heat resistance than the lower winding 5, and the insulating paper 7 is placed between the upper windings 4.

According to the first embodiment, it is possible to suppress excessive thermal deterioration of only the upper winding, which has a higher temperature. In addition, by using expensive insulating paper with a high heat resistance class only for the upper winding and not for the lower winding, it is possible to reduce costs and suppress the difference in thermal deterioration of the windings. In addition, by using insulating paper with a high heat resistance class for the upper winding, it is possible to reduce the cooling area of cooling fins, etc., and therefore the tank can be made smaller, thereby suppressing the difference in thermal deterioration of the windings, suppressing the manufacturing cost of the oil-filled transformer, and realizing a compact oil-filled transformer.

Fig. 4 is a diagram illustrating the windings and insulating paper in Example 2. In Fig. 4, the windings are composed of an inner winding 9 and an outer winding 8 which is on the outer circumferential side of the inner winding 9 and faces the insulating oil.
The configuration of FIG. 4 may be any of the configurations of the upper winding 4 and the lower winding 5 of FIG.

The outer winding 8 is a primary winding that is connected to the primary side, which is the high voltage side, and the inner winding 9 is a secondary winding that is connected to the secondary side, which is the low voltage side.
Explanation of the same matters as in the first embodiment will be omitted.

In the configuration of Example 1 shown in FIG. 1, the inner winding 9 is surrounded by the outer winding 8, so the area of contact with the oil is small and heat is easily trapped. The inner winding 9 is wrapped with insulating paper 7 of a higher grade of heat resistance than the insulating paper 6 used for the outer winding 8, so that the insulating paper 7 is placed between the inner windings 9.

In this embodiment, a fourth insulating paper 7 and a third insulating paper 6 are wound around the windings between the inner windings 9 and between the outer windings 8, respectively. The fourth insulating paper 7 placed between the inner windings is an insulating paper with a higher heat resistance class than the third insulating paper 6.

In Patent Document 1, both the primary and secondary windings are covered with Kapton tape, which has a higher heat resistance class than Nomex sheet, with the primary winding on the inside and the secondary winding on the outside. Therefore, the configuration is different from that of this embodiment. Also, in Patent Document 1, a thick Nomex sheet is placed between the primary and secondary windings to ensure a reliable insulation distance, but Patent Document 1 does not suggest that the difference in thermal deterioration of the inner winding 9 and the outer winding 8 can be suppressed.

According to this embodiment, the difference in thermal degradation between the inner winding 9 and the outer winding 8 can be suppressed.

Figure 5 is a diagram explaining the windings and insulating paper in Example 3. Figure 5(a) is a diagram showing the arrangement of insulating paper 6 in the windings that make up the two outer legs (U-phase, W-phase) 10 in the three-phase, three-legged oil-filled transformer of Figure 1. Figure 5(b) is a diagram showing the arrangement of insulating paper 7 in the winding that makes up one leg 11 (V-phase) in Figure 1. Explanations of matters that are the same as in Example 1 or Example 2 will be omitted.

In the case of a tripod-wound core, the monopod 11 located in the center has a smaller area in contact with the insulating oil than the bipods 10 located on the outside, and is more likely to trap heat than the outer bipods 10. The winding that makes up the monopod 11 located in the center is wrapped with insulating paper 7 (sixth insulating paper) that has a higher heat resistance class than the insulating paper 6 (fifth insulating paper) in the bipod 10, so that the insulating paper 7 is placed between the windings that make up the monopod 11.

For either the upper winding 4 or the lower winding 5, select the heat-resistant class of insulating paper appropriate for the temperature and place it between the windings.

This embodiment can reduce the difference in thermal degradation between the windings on the two outer legs of a three-phase, three-legged oil-immersed transformer and the winding on the central leg.

In this embodiment, the winding of the oil-immersed transformer is divided into three parts in the height direction, and each of the two divided windings is called a winding group, and the oil-immersed transformer is composed of three winding groups.
Oil is drawn into the windings through two gaps (divided areas) formed between the upper winding, the middle winding, and the lower winding to cool them. However, the upper winding, the middle winding, and the lower winding are electrically connected. Explanations of the same points as in the first to third embodiments will be omitted.

In this embodiment, although not shown in the figures, the seventh insulating paper arranged in the first winding group constituting the upper winding uses insulating paper with a higher heat resistance class than the eighth insulating paper arranged in the second winding group constituting the middle winding or the lower winding.

Depending on the temperature, the middle winding also uses insulating paper with a different heat resistance class from that of the upper winding 4 or lower winding 5. For the upper winding 4 or lower winding 5, an insulating paper with a heat resistance class appropriate for the temperature is selected and placed between the windings.

In this embodiment, the windings are divided into three groups from top to bottom: an upper winding, a middle winding, and a lower winding, but the oil-immersed transformer may have four or more winding groups.

According to this embodiment, the windings of the oil-filled transformer are divided into three or more winding groups in the vertical direction. Compared to embodiment 1, the number of gaps arranged between the winding groups to take in oil is increased, and the difference in cooling efficiency between the windings can be reduced, making it possible to suppress the difference in thermal deterioration of the windings.

1...Outer core, 2...Inner core, 3...Winding, 4...Upper winding, 5...Lower winding, 6...Insulating paper (heat resistance class: low), 7...Insulating paper (heat resistance class: high), 8...Outer winding, 9...Inner winding, 10...Two legs (U-leg winding, W-leg winding), 11...One leg (V-leg winding)

Claims (4)

An oil-filled transformer in which an assembly of an iron core and a winding is housed in a tank and filled with insulating oil,
The winding comprises:
An upper winding portion and a lower winding portion,
The windings are of an oil-immersed transformer in which the heat resistance class of the insulating paper used between the upper windings is higher than the heat resistance class of the insulating paper used between the lower windings. In the oil-immersed transformer according to claim 1,
An oil-filled transformer having a gap between the upper winding portion and the lower winding portion. An oil-filled transformer in which an assembly of an iron core and a winding is housed in a tank and filled with insulating oil,
The winding comprises:
An upper winding portion and a lower winding portion,
An oil-filled transformer in which the heat resistance class of the insulating paper used between the inner windings is higher than the heat resistance class of the insulating paper used between the outer windings. An oil-filled transformer in which an assembly of an iron core and a winding is housed in a tank and filled with insulating oil,
The winding comprises:
An upper winding portion and a lower winding portion,
The core is a tripod core,
An oil-immersed transformer in which the heat resistance class of the insulating paper used between the windings of the central leg of the three legs is higher than the heat resistance class of the insulating paper used between the windings of the two outer legs.

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