JP2963645B2 - Cage-shaped connecting conductor and bushing using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cage connection conductor used in the technical field of electric power equipment and a bushing using the same.

[0002]

2. Description of the Related Art The center conductor of a bushing needs to have a sufficient current carrying capacity to pass a current, and the current carrying capacity is determined by the amount of heat generated by Joule loss of the center conductor due to current supply and heat radiation conditions. Depends on maximum temperature rise. By the way, JEC-183 "Bushing" specifies the allowable value of this temperature at 105 ° C. This temperature rise value is determined by the manner of heat transfer from the central conductor, which is the heat-generating part, to the outer part, which is the heat-dissipating part.How to reduce the thermal resistance during this time is an important means for improving the current carrying capacity. Become. That is, even in the case of bushings using the same shape and size of the center conductor, the value of the current that can flow varies greatly depending on the above-mentioned thermal resistance.

In order to reduce the thermal resistance, as shown in FIG. 6, a central conductor 1 is used as a pipe to convect an insulating oil having a high specific heat and a high specific gravity inside, and then cooled like other oil-filled equipment. A structure for quickly transferring heat to the inner surface of the outer component 2 is widely used. In order to convection the insulating oil inside the center conductor 1 as described above, it is necessary to provide an inlet and an outlet for the insulating oil. Is provided.

The larger the size of these oil passage holes 3, the lower the fluid resistance of the insulating oil, so that the cooling effect is enhanced and the thermal resistance between the heat generating portion and the heat radiating portion can be reduced. However, when the size of the oil hole 3 is increased,
A reduction in the current-carrying cross-sectional area of the central conductor 1 causes a reduction in the current-carrying capacity and a decrease in the mechanical strength. In particular, in the center clamp bushing, a large tensile stress acts on the center conductor 1, so that a decrease in mechanical strength is a great constraint. Therefore, the conventional structure as shown in FIG. 6 may not be able to provide a sufficient cooling effect.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a cage-like connecting conductor capable of obtaining a sufficient cooling effect without lowering the mechanical strength of the center conductor. And a bushing using the same.

[0006]

The cage-like connecting conductor of the present invention made to solve the above-mentioned problems is a metal cage-like body having a connecting portion with a center conductor on one or both end faces. The outer diameter is larger than the outer diameter of the center conductor, and the total area of a large number of oil passage holes formed on the side surface is made larger than the flow path cross-sectional area inside the center conductor. . Further, the bushing of the present invention is characterized in that the above-mentioned cage-shaped connection conductor is connected to a center conductor.

[0007]

1 to 3 are sectional views showing a preferred embodiment of the present invention. The cage connection conductor of FIG. 1 is a cage formed by processing a cylindrical body (a large-diameter pipe) made of a metal material having excellent conductivity such as copper and aluminum, and has a skin coefficient (DC resistance). And the ratio of AC resistance to AC). The cage-shaped connection conductor has connection portions 4 and 4 with the center conductor 1 on upper and lower end surfaces. The connection with the center conductor 1 may be welding connection in addition to the screw connection as shown. In addition, a large number of oil passage holes 5 are provided on the side surface of the cage-shaped connection conductor. The shape of the oil passage hole 5 may be circular, elliptical or other oval, but in the case of a circular shape, the Karman vortex is formed when the insulating oil passes, thereby increasing the flow resistance. It is preferable to make the shape oval because it is easy to perform.

The outside diameter of the cage-shaped connection conductor is larger than the outside diameter of the center conductor 1 so that the cage conductor has a tensile strength greater than the tensile strength of the center conductor 1 itself, and the resistance to current per unit length. Is smaller than the conduction resistance per unit length of the center conductor 1. By making the total area of the large number of oil passage holes 5 larger than the cross-sectional area of the flow path of the insulating oil inside the central conductor 1, the flow of the insulating oil is smoothly performed.

The cage-shaped connecting conductor shown in FIG. 2 is formed by connecting a plurality of small-diameter rod-shaped or bar-shaped conductors 7 between the outer peripheral portions of two flanges 6 and 6. It is preferable that the cross section of these small-diameter rod-shaped or bar-shaped conductors 7 is rounded by chamfering or the like to reduce fluid resistance. Note that FIG.
The cage-shaped connecting conductor is formed by welding the flanges 6 and 6 to the conductor 7. In the case of such a welding structure, the material is preferably made of an aluminum alloy, and the strength is preferably improved by heat treatment after welding. .

The cage connection conductors shown in FIGS. 1 and 2 are used by connecting the center conductor 1 up and down. FIG. 3 shows the cage connection conductor arranged between the terminal seat 8 and the center conductor 1. 4 shows an example of a connection conductor. This is the same as that of FIG. 1 except that the configuration of the lower connection portion 4 is different.

Such a cage-shaped connection conductor is incorporated at or near the end of the center conductor 1 of the bushing. The bushing having this structure does not cause a decrease in the mechanical strength of the center conductor 1. Since the insulating oil can be smoothly circulated through the oil passage hole 5, a sufficient cooling effect can be obtained. For this reason, as shown in the next embodiment, the current carrying capacity of the bushing can be increased. In addition,
In the case of the vertical mounting bushing, the lowermost part of the oil passage hole 5 of the cage-shaped connection conductor is set to be lower than the lowest position of the oil surface of the head expansion chamber. It is desirable that the total oil passing area be larger than the cross-sectional area of the flow path of the insulating oil inside the central conductor 1.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A temperature rise test was conducted on a bushing for a 500 kV class transformer in which the cage-shaped connecting conductor having the structure shown in FIG. 1 was incorporated near the upper and lower ends of the center conductor. It was possible to conduct electricity up to 8000 A with the center conductor. FIG.
Is a graph showing the temperature distribution in the central conductor length direction in this case.

A temperature rise test was also performed on a 275 kV class wall-through bushing in the same manner. As a result, the center conductor having a current carrying capacity of 4500 A in the conventional structure was 8000 A
It became possible to energize until. Since the through-wall bushing is arranged horizontally, convection of the insulating oil hardly occurs in the center conductor, and heat is trapped inside as shown in FIG. 5, and the temperature at the highest point is extremely high. On the other hand, the bushing incorporating the cage-shaped connection conductor of the present invention has a gentle temperature gradient, and the temperature at the highest point is reduced, so that the current carrying capacity can be improved. As described above, according to the present invention, local temperature rise is suppressed, and the average temperature of the insulating oil during the bushing increases, so that the amount of heat radiated from the outer portion increases. It becomes.

[0014]

As described above, according to the cage connection conductor of the present invention and the bushing using the same, a sufficient cooling effect can be obtained without lowering the mechanical strength of the center conductor. Thus, the current carrying capacity of the bushing can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the present invention.

FIG. 4 is a graph showing a temperature distribution in a longitudinal direction of a center conductor when the present invention is applied to a bushing for a transformer.

FIG. 5 is a graph showing a temperature distribution in a longitudinal direction of a center conductor when the present invention is applied to a wall-through bushing.

FIG. 6 is a sectional view showing a conventional example and a simulation circuit thereof.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Center conductor, 2 outer parts, 3 oil holes, 4 connection parts, 5 many oil holes, 6 flanges, 7 rod-shaped or bar-shaped conductor, 8 terminal seat

Claims (4)

(57) [Claims] 1. A metal cage having a connection portion with a central conductor on one or both end faces, the outer diameter of which is larger than the outer diameter of the central conductor, and a plurality of through-holes formed on side surfaces. A cage-shaped connecting conductor, wherein the total area of the oil hole is larger than the cross-sectional area of the flow passage inside the central conductor. 2. The cage-like connecting conductor according to claim 1, wherein the metal cage-like body has a large number of oil passage holes formed in a side surface of the metal cylindrical body. 3. A metal basket-like body connects the outer periphery of two flanges with a number of rod-like or bar-like conductors,
2. The cage-shaped connecting conductor according to claim 1, wherein the connecting conductor has a structure in which a number of oil passage holes are formed between them. 4. A bushing wherein the cage-shaped connection conductor according to claim 1 is connected to a center conductor.