JPS6245389Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a center clamp type bushing.

Bushings are used to insulate and draw out the lead wires of electrical equipment from their outer boxes. Bushings are usually made of a pipe-shaped center conductor through which current flows, or a pipe-shaped center conductor into which a flexible conductor through which current flows is inserted. It consists of an insulating material layer that insulates this central conductor from the ground, and external products such as insulators and support fittings that house them.

The conventional stud-type bushing with a so-called center clamp structure, as shown in Figure 1,
An insulating layer 2 formed by winding insulating paper, for example, is provided around the outer periphery of the center conductor 1. This insulating layer 2
A support fitting 3 is fitted on the outer periphery of the middle part of the head cap 3, and two side pipes 4a and 4b are provided on both sides of the support fitting 3, and screwed to the head cap 5 and the center conductor 1 via the center conductor 1. These are assembled together by a lower clamp 6. Further, an insulating medium 7 such as insulating oil or insulating gas is sealed inside the support fittings 3 and the hollow tubes 4a, 4b, and gaskets 8a, 8 are provided at the joints of each component.
b, 8c, 8d, and 8e are interposed. These gaskets are sealed at their joints by pressing each component through the center conductor 1 with a compression spring 9 disposed inside the head cap 5.

In such conventional bushings, since the compression spring 9 is housed inside the head cap 5, the diameter of the head cap 5 becomes larger than necessary, which increases the weight of the head and reduces earthquake resistance. There was a problem that it was not desirable from the top.

This invention was made taking the above points into consideration.
The purpose is to maintain sealing performance,
To provide a bushing with a center clamp structure that reduces the size of the head cap and improves earthquake resistance.

The present invention will be described below with reference to an embodiment shown in the drawings.

In FIG. 2, for example, a pipe-shaped central conductor 1
Insulating layer 1 formed by winding insulating paper around the outer circumference of 1
2 is wound around the insulating layer 12, and a support fitting 13 is fitted on the outer periphery of the intermediate portion of the insulating layer 12, and an air side insulator tube 14 (hereinafter referred to as an upper insulator tube) and an air side insulator tube 14 (hereinafter referred to as upper insulator tube) and An insulating medium side insulator 15 (hereinafter referred to as a lower insulator) is provided. A lower clamp 16 is screwed to the lower end of the lower insulator 15 so as to be substantially integral with the center conductor 11, and a head cap 17 is provided at the upper end of the upper insulator 14. An insulating medium 18 such as insulating oil or gas is sealed inside these structural members such as the support fitting 13 and upper and lower insulator tubes 14 and 15, and gaskets 19 and 2 are provided at the joints of the respective structural members.
0, 21, 22, 23, and 24 are interposed.
Then, by screwing the lock nut 25 disposed on the upper part of the head cap 17 into the threaded part 11a formed on the upper part of the center conductor 11 and tightening this, the insulating medium 18 is assembled as one body while maintaining its sealing function. It will be done.

Note that the center conductor 11 is made of a conductive material such as aluminum alloy, stainless steel, and copper alloy. When the center conductor 11 is heated to a temperature higher than the maximum permissible temperature during use of the bushing and thermally expanded, the center conductor 11 is screwed into the threaded portion 11a of the center conductor 11 with a tensile strength within the elastic limit of the center conductor. The matched lock nut 25 is tightened. and,
The elasticity of the center conductor 11 when the temperature returns to room temperature allows the components to be assembled together to form the bushing.

In this case, heating the center conductor 11 to a temperature higher than the maximum allowable temperature means that even if the maximum allowable temperature is reached during use of the bushing, the assembly of each component will not loosen due to thermal expansion of the center conductor. This is how it was done. In other words, the amount of thermal expansion of the center conductor when heated above the maximum allowable temperature is greater than that when the maximum allowable temperature is reached, so even if the center conductor reaches the maximum allowable temperature, the amount of thermal expansion of the center conductor that corresponds to the difference in the amount of thermal expansion The elastic force is maintained, thereby preventing the assembly of each component from becoming loose. However, even if the center conductor 11 is heated to a temperature higher than the maximum allowable temperature, it is not preferable to heat it too much due to the pressure applied when the center conductor 11 contracts. This point will be explained in detail.

Generally, the maximum allowable temperature for this type of bushing is determined to be 150°C or less, assuming a maximum ambient temperature of 45°C + a temperature rise of 65°C. Therefore, if the lock nut 25 is tightened while the center conductor 11 is heated to a temperature higher than the maximum allowable temperature, for example, 115 DEG C. to 120 DEG C., and the temperature is returned to room temperature again, a temperature change of about 100 DEG C. will occur in the center conductor 11.

On the other hand, the length of the center conductor 11 used in this type of bushing is designed to be in the range of 1000 mm to 6000 mm. Here, when the material of the center conductor 11 is aluminum (Al), the length change △l due to a temperature change of 100°C is the linear expansion coefficient of aluminum, which is 23.6 × 10 ^-6
Then, Δl=23.6×10 ^- ₆ ×100×(1000 to 6000) (mm) From the formula, Δl=2.36 to 14.16 (mm). The pressing force generated by this length change Δl is as follows. That is, a pipe-shaped conductor is generally used for the center conductor 11 of this type of bushing, and its cross-sectional area is approximately 730 mm ² when the length is 1000 mm, and when the length is 6000 mm.
It is approximately 2830mm ² , and the pressing force P is determined by the following formula.

P = 6.3 × 10 ³ × (conductor cross-sectional area) × (length change) / (conductor length) (Kg) As a result, the pressing force P generated by the above-mentioned length change △l is P = 11 to 42 tons. . On the other hand, this pressing force P
The compressive strength of the receiving insulator meets the standard ASTM.C407−
5700 ~ in a test using a test piece according to 58
6600Kg/ ^cm2 , but even in the product state it is 1000Kg/cm2
It has been confirmed that the amount is around 2000Kg/ ^cm2 . In this type of bushing, the minimum cross-sectional area of the insulator tube is the length
In the case of 1000 mm, it is about 86 cm ² , and in the case of 6000 mm, it is about 245 cm ² , and the fracture strength of the insulator due to compression is at least 86.
~245 tons. Therefore, there is a margin of about 6 times the breaking strength of the insulator against the pressing force of 11 to 42 tons generated by a temperature change of 100° C. in the center conductor 11, and there is no fear that the insulator will break.

In general, in order to maintain the assembly of the insulator tube sufficiently by the tensile elastic force of the center conductor, the center conductor 11 is heated to a temperature 10 to 15 degrees Celsius higher than the maximum allowable temperature, although this varies depending on the material of the center conductor 11. Tightening is sufficient.

As shown in FIG. 3, the head cap 17 provided at the top of the upper insulator is covered with a cover plate 17a via a gasket 23 in order to seal the opening at the top. The tightening force of the lock nut 25 is transmitted to the head cap 17. In addition, inside the center conductor 11, a solid conductor shown by a two-dot chain line or a cable 26 whose stranded wires are coated with an insulating material is inserted in order to conduct electricity, and the upper end of the cable 26 is inserted inside the upper end of the center conductor 11. The other end is connected to a lower clamp 16 which also serves as a lower terminal. The cable bolt 27 is fixed inside the center conductor 11 through a pin 28 to prevent rotation. Further, this cable bolt 27 is provided with a threaded portion 27a, and the terminal cap 29 is screwed onto the terminal cap 29.
A gasket 32 is interposed between the lock nut 25 and the lock nut 25 to maintain a seal. In addition, in the above example,
The pipe-shaped center conductor 11 has been described for the case in which it does not share the current supply, but as shown in FIG. The gasket 2 is inserted into the threaded portion 30a of the gasket 2.
3. A lock nut 25 may be screwed together via the cover plate 17a and the gasket 24.

As described above, according to the present invention, each component including the head cap is tightened and assembled together by the tensile elasticity of the center conductor, so there is no need for a compression spring or a spring as in the conventional structure.
Furthermore, since the head cap does not house any compression springs or the like inside it, its size can be determined solely by its original function, so it can be made smaller. Therefore, according to the present invention, the structure of the head is simplified, and it is also smaller and lighter, so it is possible to provide a bushing that has excellent seismic strength and is cost-reduced.

[Brief explanation of the drawing]

Fig. 1 is a partially sectional front view showing a conventional bushing, Figs. 2 and 3 show the bushing of the present invention, Fig. 2 is a partially sectional front view, and Fig. 3 is a partially sectional front view showing main parts. , FIG. 4 is a partially sectional front view showing another embodiment of the present invention. 11, 30... Center conductor, 12... Insulating layer, 1
3...Supporting metal fittings, 14...Air side insulator pipe, 15...
...Insulating medium side insulator pipe, 16...Lower clamp, 1
7...Head cap, 18...Insulating medium, 19,
20, 21, 22, 23, 24, 29... Gasket, 25... Lock nut, 27... Cable bolt, 28... Pin, 29... Terminal cap.

Claims (1)

[Scope of utility model registration request] In a structure in which an air side insulator tube and an insulating medium side insulator tube are provided on both sides of a support fitting, and a center conductor provided with an insulating layer is housed inside them together with an insulating medium, the end of the insulating medium side insulator tube one end of the center conductor is fixed to an end clamp provided at the center conductor, and a threaded portion formed at the other end of the center conductor is made to protrude from a head cap provided at the head of the air side insulator tube. The center conductor has a tensile strength within the elastic limit of the center conductor in a state where the center conductor is thermally expanded by heating it to a temperature approximately 10 to 15 degrees Celsius higher than the maximum allowable temperature allowed during use of the bushing. A lock nut is tightened on the threaded portion of the head cap, the air side insulator, the support fitting, and the insulating medium side insulator are pressed together by the tensile elastic force of the center conductor, thereby assembling the head cap, the air side insulator, and the insulating medium side insulator as one unit. Butsuthing to do.