JPS6016689B2 - butsing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to bushings mainly used in medium-voltage switch gears of 10 to 30 KV or less, and in particular to improved bushings that are easy and inexpensive to manufacture and prevent deterioration of partial discharge characteristics. .

Pushings used in switchgear and the like are generally intended to completely separate completely insulated conversions and to be used as a lead-out section for leading out lead wires to the outside.

Therefore, in order to improve the performance and reduce the cost of devices such as switchgear, it is desired to manufacture inexpensive bushings with excellent electrical characteristics. Therefore, with a bushing of 3 V or less, there is no need to control the electric field by using a capacitor-type bushing with adjustable potential distribution, and even a single-type bushing with a simple structure can satisfy the particularly problematic partial discharge characteristics. I can do it. Therefore, typical conventional pushing will be explained using FIGS. 1 and 2. The pushing shown in FIG. 1 has an insulating layer 2 formed around the conductor 1 by casting an insulating layer material such as an epoxy resin onto the conductor 1. In this case, a shield 3 made of wire mesh or the like is provided inside the insulating layer 2 to alleviate the electric field on the grounding side of the bushing, and if necessary, a ring 4 is provided at the end of the shield 3, and the ring 4 is embedded together with the mounting bracket 5. This is what I did. Further, a bolt 7 is attached to a flange-shaped attachment end 6 located approximately at the center of the outer peripheral surface of the insulating layer 2.
The mounting plate 8 is attached by. On the other hand, the shield 3 is electrically connected to a bolt 7 through a mounting fitting 5, and is further connected to a mounting plate 8 through this bolt 7.
It is connected to the. Therefore, with the bushing having such a configuration, the electric field concentrated on the mounting plate 8 on the ground side is two to three times larger than the electric field on the conductor 1 on the high voltage side.
Since the shield 3 and ring 4 are embedded in the insulating layer 2 to alleviate the electric field as described above, it is possible to prevent the electric field on the ground side from concentrating on the mounting plate 8.

In this case, the equipotential lines obtained by field mapping of electric field relaxation have a distribution as shown in FIG. As is clear from this figure, the shield 3 and ring 4 widen the iso-fin level line 9 within the insulating layer 2 to alleviate electric field concentration, and in particular suppress the occurrence of partial discharge. However, in order to obtain equipotential lines 9 as shown in FIG. 2 in such bushings, it is necessary to maintain a constant dimension from the surface of the insulating layer 2 to the shield 3 embedded in the insulating layer 2. There is,
Therefore, when forming the insulating layer, the shield 3 and ring 4 are
Sufficient care and some kind of consideration are required, as if it were implanted in a state where it was forgotten. Therefore, in the past, the shield 3 and ring 4 were made manually, and when forming an insulating layer by casting insulating material, the mold was divided into 3 to 4 parts and the set position of each embedded part such as the shield 3 and ring 4 was determined. I tried to perform the pillar shape in several steps without moving.
However, when the shield 3 and the ring 4 are made manually or the mold is divided into 3 or 4 parts for casting, there are major problems in terms of speeding up the casting process and reducing costs. Therefore,
In order to deal with this problem, as shown in Figures 3 and 4, embedded parts such as the shield 3, ring 4, and mounting bracket 5 are removed, and an insulating layer is formed by one casting. There is a structure that is designed to increase the speed of a columnar type.

That is, as shown in FIG.
A grounding layer 14 such as conductive paint or metallicon is provided over the range necessary for mitigating the electric field on the surface of the insulating layer on both sides of the flange-shaped attachment part 13 approximately in the center, and a low-resistance paint 15 containing carbon is provided at both ends of the grounding layer 14. This is applied to alleviate the electric field concentrated on the mounting plate 16.
Therefore, if the bushing has such a configuration, the equipotential lines 17 will be distributed as shown in FIG. 4, and the electric field on the ground side can be prevented from concentrating on the ring plate 14 as in the case described above. . Furthermore, ``When casting the insulating layer, the conductor 11 is simply embedded, so it can be formed in one casting process, making it possible to increase the speed and reduce the cost.However, with this type of bushing, the surface of the insulating layer 12 Since the ground layer 14 is provided to alleviate the electric field, the low-resistance paint 15 and the ground layer 14 peel off from the edges when attaching the bushing or cleaning the surface, resulting in deterioration of partial discharge characteristics. The purpose of this invention is to form a vertical edge layer around a conductor in a western shape, provide grooves on both sides of the grounding end of the edge layer with the necessary spacing for mitigating the electric field, and By providing a conductive ground layer over the entire surface of the insulating layer from the inside of the insulating layer through the mounting end to the other groove to ease the electric field on the ground side, manufacturing is easy without deteriorating partial discharge characteristics. An object of the present invention is to provide an inexpensive bushing.Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 5, the bushing body is constructed by forming an insulating layer 22 around the conductor 21 by forming grooves of an insulating material such as epoxy resin on the conductor 21, and approximately central part of the surface of the insulating layer 22. Attach the bolt 2 to the flange-like mounting end 23 having
4 or the like, attach the mounting plate 25. In addition, grooves 26 having a small semicircular cross-section at the bottom are provided on the surface of the insulating layer on both sides of the mounting end 23 with an interval necessary for electric field relaxation. Then, over the entire surface of the insulating layer from inside one groove through the mounting end to inside the other groove,
A ground layer 27 is provided by applying a conductive material or metallicon. Therefore, in the case of a single type bushing configured in this way, since the conductive layer 27 is formed from one side of the groove 26 whose bottom has a small semicircular cross section to the other, the distribution of the equipotential lines 28 is as follows. As shown in Figure 6, insulating layer 2
The grooves 26 and 26 are substantially parallel to each other in the range corresponding to both grooves 26, 26 inside the grooves 2, and it is possible to prevent the electric field from concentrating on the mounting plate 25 on the ground side.

Furthermore, since the ends of the ground layer 27 are located in the grooves 26 provided on the surface of the insulating layer 22, both ends of the ground layer 27, which are the parts that are most likely to peel off, are protected. It is possible to prevent the ground layer 27 from peeling off from its ends during installation or surface cleaning, and it is possible to prevent deterioration of partial discharge characteristics due to peeling of the ground layer, which has been a problem in the past. As described above, according to the present invention, an insulating layer is formed around the conductor by casting, and a distance necessary for electric field relaxation is provided on both sides of the mounting end on the ground side of the surface of the insulating layer, so that the bottom part has a cross-sectional shape. A small semicircular groove is provided, and a conductive ground layer is provided over the entire surface of the insulating layer from inside one groove through the mounting end to the other side, making it easy to manufacture and low cost. It is possible to provide a bushing in which the ground layer is not peeled off and the partial discharge characteristics are not degraded when the bushing is attached or the surface is cleaned.

[Brief explanation of the drawing]

Fig. 1 is a half-sectional view showing a conventional bushing, Fig. 2 is a partially enlarged view of Fig. 1, Fig. 3 is a half-sectional view showing a conventional bushing different from Fig. 1, and Fig. 4 is a half-sectional view showing a conventional bushing. FIG. 5 is a half-sectional view showing a bushing according to an embodiment of the present invention, and FIG. 6 is a partially enlarged view of FIG. 5. 21...Conductor, 22... Insulating layer, 23... Attachment end, 24... Bolt "2
5... Mounting plate, 26... Groove, 27... Ground layer. 〆・1 Figure * 2 Figure O 8 Figure 4 Figure 5 Figure O 6 Style

Claims (1)

[Claims] 1 The bushing body is constructed by forming an insulating layer around the conductor by casting, and the bottom part has a small semicircular cross section with an interval necessary for electric field relaxation on both sides of the mounting plate attachment end on the surface of the insulating layer. A bushing characterized in that a groove is provided in the shape of a shape, and a conductive ground layer is provided on the surface of the insulating layer from inside one groove, passing through the attachment end and into the other groove.