JPS598007B2 - gas butsing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention supports a bushing, especially a center conductor, with an insulator tube, and includes an air grounding shield ring and a cylindrical ground electrode inside the insulator tube in order to control the potential gradient on the ground side of the lower part of the insulator tube. The present invention relates to a gas bushing having a gas bushing.

The conventional gas bushing has a central conductor 1 as shown in Figure 1.
In order to reduce the potential gradient between the insulator tube 2 and the lower flange 3 of the insulator tube 2, a cylindrical grounding shield 4 concentrically surrounds the center conductor 1 in the gas inside the insulator tube 2 and the insulator tube 2 concentrically in the air outside the insulator tube 2. An annular grounding shield 5 is arranged to surround the capacitor, and its dimensions are selected so as to obtain a predetermined withstand voltage performance.

6 indicates a metal case of an electrical device or the like to which the bushing is attached.

FIG. 2 shows equipotential lines during field mapping of the bushing. As can be seen from Figure 2, gas bushings are generally designed so that the internal insulation of the insulator tube is higher than the external insulation of the insulator tube.

That is, the insulation performance of the bushing is determined externally. In other words, it has been limited by the surface potential gradient of the grounding shield in the air and the potential gradient of the surface of the porcelain tube near the ground side. Therefore, in order to improve the withstand voltage characteristics using a standard type insulator tube, it is possible to lower the potential gradient on the surface of the insulator tube by moving the equipotential lines toward the high voltage side, but this equipotential line By moving the cylindrical grounding shield 4 inside the insulator to the high pressure side, the surface potential gradient of the insulator on the air side is alleviated, but the creeping potential gradient inside the insulator and the cylindrical shape are reduced. The local potential gradient at the end of the ground shield 4 increases. Therefore, the balance between internal and external insulation coordination deteriorates.
The present invention moves the equipotential lines toward the high voltage side by arranging a potential distribution control shield with an intermediate potential between the center conductor and the ground shield, without moving the cylindrical ground shield inside the insulator tube toward the high voltage side. The purpose of this invention is to obtain a gas bushing that can reduce the potential gradient on the surface of the porcelain tube and stabilize the insulation. In order to achieve this object, the gas bushing according to the present invention has a structure in which cylindrical insulators are distributed on the circumference in the axial direction of the cylindrical grounding shield inside the insulator tube to support the cylindrical shield at an intermediate potential. The third
The configuration of the present invention will be explained with reference to FIGS. FIG. 4 shows the mounting structure of the intermediate potential shield within the two-dot chain line in FIG. A cylindrical internal grounding shield 21 is fixed inside the flange 13 of the single porcelain tube 12 into which the center conductor 11 is inserted.

Reference numeral 14 denotes an air grounding shield which is fixed to the flange 13 via a support pipe 15.

Reference numeral 16 denotes a metal case that supports the bushing by the flange 13, and is, for example, a case for a gas cylinder or a disconnector.

An intermediate potential shield 25 is attached to the upper part of the cylindrical internal grounding shield 21 via a cylindrical insulator 31, and the details thereof will be explained with reference to FIG. 4. The intermediate potential shield 25 is constructed integrally with a mounting hardware 26 provided at its upper end, and the connecting shield 21 and mounting hardware 22 provided at its upper end are also constructed integrally in the same manner as described above.

A plurality of cylindrical insulators 31 are distributed on the circumference between these two mounting hardware 26, 22, and are attached with tightening bolts 27, so that the intermediate potential shield 25 is positioned on the inside. To support. The shield 21 is fixed to the inner surface of the metal case 16 with bolts 24 via a grounding shield mounting plate 23, and thereby the shield 21
is electrically connected to the flange 13. The potential of the shield 25 is determined by the ratio of the capacitance between the conductor 11 and the shield 25 and the capacitance between the shield 25 and the grounded shield 21. Therefore, the overlap b amount A of both shields 21 and 25
It can be considered that it changes depending on the By providing the intermediate potential shield 25 according to the present invention, the equipotential lines during field mapping in FIG. It becomes possible to keep the surface potential low.

Also, considering the withstand voltage characteristics when water is poured onto the surface of the insulator,
Although the potential distribution on the surface of the insulating tube changes due to the influence of falling water droplets, it has the advantage that the potential distribution is fixed by the internal intermediate potential shield. By arranging the intermediate potential shield inside the X, the air grounding shield outside the insulator tube does not need to be a large diameter shield ring as is provided in ordinary gas bushings.

As a method of supporting a shield at an intermediate potential, it is also possible to disperse the supports in the radial direction of the porcelain tube, that is, in the direction perpendicular to the center conductor, as described in, for example, Japanese Patent Application Laid-Open No. 49-113194. However, in the case of the support structure having this configuration, it is difficult to ensure creepage distance when the support is an insulator. In order to secure a predetermined creepage distance, the inner diameter of the porcelain tube must be increased, and furthermore, it is very difficult to construct a specific structure for fixing the support to the inner surface of the porcelain tube. In order to firmly fix the support to prevent it from falling, a large amount of space is required for the fixing structure, and the inner diameter of the insulator tube must be made increasingly thicker. On the other hand, according to the configuration described in the above publication, the ground shield and the intermediate potential shield are mechanically independent, and each is supported by a separate support.
It is supported and fixed on the inner surface of the insulator tube. Therefore, in particular, the fixing of the intermediate potential shield is a structure that can only be adopted for insulators that have a multi-stage structure in which unit insulators are stacked. In contrast, in the present invention, an insulator is disposed on the circumference of the high potential side end of the grounding shield so as to extend in the axial direction of the shield, and the intermediate potential shield is supported and fixed at the other end of the insulator. The ground shield and intermediate potential shield are integrated through an insulator, and the center conductor and insulator are arranged so that their axes are approximately parallel to each other, so there is sufficient creepage distance. , it is not necessary to increase the inner diameter of the insulator tube, and it is easy to assemble.

Moreover, in order to raise the intermediate potential to about 20(f) to 60%, the intermediate potential shield should naturally be located near the inclined part of the porcelain tube.

Therefore, in order to reliably control the potential distribution, the cylindrical insulator may be installed at an angle along the inclination of the porcelain tube with respect to the axial direction of the shield. This embodiment is shown in FIG. Here, B is the inclination angle. Furthermore, by stacking the porcelain in multiple stages, it is possible to improve the potential distribution on the surface of the porcelain tube. As explained above, according to the present invention, a cylindrical insulator arranged extending in the axial direction of the cylindrical internal grounding shield is used as a structure for supporting the intermediate potential shield. By adopting a simple structure in which the intermediate potential shield is supported by the insulator, a long creepage insulation distance can be obtained without increasing the inner diameter of the insulator tube, and the stability of the insulation in the gas can be measured.

In addition, since an intermediate potential shield is installed, the grounding shield on the air side can also be made small, reducing costs.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. A single insulator tube, a center conductor inserted into the insulator tube,
a cylindrical grounding shield disposed around the outer periphery of the central conductor within the insulator tube and fixed to a metal object at ground potential; an air grounding shield electrically connected to the cylindrical grounding shield and provided outside the insulator tube; an insulator having one end fixed to the high potential side end of the cylindrical ground shield and disposed toward the high potential side so that the other end extends in the axial direction of the ground shield;
a cylindrical electric field control shield having an intermediate potential, one end of which is fixed to the other side of the insulator, and the other end of which is located between the grounding shield and the center conductor and facing the grounding shield; Consists of gas bushing. 2. The gas bushing according to claim 1, wherein the insulator is constructed by distributing a plurality of cylindrical insulators. 3. The gas bushing according to claim 1, wherein the cylindrical electric field control shield is stacked in multiple stages. 4. The gas bushing according to claim 1, wherein the insulator is attached to the end of the cylindrical shield so as to be inclined along the inclined surface of the inner surface of the insulator tube.