JPH04337613A - Gas insulated current transformer - Google Patents

Abstract

PURPOSE:To improve insulation performance without requiring a large insulator supporting the container for the main body of a current transformer. CONSTITUTION:A metal container 2 is supported by an insulator 2, and a main body of the current transformer is contained in the container 2. A supporting pipe 10 is arranged in the insulator pipe 1, and a secondary coil unit 7 on the main unit of the current transformer is fixed on the upper end of the supporting 10. A shield for mitigating electric field 21 is arranged near the upper end of the insulator 1, and a capacitor cone 22 is formed between the supporting pipe 10 and the shield 21 so that the electric field is prevented from concentrating on the upper part of the insulator to improve the insulation performance. The supporting pipe is supported on the container 2 by means of the capacitor cone and the shield 21 to enhance the mechanical strength.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas-insulated current transformer having a current transformer body housed in a container filled with an insulating gas.

0002

2. Description of the Related Art A gas-insulated current transformer has a current transformer body consisting of a primary conductor and a secondary coil unit housed in a container filled with an insulating gas such as SF6 gas. 2
The secondary coil unit includes a ring-shaped iron core surrounding a primary conductor and a secondary coil distributedly wound around the iron core, and the iron core and the secondary coil are housed in a shield case made of a non-magnetic metal. . The potential of the shield case is fixed to ground potential.

As this type of current transformer, one shown in FIG. 3 has been proposed. In the figure, 1 is an insulator tube fixed on a base B, and 2 is a metal container supported on the upper end of the insulator tube 1. Inside the container 2 is a secondary coil unit 7 having a structure in which a primary conductor 3 and a secondary coil 5 wound around a ring-shaped iron core 4 surrounding the primary conductor are housed in a hollow annular shield case 6. The main body of the current transformer consisting of is housed.

A conical insulating spacer 8 that shares an axis with the insulating tube is attached to the bottom plate of the container 2, and the shield case 6 is connected to a tubular through conductor 8a provided through the insulating spacer via a connecting fitting 9. is fixed.

A metal support tube 10 is provided passing through the axial center of the insulator tube 1, and the lower end of this support tube 10 is fixed to the base B. The upper end of the support tube 10 is connected to the through conductor 8a of the insulating spacer, and the 2
A second lead wire is passed through the pipe 10 and introduced into a terminal box 11 provided inside the base B.

One end 3a of the primary conductor 3 passing through the axis of the secondary coil unit 7 is led out to the outside through an airtight lead-out part 12 attached to the container 2, and the other end 3b is led out through an insulating lead-out part 12 attached to the container 2. It hermetically passes through the spacer 13 and is led out. The airtight lead-out portion 12 has electrical conductivity, and has 1
The secondary conductor 3 is electrically connected to the container 2 via an airtight lead-out portion 12. This keeps the container 2 at the same potential as the primary conductor 3. Primary terminals 14 are provided at both ends of the primary conductor 3,
14 is installed. There is S in the insulator tube 1 and container 2.
F6 gas is sealed at a predetermined pressure.

[0007] An annular electric field mitigation shield 15 is provided at the upper end of the insulator tube 1, and the electric potential of this shield 15 is fixed to the container 2. A pressure relief device 16 is provided at the top of the container 2 .

In the above current transformer, a spacer S for forming a gas flow path is inserted between the flange portion 8b of the insulating spacer 8 and the bottom plate of the container 2, and the spacer S is inserted between the flange portion 8b of the insulating spacer 8 and the bottom plate of the container 2. A gas flow path is formed between the container and the bottom surface, and the gas space in the container 2 and the gas space in the porcelain tube 1 are communicated through the gas flow path.

[0009]

[Problems to be Solved by the Invention] In the conventional gas insulated current transformer shown in FIG. The distribution of E is as shown in FIG. 5, and the concentration of the electric field at the top of the insulator tube is considerably large. As a result, the upper part of the insulator becomes a weak point in the insulation, making it difficult to design the insulation.

[0010] In order to avoid this, it is necessary to increase the height of the insulator tube and increase its diameter, which causes the problem of increasing the size of the current transformer.

An object of the present invention is to provide a gas insulated current transformer that improves insulation performance by alleviating the concentration of electric field at the upper part of the insulator tube without using a large insulator tube.

0012

[Means for Solving the Problems] The present invention provides a metal container that supports a metal container at the upper end of an insulator tube, houses a current transformer main body within the metal container, and that is provided with a shaft core inside the insulator tube. This relates to a gas-insulated current transformer in which a secondary coil unit of the current transformer body is supported at the upper end of a support tube.

In the present invention, an annular electric field mitigation shield is arranged along the inner surface of a portion near the upper end of the insulator tube, and the shield is fixed to the container, and a gap between the outer periphery of the support tube and the electric field mitigation shield is arranged. In addition, a capacitor cone consisting of an insulating film and a plurality of intermediate electrodes is formed.

[0014]

[Operation] By forming a capacitor cone between the electric field mitigation shield provided at the top of the insulator tube and the support tube as described above, when using the same insulator tube as before, the distribution of the electric field at the top of the insulator tube is almost uniform. It can be done. Therefore, the insulation performance can be improved without increasing the size of the insulator.

Furthermore, since the upper part of the support tube supporting the heavy secondary coil unit can be supported against the container via the capacitor cone and the shield for mitigating the electric field, the secondary coil unit is protected from vibrations during transportation. This makes it possible to prevent the current transformer from swinging, thereby increasing the mechanical strength of the support portion of the current transformer main body.

[0016]

[Embodiment] Fig. 1 shows an embodiment of the present invention, in which B is a base, 1 is an insulator tube whose lower end is fixed on the base, and 2 is a metal container fixed to the upper end of the insulator tube 1. It is. A cylinder 20 made of FRP is disposed inside the insulator tube 1 to prevent the insulator tube 1 from exploding and scattering when a flashover accident occurs inside and the gas pressure inside increases. A support tube 10 is arranged along the central axis of the insulator tube 1, and the lower end of the support tube 10 is fixed to the base B. A hollow annular shield case 6 is disposed within the container 2 with its axis oriented horizontally, and the shield case 6 is fixed to the upper end of the support tube 10. Inside the shield case 6, a plurality of secondary coils 5, which are uniformly distributed and wound in a toroidal manner around a ring-shaped iron core 4, are arranged side by side.
The secondary lead wires drawn out from these secondary coils are
It passes through the support tube 1 and is introduced into a secondary terminal box provided inside the base B.

The iron core 4, the secondary coil 5, and the shield case 6 constitute a secondary coil unit 7. A portion of the shield case 6 is electrically separated by an insulator so as not to form one turn surrounding the iron core 4.

A primary conductor 3 extending horizontally through the axial center of the shield case 6 is also housed inside the container 2, and one end 3a of the primary conductor 3 is provided on the side wall of the container 2. The other end 3b passes through an insulating spacer 13 attached to the side wall of the container and is led out to the outside. The airtight holding part 12 has electrical conductivity,
One end of the primary conductor 3 is electrically connected to the container 2 through the hermetic holding part 12. Primary terminals 14, 14 are attached to both ends of the primary conductor 3. At the top of container 2,
A pressure relief device 16 is attached, and SF6 gas is sealed in the gas container 2 and the insulator tube 1 at a predetermined pressure.

A substantially cylindrical electric field mitigation shield 21 is provided concentrically with the support tube 10 inside a portion near the upper end of the insulator tube 1 . As shown in FIG. 2, this electric field mitigation shield 21 has a flange portion 21a at the upper end, and the flange portion 21a has mounting holes 21b on the outer periphery and a large number of holes on the inner periphery. A pore 21c is provided respectively. The flange portion 21a is brought into contact with the bottom surface of the container 2, and the bolts inserted into the mounting holes 21b are attached to the container 2.
An electric field mitigation shield 21 is fixed to the container 2 by being screwed into a screw hole provided in the bottom plate of the container 2.

In the present invention, the electric field mitigation shield 2
A condenser cone 22 is formed between the inner peripheral surface of the support tube 1 and the outer peripheral surface of the support tube 10 . This capacitor cone is
An insulating film 23 and a plurality of intermediate electrodes 24 are layered and wound, and the laminated thickness is formed so that it gradually becomes thinner toward the lower end of the porcelain tube and toward the current transformer main body. As the insulating film 23, a film of polyethylene terephthalate or polypropylene suitable for use in an insulating gas can be used. Further, as the intermediate electrode 24, aluminum foil, carbon paper, or the like is used.

The upper part of the support tube 10 is a condenser cone 22.
It is supported by an electric field mitigation shield 21 via. The gas space in the container 2 and the gas space in the porcelain tube 1 are communicated through a vent hole 21c provided in the electric field mitigation shield.

When the capacitor cone 22 is formed as described above, the distribution of the electric field E near the porcelain tube becomes as shown in FIG. FIG. 4 shows a case where the same insulator tube as in FIG. 5 is used, and the electric field does not concentrate on the upper part of the insulator tube, and the electric field distribution can be made close to uniform.

[0023]

As described above, according to the present invention, since the capacitor cone is formed between the electric field mitigation shield provided on the upper part of the insulator tube and the support tube, even when the same insulator tube as the conventional one is used, It is possible to prevent the electric field from concentrating on the upper part of the insulator tube, and to make the distribution of the electric field near the upper part of the insulator tube substantially uniform. Therefore, the insulation performance can be improved without increasing the size of the insulator.

Further, according to the present invention, since the upper part of the support tube supporting the heavy secondary coil unit can be supported with respect to the container via the capacitor cone and the electric field mitigation shield, the secondary coil unit This has the advantage that the current transformer can be prevented from shaking due to vibrations during transportation, and the mechanical strength of the support portion of the current transformer body can be increased.

[Brief explanation of the drawing]

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

FIG. 2 is a perspective view showing a part of the electric field mitigation shield used in the embodiment of FIG. 1;

FIG. 3 is a longitudinal sectional view showing a conventional gas insulated current transformer.

FIG. 4 is a vertical cross-sectional view showing the electric field distribution near the insulator tube in FIG. 1;

5 is a vertical cross-sectional view showing the electric field distribution near the insulator tube in FIG. 3; FIG.

[Explanation of symbols]

1...Insulator pipe, 2...Container, 3...Primary conductor, 4...Iron core, 5...2
Secondary coil, 6... Shield case, 7... Secondary coil unit, 10... Support tube, 21... Shield for electric field relaxation, 22...
capacitor cone.

Claims (1)

[Claims] 1. A metal container is supported at the upper end of the insulator tube, a current transformer main body is housed in the metal container, and the current transformer body is housed in the metal container, and the In a gas-insulated current transformer that supports a secondary coil unit of a current transformer main body, an annular electric field mitigation shield is arranged along the inner surface of a portion near the upper end of the porcelain tube, and the shield is attached to the container. A gas insulated current transformer, characterized in that a capacitor cone consisting of an insulating film and a plurality of intermediate electrodes is formed between the outer periphery of the support tube and the electric field mitigation shield.