JPH05243064A - Gas insulated transformer - Google Patents

Abstract

PURPOSE:To facilitate an insulation design of a gas insulated transformer and hence facilitate the miniaturization of the same by providing a plurality of cylindrical electric field moderation shields surrounding concentrically a second lead containing pipe. CONSTITUTION:There are provided a plurality of cylindrical electric field moderation shields 20A, 20B, and 20C surrounding concentrically a secondary lead containing pipe 5 by supporting a secondary coil unit 12 on the upper end of the secondary lead containing pipe 5. The upper end of the electric field moderation shields are arranged in a pressure container 3 while the lower ends of the same are arranged in a gas pipe 2. The electric field moderation shields 20A-20C are located more upward than the upper end of the shields located inwardly while the lower ends of the shields located inwardly are located more downward than the lower end of the shields located outwardly. Hereby, an electric field distribution on the side of the external surface of the glass pipe is made uniform to avoid the concentration of an electric field. Thus, the radial dimension of the glass pipe is more reduced than the prior art is, and hence predetermined insulation performance is ensured even if the height of the glass pipe is lowered.

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 using an insulating gas such as SF ₆ gas as an insulating medium.

[0002]

2. Description of the Related Art A gas-insulated current transformer has a main body of a current transformer equipped with a primary conductor and a secondary coil wound around a ring-shaped iron core surrounding the primary conductor, and is filled with SF ₆ gas or the like. It has a structure of being housed in a container.

FIG. 6 shows a conventional current transformer of this type used in a circuit for ultrahigh voltage. In FIG. 6, 1 is a base, 2 is a base 1, and the lower end is connected airtightly. Insulator pipe 3 is a pressure vessel composed of a bell jar type container body 3A and a bottom plate 3B for closing the lower end opening of the vessel body.
The bottom plate 3B of the pressure vessel 3 is connected to and supported by the upper end of the porcelain insulator 2.

A hole 3b1 is formed in the central portion of the bottom plate 3B of the pressure container so as to penetrate the inside of the porcelain insulator 2 and the inside of the pressure container 3, and an insulating spacer 4 is attached to the periphery of the hole 3b1. A secondary lead storage pipe 5 extending in the axial direction of the porcelain bushing is arranged at the center of the porcelain bushing 2, the lower end of the pipe being the base 1 and the upper end being the lower end of a hollow through conductor 6 provided in an insulating spacer 4. Respectively connected to.

Reference numeral 7 denotes a primary conductor arranged in a state of being oriented in a direction orthogonal to the axis of the porcelain bushing 2. One end of this primary conductor 7 is supported on the side wall of the pressure vessel 3 via an insulating spacer 8. It is led to the outside through the insulating spacer, and the other end of the primary conductor is led to the outside through the airtight holding portion 9 having conductivity. Primary terminals 10 and 11 connected to the main circuit are attached to both ends of the primary conductor 7.

Reference numeral 12 is a secondary coil unit arranged in the pressure vessel 3, and this secondary coil unit is a primary conductor 7
A plurality of secondary coils 14 wound in a toroidal shape are arranged around a ring-shaped iron core 13 surrounding the
Hollow annular shield case 15 with the following coil
It has a structure housed inside. The shield case 15 of the secondary coil unit 12 is connected to and supported by the upper end of the through conductor 6 of the insulating spacer 4.

The secondary lead derived from the secondary coil is 2
It is guided into the secondary terminal box 16 provided in the base 1 through the next lead storage pipe 5. In order to make the electric field distribution outside the insulator tube uniform, a cylindrical electric field mitigating shield 17 is attached to the upper end of the insulator tube 2.

The pressure vessel 3 and the porcelain tube 2 are filled with SF ₆ gas at a predetermined pressure. Although not specifically shown,
A gas flow hole that connects the inside of the pressure vessel 3 and the inside of the porcelain bushing 2 is provided in the mounting portion of the insulating spacer 4, so that the inside of the pressure vessel and the inside of the porcelain bushing are kept at the same pressure.
Further, on the top of the pressure vessel 3, there is provided a pressure release device 18 which breaks and releases the gas inside when the pressure inside the pressure vessel exceeds a set value.

[0009]

In the conventional gas-insulated current transformer, since only one electric field mitigating shield 17 is provided, when this current transformer is used in an ultrahigh voltage circuit,
It was difficult to sufficiently relax the electric field on the outer surface of the porcelain insulator (the surface in contact with the outside air). Therefore, in order to obtain a predetermined insulation performance, it is necessary to increase the height of the porcelain bushing and increase the outer diameter of the porcelain bushing, which inevitably results in a large-sized current transformer.

An object of the present invention is to provide a gas-insulated current transformer in which the electric field on the outer surface side of the porcelain insulator is relaxed to improve the insulation performance and the height and diameter of the porcelain insulator can be reduced. To do.

[0011]

According to the present invention, a porcelain insulator having a lower end fixed to a base, a pressure vessel supported on an upper end of the porcelain insulator, and a secondary arranged axially in a central portion of the porcelain insulator. The lead storage pipe, the primary conductor provided in the pressure vessel in a direction orthogonal to the central axis of the porcelain insulator and supported on the pressure vessel, and wound around a ring-shaped iron core surrounding the primary conductor. And a secondary coil unit having a structure in which the secondary coil is housed in a shield case together with the iron core and disposed in the pressure vessel, and a secondary terminal is drawn from the secondary coil and passed through a secondary lead housing pipe. 2 guided in the box
The present invention relates to a gas-insulated current transformer having a secondary lead.

In the present invention, the secondary coil unit is supported on the upper end of the secondary lead storage pipe. Then, a plurality of cylindrical electric field mitigating shields concentrically surrounding the secondary lead storage pipe are provided, and the upper ends of the plural electric field mitigating shields are arranged in the pressure vessel and the lower ends are arranged in the porcelain tube. The multiple electric field mitigation shields have the upper end of the inner shield located above the upper end of the outer shield and the lower end of the inner shield below the lower end of the outer shield. Place it in the opened condition.

The respective upper ends of the plurality of electric field mitigating shields are formed so as to have a trumpet shape which spreads toward the secondary coil unit side toward the secondary coil unit side. It is preferable to form the opening angle so as to be larger than the opening angle of the upper end of the electric field relaxation shield located inside.

It is preferable to support the plurality of electric field relaxation shields as follows. That is, the innermost electric field mitigating shield is supported by the secondary lead storage pipe through the inner insulating support. An inter-shield insulating support is inserted between the plurality of electric field mitigating shields, and the plurality of electric field mitigating shields are connected and supported through the inter-shield insulating support. In this case, the capacitance between the electric field mitigating shields is adjusted by the occupation ratio of the inter-shield insulating support in the gap between the electric field mitigating shields.

[0015]

As described above, when a plurality of cylindrical electric field mitigating shields concentrically surrounding the secondary lead housing pipe are provided, the electric field distribution on the outer surface side of the porcelain insulator is made uniform and the concentration of the electric field is avoided. Therefore, even if the radial dimension of the porcelain insulator is reduced and the height of the porcelain insulator is reduced as compared with the conventional case, a predetermined insulation performance can be obtained.

When the upper end of each electric field mitigating shield is formed in a trumpet shape, the projecting length of the plurality of electric field mitigating shields into the pressure vessel can be shortened, so that the current transformer The height can be reduced.

In order to prevent the concentration of the electric field outside the porcelain tube and to improve the insulation performance, the electrostatic capacitance between the electric field relaxation shields and the static electricity between the innermost shield and the secondary lead storage pipe are used. It is necessary to adjust the capacitance to an appropriate value, but if the electric field mitigating shields are made to face each other substantially only through the insulating gas, adjust the capacitance between them to the length of the shield. Since it has to be performed only by the gap, it is difficult to finely adjust the capacitance.
In particular, in order to make the electric field distribution on the outer surface of the porcelain insulator uniform, it is desirable to lengthen the axial length of the shield, but if the length of the electric field relaxation shield is increased, the electrostatic discharge between the electric field relaxation shields is increased. It becomes difficult to adjust the capacity,
Design for uniform electric field distribution outside the porcelain tube becomes difficult. On the other hand, as described above, a structure in which an inter-shield insulating support is inserted between a plurality of electric field mitigating shields and a plurality of electric field mitigating shields are interconnected and supported through the inter-shield insulating support is provided. Then, the capacitance between the electric field mitigating shields can be adjusted by adjusting the space factor of the insulating support material between the shields in the gap between the electric field mitigating shields. Also, the capacitance between the shields can be set to an appropriate value, and the optimum design for making the electric field distribution on the outer surface of the porcelain insulator uniform can be easily performed.

[0018]

1 and 2 show an embodiment of the present invention. In this embodiment, the insulating spacers 4 provided in the example of FIG. 6 are removed, and the upper end of the secondary lead storage pipe 5 is removed. The secondary coil unit 12 is supported by the. In the present embodiment, a plurality of cylindrical electric field mitigating shields 20A, 20B and 20C concentrically surrounding the secondary lead storage pipe 5 are provided, and the upper ends of the plurality of electric field mitigating shields are inside the pressure vessel 3. The lower ends are arranged in the porcelain bushing 2. The plurality of electric field mitigating shields 20A to 20C are arranged such that the upper end of the inner shield is located above the upper end of the outer shield, and the lower end of the inner shield is located below the lower end of the outer shield. It is arranged in a state of being positioned below. Shield 20A-20
The end portions 20a1 to 20c1 at the upper end of C are formed to have a ring-shaped cross-section with a sufficiently large curvature. In addition, the terminal ends 20a2 to 20 at the lower ends of the shields 20A to 20C
c2 is formed to have an arcuate cross-sectional shape with a sufficiently large curvature.

In FIG. 2, electric field relaxation shields 20A-2
A plurality of curves shown from between 0C to the lower part in the pressure vessel 3 show potential distributions, and the numerical values such as 90% and 70% attached to these curves and 0 attached to the secondary lead storage pipe. The numerical value of% indicates the potential of each part when the potential of the pressure vessel 3 whose potential is fixed to the primary conductor 7 is 100%.

The electric field mitigating shields 20A to 20C are made of a light metal such as aluminum or a plastic material such as FRP whose surface is subjected to a conductive treatment, or a conductive plastic, and are insulated from each other. It is supported on the porcelain bushing 2 or the secondary lead storage pipe by an appropriate means such as inserting a support.

When a plurality of electric field mitigating shields are concentrically provided between the secondary lead storage pipe and the porcelain insulator as in the above-mentioned embodiment, compared with the case where only one electric field mitigating shield is provided, Since the electric field distribution around the can be made more uniform, a predetermined insulation strength can be obtained even if the diameter and height of the porcelain insulator are reduced.

As in the embodiment shown in FIGS. 1 and 2, when the upper ends of the electric field mitigating shields 20A to 20C are cylindrical, and the cross-sectional shape of the terminal end of the upper end of each shield is ring-shaped. In order to secure an insulation distance between the end portions of the shields 20A to 20C,
It is necessary to increase the distance between the 0C end portions 20a1 to 20c1. Therefore, the protrusion length of the shields 20A to 20C into the pressure vessel 3 becomes long, and the height of the pressure vessel becomes high. In order to avoid this, as shown in FIGS. 3 and 4, the upper ends of the shields 20A to 20C are formed to have a trumpet-like shape that widens toward the secondary coil unit 12 side, It may be formed so that the opening angle of the upper end of the electric field mitigating shield located outside is larger than the opening angle of the upper end of the electric field mitigating shield located inside. Further, in this case, in order to prevent the potential distribution from being disturbed, the cross-sectional shape of the end portion 20c1 at the upper end of the outermost shield 20C has a sufficiently large curvature to smoothly curve and extend outward in the radial direction. (For example, arcuate), and the inner shields 20A and 20B
The cross-sectional shape of the end portions 20a1 to 20c1 at the upper end of is preferably a crushed circle (for example, an elliptical shape).

In FIG. 4, a plurality of curves shown from between the shields to the lower part in the pressure vessel show the potential distribution, and the numerical value (%) attached to each curve is when the potential of the pressure vessel is 100%. The electric potential of each part is shown. As is clear from FIG. 4, when the upper ends of the shields 20A to 20C are in a divergent shape, the upper end of the shield has a shape that follows the potential distribution, so that the potential gradient can be reduced. In addition, the pressure vessel 3 at the upper end of the shields 20A to 20C
Even if the protrusion length inward is shortened, the insulation distance between the end portions 20a1 to 20c1 can be increased, so that the height of the pressure vessel 3 can be reduced and the size of the current transformer can be reduced. be able to.

In order to prevent the concentration of the electric field outside the porcelain insulator 2 and improve the insulation performance, the electric field mitigating shield 20 is used.
It is necessary to adjust the electrostatic capacitance between A to 20C and the electrostatic capacitance between the shield 20C and the secondary lead storage pipe 5 to appropriate values, respectively. However, as shown in FIG. 1 or FIG. When 20 C are made to face each other substantially only through SF ₆ gas, the capacitance between them must be adjusted only by the length of the shield and the facing gap. Adjustment is difficult. In particular, in order to make the electric field distribution on the outer surface of the porcelain insulator 2 uniform, it is desirable to increase the length of the shield in the axial direction. However, if the length of the electric field relaxation shield is increased, the static electricity between the electric field relaxation shields is reduced. It becomes difficult to adjust the capacitance.

The embodiment shown in FIG. 5 solves this problem. In this embodiment, the space between the upper and lower ends of the innermost electric field mitigating shield 20A and the secondary lead storage pipe 5 is provided. The ring-shaped inner insulating supports 21 and 21 are arranged in the inner side of the secondary lead storage pipe 5. Between the electric field mitigating shields 20A and 20B, annular inter-shield insulating supports 22 and 22 are arranged near the upper end and the lower end of the shields 20A and 20B, respectively, and the shield 20B serves as the shield support 20A. It is connected and supported by. Between the electric field mitigating shields 20B and 20C, annular inter-shield insulating supports 23, 23 are arranged near the upper end and the lower end of the shields 20C and 20C, respectively, and the shield 20C is provided by these insulating supports. 20B
It is connected and supported by.

The inner insulating support 21 and the inter-shield insulating supports 22 and 23 are made of an insulating material having a high dielectric constant (such as tetrafluoroethylene resin (trade name: Teflon), polyacetal copolymer resin (trade name: Duracon), epoxy resin). Dielectric material). Further, the shields 20A to 20C are preferably made of a light conductive metal such as aluminum.

As described above, the electric field mitigating shield 20
When the inter-shield insulating support is inserted between A and 20B and between 20B and 20C, by adjusting the space factor (axial length) of the inter-shield insulating support in the gap between the electric field mitigating shields, Electric field mitigation shield 20
The capacitance between A and 20B and between 20B and 20C can be easily adjusted, and the capacitance between the shield 20A and the secondary lead storage pipe 5 can also be easily adjusted. Adjustment of these capacitances is performed by the shields 20A to 20C.
This can be done by adjusting the occupancy rate of the insulating support regardless of the length in the axial direction of, so set the length of each electric field relaxation shield and the capacitance between the shields to appropriate values. The optimum design for making the electric field distribution on the outer surface of the insulator tube uniform can be easily performed.

In the above embodiment, three electric field mitigating shields are provided, but a plurality of electric field mitigating shields may be provided, and two or four or more electric field mitigating shields may be provided.

[0029]

As described above, according to the present invention, since a plurality of cylindrical electric field mitigating shields concentrically surrounding the secondary lead storage pipe are provided, the electric field distribution on the outer surface side of the porcelain insulator is uniform. Thus, the concentration of electric field can be avoided. Therefore, even if the diametrical dimension of the porcelain insulator is reduced and the height of the porcelain insulator is reduced compared to the conventional case, a predetermined insulation performance can be obtained and the gas-insulated current transformer can be downsized.

Further, according to the invention described in claim 2, since the shape of the upper end of each electric field mitigating shield is formed into a trumpet shape, the projection length of the plurality of electric field mitigating shields into the pressure vessel is shortened. Therefore, there is an advantage that the height of the pressure vessel can be reduced and the current transformer can be further downsized.

According to the third aspect of the present invention, an inter-shield insulating support is inserted between the plurality of electric field mitigating shields, and the plurality of electric field mitigating shields are mutually connected via the inter-shield insulating support. In order to adjust the electrostatic capacitance between the electric field mitigating shields by adjusting the space factor of the inter-shield insulating support in the gap between the electric field mitigating shields, This has the advantage that the length of each electric field relaxation shield and the capacitance between the shields can be set to appropriate values to facilitate an optimum design for making the electric field distribution on the outer surface of the porcelain insulator uniform.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of an essential part showing an enlarged upper portion of the embodiment of FIG.

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

FIG. 4 is an enlarged sectional view of an essential part showing an enlarged upper portion of the embodiment of FIG.

FIG. 5 is a vertical sectional view showing still another embodiment of the present invention.

FIG. 6 is a vertical sectional view showing a conventional gas circuit breaker.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Insulator tube, 3 ... Pressure vessel, 5 ... Secondary lead storage pipe, 7 ... Primary conductor, 8 ... Insulating spacer, 12 ...
Secondary coil unit, 13 ... Ring-shaped iron core, 14 ... 2
Next coil, 20A to 20C ... Shield for electric field relaxation, 21
... Inside insulating support, 22, 23 ... Inter-shield insulating support.

Claims (3)

[Claims] 1. A porcelain insulator having a lower end fixed to a base, a pressure vessel supported on an upper end of the porcelain insulator, a secondary lead storage pipe arranged in a central portion of the porcelain insulator along an axial direction, and the porcelain insulator. A primary conductor that is provided in the pressure vessel and is supported by the pressure vessel in a direction orthogonal to the central axis of the coil, and is wound around a ring-shaped iron core that surrounds the primary conductor. A secondary coil having a structure in which a secondary coil is housed in a shield case together with the iron core is arranged in the pressure vessel.
A secondary coil unit and a secondary lead drawn from the secondary coil and guided into the secondary terminal box through the secondary lead storage pipe are provided, and insulating gas is filled in the insulator tube and the pressure vessel. In the gas-insulated current transformer, the secondary coil unit is supported on the upper end of the secondary lead storage pipe, and a plurality of cylindrical electric field mitigation shields concentrically surrounding the secondary lead storage pipe are provided. The upper ends of the plurality of electric field mitigating shields are arranged in the pressure vessel and the lower ends thereof are arranged in the porcelain insulator, and the plurality of electric field mitigating shields are arranged such that the upper end of the inner shield is the upper end of the outer shield. The shield is positioned above the lower end of the shield, and the lower end of the inner shield is positioned below the lower end of the outer shield. Insulation current transformer. 2. An upper end of each of the plurality of electric field mitigating shields is formed so as to have a trumpet shape that spreads toward the secondary coil unit side toward the secondary coil unit side. The gas insulated current transformer according to claim 1, wherein the opening angle of the upper end is formed to be larger than the opening angle of the upper end of the electric field mitigating shield located inside. 3. The innermost electric field mitigating shield among the plurality of electric field mitigating shields is supported by the secondary lead storage pipe via an inner insulating support, and is provided between the plurality of electric field mitigating shields. An inter-shield insulation support is inserted in the inter-shield insulation support, and a plurality of electric field mitigation shields are mutually connected and supported through the inter-shield insulation support, and the inter-shield insulation support in the gap between the electric field mitigation shields. 3. The gas-insulated current transformer according to claim 1, wherein the capacitance between the electric field mitigation shields is adjusted by the occupation ratio of the gas insulation current transformer.