JPH0250685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to gas insulated lines, and particularly to miniaturization thereof.

[Prior art]

In recent years, gas-insulated switchgear has become widely used due to its compact size, non-polluting properties, and labor-saving maintenance properties, and as a result, power transmission lines are also becoming gas-insulated. Ta. In other words, a conductor supported by a solid insulator is placed inside a container.
Gas-insulated lines, which are insulated by filling them with a gas with excellent insulation performance such as SF ₆ , have come into use.

In this gas-insulated line, as with conventional gas-insulated switchgear, in order to prevent the dielectric strength from decreasing due to the decrease in gas density due to condensation and liquefaction of SF ₆ gas at low temperatures,
Designs have been made with gas pressures up to 5-6 atmospheres.

However, with such gas pressure, the size of the gas insulated line becomes large, and the cost of the gas insulated line and the tunnel to house it become excessive, which significantly increases the construction cost of the gas insulated line, creating a barrier to practical use. It was becoming.

[Summary of the invention]

Therefore, in order to overcome these conventional difficulties, the underground temperature where the gas insulated line is laid does not drop as much as the surface temperature in winter (for example, about 15 degrees Celsius).
Focusing on this, it is an object of the present invention to attempt to reduce the size of a gas insulated line, with one condition being that the gas pressure is increased to, for example, about 15 atmospheres.

In the above-mentioned high-pressure gas-insulated line, the insulation performance of the gas space can be improved as the gas pressure increases, and the desired goal can be achieved, but the insulation performance of the solid insulator supporting the conductor is insufficient. Various improvements are required in terms of performance. As part of this invention, the electric field distribution in the solid insulator is made almost uniform in the radial direction, and specifically,
The diameter of the container at the part where the annular insulating support that is interposed between the container and the conductor and supports the conductor is provided,
The diameter of the annular insulating support is larger than that of the portion of the container where the annular insulating support is not provided, and a plurality of holes are formed in the annular insulating support, concentrically with the support and increasing in diameter as they are closer to the conductor. It has a ring-shaped electrode embedded in it.

[Embodiments of the invention]

FIG. 1 is a longitudinal sectional view showing an embodiment of a gas insulated line according to the present invention. In the figure, 1 is a conductor, 2 is an annular insulating support that supports this conductor 1, and both ends 2A in the axial direction are shown in FIG. , 2B, and has a substantially truncated conical shape. This support 2 supports the conductor 1, and the inner circumferential surface 2C serving as the supporting surface is in close contact with the conductor 1 over its entire axial and circumferential length, and the outer circumferential surface of the conductor 1 and the support No space is created between the entire inner circumferential surface 2C of No.2. 3A and 3B are small-diameter tubular containers surrounding the conductor 1 in the part where the annular insulating support 2 is not provided, and 4A and 4B are the supports 2 in the part where the support 2 is provided.
and a large-diameter tubular container surrounding the conductor, each in the shape of a hollow truncated cone, with each end connected to the small-diameter container 3 above.
It has the same diameter as A and 3B, and is airtightly connected to the small diameter containers 3A and 3B by welding or the like. Reference numeral 5 denotes an annular metal connection flange member, the entire inner circumferential surface of which 5A is in close contact with the outer circumferential surface of the annular insulating support 2;
No space is formed between the support body 2 and the support body 2. The other ends of the large-diameter containers 4A, 4B are hermetically connected to the outer peripheral surface of the connecting flange member 5 by welding or the like. 6A, 6B...6N
is for the conductor 1 within the annular insulating support 2,
In addition, a large number of annular metal electrodes are buried concentrically at a predetermined distance from each other, and the one with the smaller diameter The electrode, for example 6A, is formed to have a longer axial length than the smaller electrode, for example 6B, and all electrodes 6A, 6B...6N are connected to the annular insulating support 2. This is done so that there is no space between them. 7 is the conductor 1, the annular insulating support 2, and the containers 3A, 3B, 4.
An insulating space 8 in the container formed by A and 4B is a high-pressure insulating gas having excellent insulating properties such as SF ₆ gas sealed in this insulating space.

The insulating gas in the gas insulated bus bar currently used has a gas pressure of about 4 to 6 atmospheres, but in the example of the present invention, SF ₆ gas of 15 atmospheres is used. For this reason, the dielectric strength in gas increases to about three times that in the case of 4 to 6 atmospheres, but the dielectric strength of a normal insulating support will only improve by about 1.5 times with the same diameter even if extreme design is performed. . Therefore, the diameter of the container in the insulating support section is reduced to approximately 1/1.5, and instead of suppressing the increase in electrolytic strength of the insulating support to a value that can withstand pressure, the diameter of the container in the gas insulating section is reduced to approximately 1/3 that can withstand pressure. reduce, i.e.
It has been found that it is better to make the insulating support part a large-diameter container, and to make the gas insulating part, where no insulating support is provided, a small-diameter container.

Now, in the present invention, as described above, the insulating support 2 has a structure in which concentric electrodes 6A, 6B, . . . , 6N are integrated with a solid insulator. The concentric electrodes 6A, 6B, . . . , 6N have substantially the same capacitance between them, making the potential distribution from the conductor 1 to the container substantially uniform. In the absence of this electrode, the electric field becomes higher as it approaches the conductor 1, resulting in an electric field distribution as shown in FIG. 2a. In Figure 2a, 9 indicates the electric field strength, and as is clear from the figure, the electric field strength (9MAX) near the conductor 1 is the maximum, and the electric field strength (9MIN) near the container 4 is the minimum. ing. That is, the closer the conductor 1 is from the container 4, the greater the electric field strength becomes.

On the other hand, in the case of the embodiment of the present invention shown in FIG. 1, as shown in FIG. 2b, the electric field strength 9 near the conductor 1 and the electric field intensity 9 near the container 4 are the same. It's getting old. That is, the electric field strength is constant from the container 4 to the conductor 1 (in the radial direction).

Since the withstand voltage design is performed under the condition that the highest electric field portion does not exceed the allowable electric field value, the container diameter becomes considerably small in the case of a uniform electric field as in the present invention. for example,
In the above example, if a normal insulating support without electrodes 6A, 6B...6N for improving the electric field was used, the large diameter part of the container would have been nearly twice as large as the small diameter part of the container. In the case of an insulating spacer with electrodes 6A, 6B, . . . , 6N, the size can be expanded by about 1.3 times.

The maximum electric field E when a voltage E is applied to a concentric cylinder with an inner diameter D ₁ of the container 4 and an outer diameter D ₂ of the conductor 1 is E=2V/D ₂ e _o D ₁ /D ₂ , and D ₁ /D ₂ is generally Since a value close to e=2.72 results in the lowest electric field and miniaturization, the container 4 and conductor 1 of the gas insulated line are often designed with this ratio.
However, in the above example, in the large-diameter parts 4A and 4B of the container, the diameter of the conductor 1 remains almost the same and only the container becomes larger, so D ₁ /D ₂ increases by 4 to 5 times, and the electric field concentration in the conductor part becomes particularly large. Therefore, as in the present invention, the effect of equalizing the electric field strength in the radial direction by using concentric cylindrical electrodes is great. Further, by reducing the size of the gas insulated line in the radial direction, it is possible to reduce not only the size of the line itself but also the tunnel in which it is installed. The economic effect is very large.

〔Effect of the invention〕

As described above, the present invention provides that the diameter of the container in the portion where the annular insulating support interposed between the container and the conductor and supporting the conductor is provided is the diameter of the container in the portion where the support is not provided. A plurality of annular electrodes having a diameter larger than the diameter of the container and concentric with the support and having a larger diameter closer to the conductor are buried in the support, and the electrodes are arranged in a radial direction in the support portion. Since the electric field distribution is made almost uniform, the gas insulated line can be made smaller without impairing its reliability, and furthermore, the tunnel etc. that accommodate the gas insulated line can be constructed economically. It is.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention;
FIG. 2a is a diagram showing the electric field distribution when the present invention is not applied, and FIG. 2b is a diagram showing the electric field distribution according to one embodiment of the present invention. In the figure, 1 is a conductor, 2 is an annular insulating support,
3A and 3B are small diameter containers, 4A and 4B are large diameter containers, 6A, 6B...6N are annular electrodes, and 8 is a high pressure insulating gas.

Claims (1)

[Claims] 1. In a gas insulated line in which a conductor is placed in a container filled with high-pressure insulating gas, an annular insulating support is provided between the container and the conductor to support the conductor. The diameter of the container of the part,
A plurality of annular electrodes are provided within the support, the diameter of which is larger than the diameter of the container in the portion where the support is not provided, and which is concentric with the support and has a larger diameter as it approaches the conductor. 1. A gas insulated line, characterized in that the line is buried and the electric field distribution in the radial direction is substantially uniform in the support portion.