JPH0250684B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tunnel gas insulated power transmission line that is easy to install and has high reliability.

(Prior technology) Due to the increasing demand for electricity, urban congestion, and the difficulty of constructing overhead power transmission towers for aesthetic reasons, the cableization of power transmission systems, especially ultra-high voltage lines and ultra-super high voltage lines (500kv), has become necessary.
are beginning to be converted into cables. However, regular oil-immersed (OF) or polyethylene (CV) cables cannot transmit power over long distances. Therefore, in order to cope with this, a bare conductor 3 is laid in the center of the metal conduit 1 with a spacer 2, as shown in the sectional view shown in FIG. 6
A conduit aerial power transmission line filled with a high dielectric strength gas such as sulfur fluoride gas at 3 to 4 atmospheres has been proposed.
It is already in practical use at 275Kv or higher. This type of cable is capable of transmitting large amounts of power compared to conventional OF cables, and has superior electrical characteristics.
This is a powerful means for ultra-high voltage power transmission.

(Problems with the Prior Art) On the other hand, in order to withstand the high pressure of the sealed gas, this system has no choice but to use a thick metal tube, that is, a non-flexible metal tube, as the metal conduit. As a result, not only is the price high, but it cannot be wrapped around a drum and transported to the installation site like conventional cables, and its unit length is at most 16 m, which is suitable for transport by means such as trucks.
It has to be about the same length. This not only makes transporting a hassle, but also requires careful and tedious work to construct a long line to prevent dust from entering the short metal tubes, which could reduce their dielectric strength (electrical properties). Must be. In addition, metal pipes are expensive, and installation costs are high.
In addition, since metal pipes are not flexible, they are vulnerable to earthquake disasters and tend to interfere with the stable supply of electricity.

Therefore, in order to eliminate this drawback, a so-called flexible conduit aerial power transmission line, which can be transported by winding a metal tube around a drum in the same way as conventional cables, has been studied. However, in order to satisfy these requirements by following the conventional method as is, it is necessary to make the metal tube thinner so that it can be wound around a drum, for example, so that it can be used with flexibility.
However, in this case, the insulation distance between the conductor and the metal conduit becomes shorter, so in order to maintain the same insulation performance as before, the pressure of the insulating gas must be increased. As a result, various dust and impurities in the enclosed gas prevent the high dielectric strength gas from exhibiting its original insulation performance.
It has not been put into practical use at ultra-high pressure or ultra-super high pressure levels.

(Purpose of the Invention) The present invention solves problems such as difficulty in imparting flexibility to metal conduits, difficulty in laying them to prevent dust from entering high dielectric strength gas, and increased cost of metal conduits. The object of the present invention is to provide a tunnel gas-insulated power transmission line that can solve all the problems of the above-mentioned prior art at once.

(Means of the present invention for solving the problems) The present invention provides a fixed method for conventional power transmission lines of this type, in which an insulating gas is sealed in a metal conduit as thin as possible under high pressure. The present invention was developed based on the idea that a gas-insulated power transmission line that satisfies the above requirements can be realized by breaking away from the above-mentioned concept.The present invention will now be described with reference to examples.

(Example) FIG. 2 is a sectional view of an example of the present invention,
In the figure, 5 is a metal container corresponding to a conventional metal conduit, 4
are internal spaces filled with high dielectric strength gas, 3A, 3B,
3C is a conductor (the insulating spacer is not shown), and the present invention is characterized by the following points.
The sealing pressure of the high dielectric strength gas into the internal space 4 of the metal container 5 is set to a pressure slightly higher than atmospheric pressure, for example, 0.1 to 1 atm higher than atmospheric pressure. The metal container 5 has a polygonal cylindrical shape, for example, a rectangular cylindrical shape, which is made up of a set of flat walls formed by bonding band-shaped flat metal plates having a thickness that can withstand the sealing pressure of the high dielectric strength gas, and the size of the metal container 5 is set to a required insulation distance. It is at the point where it is formed to have .

(Operations and Effects of the Invention) By significantly lowering the sealing pressure of high dielectric strength gas compared to the conventional method, the influence of dust and impurities, which is the biggest drawback of ordinary conduit aerial power transmission lines, is reduced. Therefore, there is almost no need to pay attention to these matters. Since the wall thickness of the metal container can be reduced approximately in proportion to the filling pressure, the wall thickness of the metal container can be made significantly thinner than that of conventional metal conduits, and there is less need to consider gas leakage at joints. . Therefore, by transporting long thin metal plates wound around a drum (the top, bottom, left and right side walls of the metal container) to the installation site and welding them using welding technology, which has recently made remarkable progress, it is relatively easy to do this. A flexible container can be constructed. At this time, there is no problem with the intrusion of dust and impurities, which is a decisive difference from conventional conduit aerial power transmission lines. Furthermore, by laying a flexible conductor in this,
It is easier to change direction than with conventional metal conduits, and it is possible to construct a line that is resistant to earthquake disasters. Furthermore, since the insulation distance between the metal container and the conductor is longer, the insulation spacer is also much easier to design and manufacture than in the past.

Furthermore, since the metal container is large enough for people to enter and exit the container at a power transmission voltage of 500 KV, for example, it is easy to install conductors using insulating spacers, and the installation cost can be lower than that of conventional containers. Furthermore, since the internal space is large, the conductor can be made thicker, and the current capacity can be increased compared to conventional devices.

In addition, as shown in FIG. 2, the container 5 has a square cross section,
Three conductors 3A, 3B, 3C are placed in the center of the interior.
According to the calculation results for a three-phase transmission line with a grid voltage of 500 KV arranged in a corner, the length and width of the container H ₁ =
By setting H ₂ = 2000 mm, conductor diameter D = 300 mm, and distance L from the middle of the metal container = 500 mm, the voltage of conductor _3A = 1800 KV, and the voltage of conductors 3B and 3C.
Even in the case of severe surge conditions with V ₂ = V ₃ = 900KV, the maximum electric field is at most 94KV/cm,
It has been found that the dielectric strength can be sufficiently satisfied by using sulfur hexafluoride gas at a sealed pressure of 0.1 to 0.2 atm (dage pressure).

As is clear from the above description, the present invention has various advantages over conventional gas insulation, such as being unaffected by dust and impurities, being easy to install, and being resistant to earthquakes. It can be used as a power transmission line and will make a particularly large contribution to the realization of ultra-high voltage underground power transmission lines of 275KV, 500KV or higher.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional pipeline aerial power transmission line, and FIG. 2 is a sectional view of an embodiment of the present invention. 1...Metal conduit, 2...Insulating spacer, 3...
Conductor conduit, 4... Insulating gas-filled space, 5... Metal container.

Claims (1)

[Claims] 1. A tunnel gas insulated power transmission line in which a high dielectric strength gas is sealed in a metal container in which a conductor is laid using an insulating spacer in the inner space, and the pressure of the high dielectric strength gas is set to 0.1 to 1 below atmospheric pressure. At the same time as setting the atmospheric pressure to a high value, the metal container is formed into a polygonal cylindrical shape having a size that satisfies a desired insulation distance, and is formed by joining a band-shaped flat metal plate having a thickness that can withstand the pressure of the enclosed high dielectric strength gas. A tunnel gas insulated power transmission line characterized by reducing the effects of dust and impurities and being easy to install.