JPS6226244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling method for increasing the power transmission capacity of electric cables used in power transmission and distribution lines.

Various methods have been devised to increase the power transmission capacity of cables, but they can be broadly divided into external (direct or indirect) cooling, which cools the cable from the outside, and internal direct cooling, which directly cools the cable conductor. Divided. The latter type of internal direct cooling attempts to directly eliminate conductor loss, which accounts for most of the cable's total heat loss, and is the most effective cooling method that can be expected to significantly increase capacity. The present invention relates to this internal direct cooling method, which has effects and features not found in conventional methods.

Now, conventionally considered internal direct cooling methods include (1) water cooling, (2) insulating oil circulation cooling, (3) refrigerant circulation cooling, and (4) heat pipe applied cooling.
Either method has many problems and cannot be applied to ultra-high voltage distance power transmission cables. The first method, water cooling, uses water with good heat removal ability, so the cooling effect is large, and the viscosity is low, so the fluid pressure drop is small, so it is an effective cooling method.
It can be used to cool cables up to about 20KV, but 275 [KV] is currently most needed.
There are problems when applying this method to ultra-high voltage cables such as 500 [KV]. This is because if water leaks, there is a risk of immediate insulation breakdown of the cable. The second biggest problem with insulating oil circulation cooling is that because the oil passage diameter cannot be made extremely large due to the cable structure, the fluid pressure drop due to the high viscosity insulating oil becomes large, and the cooling section length is 300 mm. ~500
The problem is that it is limited to about [m]. In the third type of refrigerant circulation cooling, the mechanical elements used for refrigerant circulation are complicated, so a self-cooling type that does not use these is currently being devised, but this type consists of liquid Freon and its boiling gas. Although it is intended for natural circulation of a gas-liquid mixed two-phase flow, it cannot be used for long distances because the circulation speed is slow and problems remain, especially when there are height differences in the route. The fourth method, heat pipe applied cooling, is originally limited to the effective length of the heat pipe itself, which is several meters at most, so it cannot be applied to long-distance routes with large differences in elevation.

Although an overview of conventionally devised methods has been described above, it is difficult to apply any of the methods to ultra-high voltage long-distance power transmission lines. The present invention aims to provide a cooling method that does not have the above-mentioned drawbacks and can be applied to any line.

The present invention will be explained in detail below based on the drawings of one embodiment.

FIG. 1 shows a cross section of a cable used as an application example of the present invention. However, illustrations of insulators, metal sheaths, etc. outside the conductor are omitted. A gas passage pipe 3 made of a porous pipe made of metal or synthetic resin is inserted into the airtight metal pipe 2 provided in the center of the cable conductor 1, and a gas passage pipe 3 made of a porous pipe made of metal or synthetic resin is inserted into the gap between the airtight metal pipe 2 and the gas passage pipe 3. is filled with liquid refrigerant 4. The porosity and pipe thickness of the gas passage pipe 3 are selected according to the static pressure and viscosity of the refrigerant, and are designed so that the liquid refrigerant hardly passes therethrough, but the boiled refrigerant gas easily passes therethrough. That is, it is assumed that only the refrigerant gas 5 exists inside the gas passage pipe 3.

For example, when using Freon as a refrigerant, the gas passage pipe 3
For example, if a bronze filter made of sintered metal with a maximum particle diameter of 4 to 8 [μ] and a pipe thickness of 2 to 3 [mm] is used, there will be a difference of hundreds of times in the amount of permeation between refrigerant gas and liquid. Go out and achieve your goal. Of course, depending on the size of the height difference, the maximum permeable particle size is 1 to 4.
[μ], a bronze filter of about 8 to 20 [μ] may also achieve the purpose. An example of forming a continuous gas passage pipe 3 using this sintered metal body is shown in FIG.

By connecting relatively short sintered metal bodies 6 one after another through airtight synthetic resin pipes 7, refrigerant gas 5
A long gas passage pipe 3 is formed to transport the gas.

Next, FIG. 3 shows an example of a cable cooling system. A cable 8 is laid along a long distance route with height differences, and both ends of the cable 8 are treated with cable terminal parts 9 to 9'. As already explained, in the center of the conductor (not shown) of the cable 8 is an airtight metal pipe 2.
There is further a gas passage pipe 3 arranged therein. The hermetic metal pipe 2 and the gas passage pipe 3 are connected to a lower cable end 9'.
The cable terminals 9 are each individually and completely sealed, and the cable terminals 9 located at a higher level are individually connected to the pipes 10 and 11, respectively. A reservoir 12 and a condenser 13 are installed as a refrigerant cooling device at a position higher than the cable terminal part 9, the pipe 10 is connected to the lower part of the reservoir 12, and the pipe 11 is fixed at a position close to the upper part of the reservoir 12. Further, a pipe 14 is connected to the condenser 13,
Its end is fixed in the upper position of the reservoir 12. After all piping is completed, airtight metal pipe 2, gas passage pipe 3, piping 10, 11, 14,
After degassing the inside of the reservoir 12 and condenser 13, the liquid refrigerant 4 is filled. That is, the gap between the airtight metal pipe 2 and the gas passage pipe 3 is filled with refrigerant, and the liquid level in the reservoir 12 is maintained at a specified position.

When the cable 8 is energized, the heat generated in the conductor (not shown) immediately passes through the airtight metal pipe 2.
This is transmitted to the refrigerant 4 in contact with this. The refrigerant absorbs latent heat of vaporization and boils and vaporizes. When this refrigerant gas reaches the surface of the gas passage pipe 3, it enters the gas passage pipe 3 at a speed corresponding to the pressure difference between the inside and outside of the gas passage pipe 3, and further passes through the piping 11 to the reservoir 12.
The released heat is also liquefied in the condenser 13 through the pipe 14 and stored in the lower part of the reservoir 12. At this time, the liquid refrigerant 4 also leaks slightly into the gas passage pipe 3 depending on its static pressure, but
Since this vaporizes immediately, it does not block the gas passage of the gas passage pipe 3. Therefore, the gas passage pipe 3 is secured as a passage for the refrigerant gas with an extremely high heat transfer coefficient, so that even if there are height differences in the cable route, or even if the cable route is a fairly long distance, cooling can be carried out extremely effectively. In addition, since the liquid refrigerant 4 is constantly and automatically filled into the airtight metal pipe 2 depending on the liquid level of the reservoir 12, there is no need for any mechanical elements for refrigerant circulation or piping for the refrigerant return path. self-cooling is possible.

The above explanation assumes that a refrigerant cooling device is installed only at the cable end at a high level, but if the cable route is an extremely long distance, installing a refrigerant cooling device at both ends of the cable will save even more space. A system with high cooling efficiency can be implemented.

As explained in detail above, the present invention is a completely new method that provides a complete self-cooling system that does not require refrigerant circulation, and is an extremely effective invention.

[Brief explanation of the drawing]

Fig. 1 is a partially omitted cross-sectional view of the cable used in the present invention, Fig. 2 is a longitudinal cross-sectional view showing the connecting part of the gas passage pipe, and Fig. 3 is an explanatory diagram showing one embodiment of the cable cooling system. It is. 1...Cable conductor, 2...Airtight metal pipe,
3... Gas passage pipe, 4... Liquid refrigerant, 5...
Refrigerant gas, 6... Sintered metal body, 7... Airtight synthetic resin pipe, 8... Cable, 9... Cable terminal, 10... Piping, 11... Piping, 12... Reservoir, 13... Condensation Vessel, 14...Piping.

Claims (1)

[Claims] 1 Install an airtight pipe in the center of the cable conductor,
Furthermore, a gas passage pipe through which boiled refrigerant gas can easily pass is inserted into the interior, the gap between both pipes is filled with liquid refrigerant, and the refrigerant gas, which boils and vaporizes due to the heat generated by the conductor, is guided into the gas passage pipe, A method of cooling the cable by liquefying this heat through a cooling device installed at the cable end.