JPS5851365B2 - Radial flow cooling method for internally cooled cable lines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for radial flow cooling of internally cooled cable lines.

As shown in FIG. 1, a conductor 1 has an intra-conductor refrigerant passage 2, an insulating layer 3 on the outer periphery of the conductor 1, a refrigerant passage 4 directly under the sheath,
A pump 8 pressurizes and sends a refrigerant made of insulating oil cooled by a heat exchanger 7 to the intra-conductor refrigerant passage 2 of the internal cooling cable line 6 in which cable sheaths 5 are sequentially provided, and this refrigerant is fed to the intra-conductor refrigerant passage 2. In the process of flowing the conductor 1 and the insulating layer 3 in the radial direction of the insulating layer 3,
The refrigerant discharged to the refrigerant passage 4 directly under the sheath is collected at the end of the refrigerant passage 4 directly under the sheath, returned to the heat exchanger 7, cooled, and supplied to the pump 8 again for circulation. Radial flow cooling methods are known.

The refrigerant passage 4 directly under the sheath connects the cable sheath 5 and the insulating layer 3.
It is formed by taking advantage of the narrow gap between the

The key to this radial flow cooling method is that the pressure difference between the pressure inside the refrigerant passage 2 inside the conductor and the pressure inside the under-sheath refrigerant passage 4 increases the amount of oil in the radial direction of the insulating layer 3, that is, the amount of heat removed. In order to determine the differential pressure, g
If it can be maintained at a constant predetermined value, it becomes possible to extend the cooling span.

To achieve this, it is necessary to reduce the pressure drop in each longitudinal direction of the refrigerant passage 2 within the conductor and the refrigerant passage 4 directly under the sheath.
0 Reducing the pressure drop in the longitudinal direction of the conductive refrigerant passage 2 can be achieved relatively easily by increasing the inner diameter of the conductive refrigerant passage 2.

For example, in the 27 SKV class, the inner diameter of the conductive refrigerant passage 2 of the current OF cable (internal cooling cable) is 14 m.
Setting the distance to 60m can be a sufficient solution.

The pressure drop in the longitudinal direction of the under-sheath refrigerant passage 4 could be prevented by widening the gap between the cable sheath 5 and the insulating layer 3, or by making the peaks of the goofle sheath 50 waves higher. There are problems with the manufacturing technology and mechanical properties of the cable, and as mentioned above, it is not possible to obtain a value equivalent to the flow resistance of the conductive refrigerant passage 2 when the inner diameter is set to 50 to 60 concave φ.
The pressure loss was quite large.

Therefore, as shown in FIG. 2, the pressure difference △P between the pressure A in the conductive refrigerant passage 2 and the pressure B in the refrigerant passage 4 immediately below the sheath gradually decreases along the longitudinal direction, and as this occurs, the radial pressure of the insulating layer 3 The amount of refrigerant permeation in the direction, that is, the amount of heat removed, is reduced, and the cooling span length of the internal cooling cable line 6 can be prevented from increasing.

An object of the present invention is to reduce the pressure loss in the refrigerant passage directly under the sheath as much as possible, to equalize the amount of refrigerant permeated through the insulating layer in the longitudinal direction of the line, and to increase the cooling span length. It is possible to provide a radial flow cooling method for the internal cooling goofle line.

Hereinafter, specific examples of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 3, in the present invention, a return pipe 9 is provided along the internal cooling cable line 6 to be cooled, and the return pipe 9 and the refrigerant passage 4 directly under the sheath are connected in the longitudinal direction of the internal cooling cable line 6. =Communicate through the communication path 10 at regular intervals.

One end of the conductive refrigerant passage 2 is provided with a heat exchanger 7 for cooling.
A refrigerant made of pressurized insulating oil is supplied by a pump 8.

The refrigerant collected by the return pipe 9 is returned to the heat exchanger 7 for cooling.

However, in the present invention, the refrigerant cooled by the heat exchanger 7 and pressurized by the pump 8 is supplied to the conductive refrigerant passage 2 and flows in the longitudinal direction, and in the process, the refrigerant permeates in the radial direction of the insulating layer 3. The conductor 1, the insulating layer 3, etc. are cooled down.

The refrigerant that has exited to the refrigerant passage 4 directly under the sheath is caused to flow out into the return pipe 9 through each communication passage 10, and is returned to the heat exchanger γ side through the return pipe 9.

When the refrigerant that has exited the refrigerant passage 4 directly under the sheath is allowed to flow out to the return pipe 9 side at various points, the refrigerant flows out of the internal cooling cable line 6 with almost no pressure loss or temperature rise in the refrigerant passage 4 directly under the sheath. can be derived.

Therefore, the temperature rise in the longitudinal direction of the refrigerant in the refrigerant passage 4 directly under the sheath can be suppressed, and the cooling span length can be increased.

FIG. 4 shows how the pressure A in the conductive refrigerant passage 2 and the pressure B in the refrigerant passage 4 directly under the sheath change in the line direction in the cooling method of the present invention, and the differential pressure between the circular pressures A and B is △ In the longitudinal direction of the line 6, P is kept constant as x is L.

Experimental example 275KV, 2500sq, internal diameter of refrigerant passage in conductor 60m
m, 5 to internal cooling cable track with refrigerant inlet temperature 15℃
When a current of 00 OA was applied, the cooling span was 2.51
．． The discharge pressure of the pump 8 required to keep the temperature of the conductor 1 below 90° C. over the entire length of t was 35 degrees Celsius.

On the other hand, an internal cooling cable line of 275KV, 2500sq, conductive refrigerant passage of 60mφ and sheath structure similar to that of a normal OF cable is installed, and the return pipe 9 attached to this line 6 is insulated at intervals of 50m. to form a communication passage 10, and a refrigerant passage 4 directly under the sheath.
An experiment was conducted in which the cooling of
At a pump discharge pressure of /crtl, the conductor temperature could be kept below 90°C over the entire cooling span of 2.5 hours.

Conversely, when the pump discharge pressure was set to 35 gy/cA,
Allowable current in cooling span 25Icrn is 5800A
It became.

As explained above, in the radial flow cooling method for an internally cooled cable line according to the present invention, the refrigerant made of insulating oil that flows out into the refrigerant passage directly under the sheath, which is formed by the narrow L/gap between the goofle core and the insulating layer, is absorbed by the radial flow. Since the refrigerant is sequentially discharged to the return pipe at each position in the longitudinal direction of the line, it is possible to suppress the pressure in the refrigerant passage directly under the sheath from increasing gradually along the longitudinal direction of the line, and the pressure in the refrigerant passage in the conductor and the refrigerant directly under the sheath can be suppressed. The pressure difference between the pressure inside the passage and the pressure inside the line can be maintained almost constant in the longitudinal direction of the line, and the pressure loss of the refrigerant in the refrigerant passage can be made as small as possible, thus reducing the amount of refrigerant that permeates through the insulation layer. The length of the cooling span can be increased by making the cooling span substantially uniform in the longitudinal direction of the line.

Further, according to the present invention, the same allowable current can be achieved with a lower pump discharge pressure than in the conventional radial flow cooling method.

Furthermore, according to the present invention, the refrigerant passage directly under the sheath is replaced with the conventional OFF.
Even if it is the same as a keguru, radial flow cooling can be easily performed.

[Brief Description of the Drawings] Fig. 1 is a system diagram of a system implementing the conventional radial flow cooling method, Fig. 2 is a diagram showing the pressure relationship between the conductive refrigerant passage and the refrigerant passage directly under the sheath in the conventional cooling method, FIG. 3 is a system diagram showing an example of a system implementing the radial flow cooling method according to the present invention, and FIG. 4 is a diagram showing the pressure relationship between the conductive refrigerant passage and the refrigerant passage directly under the sheath in the cooling method of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Conductor, 2... Conductive refrigerant passage, 3... Insulating layer, 4... Refrigerant passage under sheath, 5... Sheath, 6...
・・Internal cooling goofle line, 7・heat exchanger, 8・・
・Pump, 9...Return pipe, 10...Communication path.

Claims (1)

[Claims] 1. In the process of sending a refrigerant made of pressurized insulating oil into the refrigerant passage in the conductor of the internal cooling cable line and causing it to flow in the longitudinal direction, the refrigerant is transmitted in the radial direction of the insulating layer in the line, and the refrigerant is permeated through the insulating layer. In the radial flow cooling method for an internally cooled cable line, the inside of the line is cooled by causing the coolant to flow out into a refrigerant passage directly under the sheath formed by a narrow gap between the insulating layer and the cable sheath. A return pipe is provided outside the cable sheath along the line, and the refrigerant that has exited to the refrigerant passage directly under the sheath is sequentially discharged into the return pipe at each position in the longitudinal direction of the line by means of a radial 70 in the line. A radial flow cooling method for an internally cooled cable track.