JPS5917814A - Method of cooling cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling a high voltage cable, and more particularly to a method for cooling a high voltage section using a refrigerant.

Forced cooling methods are increasingly being used, in which various kinds of heat generated in cables are trapped in refrigerant circulation, taken out to the outside, radiated or cooled, and then sent back in. In general, cables are cooled by cooling the internal high voltage conductors rather than cooling from the outside, which is more effective. For example, as shown in FIG.
is press-fitted into the high-voltage termination part 3 by a pump 2 or the like at ground potential, passes through a 1m refrigerant path 5 provided inside the conductor 4, removes heat from the cable, reaches the other end 6, and is discharged from the high-voltage part to the earth. After passing through the pre-cooler 7, heat exchanger 8, storage tank 9, etc., which are at potential, it is again pumped and circulated.

At this time, if the refrigerant deteriorates or foreign matter enters the circulation system, there is a risk of deterioration or damage to the inner wall surface of the circulation system.
There is also a possibility that insulation may not be maintained due to a decrease in the dielectric strength of the refrigerant. For this reason, a filter 10 is installed in a part of the circulation system to remove solids exceeding a certain limit, and an ion exchanger 11
A method is used to remove impurity ions. In particular, impurity ions, which are most problematic in terms of dielectric strength, are present in the cable refrigerant passage 5 and the return/return area, which are at high temperature and have a large contact area.
It is likely to occur within ξ Eve 12. On the other hand, when the load is low, when the cable or cooling system is inspected, or when there is a partial failure, the circulation system is temporarily stopped with some of the refrigerant remaining in the refrigerant passage 5 and the return vibro, and then restarted. At this time, refrigerant passage 5, return/ξ Eve 12
The refrigerant that has accumulated in the refrigerant contains impurity ions at a higher concentration than usual, and when the refrigerant is restarted, a high concentration of impurities flows into the ion exchanger 11 at once, making it impossible to process. , and is pumped out by pump 2, making it impossible to maintain insulation at the high voltage part on the artificial side.

Furthermore, installing an ion exchanger capable of processing this highly concentrated ion refrigerant in a short time would be unnecessary equipment from the standpoint of continuous operation, which would impair the economic efficiency of the cooling system.

The same can be said of solid matter removal filters.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional methods described above and to provide a cooling method that can economically circulate a dielectrically stable refrigerant.

That is, the present invention takes the returned refrigerant out of the closed circulation loop when the cooling circulation system is stopped and restarted, and controls the circulation system so that the refrigerant with high impurity concentration does not flow into the processing equipment at once and exceed its processing capacity. This is because some branches are placed.

The implementation of the present invention will be explained by the following specific examples.

A nominally 24 m 22 KV cV cable with a copper conductor (size 500 mm2) and 4 internal refrigerant copper tubes with an inner diameter of 10 mm was used as the cable, and was equipped with an ion exchanger, a heat exchanger, a pump, and a refrigerant transport return/guve for cooling. We conducted an experiment to understand the characteristics of the cooling system at room temperature. When the cooling water was circulated at a flow rate of about 5 R/min, its conductivity was due to the accumulation of impurity ions, and the initial value o2
The cooling water flow rate of 75 μs/ctn became almost saturated at 2 μs^ after 1 hour. This shows that although some of the impurity ions generated are reduced by the ion exchanger, they slightly increased in the S lance state of generation and removal compared to the initial first shift.

After that, I stopped the cooling system for a day and night, restarted it, and immediately returned home! The cardiac conductivity of the water rose to 7 μs 7 cm, and even after passing through the ion exchanger (i, it was as high as 5 μS/cm, but after 1 hr of operation/ζ the result was 2 μS/c1n at all positions in the system) It decreased to a stable value.

In other words, immediately after restarting operation, the cooling water with high concentration of ions accumulated in the refrigerant pipe, return/ξ-eve, and other parts directly reaches the ion exchanger and is pumped out with a high concentration exceeding its processing capacity. This shows that as it circulates many times, it is gradually processed by the ion exchanger and reaches the ζ lance state.

The above results are based on small-scale experiments, but in actual cables, which are subject to more severe operating conditions, immediately after the circulation is restarted, cooling water containing highly concentrated impurities enters between the high voltage parts from the ground potential. There is a strong possibility that the insulation 1'lE ability will be reduced and dielectric breakdown will occur.

Note that the terminal end 3 does not necessarily refer to the terminal end of the cable, but refers to a refrigerant inlet, and the other end 6 refers to a refrigerant outlet.

Although the above specific example deals with impurity ions in the cooling water, the same can be said of conductive particles generated from the entire cooling system. In some cases, the filter reaches the filter in a concentrated manner, clogging the filter in a short period of time, or the PI-97 circuit (
[Fig. 2] 3) and is sent out with high concentration.

Therefore, in order to stop these abnormal phenomena by 19 points, in the enlarged view of FIG. , 15 branches are placed in the branch part 14 immediately after exiting the +5 pump or in front of the storage tank 9 that stores clean refrigerant, so that the refrigerant returned at a high temperature of 1 degree can be safely discharged to the outside. A sharp valve 16 or 16' is installed at the tip of the branch, and empirically, it is possible to discharge by opening the valve for a certain period of time or to detect the impurity concentration at the branch. The valve may be opened when a certain limit is exceeded. In either case, the S loop can be operated automatically or manually. The discharged refrigerant may be discarded, or may be treated by a separate treatment device and then reinjected into the circulation system.

According to the present invention described above, refrigerant with stable performance can be obtained by simply installing a filter or ion exchanger that can perform sufficient treatment under normal operating conditions without installing a treatment device with a capacity that can handle abnormalities immediately after restart. This makes it possible to send energy to high-voltage parts, which is highly effective in providing an economical and stable cooling method.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a conventional cable cooling method,
FIG. 2 is an enlarged explanatory view of the vicinity of a cooling device showing an embodiment of the method of the present invention. 1. Refrigerant, 2. Circulation pump, 3. Cable end, 4. Cable conductor, 5. Refrigerant in conductor 1F! l road, 6
・・Other end terminal part, 7・・Precooler, 8・・Heat exchanger,
9 ・Refrigerant storage tank, 10 Filter, 11 Ion exchanger, 12 ・Return・ξ Eve, 13 Filter pipe・
ξS tube, 14...Branch, 15 Branch, 1G, Branch, ζRuso, 16'...Branch, S Luso.

Claims (1)

[Claims] (1) In the cable circulation cooling method, in which the cooled refrigerant is force-fed to the high-voltage part of the cable, returns after cooling the high-voltage part, and radiates and cools the high-voltage part again, when restarting the circulation system after stopping, the returned refrigerant is A cable cooling method characterized in that the cable is taken out of the circulation loop and stored after being disposed of or cleaned.