JPS6041528B2 - Cable cooling method - Google Patents

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 cold soot.

Forced cooling methods are increasingly being used, in which various kinds of heat generated in the cable are taken out to the outside through refrigerant circulation, the heat is radiated or cooled, and then the cable is re-introduced.

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. 1, the cooled cold soot 1 is press-fitted into the high-voltage termination part 3 by a pump 2 or the like at ground potential, passes through a refrigerant passage 5 provided inside the conductor 4, and then passes through the cable to generate heat. take away,
The water reaches the pond end 6, and from the high-pressure part passes through the pre-cooler 7, heat exchanger 8, storage tank 9, etc., which are at ground potential, and 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.Also, when flowing between the ground potential and high voltage potential, the dielectric strength of cold soot decreases. There is also the possibility that insulation may not be maintained due to the drop. For this reason, a method is used in which a filter 10 is installed in a part of the circulation system to remove solid matter exceeding a certain limit, and an ion exchanger 11 or the like is installed to remove impurity ions. In particular, impurity ions, which are most problematic in terms of dielectric strength, are likely to be generated in the cable refrigerant passage 5 and the return pipe 12, which are at high temperatures and have a large contact area. On the other hand, when the load is low, when the cables or cooling system are inspected, or when there is a partial failure, the circulation system is temporarily stopped with some of the refrigerant remaining in the cold soot passage 5 and the return pipe 6, and then restarted. In this case, the refrigerant passage 5,
The refrigerant that remained in the return pipe 12 contains impurity ions at a higher concentration than usual, and when it is restarted, a high concentration of impurities flows into the ion exchanger 11 at once, making it impossible to process and leaving it as it is. It is pumped out by the pump 2, and insulation up to the high voltage part on the inlet side cannot be maintained. In addition, installing an ion exchanger that has the ability to process cold soot with high concentration of ions in a short time would be unnecessary equipment in terms of constant continuous operation, which would impair the economic efficiency of the cooling system. .

The same thing can be said about 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 cold soot that is stable in terms of insulation. That is, the present invention provides for stopping the cooling circulation system,
When resuming work, the returned refrigerant is taken out of the closed circulation loop,
In order to prevent refrigerant with high impurity concentration from flowing directly into the processing bag and exceeding its processing capacity, a branch was installed in a part of the circulation system.

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

The cable used was a copper conductor (size 500 squares), a nominally 24 mm VCV cable with a cold soot steel pipe inner diameter of 1 mm inside the conductor, and an ion exchange device, a heat exchanger, a pump, and a cold soot transport return pipe were attached to this. We used this as a cooling loop and conducted experiments to understand the various characteristics of the cooling system at room temperature.

When the cooling water was circulated at a flow rate of about 5 mm/min, the conductivity was due to impurity ions, so the initial value of the cooling water was 0.75 μS/arc, but after 1 hour it reached a nearly saturated state of 2 μS/min. became.
This indicates that although some of the generated impurity ions are reduced by the ion exchanger, the impurity ions slightly increased from the initial value due to the balance between generation and removal. After that, the cooling system was stopped for a day and night, and when restarted, the conductivity of the returned water immediately rose to 7 S/s, and even after passing through the ion exchanger, the conductivity of the returned water increased to 6
．． It was at a high level of 5 S/skin, but as a result of subsequent lhr operation, it decreased to 2 S/skin at all positions in the system, showing a stable value.

In other words, immediately after restarting operation, cooling water with high concentration of ions that had accumulated in the soot pipe, return pipe, and other parts directly reached the ion exchanger, and was pumped out with a high concentration that exceeded its processing capacity. This indicates that the ion exchanger gradually processed the ion exchanger as it was circulated several times, and a balance state was reached.

The above results are based on small-scale experiments, but in actual cables that undergo more severe operating conditions, cooling water containing highly concentrated impurities enters between high-voltage sections from ground potential immediately after circulation resumes, and the insulation performance of that section deteriorates. There is a strong possibility that this will cause a decrease in the temperature and cause dielectric breakdown.

Note that the terminus 3 does not necessarily refer to the terminus of the cable, but refers to the inlet of the butterfly, and the other end 6 refers to the outlet of cold soot.

Although the above example deals with impurity ions in the cooling water, the same can be said of the tortoise-conducting particles generated from the entire cooling system, and during continuous operation, those that are kept at a low concentration in a certain balanced state are used to restart operation. Immediately after, it intensively reaches the filter and clogs the filter in a short period of time, or it is sent out in high concentration through a bypass circuit (Fig. 2, 13) installed in parallel with the filter.

Therefore, in order to prevent these abnormal phenomena, the branch part 15 is placed immediately after exiting the delivery pump in the enlarged view of FIG. It is necessary to release the returned refrigerant to the outside in a concentrated state.

A valve 16 or 16' is attached to the tip of the branch, and based on experience, it can be released by opening the valve in a certain amount or for a certain period of time, or by detecting the concentration of impurities at the branch and detecting impurities that exceed a certain limit. The valve may be opened when the In either case, the valve can be operated automatically or manually. The released butterflies 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, by simply installing a filter or ion exchanger that can perform sufficient treatment under normal operating conditions, stable cooling performance can be achieved without installing a treatment device with a capacity that can handle abnormalities immediately after restart. This makes it possible to send soot to high-voltage parts, which is highly effective in providing an economical and stable cooling method.

[Brief explanation of the drawing]

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...Cold soot passage within the conductor, 6...Other end terminal, 7... Pre-cooler, 8... Heat exchanger, 9... Refrigerant storage tank, 10...
...Filter, 11...Ion exchanger, 12.
... Return pipe, 13 ... Filter bypass pipe, 14 ... Branch section, 15 ... Branch section, 16 ...... Minute Branch valve, 16'...
...Branch part balf. Figure 1 Festival style

Claims (1)

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