JPH0419946Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a cable head of a Kottorel cable for supplying DC high voltage to a Kottorel dust collector.

(Technical background of the invention) Paper insulated cables such as OF cables and paper insulated solid cables are used as Kottorel cables. For example, cable conductors made of twisted Al conductors and insulated oil-impregnated paper are used. It has a structure including an insulating layer and an Al sheath.
Then, attach cable heads to both ends of the cable, and electrically connect each cable head to the high-voltage rectifier on the electrical room side and the dust collection electrode on the Kottorel dust collector side, and apply high DC voltage to the dust collection electrode. This ionizes fine particles in the gas and removes them by suction, thereby purifying the gas.

The cable head of the above Kottrell cable is
An insulator pipe with an upper metal fitting airtightly fixed to the upper end;
A conductor pull-out rod is inserted into the insulator tube by passing through the upper metal fitting in an airtight manner and connected to the end of the cable conductor, and the insulator tube is filled with an insulating mixture.

(Problems with the background art) By the way, Kottorel dust collectors are usually installed at a height of 10 to 30 meters above the ground, so in this case, the cable head on the dust collector side is also connected to the electrical room. It will be placed 10 to 30 meters higher than the cable head. However, if there is a difference in height between the two cable heads, the insulating oil in the insulating oil-impregnated paper that forms the insulating layer of the Kottle cable moves downward, causing the dust collector side, that is, the high place side, to move downward. At the cable head, the fill height of the insulating mixture is reduced by the displacement of the insulating oil, creating a vacuum void in the insulator tube. If a negative pressure gap occurs within the insulator, arc discharge may occur within the insulator, resulting in dielectric breakdown of the cable head.

(Purpose of the invention) An object of the invention is to provide a cable head for a Cottrell cable having a structure in which a negative pressure gap does not occur even when the insulating oil of the insulating oil-impregnated paper moves.

(Summary of the invention) The invention consists of an upper metal fitting that is airtightly fixed to the upper end of the insulator pipe, which is made of gray cast iron that has ventilation properties.
It is characterized by the fact that the negative pressure created within the insulator pipe is gradually returned to atmospheric pressure.

(Embodiments of the invention) Hereinafter, embodiments of the invention will be described in detail with reference to the drawings.

1 and 2 show a cable head of a Cottrell cable according to the invention. That is, this cable head includes an insulator tube 1;
An insulator pipe upper metal fitting 1A is fixed to the upper circumferential surface of the insulator pipe through a cement attachment part 2. An upper metal fitting 3 is airtightly secured to the upper end surface of the insulator tube 1 via a packing 4, and the upper metal fitting 3 is bolted to the insulator tube upper metal fitting 1A. The upper metal fitting 3 is made of gray cast iron and has breathability, but does not allow moisture such as rainwater to pass through. A conductor pull-out rod 5 passes through the upper metal fitting 3 in the vertical direction, and an O-ring 6 is attached to the circumferential surface of the conductor pull-out rod 5 on the upper metal fitting 3. The O-ring 6 is pressed by a fastening fitting 7 bolted to the upper fitting 3. The upper metal fitting 3 is the upper cover 8
The upper end of the conductor pull-out rod 5 protrudes from the upper cover 8 through a packing 9.

A mounting bracket 10 is fixed to the lower circumferential surface of the insulator pipe 1 via a cemented portion 2', and a lower bracket 11 is bolted to the mounting bracket 10. This lower metal fitting 11 is airtightly secured to the lower end surface of the insulator tube 1 via a packing 12. The end of a cable 20 is inserted through the lower metal fitting 11, and a packing 13 is attached to the circumferential surface of the shielding layer 20c of the cable 20. This packing 13 is pressed by a pressing member 15 to which an elastic force is applied by a coil spring 14.
It is placed within 6. An anti-corrosion tape 17 is wrapped around the end of the sheath layer 20d of the cable 20 and the lower part of the fastening fitting 16. Further, the cable 20 terminal where the sheath layer 20d and the shielding layer 20c are peeled off and the insulating layer 20b is exposed is the insulator tube 1.
It is expanding inward. The insulating layer 20b is formed from insulating oil-impregnated paper, and the cable conductor 20a extending from the pencil ring portion at the tip is connected to the conductor pull-out rod 5. The insulator 1 is filled with an insulating mixture 18. Incidentally, insulating oil-impregnated papers 19A and 19B are wrapped around the connecting portion between the conductor pull-out rod 5 and the cable conductor 20a and below the insulating layer 20b, respectively.
A shielding tape 1 is further placed on one insulating oil-impregnated paper 19B.
9C is wrapped around it.

By the way, as shown in FIG. 1, the cable head of the present invention has a connector 22 attached to the upper end of the conductor pull-out rod 5, and is connected to a high-placed dust collector (not shown) via a lead wire 23. electrically connected to the dust collection electrode on the side). The conventional cable head is also electrically connected to a high voltage rectifier on the lower electrical room (not shown) side.
Therefore, by applying a DC high voltage to the dust collection electrode through the conventional cable head, the cable head of the present invention, and the cable head of the present invention, fine particles in the gas can be ionized and removed by suction, thereby purifying the gas. can do.

Now, as mentioned above, since the cable head of the present invention is arranged at a high place, the insulating oil in the insulating layer 20b (insulating oil-impregnated paper) of the Kottorel cable 20 moves downward, and the cable head of the present invention moves downward. Drips in the cable head. Therefore, the filling height of the insulating mixture 18 is reduced, and a gap 21 is created between the upper metal fitting 3 and the insulating mixture 18 in the upper part of the insulator tube 1. However, as described above, since the upper metal fitting 3 is made of breathable gray cast iron, the outside air gradually enters the space 21 through the upper metal fitting 3. That is, outside air infiltrates so that the air pressure inside the insulator tube 1 increases by 20 to 40 mmHg per day. Therefore,
The negative pressure in the void 21 can be returned to atmospheric pressure in several tens of days. Therefore, it is possible to effectively prevent arc discharge from occurring within the insulator tube 1, so that dielectric breakdown does not occur in the cable head. Further, since the upper metal fitting 3 made of gray cast iron does not allow moisture to pass through, rainwater and the like will not enter into the insulator pipe 1.

In addition, FIG. 3 is a characteristic diagram showing the state of occurrence of partial discharge with respect to the atmospheric pressure inside the insulator tube in relation to the DC voltage supplied to the Kottorel cable 20, where ○ indicates the occurrence voltage of partial discharge with respect to atmospheric pressure, and × indicates the occurrence of partial discharge with respect to the atmospheric pressure. It shows the voltage for extinguishing partial discharge. This third
As is clear from the figure, when the negative pressure inside the insulator tube increases, partial discharge occurs, and when the atmospheric pressure is about 450 mmHg or higher, no partial discharge occurs.

(Effects of the invention) According to the invention, by forming the upper metal fitting from gray cast iron, the filling height of the insulating mixture in the insulating pipe is reduced due to the downward movement of the insulating oil of the Kottorel cable, and the upper part of the insulating pipe is Even if a negative pressure gap occurs, the ventilation characteristics of the upper metal fitting can be used to gradually return the negative pressure gap to atmospheric pressure. Therefore, since it is possible to prevent arc discharge from occurring within the insulator tube, it is possible to provide a cable head for a cotterel cable that is free from the risk of dielectric breakdown.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the main parts of the cable head according to the present invention, Fig. 2 is a cross-sectional view showing half of the cable head according to the present invention, and Fig. 3 is a cross-sectional view showing the main part of the cable head according to the present invention. FIG. 3 is a characteristic diagram showing the relationship between supplied series voltage and partial discharge. 1... Insulator pipe, 3... Upper metal fitting, 5... Conductor pull-out rod, 11... Lower metal fitting, 18... Insulating mixture, 2
0...Kottrell cable.

Claims (1)

[Scope of utility model registration request] In a cable head provided at the high end of a cable conductor having an insulating layer made of insulating oil-impregnated paper on the cable conductor, an upper metal fitting is fixed to the upper end of the insulator tube in an airtight manner, and 1. A cable head of a Kottorel cable, characterized in that the upper fitting is made of gray cast iron, and the upper fitting is made of gray cast iron.