JPS642500Y2 - - Google Patents

Description

[Detailed description of the invention] This invention mainly relates to a termination box for paper insulated cables such as OF cables.

A capacitor type is mainly used for the termination box of ultra-high voltage OF cables, but this is difficult and expensive to manufacture. There is also an electric field shield type, which is cheap but has problems with electrical reliability.

This idea equalizes the electric field in the longitudinal direction from the high voltage side to the ground side by wrapping a high dielectric constant oil-impregnated paper layer with different dielectric constants on the cable insulation instead of the conventional capacitor electrode. This makes it possible to provide a low-cost and electrically reliable termination box.

Example In "Fig. 1", 10 is a cable conductor, 1
2 is a cable insulator.

Reference numeral 14 denotes a cable insulation layer, which is made of a combination of semiconductive paper and metallized paper. This is removed at a suitable point so that the end forms the ground electrode.

16 is a cable sheath, 18 is a conductor pull-out rod,
20 is an insulating layer (valley filling).

A high-voltage electrode 22 is made of, for example, a metal foil wrapped around the cable insulator 12, and is electrically connected to the conductor lead-out rod 18.

24 is a layer of high dielectric constant oil-impregnated paper.

This is provided around the cable insulator 12 from the high voltage electrode 22 to the end of the cable insulation layer 14. This high dielectric constant oil-immersed paper layer 2
4 is composed of eight types of oil-impregnated paper having different dielectric constants, for example, portions 241 to 248.

The oil-impregnated paper is placed along the curve 25 shown in the upper part of FIG.
A material with a high dielectric constant is wound around the parts 248 and 241 where the electric field is concentrated, and a material with a lower dielectric constant is wound between them.
The appropriate dielectric constant value is the highest at the 248 part, about 30, the second at the 241 part, about 20, and the lowest at the 243 and 244 parts, about 5 to 10.

Note that the dielectric constant can be adjusted by adjusting the amount of high dielectric material (for example, carbon powder) mixed into the oil-impregnated paper; the larger the amount mixed, the higher the dielectric constant.

"FIG. 2" is an explanatory diagram showing an example of how to make the high dielectric constant oil-immersed paper layer 24.

First, several layers of oil-impregnated paper tape 248a having the highest dielectric constant are wrapped around the cable insulator 12 to obtain a predetermined thickness. When the boundary between the sections 248 and 247 is reached, the same number of sheets of oil-impregnated paper 247a having a different dielectric constant are stacked and spliced to wrap the section 247, and then in the same manner up to the section 241. Then, going back to the 248 part,
Roll it up as before, and repeat to get the desired thickness. In addition, oil-impregnated paper 248a, 247
It is also possible to use wide sheets of paper corresponding to 248, 247, etc. in FIG. 1 as a, .

The thickness of the high dielectric constant oil-immersed paper layer 24 is from 241 to 24
It may or may not be constant up to the part 8. The end face 240 may also remain upright from the cable insulator 12, especially the end face 240 at 248.
It is not necessary to make 40 into a bellmouth shape as in the past.

Also, 26 is a peeling tube, and 28 is insulating oil, which are the same as the conventional ones.

Effects (1) Figure 3 shows the potential distribution. In particular, the lines of electric force change at parts 248 and 241, and the equipotential surface becomes arrow 30 and 32, the spacing becomes wider, and the spacing becomes closer to equal spacing as a whole.

(2) Expensive capacitor termination is not required, resulting in lower cost.

(3) It is easier to work because there is no need to create a difficult shape like a stress relief cone.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of this invention, together with a dielectric constant distribution diagram, FIG. 2 is an explanatory diagram of how to make a high dielectric constant oil-immersed paper layer 24, and FIG. 3 is a potential distribution diagram. 10: cable conductor, 12: cable insulator,
14: Cable insulation layer, 22: High voltage electrode, 2
4: High dielectric constant oil-immersed paper layer.

Claims (1)

[Scope of utility model registration request] In the exposed cable insulator 12, a high dielectric constant oil-impregnated paper layer 24 is provided from the high voltage electrode 22 provided electrically connected to the cable conductor 12 to the end of the cable insulation layer 14, and The high dielectric constant oil-impregnated paper layer 24 is characterized in that the areas near the high-voltage electrode 22 and the cable shearing layer 14 are made of oil-impregnated paper having a higher dielectric constant than the layer between them. Termination box for power cables.