JPH08196025A - Intermediate connection part of solid insulation power cable - Google Patents

Abstract

PURPOSE: To provide the intermediate connection part of a solid insulation power cable by which the term of works can be shortened and which is economical, compact and electrically stable. CONSTITUTION: In the intermediate connection part of a solid insulation power cable, an insulator block 6 having a built-in internal shield 5 on a conductor connection part 4 is disposed and a tape-wound insulating layer 7 in which a thin tape is wound on both sides and on the outside of the insulator block 6 is provided, and further an insulating oil 9 is filled in the interior of an external case 10 provided on the outside thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate connecting portion of a power cable having a solid insulator such as cross-linked polyethylene formed by extrusion.

[0002]

2. Description of the Related Art Conventionally, as an intermediate connecting portion of an extruded solid insulated power cable, for example, in the case of a CV cable (crosslinked polyethylene power cable), (1) a crosslinking agent is used as a method for forming a reinforcing insulator on a conductor connecting portion. A method of winding the added polyethylene tape on the cable insulator and heat-molding it. (2) Attach a mold to the cable connection part, inject polyethylene compound containing a cross-linking agent into the mold, and press the outside of the mold. A method of heating from above to crosslink and mold,
(3) A method of inserting and fitting a preformed epoxy resin insulation unit and a rubber mold insulator onto a cable, a method of inserting a preformed rubber mold insulation unit onto a cable, and the like are used.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention (1) A method of winding polyethylene tape and heat-molding it,
(2) The method of injecting polyethylene compound into the mold to heat-crosslink not only requires a lot of equipment and time for forming the reinforcing insulating layer, but also requires a strict foreign substance to obtain a good connection state. Since management and skilled workers are required, there were problems in terms of construction period and economy. Further, the method of inserting a preformed insulating unit on the cable is easy to assemble and suitable for field work, but there is a problem that the outer diameter dimension of the connecting portion becomes large due to the insulating strength of the insulating unit.

On the other hand, a method of using the oil-impregnated paper winding method used for the connection portion for the OF cable and the terminal connection for the CV cable of 275 KV or more can be considered. This method can obtain relatively stable performance without strict foreign substance control, and is a very advantageous method in terms of equipment and construction period. However, when applied to the intermediate connection part of a solid insulated power cable, the end of the cable insulator near the conductor connection part shrinks in the cable axial direction due to the shrink back phenomenon. An oil layer is formed on the surface, and it is necessary to make the outer diameter of the reinforcing insulation layer very large in view of the insulation strength of the oil layer, which is unrealistic as an intermediate connection for ultra-high voltage of 275 KV or more.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides an economical and compact electrically stable intermediate connecting portion which can shorten the construction period. An insulator block containing an internal shield is arranged on the conductor connecting portion, and a tape winding insulating layer formed by winding a thin tape is provided on both sides and outside of the insulator block, and further, an outer case of an external case provided on the outside. It is because the inside was filled with insulating oil.

[0006]

In the above-described intermediate connection portion of the present invention, the influence of the oil layer having a relatively low insulation strength caused by the shrink back of the cable insulator is provided by providing the insulator block having the internal shield on the conductor connection portion. Since it can be eliminated, the insulation outer diameter can be made compact. Also, by using the oil-impregnated insulation part together, it is easy to manage foreign substances, reduce equipment, and eliminate the need for skilled workers.

[0007]

1 is a vertical sectional view of the upper half of a specific example of the intermediate connecting portion of the present invention. In the drawings, 1 is a power cable such as a CV cable having solid insulation by extrusion, 2 is a cable insulator such as cross-linked polyethylene formed by extrusion, and 3 is a cable conductor. An insulator block 6 containing an internal shield 5 is arranged on the central conductor connecting portion 4. The inner shield 5 has a length that does not cause electrical trouble even if the end portion of the cable insulator 2 moves in the axially expanding direction to the left and right due to the shrink back. As the material of the insulator block 6, polyethylene, epoxy, rubber or the like is used, but the insulator block 6 main body is made of insulating rubber, and the inner shield 5 is made of semiconductive rubber. It is desirable to use it because the elasticity of rubber prevents the formation of an oil layer.

On both sides and the outer peripheral side of the insulator block 6, a tape winding insulating layer 7 formed by winding a thin tape such as an insulating paper tape or a plastic tape is provided, and an outer case 10 is provided outside them. The inside of the outer case 10 is filled with insulating oil 9. In the drawing, 8 is a shielding layer provided on the tape winding insulating layer 7, and 11 is an end seal portion of the outer case 10.

FIG. 2 is a vertical sectional view of the upper half of another embodiment of the intermediate connecting portion of the present invention. In the drawings, the same reference numerals as those in FIG. 1 represent the same parts. In this example, as the tape winding insulating layer 7 in FIG.
For the thin tape wound around the part in contact with the tape, use a highly stretchable tape or a tape with good elasticity such as polyethylene, and provide a layer 7a capable of absorbing the radial expansion and contraction of the cable insulator 2 caused by the heat cycle. It is formed of a composite insulating layer provided on the outside thereof with an ordinary insulating tape, and an insulating tape layer 7b in which a plastic film and insulating paper are laminated and integrated.

FIG. 3 is a vertical cross-sectional view of the upper half of still another embodiment of the intermediate connection portion of the present invention, and the same reference numerals as those in FIG. 1 represent the same portions. In this specific example, an annular groove is provided in the cable insulator 2 below which the insulator block 6 is arranged, and a component 12 for preventing shrinkback of the cable insulator 2 is fitted in the annular groove. As a result, the shrink back amount of the cable insulator 2 can be limited to within several mm, so that the entire length of the insulator block 6 can be made compact. In this case as well, it goes without saying that the tape winding insulating layer 7 can be configured as a composite insulating layer as shown in FIG.

FIG. 4 is a vertical cross-sectional view of the upper half of yet another embodiment of the intermediate connection portion of the present invention, and the same reference numerals as those in FIG. 1 represent the same portions. In this specific example, the cable insulator 2 in the portion where the insulator block 6 is arranged in FIG.
It has a small diameter. As a result, the electrical stress at the interface between the insulator block 6 and the cable insulator 2 is 50%.
It can be reduced in the near future. As a result, not only the thickness of the inner shield 4 provided for controlling the electric field can be reduced, but also the outer diameter of the entire connecting portion can be made more compact. In this case as well, it goes without saying that the tape winding insulating layer 7 can be configured as a composite insulating layer as shown in FIG.

[0012]

As described above, according to the intermediate connecting portion of the solid insulated power cable of the present invention, the connecting portion reinforcing insulating layer has the composite insulating structure of the insulator block and the oil-impregnated tape winding insulating layer. , Not only can the assembly time be greatly shortened (30 days / 3 phases → 10 days / 3 phases) compared to the conventional mold type connection part, but also foreign matter management becomes easier, and special assembly equipment and inspection Since no device is required, the cost required for connection can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of the upper half of a specific example of the intermediate connection portion of the present invention.

FIG. 2 is a vertical cross-sectional view of the upper half of another specific example of the intermediate connection portion of the present invention.

FIG. 3 is a vertical cross-sectional view of the upper half of another embodiment of the intermediate connection portion of the present invention.

FIG. 4 is a vertical cross-sectional view of the upper half of still another embodiment of the intermediate connection portion of the present invention.

[Explanation of symbols]

 1 Solid insulated power cable 2 Cable insulator 3 Cable conductor 4 Conductor connection part 5 Inner shield 6 Insulator block 7 Tape winding insulating layer 8 Shielding layer 9 Insulating oil 10 Outer case 11 Seal part 12 Shrinkback prevention parts

Claims (4)

[Claims] 1. An insulator block having a built-in inner shield is arranged on a conductor connecting portion, and a tape winding insulating layer formed by winding a thin tape is provided on both sides and outside of the insulator block, and further on the outside thereof. An intermediate connection portion of a solid insulated power cable, characterized in that an insulating oil is filled inside the provided outer case. 2. The intermediate connection of a solid insulated power cable according to claim 1, wherein the insulator block has a block body made of insulating rubber and an internal shield made of semi-conductive rubber built therein. Department. 3. A composite insulation provided with a tape winding layer capable of absorbing radial expansion and contraction of the cable insulator by using a tape having good elasticity which is wound around a portion where the tape winding insulating layer is in contact with the cable insulator. The intermediate connection part of the solid insulated power cable according to claim 1, wherein the intermediate connection part is formed of layers. 4. An intermediate portion of the solid insulator power cable according to claim 1, wherein the cable insulator at the portion where the insulator block is arranged is stepped off to reduce the diameter of that portion. Connection.