JPH11234839A - Connecting method for cross-linked polyethylene power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form compact joints of a cross-linked polyethy lene power cable. SOLUTION: The conductors 3a, 3b of cross-linked polyethylene power cables 1a, 1b are exposed by stripping the cable insulators 2a, 2b of the ends of the cross-linked polyethylene power cables 1a, 1b composed by insulating the conductors 3a, 3b composed by twisting a plurality of conductors, tapering surfaces 13 opened towards the peripheries of the tips of the cable insulators from the conductor sides are provided at the end sections of the cable insulators 2a, 2b after the exposure of the conductors 3a, 3b. The conductors of the cable 1a whose conductors 3a exposed are cut differing their lengths individually, and those of the cable 1b end finished similarly are butt-welded to each other, and an internal semiconductive layer 5 formed on the joint conductor exposed. After this, a die 6 is provided striding the cable insulator ends of both cables 1a, 1b, and a process of injecting an insulating resin into this die 6 and forming a reinforcing insulating layer 8 is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for connecting a crosslinked polyethylene power cable.

[0002]

2. Description of the Related Art Crosslinked polyethylene power cables are rapidly following the path of high voltage due to their excellent insulation properties and ease of handling, and long-distance lines of 275 kV class are being constructed. Cable connections are essential for long-distance lines. The connection of the 275 kV cross-linked polyethylene power cable is performed by connecting the exposed conductors to each other, providing an internal semiconductive layer on the conductor, and covering the stripped cable insulator with a split mold. An extruding resin is extruded from a small extruder into the extruded resin, formed into a predetermined shape, coated with an external conductive layer, and heated and pressurized in an integrated state with the extruded insulating resin to form a cross-linking connection using an extrusion molding connection method. Department has been adopted.

[0003] A general description of the extrusion molding connection method will be given with reference to FIG. The working steps of this method are as follows. 1) First, the cables 1a and 1b are stripped to predetermined dimensions to expose the cable conductors 3a and 3b.
The ends of a and 2b are processed into a pencil sharpened shape (pencilling portion). Thereafter, the exposed cable conductors 3a, 3
b. Compression connection is performed using the conductor connection pipe 4. An inner semiconductive layer 5 is formed on the conductive connection pipe 4 by using a semiconductive tape or a semiconductive shrink tube. 2) Next, a mold 6 is put over the entire connecting portion via the cushion material 7, and an uncrosslinked insulating resin heated and melted by a small extruder (not shown) is extruded into the space inside the mold 6. . 3) Thereafter, the mold 6 is disassembled, and the solidified insulating resin is cut into a predetermined shape to cover the external conductive layer. 4) Finally, the whole is housed in a closed container and crosslinked by heating under gas pressure. Thus, the reinforcing insulating layer 8 having the same layer structure as the cable is formed. In the figure, 9
Reference numerals a and 9b denote cable external conductive layers.

The above-mentioned extrusion molding connection method is a highly reliable connection method for crosslinked polyethylene power cables.
However, in this connection method, the outer diameter of the connection portion is considerably larger than the outer diameter of the cable. This is because the conductor connection pipe 4 after compression is larger than the outer diameter of the cable conductors 3a and 3b, and if the characteristics of the reinforcing insulating portion are to be made equal to those of the cable insulating portion, the outer diameter of the reinforcing insulating layer 8 will be ,
This is because it becomes larger than the outer diameter of 2b. By the way, in recent years, in order to further reduce the size of the power transmission system and facilitate the installation, it is required to reduce the outer diameter of the cable connection portion.

As a method of reducing the outer diameter of the cable connection portion, there is a method of connecting a conductor by welding without using a conductor connection pipe. In this method, as shown in FIG. 4, for example, the cable conductor is composed of divided conductors 3a and 3b. The divided conductors 3a and 3b are separated and drawn out, and the opposed divided conductors 3a and 3b are welded. At this time, the welded portion 12 is shifted in the longitudinal direction for each of the divided conductors, and the weakly welded portion 12 is dispersed in the longitudinal direction. FIG. 5 shows a connection portion manufactured by this method. In FIG. 5, the reinforcing insulating layer 8
Has the same outer diameter as the cable insulators 2a and 2b. Reference numeral 10 denotes an external semiconductive layer.

[0006]

In this method, the outer diameter of the conductor connecting portion is reduced, but the length is increased. That is, in FIG. 4, the pitch p in the longitudinal direction of the welded portion 12 of the divided conductors 3a and 3b must be equal to or longer than a predetermined length. In addition, since it is necessary to perform a welding operation, the divided conductors 3a and 3b to be connected must be separated and pulled out. As a drawing-out margin, the ends of the pencilling portions of the cable insulators 2a and 2b and the nearest welded portion 12 are formed. The interval m needs to be longer than a predetermined length. For example, when welding 5 divided conductors of 2500 mm ^2, the conductor exposed length L _b is equal to or greater than 800 mm. Incidentally When connecting this conductor in the process of connecting tube compression, in FIG. 3, the exposed conductor length L _a is about 300 mm. Thus, when the length of the conductor connection portion is increased,
When forming the reinforcing insulating layer, there is a problem in that the propagation of the resin pressure in the mold becomes difficult to spread to the end portion, and a resin-unfilled portion occurs, thereby lowering electrical reliability.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and strips a cable insulator at a terminal of a cross-linked polyethylene power cable in which a twisted split conductor is insulated with cross-linked polyethylene. A tapered surface that opens from the split conductor side toward the outer periphery of the tip of the cable insulator is provided at the end of the cable insulator after the split conductor is exposed, and the exposed split conductor is separated for each split conductor. After butt-welding the divided conductors of the first cable cut at a different length and the second cable similarly processed to form an internal semiconductive layer on the exposed connecting portion conductor Connecting a cross-linked polyethylene power cable, wherein a mold is provided across the cable insulator ends of both cables, and a reinforcing insulating layer is formed by injecting an insulating resin into the mold. It is the law.

As described above, according to the present invention, as shown in FIG. 1, tapered surfaces are provided at the ends of the cable insulators 2a and 2b, the tapered surfaces being open from the divided conductor side to the outer periphery of the distal end of the cable insulator. In other words, the pencilling process is performed in the opposite direction to the conventional pencilling process at the end of the cable insulator. Then, the mold 6 is installed such that both ends thereof are held by the reverse-pencilling processing portion at the end of the cable insulator. Then, the exposed conductor length as L _b, the length of the extrusion space of the mold 6 becomes L _b -2d. On the other hand, in the conventional case (as shown in FIG. 5, the outer shape of the ends of the cable insulators 2a and 2b is tapered, and the length of the portion is d.
), The length of the extrusion space of the mold 6 is at least L _b + 2d, so that the length of the extrusion space of the mold 6 can be shortened by the present invention.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram of one embodiment of a method for connecting a crosslinked polyethylene power cable by extrusion molding according to the present invention. The crosslinked polyethylene power cables 1a and 1b used in the present embodiment are 275 kV, 2
A 500 mm ² cable comprising a cable conductor 3a,
3b is made of a five-piece conductor. The steps of the extrusion mold connection method are as follows. 1) First, the cables 1a and 1b are cut, and the divided conductors 3
a, 3b are spouted over a sufficient length. In addition, the end of the cable insulator is machined to a depth of 100 mm.
Are provided. Thereafter, the cable outer conductive layers 9a and 9b are peeled to a predetermined size. The machining of the tapered surface is performed until the final finish by machine cutting, and the depth d is 100
mm. 2) Then, as a final conductor exposed length L _b is 1000 mm, divided conductors 3a, trimmed conductors tip every 3b of the segment, performs welding. The internal semiconductive layer 5 is formed on the conductor connection portion by tape winding. Incidentally, cable insulation end distance has become L _b -2d, to 800 mm. 3) Next, a mold 6 having an internal extrusion space length of 800 mm is placed on the conductor connection portion via a cushion material 7, and an uncrosslinked polyethylene resin is extruded into the inside thereof, and a length of 80 mm is extruded.
A 0 mm resin layer is formed. 4) After completion of the extrusion, the mold 6 is removed, and as shown in FIG. 2, the resin layer is shaped to the same outer diameter as the cable insulators 2a and 2b, and the outer semiconductive layer 10 is covered. 5) Finally, the entire connection portion is housed in a closed container, and is heated and cross-linked under gas pressure to form a reinforcing insulating layer 8 having an outer diameter substantially the same as that of the cable insulator.

Table 1 shows the dimensions of the connecting portion of this embodiment. Table 1 also shows the dimensions of a conventional example (corresponding to FIG. 3) in which a conductor was connected by compression of a connecting pipe and a conventional example (corresponding to FIG. 5) in which a conductor was connected by welding. As can be seen from Table 1, the die extrusion space length of this embodiment (800 mm)
Is the conventional mold extrusion space length by welding connection (1200
mm).

[0011] Note 1) Depth of the tapered hole at the end of the cable insulator (reverse pencilling) 2) Distance between the ends of the cable insulator

It should be noted that the present invention is not limited to the above embodiment, and the depth of the tapered surface at the end of the cable insulator and the inclination gradient (reverse pencilling) can be determined by the ease of cutting the cable insulator. it can.

[0013]

As described above, according to the present invention, there is an excellent effect that a compact extrusion-molded connection portion of a crosslinked polyethylene power cable can be formed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of a method of connecting a crosslinked polyethylene power cable by extrusion molding according to the present invention.

FIG. 2 is a vertical cross-sectional view of an extrusion mold connecting portion manufactured in the embodiment.

FIG. 3 is an explanatory view of a conventional extrusion molding connection method of a crosslinked polyethylene power cable.

FIG. 4 is an explanatory view of a conductor connection portion by segment welding.

FIG. 5 is a longitudinal sectional view of an extrusion mold connecting portion having a conductor connecting portion by segment welding.

[Explanation of symbols]

 1a, 1b Cable 2a, 2b Cable insulator 3a, 3b Split conductor 5 Internal semiconductive layer 6 Mold 7 Cushion material 8 Reinforced insulating layer 9a, 9b Cable external semiconductive layer 10 External semiconductive layer 13 Tapered surface

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironobu Hirano 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Shunichi Shindo 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (1)

[Claims] An end of a cable insulator after exposing the split conductor by peeling off a cable insulator of a terminal of a crosslinked polyethylene power cable in which a twisted split conductor is insulated with crosslinked polyethylene and exposing the split conductor. In the same manner as the first cable obtained by providing a tapered surface that opens from the divided conductor side to the outer periphery of the distal end of the cable insulator from the divided conductor side, and exposing the divided conductor to have a different length for each divided conductor, the same as the first cable. After the split conductors of the second cable are butt-welded to each other to form an inner semiconductive layer on the exposed connecting portion conductor, a mold is provided across the cable insulator ends of both cables. A method for connecting a crosslinked polyethylene power cable, wherein an insulating resin is injected into the mold to form a reinforcing insulating layer.