JPH0360314A - Connection of power cable insulated with plastic - Google Patents

Abstract

PURPOSE:To restrict the effect of a gap or step produced in a connection part insulating block to flow of a part of an insulating interposition layer thereto and prevent production of semiconductor projections and unevennesses by making an insulating interposition layer on a semiconductor layer inside the connection part before the connection insulating block is installed. CONSTITUTION:Conductors 15A and 15B placed abutted are weld connected with silver solder 16. Semiconductor polyethylene tape is wound round the section including the conductor connection and cable inner conductive layers 14A and 14B and molded by heating to form a semiconductor layer 17 inside the connection part. Polyethylene tape containing a cross-linking agent but not yet cross-linked is wound to the thickness of approximately 1mm to form an insulating interposition layer 18. A connection part insulating block 19 containing a cross-linking agent but not yet cross-linked is mounted on a section extending to cable insulators 13A and 13B. A semiconductor thermal-contraction tube is put on the block 19 and contracted by heat to form an external semiconductor layer 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for connecting plastic insulated power cables.

[Prior art]

As the application of cross-linked polyethylene electrical cables to ultra-high voltage lines progresses, shortening the connection work time has become a major issue in streamlining line construction. That is, the mold joint method, which is a technique for connecting cross-linked polyethylene electrical cables with voltage class 154 of V or higher, provides stable and high performance, but has the disadvantage that it takes a long time to complete the connection work. For this reason, there is a growing need for so-called prefabricated insulators that assemble insulating parts prefabricated in factories on-site, and 154KV class prefabricated insulators have already been developed and are about to be put into practical use.

However, since prefabricated inserts use epoxy or rubber for reinforcing insulators, they cannot be subjected to high electrical stress like cross-linked polyethylene, so they have the disadvantage that the dimensions of the connection parts are large. 9
It is expected that the areas where it can be applied will be limited due to space constraints on class lines.

For this reason, as a connection method that combines the high performance of molded joints with the simplicity of prefabricated joints to some extent, the reinforcing insulator for the connection part is manufactured in advance as an insulating block at the factory, and then it is attached to the cable connection part on site. Methods have been proposed in which it is attached and heated to integrate with the cable insulation. In this case, it is preferable that the connecting portion insulating block is divided into two halves (or more is possible) in terms of installation workability.

〔assignment〕

However, when using a halved connection insulation block, the following problems arise. In other words, when using a connection part insulating block, after connecting the conductor, a connection part internal semiconducting layer is provided on top of it, and a connection part insulating block is attached on top of it.
At this time, as shown in Figure 4, before the joint 2 of the two halves of the insulating block 1a-1b is bonded, the semiconductive layer 3 inside the connection part flows and the inside of the joint 2 is heated. , and may form rib-like protrusions 3P.

Such a protrusion 3P is not preferable because it becomes an electrical defect.

In addition, due to accuracy and dimensional accuracy when installing the connecting insulating block, a step may occur on the inner peripheral surface corresponding to the seam 2 of the insulating blocks 1a and 1b, as shown in Figure 5. When this is completed, the bottom of the connecting portion internal semiconducting layer 3 is shaped accordingly, forming a stepped protrusion 3Q. Such a protrusion 3Q also becomes an electrical defect.

Furthermore, in the inner layer of the insulation block, the insulation block and the internal semiconducting layer of the connection part are bonded together before the insulation blocks are bonded to each other, so if the insulation block subsequently moves relative to each other due to the influence of heat, A protrusion will be formed on the surface of the semiconductive layer inside the connection portion.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a connecting part internal semiconductive layer on top of the conductor so as to span the internal semiconductive layers of the cable on both sides after connecting the conductors. By attaching and heating a connection insulation block divided into two or more parts so as to straddle the cable insulation,
A method for connecting a plastic insulated cable that integrates a connecting part insulating block and a cable insulator, characterized in that an insulating intervening layer is provided on the internal semiconductive layer of the connecting part before attaching the connecting part insulating block. It is something.

[Effect]

When an insulating intervening layer is provided on the internal semiconducting layer of the connecting part, the connecting part insulating block and the connecting part internal semiconducting layer do not come into direct contact with each other, so even if a gap or step occurs in the connecting part insulating block,
The insulating intervening layer only needs to partially flow and flow into it, eliminating the risk of semiconductive protrusions or irregularities.

〔Example〕

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

Embodiment 1 Figure 1 shows an embodiment of the present invention, connecting cable l.
lA・11B is 275 to V 1400mm”
(7) Cross-linked polyethylene electrical cable (cable outer semiconductive layer outer diameter 105 mm, insulator outer diameter 103+m). The ends of the cables 11A and IIB are stripped to predetermined dimensions, and the outer semiconducting layers 12A and 12B1 are insulators 13A and 13.
B1 internal semiconducting layers 14A and 14B are exposed, and the conductor 15
Interject A/15B. Before connecting conductors 15A and 15B, parts such as semiconductive heat shrink tube, crosslinking gas barrier layer, and buffing of crosslinking pressurized pipe are attached to Cable II.
Extrapolate to the A side or IIB side.

In the connection work, first, the conductors 15A and 15B are butted together and connected by welding with silver solder 16. This welding is performed while cooling the exposed conductor parts on both sides of the welded part in order to avoid any adverse effects of heat on the cable insulators 13A-13B on both sides. It is wound so as to straddle the internal conductive layers 14A and 14B of the cable, and is heated and molded to form the connecting portion internal semiconductive layer 17.

Thereafter, an uncrosslinked polyethylene tape containing a crosslinking agent is wound around the tape to a thickness of about 1 inch to form an insulating intervening layer 18. It is preferable that the insulating intervening layer I8 is formed so that both ends thereof overlap part of the tapered cable insulators 13A and 13B, as shown in the figure.

Next, take out the uncrosslinked connection insulating block 19, which is cut in half and has one side containing a crosslinking agent in the shape shown in Figure 2, from the nitrogen gas-filled sealed container, and place it so that it straddles the cable insulators 13A and 13B. Assemble. The insulating block 19 has a length of 50
0 questions, the outer diameter is 123 shafts. After that, the insulation block 19
A semiconductive heat-shrinkable tube is placed on top so that both ends rest on the cable outer semiconductive layers 12A and 12B, and heat-shrinked to form the outer semiconductive layer 20 of the connection portion.

Next, a gas barrier layer is coated thereon, a pressurizing tube for crosslinking is attached, and by applying pressure and heating, the insulating block 19 and the Pi edge intervening layer 18 are crosslinked, and the cable insulators 13A and 13B are insulated. The block 19, the insulating intervening layer, and the semiconductive layer 17 inside the connecting portion are fused and integrated. The heating conditions were that the temperature was raised to 220°C, held for 6 hours, and then cooled.

On the other hand, for comparison, a connection part with the same dimensions using the same cable as in the above example was used, but a two-part insulating block was attached directly onto the semiconducting layer inside the connection part without providing an insulating intervening layer. Assembled. The heating conditions were also the same as in the above example.

A predetermined shielding layer was applied to each of the two types of connections obtained as described above, and an electrical test was conducted. The results are shown in Table-1.

Table 1 * Occurrence at joints of insulating blocks The breakdown value of the connection part according to Example 1 is a value that is fully satisfactory for 27SXV class, and the breakdown location is not caused by the joints of insulating blocks. You can see the effectiveness.

Example 2 The cables to be connected are the same as in Example 1. The conductor is connected using a compression sleeve, and a semiconductive heat shrink tube is placed over it and heated to shrink, and both ends are shaved with glass to form a semiconductive layer inside the connection part that is smoothly connected to the semiconductive layer inside the cable. did. Next, a polyethylene heat-shrinkable tube was placed thereon and heat-shrinked to form an insulating intervening layer. After that, attach the connection insulation block as in Example 1,
An external semiconductive layer was formed at the connecting portion, and a pressurizing tube was placed over the connecting portion to perform pressure heating to effect crosslinking.

The thus obtained connection was disassembled, and the size of the protrusion on the internal semiconducting layer of the connection was examined, and the adhesion between the internal semiconducting layer of the connection and the insulating intervening layer, and between the insulating intervening layer and the insulating bronch of the connection. The force was measured as the interfacial tear force. The results are shown in Table-2.

Table 2: Adhesive strength is the load when a notch is made at the adhesive boundary of a slice sample with a thickness of 0.5 mm as shown in Figure 3, and the sample is torn in the direction of the arrow.

According to this result, the protrusions of the internal semiconducting layer of the connecting portion are sufficiently small, and the adhesive force at each interface is also sufficient.

In the above embodiments, a non-crosslinked insulating block containing a crosslinking agent was used as the connecting portion insulating block, but it is also possible to use a block that is already crosslinked.

[Effects of the Invention] As explained above, according to the present invention, the insulating intervening layer is provided on the internal semiconducting layer of the connecting portion and then the connecting portion insulating block is attached, so that the seam of the insulating block is slightly Even if a gap or level difference occurs, the vA edge intervening layer absorbs it, and no protrusion is formed on the surface of the semiconductive layer inside the connection part. Therefore, a connection part with stable performance and no electrical defects can be obtained.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an embodiment of the connection method according to the present invention, Figure 2 is a perspective view of a connection insulating block used therein, Figure 3 is an explanatory diagram of the adhesive force measurement method, Figures 4 and Figure-
5 is an explanatory diagram showing problems with the conventional connection method. llA・11B=crosslinked polyethylene electrical cable, 12
A-12B: Outer semiconducting layer, 13A/13B: Insulator, 14A-14B: Inner semiconducting layer, 15A-1
5B: Conductor, 16: TL solder, 17: Semiconducting layer inside the connection part, 18: Insulating intervening layer, 19: Insulation block of the connection part,
20: Connecting portion external semiconducting layer. ↓ Figure- Figure-5

Claims (1)

[Claims] 1. After connecting the conductors, provide a connecting internal semiconductive layer on top of it so as to straddle the internal semiconductive layers of the cable on both sides, and then install two In a method for connecting a plastic insulated power cable, which integrates a connection part insulation block and a cable insulator by attaching a connection part insulation block divided into more than 100 parts and heating it, before installing the connection part insulation block, A method for connecting a plastic insulated power cable, characterized by providing an insulating intervening layer on a semiconductive layer inside a connecting part.