JPH0318216A - Rubber-plastic cable connection - Google Patents

Abstract

PURPOSE:To eliminate the electric defect of the whole line by gradually increasing the insulators of rubber-plastic cables in thickness in the longitudinal direction toward terminals and making the insulators thickest at the cable terminals. CONSTITUTION:The outer diameter of cables 11 and 11' near a connection is gradually increased from the center to both sides of said connection and kept constant to the cutting points of said cables. The insulators of the cables near the connection is thicker than those thereof in the other sections, the cables are peeled into step form at external conductive layers 27 and 27' and insulating layers 28 and 28', and conductors are connected by compression connection with a conductor connection tube 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in rubber-plastic cable connections.

[Conventional technology]

Due to its excellent insulation properties and ease of handling, cross-linked polyethylene cables are rapidly moving toward higher voltages, and 275kV class long-distance lines are being constructed.

Connections are essential for long-distance lines, but 27Sk
For the V class, a two-split mold is placed over the stripped cable insulation, and insulating resin is extruded into the mold using a small extruder, and after shaping into a predetermined shape, the external conductive layer is coated and the extruded insulating layer is The extrusion mold 2 connection part is integrally cross-linked with heat and pressure.

This will be explained in detail using FIG. The cables 1.1', which have been stripped in stages to predetermined dimensions, are compressed and connected using a conductor connecting tube 2, and an internal conductive layer 3 is formed on the conductor connecting tube using semiconductive tape or semiconductive shrink tube. A two-part mold (not shown) is placed over the mold, and an insulating resin is extruded into the mold using a small extruder.

The extruded insulating resin is cut into the shape of a predetermined reinforcing insulator 4, covered with an external conductive layer 5 made of a semiconductive shrink tube, and then heated and molded in a pressurized container under gas pressure.

[Problems to be Solved by the Invention] When extruding the reinforcing insulator, one end of the cable outer conductive layers 7, 7' at the end of the connection part is stripped off, and after extrusion, it is processed into a certain shape together with the reinforcing insulator 4, and then the outer conductive layer is There are the following problems in coating layer 5.

b) Because the edge of the cable wA is scraped twice: before extrusion, that is, when stripping the cable layer, and after extrusion, that is, when forming the reinforcing insulator, the insulation thickness of the cable insulation layer 8,8' at the end of the connection part is particularly thin. Therefore, the necessary insulation thickness may not be achieved.

b) Glass pieces are often used as a tool when scraping off the outer conductive layers 7, 7' or when shaping the surface of the cable insulating layers 8, 8' and reinforcing insulators 4. It is easily scratched, and when the outer conductive layer 5 is coated and crosslinked thereon, the molten outer conductive layer 5 may flow into the fine scratches and become conductive protrusions, resulting in electrical defects. Surface scratches can be smoothed by polishing with sandpaper, but the fine powder of the abrasive rubbed into the paper tends to remain as foreign matter on the cable surface, and if the foreign matter is left behind, If the outer conductive layer is coated and cross-linked, the remaining foreign matter may become conductive protrusions or inhibit interfacial adhesion. In the rubber-plastic cable connection, the thickness of the insulation of the rubber-plastic cable increases smoothly in the longitudinal direction toward the cable terminal, and the thickness of the insulation at the cable terminal is thicker than at other parts. It is characterized by the presence of

According to the present invention, as conceptually shown in FIG. 3, the thickness of the insulation layer 48 of the cable gradually changes from the normal insulation thickness t over a length L' from the end of the connection part toward the center of the connection part. The insulation changes continuously and monotonically to the insulation t' with a predetermined thickness δt, and then remains at a constant thickness t' until the cable is cut.

When stripping the cable, the outer conductive layer is stripped at the part where the insulation thickness is at least thicker than the normal cable part, as shown at 12 and 13 in the figure. Increase the insulation thickness where the external conductive layer is added. As a result, electrical weaknesses were likely to occur due to irregularities or foreign objects that occurred at the interface between the external conductive layer and the cable insulation layer, which were installed in the field, as well as the current electrical weaknesses.

C) The cable insulation layers 8, 8' at the end of the reinforcing insulation layer, which has the thinnest insulation thickness in the connection part, are subjected to thermomechanical strain during the extrusion and crosslinking processes during actual connection work, and the resulting deformation causes wA
The edge thickness tends to decrease, and during cross-linking, the reinforcing insulation layer is exposed to high temperatures to effectively cross-link, and cross-linking residue from manufacturing that remains inside the cable decomposes and forms microvoids. Therefore, the cable's original insulation performance is on the verge of deteriorating.

These factors, acting singly or in combination, make the cable insulation layer 8, 8' at the end of the connection the greatest electrical weakness in the entire connection. In the future, as the insulation thickness of cables is reduced and cables are applied to higher voltage classes, the operating stress of cable insulators will tend to become even higher, and it is urgent to eliminate the above-mentioned weaknesses. It was a challenge.

[Means and actions to solve the problem]

The present invention solves the above-mentioned problems and can alleviate the electrical weaknesses caused by thermomechanical strain and heating effects on the cable insulation, and the cable part at the end of the connection part is connected to the line. It is possible to prevent this from becoming an electrical weak point of the whole.

(Example) The present invention will be described below based on the example shown in the drawings.

FIG. 1 is a sectional view of an embodiment of a rubber-plastic cable connection part according to the present invention. This example is 275kv2
000- crosslinked polyethylene cable was assembled by extrusion molding.

Cable 11. The insulation outer diameter of 11' is 112 mm, the outer conductive layer outer diameter is 115 mm, and the inner conductive layer outer diameter is 58 mm.

On the other hand, the cables 11 and 11' near the connection part have a slope length of 1 from a point 1000 mm on both sides from the center of the connection part.
After the outer diameter gradually increases and becomes thicker at 00+nm, the thickness remains constant until the cable is cut. The outer diameter of the internal conductive layer at the thicker part is the same as the cable, 58nwn.
Insulating layer 28. 28', outer conductive layer 27. 27' are each 10(1) larger than the cable and 122
mm, the value is 12 5 mm. In other words, the insulation thickness of the cable near the connection part is 5 mm thicker than the normal cable part, and the electrical insulation is applied to the parts that are affected by mechanical strain due to insulation surface treatment and extrusion and heat during crosslinking during cable connection work on site. This can prevent potential weaknesses from occurring. Stripping the cable layer is the insulating layer 28. 28
The thicker part of the outer conductive layer 27. 27' and an insulating layer 28. 28', the conductors are connected by compression using the conductor connecting tube 22, and after forming the internal conductive layer 23 thereon, the reinforcing insulator 24 is formed into a predetermined shape, and finally the external Conductive JW25 was coated and cross-linked under heat and pressure. The reinforcing insulator 24 had an outer diameter of 145 mm and a total length L of 790 mm, and the length of the stepped portion of the cable was 445 mm on both sides from the center of the connection.

For comparison, a connection with a conventional structure was fabricated using the same cable. The outer diameter of the reinforcing insulator is 14 5
mm, the length L was 850 mm, and the length l of the step-stripped portion of the cable was 475 mm on both sides from the center of the connection. In both this embodiment and the conventional example, the reinforcing insulator is made of glass when the cable step is stripped.According to the connection technology of the present invention, the reinforcing insulator 34 is removed from the end of the cable as shown in FIG. Extruded to the same thickness as layer 3838' and cable end outer conductive layer 37. It becomes possible to make the outer diameter of the connecting portion outer conductive layer 35 substantially equal to the outer diameter of the outer conductive layer 37'.

When applying this method to an actual cable line, measure the route length accurately in advance, and when installing cables with snaking, determine the manufacturing length by taking into account the required length for meandering, and determine the dimensions of the connection part. Control the extrusion amount and change the thickness of the cable insulation layer. The extrusion amount can be controlled by controlling the screw rotation speed of the extruder.

〔Effect of the invention〕

As explained above, according to the present invention, the thickness of the insulating layer of the rubber-plastic cable increases smoothly in the longitudinal direction toward the cable terminal, and the thickness of the insulating layer at the cable terminal is thicker than at other parts. Since it is also thicker, it has the excellent effect of preventing the cable section at the end of the connection section from becoming an electrical weak point of the entire line.

A piece was used. Furthermore, the extrusion temperature of the reinforcing insulator was 120°C on both sides, the crosslinking conditions were also the same, and the heating influence range was 600 mm from the center of the connection part to both sides.

Table 1 shows the results of four voltage tests on the connection parts manufactured as described above.

The charging method was to hold AC 610kv in steps for 12 hours, then apply a 50kV step amp and hold it for 1 hour.
Thereafter, the power was increased in steps of 50 kV in the same manner.

As shown in Table 1, the sample connected using the conventional technology is 860
All of them were destroyed at the external conduction processing section at ~910kV.

On the other hand, the samples connected by the method of the present invention were 1010 to 106
It was destroyed at an extremely high value of 0kV, and all of the fractured locations were other than the external conduction treatment section, confirming the effectiveness of the present invention.

Table 1

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of one embodiment of the rubber-plastic cable connection part according to the present invention, Fig. 2 is a longitudinal cross-sectional view of another embodiment, and Fig. 3 is an explanatory diagram of the cable terminal part used in the present invention. , FIG. 4 is a longitudinal sectional view of a conventional example of a rubber-plastic cable connection section. 1 1'11.11'...Cable, 22
2... Conductor connection pipe, 3, 23... Internal conductive layer,
4, 24, 34... reinforcing insulator, 5, 7.
7', 25, 27. 27'35, 37.
37'...Outer conductive layer, 8.8'28.28'
38. 38'. 4B...Insulating layer, 12.13.
... Stripping position.

Claims (1)

[Claims] In a rubber-plastic cable connection where rubber-plastic cables are connected to each other, the thickness of the insulation of the rubber-plastic cable increases smoothly in the longitudinal direction toward the cable end, and the thickness of the insulation at the cable end increases with the other thickness. A rubber-plastic cable connection section characterized by being thicker than the section.