JPH0265611A - Technique of molded joint of cable - Google Patents

Abstract

PURPOSE:To improve adhesion by winding the inside electrode of an outer semi-conductive layer through a resin tape composed of same or identical material to the base resin composing the inside electrode then thermally fusing the entirety of joint and molding. CONSTITUTION:Outer semi-conductive layers 7, 8 splitted into two are formed on the outer circumference of an insulator 6. The inside electrode 7a of one outer semi-conducting layer 7 is placed at the inside then the outer electrode 8a of the other semi-conductive layer 8 is lapped thereon through a predetermined insulation gap. At this time, a resin tape 10 composed of same material as the base resin composing the inside electrode 7a is wound around the inside electrode 7a. Then a stop tape is applied on the outer semi-conductive layers 7, 8 thereafter a yet-crosslinked or insufficiently cross-linked insulator 6 and the outer semi-conductive layer 7, 8 are fusion molded and cross-linked to the final stage. By such arrangement, a high breakdown-proof voltage can be achieved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a mold joint construction method, and in particular improves the adhesiveness of the inner electrode of the two divided electrodes of the outer semiconducting layer. This relates to a construction method that aims to improve breakdown voltage.

<Prior Art> Generally, an external semiconducting layer is provided at the mold joint of a cable, such as a C■ cable.
This external semiconducting layer is either continuous over the entire length of the joint or divided into two parts along the circumferential direction at appropriate points, which are overlapped in a ramp shape with their ends insulated. There is something.

The reason for adopting such a two-division method is to reduce the potential rise in the sheath caused by electromagnetic induction and the sheath circuit loss.

<Problems to be Solved by the Invention> However, when such a divided structure is adopted, stress such as electric field concentration tends to be concentrated at the edges of the external semiconducting layer, so it is difficult to select and shape the edge composition material. Careful attention must be paid to molding, etc., and the configuration of the end portions plays an important role in improving breakdown voltage.

In fact, based on the tests and research conducted by the present inventors, it has been found that voids are generated at the edges of the outer semiconducting layer, especially at the edge of the inner electrode that goes inside during molding, due to micro-peeling, etc., or protrusions or sharp points are formed due to shape deformation. It has been found that if a shape or the like is formed, electrical breakdown easily occurs due to this. In recent years, the voltage of Cv cables has been rapidly increasing, so improvement in this respect is strongly desired.

Therefore, the inventors of the present invention conducted a deeper study and found that a technique for further improving the adhesion of the inner electrode end of the outer semiconducting layer was made by using the same material (same or similar material) as the base resin used for this inner electrode. ) was wound around the inner electrode, and then the entire joint was heat-fused and molded, it was discovered that a joint with excellent adhesiveness could be obtained.

The present invention has been made from this viewpoint.

<Means for Solving the Problems and Their Effects> The feature of the present invention is that the external semiconductive layer coated on the outer periphery of the molded resin insulator is divided into two along the circumferential direction, and one The inner electrode of the outer semiconducting layer is connected to the inner electrode G at the molded joint part of the cable, on which the end part goes inside and the other end part is overlapped in a lap shape while maintaining a constant insulation interval. A cable mold joint construction method involves wrapping the cable in a resin tape made of the same or similar material as the base resin used, and then heating and melting the entire joint part to mold it.

The composition of the outer semiconductive layer used in the present invention includes bases such as ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), and ethylene-acrylic acid copolymer (EAA). In the resin, conductive powder such as carbon or metal, and some crosslinking agents such as dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,2
゜5-dimethyl-2,5-di(t-butylperoxy)
Examples include those made by adding hexane or the like.

The amount of each of these components to be blended is approximately 10 to 70 parts by weight of the conductive powder and 0.2 to 1 part by weight of the crosslinking agent for 100 parts of the base resin, although it depends on the materials used. However, when coated on a molded resin insulator as an external semiconducting layer, its gel fraction (according to the extraction method when immersed in xylene at 110°C for 24 hours) is 10
It is advisable to adjust it to a range of ~50%. This is because when the gel fraction is less than 0%, the adhesion to the molded resin insulator is good, but the degree of crosslinking is insufficient, so the shape retention is poor, the edges are dipped, etc., and protrusions and This is because sharp portions are likely to form, causing electrical breakdown. In addition, when the gel fraction exceeds 50%, the shape retention is strengthened due to a sufficient degree of crosslinking, but the adhesion with the molded resin insulator deteriorates, causing voids at the edges due to micro-peeling, etc. This is because it is easy to occur and can cause electrical breakdown.

In addition, the resin tape wrapped around the inner electrode of the outer semiconductive layer is a tape for reinforcing interfacial adhesion to ensure good adhesion of the inner electrode to the insulator, and its material is the same or of the same type as the outer semiconductive layer. Use materials made of By selecting this material, good adhesion can be obtained.

Next, a specific example of the construction method of the present invention will be explained with reference to FIG.

In the figure, F and F are cables that are connected to each other, and J is a joint portion thereof.

In the construction method of the present invention, the covering portions (insulators, etc.) 22 of the connecting ends of the cables F and F to be connected are scraped off (benzine ring treatment) and exposed, and both door bodies 1 are formed into a cylindrical shape or the like. Insert it into the metal crimp sleeve 3 from both sides,
After this, the crimp sleeve 3 is crushed and conductor connections are first made.

Next, wrap a semiconductive tape around this connection, for example.
The mold is melted and crosslinked by heating to form a semiconductive layer 4 inside the mold using the crosslinking method. Of course, this mold internal semiconductive layer 4 is connected to the cable F and the internal semiconductive layers 5, 5 on the F side.

Thereafter, an insulator 6 is formed by wrapping, for example, an uncrosslinked composition tape containing a crosslinking agent around this portion. In addition to this tape wrapping, in forming the insulator 6,
For example, an extrusion mold may be set in this part and the molded resin may be extruded as the insulator 6 using a normal method.A semiconductive tape may be wrapped around the outer periphery of the insulator 6. A semiconductive molded tube is attached to form a two-part outer semiconductive layer 7.8. At this time, the inner electrode 7a of one outer semiconductive layer 7 is placed inside, and the outer electrode 8a of the other outer semiconductive layer 8 is overlapped thereon in a lap shape while maintaining insulation at a constant interval.

At this time, as shown in FIG. 2, in order to improve the interfacial adhesion between the mold outer semiconductive layer 7, especially the inner electrode 7a portion, and the mold resin, the base resin used for the inner electrode 41a is A resin tape 10 made of the same material (same or similar type of material) is wound around the inner electrode 7a.

The method of enclosing with this resin tape 10 is not particularly limited, but
For example, this can be done by the following method.

That is, for example, a −th sheet of resin tape 10 is placed 1/2 in the circumferential direction on one side (on the right side in FIG. 1) of the insulator 6, which has already been formed into a mold shape by wrapping polyethylene tape containing a crosslinking agent, etc. The semiconductive mold tube of the external semiconductive layer 7 is attached so that the inner electrode 7a of the external semiconductive layer 7 is placed on top of this. Next, apply the second resin tape 10 from the top to 1/2
Wrap it up and cover it over the inner electrode 7a, and overlap it with the -th resin tape 10. After this, polyethylene tape containing a crosslinking agent, etc., which forms the insulator 6, is rolled up to a predetermined thickness, and finally, the semiconductive molded resin part of the external semiconductive N8 is attached, and the external electrode 8a is placed exactly on the inner electrode 7a. Just match it. Also,
It is also possible to wrap only the second resin tape 10 with a 1/2 lamp.

The tip shape of this inner electrode 7a is preferably as follows:
It is best to provide a smooth chamfer on the outside as shown in Figure 2. Of course, these external semiconducting N7゜8 cables F,
Connection processing is performed with the external semiconducting layer 9.9 on the F side.

On the outer semiconducting layers 7 and 8 formed in this way,
Further, the uncrosslinked or insufficiently crosslinked insulation is wrapped with a restraining tape, and then a molding die is set and heated under pressure at 180°C for 13 hours under a nitrogen gas pressure of 6 kg/cm2. Body 6 and external semiconducting N7
, 8 parts are melt-molded to reach the final degree of crosslinking (gel fraction 60-85%). Note that the outer semiconducting layers 7 and 8
The final crosslinking of the part takes place by migration of the crosslinking agent from the molded resin part of the insulator 6.

In addition, during this molding, the outer semiconductive layer 7°8, especially the inner electrode 7a, has a composition with the above-mentioned gel fraction (10 to 50%), and the upper and lower sides are the same as the outer semiconductive layer 7. Since it is surrounded by the resin tape 10 made of the same material, this resin tape 10 is firmly adhered to the inner electrode 7a, and at the same time,
Since it is buried in the insulator 6 as a kind of anchor, it is bonded to the insulator 6 extremely well and does not lose its shape even under nitrogen gas pressure. Therefore, there is no generation of voids, protrusions, sharp parts, etc., and as a result, a high breakdown voltage can be obtained.

<Example> As shown in Table 1, the combination of the inner electrode composition and the resin tape for reinforcing interfacial adhesion resulted in the mold joint construction method (Examples ■ to ■) satisfying the conditions of the present invention and the method of the present invention. Mold joint construction method that does not meet the conditions (comparative example ■～■
) was carried out.

Here, the cable used is C■ cable (154KV,
1200mm”).

AC breakdown voltage values were investigated for the joint parts formed by each of the above mold joint construction methods. This test was conducted on two samples per construction method. The results are also listed in Table 1 above.

From Table 1 above, high AC breakdown voltage values were obtained in Examples 1 to 2 of the present invention, and the breakdown location was often other than the tip of the inner electrode of the outer semiconducting layer. On the other hand, when there is no resin tape for reinforcing interfacial adhesion as in Comparative Examples (1) to (2), the AC breakdown voltage value is also low, and it can be seen that breakdown occurs frequently at the tip of the inner electrode.

<Effects of the Invention> As is clear from the above description, according to the present invention, since the inner electrode of the outer semiconducting layer is surrounded by the resin tape for reinforcing interfacial adhesion, the adhesiveness between the inner electrode and the insulator is improved. It is possible to obtain a mold joint construction method for cables with excellent electrical properties, and the occurrence of voids due to micro-peeling, protrusions, sharp parts, etc. due to shape deformation can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view showing one embodiment of the cable mold joint construction method according to the present invention, and Fig. 2 is an enlarged cross-sectional view showing an example of the inner electrode of the outer semiconducting layer used in the construction method of Fig. 1. It is a diagram. In the figure, F, F...cable, J...joint part, l, ■...conductor, 2.2...sheathing part (insulator), 3...crimping sleeve, 4...Inner semiconducting layer, 6...Mold resin insulator, 7.8...Outer semiconducting layer, 7a...Inner electrode, 8a...Outer electrode, 10 ...resin tape,

Claims (1)

[Claims] The outer semiconducting layer that covers the outer periphery of the molded resin insulator is divided into two parts along the circumferential direction, one end goes inside, and the other end is wrapped in a lap shape while maintaining a constant insulation interval. At the molded joint part of the cable that is overlapped with the cable, the inner electrode of the outer semiconductive layer is wrapped in a resin tape made of the same or similar material as the base resin used for the inner electrode, and then the entire joint part is wrapped. A cable mold joint construction method characterized by heating and melting and molding.