JPH061937B2 - Cable mold joint construction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold joint method, and in particular, among electrodes divided into two parts of an outer semiconductive layer, the adhesion of the inner electrode is improved and The present invention relates to a method for improving the breakdown voltage.

<Prior Art> In a mold joint portion of a cable, for example, a CV cable, an outer semiconductive layer is generally provided,
In this outer semiconductive layer, one that is continuous over the entire length of the joint portion and one that is divided into two along the circumferential direction at appropriate portions are laminated in a lap shape with their ends insulated from each other. There is something.

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

<Problems to be Solved by the Invention> However, when such a divided structure is adopted, stress such as electric field concentration is likely to concentrate at the end of the outer semiconductive layer. Careful attention is required for molding and the like, and the configuration of the end portion occupies an important position in improving the breakdown voltage.

In fact, according to the tests and studies conducted by the present inventors, voids are generated at the ends of the outer semiconductive layer, particularly the ends of the inner electrodes that enter the inside during molding, due to microdelamination, or due to shape deformation, protrusions or sharp points. It has been found that if a shaped part or the like is formed, the electric machine is easily destroyed due to this. In particular, in recent years, the voltage of CV cables has been rapidly increased, and improvement in this respect is strongly desired.

Therefore, the present inventors have studied more deeply, and as a technique for further improving the adhesiveness of the inner electrode end portion of the outer semiconductive layer, the same material (same or similar material as the base resin used for this inner electrode It has been found that a resin tape of (1) is wound in such a manner as to surround the inner electrode, and then the entire joint is heated and fusion-molded to form a joint having excellent adhesiveness.

The present invention is thus made from the viewpoint.

<Means for Solving the Problem and Its Action> The feature of the present invention lies in that the molded resin insulator 6
The outer semiconductive layers 7 and 8 which are coated on the outer circumference of the are divided into two along the circumferential direction, and one end of the outer semiconductive layer 7 only enters the inside, and the other end is fixed on top of this. Before covering the inner electrode 7a that enters inside the outer semiconductive layers 7 and 8 in the mold joint portion of a cable that is stacked in a lap shape while maintaining an insulation interval, the inner side of the inner electrode 7a and the mold resin insulator are covered. A resin tape 10 made of the same or the same material as the base resin used for the inner electrode 7a is wound over the outer circumference of 6, and then,
The inner electrode 7a is covered with the inner electrode 7a.
And the resin tape 10 on the molded resin insulator 6 is rewound on the resin tape 10, and then the entire joint portion is heated and melted to mold the cable.

The composition of the external semiconductive layer used in the present invention includes ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA) and the like bases. Resin, conductive powder such as carbon or metal, and some cross-linking agents such as dicumyl peroxide (DCP), 2,5-dimethyl-
2,5-di (t-butylperoxy) hexyne-3,
Examples include those obtained by adding 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and the like. The amount of each of these components mixed depends on the materials that can be used, but the conductive powder 10 is added to 100 parts by weight of the base resin.
˜70 parts by weight and 0.2 to 1 parts by weight of the cross-linking agent, and in any case, when it is coated on the mold resin insulator as the external semiconductive layer, its gel fraction (in xylene at 110 ° C. It depends on the extraction method when immersed for 24 hours) is 10 to 50
It is good to adjust it so that it is in the range of%. This is because when the gel fraction is less than 10%, the adhesiveness with the mold resin insulator is good, but the degree of cross-linking is insufficient, the shape retention is poor, and the ends are crushed, resulting in protrusions and sharp points. Shaped parts are likely to occur,
It is a cause of electric breakdown. Also, the gel fraction is 5
When it exceeds 0%, the shape retention is enhanced by a sufficient degree of crosslinking, but the adhesiveness with the mold resin insulator deteriorates, and voids due to minute peeling etc. tend to occur at the ends, and electrical resistance is also expected. This will cause destruction.

Further, the resin tape wound around the inner electrode of the outer semiconductive layer is a tape for interfacial adhesion reinforcement for favorably adhering the inner electrode to the insulator, and its material is the same as or similar to that of the outer semiconductive layer. Use a material made from. Good adhesion can be obtained by selecting this material.

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

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

In the method of the present invention, the coating portions (insulators, etc.) 2 and 2 of both connection end portions to which the cables F and F are to be connected are scraped off (pensin ring treatment) and exposed, and both conductors 1 and 1 are piped. The pressure-bonding sleeve 3 is inserted from both sides into a metal-shaped pressure-bonding sleeve 3 and then the pressure-bonding sleeve 3 is crushed to first perform conductor connection.

Next, wind a semi-conductive tape around this connection part,
It is heated and melted to be crosslinked to form the crosslinked mold inner semiconductive layer 4. Of course, this mold inner semiconductive layer 4 is connected to the inner semiconductive layers 5 and 5 on the cables F, F side.

After that, for example, an uncrosslinked composition tape containing a crosslinking agent is wound around this portion to form the insulator 6. When forming the insulator 6, in addition to the tape winding,
For example, an extrusion molding die may be set in this portion, and the molding resin may be extruded as the insulator 6 by a usual method.

A semiconductive tape is wrapped around the outer periphery of the insulator 6 or a semiconductive mold tube is attached to form the outer semiconductive layers 7 and 8 divided into two parts. At this time, the inner electrode 7a of the one outer semiconductive layer 7 is put inside, and the outer electrode 8a of the other outer semiconductive layer 8 is superposed on the inner electrode 7a in a lap shape while maintaining insulation at regular intervals.

At this time, as shown in FIG. 2, a base resin used for the inner electrode 7a is used for the purpose of improving the interfacial adhesion with the mold outer semiconductive layer 7, particularly, the inner electrode 7a portion with the mold resin. A resin tape 10 of the same material (the same or the same material) is wound so as to surround the inner electrode 7a.

The method of enclosing the resin tape 10 is not particularly limited,
For example, it can be performed by the following method.

That is, for example, one side of the resin tape 10 is halved in the circumferential direction on one side (on the right side in FIG. 1) on the insulator 6 which is already formed in a mold shape by winding up a polyethylene tape containing a crosslinking agent. It is wrapped with a wrap, and the semiconductive mold tube of the outer semiconductive layer 7 is attached so that the inner electrode 7a of the outer semiconductive layer 7 is placed thereon. next,
The second resin tape 10 from the top is also wound in 1/2 wrap, and is covered on the upper side of the inner electrode 7a, and is overlapped on the first resin tape 10. Then, a polyethylene tape containing a cross-linking agent forming the insulator 6 is wound up to a predetermined thickness, and finally a semiconductive mold tube of the outer semiconductive layer 8 is attached, and the outer electrode 8a thereof is superposed just on the inner electrode 7a. Just match. Alternatively, only the second resin tape 10 may be wound in a 1/2 wrap.

The tip shape of the inner electrode layer 7a is preferably chamfered to the outside as shown in FIG. Of course, these outer semiconductive layers 7 and 8 are also connected to the outer semiconductive layers 9 and 9 on the cables F and F sides.

On the outer semiconductive layers 7 and 8 thus formed,
Further, it is pressed and wound with a pressing tape, then set in a mold for molding, and heated at 180 ° C. for 3 hours under a pressure of nitrogen gas of 6 kg / cm ² , for example, and the above-mentioned uncrosslinked or insufficient crosslinking is achieved. The insulator 6 and the external semiconducting layer 7.8 are melt-molded to obtain a final degree of crosslinking (gel fraction 60 to 8).
Lead to 5%). Final cross-linking of the outer semiconductive layers 7 and 8 is performed by migration of the cross-linking agent from the mold resin portion of the insulator 6.

Further, in this molding, the outer semiconductive layers 7 and 8, particularly the inner electrode 7a, are composed of the above-mentioned gel fraction (10 to 50%), and the upper and lower parts are the outer semiconductive layer 7 and the outer semiconductive layer 7, respectively. Since the resin tape 10 is surrounded by the resin tape 10 of the same material, the resin tape 10 is firmly bonded to the inner electrode 7a, and at the same time,
Since it has a shape when embedded as a kind of anchor in the insulator 6, it also adheres very well to the insulator 6 and does not lose its shape even under pressure of nitrogen gas. Therefore, voids, protrusions, pointed portions, etc. are not generated, 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 interfacial adhesion reinforcement satisfies the conditions of the present invention for the mold joint method (Examples ~) and the conditions of the present invention. No mold joint method (Comparative example ~
) Was carried out.

The cables used here are CV cables (15 KV, 12
It was 00 mm ² ).

The AC breakdown voltage value was examined for the joint portion formed by each of the above mold joint construction methods. This test was conducted for two samples per one construction method. The results are also shown in Table 1 above.

From Table 1 above, in the case of Examples 1 to 3 of the present invention, a high AC breakdown voltage value was obtained, and the breakdown location was often other than the inner electrode tip of the outer semiconductive layer. On the other hand, when there is no resin tape for reinforcing the interfacial adhesion as in Comparative Examples 1 to 3, it can be seen that the AC breakdown voltage value is low and the breakdown occurs frequently at the inner electrode tip portion.

<Effects of the Invention> As is apparent from the above description, according to the present invention, the inner electrode of the outer semiconductive layer is constituted only by the outer semiconductive layer, and without using a special member, for interfacial adhesion reinforcement. Since it is only wrapped with a resin tape to surround it, the adhesion between the inner electrode and the insulator is greatly improved and improved, and the occurrence of protrusions and pointed parts due to bolts and shape deformation due to minute peeling is minimal. The mold joint of the cable has excellent electrical properties, and the cost of the member is low because no special member is required. Moreover, it can be handled simply by wrapping the resin tape. The construction method can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a cable mold joint method according to the present invention, and FIG. 2 is an enlarged sectional view showing an example of an inner electrode of an outer semiconductive layer used in the method shown in FIG. Is. In the figure, F, F ... Cable, J ... Joint, 1, 1 ... Conductor, 2, 2 ... Cover (insulator), 3 ... Crimping sleeve, 4 ... inner semi-conductive layer, 6 ... molded resin insulator, 7, 8 ... outer semi-conductive layer, 7a ... inner electrode, 8a ... outer electrode, 10 .... Resin tape,

Claims (1)

[Claims] 1. An outer semiconductive layer 7, 8 coated on the outer periphery of a molded resin insulator 6 is divided into two along the circumferential direction, and an end portion consisting of only one outer semiconductive layer 7 enters inside, In the mold joint portion of the cable, on which the other end portion is overlapped in a lap shape while keeping a constant insulation interval, the inner electrode 7a which enters inside the outer semiconductive layers 7 and 8 is formed.
Before covering the inner electrode 7a and the outer periphery of the molded resin insulator 6, a resin tape 10 made of the same or similar material as the base resin used for the inner electrode 7a is wound around before covering the Then, the inner electrode 7a
And further winding the resin tape 10 on the inner electrode 7a and on the resin tape 10 on the molded resin insulator 6 again, and then melting and melting the entire joint portion for molding. Mold joint method for cables.