JPH0421410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for forming a connection part by a molding method for a crosslinked polyethylene insulated cable (hereinafter referred to as a CV cable).

[Conventional technology and problems] In recent years, the so-called mold joint method has been widely adopted for connecting CV cables because it has excellent reliability at the connection part and can perform the connection work relatively stably. It became.

This mold joint method involves connecting cable conductors and then forming a connecting part insulator on the outer periphery of the connected part by extrusion or tape wrapping.
An external semiconductive layer made of, for example, a heat-shrinkable tube is provided on the outer periphery, and the outside is wrapped with tape or a heat-shrinkable silicone tube, etc., and heated while applying gas pressure to integrate the whole into a mold. It is something.

During this heating molding, if the insulator melts due to imbalance in heat distribution or excessive temperature rise, the crosslinking agent in the insulator tends to migrate into the outer semiconductive layer at the outer periphery due to thermal diffusion. When this crosslinking agent migration phenomenon occurs, the crosslinking agent in the insulator near the outer semiconducting layer becomes diluted, and the degree of crosslinking in that area becomes insufficient. If the degree of crosslinking does not sufficiently reach the required degree of crosslinking as described above, it will have an adverse effect on the electrical properties (withstand voltage performance), mechanical properties (thermal deformation resistance), etc., resulting in a decrease in these properties.

In particular, if the migration of the crosslinking agent occurs at the rising part of the joint, that is, the part where the insulator of the connection part, the cable insulator, and the external semiconducting layer of the connection part are assembled, the migration of the crosslinking agent will occur within the cable insulator. There is a risk that the performance of the rising portion of the joint, which is likely to become electrically unstable, will be significantly deteriorated.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and is intended to sufficiently prevent the migration of the crosslinking agent in the insulator in the mold joint method, and to improve the electrical and mechanical properties. The object of the present invention is to provide a method for connecting CV cables that can form a connection portion with sufficiently excellent characteristics.

[Summary of the Invention] That is, the gist of the present invention is to coat the outer periphery of a connecting portion insulator for a molded connecting portion in a connecting portion of a cross-linked polyethylene insulated cable with an external semiconductive layer, A cross-linked polyethylene insulated cable is provided with an additional layer made of the same material and mixed with the same cross-linking agent as the connection part insulator over a part or the entire outer circumference of the cable, and then connected by heating and pressurizing with a mold. In this connection method, even if the crosslinking agent migration phenomenon occurs, in that case, the crosslinking agent in the attached layer is actively migrated, and the migration of the crosslinking agent from the insulator side is actively prevented. This made it possible.

[Example] The following is a description based on examples.

The figure is an explanatory diagram showing how CV cables are connected by the connection method according to the present invention.

1 is a cable insulator made of cross-linked polyethylene exposed by stripping off the sheath and the outer semiconducting layer; 2 is a conductor connecting pipe connecting the exposed conductor by penciling the cable insulator; 3 Reference numeral 4 indicates an inner semiconducting layer which is connected to the inner semiconducting layer of the cable and coats the outer periphery of the conductor connecting tube, and 4 is a connecting portion insulator, which is formed by tape winding or extrusion as described above.

Reference numeral 6 refers to the external semiconductive layer of the connection part that has already been explained, and although it has recently been increasingly formed using a heat-shrinkable tube, it is not limited to that, and may be formed using conventional methods such as tape wrapping. It's good to wear. Note that 5 is an external semiconductive layer of the cable, and is electrically connected to the connecting portion external semiconductive layer 6 as shown in the figure.

7 is an additional layer containing a crosslinking agent according to the present invention,
For example, it is formed by winding a tape made of the same material as the insulator 4 and containing the same crosslinking agent. Reference numeral 8 denotes the joint rising portion described above, and in this embodiment, an example is shown in which the additional layer 7 according to the present invention is provided at the above-mentioned portion which is likely to become electrically unstable.

If heating and pressure are applied in the state shown in the figure, even if the insulator melts, it will occur first in the outermost attached layer 7, so the crosslinking agent in the attached layer 7 will quickly melt the external semiconductor. layer 6, increasing the crosslinking agent concentration in the outer semiconducting layer 6. As a result, migration of the crosslinking agent from other insulators into the outer semiconducting layer 6 is prevented, and the electrical resistance caused by the dilution of the crosslinking agent in the insulator and the resulting insufficient degree of crosslinking is prevented. This makes it possible to sufficiently prevent deterioration of mechanical properties.

In addition, in order to ensure the above effect, it is desirable that the concentration of the crosslinking agent in the tape for forming the attached layer 7 is slightly higher than the concentration of the crosslinking agent in the connection part insulator. , whereby the migration of the crosslinking agent is realized more quickly and with sufficient concentration.

In the embodiment illustrated above, an example is shown in which the supplementary layer 7 is provided near the joint rising portion 8, but this supplementary layer is not limited to the vicinity of the joint rising portion only, and is not limited to the connecting portion. There is no problem in providing it throughout the entire area. However, when it is provided all around the connection part in this way, it is preferable to partially remove the attached layer after the completion of the crosslinking process in order to form the outer semiconductive layer. Furthermore, the attached layer 7
Needless to say, the method is not limited to the above-mentioned tape winding, and can be modified in various ways, such as forming with a heat-shrinkable tube.

[Effects of the Invention] As described above, according to the CV cable mold connection method according to the present invention, even if the insulator melts during mold heating, the melt is made of the same material, and This occurs first in the auxiliary layer existing at the outermost periphery, and the crosslinking agent in the auxiliary layer takes charge of the migration of the crosslinking agent into the outer semiconducting layer, and the migration of the crosslinking agent from other insulators occurs. Since this prevents this, it is possible to always form connections that are excellent both electrically and mechanically, and the significance of the present invention, which enables the reliability and stability of CV cable connections to be ensured, is enormous. There is something.

[Brief explanation of drawings]

The figure is an explanatory diagram showing an embodiment implementing the connection method according to the present invention. 1...Cable insulator, 2...Conductor connection pipe, 4
. . . Connection insulator, 5. Outer semiconducting layer of cable, 6. Outer semiconducting layer of connection portion, 7. Additional layer containing crosslinking agent, 8. Joint rising portion.

Claims (1)

[Scope of Claims] 1. An outer semiconducting layer is coated on the outer periphery of a connecting portion insulator for mold connection in a connecting portion of a cross-linked polyethylene insulated cable, and the above-mentioned A method for connecting cross-linked polyethylene insulated cables, in which an additional layer made of the same material and mixed with the same cross-linking agent as the connection part insulator is provided, and then heated and pressurized for mold connection. 2. The connection method according to claim 1, wherein the portion where the additional layer is provided is a joint rising portion. 3. The connection method according to claim 1 or 2, wherein the concentration of the crosslinking agent in the attached layer is higher than the concentration of the crosslinking agent in the insulator.