JPS6212318A - Formation of connection of crosslinked polyethylene insulated power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 of a V cable (V cable) in which a reinforcing insulating layer of a connection part is formed by extrusion molding using a metal mold.

(Prior Art and Problems to Be Solved) The performance of extrusion molded connections for CV cables is highly dependent on the degree of adhesion between the cable insulation layer and the reinforcing insulation layer formed by extrusion.

FIG. 1 shows an explanatory diagram of a method of forming a connection part of a C■ cable by extrusion molding. In the drawings, (1) indicates the cable insulation layer made of cross-linked polyethylene, ■ indicates the cable internal semiconducting metal on the cable conductor (3), 4) indicates the connection sleeve of the cable conductor (3), and ■ indicates the cable conductor (3). This is a cable conductor connection sleeve (a semiconducting layer inside the connection part applied over Φ and over the cable's internal semiconducting metal) to alleviate the electric field at the connection part.

It contains the conductor connection part of the above cable, and the cable insulation layer (
Mold 0 is installed across 1), and an uncrosslinked polyethylene mixture mixed with a crosslinking agent is injected into the internal space of the mold (6) using an extruder, and then heated and pressurized to fill the internal space ①. The injected polyethylene is crosslinked and integrally molded to form a reinforcing insulating layer.

In forming the writing reinforcing insulating layer, the process of injecting the polyethylene mixture into the mold ■ is called the extrusion process, and the process of crosslinking and integrally molding the polyethylene mixture is called the crosslinking process.
Conventionally, in the extrusion process, the polyethylene mixture was simply injected into the mold (6) using an extruder, and the degree of adhesion at the interface between the cable insulation layer and the reinforcing insulation layer, which is important for the performance of the connection part, was determined in the crosslinking process. It has been thought that this depends on conditions such as processing and heating.

However, as a result of a deep study by the inventors of the present invention regarding the degree of adhesion at the interface, it was discovered that factors of the extrusion process also have a large influence on the adhesion at this interface. That is,
In order to improve interfacial adhesion, it is important to sufficiently heat the cable insulation layer surface (A) in the mold ■ before injecting the polyethylene mixture into the mold ■. It was confirmed that the degree of adhesion at the interface was influenced by the temperature conditions of the cable insulation layer surface (A).

(Example) As shown in Fig. 1, the cable conductor connection part is included and the cable is insulated! The mold 6) is set across (1), and before injecting the uncrosslinked polyethylene mixture containing a crosslinking agent into the internal space ■ of the mold ■, a heater (not shown) attached to the mold ■ is used. ) etc. to make the cable insulation layer surface (A) reach a temperature higher than the melting point temperature (temperature measured by a differential calorimeter) of the crosslinked polyethylene that is the insulator. Inject the polyethylene mixture through the mixture injection hole (■).

By doing this, the interface between the cable insulating layer (1) and the reinforcing insulating layer in the mold ■ is already thermally fused at the end of the extrusion process of the polyethylene mixture, and in the subsequent crosslinking process. Problems such as peeling can be prevented.

Note that when heating the cable insulation surface (A), the temperature is lowest at the X mark point near the conductor, so at least
It is necessary that the marking point reaches a temperature higher than the melting point of the crosslinked polyethylene.

Inh j'l: , 154KVs 2000m/ ('
) The results of AC breakdown voltage measurements for two types of CV cable extrusion mold connections are shown in the table below. Note that the melting point temperature of crosslinked polyethylene is 0°C.

Table (Effects of the Invention) According to the method for forming a connection part of the present invention described above, the surface of the cable insulation layer in the mold is brought to a temperature equal to or higher than the melting point of crosslinked polyethylene before injecting the resin into the mold. Therefore, during the extrusion process, the interface between the cable insulation layer and the reinforcing insulation layer is already thermally fused and has considerable adhesive strength, and this adhesion is maintained even during the crosslinking process, preventing interfacial peeling. can be prevented from occurring.

Therefore, the variation in breakdown voltage is small, and breakdowns are less likely to occur especially at low voltages.

[Brief explanation of drawings]

FIG. 1 shows an explanatory diagram of a method of forming a connection part by extrusion molding of a Cv cable. 1... Cable insulation layer, 3... Cable conductor, 4...
...Conductor connection sleeve, 6...Mold, A...Cable insulation layer surface inside the mold.

Claims (2)

[Claims] (1) In a method of forming a reinforcing insulating layer at the connection part of a cross-linked polyethylene insulated power cable by extrusion molding using a mold, the surface of the cable insulating layer in the mold is heated during preheating before injecting resin into the mold. A method for forming a connection part of a cross-linked polyethylene insulated power cable, the method comprising making the connection part of a cross-linked polyethylene insulated power cable reach a temperature equal to or higher than the melting point of the cross-linked polyethylene. (2) The connecting portion of a cross-linked polyethylene insulated power cable according to claim 1, wherein at least the surface of the cable insulation layer near the conductor connecting portion is made to reach a temperature higher than the melting point of the cross-linked polyethylene. Formation method.