JPS59171483A - Method of heating polyolefin insulated cable at time of producing connector - 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 The present invention relates to a heating method during thermal crosslinking of a polyolefin insulated cable molding P connection part.

Conventionally, for example, for connection parts of cross-linked polyethylene insulated cables (hereinafter referred to as "Cv cables") of 154 KV or higher, a molding method using polyolefin containing a cross-linking agent, which is the same material as the cable insulator, has been used to improve electrical properties and reliability. It has been adopted. Currently, the connections for 154KVCV cables are manufactured by laminating and wrapping polyolefin tape containing a chemical crosslinking agent and using a gas pressurized molding method, and are being applied to actual lines. Furthermore, the connection part for 275KVCV cable has further improved quality and electrical performance.
In addition to the molding method in which polyolefin, which is the same material as the cable insulator, is laminated and wrapped with polyolefin tape, it is manufactured by a polyolefin extrusion molding method or a molding method using block-molded polyolefin. In such cases, since the insulation layer at the connection part is thick and the cable conductor is a dog-sized conductor, the temperature inside the connection part will not be enough to cause cross-linking if only the heating source from the mold is used when molding the insulator for thermal cross-linking. The temperature cannot be raised to the required temperature for the reaction, resulting in clogging, which is one of the causes of poor quality. Therefore, there is a need for a heating method that can effectively raise the temperature inside the Cv cable connection portion to a required temperature.

An object of the present invention is to provide a heating method that can maintain a temperature rise inside the connection part at a predetermined temperature during heat crosslinking of a polyolefin insulated cable mold connection part.

That is, in the present invention, when manufacturing a polyolefin insulated cable connection part, the connection part of a polyolefin insulated cable is made of a polyolefin insulator containing a crosslinking agent made of the same material as the cable insulator, and is heated under pressure in a heating device. In the heating method, a preheating device is arranged on the surface of the cable on both sides of the heating device at a length of 50 times or more the outer diameter of the conductor of the cable, and the heating temperature of the heating device is set to 16.
This is a heating method for producing a polyolefin insulated cable connection part, which is characterized by heating the C connection part by maintaining the surface temperature of the cable at 0C to 280C and by using the preheating device described above at 80C to 120C. .

Hereinafter, one embodiment of the present invention shown in FIG. 1 will be described in detail.

Fig. 1 is a side sectional view showing one embodiment for carrying out the method of the present invention, and Fig. 2 is a side sectional view showing an example of carrying out the method of the present invention. FIG.

In FIG. 1, a heating crosslinking mold P mold 2 is placed at the connection portion of the CV cables l. Heating crosslinking mold r mold 2
is provided with a heating device 3, for example an electric heating coil.

The connection part of the CV cable 1 is made by connecting the cable conductors of both cables using a method such as a conductor connecting tube or conductor welding, and then providing an internal semiconducting layer using semiconductive heat shrink tubing, etc., and an insulating layer on the outside. An outer semiconducting layer is provided. The insulating layer is made of the same polyolefin material as the cable insulating layer, and is composed of a polyolefin Teso containing a crosslinking agent, a block, or a polyolefin extruded from an extrusion device. Further, the outer semiconductive layer of the insulating layer is composed of a semiconductive polyolefin heat-shrinkable tube, a semiconductive polyolefin tape, a molded semiconductive polyolefin sheet, a tube, or the like.

The heating crosslinking mold P mold 2 is placed in the connection part configured in this way, and the mold 2 is heated under pressure to 160°C to 280°C.
In this case, the cables 1 on both sides of the heating crosslinking mold P mold 20
A preheating device 4 is provided on the surface of the cable, and in this case, the set length L of the preheating device 4 in the longitudinal direction of the cable is 50 times or more the outer diameter d of the cable conductor. If you do this, mold 2
This prevents the heat from dissipating in the length direction of the cable l, and the temperature rise inside the connection part can be maintained at a predetermined temperature.

The surface temperature of the cable is maintained at 80 to 120°C by cable surface heating devices 4 provided at both ends of the molding P mold 2.

In addition, in the above embodiment, if the connection part is heated to 160 to 280 °C only by the heating source of the mold 2 without preheating, heat dissipation is large in the length direction of the cable conductor, and the connection part The internal temperature rise becomes insufficient. Furthermore, if the length L of the preheating device is less than 50 times the outer diameter d of the cable conductor, dissipation in the length direction of the cable conductor cannot be prevented as described above.
The temperature rise inside the connection is insufficient. These circumstances are shown in the graph of Figure 2.

The results shown in FIG. 2 are the values obtained when a 2000-dog size conductor cable was used, the heating temperature of the mold was 200°C, and the heating temperature of the preheating device was 80°C. As is clear from this graph, it can be seen that a desirable internal temperature of the connection portion can be obtained when the length of the preheating device is 50 d or more.

Furthermore, if the preheating device is not placed close to the mold as in the present invention and there is an unheated part between the end of the mold and the preheating equipment, heat dissipation due to this unheated part will be reduced. Therefore, the temperature rise inside the connection part is not sufficient.

On the other hand, if the heating temperature is set between 280°C and 350°C using only the mold 2 without providing a preheating device as described above, the temperature rise inside the connection part will be at a predetermined value. In the case of high temperature, mold internal pressure (2~l OKg/iG
) is added to the connection part, it is unfavorable from a safety point of view as it may impair the decrease in the mechanical strength of the connection part.If the polyolefin insulation is exposed to high temperatures such as 280℃ to 350℃ for a long period of time, Such an embodiment is undesirable because it causes thermal deterioration and increases the thermal expansion of the polyolefin insulator, making it difficult to extrude the insulator.

As described above, according to the present invention, by simply adding preheating by heating from above the cable sheath, insufficient temperature rise inside the connection part as in the conventional case can be prevented.
The crosslinking reaction can be carried out completely and a homogeneous connection can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows a heating device 11 for carrying out the present invention.
Cable, 2...Mold, 3...Mold heating device, 4
...Preheating device. Bamboo shoots 1 Diagram Z Diagram The shape of the bone J and the winter length

Claims (1)

[Claims] (1) The connection part of the poly first fin insulated cable is made of a polyolefin insulator containing a crosslinking agent of the same material as the cable insulator, and the poly first/fin insulated cable is connected by applying pressure and heating in a heating device. In the heating method when manufacturing the part, a preheating device is placed on the surface of the cable on both sides of the heating device at a length of at least 50 times the outer diameter of the conductor of the cable, and the heating temperature of the heating device is set to 160 to 280.
A heating method for manufacturing a polyolefin insulated cable connection part, characterized by heating the connection part by maintaining the surface temperature of the cable at 80C to 120C using the preheating device.