JPH07118355B2 - Molding method for intermediate connection of rubber and plastic insulation cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has improved the problem of deterioration of electrical characteristics during molding of an intermediate connecting portion of a rubber or plastic insulated cable.

Generally, the following method is adopted as a method for molding the intermediate connecting portion of the rubber or plastic insulated cable. This will be described with reference to FIG. First, the two cables A and B to be connected are ground in a pencil shape to expose the conductor, and then the conductors are electrically connected by a compression sleeve or the like. Subsequently, an inner semiconductive layer is sequentially formed on the outer side with a semiconductive shrinkable sleeve or the like, a tape insulating layer with a polyethylene tape or the like is sequentially formed on the outer side, and an outer semiconductive layer is formed thereon in some cases. After that, in order to heat-bond the formed laminated connection portion 1 to integrate the whole, the metal pressure vessel 2 is covered and attached to the outside of the connection portion, and a heater is installed in the vessel. Molding is performed by embedding or heating by directly placing a heater on the connection portion, or by heating and pressurizing by a method of pressurizing and pressurizing gas into the container.

However, in the case of each of the above methods, since the metal pressure vessel 2 is also heated by the heater at the same time, the heated metal pressure vessel 2 is connected to the cable surface 3 near the connection portion.
Since the cable insulating layer is in contact with 3 ', the cable insulating layer in that portion is heated at an abnormally high temperature for a long time. Therefore, since the insulating layer in this portion is subjected to an abnormal heat history for a long time, when the cable was subjected to an electric breakdown test, the cable was often broken at a low value.

In view of the current situation, the present invention establishes a method of forming an intermediate connection portion without deteriorating the electrical characteristics of the insulator of the cable to be connected when the pressure portion is used to heat and pressurize the connection portion. It was done.

That is, according to the present invention, as shown in FIG. 2, after forming a reinforcing insulating layer of rubber or plastic on the outer circumference of the cable conductor connecting portion, a heater is attached to the outer circumference of the reinforcing insulating layer, and a pressure is applied to the outside. An intermediate connecting portion of a rubber / plastic insulated cable by enclosing and mounting the container 2 for heating and pressurization, or encapsulating and mounting and heating and pressurizing the pressurizing container 2 having a heater on the outside of the reinforcing insulating layer. In the method of molding the pressure container 2 of the pressure container 2 described above, an insulating space 4 is interposed between the end portion of the pressure container 2 and the surfaces 3 and 3 ′ of the cables located at the end portion of the pressure container 2. It is characterized by heating and pressurizing while adjusting the temperature of the cable surfaces 3, 3 ′ located at the ends to 130 ° C. or less.

In the method of the present invention, the cable surface 3 at the end of the pressure vessel 2
The reason for limiting the temperature to 130 ° C or lower is that the insulator layer does not foam even when heated to 130 ° C without pressure, but when it exceeds 130 ° C, it foams and the electrical characteristics of the cable remarkably increase. This is because it will decrease.

A specific example of the method of maintaining the temperature below 130 ° C. is as follows.

(1) When a metal container is used as the pressurizing container 2, for example, a rubber is used as the heat insulating spacer 4 between the end of the pressurizing container 2 and the cable surfaces 3 and 3 ′ located at the end of the pressurizing container 2. , An organic heat insulating material such as plastic, an inorganic heat insulating material such as glass fiber, or an organic-inorganic composite heat insulating material is interposed.

Next, examples of the present invention will be described.

Example (1) Pencil-shaped shaving each of the two ends of the 600 mm ² , 154 kV CV cables A and B to expose the conductors, and the exposed conductors were connected to each other with a compression sleeve. An internal semiconductive layer was formed on the part using a semiconductive shrinkable tube. After that, on the internal semiconductive layer that was formed, Nippon Unicar HFDJ
Polyethylene tape based on 4201 (thickness 0.2 mm,
A width of 20 mm) was wound, a reinforcing insulating layer having a thickness of 25 mm was formed, and an outer semiconductive layer was formed on the outer side thereof using a semiconductive shrinkable tube.

Then, a metal pressure container with a cartridge heater embedded on the outer semiconductive layer is attached with an FPR rubber packing interposed between the outer semiconductive layer and the end of the metal container. It was electrically heated under a nitrogen gas pressure of / cm ² . At this time, the external semiconducting layer should be adjusted to 210 ℃.
The polyethylene tape winding insulation layer was melted and integrated by heating for 0 hour and cross-linked to form a cable connection part. In this case, the temperature on the outer semiconductive layer at the end of the metal container was 100 ° C.

When the AC breakdown voltage was measured for the cable connection portion molded according to this Example (1), it was not broken at 600 kV AC.

Example (2) A pressure vessel made of a silicon nitride sintered body, in which a cartridge heater is embedded on an outer semiconductive layer of a cable intermediate connecting portion formed in the same manner as in Example (1), is provided with the outer semiconductive layer and silicon nitride. Cover with the FPR rubber packing between the end of the sintered body and the end of the container, and press under nitrogen gas of 5 kg / cm ² for 10 hours so that the outer semiconductive layer becomes 210 ° C. The polyethylene tape winding insulation layer was melted and integrated by heating with electric current and crosslinked to form a cable connection part. In this case, a rubberized cloth tape was wound around the cable located at the end of the pressure vessel to insulate the pressure vessel and the cable from each other. As a result, the temperature of the cable surface was 130 ° C.

When the AC breakdown voltage was measured for the cable connection portion molded according to this Example (2), no breakdown occurred at 600 kV AC.

Comparative Example (1) A metal pressure container in which a cartridge heater is embedded is covered on the outer semiconductive layer of a cable intermediate connecting portion formed in the same manner as in Example (1) without interposing a heat insulating spacer or the like. After mounting, the cable connection part was formed by electrically heating under external pressure of 5 kg / cm ² of nitrogen gas for 10 hours so that the outer semiconductive layer was 210 ° C. In this case, since the metal container end is in direct contact with the outer semiconductive layer of the cable,
The surface temperature of the cable located at the end of the container was 140 ° C.

Regarding the cable connection portion molded by Comparative Example (1),
When the AC breakdown voltage was measured, a breakdown occurred near the connection at AC 420 kV.

As described in detail above, according to the method of the present invention, a cable connecting portion having good electrical characteristics can be molded, and its practical value is extremely useful.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a molding method of a conventional intermediate connecting portion of a rubber / plastic insulated cable, and FIG. 2 is a schematic explanatory view showing a molding method of an intermediate connecting portion of a rubber / plastic insulating cable of the present invention. . 1 ... Connection part, 2 ... Pressurized container, 3, 3 '... Cable surface, 4 ... Insulating spacer.

Claims (1)

[Claims] 1. A rubber or plastic reinforced insulating layer is formed on the outer periphery of a cable conductor connecting portion, a heater is attached to the outer periphery of the reinforced insulating layer, and a pressure container is attached to the outer side of the heater. In the method of molding the intermediate connection part of the rubber or plastic insulated cable by heating and pressurizing by heating, or by encapsulating and mounting a pressurizing container equipped with a heater on the outside of the reinforcing insulating layer, The temperature of the cable surface located at the end of the pressure vessel is set to 130 ° C. by interposing a heat insulating space between the end of the container and the surface of the cable located at the end of the pressure vessel.
Rubber characterized by heating and pressurizing while adjusting to the following,
Molding method for intermediate connection of plastic insulated cable.