JPH03167773A - Manufacture of extrusion molded joint for cv cable - Google Patents

Abstract

PURPOSE:To stabilize electric insulating performance by carrying out preheating at a certain specified temp. with a heater for an extrusion die, filling a space between a cable junction and the extrusion die and also the inside of an extruding device with a gas having a large degree of dissolution to polyethylene, and performing the extrusive molding upon attaining the specified temp. CONSTITUTION:The ends of bridged polyethylene (CV) cable 1, 1' are stripped in steps, butted, and connected to each other by a joint tube. An internally semiconductive layer 8 is formed, on its periphery and a cylindrical extrusion die 4 is put over the periphery of this junction part. A space between the junction of CV cables 1, 1' and the extrusion die 4 is filled with a gas 7 having a large degree of dissolution, and polyethylene with bridging agent is extruded into the space via a resin supply pipe 9 when the specified temp. is attained by feeding current to a heater 3 for heating the extrusion die 4. This process can enhance the electric characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a joint of a cross-linked polyethylene cable (hereinafter referred to as CV cable), particularly an extrusion mold joint.

[Prior Art] Conventionally, for the connection parts of CV cables that use polyethylene as an insulator, a polyethylene tape wrapping molding method containing a crosslinking agent has been applied to 154kV lines, and an extrusion molding method has been applied to 275kV lines. There is. This extrusion mold type connection is suitable as a connection to a 275 kV high-pressure tin path because it is molded by extruding molten polyethylene using an extrusion device on site.

The extrusion mold type connection part is manufactured by extruding polyethylene containing a crosslinking agent, cooling it, molding the extruded insulator, providing an external semiconductive layer, and crosslinking it. As a crosslinking agent, DCP (D: CumylPeroxy
de) is used, but this D C P''i crosslinking reaction generates decomposition products (acetophenone, cumyl alcohol, α-methylstyrene, methane). In particular, methane CCH. ) is considered to be the cause of the generation of poids in the polyethylene insulation as residues. Therefore, in order to improve the electrical performance and long-term reliability of extrusion mold type joints, it is necessary to suppress the generation of voids as much as possible, so a manufacturing method that suppresses the generation of voids has been considered important.

[Problems to be Solved by the Invention] Therefore, in a molded joint for a CV cable, it is important to suppress the generation of voids in the insulator during crosslinking by using DCP as a crosslinking agent. In particular, the extrusion mold joint is made of high pressure C of 275kV.
Since it is applied to a connection part for a V cable, it is necessary to prevent polar capoids from occurring in the insulator in order to stabilize the insulation performance.

The present invention has been made in view of these points, and an object of the present invention is to provide a novel method for manufacturing an extrusion mold joint for a CV cable.

? Means for Solving the Problems 1 In the present invention, in an extrusion mold connection part in which polyethylene of the same material as the cable is molded using an extrusion device as a connection part of a CV cable that is made of cross-linked polyethylene and an insulator, After the connection part has been treated in a specified manner, an extrusion mold is attached, and the heater of this mold is used to preheat it to a specified temperature. At this time, the space between the cable connection part and the extrusion mold is Inside the extrusion device, carbon dioxide gas (CO■), which has a high solubility in polyethylene, is present.
Alternatively, a CV characterized in that it is produced by the following steps: (1) creating an atmosphere filled with methane-based hydrocarbons (at atmospheric pressure); and (1) extruding polyethylene using an extrusion device when the mold reaches a predetermined temperature. This is a manufacturing method for extrusion mold joints for cables. [Embodiments] Hereinafter, embodiments of this invention will be described with reference to the drawings. figure;
It is a sectional view of an apparatus to which the method of manufacturing an extrusion mold joint for CV cables of the present invention is applied. That is,
The ends of the CV cables 1, 1' are stripped, and their cable conductors 1a, la' are butted and connected by a connecting tube. Then, an internal semiconducting layer 8 is formed on this outer surface. Next, a cylindrical extrusion mold 4 is placed over the outer periphery of the connection portion thus formed. A heating heater 3 is attached to this extrusion die 4, and seal portions 2 are provided at both ends of the extrusion die 4. A large gas supply device 5 is connected by a pipe 5a and opens into the mold 4. A space exists between the connection portions of the CV cables 1 and 1' and the extrusion mold 4. Fill 7.

This polyethylene; on the other hand, as gas 7 with a large dissolved amount: carbon dioxide gas (carbon dioxide, Co2) ethane 1: c
2I16. :, condolence, old, -93'(:'l, Flovan fc 3 Hq,': 夷, na, l'C
'I + S F r, ・“
-50 8℃).

In addition, solubility (solubility) is the amount of volume (in a saturated solution) when one volume of liquid coexists with a volume and is in equilibrium.

The solubility of a gas is determined by the partial pressure of the gas being latm (760 Tor
It is often expressed as a value converted to latm, which is the maximum volume of gas that can dissolve in a liquid of lcm3 when The solubility of a gas at temperature is proportional to its partial pressure.

Table 1 shows the solubility coefficients of gases in polyethylene.

Next, after energizing the heater 3 of the extrusion mold 4 to reach a predetermined temperature, the motor of the extrusion device 6 is driven to rotate the screw 10, and the polyethylene connected to the mold 4 is removed from the hopper 11. Polyethylene containing a crosslinking agent is extruded and filled through an extrusion resin supply pipe 9. At this time, a gas supply device 12 is connected to the extrusion device 6 to supply a gas that dissolves in a large amount in polyethylene, so that the gas is mixed into the polyethylene to be extruded. After filling with polyethylene, it is cooled and solidified. The extrusion molded joint for a CV cable thus formed is attached with an external semiconductor layer, covered with the crosslinking mold 4 again, and subjected to crosslinking heating.

The gas 7 having a large dissolved amount is suitably in an atmosphere at about atmospheric pressure.

When polyethylene is extruded into a gas atmosphere with a large amount of dissolution, the amount of dissolution will be large at the interface between the extruded polyethylene and the CV cables 1, 1', or if voids occur in the extruded polyethylene. It will be filled with gas 7. During the extrusion or crosslinking process, the voids in the insulator are filled with a large amount of dissolved gas, which dissolves into the insulator and the voids disappear. This makes it possible to produce extrusion molded joints with superior electrical performance.

[Effects of the Invention] As explained above, according to the method of manufacturing an extrusion mold joint for CV cables of the present invention, ■ Since the extrusion mold joint extrudes polyethylene using an extrusion device, the level of foreign matter is low and the electrical performance is improved. It is also very reliable from both sides.

■Since polyethylene is extruded into a gas atmosphere with a large amount of dissolved polyethylene, when manufactured as a joint, voids in the insulator can be significantly reduced and electrical properties can be improved.

■Since the current manufacturing technology for extrusion mold joints can be applied as is, no special construction methods are required, and the workability and handling are excellent.

Excellent actions and effects such as these can be obtained.

[Brief explanation of the drawing]

The figure is a sectional view of an extrusion device for explaining the method of manufacturing an extrusion mold joint for a CV cable according to the present invention. 1 l 1 1'...CV cable 2...mold seal part 3...heater 4...
・Extrusion mold 5... Gas supply device 6... Extrusion device 7... Gas with a large dissolved amount 8... Internal semiconductive layer 9... Extruded resin supply pipe O... Screw 11...・Hopper 2...Gas supply device

Claims (1)

[Claims] (1) For the connection part of a CV cable that uses cross-linked polyethylene as an insulator, in an extrusion mold connection part in which polyethylene, which is the same material as the cable, is molded using an extrusion device, (a) The cable connection part is subjected to specified treatment. (b) At this time, the space between the cable connection part and the extrusion mold and the inside of the extrusion device are filled with polyethylene. (c) When the mold reaches a predetermined temperature, extrusion molding of polyethylene is performed using an extrusion device. A method for manufacturing an extrusion mold joint for a CV cable, characterized in that: