JPH05292625A - Assembling method of prefabricated joint for plastic insulated cable - Google Patents

Abstract

PURPOSE:To provide an assembling method of prefab joint for plastic insulated cable in which no void is present at the interface between a premold insulator and a cable insulator and a stabilized insulation performance is realized. CONSTITUTION:In the assembling method of prefabricated joint for plastic insulated cable, a premold insulator 3 is inserted to a predetermined position on a cable insulator l and a die metal 4 is mounted on the outside of the premold insulator 3 which is then heated to a temperature in the range of 50-100 deg.C by means of a heater 5 from above the die 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling a prefabricated type connecting portion such as a CV cable (crosslinked polyethylene insulated power cable), particularly a premolded insulator.

[0002]

2. Description of the Related Art Assembling a prefabricated type connecting portion of a CV cable or the like is carried out by inserting a preformed premolded insulator over the end of the cable insulator. Since the diameter of the inner cylindrical portion of the premolded insulator is formed smaller than the outer diameter of the cable insulator, silicone oil or the like should be applied to the outer surface of the cable insulator and the inner peripheral surface of the premolded insulator during insertion. Lubricant was applied and inserted.

Since the above-mentioned conventional method for inserting a premolded insulator is carried out in the atmosphere, even if a sufficiently degassed silicone oil is applied, the inclusion of voids during the application of the silicone oil or the premolded insulation is performed. Due to the inclusion of voids during body insertion, these involved voids sometimes remained at the interface between the outer peripheral surface of the cable insulator and the inner surface of the premolded insulator. The 66-77 kV class pre-molded insulator has a relatively short interface length, and the trapped voids can be released by pressing with a spring from the rear when assembling the connection part,
Pre-molded insulators for 275kV class ultra-high voltage cables have long interfacial lengths, making it difficult for voids to escape sufficiently, and these voids have been a factor in reducing the insulation performance of the connection.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and a method of assembling a prefabricated connection portion for a plastic cable having stable insulation performance without voids at the interface between the premold insulation and the cable insulation. The first feature of the present invention is to insert a premolded insulator into a predetermined position on a cable insulator, mount a mold on the outside of the premolded insulator, and then insert the mold from above the mold. The heater is to heat the premolded insulator to 50 ° C or higher and 100 ° C or lower.

A second feature of the present invention is that the cable insulator is cooled and shrunk to −20 ° C. or less in advance, and then a premolded insulator at room temperature is inserted into the portion, and the temperature is maintained at room temperature.
I have to leave it for more than an hour.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing a vertical cross section of a main part of a concrete example of the first feature of the assembling method of the present invention. In the drawings, 1 is a cable insulator, 2 is a cable conductor, and 3 is a premolded insulator inserted in a predetermined position on the cable insulator 1. On the outside of the premolded insulator 3, a mold 4 having two cracks in the length direction is attached. The inner diameter of the mold 4 is D + 5 with respect to the maximum outer diameter D of the premold insulator 3.
It is preferably less than or equal to mm. Then, a heater 5 is arranged on the mold 4, and the temperature of the maximum outer diameter portion of the premolded insulator 3 is controlled within the range of 50 ° C. or higher and 100 ° C. or lower.

By heating the premolded insulator 3 from the outside in this way, the premolded insulator 3 and the cable insulator 1 expand radially in the mold 4, and the cable insulator 1 and the premolded insulator 3 are expanded. The interfacial pressure of
The voids existing at the interface can be released from both ends of the premolded insulator 3. At this time, by controlling the heater so that the temperature of the maximum outer diameter portion of the premolded insulator 3 is maximized and the temperature gradient is formed toward the tip portion, the interface pressure has a gradient, and the void escape Is effective in. In addition, the heating temperature by the heater is 50 ℃ or more, 1
The temperature below 00 ℃ means that the expansion of the pre-molded insulation and cable insulation is small at less than 50 ℃ and an effective interfacial pressure cannot be obtained. This is because no pressure can be obtained.

FIG. 2 is an explanatory view of a concrete example of the second feature of the assembling method of the present invention. In the drawings, the same symbols as those in FIG. 1 represent the same parts. The cable insulator 1 portion into which the premolded insulator 3 of the cable having the connection 6 of the cable conductor 1 inserted therein is housed in the cooling case 7 filled with the cooling medium 8 and cooled to -20 ° C or lower, The portion of the cable insulator 1 is cooled and accommodated, and the diameter of the premolded insulator 3 is kept smaller than the inner diameter thereof. Then, the premolded insulator 3 at room temperature is inserted on the cable insulator 1 that has been cooled and shrunk, and left at room temperature for 10 hours or more. By this leaving, the temperature of the cable insulator 1 part rises from -20 ° C to normal temperature,
Due to the expansion force of the cable insulator 1 accompanying this, an interfacial pressure is generated at the interface between the cable insulator 1 and the premolded insulator 3, and the voids existing at the interface are escaped so that the two adhere to each other.
The cooling temperature of the cable insulator 1 is set to −20 ° C. or lower in order to sufficiently shrink the cable insulator 1,
After inserting the pre-molded insulator 3 on the cable insulator 1, the pre-molded insulator 3 is left at room temperature for 10 hours or more so that the cooled cable insulator 1 is heated to room temperature and expanded until a sufficient interfacial pressure is obtained. is there.

[0009]

As described above, according to the method of assembling the prefabricated connection portion of the present invention, the cable insulator and the premold are heated by heating the premold insulator or cooling the cable insulator to normal temperature. A large interfacial pressure can be obtained at the interface of the insulator, voids existing at the interface can be released, and a prefabricated connection portion having void-free and stable insulation performance can be formed. Therefore, when it is used for forming a prefabricated connection portion such as an ultra-high voltage plastic cable having a long interface, its effect is great.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a vertical cross section of a main part of a specific example of the first feature of the method for assembling a prefabricated connection part of the present invention.

FIG. 2 is an explanatory diagram of a specific example of the second feature of the prefabricated connection portion of the present invention.

[Explanation of symbols]

 1 Cable Insulator 2 Cable Conductor 3 Pre-molded Insulator 4 Mold 5 Heater 6 Cable Conductor Connection 7 Cooling Case 8 Cooling Medium

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koji Kishi, 1-3-1, Shimaya, Konohana-ku, Osaka No. 3 Sumitomo Electric Industries, Ltd. Osaka Works

Claims (2)

[Claims] 1. A premold insulator is inserted into a predetermined position on a cable insulator, a mold is attached to the outside of the premold insulator, and the premold insulator is heated from above the mold by a heater. A method for assembling a prefabricated joint for a plastic cable, characterized by heating at 50 ° C or higher and 100 ° C or lower. 2. A plastic cable, characterized in that the cable insulator is cooled and shrunk to −20 ° C. or less in advance, and then a premolded insulator at room temperature is inserted into the part and left at room temperature for 10 hours or more. Assembly method of prefabricated connection.