JP2864184B2 - Surface finishing method of cable insulation at the connection end of cross-linked polyethylene insulated cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection using a pre-molded insulator such as a stress cone in connection work of an intermediate connection portion and a terminal connection portion of a power cable, especially a crosslinked polyethylene cable (CV cable). The present invention relates to a surface finish for smoothing the surface of a cable insulator by eliminating the roughness thereof in order to mount a pre-molded insulator on an insulator interface of a cable when a so-called prefab joint method is adopted.

[0002]

2. Description of the Related Art Conventionally, as a method of connecting an insulated cable such as a CV cable, as shown in FIG. 6, uncrosslinked polyethylene insulating tapes 34 and 34 ' containing a crosslinking agent are wound on a conductor 1 to be connected. After turning, a method of cross-linking by heating with a heater 33, as shown in FIG. 7, a junction of the conductor 1 is surrounded by a mold 36, and an insulating material such as polyethylene 35 containing a cross-linking agent is filled in the mold. Injection, heating by the heater 37, pressurization by compressed air, and fusion bonding with the cable, as shown in FIGS.
A pre-mold connection method (a prefab joint method) in which a pre-molded insulator 31 formed in advance is mounted on an insulator 3 at a connection end of a cable and assembled.

[0003]

The insulation tape winding method using a polyethylene tape is simple in operation, but has a small withstand voltage limit and is not suitable for high-voltage cables.
Although the mold connection method using a polyethylene resin containing a crosslinking agent has high reliability, it requires skilled and advanced construction techniques and requires a long time for construction. Therefore, it was considered as an alternative to this, a premolded connection method using Puremo Le de insulator previously formed. To assemble a junction box using this method, remove the outer semiconductive layer at the connection end of the cable and then clean the surface of the cable insulator to install the pre-molded insulator on the cable insulator. After that, it is necessary to perform a surface finishing operation such as applying silicone oil to the surface. And the surface finish of the cable insulator that has been done conventionally, after shaving off the outer semiconductive layer of the cable using a special tool or glass piece, polishing the cable insulator surface with sandpaper or emery cloth etc. Because of the finishing, it was possible to crush the cross-linked polyethylene or the like as an insulator, causing an electrical weak point against a high voltage.

[0004]

Means for Solving the Problems It is considered that dielectric breakdown at the time of high voltage transmission in a CV cable is caused by concentration of an electric field caused by voids and foreign substances existing in the insulator, protrusions on the insulator surface, and the like. ing. However, with conventional surface finishing using sandpaper or emery cloth, no matter how large the number (600-1000), even if the surface of the insulator is viewed with a microscope, the shape of the fins becomes fine. However, there is still a scratch and a groove left, and the shavings of the semiconductive layer of the cable may get into this groove, so the pre-mold insulator is mounted on such a state In the pre-mold connection method, when finishing the surface of the semiconductive layer or insulator of the cable, make sure that these surfaces are free of foreign matter and smooth. is important. And, as a means of smoothing the surface, there is a method of removing the swelling by a torch lamp or a method of pressing and melting the swelling by heating using a mold, but the method using a torch lamp involves danger, the use of fire in the manhole is not realistic to have been prohibited, although the melting pressing method is safe for using a mold,
Extensive equipment is required. Accordingly, the present invention provides a method of insulating a cross-linked polyethylene layer or the like by shaving a cable external semiconductive layer with a special tool, fitting a heat-shrinkable tube made of a fluororesin, and pressing and heating the tube. The surface of the body is finished smoothly.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention of the present application will be described based on an embodiment with reference to the drawings (FIGS. 1 to 5). As shown in FIG. 1, after removing the external semiconductive layer 4 provided on the insulator 3 of cross-linked polyethylene or the like by a predetermined length using a special stripping tool, the connection end of the CV cable is stepped, and then cleaned. A transparent heat-shrinkable tube 13 made of tetrafluoroethylene resin (registered trademark: tetrafluoroethylene resin manufactured by DuPont) is fitted over the insulator 3 and the semiconductive layer 4, which are shown in FIG. 2. As described above, the heating is performed after being set in the pressing mold 14. That is,
4 is placed in a cylindrical pressure mold 14 containing a heater 15 therein.
Along with fixing 3 parts of the cable insulator fitted with the heat-shrinkable tube 13 made of fluorinated ethylene resin and 4 parts of the semiconductive layer,
After setting both ends 16a of the heat-shrinkable silicone tube 16 for sealing the pressurized mold with the mold sealing piece 14a and surrounding the insulator 3 and the semiconductive layer 4,
When the heater 15 is energized and heated, and when the tetrafluoroethylene resin tube 13 and the silicone tube 16 are heated, pressurized air is supplied from the compressed air supply port 17 to pressurize the heat-shrinkable 4-foot tube. The ethylene fluoride resin tube and the silicone tube shrink, and the insulator 3 and the semiconductive layer 4 of the cable are tightened. Then, the insulator and the semiconductive layer are also heated and softened,
Irregularities such as burrs on the insulator portion 8 caused by a peeling tool or sandpaper are tightened by the shrinkage force of the heat-shrinkable tube, deformed, integrated and smoothed.
As shaping conditions at this time, the heating temperature is 100 to 200.
C. and a pressure are preferably about ² to 10 kg / cm ² .

[0006] Next, removal of the mold 14 from the removal of the compressed air, after the cable insulation portion is cooled, eliminate and or excised polytetrafluoroethylene tube and the silicone tubing, the insulator surface After cleaning and applying silicone oil to the surface, the pre-molded insulator 3
If 1, the cable connection end can be connected and assembled in the same manner as in the prior art. In addition, if the method of the present invention is adopted as a method as shown in FIG. 3, the surface of the insulator can be made smooth without using a pressing mold. That is, after cleaning the part of the insulator 3 and the semiconductive layer 4 at the end of the cable connection, the heat-shrinkable tetrafluoroethylene resin tube 13 is fitted to the part, winding a tetrafluoroethylene resin tape 24 of the heat-shrinkable, further securing the upper or the al heat shrinkable polyester tape 25 wound tetrafluoroethylene resin tube on the. Next, a heater 26 for heating the insulator, the heat-shrinkable tube, and the like is provided along these layers, and a heat insulating tape is wound therefrom and fixed.

In this manner, when the heater 26 is energized and heated, the heat-shrinkable tube 13, the tape 24,
25 is heated and contracted, and the insulator 3 and the semiconductive layer portion 4 are also heated and softened, so that the projections and burrs 8 formed on these portions are deformed by the contraction pressure of the heat-shrinkable layer. , And become smooth. Then, after the cable insulator is cooled, the heat insulating tape 27, the heater 26, the heat shrink layers 13, 24, 25, etc. are removed, and then the insulator surface is cleaned and silicone oil is applied. Since the pre-mold insulator 31 can be mounted, the assembling work of the connection box can be performed as before. The smoothness of the surface of the cable insulator obtained in this manner had the same effect as that obtained by smoothing using a pressing mold.

[0008]

According to the present invention, the insulator at the cable connection end is heated and pressed through a seamless heat-shrinkable tetrafluoroethylene resin tube to finish the surface, so that the surface of the insulator does not have irregularities. In addition, the smoothness is improved, and the electrical insulation performance at the interface between the pre-mold insulator and the cable insulator is improved. In this case, when using a heating mold, the present invention
In this case, the heat shrinkable silicone tube is used
Tighten cable insulation by using force
Therefore, simply use only the tetrafluoroethylene resin tube
Cable insulation easily due to superior compression force
To achieve its surface smoothing.
When a heating mold is not used, a heat shrinkable 4
Heat-shrinkable ethylene tetrafluoride in addition to fluorinated ethylene resin tubes
Winding layer of resin tape and heat shrinkable polyester tape
The combined use of the layer and the
Cable by excellent compressive force than those who were use cube only
Tightening the bull insulator to achieve its surface smoothing
Can be. In addition, since a transparent heat-shrinkable tetrafluoroethylene resin tube is used, it is easy to determine whether there is any foreign matter on the surface of the insulator before heating, and if foreign matter is found, the foreign matter is removed. Remove and then use another resin
Since heat shrinkage can be performed by applying a wire or tape , foreign matter can be prevented from being caught in the insulator, and a decrease in the electrical insulation characteristics of the cable can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a step peeling structure of a CV cable connection end.

FIG. 2 is a partial sectional view of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view (b) a partial cross-sectional view of a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view in which a pre-molded insulator is attached to a cable connection end.

FIG. 5 is a longitudinal sectional view of a prefabricated joint using a pre-molded insulator.

FIG. 6 is an explanatory view of a conventional insulating tape winding connection method.

FIG. 7 is an explanatory view of a conventional mold connection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable conductor 2 Inner semiconductive layer 3 Cable insulator (crosslinked polyethylene layer) 4 Outer semiconductive layer 7 Vinyl sheath 8 Scissors 13 4 Fluoroethylene resin tube 14 Press mold 14 a Mold sealing piece 15 Heater 16 Silicone tube 24 Polytetrafluoroethylene resin tape 25 Polyester tape 26 Heater 27 Heat insulation tape 31 Pre-mold insulator

──────────────────────────────────────────────────続 き Continuing on the front page (72) The inventor, Manabu Yoshida, 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) The inventor, Ishifumi Seki, 1-5-1, Kiba, Koto-ku, Tokyo Fujikura (56) References JP-A-57-34710 (JP, A) JP-A-2-266812 (JP, A) JP-A 64-61225 (JP, A) JP-A-50-55894 (JP, A) , A) Jpn. Sho 62-188930 (JP, U) JP-B 53-38182 (JP, B2) JP-B 58-9530 (JP, B2) (58) Fields surveyed (Int. Cl. ⁶ , DB Name) H02G 1/14 H02G 15/00-15/196

Claims (4)

(57) [Claims] 1. A surface of a cable insulator in which a connection end portion of a crosslinked polyethylene insulated cable is stripped in a predetermined shape, and a heat-shrinkable tetrafluoroethylene resin tube is fitted on the insulator portion. Is placed in a pressurized mold having a built-in heater, and the heat-shrinkable silicone tube for sealing the pressurized mold is surrounded around the periphery of the pressurized tetrafluoroethylene resin tube. A method for finishing a surface of a cable insulator, wherein the surface of the cable insulator is smoothed by pressing the cable insulator with the silicone tube and the tetrafluoroethylene resin tube. 2. A surface of a cable insulator in which a connection end of a cross-linked polyethylene insulated cable is stripped in a predetermined shape is cleaned, and a heat-shrinkable tetrafluoroethylene resin tube is fitted on the insulator portion. Wrap the heat-shrinkable tetrafluoroethylene resin tape over the tetrafluoroethylene resin tube,
This is wound with a heat-shrinkable polyester tape, and a heater for heating is wound thereon with a tape for keeping heat, and after fixing, the cable insulator is heated by the heater,
A method for finishing a surface of a cable insulator, wherein the surface of the cable insulator is smoothed by softening and tightening the cable insulator against shrinkage force of the heat-shrinkable tetrafluoroethylene resin tube and tape. 3. The heat-shrinkable tetrafluoroethylene resin tube is transparent or translucent.
3. The surface finishing method for a cable insulator according to any one of items 1 to 2 . 4. A surface finishing method of the cable insulation according to claim 1, characterized in that pressurizing the heat-shrinkable silicone tube and polytetrafluoroethylene tube by pressurized fluid.