JPH09224322A - Power cable joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the shrinkbacks of cable jackets by a method wherein shrinkback-proof members which have nails on their inside surfaces are applied to the jackets of power cables and the nails are made to bite into the jackets and a heat-shrinkable tube is applied over both the cable jackets across the cable joint part. SOLUTION: Two shrinkback-proof members 30 are applied to the respective end parts of the jackets 14 of left and right CV cables 10 with 180 degrees intervals respectively and their nails 34 are made to bite into the cable jackets 14. Then a heat-shrinkable tube 40 is applied over the shrinkback-proof members 30 on both the cables and made to shrink. The shrinkback-proof member 30 is made of heat-resistant hard plastic such as polyamide resin. Its main part is, for instance, a rectangular thin plate which is warped into a cylindrical arc surface so as to have a concave inside surface. For instance, two nails 34 are provided integrally on its inside surface. In such case, the nail 34 has a hook-shape which is slightly inclined forward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting portion (intermediate connecting portion and terminal connecting portion) of a power CV cable, and more particularly to a technique for preventing shrinkback of a cable sheath.

[0002]

2. Description of the Related Art FIG. 4 schematically shows an intermediate connecting portion of a CV cable. Reference numeral 10 is the entire cable, 12 is the cable core (a portion of the cable such as the cable conductor, the cable insulator, and the cable shielding layer excluding the sheath), and 14 is the cable sheath. Reference numeral 20 is the entire intermediate connection portion, and 22 is a tape winding protection layer.

When the cable sheath 14 causes a shrink back at such a connecting portion, the shielding copper tape generally used for a cable having a voltage of 33 kV or less will be collapsed or broken. Then, a minute discharge is generated at the broken portion, the insulator is thermally deteriorated, and finally a ground fault occurs.

In the case of a wire shield often used for a cable of 66 kV or more, the cable sheath 14 is restrained by folding back a copper wire for processing. However, in the case of a cable of 33 kV or less, there is no such effective method, and the following treatment is currently taken. Restraint by wrapping the adhesive and self-adhesive tape. Restraint due to surface pressure and adhesion of the heat shrink tube. Restraint by tightening the cleat and bracket that are the supports of the CV cable 10 itself.

There is also a method of deforming the cable sheath 14 itself (see Japanese Patent Application Laid-Open No. 59-222022). That is, as shown in FIG. 5, a projecting portion 140 is formed at the end of the cable sheath 14 and is pressed by the heat shrinkable tube 24.

[0006]

However, each of the above methods has the following problems. Tape treatment method The adhesive strength and shrinkage force of the tape vary depending on the temperature.
A shrink back is caused by a heat thunker due to the temperature difference during the day. Also, the winding of the tape itself may collapse. Heat-shrinkable tube has weak binding force. Since it is intended to support the cleat and bracket cable itself, the distance at the end may be large. At this time, the cable sheath 14 from the terminal end to the support portion causes a shrink back. Also,
Vibrations of the transformer and electric motor may loosen the bolts of the cleats and brackets, reducing the binding force. The method of forming the protruding portion 140 of the cable sheath 14 requires the operation of forming the protruding portion 140 (formed by heating and softening the end portion of the cable sheath 14 and pushing in the cable axial direction). A technique for softening only the cable sheath 14 without affecting the core 12 with heat is required.

[0007]

As illustrated in FIGS. 1 to 3, a shrinkback preventing material 30 having a claw 34 on its inner surface is used. The shrinkback prevention material 30 is mounted on the plastic sheath 14 of the power cable, and the claw 34 is made to bite into the sheath 14. From above the sheath 14 to which the prevention material 30 is attached,
A shrink layer of heat shrink tubing 40 is placed over the components of the cable connection that precede the ends of the sheath.

[About the shrink-back prevention material 30]
FIG. 3 shows an example of the shrinkback prevention material 30. In the same figure, (a) is a perspective view seen from the inner surface side, (b) is a plan view seen from the inner surface side and its side view, and (c) is a C sectional view of (b). The shrink-back preventing material 30 is made of heat-resistant hard plastic such as polyamide resin. The main body 32 is, for example, a rectangular thin plate, and is slightly curved in an arcuate cylindrical shape so that the inner surface 320 is concave. For example, two claws 34 are integrally provided on the inner surface 320. In this case, the claw 34 has a hook shape that is slightly inclined forward.

The inner surface 320 is curved so as to be in close contact with the cable sheath.

The claw 34 may have a structure projecting at a right angle from the inner surface, but if the claw 34 is formed into a hook shape inclined with respect to the axial direction, the effect can be more easily obtained.

The outer surface 322 becomes a contact surface with the heat shrinkable tube 40. Therefore, in order to increase the frictional resistance, this surface is roughened to have fine irregularities.

In the claims, "a component of the cable connecting portion existing before the end portion of the sheath 14 to which the preventive material 30 is attached" refers to, for example, FIG.
2 is the end of the sheath 14 of the CV cable 10 of the connected counterpart, etc.
In the case of the terminating connection part, it is the stress cone body 21 or the like.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

[In case of intermediate connection part (Fig. 1)] Left and right CV cables 10
The two shrinkback preventing materials 30 are attached to the ends of the respective cable sheaths 14 at intervals of 180 degrees, and the claws 34 bite into the cable sheaths 14. A heat shrink tube 40 is covered over the shrink-back preventing materials 30 of both cables to shrink them, thereby applying a pressure inward in the radial direction to each shrink-back preventing material 30, and between the both shrink-back preventing materials 30. Keep binding.

When the size of the cable changes and the restraint force of the shrink-back preventing material 30 becomes excessive or insufficient, the number is appropriately increased or decreased.

[In case of terminal connection portion (FIG. 2)] A shrinkback preventing material 30 is attached to the end portion of the cable sheath 14 and the claw 34 is bited. Then, the shrink-back preventing material 30 is covered with the heat-resist cone body 21, and the heat-shrinkable tube 40 is covered to shrink the heat-shrinkable tube 40. Note that 120
Is a cable insulator, 122 is a cable outer semiconductive layer, 4
2 is a bracket stopper.

[0016]

The restraint force of the cable sheath is increased, shrinkback can be prevented, and a cable ground fault can be prevented.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment example in which the present invention is applied to an intermediate connection portion.

FIG. 2 is an explanatory diagram of an example of an embodiment in which the present invention is applied to a terminal connecting portion.

FIG. 3 is an explanatory diagram of a shrinkback prevention material 30 of the present invention.

FIG. 4 is a general explanatory view of a CV cable intermediate connection portion.

FIG. 5 is an explanatory diagram of an example of a conventional technique.

[Explanation of symbols]

 10 CV cable 12 Cable core 14 Cable sheath 140 Projection 20 Intermediate connection 21 Stress cone body 22 Tape winding protective layer 24 Heat shrink tube 30 Shrink back prevention material 32 Body 320 Inner surface 322 Outer surface 34 Claw 40 Heat shrink tube 42 Bracket stop Metal fittings

Claims (1)

[Claims] 1. A shrinkback preventing material having a claw on its inner surface is mounted on a plastic sheath of a power cable in a state in which the claw is bite into the sheath,
A feature that a contraction layer of a heat-shrinkable tube is covered over the sheath on which the preventive material is mounted, to the components of the cable connecting portion existing before the end of the sheath, Power cable connection.