JPH09288917A - Plastic power cable - Google Patents

Abstract

[PROBLEMS] To provide a plastic power cable having a wire shield structure in which eddy current loss is always small and a ground fault current flows uniformly in a shield layer. SOLUTION: In a plastic power cable having a wire shield layer on the outside of an insulating core of the cable, the wire shield layer is a plastic in which insulating wires and non-insulating wires are alternately arranged and closely wound in contact with each other. Power cable.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a plastic power cable such as a CV cable, and more particularly to a wire shield structure.

[0002]

2. Description of the Related Art There are two types of metal shields for plastic power cables such as CV cables: a wire shield system and an aluminum sheath system. FIG. 3 is a cross-sectional view of an example of a wire shield type plastic power cable. A non-insulating element wire 11A such as annealed copper wire or tinned annealed copper wire is provided on an insulating core 10 of a cable in which an inner semiconductive layer 2, an insulating layer 3 such as crosslinked polyethylene and an outer semiconductive layer 4 are sequentially provided on a cable conductor 1. The wire shield layer 11 is provided by winding a large number of the wires in parallel with each other at intervals. On the outside of the wire shield layer 11, a lead laminated tape or a stainless sheath 12 is provided as a water blocking layer, and a corrosion protection layer 13 such as polyethylene or vinyl chloride is provided thereon.
Or by directly applying the anticorrosion layer 13 on the wire shield layer 11.

FIG. 4 is a cross-sectional view of an example of an aluminum sheath type plastic power cable. Insulating core 1 mentioned above
0 on the corrugated aluminum sheath 1 through the cushion layer 14
5 is provided with a shield layer, and an anticorrosion layer 13 made of polyethylene, vinyl chloride or the like is provided on the shield layer.

[0004]

In the above-described conventional wire-shield type plastic power cable, since the non-insulating wires constituting the shield layer are arranged at intervals, there is no eddy current loss and the transmission capacity is large. Has the advantage of being large. On the other hand, it becomes difficult for the ground fault current to evenly flow through the shield wire, and the ratio of the ground fault current flowing to the ground increases, which causes problems such as induction to the communication line.

On the other hand, in the aluminum sheath type plastic power cable, the ground fault current easily flows through the aluminum sheath, and since the aluminum sheath has a cylindrical shape, the shielding coefficient is large, which is preferable as a countermeasure for induction. On the other hand, there is a problem that the transmission capacity is suppressed because the eddy current is generated.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a plastic power cable having a wire shield structure which has the advantages of both the conventional wire shield system and aluminum sheath system. The characteristic of the wire shield layer is that the insulating layer and the non-insulating layer are alternately arranged in the wire shield layer, and they are closely wound in contact with each other.

[0007]

1 is an explanatory view of a concrete example of a wire shield structure for a plastic power cable of the present invention, FIG. 1 (a) is a horizontal sectional view, and FIG. 1 (b) is a vertical sectional view. A wire shield layer 11 is provided on an insulating core 10 formed by sequentially providing an inner semiconductive layer, an insulating layer such as cross-linked polyethylene, and an outer semiconductive layer on a conductor. The wire shield layer 10 comprises non-insulating element wires 11A such as annealed copper wires and tin-plated annealed copper wires, and insulating element wires 11B having an oxide film, an enamel coating or the like on the annealed copper wires, which are alternately arranged. They are in close contact with each other and are tightly wound by spiral winding, SZ winding or the like.

In the wire shield layer having the above structure, a normal charging current flows through the non-insulating wire 11A, so that there is no eddy current loss and the transmission capacity is not suppressed. On the other hand, since the wires 11A and 11B forming the shield layer 11 are in close contact with each other and closely wound, the ground fault current easily flows through the wire at the ground fault point. In this case, insulated wire 1
1B is more expensive than the non-insulated wire 11A,
To reduce the number of insulated wires 11B, non-insulated wires 11
A plurality of A's may be continuously arranged, and the number of A's is determined by the line design conditions.

FIG. 2 is a side view of another embodiment of the wire shield structure for a plastic power cable of the present invention. As is clear from the drawing, the non-insulating wires 11A and the insulating wires 11B forming the wire shield layer 11 are alternately arranged, and these wires 11A and 11B are closely wound in contact with each other as shown in FIG. And the same as the case. In the case of this specific example, the insulating coating of the insulating wire 11B is removed 11C in the length direction, and the non-insulating wire 11A is removed at this portion.
And the conductor in the insulating wire 11B are in contact with each other. For this reason, since the electric current is transferred at the contact point, the electric current easily flows uniformly in all the wires. In this case, the eddy current is very small because the contact points are very small. The frequency of removing the insulating coating is arbitrarily determined by the line design conditions.

[0010]

As described above, according to the wire shield structure of the plastic power cable of the present invention, the eddy current loss is always small, the transmission capacity is large, and the ground layer is evenly grounded when the ground fault current occurs. A short circuit current flows, and the problem of induction to a nearby communication line can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view of a specific example of a wire shield structure of a plastic power cable of the present invention, FIG. 1 (a) is a horizontal sectional view, and FIG. 1 (b) is a vertical sectional view.

FIG. 2 is a side view of another embodiment of the wire shield structure for the plastic power cable of the present invention.

FIG. 3 is a cross-sectional view of an example of a conventional wire shield type plastic power cable.

FIG. 4 is a cross-sectional view of an example of a conventional aluminum sheath type plastic power cable.

[Explanation of symbols]

 10 Insulating Core 11 Wire Shield Layer 11A Non-insulating Element Wire 11B Insulating Element Wire 11C Coating Removal Part 12 Corrugated Stainless Sheath 13 Anticorrosion Layer 14 Cushion Layer 15 Corrugated Aluminum Sheath

Claims (2)

[Claims] 1. A plastic power cable having a wire shield layer on the outer side of an insulating core of the cable, wherein the wire shield layer has alternating insulated wire and non-insulated wire, and is closely wound in contact with each other. A plastic power cable characterized by the following. 2. The plastic power cable according to claim 1, wherein the insulating coating of the insulating wire is partially removed in the lengthwise direction.