JP2005251457A - Power cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a disadvantage of a power cable having an internal semiconducting layer, a cross-linked polyethylene layer, an external semiconducting layer, a cushion layer, a wire shield, a metal cover, and a corrosion protection layer on the outer periphery of a cable conductor, that the cost is high because a metal tape having small extensibility is wound between the cushion layer and the wire shield in order to prevent the distortion caused by the heat generation of power transmission. <P>SOLUTION: The cheap power cable reduces the distortion caused by the tension of the wire shield by using a hollow stranded wire or a strand wire having cushion member in its hollow core as the wire shield 6, and does not use any new members. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power cable.

  In general, as shown in FIG. 3, the power cable has an inner semiconductive layer 2, a crosslinked polyethylene insulating layer 3, an outer semiconductive layer 4, a cushion layer 5, a wire shield 6, a metal sheath 7, and an anticorrosion layer 8 on the outer periphery of the cable conductor 1. It has a configuration with.

  The wire shield 6 is configured by winding a copper wire having a thickness of about 1 to 2 mm at a predetermined pitch. This wire shield 6 is provided for the return circuit of a short-circuit current of tens of thousands of amperes that is generated when the cross-linked polyethylene insulating layer 3 breaks down. By this, the short-circuit current is shunted outside the cable. Thus, it is possible to prevent an electric shock to a living body and a failure of communication devices. For this purpose, 80 to 100 wire shields 6 are usually used.

  By the way, it is known that the power cable having the above-described configuration will be twisted when heat is generated by power transmission (see Patent Document 1). That is, the power cable generates heat by power transmission, and when such heat generation occurs, the cross-linked polyethylene insulating layer 3 expands in the radial direction and the axial direction, and the wire shield 6 is also stretched along with this, causing this. Thus, the power cable is twisted. When the power cable is twisted, there is a problem that the connection portion or the terminal portion of the cable is damaged. Therefore, development of a power cable that prevents twisting is desired.

  Conventionally, in order to prevent twisting of the power cable, as described in Patent Document 1, a metal tape having a low spreadability is provided between the cushion layer and the wire shield (conductive metal element wire). The configuration is known.

JP-A-5-274924

  However, the power cable having the above-described configuration has a problem that it is expensive because it is a configuration in which a metal tape having a small extensibility is newly wound.

  The present invention has been made in view of the above problems, and provides a power cable that is inexpensive and that can prevent twisting. The configuration of the power cable includes a cable conductor, a crosslinked polyethylene insulator, a cushion layer, a wire shield, a metal sheath, and the like. In the power cable including the anticorrosion layer, the wire shield is a stranded wire having a hollow center or containing a cushion material.

  In addition, the wire shield has an alternate winding structure in which the wire shields are reversed in directions for each of a plurality of twist pitches.

  When a twisted wire with a hollow center or cushion material is used as the wire shield, even if the cross-linked polyethylene insulation layer expands in the radial direction due to heat generated by power transmission, the wire shield may be deformed along with this. it can. For this reason, the twist resulting from the tension | tensile_strength of a wire shield can be reduced. In addition, since a new metal tape or the like having a low spreadability is not used, an inexpensive power cable can be obtained.

  In addition, by forming the wire shield in an alternating winding structure that is reversed for each of a plurality of twist pitches, the twist can be offset along the longitudinal direction of the power cable, and a power cable that is not easily twisted can be obtained.

Hereinafter, an embodiment of a power cable according to the present invention will be described in detail with reference to FIGS.
As shown in FIG. 3, the basic configuration of the power cable according to the present invention includes an inner semiconductive layer 2, a crosslinked polyethylene insulating layer 3, an outer semiconductive layer 4, a cushion layer 5, and a wire shield 6 on the outer periphery of the cable conductor 1. The metal sheath 7 and the anticorrosion layer 8 are provided.
As shown in FIG. 1, the feature of the present invention is that the wire shield 6 is a twisted wire having a hollow center. As the strand 61 constituting the stranded wire, for example, a copper wire having a thickness of 0.6 mm is used, and the 6 strands 61 are twisted so that the center is hollow.

  Thus, when the wire shield 6 is a stranded wire having a hollow center, the wire shield can be deformed together with the cross-linked polyethylene insulating layer expanding in the radial direction or the like. For this reason, it becomes possible to reduce the twist resulting from the tension | tensile_strength of a wire shield.

  FIG. 2 shows another embodiment of the wire shield 6 used in the present invention. The wire shield 6 is a stranded wire in which a cushion material 62 is inserted at the center. As the cushion material 61, a material that is easily stretched and has a cushioning effect in the radial direction, for example, a twisted polypropylene fiber is used. As the strand 61 constituting the stranded wire, for example, a copper wire having a thickness of 0.6 mm is used, and the six strands 61 are twisted around the outer periphery of the cushion material 62 as in the above embodiment. It is composed.

  In this way, when a stranded wire with the cushion material 61 in the center is used as the wire shield 6, the wire shield can be deformed together as the crosslinked polyethylene insulating layer expands in the radial direction or the like. For this reason, it becomes possible to reduce the twist resulting from the tension | tensile_strength of a wire shield. The material of the cushion material 61 placed in the center is not particularly limited as long as it is easily stretchable and has a cushioning effect in the radial direction.

  As described above, the wire shield composed of a stranded wire having a hollow center or containing a cushion material has a predetermined pitch on the outer periphery of the plurality of cushion layers 5, for example, a pitch of about 3 to 4 times the outer diameter of the cushion layer 5. It is used by wrapping.

  The wire shield 6 is usually wound spirally in one direction at a predetermined pitch. For example, a so-called alternating winding structure in which the twisting direction is changed every several tens of pitches may be used. Such an alternating winding structure has an advantage that twists can be offset along the longitudinal direction of the power cable and a power cable that is hard to twist can be obtained.

Sectional drawing which shows one Embodiment of the wire shield used by this invention. Sectional drawing which shows other embodiment of the wire shield used by this invention. Explanatory drawing of a power cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cable conductor 2 Internal semiconductive layer 3 Crosslinked polyethylene insulating layer 4 External semiconductive layer 5 Cushion layer 6 Wire shield 7 Metal coating 8 Corrosion protection layer 61 Wire 62 Cushion material

Claims (2)

In a power cable comprising a cable conductor, a cross-linked polyethylene insulator, a cushion layer, a wire shield, a metal sheath, and an anticorrosion layer, the wire shield is characterized by using a stranded wire having a hollow center or containing a cushion material. Power cable. 2. The power cable according to claim 1, wherein the wire shield has an alternating winding structure in which the wire shields are reversely arranged for each of a plurality of twist pitches.

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