JPS5933127Y2 - Cross-linked polyethylene power cable - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a cross-linked polyethylene electrical cable.

The inner shielding layer of a cross-linked polyethylene cable, i.e. the shielding layer on the inner conductor, consists of a semi-conductive rubberized cloth tape wound over the inner conductor, and a wrapped layer of semi-conductive rubber, plastic, usually semi-conductive The structure is extrusion coated with polyethylene.

On the other hand, the outer shielding layer of the same cable is an extrusion coating of semiconductive rubber or plastic, usually semiconductive polyethylene, on a crosslinked polyethylene insulation layer, and a semiconductive rubber coating is applied to the extruded semiconductive coating layer. It has a structure in which a cloth tape is wound, and a metal tape for an external conductor is wound on top of the wound layer.

In crosslinked polyethylene cables, the generation of gas as a crosslinking residue is unavoidable during crosslinking, and it is known that the gas is removed by heat treatment and vacuuming after the crosslinking process, but even with such treatment, It is undeniable that trace gases remain.

Therefore, during use of the cable, the residual gas may be liberated from the crosslinked polyethylene, and there is a strong possibility that gas will be generated from the crosslinked polyethylene insulating layer, even if it is in a small amount.

However, in the internal shielding layer and the external shielding layer of conventional cross-linked polyethylene cables, a conductive seat layer provided between the cable internal conductor or external conductor and the semiconductive internal extruded layer or external extruded layer is If a semi-conductive rubberized (or semi-conductive polyethylene-coated) cloth tape is used to attach a button, if gas is generated from the cross-linked polyethylene insulation layer during use of the cable, the release of this gas can be prevented by using the semi-conductive rubberized cloth tape. Under the above gas generation conditions, a gas layer will be formed between the semiconductive rubberized cloth tape and the semiconductive extruded layer, even if the amount generated is minute. become.

It is clear that such a gas layer has a negative effect on the cable properties and must be eliminated.

For this reason, it is conceivable to use a breathable conductive tape, such as a cloth tape containing conductive wires, for the above-mentioned conductive floor layer, but there is a significant difference in the coefficient of thermal expansion between the conductive wires (metal) and the plastic insulation layer. Due to cable heat cycling, abnormal thermal stress and strain occur at the contact interface between the conductive wire of the conductive floor layer and the semiconductive extruded layer.

However, the metal body of the conductive floor layer can become a propagation path for surges, and when a surge enters the cable, abnormal strain occurs at the interface between the conductive floor layer and the semiconductive extruded layer, as described above. If a portion occurs, dielectric breakdown is likely to occur from that portion.

The cross-linked polyethylene electrical cable according to the present invention has a structure devised in view of the above points, and has a metal plating between the cable inner conductor or outer conductor and the semiconductive inner extruded layer or outer extruded layer. It is characterized by having a plastic cloth layer applied to it.

The present invention will be explained below with reference to the drawings.

In the figure, 1 is an internal conductor made of a twisted wire conductor.

Reference numeral 2 denotes a metal-plated plastic cloth layer provided on the inner conductor 1, which may be provided in any of the following manners: horizontally, wound, or vertically.

3 is an internal semiconductive layer extrusion coated on the metal plated plastic cloth layer 2, and is usually made of semiconductive crosslinked polyethylene (the metal plated plastic cloth layer 2 is coated on the internal semiconductive layer 3). During extrusion coating, the coating material is prevented from entering the strand gaps of the stranded wire conductor 1 (same as the conventional method).

4 is a crosslinked polyethylene insulation layer, which is provided by extrusion coating.

Reference numeral 5 denotes an outer semiconductive layer extruded and coated on the crosslinked polyethylene insulating layer 4, and the material thereof is usually the same as that of the inner semiconductive layer 3.
is the same as

Reference numeral 6 denotes a metal-plated plastic cloth layer provided on the outer semiconductive layer 5, and may be provided by winding or vertically laying.

7 is a metal tape winding layer as an external conductor, and a twisted layer of metal wires can also be used (the external semiconductive layer 5 may be damaged by the metal plated plastic cloth layer 6 at the edges of the external conductor 7, etc.). The point of preventing this is the same as the conventional method.

) 8 is a cable sheath, which may be made of metal or plastic.

In addition to the above, the metal plated plastic cloth layer 2゜6 is
Since it is breathable, gas may be generated from the crosslinked polyethylene insulating layer 4, but the metal plated cloth layer 2.6 and the semiconductive layer 3,
It is possible that gas may accumulate between these layers, so the formation of a gas layer between these layers can be avoided.

The generated gas is then dissipated along the inner stranded conductor 1 and the outer conductor 7.

The above-mentioned metal-plated plastic cloth is plated with copper, aluminum, nickel, etc. by chemical plating, electroplating, vacuum deposition, metal spraying, ion plating, sputtering, etc. on acrylic, polyester, nylon, polypropylene woven fabric, non-woven fabric, etc. The plating thickness is usually 1 to 15 μm.

As mentioned above, the cross-linked polyethylene cable according to the present invention is provided with a conductive material between the cable conductor (inner conductor or outer conductor) and the semiconductive plastic extruded layer (inner extruded layer or outer extruded layer). A metal-plated plastic cloth layer is used for the seat floor layer, and the metal plating thickness of this cloth is extremely thin, on the μ order, and the thermal expansion coefficient of the metal-plated plastic cloth is the same as that of plastic. Therefore, despite the cable heat cycle, thermal stress distortion can be prevented from occurring at the contact interface between the semiconductive plastic extruded layer and the conductive seat layer, and therefore, the occurrence of thermal stress distortion due to the surge described above can be prevented. Can prevent dielectric breakdown.

However, the present invention can also be implemented in such a manner that a metal plated cloth layer is provided only on one side of the inner shielding layer or the outer shielding layer, as described above, and even in this case, compared to the conventional cable, the above-mentioned The benefits of securing Cape 4 can be fully expected.

[Brief explanation of the drawing]

The drawing is a longitudinal cross-sectional view showing a crosslinked polyethylene electrical cable according to the present invention. In the figure, 1 is an inner conductor, 2 is a metal-plated plastic cloth layer, 3 is a semi-conductive inner extruded layer, 4 is a cross-linked polyethylene insulation layer, 5 is a semi-conductive outer extruded layer, 6 is a metal-plated cloth layer, I is It is an outer conductor.

Claims (1)

[Scope of utility model registration request] A cross-linked polyethylene electrical cable, characterized in that a metal-plated plastic cloth layer is provided between a cable inner conductor or outer conductor and a semiconductive inner extruded layer or outer extruded layer.