JPS5821763B2 - Rubber/plastic insulated power cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in rubber-plastic insulated cables, particularly for high current applications.

In general, rubber/plastic insulated cables are made of copper wire or aluminum stranded wire conductor, with an inner semiconducting layer, an insulating layer made of polyethylene, crosslinked polyethylene, ethylene copolymer, etc., an outer semiconducting layer formed by extrusion or tape wrapping, and copper wire. A metal shielding layer made of overlapping metal tapes such as aluminum, and a pressing layer of cloth tape are successively formed, and a rubber or plastic sheath is provided on the outer periphery of the layers.

When such cables are in use, the metal shielding layer is always grounded for safety reasons, but since this metal shielding layer is formed by overlapping metal tapes, its resistance is low, and as the current capacity increases, electromagnetic induction causes damage to the metal shielding layer. If a potential is induced in the metal shielding layer or if it is grounded at two or more places, a large current will be generated in the metal shielding layer and generate heat, which is not preferable as a cable for large currents.

The present invention provides an electrical cable that solves the above problems by improving the structure of the shielding layer, and in which an insulating or semiconductive tape and a metal tape are wrapped around the outside of the rubber/plastic insulating layer. having an even number of shielding layers,
It is characterized in that the winding direction of the shielding layer is opposite to each other, and a semiconductive tape winding layer is provided between each layer.

The present invention will be described in detail below with reference to embodiments shown in the drawings.

The drawing is a partial vertical cross-sectional view of an embodiment of the electric cable according to the present invention, in which 1 is a stranded conductor made of copper, aluminum, etc., 2 is an internal semiconductive layer, and 3 is a synthetic rubber, polyethylene, crosslinked polyethylene, or ethylene copolymer. The combined insulating layer 4.7 is a shielding layer which is formed by winding insulating tape or semiconductive tape 5, 8 and metal tape 6.9 of copper, aluminum or the like.

This shielding layer 4.7 is provided with an even number of layers, and each layer 4,7
The winding direction is the opposite direction.

Further, a semiconductive tape wrapping layer 10 is provided between each of the shielding layers 4 and 7.

Incidentally, on the outer periphery of the outermost shielding layer, a pressing layer 11 of cloth tape and a sheath 12 such as rubber or plastic are provided as in the case of conventional cables.

Note that a semiconductive layer may be provided between the insulating layer 3 and the shielding layer 4 by extrusion.

As described above, in the cable of the present invention, the shielding layer is composed of an insulating or semiconductive tape and a metal tape wrapped around each other. The resistance in the unit length direction of the cable becomes significantly large, and even if a method of grounding at two or more places is adopted as the grounding method, the circuit current loss of the metal tape can be reduced.

In addition, since the shielding layer is provided with an even number of layers and each layer is wound in the opposite direction, the inductance of the metal tape is smaller compared to winding an odd number of layers or winding an even number of layers in the same direction against high frequency currents such as surges. This method has advantages such as being able to reduce the potential increase on the metal tape to the same level as the conventional overlapping method of metal tape.

[Brief explanation of drawings]

The drawing is a partial vertical sectional view of an embodiment of the power cable according to the present invention. DESCRIPTION OF SYMBOLS 1...Twisted wire conductor, 2...Inner semiconducting layer, 3...Insulating layer, 4, 7... Shielding layer,
5, 8... Insulating or semiconductive tape, 6, 9
...Metal tape, 10...Interlayer semiconducting tape.

Claims (1)

[Claims] 1. On the outside of the rubber/plastic insulation layer, there is an even number of shielding layers made by winding insulating or semiconductive tape and metal tape, and the winding direction of the shielding layers is opposite to each other, and there is no space between each layer. A rubber/plastic insulated capple characterized by having a semi-conductive tape wrapping layer provided on the top.