Optical waveguides – Optical transmission cable – With electrical conductor in the same cable
Patent
1990-08-06
1991-12-03
Lee, John D.
Optical waveguides
Optical transmission cable
With electrical conductor in the same cable
385113, G02B 644
Patent
active
050695266
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an earth-wire overhead cable having integrated optical transmission elements and consisting of several stranded elements, cf which at least one contains an optical transmission element, whereby the cable features a central steel wire onto which one or several layers of steel wires are stranded and whereby around the stranded core thus formed in at least one steel wire layer, at least one layer of stranded elements made of hard aluminum or of an aluminum alloy is configured around the stranded core thus formed.
In an electricity supply network, the nodal points of the network must be interconnected by communication cables. They enable the exchange of information which is required for the operation of the network. The communication cables are expediently run parallel to the power supply lines or are even integrated in these lines. When a communication cable is integrated in an earth-wire overhead cable, it is advantageous to use an optical transmission element as a communication cable, due to its considerable interference immunity from electromagnetic pulses (DE-AS 26 04 766).
In the Great Britain PS 15 98 540, a cable is described which has one of its conductive, aluminum, stranded elements, replaced by an optical transmission element.
Optical transmission elements such as optical waveguides or optical waveguide bundles are by far less stressable, mechanically-speaking, than the other stranded elements in an earth-wire overhead cable. In particular, the optical transmission elements can become damaged as the result of pinching during the clamping operation when conventional wire clamps are used.
Therefore, the object of the invention is to create a stranded bond of electrically conductive wires and optical transmission elements, in which the optical transmission elements are protected from pinching and other damaging mechanical influences.
The problem is solved according to the invention in that in at least one steel wire layer, at least one steel wire in the stranded bond is replaced by optical transmission element (5, 6, 7).
The advantage of the invention lies in the fact that the steel wires form a tension-proof and transverse-pressure resistant stranded core, in the case of which in at least one stranded layer, at least one steel wire is replaced by optical transmission elements, without the transverse-pressure resistance being significantly reduced. The transverse pressure which develops when the overhead cable is secured in a wire clamp is substantially absorbed by the supporting structure of the steel wires.
One or several layers of stranded elements made of hard aluminum or of an aluminum alloy with good conducting properties are configured around the stranded core. Due to their high conductivity, these elements take over a significant share of the task of transporting the electrical energy.
If a short-circuit should occur, the optical elements are protected from the high temperatures of the aluminum wires, due to the negligible thermal conductivity of the steel wires.
The invention can be advantageously developed by providing the optical transmission element(s) with a casing of a polyetherimide. Such a material is sold, for example, under the trademark "ULTEM" by the General Electric Co. This material offers an optimal protection against mechanical damages and is moreover stable when subjected to a lasting service temperature of up to 170.degree. C. Through this means, the danger of damaging the optical transmission elements in case of an electric short-circuit are reduced. Alternatively, the casing can also consist of an aromatic polyamide, of polyoxymethylene or of a fluorinated polymer.
The invention shall be described based on the exemplified embodiment depicted in the drawings and clarified in the following. In the drawings, the Figures illustrate as follows:
FIG. 1 an earth-wire overhead cable in cross-section, in the case of which the central steel wire has the same diameter as the steel wires stranded on it;
FIG. 2 an earth-wire overhead cable, in the case of which
REFERENCES:
patent: 4671611 (1987-06-01), Allemand et al.
patent: 4801192 (1989-01-01), Wehner
patent: 4861947 (1989-08-01), Altermah et al.
patent: 4902097 (1990-02-01), Worthington et al.
Patent Abstracts of Japan, vol. 2, No. 61 (E-78) 1703, May 9, 1978 & JP-A-53 24582 (Hitachi Densen) Jul. 3, 1978.
Heartney Phan T.
Lee John D.
Siemens Aktiengesellschaft
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