FR2563042A1 - Electrical power- and data-transmission cable - Google Patents

Abstract

The cable, used for transmitting both medium-voltage electrical power and high-rate data, comprises phase conductors 10 each fitted with an insulating jacket and disposed around a central element 12 including an earth conductor or a carrier. The central element 12 includes a tube of insulating thermoplastic material containing a module having at least one optical fibre associated with a protection element and having an overlength with respect to the said element, the insulating tube being surrounded by the earth conductor or the carrier.

Description

Electric power and information transmission cable
The invention relates to medium voltage electric power transmission cables of the type comprising three phase conductors each provided with an insulating envelope and arranged around a central element comprising an earth conductor (case of an underground network cable ) or a carrier (air network target).

 It has already been proposed to use electric cables to also transmit information, for example by carrier currents; in the conductors themselves.

 The invention aims to provide a cable making it possible to transmit information at high speed without requiring a significant increase in the size or complexity of the cable; on a separate support.

 For this reason; the invention provides in particular a cable of the type defined above in which the central element comprises a tube of thermoplastic material containing a module with at least one optical fiber associated with a protective element and having an excess length relative to this element; tube surrounded by the earth conductor or the carrier.

The invention will be better understood on reading the following description of particular embodiments of the invention; given by way of nonlimiting examples. The description refers to the accompanying drawings; wherein
- Figure 1 is a block diagram of a cable for transmitting electrical energy and information according to the invention; in section along a transverse plane; only a fragment of the phase conductors being shown;
- Figure 2 is a cross section showing the central part of the cable of Figure 1, incorporating the optical module, which is only represented by its outline,
- Figures 3, 4 and 5 are diagrams showing, in cross section, three possible embodiments of an optical module of the kind shown in Figure 2.

 The target shown in Figure 1 has a general constitution which is that of a conventional medium voltage target for buried networks. I1 comprises three phase conductors 10 arranged around a central element 11.

Each conductor consists of a conductive aluminum core 13 protected by alternating semiconductor and insulating elements, a metal screen and a thick external insulating sheath.

 The central element 12 (FIG. 2) comprises a tube of insulating thermoplastic material 14 containing the optical transmission module 15 and surrounded by a layer of wires 16, constituting a ground conductor, and by a lead sheath 18. The wires can in particular be made of an alloy known under the name "ALMELEC" and protect the optical fibers of the module against mechanical stresses.

 The optical module 15 can have very diverse forms, the choice between the possible constitutions being made taking into account in particular the available diameter and the number of optical fibers necessary to ensure the required data rate. In all cases, the module 15 will be provided so that the fiber or each optical fiber that it contains has freedom and has a sufficient length so that it is not tensioned, even if the cable is bent.

 The module shown in Figure 3 comprises a single optical fiber 20, freely mounted in the tube 14 of thermoplastic material or in an additional tube (not shown) placed inside the tube 14. The fiber can have any of the constitutions usual, comprising a core protected by a sheath.

 The core can be index hopping or index gradient, multimode or single mode.

In the variant shown in Figure 4, the optical module 15 contains four optical fibers 22 (this number not being limiting) each placed in a groove of a rod 24 made of plastic material, such as polyethylene or polyamide. The fibers are retained in the grooves by an envelope 26 which will generally be formed by winding a ribbon of insulating plastic material, such as "TERPHANE". In the center of the rod 24 is advantageously embedded a central support wire 28 which can notably be metallic or made of fiberglass. The grooves of the rod 24 are advantageously helical
In the variant shown in Figure 5, the module 15 comprises several tubes of hard thermoplastic material 30 distributed around a central support wire 32 and each containing an optical fiber 34 of diameter much smaller than that of the tube 30 which contains it.

Each fiber 34 has an extra length and therefore has a wavy path in the corresponding tube 30, which avoids any tensile stress. The tube 30 being rigid cannot be crushed under the pressures which it undergoes and guarantees that the fiber remains withdrawn from the mechanical forces possibly exerted on the cable.

 The modules which have just been described can also be used in cables for overhead networks. However, in this case, as a general rule, around the tube made of thermoplastic material 14, a protective sheath against water penetration (aluminum sheath for example) and the components playing the role of ground conductors will be replaced by components intended to make the cable self-supporting. In this case, steel wires 16 and a sheath 18 made of hard plastic material such as polyvinyl chloride or crosslinked polyethylene may be used.

Claims (8)

 1. Medium voltage electrical energy transmission cable comprising phase conductors (10) each provided with an insulating envelope and arranged around a central element (12) comprising an earth conductor or a carrier, characterized in that that the central element (12) comprises a tube of insulating thermoplastic material (14) containing a module with at least one optical fiber (20; 22; 34) associated with a protective element and having an excess length relative to said element, the insulating tube (14) being surrounded by the earth conductor (16) or the carrier.  2. Cable according to claim 1, characterized in that the earth conductor (16) consists of an annular ply of conductive metallic wires.  3. Cable according to claim 1 or 2, characterized in that the earth conductor of the central element (12) is surrounded by a lead sheath.  4. Cable according to claim 1, characterized in that the carrier consists of a sheet of metal wires and in that a metal sheath for protection against ingress of water is disposed around the tube of insulating thermoplastic material (14 ).  5. Cable according to any one of claims 1 to 4, characterized in that the module contains a single optical fiber placed directly in the tube of insulating thermoplastic material (14).  6. Cable according to any one of claims 1 to 4, characterized in that the module comprises several optical fibers (22) placed in the grooves of a rod (24) and trapped by an envelope, possibly produced by winding a band (26).  7. Cable according to claim 6, characterized in that the rod contains a central carrier (28) metal or fiberglass.  8. Cable according to any one of claims 1 to 4, characterized in that the optical module comprises several tubes (30) each containing an optical fiber (34) and distributed around a central support wire (32) in the tube insulator (14).