WO1995022777A1

WO1995022777A1 - Conductor termination

Info

Publication number: WO1995022777A1
Application number: PCT/GB1995/000364
Authority: WO
Inventors: James Charles Baker
Original assignee: Focas Limited
Priority date: 1994-02-22
Filing date: 1995-02-22
Publication date: 1995-08-24
Also published as: ZA951436B; AU1713095A; GB9403298D0

Abstract

The present invention relates to a conductor (1), comprising a fibre optic cable provided with a layer of conductive material. The layer of conductive material and any other conducting components of the cable are removed from an intermediate section (X) of the cable thereby leaving the insulating components of the cable exposed. In this way, an insulated section is provided close to the phase conductor level without the need to splice above ground level.

Description

CONDUCTOR TERMINATION

The present invention relates to a conductor, in particular, a conductor comprising a fibre optic cable provided with a layer of conductive material.

The term "fibre optic cable" is intended to be a general reference to any configuration which comprises one or more optical fibres. The individual optical fibres can be provided with a sheath or sheaths or groups of optical fibres can be enclosed together within a single sheath or sheaths. Moreover, the fibre optic cable can comprise conducting components as well as insulating components. For example, the optical fibres could be guided around a central conducting core provided with one or more grooves to guide the optical fibre cable.

Fibre optic cables are now a well known and developed art and are increasingly replacing older forms of cabling in the field of communication. Fibre optic cables can be employed to provide communication links based on power distribution networks. Conveniently, the fibre optic cable is wound directly onto the already established overhead conductors thus utilising existing networks and linking control centres and sub-stations, as required.

It is well known to wrap fibre optic cable onto overhead phase conductors but the main problem which has to be addressed is how to cope with the voltage gradients which exist, in particular, the phase to ground voltage that the fibre optic cable must pass through when it is brought from the overhead conductor to ground level. One method of protecting the fibre optic cable is to locate the cable in a conduit which extends from phase to ground. The conduit would typically have an outer sheath which is capable of withstanding the surface leakage currents that flow when the system is live.

An alternative which exists to the phase wire wrapped system is that of a phase conductor which comprises a fibre optic cable with an outer conductive layer. Such an arrangement is preferred when reconductoring since the replacement of the conductor and the installation of a communications system are achieved simultaneously. Clearly, housing the fibre optic cable within a conductor provides the highest possible level of protection. However, as in the case of the wrapped system, there is the problem of taking the fibre optic cable from phase to ground.

A number of arrangements already exist and each typically comprises an insulator through which the optical fibres pass before reaching ground level. United States Patent Serial No. 3,746,424, United Kingdom Patent No. 2,083,647 and Australian Patent No. 543,952 describe suitable arrangements. The prior art arrangements are depicted in principle, in Figures 1 and 2.

Figure 1 shows how a conductor which comprises a fibre optic cable with an outer conductive layer is brought to ground level. The conductor A passes from phase conductor level to ground level via three insulators B which serve to isolate the conductor A electrically from the support structure C. The fibre optic cable passes into a splice enclosure E where the optical fibres are spliced to those of a cable G brought up through the insulating housing D. However, there are significant safety issues associated with bringing the live conductor A down the support structure C which can make this arrangement impractical.

Figure 2 shows how the insulating housing D' may be mounted on a bracket F' on the support structure C close to the conductor level in order to overcome the difficulty experienced in the Figure 1 arrangement. The fibre optic cable A' passes into the splice enclosure E' where the optical fibres are spliced to those of cable G' which is brought up the support structure C and through the insulating housing D'. However, the arrangement in Figure 2 requires splicing to be carried out above ground level which is never an easy task. Futhermore, the splices will then be difficult to access should repairs or reconfiguring be required.

There is, therefore, a demand for an improved arrangement for bringing the fibres of a conductor of the kind which comprises a fibre optic cable with an outer conductive layer from phase to ground potential.

Accordingly, the present invention provides a conductor comprising fibre optic cable provided with a layer of conductive material, wherein the layer of conductive material and any other conducting components of the cable are removed from an intermediate section of the cable thereby leaving the insulating components of the cable exposed.

Preferably, the exposed insulating components of the cable are protected by an insulating housing.

Preferably, the insulating housing is convoluted and/or has a shedded outer surface. Preferably, the insulating housing is of substantially non-tracking material.

Preferably, the insulating housing is filled with an insulating solid, liquid or gas, either singly or in combination.

Preferably, the fibre optic cable comprises only insulating components.

Preferably, there is a further conductive layer between the conductive layer and the fibre optic cable.

Preferably, the fibre optic cable comprises both conducting components and insulating components.

Preferably, the conducting components of the fibre optic cable comprise a conducting core having one or more grooves for guiding the optical fibres of the cable.

The present invention also provides a method of bringing a conductor comprising a fibre optic cable provided with a layer of conductive material from a first potential to a lower second potential, comprising the step of removing the layer of conductive material and any other conductive components of the cable from an intermediate section of the cable thereby leaving the insulating components of the cable exposed.

Preferably, the method further includes the step of locating an insulating housing over the exposed insulating components of the cable. Preferred embodiments of the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, of which: Figure 1 depicts a prior art arrangement;

Figure 2 depicts a further prior art arrangement; Figure 3 depicts a first preferred embodiment of the present invention;

Figure 4 depicts a second preferred embodiment of the present invention;

Figure 5 is an enlarged detail of a first type of conductor which is used in the Figure 3 and Figure 4 embodiments;

Figure 6 is a cross sectional view in direction A-A of the conductor in Figure 5;

Figure 7 depicts in partial cross section, a conductor of the type in Figures 5 and 6 provided with an insulating housing according to the present invention; Figure 8 is an enlarged detail of a second type of conductor which is used in the Figure 3 and Figure 4 embodiments;

Figure 9 is a cross sectional view taken along line A-A in Figure 8; Figure 10 is a cross sectional view taken along line B-B in Figure 8;

Figure 11 depicts a conductor of the type in Figures 8, 9 and 10, provided with an insulating housing according to the present invention.

Figures 1 and 2 depict prior art arrangements and have already been described in detail.

Figure 3 depicts a first preferred embodiment of the present invention and shows a conductor 1, which comprises a fibre optic cable with an outer layer of conductive material. The outer layer of conductive material has been removed from a section X inbetween the ends of the conductor. If the fibre optic cable is of the type which comprises conducting components then these components must also be removed to leave only the insulating components. This arrangement provides an insulated section close to the phase conductor level without the need to splice above ground level. Furthermore, the lower section of the conductor 1 can easily be earthed and so can be brought down the support structure easily and safely.

Figure 4 depicts a second preferred embodiment where the conductor 1 passes from phase to ground potential. In this embodiment the exposed section X is protected by an insulating housing 2 mounted on a bracket 3. The insulating housing 2 provides additional protection from physical damage and enables the arrangement to withstand higher voltages in the presence of higher levels of pollution. The housing 2 is preferably a conduit which can be slipped over the exposed insulating components of the fibre optic cable and secured at each end. The housing 2 should preferably be filled with an insulating solid, liquid or gas to improve the integrity of the housing. With this arrangement, the mechanical robustness of the conductor 1 is maintained and the conductor 1, after passing through the housing 2, can be brought down the support structure in the usual way. The housing 2 preferably has a convoluted and/or shedded outer surface 2a to provide a given electrical rating over a shorter length. Again, this embodiment provides the same advantages as the Figure 3 embodiment.

Figure 5 shows a first type of conductor 10 which can be used in the arrangements in Figures 3 and 4. The conductor 10 comprises an outer conductive layer 11 and a fibre optic cable 12. The outer conductive layer 11 can be formed in a number of ways, in this case, by winding metal strands helically around the fibre optic cable 12. Alternatively, the the outer conductive layer 11 is simply a conductive tube or jacket for the fibre optic cable 12. The fibre optic cable 12 in conductor 10 has only insulating components and comprises four groups of optical fibres 13a, 13b, 13c and 13d each having a protective sheath 14. In this type of conductor there is also a conductive tube 15 between the fibre optic cable 12 and the outer conductive layer 11.

Figure 6 is a cross sectional view taken in direction A-A in Figure 5.

Figure 7 depicts, in partial cross section, the conductor in Figure 5 when provided with an insulating housing 2. The housing 2 comprises end caps 17a and 17b and between them a shedded surface 18 which is preferably manufactured from a non-tracking material. At the points where the outer conductive layer 11 has been removed, a heat shrink jacket 19 is applied which ensures that the fibre optic cable 12 is sealed within the housing thereby preventing the ingression of moisture and/or pollution which would lead to the flow of leakage currents on the fibre optic cable 12. The inner casing 20 serves to terminate the support tube 21 and the shedded surface 18. The inner casing 20 is sealed to the inner conductive tube 15 and is provided with a hole 22 to allow the annulus between the outer diameter of the fibre optic cable 12 and the inner diameter of the support tube 21 to be filled with an insulating material. Figure 8 shows a second type of conductor 30 which can be used in the arrangements in Figures 3 and 4. The conductor 30 comprises an outer conductive layer 31 of metal strands (as in Figure 5) and a fibre optic cable 32. In this type of conductor, the fibre optic cable 32 has both a conducting component and insulating components. The conducting component is a conducting core 33 having two helical grooves which serve as guides for two groups of optical fibres 34a and 34b, each having a protective sheath 35. Figure 9 is a cross section in direction A-A in Figure 8. Where the outer conductive layer 31 has been removed, an adhesive-lined heat shrink jacket 36 can be applied and this is clear from Figure 10 which is a cross section in direction B-B in Figure 8. The heat shrink jacket 36 is applied to ensure that the core of the fibre optic cable 32 is sealed.

Figure 11 depicts a conductor of the type in Figures 8, 9 and 10, when provided with an insulating housing 2. In this Figure, the housing 2 has identical components to the housing in Figure 7 and, therefore, like reference numerals indicate like features.

SUBSTITUTE SHEET [RULE 26}

Claims

CLAIMS :

1. A conductor comprising fibre optic cable provided with a layer of conductive material, wherein the layer of conductive material and any other conducting components of the cable are removed from an intermediate section of the cable thereby leaving the insulating components of the cable exposed.

2. A conductor as claimed in Claim 1, wherein the exposed insulating components of the cable are protected by an insulating housing.

3. A conductor as claimed in Claim 2, wherein the insulating housing is convoluted and/or has a shedded outer surface.

4. A conductor as claimed in Claim 3, wherein the insulating housing is of substantially non-tracking material.

5. A conductor as claimed in any of Claims 2 to 4, wherein the insulating housing is filled with an insulating solid, liquid or gas, either singly or in combination.

6. A conductor as claimed in any preceding claim, wherein the fibre optic cable comprises only insulating components.

7. A conductor as claimed in Claim 6, wherein there is a further conductive layer between the conductive layer and the fibre optic cable.

8. A conductor as claimed in any of Claims 1 to 5, wherein the fibre optic cable comprises both conducting components and insulating components.

9. A conductor as claimed in Claim 8, wherein the conducting components of the fibre optic cable comprise a conducting core having one or more grooves for guiding the optical fibres of the cable.

10. A method of bringing a conductor comprising a fibre optic cable provided with a layer of conductive material from a first potential to a lower second potential, comprising the step of removing the layer of conductive material and any other conductive components of the cable from an intermediate section of the cable thereby leaving the insulating components of the cable exposed.

11. A method as claimed in Claim 10, further comprising the step of locating an insulating housing over the exposed insulating components of the cable.

12. A conductor substantially as herein described with reference to Figures 3 to 11 of the acccompanying drawings.

13. A method of bringing a conductor from a first potential to a lower second potential substantially as herein described with reference to Figures 3 to 11 of the accompanying drawings.