GB2328327A

GB2328327A - Method and apparatus for use in installing overhead conductors by using a suspended pulley

Info

Publication number: GB2328327A
Application number: GB9821278A
Authority: GB
Inventors: Peter Derek Crebbin; John Bevan
Original assignee: Manx Electricity Authority
Current assignee: Manx Electricity Authority
Priority date: 1995-03-24
Filing date: 1995-03-24
Publication date: 1999-02-17
Anticipated expiration: 2015-03-24
Also published as: GB2328327B; GB9821278D0; GB2299219B; GB9506090D0; GB2299219A

Abstract

A method and apparatus are provided for replacing one of several existing overhead conductors which pass over a road or other thoroughfare. A pulley 40 is suspended from one, or preferably two, of the other existing conductors above the road or other thoroughfare, and the conductor to be replaced is supported on the pulley. The replacement conductor is connected to one end of the conductor to be replaced, which is then reeled in to pull the replacement conductor over the pulley to the reeling in point. The axis of the pulley 40 is horizontal and perpendicular to the conductor. The pulley may be suspended from the conductors by cables 48 with hooks at the end.

Description

METHODS AND APPARATUS FOR USE IN INSTALLING OVERHEAD CONDUCTORS This invention relates to methods and apparatus for use in installing overhead conductors, and is more particularly but not exclusively concerned with methods and apparatus for use in replacing one of a plurality of overhead conductors constituting an overhead power line with a conductor which incorporates a fibre optic cable.

Three phase, three conductor, power lines are typically supported in straight sections by several spaced apart poles or pairs of poles, the poles at each end of a section being referred to as section poles and the poles between the section poles being referred to as intermediate poles: the term "pole" as used hereinafter in this introduction and in the claims should be understood to include both a single pole at a given location along the power line and a pair of poles at a given location along the power line. Typically, but not exclusively, the section poles are positioned at points where there is a change of direction of the power line.

Because of this, the conductors are normally terminated at section poles, and conductive jumpers are used to connect the adjacent ends of the conductors, to maintain electrical continuity while avoiding the damaging lateral forces which could result if the conductor itself followed the change of direction.

In order to incorporate an improved signalling or telecommunications capability in such a power line, it is currently being proposed to replace one of the conductors, typically the centre one, with a special conductor incorporating a fibre optic cable. However; overhead power lines frequently cross roads. As a result, their replacement can cause severe obstruction, and in certain circumstances, may even require temporary closure of a road: in either event, it is likely that local authority authorisation will be required. It is an object of the invention to alleviate this problem.

According to the present invention, there is provided a method of replacing one of a plurality of existing overhead conductors which pass over a road or other thoroughfare with a new conductor, the method comprising attaching pulley means to at least one of the other existing conductors over said road or other thoroughfare, and passing said one existing conductor over the pulley means, attaching the new conductor to one end of said one existing conductor, and reeling in said one existing conductor from the other end thereof, thereby drawing the new conductor over the pulley means until it reaches the reeling-in location.

The pulley means is preferably attached to said at least one of the other existing conductors at two spaced apart points. Where said one existing conductor is the middle conductor of a group of three conductors, constituting, eg a power line, the pulley means is preferably attached to each of the other conductors at two spaced apart points.

The or each pulley means preferably comprises a single pulley.

The invention also includes a support device for implementing the methods of the three preceding paragraphs.

The invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 shows the top of a pair of section poles for supporting a three phase, three conductor, power line, incorporating additional means, including a pulley, for use in replacing the existing middle conductor with a new conductor incorporating a fibre optic cable; Figure 2 shows part of a device for use in the method of the present invention at locations where the power line of Figure 1 crosses a road or other thoroughfare; Figure 3 shows a further part of the device of Figure 2; Figure 4 is a very schematic diagram illustrating a power line having its centre conductor replaced by a method involving the present invention; and Figure 5 shows the new conductor of Figure 4 after installation.

The section poles of Figure 1 are indicated generally at 10, and are typically about ten metres high and about one hundred cms apart. An elongate rectangular metal support frame 12 is secured to and extends between the tops of the poles 10, with its longer sides 14 embracing both poles and its shorter sides 16 disposed about thirty five cms outside the space defined between the poles. A short centre strut 16a joints the respective mid-points of the longer sides 14 of the frame 12. Respective porcelain insulators 18 of known kind are secured to and project upwardly from the shorter sides 16 of the frame 12 and the centre strut 16a, while three pairs of tension insulators 20, also of known kind, are spaced along, and pivotally connected to, the longer sides 14 of the frame, one insulator of each pair being on one side 14 of the frame, and the other insulator of each pair being on the other side 14: only the outer insulators 18 and the outer pairs of tension insulators 20 are shown in Figure 1, for reasons that will become apparent hereinafter.

The section poles 10 and the frame 12 together support the conductors of a three phase, three conductor power line, the two outer conductors of which are indicated at 22 in Figure 1: the reason for the omission of the centre conductor will also become apparent hereinafter. The direction of the power line, as it goes from the left of Figure 1 to the right, changes to the right at the section poles 10, so to avoid the lateral stresses that this change of direction could induce in the conductors 22 if they were continuous, the conductors are terminated at respective ones of the tension insulators 20 of the outer pairs. Electrical continuity between the adjacent terminated ends of the conductors 22 is maintained in known manner by respective jumpers 24, which are supported on the insulators 18.

The centre conductor of the power line is in the course of being replaced by a new conductor incorporating a fibre optic cable, hence the omission of the centre conductor from Figure 1. To facilitate the replacement, and in accordance with the present invention, a vertically upstanding metal support structure 28 is temporarily secured to the frame 12 of each pair of section poles 10. The support structure 28 comprises two uprights 30, each secured to a respective one of the longer sides 14 of the frame 12 just to the right of its midpoint as viewed in Figure 1, two bracing struts 32, each of which extends from the top of a respective upright 30 to the side 14 of the frame 12 to which that upright is secured, but just to the left of its midpoint, and a cross-piece 34 which interconnects the tops of the uprights 30. A pulley 36 is supported from the right side of the cross-piece 34, ie the side facing away from the bracing struts 32, with its rotational axis inclined or angled from the horizontal to extend generally parallel to the struts 32.

It will of course be appreciated that the power line is de-energised prior to the fitting of the angle pulley 36 and its support structure, and that it remains de-energised throughout the subsequent steps in the replacement of the centre conductor of the power line.

The next step in the replacement procedure, the centre conductor at all intermediate poles (not shown) having been unbound and placed in rollers fitted to the insulators on the intermediate poles, is to disconnect the terminated ends of the centre conductor from its tension insulators 20 and to connect them together so that they extend over the angle pulley 36: a short length of conductor can be used to join the terminated ends if necessary. At the same time, the centre jumpers 24 are removed and discarded. At this point, the centre conductor to be replaced forms a single continuous length over the entire length thereof to be replaced, this continuous length passing over each of the angle pulleys 36 (as well as over the rollers at the intermediate poles) In addition to fitting an angle pulley 36 and its support structure 28 to the top of each pair of section poles 10, and in accordance with the present invention, a device of the kind indicated at 40 in Figure 2 is secured to the two outer conductors 22 above each road or other thoroughfare crossed by the conductors. Thus the device 40 comprises a rectangular frame 42, whose two longer sides 44 extend parallel to the conductors 22 in use. A pulley 46 is mounted between the sides 44 of the frame 42, with its rotational axis extending perpendicularly between the sides 44. Four cables 48, attached to respective corners of the frame 42 at the ends of the sides 44, secure the frame to the outer conductors 22, each cable 48 terminating in a hook-like clamp 50, shown in Figure 3, by which it can be clamped to the respective conductor 22. The angle between the clamps 50 and the cables 48 is adjustable at the connection point 52 of Figure 3, such that the cables 48 each extend inwardly and downwardly at an acute angle from the respective conductor 22, so as to support the device 40 fairly closely beneath the conductors 22, and thus well above the road or other thoroughfare therebeneath.

The aforementioned single continuous length of the centre conductor to be replaced is then placed upon and supported by the or each device 40.

The replacement proper of the centre conductor can now begin.

As shown in Figure 4 (where each of the pairs of poles 10 has been replaced by a single pole 10 for the sake of simplicity), the new conductor 26 incorporating a fibre optic cable, wound on a drum 60, has its free end passed through an automatic tensioning device 62 and connected at 64 to one end of the continuous length of the centre conductor to be replaced, indicated at 22a in Figure 4. The other end of the centre conductor 22a is passed through another automatic tensioning device 66 and wound onto a take-up drum or winch 68. The take-up drum 68 is then used to pull the centre conductor 22a, and therefore the new conductor 26 incorporating the fibre optic cable, through the respective pulleys 36 on all the poles 10, until the new conductor 26 reaches the take-up drum 68. As mentioned earlier, a device 40 incorporating a pulley 46 facilitates the crossing of any road or other thoroughfare by the new conductor 26 with a minimum of disruption.

Once the above procedure has been completed, the new conductor 26 needs to be properly supported at each pole 10 (or more accurately, at each pair of poles 10), whether they be intermediate poles or section poles. To this end, and as shown in Figure 5, the support structure 28 is removed and the centre insulator 18 and the centre pair of tension insulators 20 are replaced on (ie restored to) the respective frame 12 of each pair of poles 10. Then, the correctly tensioned new conductor 26 is bound at 70 to a short length of steel cable 72 secured to a respective tension insulator 20 of each centre pair, while an untensioned loop 74 of the new conductor 26 extends between the respective one of the cables 72/tension insulators 20, with its midpoint supported on the centre insulator 18. Finally, preformed double distribution ties are fitted at the intermediate pole positions.

If necessary, the section poles at each end can be provided with temporary stays to give them additional support during the replacement procedure.

It will be appreciated that several modifications can be made to the described implementations of the various aspects of the invention. For example, the device 40 of Figure 2 could be supported from only one other conductor 22, instead of from two. Additionally, the device 40 can obviously be used to advantage when replacing an existing conductor 22 with another conductor of the same type (as opposed to one incorporating a fibre optic cable).

Claims

1. A method of replacing one of a plurality of existing overhead conductors which pass over a road or other thoroughfare with a new conductor, the method comprising attaching pulley means to at least one of the other existing conductors over said road or other thoroughfare, and passing said one existing conductor over the pulley means, attaching the new conductor to one end of said one existing conductor, and reeling in said one existing conductor from the other end thereof, thereby drawing the new conductor over the pulley means until it reaches the reeling-in location.

2. A method as claimed in claim 1, wherein the pulley means is attached to said at least one of the other existing conductors at two spaced apart points.

3. A method as claimed in claim 1, for use where said one existing conductor is the middle conductor of a group of three conductors, wherein the pulley means is attached to each of the other conductors at two spaced apart points.

4. A method as claimed in any one of claims 1 to 3, wherein the or each pulley means comprises a single pulley.

5. A support device adapted for use in the method of claim 1, the device comprising a pulley and means for suspending the pulley from at least one of the other overhead conductors above the road or other thoroughfare such that the axis of the pulley is generally horizontal and generally perpendicular to said at least one other conductor, whereby said one conductor can be supported on the pulley and used to draw the replacement conductor thereover without unduly obstructing the road or other thoroughfare.

6. A support device as claimed in claim 5, adapted for use in the method of claim 2, wherein the suspending means comprises two cables ending in respective hooks which engage said at least one other conductor at two spaced apart points.

7. A support device as claimed in claim 6, adapted for use in the method of claim 3, wherein the suspending means comprises two further such cables with hooks for engaging yet another conductor generally parallel to said at least one other conductor and said one conductor.

8. A support device as claimed in claim 6 or claim 7, wherein each hook includes clamping means for clamping it to the respective conductor.

9. A support device adapted for use in replacing one of a plurality of existing overhead conductors which pass over a road or other thoroughfare with a new conductor, the device being substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.