WO2009014457A1

WO2009014457A1 - Equipotential bonding system

Info

Publication number: WO2009014457A1
Application number: PCT/NZ2008/000179
Authority: WO
Inventors: Goran Stojadinovic
Original assignee: Vector Limited
Priority date: 2007-07-24
Filing date: 2008-07-24
Publication date: 2009-01-29
Also published as: AU2008279894A1; NZ556735A; AU2008279894B2

Abstract

A system for creating anequipotential along a pole comprising a conductive downlead for fixing to andextending substantially along the length of the pole to electrically connect tothe pole substantially along the length of the conductive downlead or at leastat intervals along the length of the conductive downlead sufficient to create anequipotential along the pole, anda liquid distribution system for supplying aliquid between the conductive downlead and thepole.

Description

"EQUIPOTENTIAL BONDING SYSTEM"

TECHNICAL FIELD

This invention relates to securing devices and a method and apparatus for the electrical equipotential bonding on power poles or posts that are used in electrical and/or telecommunication networks. Particularly the method and apparatus of the present invention is applied to concrete poles or posts.

BACKGROUND When working on overhead power lines, for example, maintaining the overhead power lines or items associated with power poles or posts, it is a requirement to have appropriate earthing and equipotential bonding at the work site around power poles and lines. There are also hazards associated with working on de-energised lines, where should one of the power line phases be inadvertently re-energised, the worker is likely to be electrocuted.

To provide further detail, when one phase of a set of power lines is inadvertently livened a fault current is created and goes directly into the ground at the work site, where overhead lines are temporarily earthed. If at the same time a worker is in contact with a concrete pole and overhead lines, and if a concrete pole surface is not at the same potential as the lines, a part of the fault current will go through the worker's body, electrocuting the worker. This occurs because a concrete pole is neither an isolator nor a conductor. It behaves more like a semiconductor, creating a potential difference between the ground and the surface of the pole.

A fatal accident, due to the very- problem described above, occurred at Arahura in the West Coast on the Soudi Island of New Zealand on a 66kV line between Otira and Hokitika on 10

January 2005. Another incident happened in September 2006 in New Zealand, when two workers on a pole felt the re-livening of a line but were uninjured. In both incidents there was an inadvertent livening of one phase somewhere along the de-energized lines. In both incidents the lines were earthed according to current best industry practice. However, the earthing and equipotential bonding at both work sites were insufficient to prevent substantial fault currents and danger to the line workers.

This is a world wide problem which has not been addressed properly. The New Zealand electricity industry safety rules establish general principles and minimum requirements for safety. As a solution for new poles, it has been recommended that all newly manufactured concrete poles have an integral earth from the top to the bottom of pole. However, there is no an adequate solution for the existing concrete poles. Existing solutions cause damage to the poles or provide insufficient grounding and equipotential bonding. There are hundreds of thousands existing concrete power poles around the globe.

It is an object of the present invention to attempt to provide a method and apparatus for the electrical equipotential bonding of power poles and securing of earthing leads to power poles that goes some way to overcoming the abovementioned disadvantages in the prior art or which will at least provide the industry with a useful choice.

SUMMARY OF THE INVENTION

In a first aspect, the invention broadly consists in a system for creating an equipotential along a pole comprising: a conductive downlead for fixing to and extending substantially along the length of the pole to electrically connect to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead sufficient to create an equipotential along the pole; and a liquid distribution system for supplying a liquid between the conductive downlead and the pole.

Preferably, the system for creating an equipotential along a pole comprises a second conductive downlead for fixing to and extending substantially along the length of the pole to electrically connect to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead.

Preferably, the liquid distribution system comprises a bladder also extending substantially along the length of the pole. More preferably, a bladder is provided internally within the or each conductive downlead.

Preferably, the system for creating an equipotential along a pole comprises at least one securing device for fixing the conductive downlead to the pole. More preferably in a first form, the securing device is a clamp. Even more preferably in this first form, the clamp comprises a recess arranged to receive the conductive downlead. More preferably in a second form, the securing device comprises an elongate member made of a conductive material and capable of extending within a hole in the pole, a spring made of conductive material and attached to the elongate member and arranged to hold the elongate member in the hole, and a clamp made of conductive material and attached to the elongate member to in use clamp the conductive downlead to the surface of the pole.

Preferably, the liquid distribution system comprises a pump for pumping a liquid into the bladder.

Preferably, the system for creating an equipotential along a pole includies a scissor gripping device for securing the conductive downleads near the top of the pole.

In a second aspect, the invention broadly consists in a method of creating an equipotential along a pole comprising the steps of:

(a) fixing a conductive downlead substantially along the length of the pole, such that the conductive downlead is electrically connected to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead sufficiently to create an equipotential along the pole; and

(b) supplying a liquid between the conductive downlead and the pole.

Preferably, the method of creating an equipotential along a pole comprises the steps of:

(a) fixing a second conductive downlead substantially along the length of the pole, such that the second conductive downlead is electrically connected to the pole substantially along the length of the second conductive downlead or at least at intervals along the length of the second conductive downlead sufficiendy to create an equipotential along the pole; and (b) supplying a liquid between the second conductive downlead and the pole.

Preferably, the method of creating an equipotential along a pole comprises the step of fixing the conductive downlead to the pole with a securing device. More preferably in a first form, the securing device is a clamp. Even more preferably in this first form, the clamp comprises a recess arranged to receive the conductive downlead. More preferably in a second form, the securing device comprises an elongate member made of a conductive material and capable of extending within a hole in the pole, a spring made of conductive material and attached to the elongate member and arranged to hold the elongate member in the hole, and a clamp made of conductive material and attached to the elongate member and which clamps the conductive downlead to the surface of die pole.

Preferably, the method of creating an equipotential along a pole comprises the step of pumping a liquid into the bladder.

Preferably, the method of creating an equipotential along a pole comprises securing the conductive downleads substantially near the top of the pole with a scissor gripping device.

In a third aspect, the invention broadly consists in a system for creating an equipotential along a pole comprising: a conductive downlead for fixing to and extending substantially along the length of the pole; and at least one securing device arranged to clamp and electrically connect the conductive downlead to die pole sufficient to create an equipotential along the pole.

Preferably, die system for creating an equipotential along a pole comprises a second conductive downlead for fixing to and extending substantially along the length of the pole to electrically connect to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead.

Preferably, the system for creating an equipotential along a pole comprises a liquid distribution system for supplying a liquid between the conductive downlead and the pole. More preferably, the liquid distribution system comprises a bladder also extending substantially along the length of the pole. Even more preferably, a bladder is provided internally within the or each conductive downlead.

Preferably, the clamp comprises a recess arranged to receive the conductive downlead.

Preferably, the liquid distribution system comprises a pump for pumping a liquid into the bladder. Preferably, the system for creating an equipotential along a pole includes a scissor gripping device for securing the conductive downleads substantially near the top of the pole.

In a fourth aspect, the invention broadly consists in a method of creating an equipotential along a pole comprising the steps of:

(a) extending a conductive downlead along the length of the pole; and

(b) clamping and electrically connecting the conductive downlead to the pole sufficiently to create an equipotential along the pole.

(a) extending a second conductive downlead along the length of the pole; and

(b) clamping and electrically connecting the second conductive downlead to the pole sufficiently to create an equipotential along the pole.

Prferably, the method of creating an equipotential along a pole comprises a liquid distribution system for supplying a liquid between the conductive downlead and the pole. More preferably, the liquid distribution system comprises a bladder also extending substantially along the length of the pole. Even more preferably, a bladder is provided internally within the or each conductive downlead.

Preferably, the method of creating an equipotential along a pole includes securing the conductive downleads are secured substantially near the top of the pole with a scissor gripping . device.

. In a fifth aspect, the invention broadly consists in a device to secure an earthing lead to a pole by way of a hole in said pole comprising: an elongate member, made of a conductive material, capable of extending within said hole in said pole, a spring, made of a conductive material, attached to said elongate member and holding said elongate member in said hole, and a clamp, made of a conductive material, attached to said elongate member and in use clamping said earthing lead to the surface of said pole.

Preferably said elongate member is a hollow pipe that is closed at one end and open at the other end.

Preferably said hollow pipe has a liquid receptacle attached to it and at least one aperture formed along said pipes length, such that in use when said pipe is inserted into a hole in said pole said liquid can flow from said receptacle along said pipe and out said at least one aperture to soak into said pole.

In a sixth aspect, the invention broadly consists in a method of creating an equipotential along a pole comprising the steps of: running an earthing lead down a pole, attaching at least one conductive securing device to at least one hole in said pole, said securing device having a elongate member, capable of extending within said hole, a spring attached to said elongate member and holding said elongate member in said hole, and a clamp attached to said elongate member that in use clamps said earthing lead to the surface of said pole, and clamping said earthing lead to an earthing rod in the ground surrounding said pole.

Preferably said method of creating an equipotential along a pole further comprises the step of attaching a liquid receptacle to said securing device, such that in use, liquid flows into said pole creating an ionic solution in said pole and reducing the resistance of said pole.

Preferably said method of creating an equipotential along a pole further comprises the step of attaching one or more auxiliary securing devices to- said pole to further secure said earthing lead to said pole.

The invention consists in the foregoing and also envisages constructions of which the following gives examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred forms of the present invention will now be described with reference to the accompanying drawings in wjiich: Figure 1 is a perspective view of part of a concrete power pole with an unsecured earthing downlead, with a part of the pole cut-away;

Figure 2 is a front view of a power pole and an equipotential bonding system of the invention; Figure 3 is a side view of the power pole and equipotential boding system of Figure 2;

Figure 4 is a plan view of a first embodiment securing device which may be used in the equipotential bonding system of the invention, fitted to a pole;

Figure 5 is a plan view of a second embodiment securing device which may be used in the equipotential bonding system of the invention, fitted to a pole; Figure 6 is a perspective view of a third embodiment securing device which may be used in the equipotential bonding system of the invention, fitted to a pole;

Figure 7 is a perspective view of a liquid distribution system which may be used in the equipotential bonding system of the invention;

Figure 8 is a perspective view of a carrying device which may be used in the equipotential bonding system of the invention;

Figure 9 is a perspective view of a scissor gripping device which may be used in the equipotential bonding system of the invention;

Figure 10 is a perspective view of earthing electrodes which may be used in the equipotential bonding system of the invention; Figure 11 is a lengthwise cross-sectional view of a concrete power pole with two of the securing devices of a first embodiment of the present invention securing the earthing downlead to the concrete pole;

Figure 12 shows a securing device of the first embodiment of the present invention as shown in Figure 11 ; Figure 13 shows a securing device of a second embodiment of the present invention;

Figure 14 is a lengthwise cross-sectional view of a concrete pole with an earthing downlead secured by two of the securing devices of Figure 13;

Figure 15 shows a first auxiliary securing device for use with the either of the securing devices of Figures 11 or 12; Figure 16 shows a second auxiliary securing device for use with the either of the securing devices of Figures 11 or -12;

Figure 17 shows a third auxiliary securing device for use with the either of the securing devices of Figures 11 or 12; and

Figure 18 shows a concrete pole where the devices of Figures 12, 15, 16 and 17 are in use to secure an earthing downlead and provide equipotential bonding of the pole. DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The invention generally relates to a system, a method, and an apparatus for the electrical equipotential bonding on power poles or posts that are. used in electrical and/or telecommunication networks. Particularly, the system, method and apparatus are applied to concrete poles or supporting structures.

The present invention provides means provide equipotential bonding of a power pole. The power pole may be made from concrete of any suitable shape or size. . —

Referring to Figure 1 , concrete poles 1 generally have a number of reinforcing bars or rods 2 set in them when made. The main objective of the present invention is to create an efficient equipotential bonding of the pole by creating a low resistance path between an earthing conductor or earthing downlead 4 and the steel reinforcing rods 2.

On most concrete power pole^'s 1 there are a number of small transverse holes 3 formed at various points along the length of the pole. These holes 3 extend completely through the pole and are generally used for fastening cross-arms, cables, transformers or the like to a pole 1.

Referring to Figs. 2 and 3, the equipotential bonding system comprises a downlead 4 which is made from a conductive material. The downlead 4 may be a round or flat braided conductor of adequate size. A flat braided conductor is preferred for use with the equipotential bonding system because it generally will have a larger surface contact with a pole, compared to a round one. In use the downlead 4 is connected to ground. The downlead 4 may be connected to at least one earth electrode 100 at the base of pole 1. Preferably, two downleads 4 are provided and they are each connected to an earth electrode 100 driven into the ground at the base of the pole 1. However, the downleads 4 may be grounded in any suitable number and any suitable amount of downleads 4 may be used.

The equipotential bonding system comprises at least one securing device 102 for securing the downleads 4 to the pole 1. The securing device 102 may be a clamp or any other suitable securing device as described in detail below.

The equipotential bonding system comprises a liquid distribution system 104 to distribute water, an electrolyte, or any other suitable liquid along the length of the downlead 4. This liquid distribution may enhance the electrical connection and conductivity between the pole 1 and the downlead 4.

Referring to Fig. 4, a first preferred embodiment securing device 102 is a first clamp 106. The first clamp 106 comprises first 108 and second 110 L-shaped body members. The body members 108, 110 are axially slidable relative to each other. The body members may be slidibly coupled telescopically, however any suitable sliding connection may be used such as the body members 108, 110 sliding next to each other. A biasing member 112 may be connected to both of the body^" members 108, 110. The biasing member may tension the body members 108, 110 towards each other ie the clamp closed. The biasing member 112 is preferably a spring but any suitable biasing member may be used. The spring may be provided internally.

Referring to Fig. 5, a second preferred embodiment securing device 102 is a second clamp 114. The second clamp 114 is similar to the first clamp 106 except that the biasing member 112 is provided external to the body members 108, 110.

Referring to Fig 6, a third preferred embodiment securing device 102 is a pump-action clamp 116. The third clamp may have a first extending part 108 axially slidibly connected to a second jaw member 110. A third jaw member is provided at the other end of part 108. The 'jaw member 110 may comprise a handle 118 such that when the handle 118 is squeezed by a user, the second body member 110 slides along the second body member 108 making the distance between the clamp jaws smaller. The jaw 110 grips the first body member 108 such that a force in the opposite direction will not move the body members 108, 110 apart. However, the pump-action clamp 116 may comprise a release mechanism which when actuated will release the grip between the body member 108, and jaw 110 such that the pump-action clamp 116 may be removed.

Referring to Figs. 4 to 6, the clamps 106, 114, 116 each comprise two individual jaws 120 which are axially movable relative to one another with the body members 108, 110. Preferably, each jaw 120 comprises a recess arranged to receive the downlead 4 without crushing it against the pole 1. Preferably, the securing devices 102 are made of a conductive material such as metal or sheet metal, however any suitable conductive material may be used. Alternatively, only some parts of the securing devices 102 may be made of conductive materials.

In the first and second preferred embodiment securing devices 102, in use a downlead 4 is placed next to the pole 1 so that the downlead 4 extends along the length of the pole 1. One jaw 120 is then placed over the downlead 4 and in contact with the side of the pole 1, with the downlead 4 preferably substantially situated in the recess 122. The other jaw 122 may then be stretched to contact with the opposing side of the pole 1. A second downlead 4 may be provided extending along the opposing side of the pole 1. The second downlead 4 is preferably substantially situated in another recess 122. The biasing member 112 may bias the two jaws 120 towards each other so that the securing device itself 102 is fastened to the pole 1 and the downleads 4 are also fastened to the pole 1.

In the third embodiment securing device 102, a downlead 4 is placed extending along the length of the pole 1. The jaws 120 of the pump-action clamp 116 are opened to be wider than the width of the pole 1. A jaw 120 of the pump-action clamp 116 is placed over the downlead 4 and in' contact with a side of the pole 1 , with the downlead 4 preferably substantially situated in the recess

122. The other jaw 120 is brought to the opposing side of the pole 1 and the handle 118 is squeezed one or more times so that the jaws 120 are brought together to each abut with and clamp opposing sides of the pole 1 such that any downleads 4 provided are fastened to the pole 1. A second downlead 4 may be clamped in another recess 122 of a jaw 120 as described above.

When the downleads 4 are fastened to the pole 1 in this manner, they may have an electrical connection with the pole 1. Referring to Figs. 2 and 3, at least one securing device 102 may be used to fasten the downleads 4 to the pole 1. However, preferably more than one securing device 102 is used to fasten the downleads 4 to the device. Securing devices 102 may be used at for example 50cm intervals along the length of the downleads 4 to secure them to the pole 1. However any suitable number of securing devices 102 at any suitable constant or variable interval may be used to secure and sufficiently electrically connect the downlead 4 to the pole 1 such that an equipotential is created on the pole 1. Any suitable securing device 102 that will achieve this may be used.

Referring to Fig. 7, the equipotential bonding system comprises a liquid- distribution system

104. The liquid distribution system 104 is used to provide a liquid between the downleads 4 and the pole 1 to help provide a better electrical connection between the downleads 4, the pole 1, and the reinforcing rods 2 which may help the. pole 1 achieve a better equipotential along its length.

The liquid may be water, an electrolyte^", or any other suitable liquid.

Electrolytes (also known as ionic solutions) commonly exist as solutions of acids, bases or salts. Water inside of concrete creates an ionic solution (electrolyte) called calcium hydroxide - n -

Ca(OH)₂ (also known as 'slaked lime' or 'hydrated lime'). It is obtained when the calcium oxide (called lime or quicklime) from the cement is mixed (slaked) with water. Water is a solvent in which calcium oxide is dissolved through a hydration process, thus creating a strong electrolyte. The calcium oxide is always present in a concrete, no matter how old the concrete is. It is preferred that the liquid used is pure water because it is inexpensive, ready available, and does not cause more rust to the steel reinforcement than is caused naturally by rain. However, electrolytes could be used so long as they are relatively inexpensive and if proven, that they do not cause additional deterioration of pole and steel reinforcement.

When a concrete pole is wet, any electrical potential difference between two points in the concrete pole or between the surface of pole and its internal steel reinforcing bars will create an ionic current. With the increase of liquid content inside a pole, by way of the liquid in the receptacle in use flowing through the pipe and into the hole in the pole and subsequendy into the concrete surrounding the hole, the resistance between any two points at its surface, or between the surface of pole and its internal reinforcing bars, will drop sharply to about 20% of the poles resistance when the pole is dry, that is, the conductivity is increased several times. Wetting the pole therefore reduces the potential difference between the pole surface and its steel reinforcing bars, and creates an efficient equipotential bonding.

Concrete may quickly absorb liquid and release it very slowly, so the liquid will stay inside a concrete for a long time and can be easily replenished during any work that is conducted on overhead lines near the pole, on devices on the pole or the pole itself.

The liquid distribution system 104 may comprise a bladder 124 extending along the length of the downleads 4 (shown in Figs. 4 and 5). More preferably, the bladder 124 is provided internally within the downlead 4. Alternatively, the bladder 124 may be provided external to the downlead 4. The bladder 124 may be used to carry and distribute a liquid along the length of the downleads 4. In a preferred embodiment, the bladder 124 may be a flexible conduit such as a length of hose with a series of holes along one side such that a liquid in the conduit can escape and pass through the braids of the downlead 4 and contact with the pole 1. In this embodiment, the hose may be provided inside the downlead 4 and the holes may be directed to face towards the pole 1. The hose may be made from plastic or any other suitable material. Alternatively, the bladder 124 may be a porous material or any other suitable type of bladder that can transport and release a liquid along its length. Alternatively again, the liquid may be provided in any other suitable manner. In the preferred embodiment liquid distribution system 104 above, generally there is no liquid in the hose before the downleads 4 are fastened to the pole 1. The downleads 4 each containing an empty hose may be fastened to the pole 1 as described above then the hoses may be filled. A pump 126 may be used to pump a liquid into the hoses once they have been fastened along the length of the pole. The pump 126 may be a manual pump, an electric pump, or any suitable pump. As the liquid enters the hoses, the downleads 4 and hoses will expand, preferably into the space of the recesses 122. If two or more downleads 4 and bladders 124 are provided, liquid may be supplied to all bladders 124 by a single pump 126 through a tap connector 128 for example. The tap connector may be connected to the bladders 124 through standard garden connectors such as garden hose and any suitable hose coupling devices. Alternatively, separate liquid distribution system 104 may be provided for each bladder 124 and downlead 4. Any suitable liquid distribution system may be used to supply a liquid to a bladder 124 provided in a downlead 4. Generally when the bladder 124 is filled with a liquid, the liquid may seep out of the bladder 124, through the braids of the downlead 4, and soak into the material of the pole 1 to make a lower resistance connection between the downlead 4 and the reinforcement rods 2 of the pole 1. This may help create an equipotential along the pole 1.

Referring to Figs. 2, 8, 9, and 10, a method of installing an equipotential bonding system will be described. Each downlead 4 may have an associated bladder 124. For example, the downlead 4 may be a hollow, braided conductor with a hose with a series of holes along one side contained inside.

With particular reference to Fig. 8, the downlead 4 and associated bladder 124 may be initially contained on a carrying device 130. The carrying device may comprise a frame 132 with a rotatable reel 134. The reel 134 may comprise one or more compartments suitable for winding one or more downleads 4 and associated bladders 124 onto. However, the carrying device 132 may be any suitable device. Preferably, there is no liquid in the bladders 124 while they are contained on the carrying device 132. A user may take the ends of the downleads 4 and raise them from the bottom of the pole 1 to near the top of the pole 2, unwinding them from the carrying device 132 in the process. The downleads 4 may be raised using a ladder, cherry picker, or in any other suitable manner.

With particular reference to Fig. 9, the ends of the downleads 4 may be secured near the top of the pole 1 with a scissor gripping device 136. The scissor gripping device 138 may comprise two cross-bars 138 with an off-centre pivot point. Preferably, the two top arms of the scissor gripping device 138 are shorter than the two bottom arms. The ends of the downleads 4 are connected to the two bottom arms. The two top arms may each be provided with a gripping finger 140 that abuts with the sides of the pole 1. When the weight of the downleads 4 is placed on the bottom arms, the cross-bars 138 will pivot so that the gripping fingers 140 are squeezed together around the pole 1, holding the downleads 4 near the top of trie pole 1. Preferably the scissor gripping device 136 is made from a conductive ^"material such as metal, however any suitable material may be used. Alternatively, any suitable means may be used to hold the end of the downleads 4 near the top of the pole 1.

With particular reference to Fig. 2, the downleads 4 and associated bladders 124 may be further secured along the length of the pole 1. Preferably, the downleads 4 are secured to the pole 1 such that the distance between the downleads 4 and die reinforcing rods 2 are minimised. This will help lower the resistance between the downleads 4 and the reinforcing rods 2. The reinforcing rods 2 of some poles 1 are provided near the corners. This means that the downleads 4 should be secured as close to the corners as possible on such poles 1. At least one securing device 102 may be attached to the pole 1 such that the downleads 4 are secured to the pole 1. In embodiments when the bladder 124 is contained in the downlead 4 and will eventually be filled with a liquid, it is preferred that the downleads 4 are placed in recesses 122 of the securing devices jaws 120. Preferably, more than one securing device 102 is used. More preferably, securing devices are used at 50cm intervals along the length of the downleads 4. However, any suitable number of securing devices 102 may be used, and the securing devices do not necessarily need to be of the same type, so long as the downlead 4 is sufficiendy electrically connected to the pole 1 to create an equipotential on the pole 1.

With particular reference to Fig 10, each downlead 4 may be electrically connected to an earth electrode 100 with a connector 142. If more than one downlead 4 is provided, each downlead 4 may be provided with its own earth electrode 100, or more than one downlead 4 may be connected to a single earth electrode 100. The connector 142 may be a conductive cable or any other suitable connector. The connector 142 may connect to the downlead 4 or the earth electrode 100 or both with a conductive, spring-loaded crocodile clip 144, or in any other suitable manner.

The liquid distribution system 104 may be connected to the bladders 124 as described above. Liquid may be provided to the bladders 124 so that it reduces the resistance between the downleads 4 and reinforcing rods 2 as described above. Liquid is preferably supplied to the bladders 124 with a pump 126, however water may be supplied in any suitable manner. Alternatively, the bladders 124 may be filled before raising them up the pole 1.

Referring now to Figs. 11 and 12, a further embodiment of a securing device 5 to secure a downlead 4 to a concrete pole 1 is shown. The securing device 5 is a conductive elongate member

6 with attachments that 1) hold the device 5 in a hole 3 in the pole 1, and 2) clamp the downlead 4 to the surface of the concrete pole 1. The securing device is preferably made from an electrically conductive pipe 6, such as one made from copper. The pipe 6 may be open or have sealed ends.

However, other conductive elongate members made from other appropriate materials could be used. For example, the elongate member could be a solid conductive rod. Further, at one end of the elongate member of this embodiment there may be a suitable handle, for example, a ring or L-shaped handle to allow for easy removal of the device from the hole in the pole, should the spring retain the elongate member tighdy in the hole.

Attached to a first end 9 of the pipe 6 is a spring member 7. The first end 11 of the spring member 7 is preferably attached by screws, a weld or similar fastening means to the first end 9. The spring member 7 is elongate and runs along a substantial length of the pipe 6. Nearer to the other end 10 of the pipe 6 the elongate spring 7 has a curve 12 and the other end 13 of the spring member is left free. In use when a pressure is placed at A on the curve 12 the spring member 7 flexes towards and against the pipe, effectively reducing the overall width of the pipe plus spring member. When the force is released the spring member will return to its original position and the pipe plus spring is tighdy held within the hole by die returning upward force of die spring. The spring member is preferably made from a conductive material, such as a phosphor bronze strip, a stainless steel strip or similar.

Also attached to the first end 9 of the pipe 6 is a conductive clamp 14. The clamp is a clip- in type that in use clamps over die earthing downlead 4. The clamp 14 is preferably attached by screws, a weld or similar fastening means to the first end 9. The clamp 14 in this embodiment is attached to the pipe 6 at a position that^, is perpendicular to the spring member 7 but other appropriate positions may be used, such as on the opposite side of the pipe to the spring member. The clamp 14 is also made from a conductive material, such as a copper strip, that has been shaped into an appropriate shape to allow for clamping of the earthing downlead 4 against the surface of the concrete pole 1. In use, as shown in Figure 11, the securing device 5 is inserted into at least_, one but preferably more holes 3 formed in the concrete pole. The spring member 7 pushes against the internal walls of the hole and holds^' the securing device 5 in the hole 3 and causes the clamp 14 to clamp about the downlead 4 and hold the downlead 4 against the surface of the concrete.

Thus, the securing device in use makes a good electrical contact with the earthing downlead and with the concrete surface inside of hole on pole. Further a good contact is also made between the earthing downlead and the pole surface. Finally, the earthing downlead that runs down the pole to the soil (earth) is secured to the pole.

Figure 13 shows another embodiment of a securing device 20 of the present invention.

This securing device 20 is very similar to the securing device of Figure 12 except the elongate member is a pipe 21 formed in an L-shape. The longer part 22 of the L is preferably sealed at its distal end 23 and this longer part 22 is the part that is inserted in use into a hole 3 on a pole 1. The shorter end 24 of the L is open and turned up. In this form a liquid receptacle 25, such as a botde

■ or other appropriate receptacle, is inserted into the open pipe 21 upside-down.

The liquid held by the receptacle 25 may be water, an electrolytic solution or other appropriate liquid that will provide an ionic solution inside the concrete pole.

The securing device 20 has a spring member 7 and clamp 14 substantially similar to the first embodiment of Figure 12.

Alongside the bottom of longer part 22 of the L shaped pipe 21 there are one or more small holes 5, which slowly release liquid, in use, from the liquid receptacle 25. The rate of liquid discharge is controlled by the size of diese holes 5 and by a small hole on the liquid receptacle to allow for an air intake and transfer of the liquid to the pipe 21.

The securing device 20 of the second embodiment of the present invention is believed to ^■ provide an increased equipotential bonding between the downlead 4 and concrete pole.

In use, as shown in Figure 14, there are two securing devices 20 with liquid receptacles 25. The securing device distributes liquid inside each of the holes 3, which creates an ionic solution in the concrete, thus creating a low resistance path between the concrete pole and the steel reinforcement bars. As with the securing device of Figure 12 the securing device 20 makes a good electrical contact with the earthing downlead and with the concrete surface inside of hole on pole. It also makes a good contact between the earth downlead and the pole surface and secures the earthing downlead to the pole. Furthermore, the securing device 20 of the second embodiment distributes liquid to internal parts of pole and improves the conductivity between the earthing downlead and the reinforcement bars by creating an ionic electrical path, therefore achieving a good equipotential bonding of all metallic parts on a pole and around a pole.

Both the securing devices 5, 20 described above are capable of being adjusted to different hole sizes. Further, the number of devices installed on any particular pole will depend on weather conditions, the type of concrete or the voltage level of the overhead lines. As an example, two securing devices of the first or second embodiments are likely to be sufficient to secure an earthing lead to a pole and provide a good equipotential bond. However, any number securing devices may be used.

Auxiliary securing devices may be' used with either of the above embodiments of the securing device of the present invention. The auxiliary devices have the purpose of creating a good surface contact between the earthing downlead and concrete, and are preferably used when for any reason the securing devices of the first two embodiments can not be inserted into a hole on a pole. For example, when a hole is already being used to strap something else to the pole and the securing devices of Figures 3 or 4 cannot be inserted into the hole.

A first auxiliary device 30 is shown in Figure- 15. It is a bracket made of conductive material. The bracket 31 has a wedge shaped recess 32 in it, which in use, the downlead fits into.

In use, the legs 33, 34 of the bracket 31 are strapped to the concrete pole behind a cable strap such that the conductive bracket holds the downlead 4 against the surface of the concrete pole. One of these first auxiliary devices 30 is shown in use in Figure 18. This first auxiliary device 30 provides a good surface contact between the earthing downlead and the pole and supports the earthing downlead.

A second auxiliary device is shown in Figure 16. This auxiliary device 35 is preferably made of conductive wire and has a type of spring action. The device 35 is a loop of conductive wire, preferably of a substantial diameter. The device 35 has a loop 36 and legs 37, 38. The loop is maintained by a tie, crimp or lug 39 and the leg^'s 37, 38 of the device extend below the crimp. This auxiliary device 35 may be adjusted to fit differing pole hole diameters by changing the width or diameter of the wire making up the device or changing the position of the crimp 39.

In use, this second auxiliary device 35 may be used if a hole on pole is taken by a cable strap. The device 35 is fitted in use into a hole 3 in a pole 1 with each of the legs 37, 38 extending about the downlead 4. The device 35 is pushed in the hole and the downlead 4 is pushed to the apex 40 of the legs of the device 35. Due to the flexible nature of the wire legs 37, 38 when inside the hole 3 they push against the^' inside walls of the hole, providing an additional contact between the inside of the pole, the device 35 and the downlead 4.

Again this second auxiliary device 35 makes a good surface contact between the earthing downlead and the pole and support the earthing downlead. The legs 37, 38 also make an additional contact with the concrete surface inside a hole.

A third auxiliary device 41 is shown in Figure 17. This third auxiliary device 41 is effectively a clamp. The clamp 41 is made of conductive material and may be adjustable to most pole sizes. This clamp 41 may be used if there are no holes on a pole, or if there are not enough holes at any. part of pole.

The clamp 41 comprises a handle 42 attached to a T-shaped bracket 46. A spring 44 extends between the handle 42 and the T of the bracket 46. A rod 43 attached to the spring 44 at or near to the T of the bracket 46 extends through a threaded hole (not shown) in the T of the bracket 46, then ends with a disc 47. The spring 44 is preferably bolted 48 at the handle and similarly attached at the other end of the rod to the disc 47.

Preferably the spring 44 has a PVC protective tube outer 45.

In use the clamp 41 clamps around a pole and holds a downlead firmly against a pole surface, thus achieving good contact between a downlead and pole surface. It also supports the earthing downlead. In particular, one side of the T of the bracket 49 rests against the downlead 4 pushing it against the pole front surface and the rod 43 and disc 47 extend to the back surface of the pole, effectively clamping the device 41 to the pole. This third auxiliary device 41 could also successfully replace the so called "cluster mount", which is usually mounted just underneadi the work zone, and consists of a metallic chain or braided flat conductor or strap.

A cluster mount is the currently recommended "best" industry practice to achieve an equrpotential bonding. A cluster mounts reduces to some extent the fault current through a body of a lineman during a fault condition, but it has been proven by testing that it is not very effective.

A cluster mount consists of a metal chain or flat braided conductive strap that is strapped around a pole just bellow a work zone, for example, just bellow the feet of a lineman standing on a ladder. There is very poor surface contact between the chain and the concrete. The contact between the flat braided strap and the concrete is somewhat better, but it is made at one point only on the pole, and does not help at all in dry conditions. A cluster mount in general is not very practical to install because there are a lot of "thick" double poles and/or a lot of cables coming down from the top of poles that further reduces the effectiveness of this method. The chain is connected to the temporary earth at the base of pole and to the main temporary earth of the lines.

Figure 18 shows a pole 1 with a first end of a downlead 4 clamped, with appropriate clamps or fasteners 50, to the top of die pole, e.g. to the metal braces of cross-arms or similar on the pole. The downlead 4 extends down the length of the pole to the ground 51 beneath the pole. The ground end 52 of the downlead 4 is attached to an earthing rod 53 by a clamp, hook or similar 54.

When a worker wishes to ground die pole 1 , he runs the downlead 4 down the pole 1 and clamps it at each end, one to die top of the pole, e.g. to the metal braces of cross-arms or similar on the pole, and the other to the earthing rod 53 in the ground. To secure the length of the downlead 4 to die pole, he may use any of the securing devices detailed above. As shown in Figure 9, a securing device 21 (of the second embodiment) with a liquid receptacle 25 is used. Also, a bracket 30, clamp 41 and wire and loop securing device 35 are all used to secure the downlead to the surface and creates a contact between the inside of die pole to the downlead 4.

The devices described above are easy and low cost to manufacture. They provide an easy and effective solution to the problems discussed with the prior art. Finally, the devices provide an easy method for line or pole workers to create equipotential bonding on power poles. The foregoing description of the invention includes preferred forms thereof. Modifications may be made thereto without departing from the scope of the invention as defined by the accompanying claims.

Claims

1. A system for creating an equipotential along a pole comprising: a conductive downlead for fixing to and extending substantially along the length of the pole to electrically connect to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead sufficient to create an equipotential along the pole; and a liquid distribution system for supplying a liquid between the conductive downlead and the pole.

2. A system for creating an equipotential along a pole according to claim 1 comprising a second conductive downlead for fixing to and extending substantially along the length of the pole to electrically connect to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead.

3. A system for creating an equipotential along a pole according to either of claims 1 or 2 where the liquid distribution system comprises a bladder also extending substantially along the length of the pole.

4. A system for creating an equipotential along a pole according to claim 3 where a bladder is provided internally widiin the or each conductive downlead.

5. A system for creating an equipotential along a pole according to any one of claims 1 to 4 comprising at least one securing device for fixing the conductive downlead to the pole.

6. A system for creating an equipotential along a- pole according to claim 5 where the securing device is a clamp.

7. A system for creating an equipotential along a pole according to claim 6 where the clamp comprises a recess arranged to receive the conductive downlead.

8. A system for creating an equipotential along a pole according to claim 5 where the securing device comprises an elongate member made of a conductive material and capable of extending within a hole in the pole, a spring made of conductive material and attached to the elongate member and arranged to hold the elongate member in the hole, and a clamp made of conductive mateπal and attached to the elongate member to in use clamp the conductive downlead to the surface of the pole.

9. A system for creating an equipotential along a pole according to either of claims 3 or 4 or claims 5 to 8 when dependent on either of claims 3 or 4 where the liquid distribution system comprises a pump for pumping a liquid into the bladder.

10. A system for creating an equipotential along a pole according to claim 2 or any of claims 3 to 9 when dependent on claim 2 including a scissor gripping device for securing the conductive downleads near die top of the pole.

11. A method of creating an equipotential along a pole comprising the steps of:

(a) fixing a conductive downlead substantially along the length of the pole, such that the conductive downlead is electrically connected to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead sufficiendy to create an equipotential along the pole; and

(b) supplying a liquid between die conductive downlead and the pole.

12. A method of creating an equipotential along a pole according to claim 11 comprising the steps of:

(a) fixing a second conductive downlead substantially along the length of the pole, such diat the second conductive downlead is electrically connected to the pole substantially along the length of the second conductive downlead or at least at intervals along the length of the second conductive downlead sufficiendy to create an equipotential along the pole; and (b) supplying a liquid between the second conductive downlead and the pole.

13. A method of creating an equipotential along a pole according to either or claims 11 or 12 where the liquid distribution system comprises a bladder also extending substantially along the length of the pole.

14. A method of creating an equipotential along a pole according to claim 13 where a bladder is provided internally within the or each conductive downlead.

15. A method of creating an equipotential along a pole according to any one of claims 11 to 14 comprising the step of fixing the conductive downlead to the pole with a securing device.

16. A method of creating an equipotential along a pole according to claim 15 where the securing device is a clamp.

17. A method of creating an equipotential along a pole according to claim 16 where the clamp comprises a recess arranged to receive the conductive downlead.

18. A method of creating an equipotential along a pole according to claim 15 where the securing device comprises an elongate member made of a conductive material and capable of extending within a hole in the pole, a spring made of conductive material and attached to the elongate member and arranged to hold the elongate member in the hole, and a clamp made of conductive material and attached to the elongate member and which clamps the conductive downlead to the surface of the pole.

19. A method of creating an equipotential along a pole according to either of claims 13 or 14 or any of claims 15 to 18 when dependent on claim 13 or 14 comprising the step of pumping a liquid into the bladder.

20. A method of creating an equipotential along a pole according to claim 12 comprising securing the conductive downleads substantially near the top of the pole with a scissor gripping device.

21. A system for creating an equipotential along a pole comprising: a conductive downlead for fixing to and extending substantially along the length of the pole; and at least one securing device arranged to clamp and electrically connect the conductive downlead to the pole sufficient to create an equipotential along the pole.

22. A system for creating an equipotential along a pole according to claim 21 comprising a second conductive downlead for fixing to and extending substantially along the length of the pole to electrically connect to the pole substantially along the length of the conductive downlead or at least at intervals along the length of the conductive downlead.

23. A system for creating an equipotential along a pole according to either of claims 21 or 22 comprising a liquid distribution system for supplying a liquid between the conductive downlead and the pole.

24. A system for creating an equipotential along a pole according to claim 23 where the liquid distribution system comprises a bladder also extending substantially along the length of the pole.

25. A system for creating an equipotential along a pole according to claim 24 where a bladder is provided internally within the or each conductive downlead.

26. A system for creating an equipotential along a pole according to any one of claims 21 to 25 where the clamp comprises a recess arranged to receive the conductive downlead.

27. A system for creating an equipotential along a pole according to either of claims 24 or 25 where the liquid distribution system comprises a pump for pumping a liquid into the bladder.

28. A system for creating an equipotential along a pole according to claim 22 including a scissor gripping device for securing the conductive downleads substantially near the top of the pole.,

29. A method of creating an equipotential along a pole comprising the steps of:

(a) extending a conductive downlead along the length of the pole; and

30. A method of creating an equipotential along a pole according to claim 29 comprising the steps of:

(a) extending a second conductive downlead along the length of the pole; and

31. A method of creating an equipotential along a pole according to either of claims 29 or 30 comprising a liquid distribution system for supplying a liquid between the conductive downlead and the pole.

32. A method of creating an equipotential along a pole according to claim 31 where the liquid distribution system comprises a bladder also extending substantially along the length of the pole.

33. A method of creating an equipotential along a pole according to claim 32 where a bladder is provided internally within the or each conductive downlead.

34. A method of creating an equipotential along a pole according to any one of claims 29 to 33 where the clamp comprises a recess arranged to receive the conductive downlead.

35. A method of creating an equipotential along a pole according to either of claims 32 or 33 comprising the step of pumping a liquid into the bladder.

36. A method of creating an equipotential along a pole according to claim 30 including securing the conductive downleads are secured substantially near the top of the pole with a scissor gripping device.

37. A device to secure a conductive downlead to a pole by way of a hole in said pole comprising: an elongate member, made of a conductive material, capable of extending within said hole " in said pole, a spring, made of a conductive material, attached to said elongate member and holding said elongate member in said hole, and a clamp, made of a conductive material, attached to said elongate member and in use clamping said earthing lead to the surface of said pole.

38. A device to secure a conductive downlead to a pole according to claim 37 where said elongate member is a hollow pipe that is closed at one end and open at the other end.

39. A device to secure a conductive downlead to a pole according to claim 38 where said hollow pipe has a liquid receptacle attached to it and at least one aperture formed along said pipes length, such that in use when said pipe is inserted into a hole in said pole said liquid can flow from said receptacle along said pipe and out said at least one aperture to soak into said pole.

40. A method of creating an equipotential along a pole comprising the steps of: (a) running an earthing lead down a pole, (b) attaching at least one conductive securing device to at least one hole in said pole, said securing device having a elongate member, capable of extending within said hole, a spring attached to said elongate member and holding said elongate member in said hole, and a clamp attached to said elongate member that in use clamps said earthing lead to the surface of said pole, and clamping said earthing lead to an earthing rod in the ground surrounding said pole.

41. A method of creating an equipotential along a pole according to claim 40 comprising the step of a liquid receptacle to said securing device, such that in use, liquid flows into said pole creating an ionic solution in said pole and reducing the resistance of said pole.

42. A method of creating an equipotential along a pole according to either of claims 40 or 41 comprising the step of attaching one or more auxiliary securing devices to said pole to further secure said earthing lead to said pole.