WO2006034539A1 - Method and apparatus for installing electrical lines or cables - Google Patents

Abstract

An apparatus and method for upgrading the capacity of an electrical circuit for transmission of high voltage electricity, including attaching a cross member (202, 203, 204) to an existing support structure (101) for conductors (111, 112; 114, 115; 117, 118) of the electrical circuit (110); transferring each of the conductors from the existing support structure (101) to the cross member (202, 203, 204) whereby each conductor is displaced from its pre-existing position; constructing a further support structure (205) for replacement electrical conductors (211, 212, 213) required to upgrade circuit capacity; attaching the replacement conductors to the further support structure (206, 207, 208); energising the replacement conductors of the upgraded circuit; de-energising and removing the conductors (111, 112; 114, 115; 117, 118) from the cross member (202, 203, 204); and detaching the cross member from the existing support structure (101).

Description

TITLE

METHOD AND APPARATUS FOR INSTALLING ELECTRICAL LINES OR

CABLES

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Australian Provisional Patent Application No. 2004905613 filed by the present applicant for the above-titled invention on 28 September 2004.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to the installation of electrical conductors, including lines and/or cables. In particular, the invention relates to the installation of overhead lines in order to supplement or increase the capacity of existing electrical transmission or distribution systems.

Discussion of the Background Art

The transmission and distribution of electrical power may be achieved by use of electrical lines or cables which are installed in an overhead configuration or disposed underground. In the case of overhead transmission, bare electrical conductors are generally strung from poles, towers or other constructions utilising insulating supports or insulators, whereas underground cables typically include complex electrically insulated, reinforced and armoured constructions suited to the underground environment. The lines or cables are usually connected in a network to provide for transmission of electrical power from generating stations, such as thermal or hydro-electric stations, to distribution points or sub-stations. Whilst underground cables are more space efficient, the capital cost of acquisition of suitable cables and underground installation dictates that overhead lines are preferred where feasible.

The electrical load applied to transmission and distribution networks generally grows with expansion or in-fill of industrial, commercial and residential areas, placing additional demands for power flow across the electrical network. This typically requires the installation of additional electrical lines and/or the upgrading of existing lines. In the case of overhead transmission, constrained use strips of land or easements are utilised for siting poles or transmission towers in order to provide the requisite clearance for the bare conductors carried by the supporting insulators for routing the lines. However existing easements, which typically vary in width from about 20m to 70m, may already be filled with pole or tower constructions. New easements are difficult to acquire and substantial widening to accommodate additional constructions, which is required for the full length of the line route, is often either expensive or impractical due to encroachment on adjoining properties.

Although the tolerance to outages (i.e. taking a transmission circuit out of service) varies across an electrical transmission network, in general outages must be restricted to periods of good weather with relatively low load, such as overnight for residential loads or week-ends for industrial or commercial loads. Furthermore the risk of accidental loss of supply during circuit upgrade must be kept to an acceptably low level.

Electrical networks are generally structured to allow loss of service or an outage of one circuit for at least a restricted period. However, in some instances, operational constraints are such that the risk of being unable to meet the connected electrical load is too high to permit a circuit to be taken out of service for extended periods for re-building.

The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia or any other country.

SUMMARY OF THE INVENTION Object of the Invention The present invention aims to provide an alternative to present arrangements for installing or upgrading electrical lines or cables to supplement or increase the capacity of electrical transmission circuits.

Disclosure of the Invention In a first broad aspect, the invention resides in a method for upgrading the capacity of an electrical circuit for transmission of high voltage electricity, said method including the steps of: attaching a cross member to an existing support structure for conductors of the electrical circuit; transferring each of the conductors from the existing support structure to the cross member whereby each conductor is displaced from its pre-existing position; constructing a further support structure for replacement electrical conductors required to upgrade circuit capacity; attaching the replacement conductors to the further support structure; energising the replacement conductors of the upgraded circuit; de-energising and removing the conductors from the cross member; and detaching the cross member from the existing support structure.

Preferably the existing support includes a pole or tower structure that includes cross-arms for supporting aerial conductors comprising the electrical circuit. Most preferably the electrical circuit is a multi-phase circuit and a bundle of aerial conductors corresponds to each phase of the circuit, for example a bundle for each of A phase, B phase and C phase.

Suitably pluralities of cross members are attached to the existing support structure, independently of the cross-arms. In the example of a three (3) phase circuit, there will be provided three (3) cross-arms, typically requiring a corresponding number of cross members. Most desirably, phase conductor bundles for two circuits may be attached at opposite ends of respective cross members.

In preference, the cross members are arranged such that the conductors may be transferred in an energised condition and whereby the displacement of the conductors is not beyond the permissible clearance within an easement wherein the support structure is sited.

Preferably the conductors in a phase, whether bundled or otherwise, are transferred together with a supporting insulator. For example, each phase (A, B, C) of a circuit may include an insulator supporting a bundle of aerial conductors for a respective phase. The step of constructing the further support structure, may involve constructing a replacement pole or replacement tower adjacent said existing support structure. The replacement pole or tower may be constructed either in alignment with the existing support structure, or laterally offset from the existing support structure. Alternatively, the step of constructing the further support structure may involve constructing poles or towers substantially equidistant between existing support structures. If required, the step of constructing the further support structure may involve constructing poles or towers at a different longitudinal spacing to the existing support structures.

Further, the step of constructing the further support structure may involve the precedent step of dismantling existing cross-arms and then strengthening the existing support structure and fixing replacement cross-arms at an elevated position on the strengthened support structure. If required, the existing support structure may be dismantled, either in part or entirely. Where the existing support structure includes an upright tower or pole, the step of dismantling the existing support structure suitably includes removing the cross-arms and removing said tower or pole. Most preferably in the case of a pre¬ existing tower, the step of dismantling involves working from the top down and sending structural elements of each tower down through a central void within the tower.

In a variation of the first aspect of the invention, the step of attaching a cross member to the existing support member further includes extending the existing support structures upwardly in order to provide a single wide span cross member. Suitably a further step may involve attaching a conductor holding structure adjacent to opposite distal ends of the cross member; wherein the conductor holding structure depends from respective distal ends of the cross member and includes a plurality of conductor cradles for existing conductors, which cradles are interposed by insulator strings. The cross member preferably has a relatively span which provides predetermined lateral clearance from said replacement conductors. The lower free ends of the conductor holding structure are anchored, suitably to the ground, in order to stabilise said holding structure, especially during conductor transfer.

In a second broad aspect of the invention there is provided a method for upgrading the capacity of an electrical circuit for transmission of high voltage electricity, said method including the steps of: constructing a series of replacement support structures for replacement electrical conductors required to upgrade circuit capacity, each replacement support structure sited intermediate to existing support structures for conductors of the electrical circuit; displacing freely suspended portions of the conductors intermediate said existing support structures and attaching said conductors to lateral support arms provided by the replacement support structures; attaching temporary lateral support members to the existing support structure; stringing the replacement conductors between the temporary lateral support members and further lateral support arms provided by the replacement support structures; de-energising conductors of the existing electrical circuit and energising the replacement conductors; dismantling the conductors of the existing electrical circuit from the existing support structures; transferring the replacement conductors from the temporary lateral support members to lateral support arms of the replacement support structure; and dismantling the temporary lateral support members and existing support structures. In one arrangement the replacement support structure is longitudinally aligned with the existing support structures, such as towers. In an alternate arrangement, the replacement support structures are laterally displaced from the existing support structures.

Suitably the replacement support structures include modular poles to which are attached insulating lateral support arms. If required, two modular poles are sited intermediate the existing support structures, such as towers, wherein the modular poles are laterally displaced in opposite directions.

The step of displacing the freely suspended portions of conductors may be affected by an insulating rope or net provided over lateral end portions of the temporary lateral support members. Alternatively, the step of displacing conductors may be affected by attachment of a cable having an insulator at a distal attachment end, which cable is then anchored to the ground or to a moveable anchoring means, such as a truck or a crane. In locations where adjacent conductors cross vertically and/or horizontally in relation to one another, insulated separators may be provided between the adjacent conductors.

In a third broad aspect of the invention, there is provided apparatus for affecting an upgrade to the capacity of an electrical circuit for transmission of high voltage electricity, said apparatus including: a plurality of replacement support structures, each support structure including lateral support arms for replacement conductors required to upgrade the electrical circuit, said lateral support arms arranged for siting the replacement support structures either adjacent to or intermediate, the existing support structures; at least one temporary lateral support members for removable attachment to the existing support structure; and holding means for effecting temporary displacement of freely suspended portions of conductors during stringing of the replacement conductors and removal of the existing conductors from the existing support structure.

Suitably the replacement support structures include a modular pole having laterally extending insulating arms for attachment of said conductors. If required, the insulating arms are able to be elevated relative to the pole. The temporary lateral support members are preferably insulators adapted to receive replacement conductors and/or the holding means.

Alternatively, said at least one temporary lateral support member includes a wide span cross member having conductor holding structures suspended from opposite distal ends. The holding means is desirably selected from the group including an insulating net, insulating rope assembly, a cable having an insulator at a distal end and a conductor holding structure including a plurality of conductor cradles interposed by insulator strings.

BRIEF DETAILS OF THE DRAWINGS

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings illustrate preferred embodiments of the invention, and wherein: FIG. 1 is a front elevational view of an existing tower supporting groups of electrical conductors for power transmission;

FIG. 2 is a plan view of the existing towers depicting the circuits comprised by the groups of conductors disposed along an easement; FIG. 3 is a front elevational view of the tower after installation of a supplementary cross member of a first embodiment of the present invention;

FIG. 4 is a plan view of the towers with supplementary cross member of the first embodiment;

FIG. 5 is a front elevational view of the tower with supplementary cross member supporting the conductor groups;

FIG. 6 is a plan view of the towers with supplementary cross member supporting the conductor groups;

FIG. 7 is a front elevational view of the tower with supplementary cross member after dismantling of existing cross-arms; FIG. 8 is a plan view of the towers with supplementary cross member after dismantling of existing cross-arms;

FIG. 9 is a front elevational view of a replacement pole of a first embodiment positioned adjacent the existing tower;

FIG. 10 is a plan view of the replacement poles of a first embodiment positioned adjacent the existing tower;

FIG. 11 is a front elevational view of the replacement pole supporting replacement conductors;

FIG. 12 is a plan view of the replacement poles supporting replacement conductors; FIG. 13 is a front elevational view of the replacement pole supporting the replacement conductors after switching on and de-energising the existing conductors on the tower;

FIG. 14 is a plan view of the replacement pole supporting the replacement conductors after switching on and de-energising the existing conductors; FIG. 15 is a front elevational view depicting the tower after removal of de- energised conductors from the supplementary cross members;

FIG. 16 is a plan view depicting the tower after removal of de-energised conductors from the supplementary cross members; FIG. 17 is a front elevational view of the tower after removal of the supplementary cross members;

FIG. 18 is a plan view of the tower after removal of the supplementary cross members; FIG. 19 is a front elevational view of the replacement pole after disassembly of the towers;

FIG. 20 is a plan view of the replacement pole after disassembly of the towers;

FIG. 21 is a front elevational view of a strengthened tower with new cross- arms of a second embodiment of the invention; FIG. 22 is a front elevational view of the strengthened tower with new cross- arms supporting the replacement conductor groups;

FIG. 23 is a front elevational view of the strengthened tower with supplementary cross member after switching power from the existing circuits to the replacement circuits; FIG. 24 is a front elevational view of the strengthened tower of the second embodiment with existing conductor sun-assemblies removed form the cross members;

FIG. 25 is a front elevational view of the strengthened tower supporting the replacement conductor sub-assemblies; FIG. 26 is a front elevational view of a further existing tower supporting groups of electrical conductors for power transmission;

FIG. 27 is a plan view of the further existing towers depicting the circuits comprised by the groups of conductors disposed along an easement;

FIG. 28 is a front elevational view showing a modular replacement pole erected in an laterally offset position in accordance with a third embodiment of the present invention;

FIG. 29 is a plan view of the arrangement of original towers and replacement poles of the third embodiment;

FIG 30 is a front elevational view showing lateral displacement of the freely suspended conductor portions of a second circuit for retention by lateral insulators of the replacement poles;

FIG. 31 is a plan view showing lateral displacement of conductors of the first and second circuits that are retained by the intermediate replacement poles; FIG. 32 is a front elevational view showing the construction of a further modular pole in lateral alignment with the replacementpole of FIG. 29;

FIG. 33 is a plan view of the further modular pole constructed in alignment with a respective replacement pole; FIG. 34 is a front elevational view of the modular poles that bracket the original tower to which is added temporary lateral insulating members;

FIG. 35 is a plan view of the modular poles and the temporary lateral insulating members added to the original towers;

FIG. 36 is a front elevational view showing the stringing of conductors of a new circuit between lateral arms of the further modular poles and temporary lateral insulating members added to the original towers;

FIG. 37 is a plan view of the conductors of a new circuit strung between lateral arms of the further modular poles and temporary lateral insulating members added to the original towers; FIG. 38 is a front elevational view depicting the energisation of the new circuit of FIGs 36 and 37;

FIG. 39 is a plan view depicting the energisation of the new circuit of FIGs 36 and 37;

FIG. 40 is a front elevational view showing the dismantling of the second existing circuit from the cross-arms of the tower and temporary retainers on the first modular poles;

FIG. 41 is a plan view showing the dismantling of the second circuit from the towers and the first modular poles;

FIG. 42 is a front elevational view showing the removal portions of the cross- arms and depending insulators from the tower which formerly carried conductors of the second circuit;

FIG. 43 is a plan view showing removal from the original towers of the cross- arm portions which formerly carried the second circuit;

FIG. 44 is a front elevational view depicting the elevation of inwardly extending insulating arms on the first modular poles;

FIG. 45 is a front elevational view of conductors of a further new circuit strung between the elevated inwardly extending insulating arms of the modular poles and the temporary lateral insulating members on the original towers; FIG. 46 is a plan view of the stringing of the conductors for the further new circuit between the elevated inwardly extending insulating arms and the temporary lateral insulating members;

Fig 47 is a front elevational view depicting the energisation of conductors of the further new circuit of FIGs 45 and 46;

FIG 48 is a plan view depicting the energisation of conductors of the further new circuit of FIGs 45 and 46;

FIG. 49 is a front elevational view depicting dismantling of the first circuit from the original towers and temporary restrain on modular poles; FIG. 50 is a plan view depicting dismantling of conductors from the first circuit;

FIG. 51 is a front elevational view depicting removal of the cross-arms from the towers and lateral arms from the modular poles;

FIG. 52 is a plan view depicting removal of the cross-arms from the towers and lateral arms from the modular poles; FIG. 53 is a front elevational view showing the holding of the conductors to allow dismantling of the existing towers;

FIG. 54 is a plan view showing the holding of the top sets conductors to allow dismantling of the existing towers;

FIG. 55 is a front elevational view showing dismantling of the top part of the existing towers;

FIG. 56 is a plan view showing dismantling of the top part of the existing towers;

FIG. 57 is a front elevational view showing the re-positioning of top sets of conductors; FIG. 58 is a front elevational view showing the holding of lower set of conductors;

FIG. 59 is a plan view depicting the re-positioning of top sets of conductors and the holding of lower set of conductors;

FIG. 60 is a front elevational view showing the removal of the base of the original tower whilst lower set of conductors are held;

FIG. 61 is a plan view depicting deconstruction of the tower base and re¬ positioning of the lower set of conductors; FIG. 62 is a front elevational view of the re-positioning of the lower set of conductors;

FIG. 63 is a front elevational view of all conductors in final relaxed positions suspended from the replacement poles; FIG. 64 is a plan view of all conductors in final relaxed positions suspended from the replacement poles;

FIG. 65 is a front elevational view of a pole of a replacement support structure of a fourth embodiment constructed mid-span in alignment with the original tower;

FIG. 66 is a plan view of the replacement pole of the fourth embodiment; FIG. 67 is a front elevational view depicting placement of temporary lateral insulating members on the replacement pole;

FIG. 68 is a plan view of the placement of temporary lateral insulating members on the pole;

FIG. 69 is a front elevational view depicting placement of a push insulating rope or net on the replacement pole;

FIG. 70 is a plan view of the placement of a push insulating rope or net on the replacement pole;

FIG. 71 is a front elevational view depicting outward displacement of freely hanging portions of existing conductors; FIG. 72 is a plan view of the outward displacement of freely hanging portions of existing conductors;

FIG. 73 is a front elevational view depicting attachment of insulating lateral arms on the replacement poles;

FIG. 74 is a plan view of the attachment of insulating lateral arms on the replacement poles;

FIG. 75 is a front elevational view depicting attachment of further temporary insulating cross members and a further insulating rope or net on the existing support tower;

FIG. 76 is a plan view of the attachment of further temporary insulating cross members and a further insulating rope or net on the existing support tower;

FIG. 77 is a front elevational view depicting stringing of new conductors at replacement poles and further insulting net; FIG. 78 is a plan view of the stringing of new conductors at replacement poles and further insulting net;

FIG. 79 is a front elevational view depicting energisation of the new conductors; FIG. 80 is a plan view of the energisation of the new conductors;

FIG. 81 is a front elevational view depicting removal of existing conductors and cross-arms from original towers;

FIG. 82 is a plan view of the removal of existing conductors and cross-arms from original towers; FIG. 83 is a front elevational view depicting removal of the temporary lateral insulating members and insulating net from the new poles;

FIG. 84 is a plan view of the removal of the temporary lateral insulating members and insulating net from the new poles;

FIG. 85 is a front elevational view depicting removal of the further temporary lateral insulating members and further insulating net from the existing towers;

FIG. 86 is a plan view of the removal of the further temporary lateral insulating members and further insulating net from the existing towers;

FIG. 87 is a front elevational view depicting dismantling of the original tower;

FIG. 88 is a plan view of the dismantling of the original tower; FIG. 89 is a plan view of existing towers supporting conductor bundles of circuits for transmission of high voltage electricity;

FIG. 90 is a front elevational view of the placement of a cross member on an existing tower in accordance with an upgrade method of a fifth embodiment of the invention; FIG. 91 is a plan view of the placement of cross members on the existing towers;

FIG. 92 is a front elevational view of conductor holding structures suspended from a cross member on an existing tower;

FIG. 93 is a plan view of the conductor holding structures suspended from a cross member on existing towers;

FIG. 94 is a front elevational view of the conductor holding structures suspended from a cross member after transfer of conductors from the existing tower; FIG. 95 is a plan view of the conductor holding structures suspended from a cross member after transfer of conductors from existing towers to cradles;

FIG. 96 is a front elevational view of the conductor holding structure showing the deconstruction of an existing tower; FIG. 97 is a plan view of the conductor holding structures suspended from a cross members together with intermediate conductor stabilising cables;

FIG. 98 is a front elevational view of the conductor holding structure showing the construction of a new modular pole;

FIG. 99 is a plan view of the conductor holding structures showing the construction of new modular poles;

FIG. 100 is a plan view of the conductor holding structures showing replacement conductors strung on the new modular poles;

FIG. 101 is a front elevational view depicting energisation of replacement circuits and de-energisation of existing conductors in the cradles; FIG. 102 is a plan view depicting energisation of replacement circuits and de- energisation of existing conductors in the cradles;

FIG. 103 is a front elevational view of the removal of the cross member and depending conductor holding structures from existing towers;

FIG. 104 is a plan view of the removal of cross members and depending conductor holding structures from existing towers;

FIG. 105 is a front elevational view showing the removal of the existing towers and remaining new modular pole; and

FIG. 106 is a plan view showing the removal of the existing towers and remaining new modular poles.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In FIGs 1 and 2 there is depicted an existing electrical power transmission system 100 which requires its load carrying capacity to be upgraded. The system

100 includes a plurality of support structures sited along the route or path of aerial conductors. Each support structure comprises an upright tower 101 having three (3) cross-arms 102, 103, 104 attached at different heights on the tower. Towers 101 are disposed at predetermined distances or spans along an easement 150 in order to provide the necessary clearance for current carrying conductors from adjacent objects. Easements are typically 40m wide in the case of 132 kV circuits and 60m wide in the case of 275kV circuits.

The transmission system 100 shown here includes two (2) circuits 110, 120 which each include three (3) phases A, B, C associated with respective cross-arms on the tower 101. Thus a first cross-arm 102 is associated with phase A, a second cross-arm 103 is associated with phase B and a third cross-arm 104 is associated with phase C. In turn each of the A, B and C phases includes a bundle of conductors, in the present case a pair of conductors.

Thus phase A of the first circuit 110 includes conductors 111 , 112 supported by an insulator 113; phase B includes conductors 114 115 supported by an insulator 116; and phase C includes conductors 117, 118 supported by an insulator 119. Turning to the second circuit 120, phase A includes conductors 121 , 122 supported by an insulator 123; phase B includes conductors 124 125 supported by an insulator 126; and phase C includes conductors 127, 128 supported by an insulator 129. For ease of reference in relation to the present embodiment, the subassemblies of phase conductor bundles and insulators will be indicated as 110A, 110B and 110C for the first circuit 110; and similarly 120A, 120B and 120C for the second circuit 120. It will be appreciated that in other arrangements the phases of different circuits might not necessarily correspond to the cross-arms of the tower 101 , as shown for example in FIGs 27 and 27.

In FIGs 3 and 4 there is shown the first stage or step in upgrading the electrical transmission circuits 110, 120 carried by tower 101 of a first embodiment which involves attaching cross members 202, 203, 204 to the tower adjacent to the existing cross-arms 102, 103, 104. The cross members, each suitably constructed of structural steel, are attached to the tower separately or independently of a respective cross-arm and supported by stays 201. In the present embodiment, the cross members 202, 203, 204 extend laterally outwardly beyond the ends of the existing cross-arms.

In FIGs 5 and 6 there is shown the second upgrade stage wherein each of the phases of the existing circuits are moved laterally outwardly from ends of existing cross-arms 102, 103, 104 to the cross members 202, 203, 204; ie. phases 110A and 120A are transferred from cross-arm 102 to cross member 202, phases 110B and 120B are transferred from cross-arm 103 to cross member 203, and phases 110C and 120C are transferred from cross-arm 104 to cross member 204. Conveniently for each phase a pair of bare conductors 117, 118 and a supporting insulator 119 are moved together as a sub-assembly, as in the case of phase 110C. Where possible, the phase sub-assemblies are transferred whilst still in an energised state whereby lifting from above utilising the supporting insulator has particular advantages.

The third upgrade stage is depicted in FIGs 7 and 8 wherein the existing cross-arms 102, 103, 104 are dismantled from the towers 101 , leaving the cross members 202, 203, 204 in place carrying the two circuits 110, 120. FIGs 9 and 10- depict the fourth stage, wherein replacement support structures, here in the form of modular poles 205 with insulating cross-arms 206, 207, 208 are erected adjacent to the original or existing towers 101. It will be appreciated that in cases where the line voltage is being substantially increased, eg. from 132 kV to 275 kV, that some easement widening may be required. Alternatively, the longitudinal spacing of the replacement support structures may be reduced in order to reduce the span of conductors and/or to remain consistent with electromagnetic field requirements. This may be contrasted with an upgrade involving a modest increase in line voltage, for example, from 11OkV to 132 kV.

Next replacement conductor bundles 211 , 212, 213 for a first replacement circuit 210 and conductor bundles 221 , 222, 223 for a second replacement circuit 220 are strung in an un-energised state from respective ends of the first, second and third replacement cross-arms 206, 207, 208 as depicted in FIGs 11 and 12. It is noted that where insufficient clearance exists between conductors of the existing circuit and replacement circuit, insulating standoffs or spacers 215, 225 may be provided mid¬ way between towers 101 and between modular poles 205 in order to address the risk of conductor clashes in high wind conditions.

Once the replacement circuits 210, 220 are appropriately connected, the existing circuits 110, 120 are de-energised and the replacement circuits energised as depicted in FlG. 13, suitably by switching load from the existing circuits to the replacement circuits in turn. The next stage is to remove the now de-energised pre-existing conductors of circuits 110, 120 and insulator sub-assemblies from the cross members of the towers 101. This leaves just the energised conducts of replacement circuits 210, 220 supported by the modular poles 205, as depicted in FIGs 14 and 15. The cross members 202, 203, 204 may then be removed from the towers 101 as shown in FIGs 16 and 17, for re-use at a later time. Finally the towers 101 may be removed from the easement as depicted in FIGs 18 and 19, suitably by working from the top down and sending structural elements of each tower down through the unobstructed central portion or void within the tower.

In a second embodiment of the invention, stages one to three proceed as described above in relation to FIGs 3 to 8 showing stages of the first embodiment. The existing conductor assemblies 110A, 110B, 110C of the first circuit 110 and existing conductor assemblies 120A, 120B, 120C of the second circuit 120 are displaced outwardly to respective ends of temporary cross members. The temporary cross members 302, 303, 304 are attached to the towers 101 , independently of existing cross-arms, to provide the desired displacement of the conductor assemblies. The second embodiment diverges at the fourth stage wherein tower 101 is strengthened and heightened to provide a modified tower 301 as required to carry higher voltage transmission circuits, such as in an upgrade from 275 kV to 350 kV. As shown in FIGs 20 and 21 , the strengthening includes the addition of larger and stronger replacement cross-arms 306, 307, 308 fixed at a position elevated further up the tower from the position of the pre-existing cross-arms 102, 103, 104, as shown in FIG. 1.

Next replacement conductor bundles 311 , 312, 313 carried by respective insulators 314, 315, 316 for a first replacement circuit 310 and conductor bundles 321 , 322, 323 carried by respective insulators 324, 325, 326 for a second replacement circuit 320 are strung from the replacement cross-arms 306, 307, 308 in an un-energised state as depicted in FIG. 22.

Once the replacement circuits 310, 320 are appropriately connected, the existing circuits 110, 120 are de-energised and the replacement circuits energised as depicted in FIG. 23, suitably by switching load from the existing circuits 110, 120 to the replacement circuits 310, 320 in turn.

The next stage is to remove the now de-energised pre-existing conductor and insulator sub-assemblies 110A/120A, 11 OB/12OB, 110C/120C from the cross members 302, 303, 304 of the towers 301 , as depicted in FIG. 24. The temporary cross members 302, 303, 304 may then be removed from the towers 301 as shown in FIG 25, for re-use at a later time.

In a third embodiment of the invention, replacement support assemblies 400 include modular poles 401 that are disposed about mid-way between the towers 101 of an existing support structure 100'. The original positions of conductors of the pre¬ existing circuits 110, 120 are depicted in FIGs 26 and 27. The modular poles have insulating lateral support arms 402, 403, 404 carrying conductor bundles and insulators for two (2) high voltage circuits 110 [1], 120 [2]. The arrangement of the third embodiment allows the existing conductor bundles 111 , 112, 113, for example of the first circuit 110 to be displaced from their freely suspended positions (indicated in dashed outline) in a common lateral direction, as is apparent from the plan views in FIGs 27, 29 and 31.

The conductor bundles 111 , 112, 113 that are displaced in the first step depicted in FIGs 28 and 29 are retained by respective insulating lateral support arms 402, 403, 404 provided on one side of each modular pole 401. In the second step depicted in FIGs 30 and 31 , conductor bundles 121 , 122, 123 of the second circuit 120 are taken from their freely suspended position mid-way between the tower cross- arms and retained by respective insulating lateral support arms 407, 406, 408 provided on an opposite side of the intermediate modular poles 401.

In step three (3), a second array 410 of modular poles is located in the easement, with each pole 411 located substantially in lateral alignment with the first array of modular poles of the replacement support assembly 400. The poles include lateral insulating support arms 412, 413, 414 extending inwardly of the easement, as depicted in FIGs 32 and 33. In step four (4), three temporary lateral insulating members 421 , 422, 423, which arms approximately 6m in length in the embodiment and extending towards the second array of modular poles 411 , are attached to the original tower 101 as depicted in FIGs 34 and 35. These temporary lateral insulating members are provided for supporting higher capacity conductors (not shown) for upgraded circuits three [3] and four [4], as will be described further below.

Replacement conductor bundles 131 , 132, 133 for an upgraded circuit 130 [3] are then strung in step five (5) from the lateral insulating members to the lateral insulating supporting arms to a further lateral insulating member and so on, i.e. conductors 131 are strung between members 421 and arms 412, conductors 132 are strung between members 422 and arms 413, and conductors 133 are strung between members 423 and arms 414; particularly in order to maintain necessary clearance from the conductor bundles of the second circuit 120 [2] as depicted in FIGs 36 and 37.

Subsequently in step six (6), the second circuit 120 is de-energised and the third circuit 130 having upgraded capacity is energised as represented in FIGs 38 and 39. In step seven (7), the conductors from the second circuit 120 [2] are dismantled from insulating arms 406, 407, 408 disposed on the inward side of the modular poles 401 and from respective portions 102.2, 103.2, 104.2 of the cross- arms on the pre-original towers 101 , as depicted in FIGs 40 and 41. This is followed in step eight (8) by the removal from the original towers of those portions of the cross-arms and any depending insulators 124, 125, 126 which formerly carried conductors of the second circuit 120, see FIGs 42 and 43. In step nine (9), the inward extending insulating support arms 406, 407, 408 are raised to respective elevated positions on the modular poles 401 , as depicted in FIG. 44. It will be appreciated that the elevated positions generally correspond to the positions of the lateral support arms 412, 413, 414 on the further modular poles 411 , presently carrying conductors of the third circuit 130 of enhanced capacity. Step ten (10) then involves the stringing of upgraded capacity conductors 141 ,

142, 143 for a fourth circuit 140 [4] between the further lateral insulating members 421 , 422, 423 on the original towers 101 and the insulating lateral support arms 407, 406, 408 of the first modular poles 401 , as shown in FIGs 45 and 46. Whilst in step eleven (11), the fourth circuit is depicted as being energised and the first circuit [1] is depicted as being de-energised in FlGs 47 and 48. Subsequently the conductors of the first circuit are dismantled from the original tower 101 and the outer lateral insulators 402, 403, 404 of the modular poles 401 in step twelve (12), as shown in FIGs 49 and 50. Step (13) then involves the dismantling of the remaining cross-arm portions 102.1 , 103.1 , 104.1 from the original tower 101 and also the outer lateral insulators 402, 403, 404 of the modular poles 401 , which previously supported conductors of the first circuit, as depicted in FIGs 51 and 52.

Step fourteen (14), which involves holding the conductors laterally in order to transition each from a position suspended from the lateral insulating members 421 , 422, 423 on the original towers 101 to a freely suspended position from insulating arms on the respective modular poles 401 , 411 , is split into a number of subsidiary steps: 14A, 14B, 14C etc., as described below.

In step 14A a holding means, which here includes a truck or crane 450, for anchoring a number of holding cables 451 , 452, 453, 454 each cable having an insulator at a distal end. The insulated distal ends of the cables are attached to the conductors 141 , 142 and conductors 131 , 132 suspended from the top two lateral insulating members 421 , 422, as depicted in FIGs 53 and 54. This allows the conductors of the fourth circuit 140 and of the third circuit 130 to be released from the lateral insulating members enabling a top part of the original tower 101 to be deconstructed in step 14B, as depicted in FIGs 55 and 56.

In step 14C, the holding cables are slowly fed out allowing the conductors formerly attached to the top two insulating members to relax into a freely suspended position as depicted in FIGs 57 and in dotted outline in FIG. 59. Subsequently in step 14D, the holding cables 455, 456 are attached to the lower conductors 133, 143, as depicted in FIGs 58 and 59. This allows the remaining insulating support member 423 and the base of the original tower 101 B to be deconstructed in step 14E whilst the lower cables 133, 143 are held by the cables, see FIGs 60 and 61.

In step 14D, the holding cables are again fed out slowly allowing the lower conductors 133, 143 to relax into a freely suspended position, as depicted in FIG. 62. Finally in step fifteen (15), the holding cables and associated insulators are removed from the lower conductors, as depicted in FIGs 63 and 64, whereby the conductors 131 , 132, 133 of the third upgraded circuit 130 are suspended only from the insulating lateral arms of pole 411 forming support assembly 410, whilst the conductors 141 , 142, 143 of the fourth upgraded circuit are suspended only from the insulating lateral arms of pole 401 forming support assembly 400.

In a fourth embodiment of the invention, the poles of a replacement support assembly 500 are disposed approximately mid-span and in longitudinal alignment between original towers 101 , whereby the existing conductors are displaced in opposite lateral directions, ie. conductor groups of a first circuit 110 are displaced in an opposite direction to conductor groups of a second circuit 120.

In step one (1) a modular pole 501 is constructed mid-span between existing towers 101 , as shown in FIGs 65 and 66. In step two (2), temporary lateral insulating members 502, 503, 504 are attached to each modular pole 501 , as shown in FIGs 67 and 68. In the third step (3), insulating net or ropes 505 are disposed over outer ends of the temporary lateral insulating members and inside the conductors 111 , 112, 113 of the first circuit 110 [1] and conductors 121 , 122, 123 of the second circuit 120 [2] at their freely suspended mid-span positions, as depicted in FIGs 69 and 70.

The insulating ropes 505 are then pulled taut around the outer ends of temporary lateral insulating members 502, 503, 504 so as to displace outwardly the conductors of the first circuit 110 and of the second circuit 120 in opposite lateral directions, as shown in FIGs 71 and 72. This allows clearance for constructions of lateral insulating arms 506, 507, 508 and 509, 510, 511 on opposite sides of the modular pole 501 , as depicted in FIGs 73 and 74. In step six (6) further temporary lateral insulating members 512, 513, 514 are attached to the existing towers 101 and a further insulating rope or net 515 is pulled taut over outer ends of the further members as depicted in FIGs 75 and 76. In step seven (7), conductors having upgraded capacity for respective phases of replacement circuits 130, 140 are strung between the lateral insulating arms and outside the further insulating net 515 at the existing towers 101. In particular relation to the third circuit 130 [3], conductors 131 are strung between arms 506 and further lateral insulating members 512, conductors 132 are strung between arms 507 and further lateral insulating members 513, and conductors 133 are strung between arms 508 and further lateral insulating members 514. In relation to the fourth circuit 140 [4], conductors 141 are strung between arms 509 and further lateral insulating members 512, conductors 142 are strung between arms 510 and further lateral insulating members 513, and conductors 133 are strung between arms 511 and further lateral insulating members 514, as depicted in FIGs 77 and 78. In locations where conductors cross one another, they may be spaced from one another by insulating separators (not shown). If required, the insulating separators may be anchored to the ground.

In step eight (8), the upgraded circuits 130, 140 are energised and the existing or original circuits 110, 120 are de-energised, as depicted in FIGs 79 and 80. In step nine (9), the conductors for the original circuits 110, 120 are removed from their supports and the cross-arms 102, 103, 104 are then removed from the original towers 101. The insulating net 505 and the lateral insulating members 502, 503, 504, which formerly laterally displaced conductors of the first and second circuits, are then removed from the modular poles 501 in step ten (10) as depicted in FIGs 83 and 84. The further insulating net 515 and further insulating members 512, 513, 514 are then dismantled from the original towers 101 in step eleven (11), as depicted in FIGs 85 and 86. It will be noted that the conductors of the respective circuits are thus able to relax into their freely suspended condition at locations adjacent the original towers in this step, compare FIGs 84 and 86.

Finally, in step twelve (12), the original towers are removed from their sites in the easement, leaving only the replacement support assemblies 500 carrying upgraded conductors of the replacement circuits 130, 140, as depicted in FIGs 87 and 88.

In a fifth embodiment of the method of the invention, existing support structures in the form of towers 101 (see FIG. 89) are extended upwardly in a first stage, by an auxiliary framework 601 to which a single wide span cross member 602 is attached, as shown in FIGs 90 and 91. The cross member 602 may be constructed, in the first stage, by sequentially utilising a number of laterally outwardly extending sections 603, 604, 605; wherein each section is supported from the auxiliary framework by cables 606, 607, 608 and independently of existing cross- arms 102, 103, 104.

The last sections 605 of the cross member 602 have attachments 609 at the distal ends 610 thereof for conductor holding structures 611 , 612 which are suspended from the attachments in a second stage, as depicted in FIGs 92 and 93. The total span of the cross member 602 is determined according to the available free swinging slack of the conductors and the lateral clearance required by the replacement conductors. The conductor holding structures 611 , 612 each include a plurality of conductor cradles 613 for the conductor bundles, which cradles 613A₁ 613B, 613C provided for phase conductor bundles, are interposed by insulators to form a string 614. A lowermost free end 615 of each insulator string 614 is anchored to the ground, for example by cables 616, in order to stabilise the depending conductor holding structures 611 , 612. In a third stage, the phase conductor bundles 120A, 120B, 120C of circuit 120 are transferred to respective conductor cradles 613A, 613B, 613C of holding structure 612, as depicted in FIGs 94 and 95. A similar transfer operation is also undertaken for circuit 110. The conductor transfers may be effected with the aid of pulleys (not shown) suspended from the cross member 602 or by use of a crane, preferably whilst the existing circuits remain in an energised state. A fourth stage of the upgrade method of the present embodiment involves removal of the cross-arms from the existing towers 101 (see FIG. 96) to provide better clearances for stringing replacement conductors. If required, insulated lateral cables 617 may be employed intermediate the towers 101 to further stabilise the existing conductors, as shown in FIG. 97.

In stage five (5), a new modular pole 620 with insulating cross-arms 621 , 622, 623 is constructed adjacent to each existing tower 101 , as depicted in FIG 98 and in particular FIG. 99. Then replacement conductor bundles 631 , 641 ; 632, 642; 633, 643 for each phase of new electrical circuits 630, 640 are attached to respective insulating cross-arms 621 , 622, 623 of the modular poles 620 in stage six (6), as shown in FIGs 98 and 100. For each newly completed line section, the new circuits 630 and 640 may then be energised, at the upgraded voltage rating, and the existing circuits 110 and 120 de-energised in stage seven (7), as depicted in FIGs 101 and 102.

Stage eight (8) of the embodiment involves the removal of the de-energised conductors, the depending conductor holding structures 611 , 612 for each circuit 110, 120 and of the wide span cross member 602, as shown in FIGs 103 and 104. It will be appreciated that the conductor holding structures and supporting cross member may be re-used on a further line section requiring a capacity upgrade. In stage nine (9) the existing towers 101 are then removed (FIG. 106), so that only the new modular poles supporting the conductors of the newly upgraded circuits 630, 640 remain in the available land corridor, as seen in FIG. 105.

In a variation of the fifth embodiment (not illustrated), existing towers may be re-used where feasible. In this variation, stages 1 to 3 proceed substantially as described above. However, in stage four (4) and subsequent, the cross-arms may be reinforced or replaced with stronger components as required rather than deconstructing the existing tower. The replacement conductors can then be installed on the strengthened tower and stages 6, 7 and 8 can then proceed. No deconstruction of the existing towers is required.

In certain embodiments, the invention enables electrical distribution or transmission line construction or reconstruction where such a line already exists but requires replacement to accommodate increased power transfer. In particular, the invention allows increased power transfer by installation of higher capacity conductors, such as by replacement of single conductors by double bundle conductors or double bundle conductors by higher capacity double bundle conductors. Suitably the invention replaces existing circuits with upgraded circuits by placing the replacement conductors in a similar location to the existing ones. In some embodiments, this involves displacing (pushing or pulling) and holding existing circuits to enable the construction of new circuits and support structures and subsequently allowing for these circuits to be energized and old structures and circuits to be removed. Further embodiments allow re-use of temporary support structures and/or existing support structures suitably strengthened. It is believed that power transfer easements or corridors need only be minimally or in some cases temporarily widened, such as at corners or intersections for conductor displacement or out-swing, or for temporary holding and/or anchoring means. It is considered that the fourth embodiment provides for the maintenance of at least one circuit during construction, whilst the third embodiment allows maintenance of two circuits during construction for upgrading capacity. The configuration of the poles proposed in the embodiments is anticipated to confer improved visual performance and thus assist in engendering community acceptance of the construction process and the resulting transmission line. Whilst the embodiments are described in relation to transmission circuits, the invention may also find application in medium voltage distribution circuits in the range, for example, from 11 kV to 66 kV.

It is to be understood that the above embodiments have been provided only by way of exemplification of this invention, and that further modifications and improvements thereto, as would be apparent to persons skilled in the relevant art, are deemed to fall within the broad scope and ambit of the present invention described herein and defined in the following claims.

Claims

1. A method for upgrading the capacity of an electrical circuit for transmission of high voltage electricity, said method including the steps of: attaching a cross member to an existing support structure for conductors of the electrical circuit; transferring each of the conductors from the existing support to the cross member whereby each conductor is displaced from its pre-existing position; constructing a further support structure for replacement electrical conductors required to upgrade circuit capacity; attaching the replacement conductors to the further support structure; energising the replacement conductors of the upgraded circuit; de-energising and removing the conductors from the cross member; and detaching the cross member from the existing support structure.

2. The upgrade method of claim 1 wherein the existing support includes a pole or tower structure that includes cross-arms for supporting aerial conductors comprising the electrical circuit.

3. The upgrade method of claim 1 wherein the electrical circuit is a multi¬ phase circuit and a bundle of aerial conductors corresponds to each phase of the circuit.

4. The upgrade method of claim 1 wherein pluralities of cross members are attached to the existing support structure, independently of the cross-arms.

5. The upgrade method of claim 1 for a three (3) phase circuit, wherein a cross member is provided for the conductors supported on each of three (3) cross- arms.

6. The upgrade method of claim 1 for support structures sited in an easement, wherein the cross members are arranged such that the conductors may be transferred in an energised condition and whereby the displacement of the conductors is not beyond the permissible clearance within the easement.

7. The upgrade method of any one of claims 3 to 6 wherein the conductors in a phase, whether bundled or otherwise, are transferred together with a supporting insulator.

8. The upgrade method of claim 1 wherein the step of constructing the further support structure involves constructing a replacement pole or replacement tower adjacent to said existing support structure.

9. The upgrade method of claim 8 wherein the replacement pole or tower is constructed either in alignment with the existing support structure or laterally offset from the existing support structure.

10. The upgrade method of claim 1 the step of constructing the further support structure may involve constructing poles or towers substantially equidistant between existing support structures.

11. The upgrade method of claim 1 wherein the step of constructing the further support structure may involve constructing poles or towers at a different longitudinal spacing to the existing support structures.

12. The upgrade method of claim 1 wherein the step of constructing the further support structure involves the precedent steps of dismantling existing cross- arms, then strengthening the existing support structure and fixing replacement cross- arms at an elevated position on the strengthened support structure.

13. The upgrade method of claim 1 wherein the existing support structure is dismantled, either in part or entirely, as required.

14. The upgrade method of claim 13 for an existing support structure including an upright tower or pole, the step of dismantling the existing support structure includes removing the cross-arms and/or removing said tower or pole.

15. The upgrade method of claim 13 for an existing support structure including a pre-existing tower, the step of dismantling involves commencing from the top of the tower working down and sending structural elements of the tower down through a central void within said tower.

16. The upgrade method of. claim 1 wherein the step of attaching a cross member to the existing support member further includes extending the existing support structures upwardly in order to provide a single wide span cross member.

17. The upgrade method of claim 16 including a further step of attaching a conductor holding structure adjacent to opposite distal ends of the cross member.

18. The upgrade method of claim 17 wherein the conductor holding structure depends from respective distal ends of the cross member and includes a plurality of conductor cradles for existing conductors, which cradles are interposed by insulator strings.

19. The upgrade method of claim 17 wherein the cross member has a span which provides predetermined lateral clearance from said replacement conductors.

20. The upgrade method of claim 17 wherein lower free ends of the conductor holding structure are anchored, suitably to the ground, in order to stabilise said holding structure.

21. A method for upgrading the capacity of an electrical circuit for transmission of high voltage electricity, said method including the steps of: constructing a series of replacement support structures for replacement electrical conductors required to upgrade circuit capacity, each replacement support structure sited intermediate to existing support structures for conductors of the electrical circuit; displacing freely suspended portions of the conductors intermediate said existing support structures and attaching said conductors to lateral support arms provided by the replacement support structures; attaching temporary lateral support members to the existing support structure; stringing the replacement conductors between the temporary lateral support members and further lateral support arms provided by the replacement support structures; de-energising conductors of the existing electrical circuit and energising the replacement conductors; dismantling the conductors of the existing electrical circuit from the existing support structures; transferring the replacement conductors from the temporary lateral support members to lateral support arms of the replacement support structure; and dismantling the temporary lateral support members and existing support structures.

22. The upgrade method of claim 21 wherein the replacement support structures are constructed in longitudinal alignment with the existing support structures.

23. The upgrade method of claim 21 wherein the replacement support structures are constructed in laterally displacement from the existing support structures.

24. The upgrade method of claim 21 wherein the replacement support structures include modular poles to which are attached insulating lateral support arms.

25. The upgrade method of claim 21 wherein two modular poles are sited intermediate the existing support structures wherein the modular poles are laterally displaced in opposite directions.

26. The upgrade method of claim 21 wherein the step of displacing the freely suspended portions of conductors is affected by an insulating rope or net provided over lateral end portions of the temporary lateral support members.

27. The upgrade method of claim 21 wherein the step of displacing conductors is affected by attachment of a cable having an insulator at a distal attachment end, which cable is then anchored to the ground or to a moveable anchoring means.

28. The upgrade method of claim 21 wherein insulated separators are provided between adjacent conductors in locations where the adjacent conductors cross vertically and/or horizontally in relation to one another.

29. An apparatus for affecting an upgrade to the capacity of an electrical circuit for transmission of high voltage electricity, said apparatus including: a plurality of replacement support structures, each support structure including lateral support arms for replacement conductors required to upgrade the electrical circuit, said lateral support arms arranged for siting the replacement support structures either adjacent to or intermediate, the existing support structures; at least one temporary lateral support members for removable attachment to the existing support structure; and holding means for effecting temporary displacement of freely suspended portions of conductors during stringing of the replacement conductors and removal of the existing conductors from the existing support structure.

30. The upgrade apparatus of claim 29 wherein the replacement support structures include a modular pole having laterally extending insulating arms for attachment of said conductors.

31. The upgrade apparatus of claim 30 wherein the insulating arms are able to be elevated relative to the pole.

32. The upgrade apparatus of claim 29 wherein said at least one temporary lateral support member includes a plurality of insulators adapted to receive replacement conductors and/or the holding means.

33. The upgrade apparatus of claim 29 wherein said at least one temporary lateral support member includes a wide span cross member having conductor holding structures suspended from opposite distal ends.

34. The upgrade apparatus of claim 29 wherein the holding means is selected from the group including an insulating net, insulating rope assembly, a cable having an insulator at a distal end and a conductor holding structure including a plurality of conductor cradles interposed by insulator strings.