AU2011201591A1 - An installation unit - Google Patents

Abstract

A CABLE INSTALLATION UNIT According to the invention, there is provided an installation unit (100) including a base (102) for disposing below a predetermined surface, such as a road surface (104). Unit (100) also includes one or more sidewalls (106), which extend upwardly from base (102). Sidewalls (106) have a common upper edge (108) for defining an open top that is also disposed below surface (104). A plurality of apertures (110) is located in sidewall (106) for receiving respective conduits (not shown), such as electrical or optical cables, or fluid pipes. A locating formation (112) extends about at least a portion of upper edge (108) for selectively removably receiving a cover (114) and an extension element (116), both of which do not extend above the surface. (Figure 3) 114 126 150150 126 14 1164 116 1*-l34 12013-16 140- -130 130 -11 /140 124-,- 12 122 - --- 124 112 - -118 -112 106F, 4-106 Figure 4

Description

1 AN INSTALLATION UNIT FIELD OF THE INVENTION [0001] The present invention relates to an installation unit. [0002] Embodiments of the invention have been particularly developed as an underground cable installation unit for installing and jointing underground transmission cables. These installation units are also known as joint bays. While some embodiments will be described herein with particular reference to underground cables, it will be appreciated that the invention is not limited to such a field of use, and is applicable in broader contexts. BACKGROUND [0003] Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field. [0004] Conventional high voltage (HV) transmission lines are rated from about 33 kV to 330 kV and transmit electricity from a source, that is typically an electrical sub station, to a load or terminal, such as another sub-station. In some instances, the source is a power station. The transmission lines are arranged in a transmission cable circuit that commonly includes 3 or 6 bundled cables that extend over many kilometres between the source and the terminal. Typical lengths of the circuit are between about 5 to 10 km, although other circuits are of other lengths. Most circuits would have a length within the range of about 1 to 25 km. [0005] A transmission circuit is typically formed from a plurality of sequentially laid and serially connected cables that are generally manufactured specifically for a given project and which are delivered in-situ on cable drums for installation. The length of the cable on a cable drum is normally about 400 m to 700 m. Due to the constraint of cable length it is necessary in almost all transmission cable circuits to use a plurality of series connected cables which, in turn, requires the jointing of adjacent cables to each other to form the circuit.

2 [0006] In urban environments it is known for underground high voltage cables to be preferentially used to overhead cables. In some jurisdictions, such as in the state of New South Wales, Australia, underground transmission cables and the associated joints are typically located in roadways, as footpath areas are allocated to other utilities such as water, gas and telecommunications. [0007] An example of an existing high voltage circuit is illustrated in Figure 1, where use is made of a number of joint bays labeled JB 1/2, JB 2/3 and JB 3/4 that are used as respective sites for joining together the ends of adjacent underground cable lengths referred to as Section 1, Section 2 and Section 3. The numbers in the joint bay nomenclature used above refer to the numbers of the Sections that are jointed together in that joint bay. It will be appreciated that while only three joint bays and three sections are illustrated, in a typical project there are usually many more of each required to complete the desired circuit. [0008] During the installation of the cables and other actions required to complete a transmission circuit, the joint bays, such as JB 1/2, JB 2/3 and JB 3/4, are typically constructed sequentially or successively, which provides protection for the respective cable joints during and after installation, and allows selective access for maintenance and repairs. [0009] One available joint bay is a 'cast in-situ' reinforced concrete joint bay. As the name suggests, this form of bay is formed from concrete, and the typical construction process involves the following steps: Day 1 - Excavate and shore (depending on ground conditions) the site, and construct a working floor of an approximate 50 mm layer of concrete. Day 2 - Place reinforcement to base and walls. Day 3 - Pour concrete base slab. Day 4 - Place timber shuttering to internal and in some case external faces. Day 5 - Place concrete with concrete pump and vibrate/finish. Day 6 - Strip shutters and leave joint bay complete, ready for cable installation.

3 [0010] After the joint bay is constructed, the high voltage cables are installed into the joint bay from opposite ends. All in all, the typical time taken to install a single length of cable takes approximately one week. [0011] Following from the abovementioned construction, the two adjacent HV cables entering the bay have to be tested and, should that be successfully completed, the jointing process can then proceed. Jointing usually takes anywhere from days to weeks to finalise, depending on the number of cables, complexity of jointing process, amongst other factors. By way of example, Figure 2 shows a sample schedule of the typical time duration that a cast in-situ concrete joint bay is left open, from initial excavation to final completion and restoration. Moreover, as joint bays are typically located beneath or adjacent roads, access to the road and the surrounding footpath can be inhibited for several weeks during joint bay construction. This is disruptive not only to traffic flows, but also results in a considerable loss of amenity, over a long period, for local residents, businesses and other persons. [0012] Taking into consideration weather and other factors, it is not uncommon for traditional joint bays to remain open and exposed to the elements for up to ten weeks. In some cases a joint bay has to be backfilled and re-excavated or covered with steel plates prior to jointing of the cables, or at some other interim time during the installation and jointing process. This adds considerable delay, additional effort, cost and expense to the installation and creates a hazard for motorists and pedestrians that can give rise to personal or property damage. [0013] Additional factors can lead to longer delays such as cables or professional cable jointers not being available at the correct time for installation/jointing. [0014] In summary, the above common practices using traditional concrete cable joint bays have a number of disadvantages, including: > The rate of construction of the joint bays is extremely dependent upon the weather, which often results in delays. > The need to leave the joint bay in place for long time periods gives rise to a prolonged exposure to public safety issues. For example, the risk of vehicles crashing into joint bays, particularly at night.

4 > Traffic control at night with traffic lights or similar can create noise impact on residents. > Residential issues including access restrictions to driveways, traffic congestion and other inconveniences. SUMMARY OF THE INVENTION [0015] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. [0016] According to a first aspect of the present invention there is provided an installation unit including: a base for disposing below a predetermined surface; at least one sidewall extending upwardly from the base, the sidewall having an upper edge for defining an open top for disposing below the surface; a plurality of apertures located in the at least one sidewall for receiving respective conduits; a locating formation extending about at least a portion of the upper edge for selectively removably receiving a cover and an extension element, both of which, when received by the upper edge, do not extend above the surface. [0017] The extension element preferably includes a positioning formation for selectively removably receiving the cover. The extension element is preferably engagable with the locating formation and the cover is preferably engagable with the positioning formation to maintain the cover in an extended position. [0018] In an embodiment, the unit includes at least one reinforcing formation that extends across the open top. In another embodiment, the unit includes a plurality of spaced apart reinforcing formations. [0019] The cover preferably includes an upper surface and, in the extended position, the upper surface and the predetermined surface form a substantially continuous compound surface. [0020] The locating formation preferably includes a first support abutment and a first aligning abutment and the extension element preferably includes a second support abutment and a second aligning abutment. Preferably the first and the second support 5 abutments are substantially alike and the first and the second aligning abutments are substantially alike. More preferably, the locating formation extends continuously around the upper edge of the side walls. [0021] When the locating formation selectively removably receives the cover, the upper surface preferably lies below the predetermined surface. The predetermined surface is preferably a road surface and the cover is preferably adapted to support vehicular traffic travelling across the cover. [0022] The cover preferably includes at least one engagement formation for facilitating movement of the cover relative to the locating formation. The engagement formation preferably includes one or more lifting lugs. The lifting lugs are preferably disposed in corresponding recessions on the cover such that the lugs do not extend beyond the upper surface. [0023] In an embodiment, the engagement formation is defined by one or more reinforcing formations. In another embodiment, the engagement formation is mounted to the reinforcing formation. [0024] The cover preferably includes one or more precast support slabs. [0025] The installation unit preferably includes an earthing circuit for facilitating electrical isolation of the conduits. The earthing circuit preferably includes one or more earthing pins connected to a plurality of interconnected electrical conductors embedded within the base, side walls, extension element and cover. The conductors are preferably rigid metal support struts for reinforcing the unit. [0026] The base preferably includes one or more depressions defining at least one sump. [0027] The conduits preferably include one or more transmission cables. The transmission cables are preferably electrical and/or optical cables. [0028] The installation unit is preferably rectangular box-like in shape having four sidewalls. [0029] According to a second aspect of the present invention there is provided a method of installing an installation unit including the step of locating an installation 6 unit, according to the first aspect, in a pit, wherein the pit extends downwardly from the predetermined surface and the upper edge of the at least one sidewall is disposed below the surface. [0030] The method preferably further includes the step of engaging the extension element with the locating formation. The method preferably further includes the step of installing one or more conduits through the respective apertures. [0031] The method preferably further includes the step of engaging the cover with the extension element such that the upper surface of the cover forms a substantially continuous surface with the predetermined surface. [0032] The method preferably further includes the steps of: selectively removing the cover from the extension element; and performing one or both of the steps of: installing one or more conduits through the respective apertures; and jointing the conduits together within the installed unit; and [0033] The method preferably further includes the step of re-engaging the cover with the extension element to maintain the substantially continuous surface with the predetermined surface. [0034] The method preferably further includes the steps of: removing the extension element; engaging the cover with the locating formation to thereby reduce the height of the unit; and backfilling over the unit such that the unit is securely buried beneath the predetermined surface. [0035] Reference throughout this specification to "one embodiment", "some embodiments" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment", "in some embodiments" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be 7 combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. [0036] As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. [0037] In the claims below and the description herein, any one of the terms comprising, comprised of or which comprises is an open term that means including at least the elements/features that follow, but not excluding others. Thus, the term comprising, when used in the claims, should not be interpreted as being limitative to the means or elements or steps listed thereafter. For example, the scope of the expression a device comprising A and B should not be limited to devices consisting only of elements A and B. Any one of the terms including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising. BRIEF DESCRIPTION OF THE DRAWINGS [0038] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a block diagram of a typical underground high voltage circuit including joint bays; Figure 2 is an example time schedule outlining the time that a cast in-situ joint bay is left open; Figure 3 is a perspective view of an installation unit according to a first embodiment of the invention; Figure 4 is a cross-sectional exploded view of the cover, extension element and side arms according to the first embodiment; 8 Figure 5 is a transverse cross-section of an installation unit, according to the first embodiment, installed in a pit with nearby safety barriers; Figure 6 is a photograph of an installation unit installed beneath a road surface showing the upper surface of the extension portion and concrete support slabs defining a compound surface with the surrounding road; Figure 7 is a transverse cross-section of an installation unit according to the first embodiment showing the unit including the extension element and cover, and being installed in a pit; Figure 8 is a photograph of the interior of an installation unit having the extension element and a single concrete support slab installed; Figure 9 is a cut-away cross-sectional view of the sidewalls and the cover according to the first embodiment, with the cover received in the locating formation; Figure 10 is a plan view of an installation unit according to the first embodiment showing a single end-type concrete cover support slab in place; Figure 11 is an end cross-sectional view of an end-type concrete support slab according to the first embodiment; Figure 12 is a plan view of an end-type concrete support slab; Figure 13 is a side cross-sectional view of an end-type concrete support slab; Figure 14 is an end cross-sectional view of a centre-type concrete support slab according to the first embodiment; Figure 15 is a plan view of a centre-type concrete support slab; Figure 16 is a side cross-sectional view of a centre-type concrete support slab; Figure 17 is a segmented plan view of an extension element; Figure 18 is a transverse cross-section of an installation unit without the extension element, showing the unit installed under a re-sealed road surface; 9 Figure 19 is a plan view of an installation unit according to the first embodiment; Figure 20 is a cut-away transverse cross-sectional view of the base having a drainage sump; Figure 21 is a cross-sectional plan view of the base and sidewalls of an installation unit showing the locations of earthing pins and sockets; Figure 22 is a perspective view of an earthing rod connected to a portion of the earthing circuit taken along line D-D in FIG 21; Figure 23 is a cut-away cross-sectional view of the base of an installation unit showing two electrically conducting steel reinforcing elements being electrically connected to an intermediate connecting element by electrically conducting welds; Figure 24 is a cut away cross-sectional view of a cover for an installation unit showing a lifting lug being electrically and structurally connected to an internal reinforcing element; Figure 25 is a cut-away cross-sectional view of one side of the cover, extension element and one side arm according to an alternative embodiment; Figure 26 is a cut-away cross-sectional view of the sidewalls and the extension element according to an alternative embodiment, with the extension element received in the locating formation; Figure 27 is a cut-away cross-sectional view of the sidewalls and the cover according to an alternative embodiment, with the cover received in the locating formation; Figure 28 is a cut-away cross-sectional view of one side of an extension element of an alternative embodiment engaged with the locating formation of one sidewall; Figure 29 is a segmented cross-sectional view of an extension element according to an alternative embodiment; 10 Figure 30 is a plan view of an installation unit according to an alternative embodiment; Figure 31 is a transverse cross-section of the installation unit of Figure 30 without the extension element, showing the unit installed under a re-sealed road surface; Figure 32 is a plan view of an installation unit according to the embodiment of FIG 27 showing a single concrete cover support slab in place; Figure 33 is a perspective view of an earthing rod connected to a portion of the earthing circuit taken along line E-E in FIG 21; Figure 34 is a transverse cross-section of an installation unit according to an alternative embodiment showing the unit including the extension element and cover, and being installed in a pit; Figure 35 is a transverse cross-section of an installation unit, according to another embodiment, installed in a pit with nearby safety barriers; and Figure 36 is a flow chart illustrating a method of installing an installation unit according to one embodiment of the invention. DETAILED DESCRIPTION [0039] Referring to Figures 3 and 5, there is provided a pre-cast reinforced concrete installation unit 100 including, as best shown in Figure 5, a generally rectangular base 102 for disposing below a predetermined surface, such as a road surface 104. Unit 100 also includes four integrally formed generally linear and rectangular sidewalls 106, which all extend upwardly from base 102. Sidewalls 106 terminate in and collectively define a single continuous generally rectangular upper edge 108 for defining an open top that is also disposed below surface 104. Thirteen generally circular and spaced apart apertures 110 are located in two longitudinally spaced apart and opposed sidewalls 106 for receiving respective conduits (not shown), such as electrical cables, optical cables or fluid pipes. However, it will be appreciated that, in other embodiments, varying numbers, types and locations of apertures are included.

11 [0040] Referring to Figure 4, a locating formation 112 extends continuously about all of edge 108 for selectively complementarily removably receiving a pre-cast reinforced concrete cover 114 and a pre-cast reinforced concrete extension element 116, both of which, in use, do not extend above surface 104. In the illustrated embodiment, sidewalls 106 each include an inner surface and an outer surface, and formation 112 extends from the inner surface to the outer surface. However, in other embodiments, formation 112 extends only partly between the surfaces, while in further embodiments formation 112 extends horizontally beyond the surfaces. [0041] As best shown in Figures 5 and 6, unit 100 is adapted for installation beneath road surface 104 for allowing selective access to the interior of unit 100 during the jointing, connecting and routing of high voltage underground electrical transmission cables to form a transmission cable circuit between a source and termination (neither shown). The embodiments of the invention will be described with primary reference to that application. However, in other embodiments, unit 100 is adapted for installation beneath other surfaces such as footpaths, construction sites and parks. Further, in additional embodiments, unit 100 is adapted to receive, through apertures 110, other types of conduits, including one or more of optical fibres and cables, gas pipes and water pipes, other communications or telecommunications cables, and the like. That is, unit 100 offers a convenient site for the respective jointing, connecting, routing and maintenance of all these, and other, conduits. [0042] As shown in Figures 3, 7 and 8, different sized apertures 110 are included in unit 100 to accommodate different sized cables and/or different types of cables. It will be appreciated by those skilled in the art that the apertures provided in the illustrated embodiments are by way of example only, and that many other aperture sizes and configurations are available to suit different applications of the embodiments. It will also be appreciated that while the apertures are matched at opposite ends of unit 100 on the assumption that all cables or other conduits will be jointed to another like cable or conduit - in other embodiments there are different numbers or configurations of apertures used. For example, in some embodiments, unit 100 is used as a termination point for one or more cables, such as those cables that are connected to a diagnostic port that is disposed within the bay and which remains within the bay. In still further 12 embodiments, the apertures are disposed other than in opposite sidewalls 106, for example, where unit 100 is at a 900 bend in the circuit. [0043] A transmission cable circuit formed with the use of the present embodiments includes a first plurality of cables and a second plurality of intermediate units 100 for receiving the ends of adjacent cables and for providing a site of the installation, testing, and jointing of those cables. That is, the joint bays of Figure 3 are replaced by respective units 100. [0044] Referring again to Figure 3, unit 100 is rectangular box-like in shape and has four sidewalls 106. More specifically, unit 100 has a transverse width of about 2,400 mm, a longitudinal length of about 6,000 mm and a height of about 2,500 mm. However, it will be appreciated that in other embodiments, unit 100 has different structural shapes, including specifically a cubic or cylindrical shape, and different dimensions. In further embodiments, other shapes are used. [0045] Referring to Figures 4 and 9, formation 112 includes a substantially horizontal support abutment 118 for selectively supporting a lower surface 120 of cover 114 (as seen in Figure 11) about its periphery. Abutment 118 also selectively supports a corresponding receiving formation in extension element 116 (as seen in Figure 4). [0046] It will be appreciated by those skilled in the art, that formation 112 directly receives at any given time no more than one of cover 114 and element 116. However, formation 112 is configured to support both, albeit mutually exclusively. [0047] A substantially vertical aligning abutment 122 extends upwardly from abutment 118 for maintaining selectively cover 114 and extension element 116 in a predetermined position with respect to unit 100. Abutment 122 includes an upper surface 124 that is substantially planar, parallel with, and horizontally level with an upper surface 126 of cover 114. [0048] In one embodiment (not shown) formation 112 extends continuously circumferentially around upper edge 108 of walls 106 to define a continuous support bracket in which extension element 116 or cover 114 are selectively located. [0049] As illustrated in Figures 3, 8 and 17, a generally rectangular and tubular extension element 116 is complementarily engagable with locating formation 112, and 13 cover 114 is complementarily engagable with formation 130 to maintain cover 114 in an extended position. [0050] Referring to Figures 3 and 4, it is shown that formation 130 is adapted to selectively removably receive cover 114. Like formation 112, formation 130 includes a horizontal support abutment 132 and a vertical aligning abutment 134. As best shown in Figure 4, abutment 134 has a vertical dimension that is much larger than the corresponding vertical dimension of abutment 122. However, in other embodiments, abutment 132 and abutment 134 are each substantially alike to the corresponding abutment 118 and abutment 122 of formation 112. In further alternative embodiments, abutment 134 is angled with respect to abutment 132. [0051] In the illustrated embodiment, element 116 is formed of concrete having steel reinforcing elements 140. However, in other embodiments, element 116 is formed of other rigid or non-rigid materials, with or without internal reinforcement. [0052] Referring to Figure 10, cover 114 includes a plurality of individual but like precast reinforced concrete support slabs 142 that extend transversely across unit 100. For the sake of clarity, only one slab 142 is illustrated in each of these figures. In use, slabs 142 are arranged in a longitudinal array with adjacent slabs in the array being abutted side-by-side to cover substantially all of the open top of unit 100. In the embodiment of Figure 10, the array has six like slabs 142. In other embodiments, a different number of slabs are included in the array. It will also be appreciated that in further embodiments not all the slabs in the array are dimensionally alike. As shown in Figures 11 to 16, slabs 142 can be of end-type (see Figures 11 to 13) or centre-type (see Figures 14 to 16). [0053] As shown in Figures 5 to 7, in the extended position, surface 126 of cover 114 and surface 144 of element 116 forms a substantially continuous compound surface 146 with road surface 104. Unit 100 and cover 114 are adapted to support vehicular traffic travelling across cover 114 such that vehicle occupants experience little or no discomfort due to vertical discontinuities in the compound surface. That is, with cover 114 maintained in the extended position of Figures 5 to 7, compound surface 146 is able to be used by vehicular traffic as a typical road surface is used. By way of example, specific reference is made to Figure 6, where an installed unit 100 is 14 shown with cover 114 and surface 144 providing, in combination with surface 104, a substantially continuous compound surface 146. In Figure 6 the road runs longitudinally. In other embodiments, the road extends other than longitudinally. [0054] As shown best in Figure 4, cover 114 is selectively removable from element 116 by disengaging cover 114 from formation 130. In a similar manner, element 116 and cover 114 are also selectively removable from formation 112. [0055] Due to the load bearing requirement of cover 114 and element 116, these components are typically relatively heavy. Accordingly, the movement and placement of these components is often undertaken with a crane (not shown) or other heavy lifting machinery. To facilitate movement of cover 114 relative to formation 112 using a crane, surface 126 includes a plurality of engagement formations in the form of lifting lugs 148, for engaging a tether or chain (not shown). [0056] Referring to Figures 11 to 16, lugs 148 are disposed in corresponding recessions 150 in surface 126 such that lugs 148 do not extend beyond the upper surface. Further, as shown in Figures 25 and 28, lugs 148 are connected to elements 140 that are embedded within slabs 142 to reduce the risk of lugs 148 separating from slabs 142 and the slabs being damaged. In other embodiments, different forms and locations of lugs are used. [0057] During the installation, testing and jointing of cables, it is usual for formation 112 to first receive element 116 and, once the jointing is completed, for element 116 to be removed from unit 100 and for formation 112 to receive cover 114. Typically, when formation 112 receives element 116, the same cover will be placed upon element 116 selectively to define in part surface 146. Once element 116 is removed from formation 112, and cover 114 received by that formation, surface 126 lies below road surface 104, as shown in Figure 18. The road is then resurfaced over unit 100. Accordingly, following installation and jointing of the cables, the road is returned substantially to its original look and feel. [0058] As best shown in Figures 4 and 19, unit 100 also includes engagement rings 152 for facilitating lifting and movement of the unit by a crane or other heavy lifting machinery (not shown). In one embodiment rings 152 are mounted to each end of base 102. This arrangement allows easy access for engaging a chain or tether and 15 provides balanced lifting of unit 100. Referring specifically to Figure 6, rings 152 extend into base 102 and, in one embodiment, are formed of steel. In alternative embodiments different spatial arrangements and number of engagement rings 152 are used. [0059] Referring to Figures 3 and 10, element 116 includes engagement apertures 154 for receiving a chain or tether to facilitate movement of element 116 relative to locating formation 112. In alternative embodiments, apertures 154 are located at different positions on element 116 and are of different sizes to accommodate different sized tethers. It will be appreciated that, in embodiments where element 116 is small enough to be lifted by a person, extension element 116 does not include engagement apertures 154. [0060] As shown in Figures 19 and 20, base 102 includes at least one depression defining respective sumps 156 for drainage of unwanted fluids and/or flowable materials. Referring to Figure 19, use is made of two transversely centred longitudinally spaced apart like sumps 156. These sumps are square shaped and covered by respective protective gratings 158. In other embodiments, use is made of only a single sump while, in further embodiments, use is made of more than two spaced apart sumps. [0061] In some embodiments, the separate sumps are connected to piping or ducts (not shown) for facilitating the egress from unit 100 of any received liquids or other flowable materials. It will be appreciated that base 102 is contoured to preferentially direct any impinging liquid to sumps 156. [0062] Referring to Figures 21 and 22, unit 100 includes an earthing circuit (collectively labeled 162) for facilitating isolation of the conduits (not shown) from external electrical currents and circuits. While the primary source of such external currents is nearby lightning strikes, other sources include interference from power lines for electric trains, other power cables and the like. Circuit 162 reduces the risk of power surges and the like in the cables and the transmission circuit. [0063] As best shown in Figure 22, circuit 162 includes an earthing pin 164 that is connected to a plurality of interconnected electrical conductors 166 embedded within base 102, sidewalls 106, element 116 and cover 114. In this embodiment, the electrical 16 conductors are primarily defined by the already present embedded reinforcing elements 140. It will be appreciated that elements 140 are formed from steel and, when element 116 and/or cover 114 is engaged as in Figures 5 to 7, earthing circuit 162 provides a continuous conducting path from cover 114 through to ground. This path extends from cover 114, through base 102 and earthing rods 168 to ground. In other embodiments, circuit 162 makes use of conductors other than elements 140. Moreover, in further embodiments, elements 140 are formed of conductive material other then steel. [0064] Figure 21 shows a plan view of unit 100 where circuit 162 extends within base 102 and sidewalls 106. Circuit 162 also includes a plurality of spaced apart electrical sockets 170 that are embedded in sidewalls 106 and base 102 for electrically receiving earthing pins 164. In the embodiment of Figure 22, pins 164 are lockable into sockets 170 by locking screws 171. Sockets 170 are electrically connected with electrically conducting reinforcing elements 140. This provides an installer of unit 100 with flexibility in the selection of the socket or sockets that are to be used to provide the required earthing for unit 100. For it will be appreciated by those skilled in the art, once unit 100 is placed, it is often difficult to have it moved for the sake of being able to access a good earth connection. Accordingly, providing a selection of access points for such an earth connection is advantageous. [0065] Referring again to Figure 19, sockets 170 are located at both ends of base 102 and are electrically connected to reinforcing elements 140 inside the base. As shown in Figure 23, adjacent reinforcing elements 140 are electrically interconnected by electrically conducting welds 172 and connecting elements 174. As shown in Figure 24, lifting lugs 148 are electrically connected to earthing circuit 162 through reinforcing elements 140. [0066] Returning to Figure 5, during construction of a pit 176 in which unit 100 is to reside, or when cables are being installed or jointed, barriers 178 are located around pit 176. Barriers 178 are placed at suitable locations to protect pit 176 from subsidence, and to prevent vehicles, construction equipment and stacked materials from entering the pit. In one embodiment barriers 178 are situated at a position such that the angle of declination at the barrier from road surface 104 to the closest side of base 102 at the barrier is about 45'. In another embodiment, barriers are set about 17 2250 mm from each side of pit 176. In alternative embodiments, barriers 178 are placed at varying locations. In further alternative embodiments, barriers 178 are substituted or complemented with a fence extending around pit 176. [0067] Depending on ground conditions, a layer of concrete (typically about 50 mm not shown) may be laid on the base of pit 176 as a foundation for unit 100. [0068] As shown in Figure 18, after installation and jointing of the cables, it is possible to fill the interior of unit 100 with sand 180, soil or other compounds such as gravel to protect the cables and support them within the unit. In alternative embodiments, the interior of unit 100 is left empty to allow future access to the cables. [0069] In some embodiments, unit 100 is sufficiently sealed, by the engagement of cover 114 with extension element 116 or locating formation 112, to restrict unwanted debris, animals and insects from entering unit 100. In particular embodiments, unit 100 is sufficiently sealed to restrict fluids such as water from entering the unit. This is particularly advantageous when electrical cables are installed through the unit. In one embodiment, such sealing is provided by a continuous rubber seal (not shown) located circumferentially about locating formation 112 and cover 114. In other embodiments, sealing is provided by a plastics or other seal (not shown). [0070] A number of alternative embodiments of the invention will now be described where corresponding features are given the same reference numerals. [0071] In the embodiment illustrated in Figure 25, formation 112 includes a generally straight groove 136 and element 116 includes a complementary downwardly inclined projection 138 that is complementarily received within the grove. In a particular embodiment, grooves 136 and projections 138 are spaced about upper edge 108 of sidewalls 106 as shown in Figure 26. In other embodiments, grooves 136 and projections 138 extend substantially continuously around upper edge 108. In some embodiments, similar grooves are also located on abutment 132 and similar corresponding projections are located on the underside 120 of cover 114 immediately adjacent abutment 132. [0072] It will be appreciated that, in various embodiments, formation 112 includes one or a combination of grooves, slots and/or abutments located in predetermined positions about upper edge 108 of side walls 106 to selectively guide cover 114 or element 116 18 into a predetermined secure orientation with respect to sidewalls 106. In particular, in some embodiments, formation 112 is shaped to not only dictate the location but also the orientation of one or more of cover 114 and element 116. For example, in some embodiments, use is made of an asymmetric spacing of the abutments or indents about edge 108. [0073] In the embodiment shown in Figures 26 and 27, abutment 132 and abutment 134 are each substantially alike to the corresponding abutment 118 and abutment 122 of formation 112. In Figure 13, upper surface 126 extends above abutment 122. In further embodiments, abutment 122 is obtusely angled with respect to abutment 118. [0074] As shown in Figure 28, in one embodiment, locating formation 116 has a cross sectional width that is substantially the same as that of side walls 106. Further, as shown in both Figures 28 and 29, locating formation 116 includes reinforcing elements 140 having a wide central portion 182 and a thinner vertically extending arm portion 184. [0075] Referring to Figure 30 and 31, other types of sumps 156 are shown. In this embodiment, base 102 includes two longitudinally centred transversely spaced apart sumps 156 having respective gratings 158. In addition, base 102 includes a transversely centred longitudinally elongate sump 160 that extends between sumps 156 and along substantially all of base 102. That is, a combination of localized sumps 156 and longitudinal sumps 160 are able to be used. Referring to Figure 27, base 102 is contoured to direct fluids and particulate material into sumps 156 and 160. [0076] Referring to Figure 32, cover 114 is formed from a longitudinal array of four slabs 142. In further alternative embodiments, cover 114 is formed from a different number of slabs 142 including, in one embodiment, a single slab 142. [0077] Referring to Figure 33, an alternative embodiment of earthing circuit 162 is shown. Here pins 164 are insertable into sockets 170 without locking screws 171. In this embodiment, pins 164 engage sockets 170 by radial supporting interfering engagement due to their similar radii.

19 [0078] Figures 34 and 35 illustrate alternative embodiments wherein unit 100 includes different arrangements of apertures 110 for receiving different numbers, types and configurations of conduits (not shown). [0079] Referring to Figure 36, the above-described installation unit 100 gives rise to a novel method of installing an installation unit. At step 200, unit 100 is manufactured at a predetermined manufacturing facility. At step 202, a pit 176 is excavated at a predetermined location. Pit 176 extends downwardly from road surface 104 and is formed to be of a size appropriate for receiving unit 100. This step will typically occur after the manufacture of unit 100. However, it will be appreciated that excavation of pit 176 may begin before or concurrently with the manufacture of unit 100. [0080] At step 204 installation unit 100 is installed by locating unit 100 in pit 176, such that the upper edge of sidewalls 106 are disposed below surface 104. At this point, in one embodiment, extension element 116 is engaged with locating formation 112. In alternative embodiments, where cables and jointers are available for immediate installation and jointing, extension element 116 need not be installed. [0081] At step 206, pit 16 is backfilled around unit 100 to secure unit 100 in pit 176. At step 208 a decision is made as to whether or not the cables should be installed through unit 100. This decision depends on the availability of the cables and the suitability of leaving pit 176 open in consideration of possible traffic congestion and other factors. If the decision is to delay installing the cables, at step 210 cover 114 is placed in positioning formation 130 such that upper surface 126 and road surface 104 form the substantially continuous compound surface 146. At step 212 workers await a suitable time for installing the cables. During this time, compound surface 146 is able to be used as normal road surface 104 with cover 114 supporting passing vehicular traffic. This reduces the impact that the construction site would otherwise impose on the local environment and personal movements within that environment. [0082] When it is desirable to install the cables, at step 214 cover 114 is removed from positioning formation 130 and extension element 116 to provide access to the interior of unit 100 and the cables are installed in a conventional manner. [0083] At step 216 a decision is made as to whether or not the cables should be jointed. This decision depends again on the suitability of leaving pit 176 open and also depends 20 on the availability of professional cable jointers. If it is not considered suitable to joint the cables at this time, at step 218 cover 114 is placed in positioning formation 130 such that upper surface 126 and road surface 104 form the substantially continuous compound surface 146. At step 220 workers await a suitable time for jointing the cables. During this time, compound surface 146 is again able to be used as normal road surface 104, with cover 114 supporting vehicular traffic. [0084] When it is desirable and possible to joint the cables, at step 222 cover 114 is removed from positioning formation 130 and extension element 116 to provide access to the interior of unit 100 and the cables are jointed in a conventional manner. [0085] At step 224 a decision is made as to whether or not unit 100 should be buried beneath surface 104 or left accessible for future cable installation, jointing or repairs. If it is considered desirable or necessary to retain easy access to the interior of unit 100, at step cover 114 is replaced to form compound surface 146. Figure 21 illustrates this situation, with vehicular traffic able to use the road as normal simply by progressing over supported cover 114. At any time, cover 114 is able to be removed to again access the interior of unit 100. [0086] If it is decided to bury unit 100 beneath road surface 104, at step 228 extension element 116 is removed and cover 114 is engaged with locating formation 112. Sand 180 or other particulate material may be used to fill the interior of unit 100 prior to engaging the cover. Pit 176 is then backfilled over unit 100 and the above road is resurfaced. In this situation, the road is returned substantially to its original look and feel. [0087] It will be appreciated that, with the use of the above embodiments, cable installation and jointing is able to be scheduled to suit availability of resources. Additionally, the method of installing the joint bay is able to be modified depending on available resources. For example, in one embodiment intended to minimize costs, the installed joint bay is left as initially constructed with the extension collar in place and supporting the removable concrete slabs. The slabs act as the new permanent road surface above the joint bay. This is shown in Figure 5. A project implementing this methodology does not require the additional cost of removing the extension collar, backfilling the pit and resurfacing the road. In an alternative embodiment intended to 21 provide increased aesthetics, the extension collar is removed, the cover slabs are supported on the rim of the side walls and the pit backfilled to be covered by a new road surface. A project implementing this methodology would inherently include additional cost but maintain more aesthetically pleasing site. [0088] In a further alternative embodiment, the extension collar is not installed and the cover is placed directly on the rim of sidewalls and the road is directly resurfaced over the cover. This embodiment is implemented where the cables and jointers are available immediately after installation of the joint bay. However, this embodiment does not provide the capability to re-seal the joint bay overnight during the cable installation/jointing period. CONCLUSIONS [0089] It will be appreciated that the disclosure above provides an underground installation unit 100 having a removable cover 114 and a removable extension element 116 allowing the height of the unit to be selectively adjusted. Installation unit 100 is able to be installed typically in two days instead of about six days for conventional joint bays. [0090] In contrast to the traditional method of installing an in-situ cast joint bay, the above described embodiments of the present invention provide a pre-cast installation unit 100 or joint bay that is able to be delivered to an installation site via truck or other vehicle and lowered into pit 176 with a crane or other lifting apparatus. Furthermore, extension element 116 extends from the top of side walls (about 300 mm below the road surface 104 in one embodiment) to the road surface 104. Element 116 supports the precast concrete cover slabs and allows rapid restoration of the immediate area, while also allowing later access for cable installation/jointing. Precast concrete cover slabs 142 are suitable for heavy vehicle loadings and are readily removable with a conventional backhoe, hi-ab truck, crane or the like. [0091] The off-site manufacture of installation unit 100 and the selective accessibility provided by extension element 116 reduces the overall time that pit 176 is open and exposed. This has important advantages in relation to cost savings, environmental and safety concerns, and local resident satisfaction. In particular, labour and construction 22 costs associated with the installation and jointing are able to be reduced as there is a decreased need for implementing traffic control, crash barriers, fencing etc. [0092] The installation unit 100 also includes an integrated earthing circuit 162 allowing installation of earthing rods 168 after installation of unit 100. [0093] In various embodiments, the present invention provides one or more of the following advantages: > Safety, security and damage risks associated with open excavations and joint bays/installation units are reduced - the present invention generally only requires a pit to be open and unattended during unit installation, cable installation and jointing works, which typically lasts about two to three weeks. Further, the site is able to be easily re-sealed after each day's work to increase safety to residents and motorists. > The re-sealable site is more aesthetically pleasing and has a lower impact on the surrounding community, including reduced traffic congestion and reduced restrictions to residents' access to driveways. > Environmental issues associated with discharging rain water during construction and cable installation are reduced. > Less traffic control, barriers, fencing and other equipment/logistics are required, which reduces the overall project cost. For example, based upon relatively conservative assumptions, the inventor has estimated cost savings of about AU$19,000 per joint bay for construction and about AU$12,000 per joint bay for cable installation and jointing. These savings are relative to a traditional methodology utilizing in-situ cast joint bays. > Construction and installation of the installation unit is able to be carried out even if the transmission cables or professional jointers are not available. > The installed cables and joints are able to be tested prior to the joint bay being completely backfilled. [0094] It will be appreciated that, while the above described embodiments have been developed for jointing high voltage electrical power transmission cables, the invention 23 may also be used in connecting other conduits such as electrical and optical data cables, and water and gas pipes. [0095] It should be appreciated that in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, Figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this invention. [0096] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination. [0097] Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention. [0098] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

24 [0099] Similarly, it is to be noticed that the term coupled, when used in the claims, should not be interpreted as being limited to direct connections only. The terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Thus, the scope of the expression a feature A coupled to a feature B should not be limited to features or systems wherein an output of feature A is directly connected to an input of feature B. It means that there exists a path between an output of A and an input of B which may be a path including other features or means. "Coupled" may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other. [00100] Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications that fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

Claims (29)

1. An installation unit including: a base for disposing below a predetermined surface; at least one sidewall extending upwardly from the base, the sidewall having an upper edge for defining an open top for disposing below the surface; a plurality of apertures located in the at least one sidewall for receiving respective conduits; a locating formation extending about at least a portion of the upper edge for selectively removably receiving a cover and an extension element, both of which, when received by the upper edge, do not extend above the surface.

2. An installation unit according to claim 1 wherein the extension element includes a positioning formation for selectively removably receiving the cover.

3. An installation unit according to claim 2 wherein the extension element is engagable with the locating formation and the cover is engagable with the positioning formation to maintain the cover in an extended position.

4. An installation unit according to claim 3 wherein the cover includes an upper surface and, in the extended position, the upper surface and the predetermined surface form a substantially continuous compound surface.

5. An installation unit according to any one of the preceding claims wherein the locating formation includes a first support abutment and a first aligning abutment and the extension element includes a second support abutment and a second aligning abutment.

6. An installation unit according to claim 5 wherein the first and the second support abutments are substantially alike and the first and the second aligning abutments are substantially alike.

7. An installation unit according to any one of the preceding claims wherein the locating formation extends continuously around the upper edge of the side walls. 26

8. An installation unit according to any one of the preceding claims wherein, when the locating formation selectively removably receives the cover, the upper surface lies below the predetermined surface.

9. An installation unit according to any one of the preceding claims wherein the predetermined surface is a road surface and the cover is adapted to support vehicular traffic travelling across the cover.

10. An installation unit according to any one of the preceding claims wherein the cover includes at least one engagement formation for facilitating movement of the cover relative to the locating formation.

11. An installation unit according to claim 10 wherein the engagement formation includes one or more lifting lugs.

12. An installation unit according to claim 11 wherein the lifting lugs are disposed in corresponding recessions on the cover such that the lugs do not extend beyond the upper surface.

13. An installation unit according to any one of the preceding claims wherein the cover includes one or more precast support slabs.

14. An installation unit according to any one of the preceding claims including an earthing circuit for facilitating electrical isolation of the conduits.

15. An installation unit according to claim 14 wherein the earthing circuit includes one or more earthing pins connected to a plurality of interconnected electrical conductors embedded within the base, side walls, extension element and cover.

16. An installation unit according to claim 15 wherein the conductors are rigid metal support struts for reinforcing the unit.

17. An installation unit according to any one of the preceding claims wherein the base includes one or more depressions defining at least one sump.

18. An installation unit according to any one of the preceding claims wherein the conduits include one or more transmission cables. 27

19. An installation unit according to claim 18 wherein the transmission cables are electrical and/or optical cables.

20. An installation unit according to any one of the preceding claims wherein the unit is rectangular box-like in shape and has four sidewalls that extend upwardly from the base.

21. A method of installing an installation unit including the step of locating an installation unit according to any one of the preceding claims in a pit, wherein the pit extends downwardly from the predetermined surface and the upper edge of the at least one sidewall is disposed below the surface.

22. A method according to claim 21 further including the step of engaging the extension element with the locating formation.

23. A method according to claim 21 or claim 22 further including the step of installing one or more conduits through the respective apertures.

24. A method according to claim 22 further including the step of engaging the cover with the extension element such that the upper surface of the cover forms a substantially continuous surface with the predetermined surface.

25. A method according to claim 24 further including the steps of: selectively removing the cover from the extension element; and performing one or both of the steps of: installing one or more conduits through the respective apertures; and jointing the conduits together within the installed unit.

26. A method according to claim 25 further including the step of re-engaging the cover with the extension element to maintain the substantially continuous surface with the predetermined surface.

27. A method according to claim 25 further including the steps of: removing the extension element; engaging the cover with the locating formation to thereby reduce the height of the unit; and 28 backfilling over the unit such that the unit is securely buried beneath the predetermined surface.

28. An installation unit substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying figures 3 to 36 and/or examples.

29. A method of installing an installation unit substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying figures 3 to 36 and/or examples.