GB2360884A - Electrical distribution system - Google Patents

Abstract

A temporary electrical installation for a construction site comprises a mains distribution unit (1), at least one item of plant, and at least one armoured cable (17) having an electrical connector (18, 19) at each end. The mains distribution unit (1) has a plurality of electrical connectors (12) hardwired thereto and providing a plurality of power outlets at differing ratings. At least one item of plant, for example a transformer (3) has an electrical connector (30) hardwired thereto providing a power inlet. The armoured cable (17) has one end connectable to a power outlet connector (12) of the mains distribution unit (1) and one end connectable to the power inlet (30) connector of the transformer (3).

Description

2360884 ELECTRICAL DISTRIBUTION SYSTEM The invention relates to an

electrical distribution system for a construction site or the like.

Presently, in the UK, the electrical power for a construction site is provided by setting up a temporary mains distribution unit (MDU) which is connected to the local electrical utility substation.

Figure 1 shows diagrammatically an example of a simple electrical distribution set up of a typical construction site. A meter with connection blocks and fuses is used to supply power to a mains distribution unit (MDU) 1, which allows for power to be distributed to the items of plant and other equipment which, in this example, include the site accommodation set up 44, storage containers and compound 2, transformers 3 of varying specifications, a hoist supply 4, site lighting 5, hoarding lighting 6, a welding power supply 7, tower crane supply 8, a compressor 42 and a cube tank 45. On other sites there may be further requirements such as, flood lights, a temporary lift supply, a batching plant pumps and supplies for diamond drilling which would be accommodated in similar manner. The MDU 1 will also have a mains isolation switch.

At present, site electricians in conjunction with the local electricity supplier, set up the meter box 43 and the MDU 1. Once the meter and MDTi 1 are established the other items of equipment are added as and when required dependent on the site needs.

The IVIDU 1 typically comprises a metal box containing a series of incoming 2 and outgoing switch gear accessed by means of a lockable door. Each of the components, for example as shown in figure 1, is hardwired to the MDU 1 by means of armoured cables that vary in size dependent on the load they are required to carry and the desired length of cable.

Presently, in the state of affairs described above, when the construction work is finished or particular items of plant or equipment no longer needed, electricians are again contracted to remove the electrical installation or equipment. The electricians generally retain the used (mainly cabling) materials. A small percentage, typically 10%, of the initial cost of materials supplied by the electricians is sometimes returned to the construction company. It is an object of the present invention to provide an electrical distribution system that will allow cables to be easily reused. Such a system would save a constructions company a significant amount of money over time and also conserve resources by reducing waste caused by unnecessary disposal of materials.

A further problem with the present system is that as construction progresses there may be a need to make changes to the layout of the site plant, despite good planning. Each time changes are made it is necessary to contract electricians to rewire the system because all of the components typically needed on a construction site are hard wired to the MDU or to a transformer which is hard wired to the MDU. It is a further object of the present invention to provide a modular system that allows more flexibility and less need to resort to qualified electricians.

Whilst it has been known to provide certain socket outlets with an MDU, these have been for specific purposes mainly for welding supplies and temporary lighting.

3 Generally, these socket outlets have been standard 1 1OV or 215V supplies. It has not been known to provide a MDU having sufficient outlet sockets, at the required ratings, to provide supplies for all the plant and other equipment on a typical. construction site or to provide inlet sockets on the plant or equipment supplies.

GB-A-2248148 discloses a method of making a branching connector on a cable, in particular, for providing a connector for attaching a lamp. This allows a series of connectors to he fitted on a single cable, allowing flexible positioning of lamps for example.

Accordingly, the present invention provides a temporary electrical installation for a construction site comprising a mains distribution unit, at least one item of plant, and at least one armoured cable having an electrical connector at each end; wherein the mains distribution unit has a plurality of electrical connectors hardwired thereto and providing a plurality of power outlets at differing ratings; said at least one item of plant has an electrical connector hardwired thereto providing a power inlet; said at least one armoured cable having one end connectable to a power outlet connector of the mains distribution unit and one end connectable to the power inlet connector of the item of plant.

The mains distribution unit may have a plurality of cables hardwired thereto and said power outlet connectors being provided at the end of said cables.

The at least one item of plant may be one, or more than one, of a mains distribution panel, a site cabin, a temporary lift, tower crane supply, a compressor, a cube tank, a flood light supply, a temporary lift supply, a batching plant, a pump and a 4 supply for a drilling apparatus or welding supply.

Each of said electrical connectors of said mains distribution unit, said at least one item of plant and said at least one armoured cable, may comprise one half of a two-part insulated electrical connector, said twopart connector comprising a safety means for preventing accidental disconnection of the two-part connector. The safety means may comprise a retaining clip, a through fixing, a web or tape wrapped around the connector.

The connectors of said at least one armoured cable may be complementary halves of a two-part an electrical connector. Alternatively, the connectors of said at least one armoured cable may be the same at each end.

The invention will now be described in more detail and by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic of a typical prior art constructions site layout; Figure 2 is a perspective view of a MDU according to one embodiment; Figure 3 is a view from the front of an MDU according to an alternative embodiment; Figure 4 shows an armoured cable according to an embodiment; Figure 5 and 5a show schematically a front view and side section of a site cabin according to an embodiment; Figure 6 shows a light fitting according to an embodiment; Figure 7 is a schematic of a lighting system according to an embodiment; Figure 8 is a schematic of a transformer according to an embodiment; Figures 9 and 10 show alternative arrangements of formers connected to an MDU of the invention;

Figure 11 is a schematic of a simplified internal temporary electrical installation.

An embodiment of the invention will be discussed using figure 1 as the example of a site layout showing the plant and other items requiring electrical supply. It will be appreciated that Figure 1 is a simplified representation and that the invention is applicable to any construction site that presently requires plant and other items to be hardwired to a MDU.

Figure 2 shows a standard MDU 1 that has been modified in accordance with the invention. The MDU 1 consists of a metal cabinet 9 incorporating the circuit breakers (not shown) behind front covers 10, which are secured by means of a lock 11. The MDU cabinet construction will need to conform to British or other local standards and may fabricated from steel sheets, seam welded and painted to reduce corrosion.

Openings in the front cover 10 provide access to a plurality of electrical outlet connectors 12 of various different ratings. The number of outlets corresponding to different electrical ratings will depend on the project requirements. In the embodiment there are a plurality of outlets 12 providing 110, 240 and 415 volts with ratings of 16, 32, 63 and 125 amps. Typically these outlets will be BS 4343/IEC309. However, sockets to BS 196,1363 can also be incorporated. Protection to these is by mains circuit breakers (MC13s) or Residual Current Devices (RCDs) located within the cabinet. The outlet connectors 12 in this embodiment are conveniently electrical sockets. However, plug connectors or live pins could be substituted for the sockets or some other electrical coupling could be used. A mains isolation device 13 is provided to lock off the incoming power supply from armoured cable 15. The armoured cable 6 is hardwired to the MDU at one end and to the meter block 43 at the other end (not shown).

In a particular embodiment, each electrical connector is unique so that it is impossible to connect an incorrect cable thereto. Alternatively, the connectors, which may be plugs and socket connectors, are provided with coding lugs or pins which act to prevent insertion of incorrect types of equipment. The lugs may be bayonet type projections arranged to fit into slots or grooves. An example of a system of industrial electrical connectors is the Commando (TM) range manufactured by MK. This system of insulated and protected plugs and outlet sockets or connectors makes use of both pin/key configurations for each voltage/frequency and also a colour coding system identifying the rating of the particular connector.

In an alternative embodiment the MDU 1 has an inlet connector for receiving a corresponding connector of the armoured cable 15. Alternatively, the armoured cable 15 might be hardwired to the MDU and have an inlet connector at one end for connection to an outlet connector of the meter box 43 or to an outlet connector of an armoured cable hardwired to the meter box 43. An electrically insulated, two-part connector for this purpose ideally has a power capacity in excess of the load carried by armoured cable 15. Safety devices would have to be provided to prevent accidental disconnection.

In order to achieve effective reuse of the IMU 1 without further modification, the total number of outlet connectors 12 and the number of outlet connectors 12 at each rating is selected to be sufficient for any particular project of the size of project to which the MDU is adapted. In keeping with the present practice there will be a range of MDU sizes to suit different size projects, for example, MDUs may be 7 purpose made in three standard models to suit small, medium and large projects.

Figure 3 shows another embodiment of the MDU 1, in which the connectors 12 are provided on the end of short cables 16 that have been hardwired into the MDU at the factory. The cables 16 are preferably less than Imetre long to enable them to be neatly stowed away for transportation and handling on delivery and removal. A simple support could be provided to support the cables off the ground to prevent damage, or contamination.

Figure 4 depicts an armoured cable according to the invention. A standard armoured cable 17 is provided with an outlet connector 18 at one end and an inlet connector 19 at the other end. Conveniently, the inlet and outlet connectors are provided by an insulated, electrical plug and an electrical socket respectively.

The armoured cables 17 vary in diameter depending on the load they are intended to carry. The outlet and inlet connectors will also vary proportionately. A cable 17 may be made to order if the correct diameter cable is not held in stock. Presently, cables of the required length are cut off a roll and hard wired at either end to the power supply (MDU) and the plant, for example, a hoist power supply.

It is a particular feature of the present invention that standard lengths of the cables shown in figure 4 will be held in stock. As each has an inlet and outlet connector at opposite ends, a cable of the correct length may be formed by coupling a series of cables of the appropriate diameter together to form a cable of the required length.

Armoured cables are used in construction sites because they provide a high level of protection against damage to the power carrying wires, any cable over 110 8 volts is required to have this protection. Such cables are constructed of an outer sheath of closed weave metal strands surrounding an inner sheath which carries the conducting wires. The cables must comply with the British or other relevant, standards.

Safety is an overriding factor and, in a preferred embodiment, the electrical connectors used in the invention are constituted by safety connectors, that is, connectors that will not come apart unintentionally without some fixing being removed, or a lock opened. For example, the connectors might be fixed by a retaining clip with lock, by a through fixing, or by means of a plastic wrap which encloses the coupled connectors.

Figures 5 and 5a are schematic drawings showing a front view and a side sectional view respectively of a site cabin 20. The site cabin has an inlet cable 21 provided externally. The inlet cable 21 is hardwired at one end to a distribution box 40 located inside the cabin. The cable exits the cabin 20 through an opening. in this case, in the cabin wall and has an electrical connector 22 connected to the external end. The distribution box is entirely standard and has outlets for lighting and power points, for example.

The provision of the cable 21 and connector 22 means that the site cabin does not require electricians to hardwire the cabin to the MDU each time a new construction site is set up. Instead, once the MDU is installed, the site cabin 20 can be connected to the MDU 1 merely by connecting an armoured cable 17 to an outlet connector 12 of the MDU and the inlet connector 22 of the cabin inlet cable 2 1.

The tower crane and hoists of figure 1 will operate. on a similar principle to the site cabin. Each will be provided with a hardwired inlet connector for connection to 9 the MDU 1. The inlet connector is preferably provided on a short length of hardwired armoured cable. Other plant commonly found on a construction site could be provided with the hardwired inlet cable of the invention so as to be connectable to the.electrical distribut ion system in the same modular manner.

Figure 6 shows a strip light module 23 according to the invention. Although a strip light is shown in figure 6, the principle is also applicable to the hoarding lights and other internal or external lights. In figure 6 the strip light 23 is shown to which an inlet cable 24 and an outlet cable 25 have been hardwired. The cables 24 and 25 are normal 1.5 or 2mm arctic type lighting cables approximately 1 to 2m long. Inlet cable 24 has an inlet connector 26 and outlet cable 25 has an outlet connector 27.

In an embodiment the lighting is arranged in a chain as shown in Figure 7. A transformer 3 has a cable 46 approximately 1 to 2m long provided with an outlet connector 47 at one end. The transformer 3 will be described in more detail in connection with figures 8 to 10 below. A cable 48 has an inlet connector 50 and an outlet connector 49 at either end. The inlet connector 50 is connected to the outlet connector 47 of the transformer outlet cable 46. The outlet connector 49 of cable 48 is connected to an inlet connector of a lighting module 23, which may be identical to that shown in figure 6 or may be a hoarding light for example. A series of cables 48 are shown in figure 7 linking a plurality of light modules 23.

The interconnecting cables 48 will vary in length and may be stocked in standard lengths, for exarnple, 5m, 1 Om, 20m, 40 and 50m; the cables 48 may also be made to order. Safety fixings may be used and may be required in certain cases to prevent unwanted disconnection.

A transformer 3 of the invention is shown in figure 8. 'Me transformer 3 has a plurality of outlet connectors 28, an armoured inlet cable 29 and an inlet connector 30 hardwired to the transformer inlet. The transformer 3 may then be connected to the MDU, or to another transformer, by simply attaching an armoured cable 17 (figure 4). As shown in figures 8 and 9, more than one cable may be used and each such cable has an inlet and an outlet connector. The cables 17 may be of identical lengths or may be selected from standard lengths to make up the required length. Of course a single cable of the required length may be connected directly to the MDU 1 and the transformer 3.

The transformer requirements vary on any construction site and several may be needed having differing outputs including 5, 10, 15, 20 and 25 Kva, single or three phase, 240 or 415 volt with varying protection systems including MCB or RCD. The transformers may have varying configurations of outputs such as three times 16amp sockets and 2 times 32 amp sockets, for example.

Figure 9 shows two transformers 3 each connected to the MDU 1 directly by one or more cables 17. Figure 10 shows a series of transformers connected to the MDU 1 in a chain arrangement where the transformers 3 are connected via armoured cables 17 in turn to form a series of transformers. The diameter of the cables 17 will depend on the maximum load they are required to carry.

A schematic diagram of an internal electrical system is shown in figure 11. Such a system is required when a site accommodation is required inside existing buildings to wire up rooms to provide the necessary power and lighting. The system 11 includes a standard mains distribution panel 34 with MC13s 35 of a number and rating chosen to suit the purpose of on the panel, which may be a 4- way or 6-way panel. The panel is controlled by a mains isolator switch 36. The power supply is provided frorn the MDU 1 by means of one or more armoured cable 17 according to the invention. The outlet connector 18 of the armoured cable 17 is connected to an armoured cable 21 hardwired to the distribution panel 34.

From the distribution panel 34, cables 39 (typically 1.5mrn or 2.5 mm arctic type) are either hard wired to the distribution panel or are connected thereto by a two part electrical connector. A lighting ring main is formed by connecting cables 32 having inlet and outlet connectors at either end. The cables 32 are connected between light modules 37, which may be identical to the modules shown in figure 6 and form two-part connections 52 with the inlet and outlet connectors of the light modules. In figure 11, the lighting ring main is made up of connecting cables 32 and is connected.to the distribution panel by way of a cable 39 of the distribution panel.

A power ring main is arranged in a similar fashion to the lighting ring and consists of power outlet sockets 38 (e.g. single, or two gang etc.) having connecting cables providing inlet and outlet connectors which form two-part connections 52 with connecting cables 3 1. Again, connecting cables 31 are connected to the MDP by cables 39.

Single appliances, e.g. a tea urn 33 may be provided and connected individually to the MDP with cables 32 and connectors 52 being used to provide power at the required location.

The cables 39 are preferably provided on the distribution panel 34 on construction at the factory.

12 The arrangement shown in figure 11 is a simplification. The cables 31, 32 may vary in length to suit the project requirements from say 1 m to 50m and the cables may be stocked in standard lengths of say, 1, 2, 5, 10, 20 and 50m to provide a modular system.

The modular system according to the invention has many advantages. Namely it is reusable and easier to adapt to changing circumstances. It is easier and quicker to install on site and to make changes as necessary. The time consumed in hardwiring is eliminated or substantially reduced. There is no need to call an electrician in every time it is required to rearrange the site installation. Plant can be moved or added as required simply by plugging and unplugging the different modules.

Whilst embodiments have been described variations will suggest themselves to those skilled in the art without departing from the scope of the invention as defined in the appended claims.

13

Claims (10)

1. A temporary electrical installation for a construction site comprising a mains distribution unit, at least one item of plant, and at least one armoured cable having an electrical connector at each end; wherein the mains distribution unit has a plurality of electrical connectors hardwired thereto and providing a plurality of power outlets at differing ratings; said at least one item of plant has an electrical connector hardwired thereto providing a power inlet; said at least one armoured cable having one end connectable to a power outlet connector of the mains distribution unit and one end connectable to the power inlet connector of the item of plant.

2. A temporary electrical installation as claimed in claim 1, wherein said mains distribution unit has a plurality of cables hardwired thereto and said power outlet connectors are provided at the end of said cables.

3. A temporary electrical installation as claimed in claim 1 or 2, wherein said at least one item of plant is one, or more than one, of a mains distribution panel, a site cabin, a temporary lift, tower crane supply, a compressor, a cube tank, a flood light supply, a temporary lift supply, a batching plant, a pump, and a supply for a drilling apparatus or welding supply.

14

4. A temporary electrical installation as claimed in claim 1, 2 or 3, wherein each of said electrical connectors of said mains distribution unit, said at least one item of plant and said at least one armoured cable, comprises one half of a two-part Insulated electrical connector, said two-part connector comprising a safety means for preventing accidental disconnection of the two-part connector.

5. A temporary electrical installation as claimed in claim 4, wherein said safety means, comprises a retaining clip, a through fixing, a web or tape wrapped around the connector.

6. A temporary electrical installation as claimed in any one previous claim, wherein the connectors of said at least one armoured cable are complementars' halves of a two-part an electrical connector.

7. A temporary electrical installation as claimed in any one of claims 1 to 5, wherein the connectors of said at least one armoured cable are the same at each end.

8. A method of installing a temporary electrical installation for a construction site comprising providing a mains distribution unit, at least one item of plant. and at least one armoured cable having complementary halves of a two-part electrical connector at its ends; wherein the mains distribution unit has a plurality of electrical connectors hardwired thereto and providing a plurality of power outlets at differing ratings; said at least one item of plant has an electrical connector hardwired thereto providing a power inlet; connecting one end of said at least one armoured cable to a power outlet connector of the mains distribution unit and connecting the other end to the power inlet connector of the item of plant.

9. A temporary electrical installation for a construction site as hereinbefore described with reference to the accompanying drawings.

10. A method of installing a temporary electrical installation for a construction site as hereinbefore described with reference to the accompanying drawings.