GB2500739A

GB2500739A - Isolation and distribution box for railway signalling allowing part shutdown for live working

Info

Publication number: GB2500739A
Application number: GB1216299.6A
Authority: GB
Inventors: Darron Jones; Paul Legrys
Original assignee: Control Systems & Equipment Ltd
Current assignee: Control Systems & Equipment Ltd
Priority date: 2012-03-23
Filing date: 2012-09-12
Publication date: 2013-10-02
Also published as: GB2500435A; GB201205157D0; GB201216299D0

Abstract

A electrical isolation and distribution enclosure 10 comprises a lower housing 12 for terminating upstream and/or downstream large diameter power cables, such as those used in railway signalling. An upper housing 14 carries a bank of control switches 70 and fuse carriers 72 and is hinged to the lower housing 12 so that it closed over the lower housing. The upper housing has an access lid 16, and a retainer means to secure the upper housing closed on to the lower housing. The lower housing 12 has a partitioning element 24 forming two cable-terminating compartments 30, 32. and access covers 34, 36 close each of these 30, 32, respectively. These lower access covers are themselves covered when the upper housing 14 is closed. This arrangement can be used to allow selective isolation of only some upstream and/or downstream large diameter power cables in a railway signalling system, so that some cables can be repaired or replaced while others are still live. Preferably, the lower housing 12 has electrically insulating interior and exterior surfaces, partitioning element 24 and access covers 34, 36 so that the box can provide double insulation. These parts may be made from plastic coated metal. An exploded view is shown in figure 9.

Description

I

Electrical Isolation And Distribution Enclosure The present invention relates to an electncal isolation and distribution enclosure, to a method of distributing power to a railway signalling system using such an enclosure.

and to a method of using such an enclosure to sdectively dectrically isolate upstream andlor downstream large diameter power cables feeding e'ectrical components of a railway signalling system.

It is a requirement, especially for railway signalling systems, to provide long lengths of power cable. To reduce voltage drop over long distances, the power cables which terminate at local distribution boxes have large diameters, typically in the order of 30 mm or more. The diameter of the local power cables from the distnbution box to the signalling system is typically much smaller, in the order of 16 mm, due to the shorter distance.

However, cable theft, particularly of the large diameter long distance power cables, is an increasing problem. The conductor materials of the power cables are valuable, thereby leading to unauthorised and hazardous removal andlor damage by third parties.

This not only inconveniences the travelling public by disabling the associated signalling systems, but repair costs are significant and can be time consuming.

Presently, the long distance large diameter power cables require earthing facilities, and as such armoured three core cables are utilised. These are expensive and heavy, thus being cumbersome and difficult to install and replace.

It is therefore a requirement to be able to safely utilise unarmoured two core power cable which dispenses with the need for earthing. Although significantly more cost-effective and simpler to install and replace, any electrical system without earthing presents potential senous electncal hazards.

It is also a requirement to be able to utilise power cables which may be earthed.

Furthermore, at present, when replacing a large diameter power cable at a distribution box, both an incoming feed and an outgoing feed must be electrically isolated if there is no earth present. This inevitably results in the entire associated signalling system or other dectrical system being supplied to be deenergised.

Additiona'ly, plastics distribution boxes cannot be utilised iii enclosed spaces, such as tunnels and underground railway systems. This is due to possible toxic fumes and the release of other hazardous chemicals into the air should the distribution box be subjected to excessive heat or fire.

The present invention seeks to overcome these problems.

According to a first aspect of the invention, there is provided an electrical isolation and distribution enclosure comprising a lower housing for terminating upstream andlor downstream large diameter power cables as herein defined, an upper housing which is hinged to the lower housing and which includes at least a bank of control switches and a bank of fuses, a retainer for releasably retaining the upper housing in a closed condition on the lower housing, and an access lid for preventing or limiting access to the upper housing, the or a further retainer retaining the access lid in a closed condition on the upper housing. the lower housing having interior and exterior surfaces and a partitioning element whereby two cable-terminating compartments are defined in the lower housing.

and first and second access covers which close the two cable-terminating compartments, respectively, the upper housing when closed overlying the first and second access covers.

Preferable and/or optional features of the first aspect of the invention are set forth in claims 2 to 16, inclusive.

According to a second aspect of the invention, there is provided a method of distributing power to a railway signa'ling system, the method comprising the steps of: a] aying two core unarmoured large diameter power cable to an electrical isolation and distribution enclosure in accordance with the first aspect of the invention; b] terminating the arge diameter power cable in a said cable-terminating compartment of the lower housing of the enclosure; c] electrically connecting an internal smaller diameter power cable from the terminated large diameter power cable with a said control switch and/or fuse of the upper housing; dl electrically connecting an external smaller diameter power cable from said control switch and/or fuse to a railway signalling system exterior of the enclosure; and ci closing the caNe-terminating compartment by its said access cover, and closing and securing the upper housing to the lower housing, so that the upper housing overlies the said access cover.

According to a third aspect of the invention, there is provided a method of using an electrical isolation and distribution enclosure according to the first aspect of the invention to selectively electrically isolate upstream and/or downstream large diameter power cables feeding electrical components of a railway signalling system, the method comprising the steps of: a] electrically isolating a terminal for an incoming andlor outgoing large diameter power cable in the respective cable-terminating compartment via its respective control switch; b] releasing and hinging the upper housing away from the lower housing; c] removing the respective access cover to access the required cable-terminating compartment; d] connecting a large diameter power cable to the said terminal; e] replacing the access cover, and closing and securing the upper housing; and 1] electrically reconnecting the said terminal to the railway signalling system by turning on the respective control switch, whereby another terminal in the other said cable-terminating compartment can remain live during steps a] to f].

Preferable and/or optional features of the third aspect of the invention are set forth in any one of daims 20 to 23.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings. in which: Figure 1 shows a side elevational view of a first embodiment of an electrical isolation and distribution enclosure, in accordance with the first aspect of the invention and shown with an upper housing hinged open relative to a lower housing, and an access lid hinged open relative to the upper housing; Figure 2 shows a side elevational view which is similar to Figure 1. but with the upper housing and the access lid both hinged to closed positions; and Figure 3 shows a top plan view of the electrical isolation and distribution enclosure, shown in figure 1; Figure 4 is a top plan view, similar to Figure 3, but with the upper housing removed and two electricafly-insulative access covers partiaHy sectioned to show two cable-terminating compartments within the lower housing of the enclosure; Figure 5 is a side elevational view from another side of the enclosure, and showing small-diameter power cable openings for feeding electrical components of a railway signalling system; Figure 6 shows a front perspective view of the electrical isolation and distribution enclosure, in a fully closed condition; Figure 7 shows a front perspective view of the electrical isolation and distribution enclosure, in a partially open condition; Figure 8 shows a front perspective view of a second embodiment of an electrical isolation and distribution enclosure, in accordance with the first aspect of the invention and shown in a fully closed condition; and Figure 9 shows the electrical isolation and distribution enclosure of Figure 8 in a fully open condition.

Referring firstly to Figures 1 to 7 of the drawings, there is shown a first embodiment of an electrical isolation and distribution enclosure lO, which in this case is double insulated and which comprises a lower housing 12, an upper housing 14, and an access lid 16. The enclosure 10 is preferably formed of metal plate, such as mild steel, overcoated on the interior and exterior surfaces with a durable plastics electricafly-insulative coating 18, for example, PPAS71 manufactured by Plascoat Systems Limited of Farnharn Industrial Estate, Farnham, Surrey, 0U9 9NY, UK. PPA571 is suitable due to being devoid of Bisphenol A BPA, PVC. halogens, phthalates and heavy metals.

Consequently, unlike traditional fully plastics enclosures, the enclosure 10 of the present invention meets requirements for location in covered or enclosed areas, such as tunnels and in underground or subway railway systems. Traditional fully plastics enclosures, if subjected to excessive heat or fire, may release toxic or hazardous chemicals.

However, for above ground or open-air use, the enclosure of the present invention may utilise fully plastics electricafly-insulative panels, instead of plastics-overcoated metal plates. Other electrically-insulative materials may also be considered.

The lower housing 12, as best seen in Figure 3, includes a uniformly solid base 20, four contiguous walls 22 upstanding from a perimeter of the base 20, and a partitioning element 24 which in this case bisects the lower housing 12, extends from a front said wall 26 to a rear said wall 28 and upstands from the base 20. The partitioning element 24 is also electrically-insulative being in this case a metal plate fully overcoated with the aforementioned plastics.

The lower housing 12 is thus divided into two cable-terminating compartments 30, 32 by the partitioning element 24, and first and second electrically-insulative access covers 34, 36 are provided for closing each of the cable-terminating compartments As with the partitioning element 24, each access cover 34, 36 is preferably a uniformly solid metal plate overcoated with non-electrically conductive plastics. Each access IS cover 34,36 is dimensioned to seat on an upper edge or shoulder of the respective walls 22 and partitioning element 24 defining each cable-terminating compartment 30, 32.

Each cable-terminating compartment 30, 32 can thus be or substantially be electrically isolated from its surroundings and from the other cable-terminating compartment 30, 32.

Preferably, the partitioning element 24 includes an access aperture allowing cable passage from a first one of the caNe-terminating compartments 30 to a second one of the cable-terminating compartments 32. Furthermore, the second access cover 36 of the second cable-terminating compartment 32 preferably includes a cable-access opening 40, in this case being a cut-out or recess in an edge, allowing cable passage between the upper housing 14 and the lower housing 12. The access aperture in the partitioning element 24 and the cable-access opening 40 in the second access cover 36 are preferably dimensioned to receive as a close fit or dght fit a small diameter power cable. Rubber or elastomeric glands may be utilised in the access aperture and/or the cable-access opening 40 to close the openings around the respective cables, thereby improving the electrical isolation.

The use of the phrases small diameter' and small power cable' used herein and throughout and in connection with a size of a power cable or its core is intended to mean power cables having an outside diameter in the range of 10 mm to 25 mm, and more preferably at least substantially 16 mm. The use of the phrases large diameter' and large power cable' used herein and throughout and in connection with a size of a powcr cablc or its corc is intcndcd to mean power cables having an outside diameter in the range of 26 mm to 150 mm, and more preferably substantially 50 mm.

A right side wall 42 of the lower housing 12, in this case forming part of the second cable-terminating compartment 32 includes one or more, and in this case three, small cable access apertures 44 for receiving outgoing and incoming small power cables. Such small power cables, in this case, supply one or more railway signafling systems and/or their associated electrical components, such as transformers and points heating systems.

Beneficially. the small cable access apertures 44 are located in the right side wall 42 beneath the cable-access opening 40, thus providing a most direct route from the upper housing 14.

Preferably, further glands may be provided in the small cable access apertures 44 for sealing and further improving the electrical isolation of the second cable-terminating compartment 32.

To provide access for upstream and downstream large power cables, each cable-terminating compartment 30, 32 ineudes a large cable access aperture 46. Even though the large power cables to be used with the enclosure 10 of the present invention are intended to be unarmoured two core cables, and therefore of somewhat smaller core diameter than the traditional aimoured three core power cables, the unarmoured two core cables are still cumbersome, heavy and relatively resilient to bending.

Advantageously, therefore, the front wall 26 of the lower housing 12 can be at least in part temporarily dismantled. The front wall 26 includes a lowermost wall element 48 having first recesses 50 forming part of the large cable access apertures 46 in an upper edge thereof, and two upper wall elements 52 which are seatable on the upper edge of the lowermost wall element 48. The lowermost wall element 48 extends between the left and right side walls 42, 54 and thus across the two cable-terminating compartments 30, 32. It may not be removable. The removable two upper wall elements 52 each close a respective one of the first and second cable-terminating compartments 30, 32.

Each upper wall dement 52 includes a second recess 56 in its lower edge. The first and second recesses 50, 56 match to define the respective large cable access aperture 46.

Screw ports for screw-threaded fasteners 58 are provided in the two cable-terminating compartments 30, 32, around the perimeter of the front wall 26, so that the upper wall elements 52 can be releasably fastened in place. The screw ports are electrically insulated to prevent a potential electrical shock hazard during removal and replacement.

However, other fastening means may be considered for retaining the upper wall elements 52 in place, such as channels for captively sliding the upper wall elements 52 therealong, or pivotable catches.

As before, each of the large cable access apertures 46 may include a gland for closing the aperture 46 around the large power caNe once located therein.

To electrically terminate an end of a large power cable in each cable-terminating compartment 30, 32, first and second heavy-duty teirninals 60 are provided fixed to the base 20. Electrically-insulative caps may also be provided which cover the terminals 60, thereby further shielding the terminals 60 during access.

Flange plates or brackets 62 may be provided on an exterior of the lower housing 12, in this case at or adjacent to an upper edge of the left and right side walls 42, 54. This enables secure mounting of the enclosure 10 at an installation site.

The upper housing 14 compnses a base 64 and four contiguous walls 66 which upstand from a perimeter of the base 64. The walls 66 of the upper housing 14 are preferably lower than those of the lower housing 12, providing a sUmmer upper container.

As with the lower housing 12, all panels are electrically-insulative at least on the interior and preferably also on the exterior surfaces. Metal plate overcoated with non-electrically conductive plastics is preferred, thereby enabling use in covered areas, but again the panels may be fully plastics if only to be used in open and uncovered installation sites.

The upper housing 14 is hinged at a lower edge of its right side wall 42 to an upper edge of the right side wall 42 of the lower housing 12, as best seen in Figure 5 and understood from Figure 1. The hinges 68 used may be plastics. for example, polyamide, or metal. Again, this is beneficial as it enables the most direct route for small power cables to run between the upper and lower housings 12, 14, without requiring significant extension or slack to be availaNe when pivoting open the upper housing 14.

A footprint of the upper housing 14 is dimensioned to match or substantially match that of the lower housing 12, so that in a closed condition the upper housing 14 overlies the lower housing 12. In such a closed condition, the upper housing 14 therefore sits over the first and second access covers 34, .36.

The upper housing 14 is adapted to house at least a bank of control switches 70 and a bank of fuse carriers 72 for fuses, along with preferably an electrical surge protection device and a bus bar. First and second control switches 74, 76 provide for electrical isolation of the terminals 60 in the first and second cable-terminating compartments 30, IS 32, and the remaining control switches 78 provide for electrical isolation of electrical components being fed by the small power cables exiting the lower housing 12 via the small cable access apertures 44.

The control switches 70 may be lockable in an ON and/or OFF condition. For example, each grip portion of the switch 70 may include an aperture, and a base portion may include one or more spaced apart apertures. Once the grip portion is moved to a certain position, the apertures align thereby allowing a lock, such as a padlock, to be inserted.

This is beneficial in that it prevents or limits the possibility of the switch being inadvertently operated whilst the lower andlor upper housings are being accessed.

The control switches 70 and preferably also the fuses on the fuse cawiers 72 are accessible from the top of the upper housing 14 and through openings 80, 82 in the aforementioned access lid 16.

The access lid 16, as with the lower and upper housings 12, 14, is electrically insulated and preferably formed of metal plate overcoated with the previously mentioned suitable plastics. The access lid 16 is preferably hinged on an opposite side to the hinging of the upper housing 14. However, hinging on another side is feasible.

A switch opening 80 and a fuse opening 82 are formed in the access lid 16, and these openings 80. 82 are dimensioned to closely fit around the bank of control switches 70 and the bank of fuse carriers 72, respectively. The access lid 16 therefore closes off unhindered access to the other elements, such as the associated terminals and the bus bar, if included.

The access lid 16 is preferably lockable to prevent or limit unauthorised opening. In this case, the access lid 16 is lockable to the upper housing 14 by an independent locking device 84. Although a locking device is suggested, any suitable retainer can be utilised whereby the access lid 16 is releasably securable in its closed condition. For example, the retainer cou'd be a swing plate operaNe by a screwdriver or a detent.

Additionally, the upper housing 14 is lockable to the lower housing 12, again to prevent or limit unauthorised opening. This further locking device is preferably accessible through an opening 86 in the access lid 16, thereby dispensing with the need to first open the access lid 16 in order to access the cable-terminating compartments 30, 32.

The further locking device of the upper housing 12 is preferably separate of the locking device of the access lid 16 for the safety reasons already mentioned. Although again a locking device is suggested, any suitable retainer can be utilised whereby the upper housing 14 is releasably securable in its closed condition to the lower housing 12. For example, the retainer could be a swing plate operable by a screwdriver or a detent.

The two retainers mentioned may be independent of each other, or may be combined together to simultaneously lock or secure the access lid and upper housing.

To install the double-insulated electrical isolation and distribution enclosure 10, the lower housing 12 is fixedly mounted at the installation site via the flange plates or brackets 62. With the upper housing 14 open and the access covers 34, 36 removed, upstream and downstream large power cables are inserted into respective cable-terminating compartments 30, 32 via the large cable access apertures 46. This process is simplified by the removal of the multi-part front wall 26, if necessary. The upstream and downstream power cables may be an incoming and an outgoing power cable, or two incoming power cables.

The large power cables are connected to the terminals 60, and the optional insulative caps are fitted to the terminals 60. A small power cable is run from the terminal 60 in the first cable-terminating compartment 30, 32, through the partitioning element 24 and together with a small power cable from the terminal 60 in the second cable-terminating compartment 30, 32 through the cable-access opening 40 in the second access cover 34, 36. The small power cables are fed into the upper housing 14. Further small power cables from the upper housing 14, through the cable-access opening 40 and out through the small caNe access apertures 44 provide power to the associated railway signalling systems or other electrical components external of the enclosure 10.

The access covers 34, 36, once in place and dosing their respective caNe-terminating compartments 30, 32, are secured by having the upper housing 14 hinged down to seat thereon and then locked.

In the case when the enclosure 10 is at the end of a power cable run, only one of the cable-terminating compartments 30, 32 may be utilised. Therefore, blanking plates may be utilised to close any access apertures in the walls 66 of the lower housing 12 not being used.

In the event of a problem with one, other or both upstream and downstream large power cables, for example, due to unauthorised tampering, removal, damage or vandalism, the respective terminal 60 can be selectively isolated via its control switch 74, 76. The upper housing 14 is unlocked and hinged open, and the relevant access cover 34, 36 removed to open the cable-terminating compartment 30, 32. Due to the electrically-insulative and isolating structures of the two cable-terminating compartments 30, 32 and the use of the electrically-insulative access covers 34, 36, in the event of only one large power cable requiring repair or replacement, the other large power cable can remain live and thus the associated external electrical systems operational.

The respective terminal 60 can thus be uncapped, the existing large power cable removed, and a new large power cable inserted and connected. The access cover 34, 36 ii is then replaced, and the upper housing 14 hinged closed and locked to securely shut the lower housing 12. The respective control switch 74, 76 is then turned on to reenergise the terminal 60 and associated external electrical components.

Referring now to Figures 8 and 9 of the drawings. there is shown a second embodiment of an electrical isolation and distribution enclosure. References which are identical to those of the first embodiment refer to the same or similar parts, and therefore further

detailed description is omitted.

The electrical isolation and distribution enclosure 10 of this second embodiment comprises a lower housing 12, an upper housing 14, and an access lid 16. The enclosure 10 may be formed of metal plate, such as mild steel, but in this case is not overcoated with electrically insulative materiaL The lower housing 12 is divided into the two cable-terminating compartments 30, 32 by the partitioning element 24. First and second non-electrically-insulative access covers 34, 36 are provided for closing each of the cable-terminating compartments 30, 32.

The upper housing 14 is hinged at a lower edge to an upper edge of the lower housing 12, and is adapted to house at least a bank of control switches 70 and a bank of fuse carriers 72 for fuses, along with preferably an electrical surge protection device and a bus bar. First and second control switches 74, 76 provide for electncal isolation of the terminals 60 in the first and second cable-terminating compartments 30, 32, and the remaining control switches 78 provide for electrical isolation of electrical components being fed by the small power cables exiting the lower housing 12.

The access lid 16, as in the first embodiment, is preferably hinged on an opposite side to the hinging of the upper housing 14, and a switch opening 80 and a fuse opening 82 are formed in the access lid 16.

The upper housing 14 is lockable to the lower housing i2, again to prevent or limit unauthorised opening.

In this embodiment, an earth terminal 90 is provided on the lower housing 12.

The switch opening and the fuse opening of the access lid in the above embodiments are preferably sized dependent on the number of control switches and fuse camers.

Although five control switches are shown, two to four or more than five control switches and respective fuse carriers can be utilised.

Although the electrical isolation and distribution enclosure described above is ideally suited for railway signalling systems, it may also be used in other environments for supplying power to electrical components.

It is thus possible to provide an electrical isolation and distribution enclosure which meets Class I and, in the case of the tirst embodiment, Class II requirements. The enclosure provides selective isolation of upstream and downstream electrical supplies, thereby dispensing with the need to electrically deenergise all electrically connected external systems and components during maintenance and repair procedures and thus minimising disruption to associated signalling equipment or other electncal components.

It is also possible to provide, in the case of the first embodiment, an unearthed enclosure IS which meets or exceeds requirements for safe installation and usage at underground or covered sites. Furthermore, it is possible to provide an electrical isolation and distribufion enclosure which can preferably operate at up to 690 volts or more, whereby large diameter core power cables can be terminated and smaller diameter core power cables or spurs can feed local electrical equipment via dedicated isolation control switches. By providing a double-insulated segregated enclosure in the first embodiment, less expensive large diameter unarmoured two core power cable can be utilised during initial installation or as a replacement for large diameter armoured three-core power cable.

Claims

Claims 1. An electrical isolation and distribution enclosure comprising a lower housing for terminating upstream and/or downstream large diameter power cables as herein defined, an upper housing which is hinged to the lower housing and which includes at least a bank of control switches and a bank of fuses, a retainer for releasably retaining the upper housing in a closed condition on the lower housing, and an access lid for preventing or limiting access to the upper housing, the or a further retainer retaining the access lid in a closed condition on the upper housing, the lower housing having interior and exterior surfaces and a partitioning dement whereby two cable-terminating compartments are defined in the thwer housing. and first and second access covers which dose the two cable-terminating compartments, respectively, the upper housing when closed overlying the first and second access covers.
2. An electrical isolation and distribution enclosure as claimed in claim 1, wherein IS a retaining mechanism for releasably securing the upper housing to the lower housing is accessible through the closed access lid.
3. An electrical isolation and distribution enclosure as claimed in claim 1 or claim 2, wherein the access lid is hinged to the upper housing.
4. An electrical isolation and distribution enclosure as claimed in claim 3, wherein the access lid is hinged on an opposite side to the hinging of the upper housing.
5. An electrical isolation and distribution enclosure as claimed in any one of claim I to 4. wherein a side wall of the lower housing at each cable-terminating compartment includes a cable-access opening for an incoming and/or outgoing large diameter power cable.
6. An electrical isolation and distribution enclosure as claimed in claim 5, wherein the cable-access opening includes a cable g'and.
7. An electrical isolation and distribution enclosure as claimed in claim 5 or claim 6, wherein the side wall includes a removable panel for enabling location of the large diameter power cable in at least part of the cable-access opening.
8. An electrical isolation and distribution enclosure as claimed in any one of claims 1 to 7, wherein each cable-terminating compartment includes a terminal block for elecica1ly connecting an incoming or outgoing large diameter power cable, the termina' block being secured to an interior surface of its respective cable-terminating compartment.
9. An electrical isolation and distribution enclosure as claimed in claim 8, wherein each terminal block includes a removable electrically-insulative cap.
10. An electrical isolation and distribution enclosure as claimed in any one of claims 1 to 9, wherein at least one of the first and second access covers includes a smaller-diameter cable opening for electrical-caNe communication between the upper housing and the cable-terminating compartments.
11. An electrical isolation and distribution enclosure as claimed in any one of claims 1 to 10, wherein the partitioning element includes a further smaller-diameter cable opening for electrical-cable communication between the two cable-terminating compartments.
12. An electrical isolation and distribution enclosure as claimed in any one of claims 1 to 11, wherein a side wall of the lower housing includes a further cable-access opening for an incoming and/or outgoing small diameter power cable in electrical communication with at least one said control switch and/or said fuse of the upper housing.
13. An electrical isolation and distribution enclosure as claimed in any one of claims 1 to 12, wherein the lower housing, upper housing and lid are formed of metal p'ate coated with an electrically-insulative p'astics coating.
14. An electrical isolation and distribution enclosure as claimed in any one of claims I to 13, wherein the enclosure is double insulated.
15. An electrical isolation and distribution enclosure as claimed in any one of claims I to 1 4, wherein the interior and exterior surfaces and partitioning element of the lower housing are electrically insulative.
16. An electrical isolation and distribution enclosure as claimed in any one of claims 1 to 15, wherein the first and second access covers are electrically insulative.
17. An electrical isolation and distribution enclosure substantially as hereinbefore described with reference to Figures 1 to 7, or Figures 8 and 9 of the accompanying drawings.
18. A method of distributing power to a railway signalling system, the method comprising the steps of: al laying two core unarmoured large diameter power cable to an electrical isolation and distribution enclosure as claimed in any one of the preceding claims; bi terminadng the large diameter power cable in a said cable-terminating compartment of the lower housing of the enclosure; c] electrically connecting an internal smaller diameter power cable from the terminated large diameter power cable with a said control switch and/or fuse of the upper housing; d] electrically connecting an external smafler diameter power cable from said control switch andlor fuse to a railway signalling system exterior of the enclosure; and ci closing the cable-terminating compartment by its said access cover, and closing and securing the upper housing to the lower housing, so that the upper housing overlies the said access cover.
19. A method of using an electrical isolation and distribution enclosure as claimed in any one of claims 1 to 14 to selectively electrically isolate upstream andlor downstream large diameter power cables feeding electrical components of a railway signalling system, the method comprising the steps of: a] electrically isolating a terminal for an incoming andJor outgoing large diameter power cable in the respective cable-terminating compartment via its respective control switch; fri releasing and hinging the upper housing away from the lower housing; ci removing the respective access cover to access the required cable-terminating compartment; di connecting a large diameter power cable to the said terminal; ci replacing the access cover, and closing and securing the upper housing; and I] electrically reconnecting the said terminal to the railway signalling system by turning on the respective control switch, whereby another terminal in the other said cable-terminating compartment can remain live during steps a] to t].
20. A method as claimed in claim 19, wherein, subsequent to step a], the large diameter power cable is damaged or at least in part removed.
21. A method as claimed in claim 19 or daim 20, wherein, in step d], an existing large diameter power cable is disconnected from the terminal and a new large diameter power cable is connected to the terminal.
22. A method as claimed in any one of claims 19 to 21, wherein, in step d], the large diameter caNe is unarmoured and two core.
23. A method as claimed in any one of claims 19 to 22, wherein, in step f], the other terminal in the other said cable-terminating compartment can remain live during steps a] to 1 without there being an electrical shock hazard.