GB2320985A

GB2320985A - Power cut-out safety device

Info

Publication number: GB2320985A
Application number: GB9724985A
Authority: GB
Inventors: Alan James Hobbs
Original assignee: ELECTRICAL TESTING Ltd
Current assignee: ELECTRICAL TESTING Ltd
Priority date: 1996-11-29
Filing date: 1997-11-27
Publication date: 1998-07-08
Anticipated expiration: 2017-11-27
Also published as: GB9724985D0; GB2320985B; GB9624912D0

Abstract

A power cut-out device 1 of the type used in street lighting columns and signs is rendered safe by mounting a rigid and robust cover 3 over the cut-out device in a secure manner to thereby prevent direct access to the cut-out device without the use of tools. The cover is open on one face to fit over the cut-out device and has means (4,9, Fig 2) on at least one edge for securing the cover to a backboard 2 on which the cut-out device is mounted. An additional fused isolator device 5 is connected in series with the existing cut-out device. The arrangement avoids the risk of fatal electric shock to maintenance workers while avoiding the expensive existing procedure.

Description

POWER CUT-OUT SAFETY DEVICE Field of the Invention The present invention relates to a method of rendering safe a street lighting fused isolation device of the type installed by Regional Electricity Companies (RECs) commonly known as a cut-out. The invention also relates to apparatus for use in the method.

Background to the Invention Over six million street lighting columns and signs are installed throughout the United Kingdom and much of the stock is old, underfunded and in poor and in many cases dangerous condition. More than 90% of this stock is supplied by networks owned and controlled directly by the RECs.

An REC cut-out is essentially a fuse carrying protection and isolation unit, designed to interrupt the power supply in the event of an electrical fault on an item of street lighting equipment and also to provide isolation whilst work may be carried out on an item of street lighting equipment. It is standard practice to house the cut-out within the column of the street light in which the cut-out may be accessed via a hatch in the body of the column. However because the cut-out is housed within a confined space, surrounded by exposed earthed metalwork, it is not permitted to replace a damaged cut-out without the need for the REC to isolate the electrical supply. To avoid the disruption of the electrical supply to many homes and factories the preferred method is for the REC to excavate the ground in the immediate vicinity of the street lighting column or sign in order to intercept the mains electricity cable coming from the sub-station before it enters into the base of the column to thereby enable the cable to be cut to electrically isolate the street light or sign before a replacement cut-out is installed. This work is permitted under live working conditions. As will be appreciated, this approach is very expensive and leads to costs of the order of 300 to replace a single cut-out.

Nonetheless, inspections carried out over recent years have identified that over half of the UK's lighting stock could have cut-outs in un-safe condition due to wear and tear and inadequate maintenance.

It is a general objective of the present invention to provide an alternative method of making safe an REC cut-out avoiding the need to replace the cut-out while meeting stringent safety standards and vastly cutting the cost of the very necessary work.

Throughout this patent specification, reference to a "fuse'' is intended to include reference to other circuit breaking devices, for example a miniature circuit breaker ("MCB").

Summarv of the Invention According to a first aspect of the present invention there is provided a method of rendering safe a power cut-out device of the type used in street lighting columns and signs (commonly known as an REC cut-out), which method comprises the steps of: mounting over the existing cut-out device a rigid and robust cover in a secure manner to thereby prevent direct access to the existing cut-out without use of tools.

Preferably, the method comprises the further steps of providing an additional fused isolation device, wiring it in series to the existing cut-out device between the existing cut-out device and the load. By adopting this method the existing cutout is rendered safe - no longer posing a risk of fatal electric shock to maintenance workers while avoiding the extremely expensive existing procedure which, in fact, is in many cases not being carried out due to cost.

According to a second aspect of the present invention there is provided apparatus for use in the method of the invention and which comprises a substantially boxshaped cover open on one face to fit closely over an REC cut-out device and having means on at least one edge by means of which the cover may be secured to the conventional back-board on which the REC cut-out is mounted.

Preferably, the cover comprises a first section which, before use, can be trimmed to a desired length and depth and a second section which, before use, can also be so trimmed, the two sections, in use, fitting closely together to form the complete cover which is not disassemblable without use of tools.

Advantageously, the cover has apertures in the sides thereof that, in use. closely accommodate the incoming mains wire and outgoing wires leading to a said additional fused isolation device.

Ideally, the cover is made of a robust and rigid flame retardent plastics material In a preferred form, the cover is transparent to enable the existing REC cut-out device enclosed by the cover in use to be viewed in-situ.

The invention is intended to include within its scope an apparatus substantially as herein before described with reference to any appropriate combination of the drawings.

The invention is also intended to include within its scope a method of rendering safe a power cut-out device substantially as herein before described with reference to any appropriate combination of the accompanying drawings.

Brief Description of the Drawinos A preferred embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, wherein: Figure I is a schematic plan view of an existing REC cut-out installation rendered safe in accordance with the method of the present invention, and Figure 2 is a perspective view of a cover embodying the apparatus of the present invention.

Figure 3 is an exploded perspective view of a second cover embodying the apparatus of the present invention.

Description of the Preferred Embodiment Referring to Figure 1, this shows a conventional REC cut-out device 1 mounted in conventional manner by screws to a wooden back-board 2 which is in turn, fastened to the interior of the lighting column, in use. This cut-out device 1 is a large fuse isolation unit having a moulded body with a detachable lid portion in which the fuse is gripped so that when the lid is detached from the main part of the body the lighting appliance is thereby isolated from the mains supply. A characteristic of the general defects of the body of the cut-out is the presence of very large supply line apertures in the base or other parts of the cut-out or missing protective shields and which themselves constitute a safety hazard since they potentially expose the maintenance operator to risk of contact with a live conductor.

A further characteristic of the general defects of the cut-out is the presence of cracks in the body of the cut-out which present an explosion hazard if the body should collapse short-circuiting the live and neutral since currents of up to 20,000 Amps are involved.

As further illustrated in Figure 1, in accordance with the present invention, a boxshaped cover 3 is installed over the cut-out I and secured in place by screws extending through screw holes 4.

Details of the cover 3 will be described in further detail below with reference to Figures 2 and 3.

Before fitting the cover 3 to the cut-out device 1 a secondary cut-out device 5 is to be wired in series to the existing cut-out device 1 between that device 1 and the load of the appliance - ie in this case the light circuit.

Connection of the secondary fused isolation device 5 is carried out strictly by a duly authorised engineer and once the secondary cut-out device 5 is in place and the cover 3 also in place the existing REC cut-out unit is strictly prohibited from access by unauthorised personnel and suitably carries a warning notice to this effect on its front face.

Referring to Figure 2, a first embodiment of the cover 3 has a generally rectangular box-shaped form of which the back face is open to enable it to seat over the REC cut-out device 1.

An aperture 6 is provided in the lower most in use face of the cover 3 to accommodate the incoming mains cable and dimensioned to closely accommodate the cable so as to prevent access to prying fingers. Additionally, this end of the cover 3 is suitably configured to be spaced a substantial distance from the bottom end of the existing cut-out device 1 when installed upon the back-board 2 to further physically isolate the cut-out 1 A further aperture 7, 8 is provided in each opposing side wall of the cover 5 to permit egress of the live, neutral and earth cables from the existing cut-out 1 which feed to the secondary cut-out 5.

The cover 3 is securely fastened to the back-board 2 by means of screws which project through screw holes 4 in the one or more flanges 9 of the covers which lie adjacent to the back-board 2, in use.

The cover 3 is suitably formed of a toughened transparent flame retardant plastics material (such as polycarbonate) and which is of relatively thick dimensions to be extremely rigid and robust. A suitable thickness of polycarbonate is, for example, 2.5 millimetres and the further dimensions of the cover 5 are suitably of the order of 20 centimetres in length. 9 or 10 centimetres in width and 7 centimetres in depth, suitably with a gap between the lower most in use wall of the cover 5 and lower most end of the cut-out device 1 of the order of 2 centimetres or greater.

It will be appreciated that REC cut-out devices vary considerably in size, shape and condition. Installation of the secondary cut-out device 5 and/or the cover 3 may typically take place in a relatively confined space (for example, the interior of a single lamp post) and access thereto may be restricted It is therefore desirable to provide a cover 3 whose dimensions may be adapted to suit the particular installation and REC cut-out device concerned Referring to Figure 3, a second embodiment of the cover 3 is shown which may be varied in size as described below. The cover 3 has a generally rectangular boxshaped form of which the back face is open to enable it to seat over the REC cutout device 1 The edges of the cover 3 may be rounded to ease manufacture and improve the cover's aesthetic appearance.

The cover 3 is in a two-part form, having a larger upper part 3a and a smaller lower part 3b.

In use, the two parts 3a, 3b are designed to fit closely together, for example with lower part 3b being a cap-fit inside upper part 3a. Once fitted together, the two parts 3a, 3b can be held together via fixing holes 10, so that the cover 3 cannot be opened up by removal of lower part 3b without the use of a tool of some kind.

Unlike the cover of Figure 2, the embodiment shown in Figure 3 is not provided with flanges 9. Instead, each part of the cover 3a 3b is provided with two fixing tabs 11 which protrude from the general body of the cover as shown in Figure 3.

Each fixing tab 11 is provided with a screw-hole 4 for use as described above.

Suitable dimensions for the fixing tabs 11 are 15x10x15mm.

During installation, the upper part 3a ofthe cover may be trimmed to a convenient length by cutting off a portion from the lowermost edge L. The depth of the cover 3 may be reduced by trimming material from the region marked D in Figure 3. In this way, cover 3 may be adapted for use with various differently-sized REC cut out devices and aperture sizes. Suitable dimensions for cover 3 are of the order of 120mm in length, 85mm in width and 80mm in depth before trimming.

The front face of the cover is provided with an indented section 12 in which a warning label can be provided as shown in Figure 3 Alternatively, or in addition, embossed lettering 13 may be used.

Since the cover shown in Figure 3 is intended to be cut to the desired size.

apertures for the entry of incoming cables are not provided but can be cut on site.

Ideally, the cover 3 may be provided with weakened areas (not shown) to facilitate this.

It will be appreciated from the foregoing that the present invention provides a simple and convenient method and apparatus for overcoming the severe drawbacks of the existing methodology and apparatus and present the opportunity for extremely considerable cost economies, in any situation where there is an REC electricity supply (for example street lighting, domestic property, office buildings etc).

Claims

1. A method of rendering safe a power cut-out device of the type used in street lighting columns and signs (commonly known as an REC cut-out), which method comprises the steps of mounting over the existing cut-out device a rigid and robust cover in a secure manner to thereby prevent direct access to the existing cut-out without use of tools.

2. A method as claimed in Claim 1 further comprising the steps of providing an additional fused isolation device, wiring it in series to the existing cut out device between the existing cut-out device and the load;

3. An apparatus for use in the method of Claims 1 or Claim 2, the apparatus comprising a substantially box-shaped cover open on one face to fit closely over an REC cut-out device and having means on at least one edge by means of which the cover may be secured to the conventional back board on which the REC cut-out is mounted.

4. An apparatus as claimed in Claim 3 wherein said cover comprises a first section which, before use, can be trimmed to a desired length and depth and a second section which, before use, can also be so trimmed, the two sections, in use, fitting closely together to form the complete cover which is not disassemblable without use of tools

5. An apparatus as claimed in Claim 3 or Claim 4 wherein the cover has apertures in the sides thereof that, in use, closely accommodate the incoming mains wire and outgoing wires leading to a said additional fused isolation device.

6. An apparatus as claimed in any of Claims 3-5, wherein the cover is made of a robust and rigid flame retardant plastics material.

7. An apparatus as claimed in any of Claims 3-6 wherein the cover is transparent to enable the existing REC cut-out device enclosed by the cover in use to be viewed in-situ.

8. An apparatus substantially as hereinbefore described with reference to any appropriate combination of the accompanying drawings.

9. A method substantially as hereinbefore described with reference to any appropriate combination of the accompanying drawings