Electricity – overhead power lines
What you need to do
The law says that any work near electric overhead power lines must be carefully planned and carried out to avoid danger from accidental contact or close proximity to the lines.
The precautions necessary will depend on the nature of the work at the site and will be required even when work near the line is of short duration.
Safety can be achieved by a combination of measures:
What you need to know
Contact with live overhead lines kills people and causes serious injuries every year.
Work involving long or high plant or equipment eg excavators, MEWPs, scaffold poles, tipper vehicles and cranes, presents a particularly high risk.
- contact with a power line is not necessary for danger. Close approach to live conductors may allow a ‘flashover’;
- contact can be lethal with voltages as low as 230V;
- do not mistake overhead power lines on wooden poles for telephone wires; and
- electric current can flow through wood or plastic (if damp or dirty) and cause fatal shocks.
Planning and preparation
The first step is to find out whether there is any overhead power line within or immediately adjoining the work area, or across any route to it.
Information may be available from the local electricity supplier. If any such lines are found, you should assume that they are live unless proved otherwise by their owners.
If there are any electric lines over the work area, near the site boundaries, or over access roads to the work area, consult the owners of the lines so that the proposed plan of work can be discussed.
Allow sufficient time for lines to be diverted or made dead, or for other precautions to be taken as described below.
Eliminating the danger
Try to eliminate the danger by:
- Avoidance – find out if the work has to be carried out under or near overhead lines. It may be possible to avoid it altogether;
- Diversion – divert all overhead lines clear of the work area; or
- Isolation – make lines dead while the work is in progress.
In some cases it may be necessary to use a suitable combination of these measures, particularly where overhead lines pass over permanent work areas.
If the danger cannot be eliminated, you must manage the risk by controlling access to, and work beneath, overhead power lines.
Controlling the access
Where there is no scheduled work or passage of plant under the lines, barriers can prevent close approach. However, where plant will pass beneath the lines, defined passageways should be made.
The danger area should be made as small as possible by restricting the width of the passageway to the minimum needed for the safe crossing of plant. It is safest if the passageway crosses the route of the line at right angles.
Controlling the work
If work beneath live overhead lines cannot be avoided, barriers, goal posts and warning notices should be provided.
The following precautions may also be needed to manage the risk:
- Clearance – the safe clearance required beneath the overhead lines should be ascertained from the owner of the line;
- Exclusion – plant, equipment or hand tools that could reach beyond the safe clearance limit should not be taken under the line;
- Modifications – plant such as cranes and excavators should be modified by the addition of suitable physical restraints so that it cannot reach beyond the safe clearance limit;
- Additions – cranes with telescopic or fly jibs may need additional restraining devices to prevent alteration in length of jib or angle of fly jib; and
- Supervision – access for plant and materials and the working of plant should be under the direct supervision of a suitable person appointed to ensure that safety precautions are observed.