Overhead services

Lesson Progress:

Every year people are killed or seriously injured when they come into contact with overhead electricity power lines.

If there is contact with a power line, or even if a piece of equipment gets too close to it, the electricity can be conducted to earth, which can cause a fire, an explosion and shock or burns to anyone touching the machine or equipment.

Overhead lines can be difficult to spot, particularly in foggy or dull conditions, but often people just fail to look up.

Overhead cables carrying electricity are generally uninsulated. You must be mindful of the following.

  • Electricity will flow through any conductor that comes into contact with it (such as a metal ladder, a scaffold pole or a raised excavator bucket).
  • Electricity may jump through the air (arc) to anything nearby that will conduct electricity.

The siting or use of cranes, lifting appliances or any conductor near to overhead power cables is dangerous and extreme care must be taken. If there is a danger to people with scaffold poles or other conducting objects then barriers should be used to keep people and mobile plant out of the area.

Power lines should be isolated and made dead or suitable precautions taken to prevent danger before any work takes place.

Electricity travels at the speed of light – more than 186,000 miles per second. You and the people you work with don’t.

Always contact the power supply company before siting or using any plant or conductor near to overhead power cables. They will tell you the voltage of the supply and the minimum safe distance. If it is not possible for the power to be isolated, they will tell you the minimum safe working distance from which a safe system of work can be developed.

A safe system of work will often involve putting up barriers and possibly introducing other control measures to make sure that nothing and no-one enters into the exclusion zone.

Example of a safety zone

Overhead power line electrocution

A construction company was prosecuted after a crane operator suffered an electric shock when the equipment he was using came into contact with overhead power lines. The sub-contractor was using the crane to move sections of steel. As they started to lift a section of steel using the crane, the hook block came into contact with an 11 kV power line and he suffered an electric shock. The sub-contractor was resuscitated but now suffers from long-term memory loss. The electricity company had warned the contractor about the presence of the overhead power cables, and had received advice on the removal of the power supplies running across the site. However, no measures were put in place by the company to prevent plant and equipment accessing the area beneath the power lines or for the power supply to be diverted or isolated. The company was fined £20,000.

The HSE said: ‘This terrible incident could have been avoided had the company placed physical barriers on site so that no plant or equipment could gain access to either side and directly below the overhead power lines, or if the high voltage cables were diverted or isolated’.