The decision to isolate high-voltage electricity supplies will need to be made in close consultation with the supplier. This will take into consideration the consequences of this action to the community both downstream and upstream of the incident.  

Fire and rescue services cannot isolate high-voltage electricity supplies. This can only be achieved by asking the supplier to isolate the supply. However, the request may take a considerable amount of time to achieve.  

If there are high-voltage lines, carrying 132 kV, 275 kV and 400 kV (kilovolts), additional safe distances need to be implemented over and above the normal cordoning requirements of an incident. 

It should always be assumed that the system is live until relevant power company engineers or other competent engineers confirm otherwise, for example, through a permit-to-work certificate. 

Personnel will benefit from having access to risk information about equipment and its location such as: 

• Substations 
• Transformers 
• Switchgear 

Columns or jets of water should not be applied to transmission towers and their components, as solid jets of water coming into contact with any electrical equipment creates a risk of electrocution. 

When firefighting in the close proximity of transmission towers, branches with spray, fog or mist can be used at ground level, as electricity is less able to conduct through droplets of water. 

As high-voltage electricity can arc, a hazard area needs to be established. This should be a minimum of 10m either side of the overhead lines at the widest point of the transmission tower. 

Any activity in close proximity of transmission towers should be subject to a risk assessment, taking into account: 

• The conditions, such as dense smoke 
• Wind direction 
• The equipment being used, such as ground monitors or aerial ladder platforms 

For more information see National Grid guidance for fire and rescue services.

Performing rescue of a casualty 

Although the exclusion zone for working near a source of high voltage electricity is 10m, if a casualty requires immediate rescue it may be necessary to reduce the exclusion zone to 5m, following a risk assessment. 

The Energy Networks Association has produced Safety Information for the Fire Service. This contains information on emergency situations involving electricity, along with important contact numbers for electricity companies. It contains a rescue flow chart that may assist with risk assessments. 

If it is necessary to rescue a casualty who is within 5m of high-voltage electricity, the following steps should be taken: 

• Request permission from the designated competent person to perform the rescue of a casualty, providing information such as: 
  • The condition of the casualty 
  • The distance and position of the casualty in relation to the point of contact of the high-voltage electricity 
  • Whether the casualty is at, above or below ground level 
  • Weather conditions 
  • Transmission tower markings and signs 
• Record permission when received 
• Carry out a risk assessment 
• Proceed with caution