Overhead high voltage electricity lines are normally bare (uninsulated) and if an object gets too close it is possible that a ‘flashover’ can occur, where electricity will jump over a small distance to reach earth.  This can kill or cause severe shocks and burns to any person nearby.

In order to prevent this happening, there are minimum safety clearances between overhead lines and the ground, roads or objects on which a person can stand.

Please take note of the advice below.

• A flashover to a tree can cause a loss of supply to customers, a fire in the tree or can lead to the tree itself conducting electricity.
• Despite the dangers, National Grid cannot actually prevent trees and vegetation being planted beneath its overhead electricity lines, as it does not own the land.
• However we have a duty to make sure that no tree comes close enough to an overhead electricity line to cause such a danger.
• We employ specialist contractors to undertake vegetation management beneath our overhead electricity lines to make sure safety clearances are not infringed over a number of growing seasons.
• All vegetation clearance work beneath and adjacent to overhead electricity  lines must be carried out by specially trained staff.
• Only low height, slow growing species should be planted beneath overhead electricity line, conductors and towers.
• Where planting is proposed in the area around a pylon (tower) base then consideration should be given to the need to maintain safe vehicle access to the tower base for overhead line maintenance activities and to prevent unauthorised access to towers.
• Tree roots can disturb and prevent access to maintain underground electricity cables.  Our prescribed planting distances between trees and buried services must be observed. 
• Detailed technical advice is available from National Grid, and should be sought before you finalise any landscape scheme.