What Happens If A Vehicle Contacts Energised Overhead Powerlines?

The vehicle will become live to the voltage of the powerline, and an electrical current will  flow from the powerline at the point of contact through conductive parts of the vehicle to reach the ground.

Despite rubber tyres not typically being thought of as conductive, high voltages can cause a large electrical current to flow through tyres to reach ground, even arcing through casing material and the tread rubber.

Large current flows may cause tyres to explode instantly, or alternatively the heating created by current flow can start a fire or initiate a decomposition process within the tyre (pyrolysis).

Pyrolisis is not immediately obvious but can cause a build up of flammable gasses and pressure within the tyre, which has the potential to cause a tyre explosion at a later time, even up to 24 hours later.

Tyre explosions are a significant hazard. The enormous amount of energy released has the potential for significant equipment damage, serious injury or fatalities.

What To Do If Contact Is Made With Overhead Powerlines?

The electricity supply should be isolated as soon as possible and an emergency response initiated.

The driver should remain in the vehicle and summon assistance, remaining in the vehicle until the powerline is either isolated or removed. Other persons in the area should not approach the affected vehicle until it has been isolated. Driver evacuation is recommended as soon as it is safe to do so.

The affected vehicle should be isolated at a safe distance from equipment and personnel for at least 24 hours to avoid the risk of tyre explosion following the contact with overhead powerlines.

Prevention

Operators of mobile equipment should be aware of the hazards associated with overhead powerlines and their vehicle clearance heights.

Road crossings under powerlines should be signed with the safe vehicle clearance heights.

Data outputs from the Aerial Powerline Surveying offered by Gridvision allow for an easy yet comprehensive way to audit all powerline height clearances where they cross travel paths and can help with the management of these across large sites.