Central Networks, which distributes electricity across central England, uses helicopters with thermal vision equipment to spot problems.

Loose connections in substations give off "hotspots" which can be detected by engineers in the helicopters and repaired as soon as possible.

Helicopters will inspect 750 sites in Derbyshire, Leicestershire, Nottinghamshire and Lincolnshire.

Preventative measures

Alan Raymant, director of infrastructure services at Central Networks, said using helicopters was the "easiest and fastest way to carry out checks on large sections of the network".

"Once we get the information back from the helicopter we can then make sure we can get out there and do the necessary work before it causes problems for our customers," he added.

Central Networks spokesman Jamee Majid said the patrols could also help see which substations were being broken into as the company reported a three-fold increase in vandalism on its properties in the past year.