Power lines checked from the sky

Helicopters have revolutionised inspections

As a helicopter embarks on its journey to check miles of overhead power lines, BBC reporter Clare Muckart joins the pilot for a bird's eye view.

Some 54,000 km (33,554 miles) of overhead cables provide power to 3.7 million CE Electric customers from Northern Lincolnshire to the Scottish Border.

Helicopters have revolutionised inspections, which in the past were carried out on foot, and still must be every decade.

But, between January and March, engineers are in the best place to look for faults - hovering above the power lines.

The crew is given special permission to fly very low and close to the cables.

Ann Walker, customer liaison co-ordinator for CE Electric, said: "We have lines going over the North Yorkshire Moors, which are so difficult to get to. But in a helicopter, it makes it much easier and allows patrols to spot if any damage has been done to the wires."

The engineers and crew are looking not just for damage to the equipment but obstructions such as overgrowing trees, which may disrupt power supply.

The thermal imaging camera scans for faults

Ms Walker added: "The observer can also see whether anyone is building children's playgrounds under the power lines or whether people are building fishing ponds.... even things like fishing lines, kites and goal posts.

"You have to make sure long objects don't come anywhere near high voltage power lines because electricity can jump gaps."

The helicopter is equipped with a thermal imaging camera, which in Northern Lincolnshire and East Yorkshire, scans more than 1,000km (621 miles) of 33,000 and 66,000 volt lines.

Livestock distress

Lines should be the temperature of the air so any faults are immediately obvious on the monitor carried by the crew. The hotter the fault, the whiter the image glows.

For this reason, inspections must be carried out during cold and dry conditions.

Working over predominantly rural land, it's not just the cables the crew must concentrate on. They're also looking out for cattle and horses which they must avoid upsetting.

Ken Chisholm, airborne observer for CE Electric, said: "Obviously our prime concern is that we don't cause any distress to any livestock animals or anybody.

"We are doing our utmost to try to make sure we do this job as safely as possible without actually causing any problems to the owners of the land."