We drive, cycle, walk or run past them every single day - but have you ever given the many miles of power lines stretching across our landscape much thought?

As the National Grid works to upgrade a major 52-mile, high-voltage line running from Norwich to Walpole, near Wisbech, passersby may be a little surprised to see the scale of work involved.

National Grid began an eight-month �50m upgrade of the 50-year-old line in April and it is creating a series of spectacles across the county.

With Meccano-style scaffolding scaling pylons, netting swooping above Norfolk's roads and panels laid across farmland to take the weight of 20-ton winching machines, it could make people pay the power lines a little more attention than usual.

As part of the improvements, engineers will replace all wires – known as conductors – as well as the fittings, and will carry out strengthening work on some of the 224 pylons which carry the wires across the county.

Sara Wilcox, National Grid spokesman, said the work was needed to maintain a reliable energy supply in the future.

She said: 'The pylons and the wires were built in the 1960s so they are reaching the end of their lives now and need to be replaced. At the same time we need to increase the capacity of the line – in other words how much power it can carry.'

In total 56,000 new insulators and 9,000 new line spaces, which stop the wires touching, will be fitted.

The upgrade is being carried out by 100 engineers.

Project manager Simon Chandler said it took a year of planning before National Grid were ready to begin the work.

Engineers had to identify every point where the line passed over a road, river, footpath or power network and decide whether they could carry out the work safely using scaffolding which allows engineers to 'pull' wires without the need to close public rights of way.

Mr Chandler said: 'It's not scaffolding as you would imagine. It's like a Meccano set. It means the sites are a lot cleaner – it all slots together.

'People are constantly attached to the scaffolding when they are working around it. The linesmen on the pylons can work at heights of about 55m, or 175ft. They find out very quickly if they haven't got a head for heights.'

Where the lines are not high enough to keep the work at a safe distance from cars and people, roads and footpaths are closed.

The workers are in the process of moving down one side of each of the 224 pylons from Walpole to Norwich. Once they reach the city they will turn around and head back.

Engineers work on sets of eight to 15 pylons – or towers – at a time and use 20-ton winching machines to pull the wires into place. Mr Chandler said: 'You attach the new wire to the old wire and the puller machine 15 pylons away will start pulling the old conductor through. As it does, the new conductor follows it.'

The workers often have to go on to farms and fields to access the towers. Rather than damage the land, panels – or even stones – are laid to take the weight of the equipment.

Information about road closures and other traffic-management measures can be found at www.nationalgrid.com/uk/electricity/projects/norwichwalpole.

victoria.leggett@archant.co.uk