Underground cable costs revealed

PUBLISHED: 16:16 31 January 2012

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THE estimated costs of placing new power lines underground have been revealed today (Tues).

Since National Grid announced plans to install a 400,000 volt line and 150ft pylons across the North Somerset and Somerset countryside, campaigners have called for the whole line to go underground.

But, the energy giant has said the associated costs, which would be passed on to the consumer, cannot be justified.

An independent report prepared by engineering company Parsons Brinckerhoff and endorsed by the Institution of Engineering and Technology was released today comparing the costs of overhead and underground lines.

Overhead lines are the cheapest, with lifetime cost estimates varying between £2.2million and £4.2million per kilometre. Underground cables have lifetime costs varying between £10.2million and £24.1million per km - just 4.6 to 5.7 times more expensive than overhead lines.

National Grid has previously said placing the cables underground would be 10-17 times more expensive due to the cost of insulating the cables, using more copper in an underground line, laying the cables and using extra equipment to maintain a steady voltage.

These figures had been disputed by campaign groups including the Campaign to Protest Rural England, which has now accused National Grid of using inaccurate information during consultations.

But, National Grid’s major infrastructure development manager David Mercer said: “The findings of the study are broadly in line with the costs National Grid has been quoting.”

Gas insulated line (GIL) technology, suggested as an alternative option by the Somerset Alliance Against Pylons in December, is estimated to be higher in cost (ranging from £13.1million to £16.2million per km) than the lowest rated underground cable studied.

The new 37-mile long power line will be installed to connect a planned new nuclear power station at Hinkley C with a substation in Avonmouth.

The energy giant is due to consult on a final draft proposal before submitting a formal application to the Government’s Infrastructure Planning Commission for consent before work can start. This is expected to be made in 2013.

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