Environment impacts of extra high voltage cables and overhead lines

For economic reasons, extra high voltage (“EHV”) underground cables (“UGCs”) are rarely appropriate for an entire new AC power transmission project (although in some long distance circumstances a DC cable may be a solution). UGCs are, however, especially effective at helping power transmission projects to cross areas where there are environmental sensitivities. These include areas that are:

• Close to homes, schools, and other human habitation;
• Of outstanding visual value, either historical or natural;
• Crucial to wildlife habitation and migration;
• Environments that present natural obstacles, such as waterways.

Underground cables are able to address these sensitivities as they offer:

• Far less visual damage after installation;
• The ability to engineer external fields to almost zero and minimal magnetic fields beyond 10 meters from the cable;
• No physical obstacle to animals or birds.

Today, some 2,700 km of underground EHV (220kV and above) power cables exist in Europe. So far, most of the cable has been laid in urban areas, to support major infrastructure projects, under waterways or to link power stations to the transmission network. However, UGCs have also increasingly been laid in rural areas across Europe. Principally, partially underground EHV lines have been applied in areas of outstanding natural beauty, where visual amenity supports an underground approach, or planning consent for an OHL was unlikely to be granted within an acceptable timeframe.

Some early examples from the 1960s and 1970s include the Snowdonia National Park in Wales and the Goring Gap in England. More recently, cables have been laid in sensitive areas in Denmark (Aarhus-Aalborg line), the UK (Newby-Nunthorpe) and Italy (Turbigo-Rho). Currently, EHV projects in Europe where cabling in sensitive areas is being considered include:

• 100km 380kV Elixhausen to Kaprun link near Salzburg, Austria;
• 220km 400kV Beauly to Denny link in Scotland;
• 80km 400kV Ullapool to Beauly in Scotland;
• 56km 380kV Ganderkesee to St.Hulfe in Germany;
• 200km 380kV France to Spain interconnector through the Pyrenees;
• 150km 400kV Sils to Verderio between Switzerland and Italy;
• 400kV interconnector between southern Sweden and Norway (South-West link)

In making a comparison between the environmental impacts of UGCs and OHLs, consideration should be given to the following factors:

• Land use
• Landscape and visual impact
• Geology and soils
• Water resources
• Ecology, nature conservation & ground restoration
• Cultural heritage and tourism
• Traffic and noise
• Electromagnetic Fields
• Decommissioning