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In terms of reliability, capability, cost, construction impacts and land use, overhead lines do have advantages when compared to underground cables. However, a significant benefit of undergrounding cables is the reduction in visual impact. In certain areas, such as protected landscapes, this benefit could be a primary consideration and outweigh disadvantages of undergrounding such as restrictions on land use and the impact on ecological and archaeological sites. National Grid considers the views and requirements of its customers and undertakes extensive stakeholder consultation before deciding which solution to take forward.
SSEN are investing over £15m in a project which will see the undergrounding of 90km of overhead lines in Areas of Outstanding Natural Beauty, National Parks and National Scenic Areas in the north of Scotland and central southern England.
Electricity is usually transmitted through overhead power lines suspended by towers or utility poles, but buried/ underground power lines are also sometimes used, especially in urban areas or sensitive locations. Overhead power lines have specific impacts on biodiversity, health and the landscape, which are different from underground power lines. On the other hand the initial investment costs of underground cables can often be significantly higher than overhead powerlines.
Represents Europe’s cable and wire producers.
Underground and subsea cable technology has matured to the point where it covers the entire scope of power transmission and distribution – both on land and at sea.
Examples from Germany and the UK show that an increase in undergrounding will result in a mere 1% increase of the total electricity bill for the end consumer, or approximately € 3 to 14 per average household per year.
Sustainability is a key factor in every infrastructure project today. Balancing the interests of families, communities, the industry, the economy and the environment requires access to the right information. Arguments need to be weighed carefully to reach the decision that benefits most, and if possible, all stakeholders.
The Netherlands, a country of just 16.7 million people but with a population density of 397 people per square kilometer, chose underground cables for the transmission network. In February 2010, the Dutch government adopted changes to the Third Electricity Supply Structure Plan (SEVIII) German Energy Line Extension Act (EnLAG) in 2009.
EnLAG accelerated the undergrounding approval process for four demonstration projects and provided clear guidelines on the use of underground cabling for utilities. It included a “200m/400m” rule to introduce physical boundaries to the application of underground cabling. Due to lack of clarity, EnLAG had mixed results. To resolve some of the legislation’s shortcomings, the Bundesrat recently approved the NABEG policy. The policy requires utilities to underground any 110kV line if the comparative cost factor to an overhead line is not above 2.75. NABEG does not account for 380kV lines, but the industry anticipates the publication of appropriate 380kV guidelines in the near future.
The cable industry association Europacable, for example, acted as a valuable information broker in Europe, developing and promoting the concept of partial undergrounding and producing a joint report with the European transmission organization European Network of Transmission System Operators for Electricity (ENTSO-E) to help legislators make informed decisions.
Where major electricity highways are concerned (= new ultra-high voltage direct current transmission lines), the Act will give priority to underground cables as a principle in federal planning. Overhead cables will only be used exceptionally in certain cases, e.g. in order to protect the natural environment. To put it simply, this means that there will be an absolute ban overheard cables being used wherever people live. So overhead cables can only be used in very strict exceptions.
400 kV connections are used for transporting and distributing large amounts of energy over long distances. 400 kV connections are generally built as overhead lines, but are undergrounded where technically possible.