General frequently asked questions are listed below. These are the questions and answers that relate to all our major infrastructure projects.

Frequently asked questions that are specific to particular projects, along with their answers, can be found within the individual project's section. For more specific FAQs please use the links on the left hand side of the page to select the project you are interested in.

1. Who are National Grid?
2. How does the electricity transmission system work?
3. How are decisions made about whether to develop overhead or underground power lines?
4. How do you route a new power line?

1. Who are National Grid?
   National Grid is an international electricity and gas company and one of the largest investor-owned energy companies in the world. We play a vital role in delivering gas and electricity to millions of people across Great Britain and north-eastern US in an efficient, reliable and safe manner.
   
   National Grid owns the high-voltage (275,000 volt and 400,000 volt) electricity transmission system in England and Wales and operates the system across Great Britain. We also own and operate the high-pressure gas transmission system in Britain and our distribution business delivers gas to 11 million homes and businesses.
   
   
2. How does the electricity transmission system work?
   Electricity is generated at power stations around the country. These power stations use a variety of fuels - principally coal, gas, oil, nuclear, hydro electric and wind - to generate electricity. The power stations are generally sited close to fuel and cooling water rather than near centres of demand, and so electricity needs to be transmitted from the power stations through our national high-voltage network of overhead power lines and underground cables. Local distribution companies then supply electricity at progressively lower voltages to homes and businesses. Suppliers sell electricity to the consumer.
   
   
3. How are decisions made about whether to develop overhead or underground power lines?
   National Grid considers every case for undergrounding a power line on its merits. However, the cost of undergrounding can be up to 17 times more expensive than an overhead line of the same length - and we have a statutory duty to develop and maintain an efficient and economical system.
   
   Undergrounding can also have significant effects in terms of loss of landscape features, sterilising land assets and disturbance during construction.
   
   The construction of an overhead line is less intrusive, as disruption occurs every few hundred metres, rather than along the entire route, and the traffic volume required for constructing an underground cable is much greater than an overhead line.
   
   It is also more difficult to detect and repair faults on an underground cable than it is on an overhead line.
   
   National Grid only considers burying underground cables in:
   • exceptionally constrained urban areas, where the density or residential community and associated development and public open space is such that a reasonably direct overhead line is impractical
   • exceptionally constrained rural areas, where there is special concern for the protection of important landscape features in nationally or internationally designated areas of amenity value. These designated sites areas comprise National Parks, Areas of Outstanding Natural Beauty, Heritage Coasts and World Heritage Sites
   • exceptionally constrained estuary and major river crossings.

   Find out more about undergrounding high voltage electricity transmission.
   

4. How do you route a new power line?
   Guidelines for the routeing of new overhead lines were originally formulated by the Central Electricity Generating Board, a predecessor to National Grid. These guidelines are known as the ‘Holford Rules’. They have subsequently been reviewed and supplemented by National Grid and are used as the basis of our approach to routeing new overhead lines. They are widely accepted and have been supported by Inspectors at public inquiries.
   
   The guidelines set out the principles to be applied in the routeing of new overhead lines. The selection of any new route will be a balance of all the various factors or constraints that have to be taken into account.
   
   In selecting an overhead line route, we seek to reduce the visual effect in terms of the number of people affected and the degree to which they are affected. The nature and topography of the landscape is considered and any statutory protection afforded to an area is also taken into account.
   
   We will seek to avoid the following areas, which are nationally or internationally designated for their landscape, wildlife or cultural significance: National Parks; Areas of Outstanding Natural Beauty; Sites of Special Scientific Interest including Special Protection Areas, Special Areas of Conservation and Ramsar sites; National Nature Reserves; Heritage Coasts; World Heritage Sites; and scheduled ancient monuments. Some of these areas can be very extensive and it may not be possible to avoid them completely.
   
   The selected overhead line route will typically seek to avoid crossing the highest contours, where pylons would generally be the most prominent, and will take account of the quality of the landscape and its ability to accommodate an overhead line.
   
   We will seek to minimise the effects of works and new infrastructure on communities by having particular regard to safety, noise and construction traffic. We will also seek to minimise the effects of new infrastructure on sites valued for their amenity such as listed buildings, conservation areas, areas of archaeological interest, local wildlife sites, historic parks and gardens and historic battlefields. We will take into account the significance of these and other areas through consultation with local authorities and other stakeholders with particular interest in such sites.