Hinkley Point C Connection frequently asked questions (FAQs)

The questions and answers on this page relate specifically to the Hinkley Point C Connection project. For more general FAQs please see our major infrastructure projects FAQs.

Questions

  1. Why are you proposing extending the electricity transmission system?
  2. Why can't you use the existing infrastructure?
  3. How long is the proposed new power line?
  4. How high will the pylons be, and how far apart?
  5. Are the pylons the same as ones already on your system?
  6. When do you plan to start construction, and how long will it take?
  7. Has National Grid considered undergrounding the overhead line or connecting Hinkley Point C to Seabank via a cable up the Severn Estuary?

Answers

  1. Why are you proposing extending the electricity transmission system?
    National Grid has a duty to offer terms for connection to the National Grid network when a customer makes an application for connection. We have received an application from British Energy Generation Limited (now part of EdF Energy) to connect a 3600MW nuclear power station at Hinkley Point by September 2017.

    The power station would comprise two 1800MW European Pressurised Water reactors. It would be one of the largest single generators connected to our system and, as a result, we need to reinforce and upgrade the National Grid network to accommodate the extra power and ensure system security.

  2. Why can’t you use the existing infrastructure?
    Where possible, we will make best use of existing infrastructure. However, new nuclear power stations such as Hinkley Point C produce more electricity and have different characteristics to their older counterparts so, whilst it is often possible to re-use the existing assets, additional assets are also required.

    We will only seek to build electricity lines along new routes, or above-ground installations in new locations, where our existing infrastructure cannot be technically or economically upgraded to meet system security standards and regulatory obligations, where forecasted increases in demand for electricity will not be satisfied by other means, or where connections to customers are required.

  3. How long is the proposed new power line?
    The proposed new power line would link our existing substations at Bridgwater and Seabank (Avonmouth). The line could be up to 37 miles long (60km), but the exact length would depend on the route option chosen.

  4. How high will the pylons be, and how far apart?
    Pylons will be a standard height of around 46.5m but extensions or reductions may be required in places depending on the land topography. The average space between pylons is 365m.

  5. Are the pylons the same as ones already on your system?
    The vast majority of our pylons were built in the 1960s. The new towers will be of about the same height and spacing, but slightly slimmer in appearance.

  6. When do you plan to start construction, and how long will it take?
    We expect to decide our preferred route corridor in January 2010 following our first phase of public consultation. After this, we will carry out a full and formal Environmental Impact Assessment, alongside an extensive public consultation programme. This will determine a preferred alignment for the overhead line within the preferred route corridor.

    We have allowed a construction period of 2012 to 2016. But because we have not yet made a decision on which option is to be built, this programme may vary.

  7. Has National Grid considered undergrounding the overhead line or connecting Hinkley Point C to Seabank via a cable up the Severn Estuary?
    When responding to requests for connection to the high-voltage electricity transmission, National Grid undertakes system studies to identify the impact of new generation on the system and the optimum method of connection having regard to our statutory duties. A High Voltage DC (HVDC) cable connection was one of the options considered as part of this assessment and National Grid would like to reassure you that it wasn’t dismissed without proper consideration.

    Under Section 9 of the Electricity Act 1989 ('the Act') National Grid has a statutory duty to maintain "an efficient, co-ordinated and economical" system of electricity transmission. The Company also has a duty under Section 38 and Schedule 9 of the Act to have regard to the desirability of preserving amenity when developing new transmission proposals. Potential options to achieve a new connection are therefore evaluated against these statutory duties. Often we are faced with a number of generators seeking connections to our system, as is the case in this instance here in the south west of England. Where such circumstances arise, we must ensure that connections are efficient and co-ordinated to meet the overall system requirements. In the case of the Bridgwater to Seabank overhead line, this means considering a solution that provides not only for the new Hinkley Point C nuclear power station, but also other proposed new generators at Oldbury, Seabank and the offshore windfarms off the south west coastline – in total nearly 10 gigawatts of new generation.

    When additional transfer capacity is required on our network we always look in the first instance to achieve this by uprating our existing overhead lines wherever that is possible. To connect the new generation proposed in the south west of England we will indeed be uprating some 200km of existing overhead lines, but there still remains a requirement for additional system capacity, which gives rise to the need for the proposed new 400kV line.

    Worldwide overhead lines are accepted as the most efficient and economic means of transporting bulk supplies of electricity. When compared to alternatives, the costs of overhead lines are significantly lower and operationally they offer higher reliability, for example when faults occur, they can be more easily and quickly located and repaired. The costs of transmitting electricity ultimately pass through to consumers in their electricity charges and in part due to the very high additional cost, the Company reserves consideration of underground cables for areas where there are exceptional constraints to a new overhead line route, such as in an exceptionally constrained urban area or a nationally designated landscape area (e.g. National Park or Area of Outstanding Natural Beauty). Our approach to undergrounding new connections is explained in more detail on our Undergrounding high voltage electricity transmission page.

    When selecting our preferred corridor and evaluating detailed alignment options following this first stage of public consultation, it is important to emphasise that in line with this approach, we will be giving consideration to any areas along the route where undergrounding may be justified in consultation with advisory bodies, which will include the Mendips AONB and the Avonmouth area.

    As already stated, the use of an HVDC solution through the Bristol channel to achieve the additional transfer capacity was considered. There are a number of very significant technical and environmental difficulties with such a proposition. The type of HVDC technology required for such a solution has never been utilised at the required capacity before or integrated in such a manner within an AC transmission system. In addition the Bristol channel has a number of national and international environmental designations and the very large tidal range would make laying and protecting a major power cable system extremely difficult.

    Furthermore, the costs of the required HVDC solution, given the issues above, would be in excess of £1bn far exceeding any potential overhead line solution. National Grid hope you will therefore understand that such an HVDC solution would not be justifiable when considered against our obligations under the Electricity Act and explained above.

    Finally, it is useful to note that our approach to use overhead lines when new additional capacity is required on our system has been accepted following consideration by the Secretary of State on a number of occasions over the last 15 years including connections for Teesside Power and Salt End power stations in North Yorkshire, South Humber Bank and Spalding Power Stations in Lincolnshire and Seabank Power Station in Avon. Only on the Teesside connection was a section of undergrounding required for 5.7km out of total line length of 75km to protect views to the North York Moors National Park. Other instances, where underground cables have been installed have included proposals in ‘exceptionally constrained urban areas’ (e.g. central London) where, consistent with our policy on undergrounding, an overhead line would be impracticable, or where nationally significant infrastructure projects, for operational reasons, require a section of overhead line to be placed underground, and meet the cost of it (e.g. Manchester Airport Second Runway).