National Grid's Nautilus Interconnector awaits the outcome of ScottishPower's DCO

National Grid Ventures have published their NAUTILUS INTERCONNECTOR FAQ's this month, (May 2020).  Not surprisingly they are awaiting the outcome of SPR's application

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Here are some of the FAQ's:

What is Nautilus Interconnector?

Nautilus Interconnector is a proposed second Interconnector between Great Britain and Belgium. When built, it will create a new 1.4 gigawatts (GW) high voltage direct current (HVDC) electricity link between the transmission systems of Great Britain and Belgium. If constructed, Nautilus Interconnector could supply power to one million homes.

Is NGV (National Grid Ventures) supportive of an alternative and more co-ordinated solution to energy supply in East Suffolk?

NGV is supportive of the efforts to achieve greater co-ordination in energy infrastructure. NGV continue to promote and test alternative solutions with the UK Government and promoters at home and in Europe.

NGV believes that to achieve the UK Government’s energy targets (40 GW by 2030 and 75 GW by 2050) there needs to be greater co-ordination of how wind and Interconnector projects are connected. This is vital to ensure that the UK can meet both energy and environmental challenges and reduce the impact on coastal communities.

NGV is engaging with its European partners and the UK Government as to how it can best utilise the technology and the Interconnector system to bring greater co-ordination with offshore wind projects.

Who will be the decision-making authority for Nautilus Interconnector?

NGV has received confirmation from the Secretary of State for Business, Energy and Industrial Strategy (BEIS) that the proposed Nautilus Interconnector will be treated as a Nationally Significant Infrastructure Project (NSIP) and as a development requiring a Development Consent Order (DCO). This means that the final decision-maker for the project will be the Secretary of State.

In March 2019, NGV requested that the Secretary of State exercise its powers under section 35 of the Planning Act 2008 to deem Nautilus Interconnector as a development for which a DCO would be required. The DCO regime will require NGV to undertake a thorough Environmental Impact Assessment (EIA) and consultation process prior to any application being submitted. NGV and the Secretary of State acknowledge that the DCO consent process will provide a single, unified consenting process with clear and fixed timescales for the development to engage with stakeholders and bring its application forward.

What is a ‘Project of Common Interest?’

Projects of Common Interest (PCIs) are key cross border infrastructure projects that link the energy systems of countries in Europe. They are intended to help Europe achieve its energy and climate objectives: affordable, secure and sustainable energy for all citizens. In the long-term, PCIs are also aimed at realising the decarbonisation of the economy in accordance with the Paris Agreement, signed by the UK, which aims to achieve climate neutrality by the end of the century.

In the case of Nautilus Interconnector, the project has been identified as a PCI due to its significant impact on the energy market and market integration between the UK and Belgium. The project will boost competition in the energy market, achieve energy security from a more diverse supply and contribute to our climate and energy goals. The selection process for PCI projects is determined by the Trans-European Networks for Energy (TEN-E) Strategy, which will be complied with throughout the development process for Nautilus Interconnector. PCI status will continue for the project regardless of Brexit, given Member Status is only required for one country involved.

Connection point and transmission

How was the connection point to the National Transmission System (NTS) for Nautilus Interconnector chosen?

NGV made two separate connection applications to the ESO for connection points for both the Nautilus and EuroLink Interconnector projects. The ESO then undertook an appraisals process to identify a point of connection on its network for each application which included an assessment of environmental, technical and cost factors. As a result of this process, the ESO have provided grid connection offers (for both Nautilus and EuroLink) to a new 400 kilovolts (kV) substation located close to the Sizewell 400kV network, provisionally referred to as ‘Leiston 400kV’. This substation is more locally known as the proposed NGET substation in Friston.

What does an Interconnector need to connect to the onshore grid?

For Nautilus and EuroLink to connect to the proposed NGET substation at Friston, the proposed substation would require an extension for each additional project.

NGV understand that typically the maximum land take required to facilitate extensions to NGET substations is approximately 1.3 hectares (3 acres) for each connection offered at a location.

NGET has indicated that provision for the land required to extend its substation at Friston has been provided for as part of ScottishPower Renewables proposals for East Anglia ONE North (EA1N) and East Anglia TWO (EA2).

Decisions on changes and upgrades to the NTS are made by NGET in its role as the Transmission Owner. NGV remain in dialogue with NGET to understand if any changes or upgrades may be required to the NTS as a result of NGV’s connection agreements.

Other energy projects in the area

How are you working with other energy projects planned in East Suffolk?

NGV is working closely with the other promoters in the area including ScottishPower Renewables and EDF as well as East Suffolk and Suffolk County Councils. Decisions for the routeing and siting of Nautilus Interconnector will consider possible benefits of co-location for the environment and surrounding communities as well as other technical constraints.

NGV regularly meet with all of the promoters in the area, alongside East Suffolk Council and Suffolk County Council, at the Suffolk Energy Forum.

Cable routeing

How are the cables buried onshore and offshore?

Two HVDC cables are typically buried in a single trench, compared to HVAC cables which typically consist of two trenches with three cables per trench. Offshore, the HVDC cables will be buried far enough below the seabed to ensure that cables don’t get snagged.

What are the differences between the crossing techniques of Horizontal Directional Drilling (HDD) and open cut?

Horizontal Directional Drilling (HDD) is a construction technique that involves drilling underneath particularly sensitive areas and infrastructure that the project may encounter along the cable route to lay the onshore cable with minimal disruption. This technique avoids the need for digging deep trenches and allows construction to operate through different ground conditions.

Open cut trench excavation offers an alternative method of cable installation which can be used instead of HDD, particularly in more rural areas and where there are no major obstacles. It consists of excavating a trench section-by-section as the cable is laid. This excavation is then backfilled once the cable laying is complete.

Typical HDD Construction

Can you use the same cable route as ScottishPower Renewables (SPR)?

The proposed Nautilus Interconnector and the East Anglia ONE North (EA1N) and East Anglia Two (EA2) offshore wind farm projects are different technologies being brought forward by different developers with different timeframes. This means Nautilus Interconnector is not able to share the same cables or cable trenches. There may be potential to locate the proposed cables within an appropriate distance from SPR’s cable route which will be considered as NGV assess different options for cable routeing. NGV is studying the applications for both offshore wind farms in detail and liaising directly with SPR to understand as much as possible about its proposed cable route corridor. This is so that NGV can identify any opportunities for joint working and minimise any disruption. In some places, Nautilus may need to cross the cables for EA1N and EA2.

Whilst SPR has already selected its preferred route, Nautilus does not yet have a defined cable route (for either DC or AC cables), and it must undertake its own detailed environmental and technical assessment to progress its project routeing and siting options. National Grid Ventures (NGV) will work to minimise impacts on local communities and the environment where possible and will liaise and consult with communities and stakeholders when the project is ready to discuss the proposed cable route options.


Will there be any visible equipment at the landfall site?

Landfall is where the subsea cables are brought onto the land and are connected to the onshore cables. As all the cables will be buried underground at the landfall site, very little will be visible once works are completed, although there may be some relatively small-scale equipment visible above ground. A kiosk type structure (similar to a telephone exchange) may be required at the landfall location to boost the signal for the subsea fibre optic communication system. It is too early to confirm if this would be required at this stage.

Cable joint bays will need to be made at sections along the route during installation. Cable joint bays will be buried for the HVDC cables and will likely require a man hole cover for operations and maintenance access, these manhole covers may require fencing. The man hole covers would be visible above ground. Joint bays on the HVAC cables will require above ground link boxes (see typical AC cable construction figure on page 7).

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