Gridlink Interconnector

Electricity interconnectors are high-voltage transmission links, linking two electricity grids. Electricity can flow in both directions, allowing a grid to import electricity when it is running short so it does not have to fire up up old, inefficient fossil fuel power stations. Renewable sources are dependent on the time of day and on the weather conditions; the required load can be balanced by interconnecting grids over a large region, in this case over the Northern Seas Offshore Grid, and the North–South Western EU Interconnections. [2]

The project to build this 1,400-megawatt (1.4 GW) interconnector comprises

• 140 km (87 mi) submarine cable (108 km (67 mi) in UK waters and 32 km (20 mi) in French territorial waters), working at a DC voltage of approximately 525 kV.
• Underground cables from the shoreline to the converter station at Kingsnorth and Warande.
• Converter stations in Kingsnorth and Warande where the HVDC voltage is converted to 400 kV AC, which is the working voltage of both the networks.
• Underground high-voltage connector cables from the converter stations to the UK and French networks
• An additional substation in France.[2]^:3

The projected timescale is:

Awarded Project of Common Interest status (PCI) by European Commission 23 November 2017 (Commission Delegated Regulation 2018/540)

Application for UK development consents September 2020, and in France November 2020.

Construction contracts to be awarded July 2021, detailed planning consents September 2021.

Construction starts December 2021

Commissioning June 2024

Commercial operations start December 2024[2]^:5

The undersea cable connects two national grids, so must run from locations, close to the coast, capable of injecting the extra 1.4 gigawatts of power into the grid. Three points in Northern France were considered Penly, Les Attaques and Warande. Only Warande had sufficient capacity. On the UK side sites along the south coast were rejected as there was not sufficient infrastructure available to transport the electricity to the main network, while the North Kent coast and the banks of Thames Estuary was well supported. The following seven suitable sites were considered before Kingsnorth was selected: Cleve Hill, Coryton, Grain, Kemsley, Kingsnorth, Northfleet East and Rayleigh Main. The existing Kingsnorth sub-station already had the capacity, as the Kingsnorth coal fired power station had been decommissioned, and was 1.5 km (1 mile) from the shore.[2]^:10

The 400 kV AC link from the substation at Kingsnorth passes though a 1.5 km (1 mile) underground duct to the converter station which is on the shoreline. The two HVDC undersea cables enter a trench under the sea perpendicular to the shore and under the shipping channel where it follows the southern bank until off Grain where it crosses the channel and leaves the Medway passing to the north of the Sheppey anchorage berths.[2]^:12

The 140 km (87 mile) cable lies on the seabed protected by a covering of rocks or in a trench so shallow but not too shallow water is desirable; other users must not be disrupted, and a series of hazards must be avoided: anchorages, navigation channels, environmentally sensitive areas, known wrecks, moving sandbanks, unexploded ordnance, windfarms and other subsea cables. The route was chosen to take all this into account, and to turn south on the most western route to minimise cable length. In the Thames, it runs to the south of the Pan Sands sand bank and south of the BritNed interconnector cable.[2]^:14

In France the HVDC cable crosses the coastline in an industrial area owned by the Grand Maritime Port of Dunkerque (GMPD) and passes under their land for 10 km (6 miles) to a site alongside the RD11 junction (52a/b) with the A16 autoroute to the new converter station. The 400 kV AC link travels 3 km (2 miles) underground to the new Warande substation that is to be built adjacent to the existing RTE Bourbourg substation; they will share connection to the 400 kV AC overhead lines of the RTE. [2]^:15

• Gridlink Interconnector HomePage
• Non-technical summary of the project