After more than three years of political turmoil, the U.K. is scheduled to finally leave the European Union at the end of January 2020. While severing deep ties, the U.K. continues forging new links with continental neighbors, at least in the power infrastructure sector.

As the U.K.’s energy transmission company, National Grid (NG), invests in upgrading onshore assets, the company is adding to its three existing electricity interconnectors to continental Europe, with the EU part funding the newest project. NG plans to have a total of 7.8 GW of import-export capacity in place by 2024.

Last month, NG awarded to Balfour Beatty Group a $117-million contract for U.K. onshore civil engineering work on the Viking interconnector with Denmark. It will be the world's longest of its kind when completed in 2023, according to the company. The 765-km link is a joint development with Denmark’s Energinet and partially EU funded.

The Viking civil engineering award followed last July’s turnkey deal with Italy’s Prysmian Group, worth roughly $775 million, to supply and install cables for the 1.4-GW link. The same company in 2015 landed the subsea cable contract on the 740-km, 1.4-GW interconnector with Norway.

The North Sea Link, shared with Norway’s Statnett, is due to go live in 2021. It will follow on the heels of a planned commissioning of the U.K.’s second interconnector with France, the 1 GW IFA2.

As new international links come on stream, NG is launching a new $1.3-billion project to “rewire” London through a 32.5-km-long, 3-m-dia bored tunnel. Running across south London from Wimbledon to Crayford, the London Power Tunnel 2 will replace cables buried just below ground more than 50 years ago, says Gareth Burden, NG’s project director.

Under a design/build contract awarded in December, a joint venture of the U.K. unit of Germany’s Hochtief A.G. and locally based J Murphy & Sons is due to start work in March. The team will use four tunnel boring machines to complete the drives in six years, adds Burden. With contracts for cable and equipment and associated infrastructure to follow, NG plans to commission the three new circuits contained by the tunnel in 2024, 2025 and 2026.

Valued at $520 million, the tunneling contract is substantially costlier than one for another power cable tunnel of roughly equal dimensions in north London commissioned last year. More challenging ground conditions south of the River Thames partly explains the cost difference, says Burden.

To accommodate 10 separate power circuits, the northern tunnel runs for some 20 km from Hackney in north London westwards to Willesden. From near its west end, a 12-km spur heads south to Wimbledon. Starting in 2011, the Costain Skanska Joint Venture used a 4-m-dia Herrenknecht earth pressure balance TBM and a dual mode 3-m-dia Caterpillar MP139SE machine to drive the tunnels, under a contract worth more than $325 million, adds Burden.