The Epic Construct of the World’s Longest Onshore and Subsea HVDC Interconnector

A marvel of contemporary engineering, Viking Hyperlink—the world’s longest onshore and subsea interconnector—started industrial operations in December 2023. The challenge garners POWER’s inaugural Transmission and Distribution (T&D) Award for its many stellar attributes, together with the milestones and improvements which have outlined its journey.

Because the first industrial high-voltage direct-current (HVDC) transmission hyperlink was energized between the Swedish mainland and the island of Gotland in 1954, submarine interconnectors have multiplied, rising extra subtle with developments in cable design, new supplies and alloys, and set up strategies. In 2021, UK-based vitality multinational Nationwide Grid and Norwegian system operator Statnett marked the industrial operation of the 1.4-GW North Sea Hyperlink, which stretches 447 miles beneath the North Sea between the UK and Norway at a depth of practically half a mile. That challenge continues to carry a distinction because the longest subsea interconnector on the earth.

However on Dec. 29, 2023, Nationwide Grid, by means of its aggressive subsidiary Nationwide Grid Ventures (NGV), in partnership with Danish system operator Energinet, energized a good longer 1.4-GW line—Viking Hyperlink—which stretches 475 miles beneath land and sea to affix Bicker Fen substation in Lincolnshire, UK, with Revsing substation in southern Jutland, Denmark.

Whereas the £1.7 billion ($2.2 billion)±525-kV DC challenge will proceed to function at a most 800-MW cap till 2025 to go well with Danish grid system limitations, Viking Hyperlink in April 2024 earned the Guinness world file because the longest land and subsea HVDC interconnector (Determine 1). Nevertheless, because it was being constructed, the five-year challenge additionally marked a number of notable firsts, together with using a hydrogen gas cell system to offer off-grid energy throughout development and the deployment of the state-of-the-art cable-laying vessel, the Leonardo da Vinci, constructed by Italian cable producer Prysmian.

Laying the Basis

In line with Nationwide Grid, the imaginative and prescient for Viking Hyperlink was conceived in 2015 as Europe started to discover a extra resilient and interconnected grid. Whereas Denmark is a part of the Nord Pool energy market and already had good hyperlinks with Sweden, Germany, and Norway, the interconnector promised a brand new high-price marketplace for its rising fleet of onshore and offshore wind.

For Nice Britain, a hyperlink would permit entry to a “well-developed, low-cost market with costs set by a diversified vitality combine from throughout Scandinavia and Northern Germany,” it stated. On the time, prominently, wind technology outputs between the UK and Denmark confirmed low correlation and durations of excessive manufacturing had been unlikely to happen on the similar time in each nations, the corporate defined.

The challenge formally grew right into a enterprise pursuit when in July 2016, the European Union (EU) chosen Viking Hyperlink for a Connecting Europe Facility (CEF) grant, by means of which the EU co-funded its last improvement prices. (NGV and Energinet individually funded the challenge’s development prices.)

By December 2016, the companions had consulted on two cable route corridors. Detailed seabed surveys, using six specialised offshore vessels, within the North Sea then recognized the optimum route for the 385-mile submarine cable portion. The surveys, carried out with 93,000 manhours by impartial marine guide Fugro Survey BV, studied seabed circumstances to reduce environmental impacts, assist engineering perspective, and establish an acceptable design specification for the cables.

That work led to funding approvals by the Danish Minister for Power, Utility, and Local weather in October 2017. Uncertainty shrouding planning consents within the UK, nevertheless, delayed a last funding determination (FID), on condition that the consents fashioned the idea for the offshore and onshore development work. By December 2018, regardless of hurdles with an area planning authority within the UK for the onshore portion, many of the challenge’s functions had been authorized.

Fast Improvement and Collaboration

After NGV and Energinet set out a plan to fee Viking Hyperlink by 2023, challenge improvement started quickly evolving. In early 2019, the companions arrange a Joint Possession and Operations Settlement (JOOA) and commenced putting contracts. By August 2019, it secured essential contracts with Siemens Power for the provision and set up of apparatus for 2 converter station websites in Lincolnshire, UK, and Revsing, Denmark. Contracts for the challenge’s two parallel HVDC cables, in the meantime, went to Prysmian Powerlink S.r.l. and NKT HV Cables AB.

Prysmian’s €700 million contract, notably, included the turnkey design, manufacturing, and set up of 1,400 kilometers (870 miles) of cabling. As the corporate famous, the order for cabling was substantial. Given the tight schedule, it started organizing all actions for cable manufacture at its Arco Felice (Italy) facility “effectively prematurely” of the order. The proactive method proved useful in gentle of the COVID-19 pandemic. By Could 2020, Prysmian reported it had efficiently carried out manufacturing unit acceptance assessments for its first cable. “The manufacturing of cable is a really essential a part of all the challenge, as even the slightest hiccup may end up in delays that construct up alongside the road,” famous Fabrizio Traversi, Prysmian Group challenge director.

Development formally kicked off in July 2020. Siemens Power famous it set to work on the 2 converter stations, mobilizing “the best requirements, with a selected give attention to the most recent sustainability and low-carbon development strategies.” The an identical 300-square-meter converter stations, used to transform alternating-current (AC) to DC, and vice versa, would finally home HVDC PLUS know-how. Aligned to Siemens converter system specs, the outside and inside of the constructing, constructed by Danish development agency MT Højgaard, is designed by Rambøll, with decorations made by Viking Age tattoo artist Luciano Pezzoli.

UK-based multinational infrastructure agency Balfour Beatty, in the meantime, spearheaded a $117 million contract for the UK onshore civil works. Balfour Beatty was liable for the civil engineering and set up of 42 miles of HV cabling throughout Lincolnshire, connecting Denmark to Nice Britain at Nationwide Grid’s Bicker Fen substation.

Just some months later, Danish agency Munck Piping began 92 horizontal directional drills (HDD) to put cables manufactured by NKT in Denmark beneath dunes from Houstrup Seashore close to Blaabjerg to the converter station in Revsing by Vejen. “Horizontal directional drilling is used to keep away from digging and making an open cable trench in areas the place it’s essential to scale back disturbance from development work—for instance, when crossing roads, railways, water streams, and so forth.,” NGV defined.

An Modern Legacy

A very modern a part of the challenge concerned Siemens Power putting in a zero-emission hydrogen gas cell to offer off-grid energy for the challenge’s development in Lincolnshire (Determine 3). Provided that it wouldn’t have a grid connection for at the very least six to eight months, the gas cell nixed the necessity for diesel mills, offering 250 kVA of normal three-phase 400V energy, 216 kWh of battery storage to easy peaks in energy demand, as much as 80 kW of heating to about 20 cabins throughout the development villages, and energy for six electrical autos. Siemens Power’s accomplice, GeoPura, directed the gas cell’s waste warmth by means of warmth exchangers to warmth water, which was then piped to 2 drying rooms for the location employees’ private protecting gear.

From 2021 to 2023, the heavy submarine cables (weighing about 40 kilograms per meter) had been laid at depths of three,000 meters over the North Sea route by the inaugural run of Prysmian’s $185 million superior cable-laying vessel, Leonardo da Vinci (Determine 4), and buried utilizing Asso trenchers. “That is the world’s most superior cable-laying vessel, and with two rotating platforms of seven,000 and 10,000 tons—the best carousel capability out there—it might retailer and set up longer lengths of cable, thus requiring fewer joints and set up campaigns, and considerably enhancing the general challenge effectivity,” stated Prysmian.

By November 2022, the UK web site had obtained the primary two of its seven large Siemens Power transformers—every weighing as a lot as “54 elephants.” The Danish portion obtained its seven transformers in April 2023 (Determine 5). Ultimate cable testing was accomplished in July 2023, becoming a member of the UK and Danish grids for the primary time. The challenge achieved industrial operation in December 2023, wrapping up greater than 4 million working hours for the groups within the UK and Denmark.

The success of Viking Hyperlink, Nationwide Grid’s sixth interconnector, in 2023 prompted the utility to launch a brand new, even bigger challenge, LionLink with Dutch transmission system operator TenneT. The 1.8-GW interconnector between the UK and the Netherlands—the second hyperlink between the nations—will join their offshore wind property when operational within the early 2030s. “A second new hyperlink known as Nautilus [being developed under a partnership with Belgian system operator Elia] can also be within the planning section with the potential to attach with Belgium,” the utility famous.

For now, Viking Hyperlink is predicted to ship “£5.2 billion [$6.8 billion] in client profit over 25 years,” Nationwide Grid famous. “These calculations had been made by Ofgem as a part of the Cap and Ground evaluation for Viking Hyperlink. In its first yr, Viking Hyperlink is predicted to save lots of greater than 600,000 tonnes of carbon emissions based mostly on the identical metrics because the above.”

—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).