Marine Surveys Launch for Second HVDC Cable Between Shetland and Mainland

Survey work is set to begin for the design and potential route of a second high voltage direct current (HVDC) cable linking Shetland to the Scottish mainland. Over the next several months, marine surveys conducted by Reach Subsea will focus on gathering vital information regarding seabed morphology, sediment structure, benthic characteristics, and habitat mapping. The areas designated for surveying include regions to the southwest and west of Shetland.

An official spokesperson from SSEN Transmission stated, “Starting this month and continuing through to summer 2026, our contractors will carry out detailed survey work between Shetland and the Aberdeenshire coast.” This survey work is a crucial early step that will help the company understand the marine environment, informing the design and potential route of the proposed Shetland 2 HVDC Link. The initiative follows information shared during last year’s public consultation.

Currently, a survey vessel is stationed in Shetland to monitor the existing HVDC cable, which runs from Caithness into Weisdale Voe and has a capacity of 600MW. This subsea cable is essential for exporting power from the Viking wind farm to the national grid and allows electricity to flow from the mainland to Shetland. With the Lerwick Power Station expected to enter standby mode later this year, Shetland will be connected to the national grid via the existing cable.

In light of forthcoming energy developments, SSEN has proposed a second HVDC link with a capacity of 1.8GW. This new cable is intended to facilitate the connection of two proposed offshore wind farms located east of Shetland, which together could generate up to 2.8GW. SSEN Transmission emphasized that the Shetland 2 cable will not only aid in connecting these wind farms but also support broader decarbonization and energy security goals, while addressing Shetland’s future electricity needs.

The proposed plan includes connecting the second HVDC link to a new northern substation hub facility in either the Sullom Voe or Scatsta area. SSEN is currently evaluating several landfall sites in Shetland for the second cable, including Wethertsa and Toft Ness. According to the energy company’s timeline, construction of the second cable could commence after 2028, with an operational target set for 2035.

The project entails more than just the cable; it will also require new HVDC converter stations at both ends of the link, as well as a new alternating current (AC) substation in Shetland. Additionally, there are proposals for large overhead power lines, referred to as “pylons,” to connect from Kergord to near the Sullom Voe Terminal. These overhead lines have generated significant local controversy and were recently the focus of a petition from residents of Voe.

As this project unfolds, the successful completion of these marine surveys will play a pivotal role in shaping Shetland’s energy infrastructure for years to come.