Shetland HVDC Link

Shetland is, by the Met Office’s measure, the windiest place in the United Kingdom, with an average wind speed of 14.6 knots. Until August 2024 that wind had nowhere to go: the islands had no electrical connection to mainland Britain. The Shetland HVDC Link changed that when SSEN Transmission energised it.

The cable runs about 260 km, all but some 10 km of it under the North Sea according to SSEN Transmission, from the converter station at Kergord, in the centre of Shetland, to a switching station at Noss Head, near Wick in Caithness. From there it joins the existing Caithness–Moray link, which had been designed years earlier to accept a third terminal. The result is a three-ended DC network, the first multi-terminal HVDC system in Europe and, SSEN says, the second in the world after one in China.

The first customer is the Viking wind farm on Shetland. SSEN expects it to produce about 1,800 GWh a year, enough for around 500,000 homes, and the link can carry 600 MW of generation from the islands.

The cable went in over three campaigns in 2022 and 2023, laid by the specialist vessel NKT Victoria, with the final section placed in autumn 2023. Hitachi Energy supplied the HVDC technology, a ±320 kV voltage-source design, and NKT the cable system; BAM Nuttall did the civil works and a Siemens and BAM joint venture the AC substation. SSEN’s managing director Rob McDonald said the project was “delivered ahead of time, on budget, and above all safely”.

One piece was still to come. The link was also meant to supply Shetland itself, through a new grid supply point at Gremista near Lerwick and new 132 kV circuits, with completion targeted for the end of 2025. For a wider view of how remote generation is brought ashore, see the guide to energy islands and the project’s first demonstration on HVDC links for offshore wind.