Caithness–Moray HVDC Link

The final bill was £970 million. The Caithness–Moray link had been budgeted at £1.1 billion, and when SSE completed it in January 2019 it came in under that figure, NS Energy reported. Cost overruns are the usual story in transmission; this one ran the other way.

The link crosses the Moray Firth, the wide inlet between Caithness and the coast east of Inverness. From the converter station at Spittal, in Caithness, the route runs underground to the sea, crosses about 113 km of seabed and continues on land to Blackhillock, near Keith in Moray. The total transmission length is nearly 160 km. The regulator approved it in 2014, and it has been in commercial operation since the end of 2018.

The reason was the grid in the far north. The link lets up to 1,200 MW of additional generation reach the main Scottish grid at Blackhillock. Hitachi Energy, which built the converters as ABB, notes that the two stations are not the same size: Blackhillock is rated at 1,200 MW, Spittal at 800 MW.

The link was designed from the start to accept a third terminal: a cable from Shetland. The Shetland HVDC link was energised in August 2024, and together the two form Europe’s first multi-terminal VSC HVDC system. Hitachi Energy calls it the second in the world.

Multi-terminal DC grids were one of the research questions of the BEST PATHS project, whose third demonstration looked at upgrading an older multi-terminal line in Italy. Caithness–Moray is where that idea runs commercially in the North Sea region today.

NKT supplied the cable. Hitachi Energy also holds a five-year service agreement for the converter stations, covering remote monitoring and round-the-clock support.