Caithness Moray Shetland
The first multi-terminal HVDC VSC interconnection in Europe

Customer Story

Challenge

Project Details

Customer: Scottish and Southern Electricity Networks (SSEN) Transmission

Location: Scotland, UK

Scope: Three HVDC Light® converter stations in multi-terminal scheme, executed in two stages:

Caithness-Moray link commissioned in 2018 and prepared for further expansion
Shetland link operating since Aug ‘24

Client’s needs: To connect the Shetland to the UK transmission system whilst strengthening onshore network in Northern Scotland

Solution

Three HVDC Light® converter stations connected in multi-terminal scheme Based on Hitachi Energy HVDC Light® VSC technology  Symmetric monopole ±320 kV DC

Blackhillock (1,200 MW) – stabilizes the DC grid through DC voltage control

Kergord (600 MW) – stabilizes Viking wind farm on Shetland through frequency and AC voltage control

Multi-purpose HVDC for up to five converter stations and two solutions for multi-terminal connection point

Spittal (800 MW) – stabilizes Caithness AC network through grid forming control

DC Grid Master Controller to coordinate all signals and sequences, already implemented at first stage

Detail multi-terminal studies for up to 5 stations. Off-line simulation studies using Virtual Control & Protection (vMACH) for efficiency and early risk mitigation

Impact

Multi-terminal HVDC interconnection provides flexibility to transfer power in multiple directions, based on supply and demand, with minimal power losses

Contribute to bringing all greenhouse gas emissions to net zero by 2050

Enhance grid performance and resilience through voltage and frequency control

Help to connect and transmit wind power generated on the islands to the UK

A future proof solution boosting the integration of renewable energy 