Transmission & distribution | Peterhead switching role


Peterhead in Scotland is the planned site for an innovative HVDC switching station that will be the key enabler for a proposed multi-terminal, multi-vendor HVDC system for offshore wind connection. It would be the first multi-terminal, multi-vendor HVDC installation outside China


The National Grid ESO’s Pathway to 2030, holistic network design initiative, launched earlier this year, sets out a blueprint for the electricity transmission network infrastructure required to connect very large amounts of offshore wind, helping to achieve the UK and Scottish government’s 2030 offshore wind targets of 50 GW and 11 GW, respectively.


For the north of Scotland, this will entail very significant investment in electricity transmission


infrastructure, including the following: ● two 2 GW subsea high-voltage direct current (HVDC) links from Peterhead to England: Eastern Green Link 2 (EGL2), connecting to Drax for 2029; and EGL4 connecting to South Humber. Both links will be taken forward as joint ventures with National Grid Electricity Transmission (NGET);


● a 2 GW subsea HVDC link from Spittal in Caithness, connecting to Peterhead;


● a 1.8 GW subsea HVDC link from the Western Isles, connecting to the north of Scotland mainland;


● 400 kV onshore reinforcements: between Beauly, Blackhillock, New Deer and Peterhead; between Beauly, Loch Buidhe and Spittal; and between Kintore, Tealing and Westfield; and


● an upgrade of the existing Beauly to Denny line to enable 400 kV operation on both circuits. “Alongside and co-ordinated” with these ‘Pathway to 2030’ investments, a new HVDC switching station at Peterhead, ‘Project Aquila’, is being developed by SSEN Transmission to accelerate the development of offshore wind. By integrating HVDC systems through multi- terminal and multi-vendor interoperability (for the first time outside China), this will help reduce the number of HVDC converter stations required for HVDC links, reducing costs and minimising community and environmental impacts. Project Aquila is one of the UK government’s four successful first tranche ‘pathfinder’ projects being progressed under the BEIS-led Offshore Transmission Network Review Early


Switching station removes need for multiple converters at Peterhead = cost and environmental benefits


AC system Peterhead


Peterhead area


HVDC switching station


Spittal to Peterhead HVDC


Interconnector (NorthConnect)


Offshore wind connections


Eastern Green Link (EGL) 2: Drax


Eastern Green Link (EGL) 4: South Humber


Remote end AC to DC converter


SSEN’s envisaged future investments “In-flight”


1. Argyll 275 kV strategy


2. Fort Augustus to Skye 132 kV upgrade 3. Orkney 220 kV AC subsea link


“Pathway to 2030”


1a. Beauly to Loch Buidhe 400 kV reinforcement 1b. Loch Buidhe to Spittal 400 kV reinforcement 2a. Beauly to Blackhillock 400 kV double circuit 2b. Blackhillock and Peterhead 400 kV double circuit 3. Beauly to Denny 275 kV circuit to 400 kV 4. East coast onshore 400 kV Phase 2 reinforcement 5. Spittal to Peterhead 2 GW HVDC subsea link 6. Peterhead to Drax 2 GW HVDC subsea link 7. Peterhead to South Humber 2 GW HVDC link 8. Arnish to Beauly 1.8 GW HVDC link 9. Aquila switching station (Peterhead)


New infrastructure


Upgrade/replacement of existing infrastructure


Existing network


Above: Main north of Scotland electricity transmission network in 2030 (source SSEN)


Opportunities workstream. The other three confirmed pathfinder projects are: Equinor’s proposal for shared transmission infrastructure between the Sheringham Shoal and Dudgeon extensions projects in East Anglia; Orsted’s proposal for Gigastack, a hydrogen electrolyser utilising power from the existing Hornsea 2 offshore wind farm in Yorkshire; and Orsted’s Boudicca proposal, to co-locate a 200 MW onshore battery to the grid connection of the Hornsea 3 offshore wind farm in East Anglia. A spokesperson for SSEN Transmission said that Project Aquila also “forms part of the scope for Ofgem’s accelerating onshore electricity transmission investment framework, with Ofgem expected to make a decision before the end of the year on which projects are to be taken forward through this new regulatory framework.”


26 | October 2022| www.modernpowersystems.com


The Peterhead site, where the planned Aquila HVDC switching station would be sited, is the location of the 1180 MW Peterhead power station. It first became operational in 1982 and in the 2000s underwent a major repowering project to convert it into an efficient and flexible gas fuelled combined cycle power station. Further redevelopment opportunities, for a decarbonised power station at Peterhead (Peterhead Carbon Capture, or Peterhead 2), are currently being explored.


Europe’s first multi-terminal (but not multi-vendor) HVDC installation, the Shetland (Kergord)-Caithness (Spittal)-Moray (Blackhillock) link, employing Hitachi Energy’s HVDC Light technology, is already under construction in Scotland, due for completion in 2024.


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