SSEN Transmission is responsible for maintaining and investing in the electricity transmission network in the north of Scotland and our network extends over a quarter of the UK’s land mass, crossing some of its most challenging terrain.

Our operating area is home to vast renewable energy resources, and this is being harnessed by wind, hydro and marine generation. Working closely with National Grid Electricity System Operator (the 'ESO'), we enable electricity generators to connect to the transmission system, allowing the electricity generated by them to be transported to areas of demand across the country.

Following a minority stake sale which completed in November 2022, SSEN Transmission is now owned 75% by SSE plc and 25% by Ontario Teachers’ Pension Plan Board.

SSE plc sold its UK domestic electricity and gas retail business, along with domestic energy services to OVO Energy in January 2020 and no longer manages these customer accounts.

This project, along with several other major projects planned in the north of Scotland, is part of a major upgrade of the electricity transmission network across Great Britain that has been independently assessed by the ESO as required to meet UK and Scottish Government climate change and energy security targets. More specifically, these projects are needed to deliver UK and Scottish Government 2030 renewable targets and follows the publication in April 2022 of the UK Government’s British Energy Security Strategy (BESS).

The BESS set out the UK Government’s plans to secure the country’s future energy independence by reducing dependence on, and price exposure to, volatile global wholesale gas markets. This will be achieved by accelerating the deployment of homegrown and affordable low carbon electricity generation, together with developing the electricity network infrastructure required to connect and transport this power. The BESS included an increased ambition for offshore wind of 50GW by 2030, up from the previous target of 40GW.

To enable connection of that 50GW of offshore wind by 2030 target, the ESO, working in

collaboration with the three GB Transmission Owners (of which SSEN Transmission is one), developed what is known as the ‘Holistic Network Design’ (the HND). Published in July 2022, it sets out the onshore and offshore electricity transmission infrastructure required across GB to deliver this UK Government target with a “Required in Service Date” of 2030.

In December 2022, the energy regulator, Ofgem, approved the need for these projects as part of its Accelerated Strategic Transmission Investment (ASTI) framework decision.

Our 2030 reinforcements are also key to enable the connection of the first phase of the ScotWind leasing round, which will connect 11GW of ScotWind’s total ambition of 28GW.

The requirement for an onshore connection from Spittal – Loch Buidhe – Beauly is confirmed within the Holistic Network Design and Ofgem’s ASTI framework, and forms part of a portfolio of SSEN Transmission projects to deliver these requirements we call the 'Pathway to 2030'.

The new overhead line (OHL) can follow the existing lines in some areas where other constraints allow, and the route options demonstrate sections where this may be feasible in parts. Since the existing line was developed in the 1950s/60s there have been changes to environmental and consenting requirements that mean routeing the new OHL entirely adjacent to the existing OHL would be difficult to consent.  
 
There are numerous properties that have since been developed very near to the existing OHL.  Positioning the new OHL in the same area would potentially infringe on these properties and may cause them to be encircled by both OHLs.  In addition, there can be effects known as a wirescape (when several OHLs are in the same area) that can cause the new and existing OHLs to appear more obvious in the landscape.  These issues would be considered a high impact and may risk consent for the project.  
 
The route options of the OHL aim to maximise the distance to residential properties where possible and this would be very challenging while following the existing OHLs. 

There are several new offshore cables being proposed as part of the Pathway to 2030 scheme. The decision to exclude subsea cables from our corridor assessment was driven by wider network requirements. National Grid’s Pathway to 2030 Holistic Network Design (HND) study concluded that an onshore connection was required to strengthen the network in parallel with planned offshore solutions, which excluded the option of exclusively using subsea cable to provide the required connection.  

Several offshore options are also being progressed alongside onshore reinforcements, including connecting Spittal to Peterhead via a 2GW high voltage direct current (HVDC) subsea link. The HND requires onshore projects to be completed in parallel to this subsea link providing reinforcement and resilience to the transmission network.  

There are several reasons why overhead lines are required alongside subsea cables. This includes the capacity that different technologies can enable, with 400kV overhead line double circuits capable of carrying around 5GW of electrical power when compared to up to 2GW for subsea cables, meaning multiple subsea cables would need to be developed, procured and delivered simultaneously to deliver the same capacity uplift.  

 Furthermore, onshore reinforcements present opportunities to accommodate onshore electricity generation and demand connections, including the support of local and community decarbonisation ambitions. It will also enhance the resilience and security of supply of local electricity networks across the north of Scotland.  

Finally, cost is clearly an important consideration, particularly given the cost of investing in the electricity transmission network is ultimately recovered by electricity bill payers across GB and that is one of the key factors in the ESO’s assessment of the proposed network reinforcements. The cost of HVDC subsea links and the associated HVDC Converter Stations that are required at each point these links connect to the onshore AC network are significantly higher than 400kV onshore reinforcements to deliver the same capacity uplift. 

These projects are steered by the National Grid ESO, and we are currently investigating options for an overhead line (OHL). Should there be a requirement to use underground cable (UGC) for a specific section of the route then this will be investigated.  
 
OHL is currently favoured for the majority of the route for several reasons, including the following:    
 
• The cost is 4-6 times higher for cabling and as a regulated business we must provide best value for customers  
• Operation and maintenance – it is easier to identify and address faults for an OHL. OHL also provides greater flexibility to upgrade based on future network requirements.  
• Land-use – UGC would require construction land width of approx. 50 m along the entire length which once reinstated, land use restrictions may apply to this width to avoid risk of cable damage. Land use beneath OHL can generally return to previous use, although the operational corridor must remain free of trees.  
• Community impact (visual and noise) – OHL generally have a greater visual and noise impact than UGC however, long distance UGC would require additional equipment above ground to maintain stability of the network or to convert power from DC to AC.  
• Environment (land take) – the impacts to sensitive habitats and soils & geology associated with 50 m construction width for UGC would be substantial. OHL impacts are limited to tower footings, which can often be micro-sited to avoid sensitive habitats. Although impacts associated with access tracks also need to be considered. 
 
Specifically relating to this scheme, the following points are important to note: 
 
•           No 275kV or 400kV underground cable on the SSEN Transmission network, only 132kV and HVDC 
•           Due to the voltage and capacity of the proposed circuits it could lead to more infrastructure required: 
•           Reactive compensation compounds  
•           Substation like compounds to stabilise the network 
•           Could be a frequent as every 10-15km of UGC 
•           Suitable compound locations may drive the cable route 
•           Joint bays, testing locations and cable sealing end compounds will be required 
•           Longer construction timescales 
•           Wider construction corridor creating potential for greater impact 

LiDAR flights and drone surveys that have commenced to undertake aerial surveys on potential overhead line routes, alongside other assessments, to help inform the ongoing development of this project.  These initial surveys have prioritised those routes which based on our initial assessment of key environmental, technical, and economic factors were identified, on balance, as performing the best.  However, please be reassured that no decisions have been taken on potential overhead line routes or substation locations. The drone surveyors have used paint that will wash away as a ground control point. 

SSEN Transmission is responsible for maintaining and investing in the electricity transmission network in the north of Scotland and our network extends over a quarter of the UK’s land mass, crossing some of its most challenging terrain.
Our operating area is home to vast renewable energy resources, and this is being harnessed by wind, hydro and marine generation. Working closely with National Grid Electricity System Operator (the 'ESO'), we enable electricity generators to connect to the transmission system, allowing the electricity generated by them to be transported to areas of demand across the country.

Following a minority stake sale which completed in November 2022, SSEN Transmission is now owned 75% by SSE plc and 25% by Ontario Teachers’ Pension Plan Board.

SSE plc sold its UK domestic electricity and gas retail business, along with domestic energy services to OVO Energy in January 2020 and no longer manages these customer accounts.

It’s the highest voltage electricity network in the UK – the ‘motorway network’ of the energy world. It transmits large quantities of electricity over long distances via wires carried on a system of mainly metal towers (pylons) and large substations. Transmission voltages in Scotland are 132kV, 275kV and 400kV. Larger generation schemes usually connect to the Transmission system.

The lower voltage parts of the system are called distribution networks. In Scotland, these local networks operate below 132kV whereas in England the distribution network includes 132kV. 

As a stakeholder-led business, throughout the life of our projects, we aim to work positively with local communities and keep people informed about what we are doing. This is particularly important when we are developing new projects, we want to understand what local people think about our plans.

We always endeavour to take the time to discuss our proposals with local community councils and the wider affected community and to carry out engagement throughout each of the development stages, listening to feedback before finalising project plans. The feedback we receive is vital to help us develop proposals that reflect the views of a variety of stakeholder.

To find out more about a project, visit our project web pages which can be searched by location or area. Each project has a dedicated Community Liaison Manager that you can contact. You can find their contact details in the individual project pages, where you can also sign up to project updates.

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