Kintore - Fiddes - Tealing 400kV Connection

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 

There are a number of new offshore cables being proposed as part of the "Pathway to 2030" scheme. This project is required to supplement these offshore cables. The project enhances the onshore capacity of the east coast of our network area to enable the significant power transfer capability needed to take power from large scale onshore and offshore low carbon renewable generation in the north and northeast of Scotland, which cannot wholly be accommodated by both offshore links from Peterhead.  
 
In addition, East Coast 400kV Phase 2 is required as onshore works to utilise (a) the offshore link out of Fiddes that forms part of the HND east coast coordinated offshore network (for further export of power offshore direct to demand centres in England), and (b) the subsea link from Westfield substation in the Scottish Power Transmission area. 

The T-Pylon has been designed and developed to suit the needs of National Grid and their operating area in England and Wales. Unfortunately, this means it not readily suitable for the use in the North of Scotland for several reasons: 
 
Loads from the weather, such as wind and ice, are much more severe in SSEN Transmission’s operating area compared to National Grid’s. As a result, the span between structures would have to be reduced from the current 350m. This would mean more structures being needed, which would increase the visual impact, the land occupied and the amount of construction traffic on the roads. The lattice steel towers proposed by SSEN Transmission can readily do spans between 350m and 400m. 

The composite material used to make the diamonds on the T-Pylon could have a life span as short as 20 years, compared to the 40-50 year life span of the glass insulators used on lattice steel towers. Due to the size and weight of the diamonds, combined with the need to lower the circuit completely to replace the diamond, there would be the potential need for a major refurbishment scheme every 20 years. 

The steel pole sections of the T-Pylon are around 3.5m in diameter, and with an overall structure height 35m; it would likely require around 6-9 large low-loaders to deliver the structure to site. This would have a significant impact on local traffic, particularly where roads pass through communities.

Additionally, such vehicles may not be able to reach more remote sites on single track roads. Use of the T-Pylon would potentially limit any new lines to major roads and prevent the routing of lines away from communities where possible. Steel lattice towers are delivered as bundles of angle steelwork and can be transported by fewer and smaller vehicles, reducing the impact of construction traffic. 

Due to the concentration of the loads at the base of a narrow pole, rather than over the wider spaced legs of a lattice steel tower, the T-Pylon requires a substantial foundation with a large amount of concrete which is not possible to source in some areas of Scotland.   

The T-Pylon design can only turn angles up to 30°. Existing lattice steel tower designs can turn up to a 90° angle. This greatly improves the ability for new lines to avoid communities, viewpoints, and site scientific and environmental importance. Using the T-Pylon with its limited ability to change direction of the powerline, would greatly reduce SSEN Transmission’s ability to route the line to minimise its impact.

 
The T-Pylon supports an entire circuit on a single diamond. In the unlikely event of a failure the entire circuit would be lost. Due to the size and weight of the combined compared to smaller individual insulator sets used on lattice steel towers, they would take substantially longer to repair, greatly increasing the time to restore power. 
 

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. 

The existing OHL between Alyth and Kintore is currently being upgraded for 400kV operation. The existing 275kV OHL between Tealing and Kintore is not suitable for 400kV operation. The towers are not tall enough to provide suitable 400kV clearances. In addition, the towers are unlikely to be strong enough to cope with the additional weight of 400kV conductors. The new OHL is required to provide capacity in addition to what the existing OHLs carry. 

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 has recently announced its development of a Community Benefit Fund. This fund is the first of its kind for a Transmission Operator in Scotland and will provide a direct opportunity for SSEN Transmission to work with Communities directly hosting the transmission network on a variety of initiatives that will be Community led and directly support communities across the North of Scotland. 
 
The Community Benefit Fund will form a core part of our social and economic support in the communities and regions we operate in. The aim of the fund is to recognise the vital role local communities play in hosting the transmission network by providing a source of funds for community-led initiatives that have the potential to changes lives and create a sustainable and positive legacy. 

The project is funded through the use of system charges on all GB users of the electricity network and is part of a GB wide programme of works that are required to meet UK and Scottish Government 2030 energy targets.  
 
Ofgem is Great Britain’s independent energy regulator.  SSEN submit a detailed cost assessment for the project to Ofgem which is thoroughly reviewed and assessed by qualified Ofgem staff. Once complete, the project is subject to a post-delivery review, and if applicable, the majority of any underspend is returned to consumers.  Any approved overspend is also shared on the same basis. 
 
The project is funded through the use of system charges on all GB users of the electricity network and is part of a GB wide programme of works that are required to meet UK and Scottish Government 2030 energy targets. 
 
SSENT submit a detailed cost assessment for the project to Ofgem which is thoroughly reviewed and assessed by qualified Ofgem staff. Once complete, the project is subject to a post delivery review, and if applicable, the majority of any underspend is returned to consumers.  Any approved overspend is also shared on the same basis. 

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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