Balfour Beatty is delivering a major upgrade to the East Coast overhead line (OHL) route on behalf of SSEN Transmission, increasing transmission capability from 275kV to 400kV between Kincardine and Kintore in Scotland.
Spanning a strategic route connecting substations at Kintore, Fetteresso and Alyth down to the SSEN Transmission/Scottish Power Energy Networks boundary near Blairingone, the project is strengthening existing infrastructure to support increased capacity, higher operating temperatures and the long-term resilience of Scotland’s electricity network.
Once complete, the upgraded line will operate at 400kV, significantly increasing transmission capability and supporting the integration of renewable energy across the network.
Engineering upgrades across a live network
East Coast OHL
With work happening along an operational OHL route, the project requires careful coordination to upgrade existing assets while maintaining network integrity and minimising disruption.
Works include:
- Strengthening and upgrading foundations at selected towers to support long-term network resilience
- Replacement of conductors, insulators and associated tower components to increase transmission capability.
These upgrades are being delivered while maintaining network operations, ensuring continued reliability throughout the works.
Adapting to change on a complex programme
Following a change in conductor selection instructed by SSEN Transmission in 2024, the project adapted to meet an enhanced scope which will deliver an additional 20% capacity uplift to Scotland’s electricity transmission network.
of conductor installed
of route upgraded and commissioned
insulators installed
social value delivered
This required:
- Re-sequencing works
- Procuring replacements materials for 51km of route
- Reworking 16km of previously refurbished sections
- Delivering an additional 39 tower foundation upgrades.
Despite these changes we maintained strong progress through effective planning and close collaboration with SSEN Transmission.
Progress at scale
By the end of 2025, significant progress had been achieved, including:
- 71% of the route rewired with Upas conductors
- 240km of circuit length upgraded and commissioned
- 4,320km of new aluminium conductor installed
- 120,000 glass insulators installed
- 6000m3 of concrete poured
- 152 of 153 foundations upgraded.
Programme delivery has been actively managed in response to external constraints, with completion now scheduled for late 2026.
Driving safety, environmental stewardship and digital innovation
Safety remains central to delivery, supported by strong leadership engagement and a consistent focus on Zero Harm.
The project has also prioritised environmental performance, supported by using digital tools to improve coordination and visibility across teams.
A digital site-specific pollution prevention approach using ArcGIS Field Maps has enabled:
- Real-time access to ecological constraints and buffer zones
- Live mapping of landowner boundaries and utilities
- Immediate updates and shared visibility across teams and stakeholders.
This has improved responsiveness to environmental risks and enhanced on-site decision-making and compliance.
Building skills and supporting communities
Beyond infrastructure delivery, the project is delivering meaningful social and economic value across the region, including (as of April 2026):
- Over £1.1 million in social value delivered
- Over £1.2 million spent with suppliers within 50 miles of the project
- 2,000+ days worked by local people on site
- Early career opportunities created, including apprentices and graduates
- 158 volunteering hours delivered, supporting local initiatives
- Over £3000 donated to local charities and community initiatives
- Strong engagement with local education providers, including careers events and support across schools, colleges and universities.
These figures represent Balfour Beatty’s contribution to the project. SSEN Transmission is also delivering direct benefits to the local community, including through its East Coast 400kV Overhead Line Upgrade Local Fund, which has distributed over £250,000 to local groups and organisations.