High Voltage Infrastructure Upgrade at RAF Lossiemouth

Project Context

RAF Lossiemouth is one of the UK’s most important operational air bases, supporting frontline aircraft and the national defence capability. The estate required a major high-voltage infrastructure upgrade to enhance resilience, increase capacity, and future-proof the site for evolving operational demands. 

OCS was appointed to deliver a design-and-build project comprising the upgrade of multiple 11kV substations and the installation of a new 33kV primary intake substation. The works formed part of a wider programme to modernise critical electrical infrastructure in a live military environment.

The scale and strategic importance of the site demanded robust planning, secure mobilisation, and careful coordination with on-site operations.

The Challenge

The project required the safe replacement and upgrade of ageing high-voltage infrastructure while maintaining continuity of power to critical defence operations. 

Works were carried out within a highly secure, operational RAF base, requiring strict compliance with Ministry of Defence standards, security protocols, and health and safety governance. 

High-voltage systems at 11kV and 33kV required specialist engineering, detailed switching strategies, and controlled outages to avoid operational disruption. The installation of a new primary intake substation also required integration with the existing distribution networks and careful sequencing of commissioning activities.

Our Delivery Model

OCS delivered the project through a fully integrated design-and-build model, combining in-house high-voltage engineering expertise with structured project governance. 

The delivery model included: 

• Detailed design and engineering of upgraded 11kV substations
• Construction and commissioning of a new 33kV primary intake substation
• Safe management of HV switching and planned outages 
• Coordination with base stakeholders to maintain operational continuity 
• Strong safety management aligned with defence estate requirements 

Self-delivery across core HV infrastructure reduced reliance on multiple subcontractors and ensured clear accountability throughout the design, installation, and commissioning phases. 

What We Delivered

The programme included upgrading existing 11kV substations to improve resilience, safety, and capacity across the estate. 

A new 33kV primary intake substation was constructed on site, providing enhanced electrical capacity and a strengthened connection to the wider grid network, including a new 10MVA grid supply and additional 11kV standby generation. 

All systems were tested, commissioned, and integrated into the live environment, with controlled transitions to the upgraded infrastructure to ensure uninterrupted support for base operations. 

Outcome 

The project delivered a safe and compliant upgrade of critical high-voltage infrastructure in a live defence environment, with zero unplanned outages during delivery. 

The new 33kV primary intake substation and upgraded 11kV substations provide improved resilience, increased electrical capacity, and a future-ready platform to support RAF Lossiemouth’s operational growth. 

Through structured design and build delivery, OCS completed the works in line with programme requirements, maintaining operational continuity and strengthening the long-term reliability of the site’s power infrastructure.