High Voltage infrastructure upgrade, new substation and HV ring main
The project incorporated an incoming National Grid supply, as part of a significant infrastructure upgrade delivered within a live operational site. The new substation was connected to both of the existing on-site substations, completing the HV ring main and providing enhanced resilience and continuity of supply across the site’s electrical network.
The scope of works included c650m of ducting, comprising two HV, two LV and two data ducts, linking all three substations. Excavation was generally undertaken to a trench width of c2m and a depth of up to 1200mm. Given the density of existing buried services along the route, vacuum excavation techniques were utilised in congested areas to safely expose and protect live infrastructure without risk of damage or service interruption.
To install two HV ducts beneath mature trees as part of the incoming NGED HV supply, approximately 90 metres of directional drilling was carried out. This trenchless method avoided disturbance to the tree root systems and surrounding landscaping while maintaining the required duct route.
The new HV substation itself was constructed within the staff car park. Earth mats were installed around the substation and along the trench route for the new substation, ensuring the installation met the necessary earthing and safety requirements.
Recognising the operational sensitivities of the live site, all works were carried out in carefully planned sections. Each section was fully completed and handed over before the next commenced, minimising disruption to car park availability throughout the 26-week programme. Critical road crossings were undertaken overnight, further reducing the impact on site users and daily operations.
Seddon worked closely with National Grid Electricity Distribution (NGED) throughout to coordinate the eventual energisation of the new HV supply, ensuring a smooth transition and minimising downtime for the University. Close collaboration was also maintained with CPW, lead designers for the HV element of the scheme, throughout the design and delivery process, ensuring technical coordination between design intent and site delivery at every stage of the works.