In 2017, VolkerInfra was awarded a contract from Siemens to design, supply, install, connect and commission two 33kV circuits, including 12 sets of three outdoor Raychem terminations at Iver substation.
The electricity substation owned by SSE (Scottish and Southern Energy) and National Grid, is located in Buckinghamshire and supplies electricity to the local area. The substation is one of the only cable upgrade packages in the UK that utilises an in air cable rating. This is to allow special ventilated trough systems to be installed to keep the cables from overheating.
VolkerInfra was awarded this contract due to its specialist cable systems design and installation capabilities and the strong working relationships the team had developed with Siemens on other projects.
The cable route was installed in precast troughs, which was changed due to design issues as the cable was maximally rated. (The previous design was to install a fully ducted system which would have caused the cable to overheat). The cable system was designed to flow in air to allow thermal ventilation throughout. Approximately 250m of trough was installed.
One of the greatest challenges on this project was to overcome the inherent issues faced with asbestos found in the ground, proximity clearance issues and crossing existing buried assets. This was overcome by contracting a specialist consultant who put control measures in place for air monitoring and ground contamination tests. For the proximity issues, smaller plant equipment was utilised with height restriction features enabled and a detailed design plan was carried out to ensure existing assets were not damaged.
During the project, VolkerInfra was awarded additional work. The team was asked to design, supply, install and commission one additional 33kV circuit and six sets of three outdoor Raychem terminations. The circuits will replace existing infrastructure within the Iver 400kV substation upgrade scheme.
Works on site commenced in May 2017 and are due to complete late 2018.