Design of the 132kV cable route through central London
Together with UK Power Networks (UKPN), Freedom identified the nearest point of connection capable of providing a 300MVA 132kV dual circuit grid connection at Islington, 13km from the data centre site. However, to meet the client’s deadline for the completion of the first data centre building, we established a temporary single circuit grid connection just 3.5km away in West Ham. To begin with the two routes run in parallel and then split off.
We were appointed to design, build and commission three cable routes and a new 300MVA 132kV/33kV substation within a congested area of central London. As the cable circuits will be adopted by UKPN on completion, the design meets standards and specifications listed in its G81 library of technical information. Our close ties with UKPN is an asset, cementing a comprehensive understanding of its standards and procedures. The design phase of the project followed the stages set out in the RIBA Plan of Work.
Designing cable routes through inner London inevitably meant finding solutions to navigate the many and varied obstructions. This led us into negotiations with stakeholders, including Transport for London (TfL), local London borough councils and business owners. We drew on combined expertise from our teams in design, surveys & inspection, estate & environmental, project management and land services.
Our in-house surveying team carried out utility record checks and surveyed the proposed cable routes to identify existing services and structures below ground. This was followed by trial hole excavations to inform the design of the route. Access problems were pinpointed above ground and we began consulting with stakeholders to agree the routes and secure necessary permits.
Due to the complexity of the route through central London, we identified several areas of Special Engineering Difficulty (SED) that required non-standard solutions. To avoid construction delays, we proposed design mitigation measures following UKPN’s guidance and discussed options with relevant stakeholders. Then we had derogation forms agreed and signed off by UKPN based on different scenarios before works began.
Some of the SEDs included designs for under and over crossings of rivers, railways and major A roads. We reviewed existing structural drawings and developed engineering solutions to determine a preferred design. Following engagement with the asset owner, the design was agreed and engineering consent given.