60MVA 132/11kV Data Centre Connection, Hemel Hempstead


JSM were awarded the contract to provide a 60MVA 132KV Connection a new Data Centre in Hemel Hempstead.




25 Months

Date Completed

June 2020

The Brief

As part of the contestable works JSM will be completing power system design & reporting, full civils design of the 132kV – 11kV substation inclusive of construction of a dedicated 11kV substation building, 132kV Dual transformer bund area and iDNO adoptable 132kV Switchgear compound. JSM are also completing 132kV dual circuit cable route & electrical design along with the installation of over 6kM of dual circuit 132kV cable, 1.6kM of 11kV cable & 1.6kM of 33kV cable. The connection will be made onto a UK Power Networks owned 132kV tower as part of the non-contestable element.

Delivery and Approach

The delivery of the project is being undertaken in separate phases with the 11kV building & cable installation being completed in July 2021 to provide temporary 11kV power to the data centre to meet the customers commissioning requirements. Following successful energisation of the 11kV network, the 132kV bunded transformer compound, 132kV iDNO adoptable switchgear compound & 6kM 132kV cable route is being undertaken in order to meet with the proposed 132kV connection date of July 2022. This approach has meant that JSM have been flexible with our planning and construction to enable the customer to complete their commissioning and partial handover before the full 132kV load is available and not result in delays to the customers energisation requirements.

The Challenges

There have been substantial challenges on each phase of the project. The customers commissioning requirements meant that full construction was not possible in the timeframes and JSM arranged a temporary 11kV ‘Bootstrap’ connection from a nearby Energetics owned substation to provide power to the customers owned 11kV substation. This requirement has resulted in having to stagger the construction works with initial focus being on the delivery of a live 11kV substation within a construction site. JSM maintain the 11kV substation under our Operational Safety Rules while still operating a live CDM construction site around the building while the 132kV compounds are being built. The Site itself is within the CDM area of an adjacent contractor who, while JSM are building the 132kV compounds, are fitting out and handing over the main data centre building. This has meant that liaison with the adjacent contractor has had to be frequent with all delivery, installation works & contractor movement having to be co-ordinated with a 3rd party who share the same access area. The 132kV cable route has presented its own challenges with the route having to cross multiple high pressure gas pipeline, going underneath a disused railway with a HDD, underneath the M25 motorway and through a buried concrete retaining wall which have all required bespoke designs and extensive temporary works.