Network Emergencies
Ntt Hh3

30MVA capacity

With twin transformers

5km cable route

Through a congested London industrial area

Ten metered circuits

in operation

Providing resilient, high-capacity electricity infrastructure to support the UK’s digital infrastructure

Project overview

The Hemel Hempstead 3 data centre is managed by NTT, the third-leading data centre provider in the world. It offers scalable data centre space, and is connected both to their other data centres and to major carrier hubs in both Slough and the Docklands. With a maximum demand of 20MW, Hemel Hempstead 3 offers solutions for housing IT and network systems in a secure environment.

Last Mile has operated and maintained the electricity network serving the facility since construction, delivering both infrastructure expertise and long-term operational support.

Last Mile’s impact

Our scope of works included:

  • Long-standing operator of the NTT HH3 site, with experience dating back to the site construction by Gyron in 2016
  • Robust infrastructure featuring twin transformers and 30 MVA nominal capacity
  • Ten metered circuits in operation, plus two bootstrapped connections supporting a neighbouring NTT site.
  • Managed a complex 5 km cable route
  • Modular, containerised switch rooms delivered and commissioned efficiently, with all units installed in a single day.

The network has demonstrated long-term operational resilience, including transformer maintenance works completed in 2025 with only three months’ notice and no interruption to customer supplies.

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