IN Brief:
- Caverion has secured a €15 million contract for a 70MW data centre substation in Mäntsälä.
- The new Nebius facility will sit alongside an existing 75MW data centre at the Finnish site.
- Caverion expects to complete the substation in autumn 2027 on a timetable driven by data centre construction.
Caverion has secured a contract worth approximately €15 million to design and deliver a 70MW substation for Nebius’s second data centre in Mäntsälä, Finland, with completion scheduled for autumn 2027.
The new 70MW building will sit alongside Nebius’s existing 75MW facility at the site, increasing the electrical demand concentrated around the Mäntsälä campus. Its dedicated substation will connect that additional load to the power network and provide the switching, protection and transformation functions needed between the utility supply and the data centre’s downstream electrical systems.
Caverion has not disclosed the voltage configuration, transformer ratings or switchgear specification for the new installation. Its Finnish high-voltage portfolio includes work across 110kV and 400kV networks, with around 30 new substations, approximately 50 substation refurbishments and close to 50 power line projects delivered to date.
The Mäntsälä contract adds another data centre project to that portfolio at a time when large computing loads are placing greater demands on transmission and distribution infrastructure. A 70MW site is electrically closer to a substantial industrial plant than to a conventional commercial building, requiring dedicated grid capacity and high-voltage equipment before the IT systems inside can operate at their intended scale.
Substation delivery therefore has to run alongside construction of the data centre itself. Transformers, switchgear, busbars, protection systems, control equipment and the external network connection must be installed, tested and energised before the downstream supply chain can support the full computing load. Delays in those packages can affect the commissioning sequence even if the building and server halls are otherwise ready.
Caverion has described the Mäntsälä schedule as exceptionally fast, with completion expected in autumn next year. Lead times for large transformers and high-voltage switchgear can stretch across many months, leaving procurement, design approval, civil works and installation closely interdependent once the connection programme is fixed.
The company is also delivering another €15 million Nebius substation in Lappeenranta, scheduled for completion in 2027, while its recent Finnish data centre workload includes projects for Hyperco in Kouvola. An earlier Mäntsälä contract for Nebius was valued at €80 million, and Caverion has also delivered work for Greenergy Data Centers in Estonia under a €50 million agreement.
Repeated projects allow high-voltage design and construction methods to be carried between sites, but individual connections still depend on local network conditions and utility requirements. Available fault level, connection voltage, network redundancy and the amount of firm capacity at the chosen site all influence the final substation arrangement.
Large data centres also impose a different operating profile from many industrial loads. Computing demand can remain high for long periods with limited daily variation, while AI and high-performance computing systems concentrate more electrical power into individual halls and racks. The resulting load must be supplied continuously through utility, onsite and backup infrastructure designed around defined availability requirements.
At utility level, that means the connection cannot be treated simply as another building-services package. Transformers and switchgear have to carry sustained high loads, protection schemes must isolate faults without unnecessarily removing healthy sections of the supply, and the network connection must be able to accommodate the demand within its thermal and voltage limits.
The 70MW figure published for the new Mäntsälä installation describes the capacity the substation is intended to serve, but does not disclose how Nebius will distribute that capacity internally or what redundancy level will be installed between the grid interface and the computing equipment. Those details generally involve multiple stages of medium- and low-voltage distribution, uninterruptible power supplies and backup generation inside the campus.
Finland has attracted data centre investment partly because of its power system, cool climate and availability of sites capable of supporting large electrical connections. Expansion at existing campuses can nevertheless require substantial new grid infrastructure when the next stage of development approaches or exceeds the capacity already available at the site.
Nebius’s second Mäntsälä building illustrates that progression. The existing 75MW facility already represents a large single-site electrical load, and the additional 70MW project requires another substation rather than relying solely on the electrical infrastructure built for the first phase.
Caverion’s work will now proceed through design, procurement, construction, installation and testing towards the autumn 2027 completion date. By then, the contractor is also due to have delivered its separate Nebius substation in Lappeenranta, giving it two additional high-voltage references in Finland’s growing data centre market.
