Substations are where data centre resilience begins

Artificial intelligence and higher-density computing are changing load forecasts while projects are still being designed.

Planning for densification and regulatory change

A facility conceived two years ago may need more capacity, revised phasing or additional space before construction is complete. Substation design must provide flexibility without committing the client to unnecessary infrastructure.

For a large data centre, the substation is more than a point of connection: it is the critical interface between the utility network and the digital infrastructure it powers. As facilities become increasingly power-dense, the availability and reliability of power can determine site viability, programme and operational resilience.

Replacement technologies vary in maturity across voltage levels and applications, projects may need to adapt specifications, layouts or approvals to align with what is technically viable and available within the required programme. The transition away from sulphur hexafluoride, or SF6, adds complexity. SF6 has long been used as an insulating and switching medium, but phased European restrictions will affect high-voltage switchgear from 2032.

This is particularly challenging in a market facing a shortage of general contractors and specialists with proven high-voltage experience. Substations bring together electrical, civil, structural, fire safety, acoustic and control-system requirements. Gaps in any one discipline can have knock-on effects for programme, cost and, ultimately, energisation.

Equipment availability, technical suitability and procurement lead times need to be considered together. At Deerns, we treat substation planning and construction as an integral part of data centre development.

Case Study:

On a major European data centre development, Deerns supported the delivery of a large open-air substation from early design through tendering and procurement to construction supervision. The role brought together multidisciplinary coordination, contractor review and programme alignment, helping ensure that the substation design remained technically robust and aligned with the wider data centre development as it progressed into construction.

Power availability shapes the programme

The first question is whether sufficient power is available and when it can be delivered. Early engagement with the network operator is essential because connection works may involve such activities as land acquisitions, easements, and works in public roads.

The initial assessment should establish 5 key parameters:

• Available capacity and delivery planning
• Connection voltage and transformation strategy
• Options for redundant supplies sources
• Cable routes, interfaces and connection costs
• Responsibilities across the utility, client and project team

These considerations help shape the master plan and business case from the outset. Addressing connection timeframes, routing constraints and land requirements early helps ensure the selected site can support the project’s power requirements and delivery programme.

Designing for the complete lifecycle

At higher capacities exceeding 40MWe, a dedicated high-to-medium voltage substation is needed to receive power from the utility transmission network at 400kV or 225kV and transform it for campus use at 11kV, 20kV or 33kV. The engineer must assess whether an open-air solution or compact enclosed arrangement offers the best whole-life outcome.

Indoor gas insulated switchgears (GIS) are compact and can reduce the substation building footprint on constrained sites especially for urban sites. Open-air substations (AIS) need more land but may offer technical, procurement or maintenance advantages. The decision should consider whole-life cost, not equipment cost alone.

7 core considerations include:

• Capacity, redundancy and future load growth
• Site location and substation position within the campus masterplan
• Safety clearances and building interfaces
• Delivery routes
• Maintenance and replacement access
• Transformer noise and fire protection
• Space for future extensions

Transformers and switchgears should be planned with maintenance, access and eventual replacement in mind. Designing sufficient space and clear routes from the outset supports reliable operation throughout the asset’s lifecycle.

Supervision protects design intent

A well-designed substation performs best when construction, interfaces and testing are managed by an experienced team. Factory testing identifies issues before delivery, when they are easier to resolve. Careful installation and commissioning ensure the system aligns with the approved design, utility requirements, local regulations and manufacturers’ instructions. Site testing confirms that the complete system performs correctly in its installed configuration.

Effective supervision should cover the full journey from factory to operation:

• Review of technical submissions and installation methods
• Factory acceptance testing before dispatch
• Verification of installation and site quality
• Site acceptance testing and commissioning
• Resolution of defects before energisation
• Complete as-built and maintenance documentation

Documentation is part of resilience

Accurate documentation supports safe operation, maintenance, fault finding and effective asset management. Yet many brownfield projects begin with incomplete or outdated records, making site surveys essential to establish what is actually installed and how existing systems are configured.

The final record should bring together approved drawings, equipment data, protection settings, test results, manufacturers’ manuals and maintenance procedures. Together, these records provide the information needed to operate, maintain and manage the asset throughout its lifecycle and should be managed with the same discipline as the physical installation.

Integrated expertise for a critical asset

Substations sit at the intersection of utility planning, engineering, procurement, permitting, construction and operations. Successful delivery requires multidisciplinary coordination, high-voltage experience and an understanding of how data centre requirements will evolve.

Deerns uses its extensive experience to connect power strategy with master planning, resilient design, construction supervision, testing and documentation. This helps clients turn a complex grid interface into dependable, adaptable infrastructure. As data centres become more powerful and densely loaded, that integrated approach will be essential to delivering capacity on time and protecting long-term resilience.