Pure DC Installs Final 75 MVA Transformer at LON01—What Should Be Checked Before Energization?

Introduction

• Pure DC announced on October 15, 2026, that it had installed the third and final 75 MVA transformer at its LON01 campus in London.
• According to the published project information, the three-transformer system has an installed substation capacity of 150 MVA, while the campus is designed for a 90 MW load.
• Following physical installation, protection, control, cable, cooling, and site acceptance checks are still required.
• Energization should be treated as a separate, controlled operation with defined approval gates and clear areas of responsibility.

Pure DC's announcement marks a significant construction milestone for the power infrastructure of the LON01 data center campus. Transporting, positioning, and mechanically installing a transformer of this scale is a complex task in itself. From an operational risk perspective, however, the next phase is at least as important: demonstrating that the equipment and every associated subsystem are ready for safe energization.

The most important engineering lesson from the project is not about a particular manufacturer or electrical topology. The key point is that a transformer can only be commissioned as part of the complete electrical system. Protection, switchgear, cables, auxiliary systems, cooling, monitoring, and operating procedures must all work together.

Who is this analysis for?

This article is intended for data center operators, facility managers, investors, electrical designers, technical procurement teams, colocation providers, and commissioning teams. The focus is not an assessment of LON01's detailed electrical topology—the announcement does not provide that information—but an overview of the technical checkpoints that are generally critical when commissioning a data center transformer of a similar scale.

The industry significance is clear: as data center loads increase and campuses adopt multiple supply paths and phased development models, substation handover increasingly depends on coordinated work across multiple systems and organizations.

What does the LON01 milestone mean?

According to the available sources, the newly installed unit is the third and final 75 MVA transformer at the campus. However, the stated 150 MVA substation capacity and the planned 90 MW campus load should not be treated as a simple arithmetic comparison.

MVA represents apparent power, while MW represents active power. The capacity actually available is influenced by factors including power factor, the redundancy model, permitted loading conditions, environmental conditions, auxiliary demand, and operational constraints. The announcement does not describe the load-sharing arrangement or the design philosophy for outage conditions, so further conclusions would not be justified.

The announcement nevertheless illustrates an important distinction: equipment installation and the operational availability of power capacity are two separate project states.

What is required before energization?

Reconciling documentation with the physical installation

The first step is to confirm that the installed configuration matches the approved single-line diagrams, cable schedules, protection designs, and manufacturer documentation. Checks should cover nameplate data, connection torque, grounding, phase identification, cable terminations, and the results of any post-transport tests required for the equipment.

For oil-insulated equipment, the oil system, leak tightness, level indication, and relevant sampling results may also form part of the acceptance package. The specific scope of testing will always depend on the equipment design, manufacturer requirements, and project specifications.

Protection, metering, and the trip chain

Differential, earth-fault, overcurrent, and thermal protection functions should only be considered ready once their settings have been approved, current transformer polarity and ratios have been verified, and the trip paths have been tested end to end.

It is not enough to confirm that a protection relay powers on. The tests must demonstrate that it operates the correct circuit breaker, that the indication reaches the monitoring system, and that interlocks prevent prohibited switching states. The coordination study should also be reconciled with the settings actually applied on site.

Auxiliary systems, cooling, and monitoring

Transformer cooling fans, pumps, temperature sensors, and auxiliary power supplies are not secondary details. Their failure can restrict loading capacity or create alarm conditions that operations teams may be unable to interpret correctly.

Statuses, alarms, measurement scaling, and timestamps should be verified in the SCADA or building management system. Local and remote control permissions, together with the process for transferring control authority, should also be documented.

What does this mean for operations?

The inrush current and transient conditions associated with initial energization can affect protection systems and network voltage. The switching sequence, monitored measurement points, shutdown criteria, and authority to stop the process in the event of an abnormal condition should therefore be defined in advance.

Post-energization checks should go beyond confirming that the transformer remains energized. Voltages, currents, noise, vibration, temperature, leakage, alarms, and communication status should all be monitored. Load should be introduced in predefined steps in accordance with the project's approved commissioning plan.

In a data center, the behavior of the downstream chain is particularly important. Medium-voltage distribution, UPS systems, generators, ATS or STS logic, and cooling auxiliaries collectively determine whether a supply event creates a service risk.

Common mistake: confusing installation completion with operational readiness

A common project risk is proceeding to energization too quickly after mechanical completion has been declared. Open punch-list items, temporary wiring, non-final relay settings, or incomplete SCADA point lists may still remain in the system.

Another mistake is accepting individual subsystems separately without testing their interfaces. A functioning relay, circuit breaker, and monitoring system do not prove that the complete trip and feedback chain operates correctly. It is similarly risky for the operations team to receive the final switching procedure only immediately before energization.

SAT and integrated systems testing

Within the SAT scope defined by the project, the site acceptance test should verify the operation of the installation, protection, controls, communications, and auxiliary systems. The results should be supported by test records, approvals, and a closed or formally dispositioned deviation list.

Energization, however, does not replace integrated systems testing. The purpose of IST is to verify that the critical power chain responds according to the accepted sequence under both normal and fault conditions. Scenarios may include loss of incoming supply, protection trips, transfer to a redundant path, and monitoring alarms. Specific tests should always be defined according to the system design, risk assessment, and operational constraints.

Recommended next step

For similar projects, a joint energization readiness review should be conducted with the participation of the owner, operator, designer, contractor, equipment suppliers, and relevant utility or grid stakeholders. At a minimum, the review should close out the following items:

1. confirmation that the approved drawings match the actual site configuration; 2. acceptance of cable, grounding, insulation, and transformer test results; 3. verification of protection settings, interlocks, and trip chains; 4. confirmation that auxiliary systems, cooling, and monitoring points are operational; 5. approval of the switching sequence, responsibilities, and abort criteria; 6. risk-based closure or documented management of remaining defects; 7. approval of the post-energization monitoring and load-introduction plan.

Conclusion

The installation of the final 75 MVA transformer at LON01 is an important step forward. From an engineering perspective, however, the next stage gate is demonstrating the safe and verifiable operational readiness of the complete system. Successful energization is not the result of a single switching operation, but of coordinated design, testing, documentation, and operational work.

Digital Technologies approaches these handovers by assessing the complete critical infrastructure chain: from medium- and low-voltage distribution through UPS, generator, and switching systems to cooling auxiliaries and monitoring. Independent technical review, phased execution, and auditable test documentation reduce the risk that a hidden interface fault will only emerge during live operation.