14 x 1.8 MW containerised plant for a data-centre campus

A data-centre campus is now protected by fourteen containerised 1.8 MW generator sets, each built around a Mitsubishi S16R2-PTAW engine and a Leroy-Somer LSA52.3 L9 alternator running at 400 V, 50 Hz.

Containerised packaging was chosen over an indoor plant room because the site programme required the plant to be commissioned in parallel blocks while the halls were still being fitted out. Each container arrives complete: engine, alternator, fuel system, exhaust, control room and switchgear, all factory tested before shipment.

The sets are configured for parallel operation with automatic synchronising and load sharing, so maintenance can be carried out on any unit without reducing site capacity.

Why load acceptance matters more than nameplate rating

For a standby generator, the nameplate kVA figure is the least interesting number on the data sheet. What determines whether the installation works is how the set behaves in the first ten seconds after a mains failure, when the entire critical load transfers at once.

• Step-load capability defines how much load the set can accept in a single block.
• Transient deviation limits define how far voltage and frequency may fall during that step.
• Recovery time defines how quickly the set returns to steady state.
• Recovery time is what the UPS and the process control system actually care about.

The most expensive generator is the one that starts successfully and then causes the critical load to drop out anyway.

What this means for specification

When you specify a standby generator, state the ISO 8528 performance class alongside the kVA rating. For data centres, hospitals and industrial process lines, that class should be G3 or better. We verify the class on the load bank before the set leaves the factory, and the recorded results ship with the machine.

Practical next step

1. List the loads that must transfer to the generator, with their starting currents.
2. Identify the largest single step and the total simultaneous step.
3. State the permitted voltage and frequency deviation for each load group.
4. Send that schedule to us — we will size the alternator for the transient, not the average.