Specifying Standby Generator Set Requirements for Data Centers

Overview

The webinar lists what must be considered when selecting a generator for a data-center load: altitude and temperature derating, load characteristics, reactive capability, constant-power load acceptance and harmonic voltage distortion. The presenters stress manufacturer sizing evidence and a realistic operating sequence, meaning the chosen set should be judged under site conditions and the real load steps rather than on its nameplate rating.

The transient specification should reflect the operating sequence. The manufacturer is expected to document the proposed set against the specified transient limits using its own sizing tools. On harmonics, voltage distortion depends on two things: load current distortion and source impedance. An acceptable distortion level therefore cannot be established without generator sizing evidence. This gives the specification writer a practical task: state the transient limits together with the load-step order they apply to, because only then can the manufacturer show a result with its tool.

The presentation is an engineering webinar, not a full standard; it gives no numeric thresholds and should be read with ISO 8528. It still leaves the designer a clear warning: a fixed kW or kVA calculation does not by itself prove transient, reactive or harmonic suitability under nonlinear loads such as UPS. The webinar's value is the list of acceptance questions: at what temperature and altitude, under which load sequence and at what distortion level will the set be judged?

Key points

1. Generator selection must account for altitude and temperature derating as well as load characteristics.
2. Transient requirements should reflect the operating sequence; the manufacturer documents the proposed set against the specified transient limits using its sizing tools.
3. Harmonic voltage distortion depends on load current distortion and source impedance, so sizing evidence is needed to establish acceptable distortion.
4. Focus topics: site derating, reactive capability, constant-power load acceptance, harmonic distortion.
5. The related standard is ISO 8528; the webinar gives selection logic, not numeric thresholds.

Using it in design

• Take site conditions (altitude, temperature) and nonlinear-load factors as evidenced inputs.
• Write the transient limits and operating sequence into the specification and require the manufacturer's sizing output against them.
• Do not approve transient, reactive or harmonic suitability from a kW/kVA estimate alone; record these three checks separately.

Who should read it

Electrical designers writing generator-set specifications and procurement engineers judging a manufacturer's sizing evidence.

Related standards

• ISO 8528

Publication details

Authors

Mark Taylor; Earnest Glaser; Andrew Panning

Publisher

Cummins

Year

2022

Document number

PowerHour, August 10, 2022

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation