Totally Integrated Power - Planning of Electric Power Distribution: Technical Principles

Overview

The manual is not a data-centre-only document. It covers demand estimation, MV network concepts, supply quality and EMC, availability and redundancy, reactive power, protection coordination and selectivity, switchgear, transformers, busbar trunking, UPS and embedded generation, and energy management. Its value is as a broad reference for default values and planning checks.

The demand-estimation chapter gives data-centre power-density planning ranges: 125-1,500 W/m2 for a self-contained data centre and 500-2,000 W/m2 for IT rooms in other buildings, with a simultaneity factor of 0.4-0.9. With (2n+1) redundancy the factor should be 0.4 for n=2 and 0.5 for large n. Tier IV redundancy costs roughly 2.5 times the infrastructure of a non-redundant Tier I design, with generators and UPS about 70% of the power-installation cost.

The availability chapter gives A = MTBF/(MTBF+MTTR) and the BSI classes: AVC2 99.9% (under 9 h/yr), AVC3 99.99% (under 53 min/yr), AVC4 99.999% (under 6 min/yr). That 99.999% can mean 1 s of outage per day or 1 h per 10 years shows why MTBF and MTTR must both be known. It also presents Harvard Research Group classes AEC-0 to AEC-5, with AEC-4 as fault-tolerant 24/7.

In the UPS section, the ITIC curve permits a voltage interruption of at most 20 ms for ICT power supplies, and static UPSs are classified per IEC 62040-3 by output dependency. Because UPS efficiency depends on load, a (2+1) redundancy can give higher availability, lower maintenance cost and lower losses than (6+1).

Key points

1. Power-density planning ranges: 125-1,500 W/m2 for a self-contained data centre, 500-2,000 W/m2 for IT rooms in other buildings; simultaneity 0.4-0.9.
2. With (2n+1) redundancy the simultaneity factor should be 0.4 (n=2) to 0.5 (large n).
3. Tier IV redundancy costs about 2.5 times a non-redundant Tier I design; generators and UPS are about 70% of power-installation cost.
4. A = MTBF/(MTBF+MTTR); AVC2 99.9% (<9 h/yr), AVC3 99.99% (<53 min/yr), AVC4 99.999% (<6 min/yr).
5. 99.999% can mean 1 s outage per day or 1 h per 10 years, so MTBF and MTTR must both be known.
6. Harvard Research Group defines AEC-0 to AEC-5; AEC-4 is fault-tolerant 24/7.
7. The ITIC curve permits at most 20 ms voltage interruption for ICT power supplies.
8. Because UPS efficiency depends on load, (2+1) redundancy can beat (6+1) on availability, maintenance and losses.

Using it in design

• Offer W/m2 defaults by building type (data centre vs IT room) and redundancy-dependent simultaneity factors in early sizing.
• Compute availability from MTBF/MTTR and map it to AVC/AEC labels alongside Tier.
• Warn when many small modules in N+1 run at low load, and show the module-count versus efficiency trade-off.
• Apply a redundancy multiplier of about 2.5 (Tier IV versus Tier I) in budget estimates.

Who should read it

Electrical designers and project managers making early sizing and availability decisions for data-centre power distribution.

Related standards

• IEC 62040-3
• IEC 60364
• EN 50160
• IEC 61000-2-4
• DIN 276-1
• Uptime Institute Tier Standard: Topology

Publication details

Authors

Siemens

Publisher

Siemens

Year

2018

Document number

TIP planning manual vol. 1

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