Data center white paper: 2N low-voltage distribution system design, IEC standards, 0.5 MW IT load (Chinese edition)

Overview

The design walks from rack PDUs and remote power panels through secondary boards, three classes of UPS (IT, cooling, life-safety), main switchboards with transformer/generator ATS, transformers and generators, and gives device selections and a monitoring architecture for PUE. The load basis is 63 racks at 7 kW = 441 kW IT; each RPP feeds 21 RPDUs (147 kW), with 3 RPPs per side and 126 RPDUs in total, each RPDU loaded to 50% in normal operation. The cooling basis is three 100 kW chillers (N+1) and six 15 kW CRAC units (N+1); fault-tolerant design requires IT-space temperature change not exceeding 5 °C within 15 minutes.

In the Tier comparison table, Tier III has one active plus one alternate distribution path, while Tier IV has two simultaneously active paths, compartmentalisation and continuous cooling, each side loaded to 50% or less normally. The IT UPS per side is one DPA 500 frame with five 100 kW modules (frames up to 500 kW, up to six frames for 3 MW); the cooling UPS uses four 20 kW modules in a 120 kW frame; and a 30 kVA EN 50171 central power system serves life-safety loads. The transformer is specified as dry type, 10/0.4 kV, 1250 kVA, Z = 6%.

For selectivity, the main ACBs switch automatically to a second protection setting when on generator, preserving selectivity in both supply configurations. For monitoring, Class 1 metering to IEC 61557-12 with harmonics up to the 50th enables PUE measurement up to Level 3 per The Green Grid. The modular build-out table steps from 12 racks / 84 kW (1+1 x 100 kW UPS modules) to 63 racks / 441 kW (5+5 modules).

Key points

1. Load basis: 63 racks x 7 kW = 441 kW IT; each RPP feeds 21 RPDUs (147 kW); 3 RPPs per side, 126 RPDUs in total; each RPDU at 50% in normal operation.
2. Cooling basis: three 100 kW chillers (N+1) and six 15 kW CRAC units (N+1); IT-space temperature change must not exceed 5 °C in 15 minutes.
3. Tier III has one active plus one alternate path; Tier IV has two simultaneously active paths, compartmentalisation and continuous cooling, each side at 50% or less normally.
4. IT UPS per side: one DPA 500 frame with five 100 kW modules (frames to 500 kW, six frames for 3 MW); cooling UPS four 20 kW modules in a 120 kW frame; 30 kVA EN 50171 central power system for life safety.
5. Transformer: dry type, 10/0.4 kV, 1250 kVA, Z = 6%.
6. Main ACBs switch automatically to a second protection setting on generator to preserve selectivity.
7. IEC 61557-12 Class 1 metering with harmonics to the 50th enables PUE measurement to Level 3 per The Green Grid.
8. Build-out steps from 12 racks / 84 kW (1+1 x 100 kW UPS modules) to 63 racks / 441 kW (5+5 modules).

Using it in design

• Use it as a template for a '2N LV, 0.5 MW' starter project, auto-generating the RPDU, RPP, secondary board, UPS, main board and transformer/generator chain from rack count and kW/rack.
• In 2N keep each side's normal loading at 50% or less; dual-feed N+1 mechanical loads from A and B; keep the life-safety UPS separate from the IT UPS.
• Support dual setting groups (mains versus generator) in the selectivity checker.
• Require IEC 61557-12 Class 1 meters at the points needed for PUE Level 2/3.

Who should read it

Electrical engineers designing 2N LV distribution and teams looking for a small Tier IV-oriented starter template.

Related standards

• IEC 60364
• IEC 61557-12
• EN 50171
• Uptime Institute Tier Standard: Topology
• The Green Grid PUE

Publication details

Authors

ABB

Publisher

ABB

Year

2022

Document number

9AKK107680A2361ZH Rev B

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