Data Center One-Line Diagram: Real 12.47 kV Examples You Can Download

What a One-Line Diagram Shows in a Data Center

A one-line diagram — the same document many engineers call a single-line diagram — is the master map of a facility’s electrical system. Each circuit is drawn as one line regardless of how many phase conductors it carries, so a single sheet can show the whole chain from the utility service entrance to the rack: medium-voltage switching, transformers, low-voltage switchgear, automatic transfer switches (ATS), UPS blocks, and the power distribution units (PDUs) that feed IT loads — together with the ratings of the protective devices between them. It is the first drawing a utility, a lender’s engineer, or a commissioning agent asks for, because it exposes the failure domains: what trips together, what transfers, and what rides through.

The Example Set: 12.47 kV Service to 136 kW GPU Racks

The one-line diagrams on this site come from a coordinated GB300-class GPU facility design. The chain on the zone one-lines runs: loadbreak switch → fused primary → 2500 kVA transformer (12.47 kV to 480Y/277 V) → secondary breaker → ATS → 2 MW UPS → PDU → a 42-rack GPU zone at 136 kW per rack. The set covers both six-path and four-path radial distribution variants, generator feeder interfaces, grounding, and buried-utility crossing details. The figure above is sheet E-110, the four-path power one-line from a shared utility point of interconnection down to the PDU paths.

How to Read the Sheets

The 108-page electrical set (Public Edition P3) is organized as an E-100 medium-voltage distribution series, an E-200 rack and generator series, an E-300 site-installation series, per-path E-7000/E-8000 ATS, UPS and control details, and E-900 CDU input sheets. Every sheet states its own assumptions and open items, and the set is published at Design Development — Public Edition status: real working drawings for study and evaluation, not construction issues. The wider engineering reasoning behind the architecture — failure domains, UPS sizing, feeder protection — is documented in the electrical architecture cluster of the Data Center Lab. Three of the one-line sheets can also be read interactively — zoom the vector drawing and click each device: E-104 (medium-voltage distribution), E-107 (Zone 7, six paths) and E-108 (Zone 8, seven paths).

The drawing set

Four books, 408 pages, free PDF, no account required, SHA-256 checksum for every file: Electrical, Public Edition P3 (108 pages) · Structural, Public Edition P2 (187 pages) · Network, Public Edition P2 (75 pages) · Liquid cooling, Public Edition P1 (38 pages). Checksums, release history and the smaller files (checklists, code, sample packs): downloads page. Design Development — Public Edition: for study; not issued for construction; not sealed. K&K Data Service Inc., Houston, publishes these sheets; the GB300-class project they describe is designed and not built. Field work, and what to send for a price, is on the Field work page.

Common Questions

Is a one-line diagram the same as a single-line diagram (SLD)?

Yes. One-line diagram, single-line diagram and SLD are names for the same document: each circuit drawn as a single line with device ratings, regardless of the number of phase conductors. This drawing set uses both terms interchangeably.

What voltage levels does the example use?

12.47 kV medium-voltage utility service, stepped down through 2500 kVA transformers to 480Y/277 V for distribution to ATS, UPS and PDU paths feeding 42-rack GPU zones at 136 kW per rack.

Why does the design use four separate power paths?

Each path carries its own transformer, ATS and 2 MW UPS block, so a fault or maintenance action on one path is contained to that path. The four-path and six-path zone one-lines in the set show how the paths divide the 42-rack zone load.

Can I reuse these one-line diagrams in my own project?

They are published for study and evaluation at Design Development — Public Edition status: not construction issues, not sealed by an Engineer of Record. Reuse follows the copyright and attribution terms stated inside each document, and every interface must be verified against your own utility and equipment data.