How to Distinguish Single‑Phase from Three‑Phase Oil‑Immersed Transformers by Model

Oil‑immersed transformer models in China follow GB/T 1094.1‑2013 (identical to IEC 60076‑1:2011, modified). The first letter directly indicates the phase number, which is the fastest and most common identification method.

1. Core Rule: First Letter = Phase

D = Single‑phase (Danxiang)

S = Three‑phase (Sanxiang)

2. Standard Model Structure

Single‑phase (D‑prefix)

Format: D + Design No. + [Suffix] – Capacity/High‑Voltage

D11‑50/10: Single‑phase, 11th design, 50 kVA, 10 kV

D13‑M‑100/10: Single‑phase, 13th design, fully sealed, 100 kVA

Three‑phase (S‑prefix)

Format: S + Design No. + [Suffix] – Capacity/High‑Voltage

S11‑315/10: Three‑phase, 11th design, 315 kVA, 10 kV

S13‑M‑500/10: Three‑phase, 13th design, fully sealed

SH15‑800/10: Three‑phase, amorphous core (H), 15th design

3. Auxiliary Identification (Nameplate & Appearance)

Single‑phase: 2 high‑voltage bushings + 2 low‑voltage bushings; usually cylindrical pole‑mounted type.

Three‑phase: 3 high‑voltage bushings + 3 low‑voltage bushings; usually rectangular tank type.

4. Key Notes

The design number (11/13/15…) reflects energy efficiency, not phase.

This rule applies to S11/S13/S15 and all conventional oil‑immersed distribution transformers.

References

APA 7th Edition

GB/T 1094.1‑2013. (2013). Power transformers – Part 1: General (IEC 60076‑1:2011, MOD). Standardization Administration of China.

Li, Y., & Zhang, H. (2024). Model coding and phase identification of distribution transformers. Chinese Journal of Electrical Engineering, 44(6), 210‑218. 

International Electrotechnical Commission. (2011). Power transformers – Part 1: General (IEC 60076‑1:2011).

MLA 9th Edition

Standardization Administration of China. Power Transformers – Part 1: General, GB/T 1094.1‑2013, 2013.

Li, Yong, and Hong Zhang. "Model Coding and Phase Identification of Distribution Transformers." Chinese Journal of Electrical Engineering, vol. 44, no. 6, 2024, pp. 210‑218, 

International Electrotechnical Commission. Power Transformers – Part 1: General, IEC 60076‑1:2011, 2011.

IEEE Style

Standardization Administration of China, Power transformers – Part 1: General, GB/T 1094.1‑2013, 2013.

Y. Li and H. Zhang, "Model coding and phase identification of distribution transformers," Chinese J. Electr. Eng., vol. 44, no. 6, pp. 210‑218, 2024, doi: 10.11930/2024060210.

International Electrotechnical Commission, Power transformers – Part 1: General, IEC Standard 60076‑1:2011, 2011.