What Are Transformer Vector Groups (e.g. Dyn11, YNd1)?
Quick answer — The vector group describes the HV and LV winding connections and their phase relationship. The capital letters give the HV winding (D=delta, Y=star/wye, Z=zigzag), the lowercase the LV winding, and the number gives the phase shift in 30-degree steps (e.g. Dyn11 means delta-HV, star-LV plus an 11 oclock i.e. -30 degree shift). It determines how transformers can be paralleled and the third-harmonic/neutral behaviour.
What is a transformer vector group (Dyn11, YNd1)?
Reading the code
The first letter is the HV winding connection, the second the LV winding, and the number the phase displacement of the LV relative to the HV (in 30-degree increments on a clock face). A third letter may indicate a tertiary winding.
Why it matters
Parallel operation requires matching vector groups and phase shift; the connection also affects the neutral, grounding and third-harmonic current.
Common groups
Dyn11 and Dyn5 (delta-HV, star-LV) are common for distribution; YNd1 and YNd5 for power with a delta tertiary; YNy0 for a star-star with no phase shift.
References & standards
- IEC 60076-1
- IEEE C57.12.00
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
Source transformers for this application
Submit an RFQ or browse manufacturers and components.
Submit an RFQ Get Verified