Transformer Applications by ANSI and IEC Vector Groups

Looking for some resources giving common applications (i.e. intended uses, pros, cons, etc) for the different ANSI IEC vector groups. I found this online document by googling but it doesn’t seem as professionally written or presented as I’d like, nor complete, though it is the best thing I’ve found so far.

I’d consider this topic a little more on the engineering side of things but some of our newer guys have been questioning why specific xfmr configurations (mainly uncommon ones you don’t see everyday) are in use on different sites and what they are accomplishing by using that specific vector group.

Any help is appreciated.

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Best location I have found for Common ANSI transformer vector group descriptions is Appendix B of the Vanguard ATRT-03 Manual (easily downloadable online). It shows hookups, and how to calculate for almost any transformer configuration (personally cannot vouch for every situation but it has helped me with the crazy configurations found on solar field sites).
Vector groups use letters (D: Delta, Y: Wye, Z: Zigzag, and N: Neutral connected) for the winding configurations and numbers for the phase shift between windings with the HV winding as reference. Just like the numbers on the face of the clock (except 0 = 0 degrees) counting clockwise: 1= 30, 2=60, 3=90, 4=120, 5=150, 6=180, 7=210, 8=240, 9=270, 10=300, and 11=330 degrees.
Capital letters indicate the High Voltage winding and lowercase letters indicate Low Voltage windings. Also, your normal Delta/Wye transformer will always have a 30 degree phase shift, and Delta/Delta or Wye/Wye always have 0 degree phase shift.

So for a normal 12kV-480Y/277V, it is read Dyn1 (since step down)
Now take a 208V-480Y/277V step-up transformer, it is read YNd11 (-30 degree phase shift)
Take the original 12kV-480Y/277V but no accessible neutral: reads Dy1

Hopefully this helps, but if not here is a good website:

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FYI, Electrical Engineering Portal and EC&M ( are my favorite websites next to Testguy for easy explanations of electrical theory

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Be sure to check out the Transformer Configuration module in the Pro App, it contains most of the common ANSI transformer configurations and will provide TTR values and tolerance range for each type. You can also enter additional transformer information to get other useful values.