Transformer Vector Group

Try these: en.m.wikipedia.org/wiki/Vector_group www.control.com/thread/1026211688 (read the reply by Phil Corso. Im sure it will shed some light)

Check this

Zig-Zag Transformer and Transformer Vector Groups

Dyn11 means the HV winding is connected in Normal Delta and the LV winding is connected in Normal Star, with the LV neutral brought out. The LV voltage will lead the HV voltage by 30degrees.

Now, consider a 11kV/415V, Dyn11 Trf. Let us say, if, let us say, the (1U-1V) HV voltage is 11kV at an angle zero degrees, then the (2u-2v) LV voltage will be 415V at an angle PLUS 30 degrees. Conversely, if the LV voltage is 415V at an angle zero degrees, then the corresponding HV voltage will be 11kV at an angle MINUS 30 degrees.

But, make sure you don't apply even 415V (leave alone anything more) at the LV side and attempt to measure the HV voltage (11kV) directly. It might be catastrophic.