vector group selection

Dear ,

There is no standard or fixed method as such.... the selection depends upon the type of sypply & special requirements.....

e.g. Normally, on high voltage distribution is received by consumers with 3 phase 3 wire system. Consumer's load may be with neutral. SO< you need delta - star - neutral requirement. DYN 11 configuration, where phase shift between transformer volts of hv & lv winding is 30 deg. Advantage is you eliminate the 3rd harmonics coming from the load. because of star connection .

Zig Zag winding is found in forming the neutral in 3 phase 3 wire supplies. that restricts the earth fault levels to safe limits & trips the relay.

if we used DY1 instead of Dy11 then what will happen?

There is no standard method for this.The selection depends on your application as for distribution system Dyn11 is used, similarly for commercial use in industries the transformer vector group selection is different such as YNd0 or Dd0 etc.