Transformer Vector Group Selection

I want to know.

why GT of power plant vector group is DY1? please Explain.

generally we used Dy11. if we use GT as DY11. wat happen??

I dint do it, honest, please sir ! Don't hit me

GT is Yd1 or Dy1?

Generally for export only transformer, generator side is connected in delta and load side is connected in star. For export import transformers star star connection may be preferred by some since this avoids a grounding transformer on generator side and perhaps save on neutral insulation.I am not sure how correct this practice is but so many systems are running in this configuration.Perhaps it may be felt to be less harmful than operating delta system incorrectly. Yd or Dy connection is standard for all unit connected generators.

The main reasons for connecting generator side winding in delta are:

1)to facilitate grounding of generator system with higher impedance and the load system with lower impedance.

2)To break The zero sequence circuit for the system at the transformer.This ensures the load side zero sequence currents do not come to the generator system.

3)IIIrd and similar harmonics will circulate in delta and will not come to generator system.

The trafo vector group will be Dy if load voltage is lower and Yd if load side voltage is higher.

Dy1,5,7 or 11 selection depends on requirement for load synchronizing ,standardizing or ready trafo availability. All vector groups are functionally similar.