transformers vector group selection

[mustafaABB]

Hi
i have question regarding transformers vector group.
why for Generator Transformers are having YNd1 and YNd11 why it dose not be other like YNd5 or YNd7 or else same thing for distribution transformers.
I know for connected two transformers in parallel it must be the same vector group but why the only the above types are selected??
is it scientific reason or commercial reason?

Thanks

 

[veritas]

mustafaABB

I would think the reasons are mostly historic. In an established network where Yd1 or Yd11's are used, it would be wise to stick to the same in order to maintain the correct network phasing.

Also, standardisation - it is easier to replace a Yd1 with another Yd1 than say a Yd5.

Technically, I cannot think why one vector group should be more preferred than another. Of course paralleling trfrs require identical vector groups (a Yd1 could be made to behave like a Yd11, Yd3 or Yd7 but I'd rather not go there!)

Regards.

 

[Bung]

A rose by any other name would smell as sweet...
A-phase is 120deg from B-phase. 1 o'clock is 120deg from 5 o'clock. So Rename A-phase on a Yd1 to B-phase and voila! Yd5.

So there is no fundamental physical difference, and hence no oneed to manufacture anything otherthan Yd1 or Yd11. A simple renaming makes it 5 or 7.

Bung
Life is non-linear...