What is the difference between substaion transformer and power geneation transformer?

Question

why is the vector group different in power transformer which connected in power generating station and inter connecting system.

Answer 1

Work functions and asymmetrical iron are meaningless in this instance.

The choice of vector group for any three-phase transformer is determined by what is to be accomplished.

In a generator step-up (GSU) transformer, where the generator is at medium voltage and the grid is HV or EHV, it is common to use vector groups that allow very sensitive earth fault detection on the generator, without influence from the transmission system.

On a transmission or distribution substation transformer, the same constraints or requirements may not be true.  Thus, a Ynyn vector group may be used, especially if the primary or secondary systems must be effectively earthed.

Fundamentally, there is no difference between a transformer used for generation or transmission or distribution, since transformers do not care which way the power flows through them.  It is only in the specifics of the application that differences occur.

Answer 2

substation transformer a Step Down

And power generation transformer Step Up

look up the work function to see the asymmetry  in the design considerations.

you will see its the inductance of iron.

with "perfect" materials it would be symmetric