Why we have used multi ( Star & Delta) connection winding in power transformer on LT side in one transformer?

For distribution neutral is required for that star connection is used for LT side of Transformer

Delta Wye connections can exist on either side of the transformers !

My question was that both winding connections are in one unit Transformer. that transformer having3 wire star connected and6 wires output secondary side. Which have one portion star3 wire and2nd portion delta3 wires.

Power Transformer HV side is Delta Connection, this will help to reduce the copper usage. However LV side neutral point required to get the single phase supply.

In transmission we dont require nuetral but in distribution we need nuetral, in star we can get the nuetral point.

TO GET STAR  POINT OR NEUTRAL