Different literatures say different things regarding ∆-Y and Y-∆ 3 phase transformer connection...
Some say that ∆-Y is used for step down and Y-∆ is used for step up while others say just the opposite things...
Depending on this step up and step down ability they are used in transmission and distribution of power... So please can anyone explain me what are ∆-Y and Y-∆ actually used for(which for step up and which for step down) along with a mathematical reason... Thanks in advanced!!