what is open delta connection and where and when is it used? Today as i was doing secondary injection for the PT circuits - i had noticed that the PT secondary side had three phase voltages (Va.Vb and Vc)of which Voltage b(Vb) was grounded. Latter i had come to know that this type of PT is known as Open Delta PT and is a 3-Wire Delta, 2½-Element, 2 PT, 3 CT connection. I am a bit confused as to why they go for such a type of connection. Is there any advantages. Is it that they only want a ph-ph voltage value? In that case - the selector switches available at site have Ph-Ph selection and Phase to Neutral selection. So now i guess we will have to change the selector switch so that it will only have Ph-Ph selections.