Hello shduthi30

I hope you are doing good . As per your query, I would like to tell you about the exact reason behind not preferring delta connection for connecting sources. The real consumed power will be very short due to the delta connection as addition of one source with another source will not be possible. Three phase four wire system cant be established due to unavailibilty of  neutral point. The voltage occuring btw sliding will be equivalent to full line voltage in case of earth fault

Hope you found this answer helpful. Good luck for your future