The SOURCE I transformer is connected through I/C-I incoming breaker to BUS I. Similarly, SOURCE II transformer is connected through I/C-II incoming breaker to BUS II. BUS I and BUS II are connected using the TIE breaker. There are several bus transfer scenarios depending upon the choice of the normal supply to the motor buses. 1  Normally closed TIE breaker: The entire motor bus comprising BUS I and BUS II is transferred between SOURCE I and SOURCE II.