During auxiliary power switching

transient characteristics such as voltage fluctuations

phase shifts

and load impacts may cause relay protection misoperation or failure to operate

affecting power supply reliability. To address the coordination issues of high-voltage auxiliary transformer differential protection

overcurrent protection

and zero-sequence protection during the switching process

optimization schemes including differential and backup protection coordination

overcurrent protection time-delay coordination

zero-sequence protection selectivity coordination

and coordination between the automatic bus transfer device and protection logic are proposed. The proposed schemes effectively reduce the probability of protection misoperation and improve the reliability of auxiliary power switching.