Abstract: In the daily operation and maintenance of the substation, it is necessary to switch between different power sources within a fixed maintenance cycle to ensure the usability, safety and integrity of dual power sources. Although it is a dual power supply, there is still a brief power outage when switching back and forth between the two power supplies. Therefore, strictly speaking, the reliability of dual power sources is significantly enhanced compared to single power sources, but there is still a problem of intermittent power outages. we accord the actual situation on site to study the AC/DC alternating test uninterrusted power supply device in the substation, design a power supply bypass to effectively avoid indirect power outages and equipment impacts during the rotation experiment of the AC/DC system in the substation. At the same time, a complete electrical locking logic is set up to avoid power short circuit closing accidents caused by misoperation