Abstract: When the power backup automatic switching device of the power station is in the state of charging and light load, if the bus PT is disconnected at this time, the backup automatic switching device will malfunction because the current does not meet the threshold value, resulting in the action of backup automatic switching in normal operation state. This paper analyzes the principle of countermeasures to prevent the malfunction of the substation under the condition of light load, and proposes a more optimized solution based on the example of the transformation of a substation, in order to find a solution that can be popularized and applied to prevent the backup under light load. A method of malfunctioning under operating conditions.