A method for operating a storage and retrieval unit (3) is specified, in which a rail line (1)/power-supply rail (6) is set to a risk-operation voltage when a risk posed by the storage and retrieval unit (3) is detected. In the storage and retrieval unit (3) the level of the voltage applied to the rail line (1)/power-supply rail (6) is measured and a current path between the rail line (1)/power-supply rail (6) and a drive motor (5, 5a . . . 5c) of the storage and retrieval unit (3) disconnected when the voltage measured is below a threshold value associated with a risk situation. Furthermore, a storage and retrieval unit (3) as well as an automated rack storage system for performing the proposed method is specified.