Abstract: Based on the general situation of the first implementation of the double-bus expansion to dual-busbar-dual-segmented project in smart substat of the power grid of southern Hebei, reasonable process is studied according to the operation content and field equipment status, and the method of identifying the risk points of each process is proposed and the safety measures are prepared according to the three lines of defense.The engineering experience of constructing network islands with hardware isolation measures and conducting tri-comparison for configuration files are summarized to provide references for subsequent and similar expansion projects.