Control　units　of　the　kernel　module,　the　fault　simulation　module　and　the　arcing　fault　device　module　used　in　a　physical　simulation　system　of　distribution　network　are　designed　on　the　basis　of　Programmable　Controller　(PLC)　with　structured　and　modular　software.　The　analog　circuit　breaker　on-off　control,　three-remote　data　acquisition　control,　fault　simulation　control,　arcing　control　are　realized　by　using　the　designed　units.　And　simulation　fault　of　system　can　be　removed　by　interruption　way　and　the　response　time　is　no　more　than　ten　cycles.　Results　of　PSCAD　simulation　are　in　accordance　with　the　running　experiment　results　of　physical　simulation　system,　which　shows　that　these　designed　control　units　can　meet　the　control　requirements　of　the　physical　simulation　system.　©　2017,　Power　System　Protection　and　Control　Press.　All　right　reserved.