The　construction　of　smart　grid　requires　that　the　relay　protection　especially　backup　protection　must　have　better　adaptability.　The　paper　proposed　a　self-adaptive　minimum　fault　isolation　method　based　on　the　fault　location　diagnosed　by　Centralized　Substation　Backup　Protection　System.　The　method　for　searching　breaker　tripping　sequence　based　on　Petri　net　is　proposed.　It　can　accurately　find　the　breakers　need　to　trip　in　local　backup　protection,　breaker　failure　protection　and　remote　backup　protection　and　has　good　adaptability　to　different　main　connections　and　different　operation　modes.　Centralized　backup　protection　system　forms　the　tripping　strategy　based　on　the　position　of　fault　element,　the　breaks　status　and　operating　signal　of　protection.　It　can　isolate　the　fault　quickly　and　minimize　the　blackout　zone.　©　2010　State　Electric　Power　Research　Institute　Press.