In　this　paper　the　defects　of　the　existing　back-up　protection　and　other　auto-mechanisms　are　investigated　in　detail　first.　Then　a　new　wide　area　security　protection　of　transmission　section　(SPTS)　based　on　wide　area　measurement　system　(WAMS)　to　prevent　the　occurrence　of　blackout　is　presented.　A　new　concept　of　parallel　transmission　section　(PTS)　is　proposed　to　identify　transmission　lines　suffering　from　flow　transferring　greatly　after　the　isolation　of　overloaded　line.　And　the　method　of　searching　for　PTS　based　on　graph　theory　on-line　is　also　stated.　And　then　the　concept　of　flow　transferring　relativity　factor　(FTRF)　based　on　direct　current　power　flow　is　proposed　to　estimate　the　flow　transferring　on　the　PTS.　If　another　new　overload　will　be　caused　on　the　PTS　by　flow　transferring,　fast　efficient　emergency　control　actions　such　as　generator　and/or　load　shedding　is　necessary　to　eliminate　the　overload　quickly.　Accordingly,　an　advanadvanced　heuristic　emergency　control　algorithmced　heuristic　emergency　control　algorithm　based　on　sensitivity　factors　is　put　forward.