Recent blackouts of major power systems (PSs) clearly demonstrate the topicality of the blackout problem. The situation is further complicated by the necessity for PSs to survive under the competition and uncertain conditions. Based on the detailed blackout analysis, the dangerous overload of transmission grid is held as a key element giving start to the development of many cascading processes. Therefore, paying major attention to the overload as to the primary event, it is possible to prevent a blackout by fixing the emergency epicentre and blocking the development of cascading events and power plant outages. For the purpose of dangerous overload elimination the short-term splitting of power system can be used, followed by automatic restoration to normal operating conditions, thus transforming severe emergency into a short transient process.