This paper offers new principles of power system protection to avoid development of cascade emergencies or blackouts and power system self-restoration. Blackouts occur as the result of dangerous emergency overloading. These are followed by cascade tripping of lines and power plants and, finally, by a power systems collapse. One of the real tools for prevention of power system collapse is its preventive short-term sectioning in the optimal places further followed by restoration of the operating condition using automatic synchronization. Such a process is to go automatically, without staff participation, so that the emergency could be quickly eliminated. The authors show that for this purpose it is possible to make automatic re-closing using a device for synchronism control. The results of computations performed using simplified formulas and a mathematical model indicate the area for application of this approach. The algorithm and formulas are not given in this paper because of its limited length.