The invention disclose a kind of method and system for preventing electric network from collapsing. The method and system contains underfrequency load-shedding, and uses transmission line and fault signal of machine set to excise accessory load in power-fail area, prevents stability destroyed to network splitting caused by large scale overload of transmission line and frequency collapse caused by seriously insufficient wattful power in power-fail area and too high frequency to parallel network splitting caused by seriously superfluous wattful power in power-rich area. So a kind of electric network collapsing accidents, such as New York blackout in American in 2003, total blackout in Canada in 2003 and island-wide blackout in Taiwan, can be prevented. |