An underfrequency load shedding protection system for stably managing a power system by recovering a power system frequency to within a predetermined range when the power system frequency drops. An underfrequency level detection unit judges an underfrequency level of the power system frequency when the power system frequency drops resulting from power generation shortage in the power system and a load shedding unit sequentially sheds loads determined in advance based on a staying time when the power system frequency stays at any one of the underfrequency levels judged by the underfrequency level detection unit and sheds on this occasion more loads quickly when the underfrequency level at which the power system frequency stays is large.
