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An approach to adaptive underfrequency load shedding, a procedure for protecting electric power systems from dynamic instability and frequency collapse, is presented. It consists of two main stages. In the first stage, the frequency and the rate of frequency change are estimated by the nonrecursive Newton type algorithm. By using the simplest expression of the generator swing equation, in the second stage the magnitude of the disturbance is obtained. The UFLS plan is adapted to the magnitude estimated, to obtain a more efficient system for operation during emergency conditions. Results of procedure testing are demonstrated through computer simulations by using a 10-machine New England test system.