The paper defines a new term called ‘frequency factor’ and develops a method which utilises this factor to detect change in fundamental components of power-system frequency. A straight-line fit algorithm then optimally computes the average frequency deviation and average rate of change of frequency from the oscillatory response of any generator busbar caused by a sudden imbalance in generation and load demand in the system and predicts the amount of load to be shed. Results of computer simulation with a sample power system were also given in the paper.