Abstract: The present invention discloses a system protection scheme comprising of at least two system protection terminals (18), introduced at suitable locations in an electric power system (1). The system protection terminals (18) are interconnected by a communication system (22), preferably using a substantially dedicated communication resource. At least-two of the system protection terminals (18) are equipped to collect measurement signals (72) associated with time stamped voltage or current values of the power system at that particular location or quantities derivable therefrom. The measurements are evaluated and related data is spread to other system protection terminals (18). At least one of the system protection terminals (18) is equipped to evaluate the existence of poorly damped power oscillations in the power network and if necessary provide control signals (74) to power system actuating units. The evaluation is preferably based on changes in the node angle differences between the measurement locations.