On security criteria in power systems operation

In this paper a new way of minimizing the risk of cascading events is presented. A method to dispatch the system in such a way that the risk for subsequent line trips after the first initial event is minimized is presented. This method is based on the assumption that the probability of a line trip is a continuous increasing function of the line overloading. A slight overload implies a smaller probability of a line trip than a larger overload does. The new method is compared with the N-1 criterion and it is shown that the proposed method makes a system more robust against multi contingencies than the N-1 criterion.