Ensuring power system security against contingencies

A power system is secure against a given contingency if it operates within acceptable operating limits before and after the occurrence of the contingency. In practice, it is not possible to secure a power system against all possible contingencies. Therefore, only the most critical contingencies (imminent disturbances) are considered. The paper gives an overview of power system security and different ways of loosing stability. Then, a statistical learning based technique for determining the boundary of the secure operating region in terms of pre-contingent state of the power system is reviewed. The paper discusses possible applications of the boundary and some issues related to practical application of this method.