Identifying high risk N-k contingencies for online security assessment

It is impractical to analyze all of the possible contingencies in a large-scale interconnected power network. Therefore, a standard approach is to analyze only a subset of the contingencies. The normal method of selecting this subset is via use of the so-called N-1 rule. This paper goes a step further by proposing a new method of forming a contingency list, based on substation configuration obtained from topology processing data and probability analysis of protection system failures. This method is particularly suited for online security assessment. Protection system failures assessed include stuck breakers and failure to operate. The method is described via application to a single substation, verified using the IEEE-RTS96, and illustrated using topology data from a large utilities EMS.