Probabilistic online risk assessment of non-cascading and cascading transmission outage contingencies

摘要

Power grids have traditionally been designed to withstand without resulting in cascading events transmission outage contingencies of the N-1 or N-2 kind. However, in actual operation, power grids are potentially vulnerable to cascading outages. Reliable operations therefore require a risk-based approach to monitoring and managing the probability and impact of potential cascading outages. This paper defines and quantifies a measure that relates to the vulnerability of the power grid to cascading outages. The approach is to simulate and identify potential cascading modes (PCM) and to compute the probability and impact of each stage of the cascade and display the risk of each potential cascade stage on the two-dimensional display of likelihood and consequences. In this display, the traditional N-1 or N-2 contingencies will also be plotted for comparison. This approach enables grid operators to be fully aware of not only the contingencies for which they are required to assess and mitigate but also the potential cascading modes. This places both types of potential adverse events on the same basis for comparison. When the risk level of a potential cascading mode approaches or exceeds the risk level of all the N-1 contingencies (or N-2, if it is the reliability standard), then the operators will be well advised to take corrective actions to manage the overall risk of blackouts. Computation examples of applying this method are illustrated in this paper.