Multi-timescale Simulation, Risk Assessment, and Mitigation of Cascading Outages

Cascading outages in electric power grids are dependent outage processes triggered by one or a set of initial faults. Cascading outages gradually impact and deteriorate transmission systems and may cause large blackouts as well as massive losses. Cascading outages often involve complex processes and various timescales. This chapter first introduces a multi-timescale cascading outage model using a quasi-dynamic simulation method. The model establishes a framework for simulating interactions among dynamics in quite different timescales. Moreover, due to the complex mechanism of cascading outages, its development is usually considered as non-deterministic, and thus probabilistic models are commonly used to model the possible paths. The number of possible sequences of cascading outages is huge and is computationally intractable to enumerate them for simulation and analysis. In this chapter, we develop tree formulation of cascading paths and introduce tree search techniques that enable efficient identification of high risk cascading outages, evaluation of cascading risk, and providing optimal mitigation strategies.