A probabilistic model of power system disturbances

Power system stability analysis involves the study of the state trajectories of a power system in response to a disturbance. The system is usually presumed to be in a static equilibrium state when the disturbance is initiated. The disturbance causes a dynamic motion of the system state variables to either a new equilibrium condition or an unstable condition, which we usually regard as a system failure in some sense. The disturbance that initiates system dynamic behavior is of primary interest here. Qualitatively, the system disturbance may be large or small, and may be a simple step change in some parameter or a complex sequence of changes. We are interested in describing the disturbance not just mathematically, but probabilistically. Thus we seek a definition that will permit us to associate probabilities with disturbance events, such that the probabilities conform to an axiomatic definition of probability.