Power System Reliability Evaluation Using Stochastic Load Flows

This paper presents a simulation procedure for bulk power system reliability evaluation. The operation of the system under forced or scheduled outages of circuits and/or units is simulated via a stochastic load flow. An efficient stochastic load flow methodology is presented, which computes circuit loading and bus voltage probability distributions from a given load probability distribution. The output of the stochastic load flow is utilized to compute the conditional probability of system failure according to predefined criteria. Circuit overloads and bus undervoltages/overvoltages are utilized as system failure criteria. The frequency and duration method is employed to compute bulk power system reliability indices. Upper and lower bounds on the reliability indices are computed, which converge to the true values of the indices as the number of contingencies simulated increases. The paper presents simulation results with two systems: (a) a small 9-bus system to demonstrate data requirements, and (b) the 500 kV/230 kV system of Georgia Power Company to demonstrate the applicability of the method to actual systems.