The Influence of Generator Scheduling and Time-Varying Fault Rates on Voltage Sag Prediction

This paper discusses the influence of generator scheduling and time-varying fault rates on the stochastic prediction of voltage sags. Typically, in the stochastic prediction of voltage sags, the annual expected sag frequencies (ESFs) at sensitive load points are calculated by assuming that the operating conditions and topology of the power system remain unchanged and fault rates of system components are constant throughout a year. In this paper, in order to obtain reasonable accuracy in predicting the annual ESFs at sensitive load points, the variation of fault rates due to adverse weather and the effect of generator scheduling are considered. The study was performed on the IEEE 30-bus test system. Two buses were randomly selected and the ESFs at the selected buses were calculated for different cases (i.e., with and without incorporation of time-varying fault rates and the operation schedule of generators in the system).