Predicting Equipment Outages Due to Voltage Sags

A methodology for predicting the number of equipment outages per year due to voltage sags is presented, allowing to evaluate their amplitude and duration. The methodology is based on Monte Carlo simulation of the network operation considering the stochastic nature of power system faults characteristics (location, type, and resistance) and the probabilistic nature of successful fault clearance by the primary protection systems. Equipment susceptibility to voltage sags is included in the methodology by considering the standardized equipment ride-through capability curves. The methodology outcomes are probability distribution functions of the number of equipment outages per year, thus allowing to characterize outages by using average or percentile values obtained from the distribution functions. An application example is presented, considering two different equipment types connected to different sites of the IEEE Reliability Test System, the corresponding number of outages being assessed. Results highlight the need to combine equipment and network performance to assess compatibility.