Environmental Data and the Assessment of Electric Grid Reliability

Heavy weather (wind, rain, snow, and hail) is significantly correlated with power interruptions. Analyzing and reporting reliability metrics usually incorporates a two-bucket approach: data is split into major event days and day-to-day operations. According to IEEE 1366-2003, major event days are defined as those with a standardized measure of interruption that is greater than 2.5 standard deviations from normal. However, grid interruptions in the “day-to-day” category can still be highly correlated with environmental data, particularly high winds. We give examples of how correlations with independent environmental data can be important for understanding grid reliability, and may prove to be a scientifically defensible approach for future reliability reporting.