Evidence for self-organized criticality in a time series of electric power system blackouts

We analyze a 15-year time series of North American electric power transmission system blackouts for evidence of self. organized criticality (SOC). The probability distribution functions of various measures of blackout size have a power tail and rescaled range analysis of the time series shows moderate long-time correlations. Moreover, the same analysis applied to a time series from a sandpile model known to be self-organized critical gives results of the same form. Thus, the blackout data seem consistent with SOC. A qualitative explanation of the complex dynamics observed in electric power system blackouts is suggested. Index Terms--Blackouts, complex systems, power system security, reliability, risk analysis, time series.