Examining criticality of blackouts in power system models with cascading events

As power system loading increases, larger blackouts due to cascading outages become more likely. The authors investigate a critical loading at which the average size of blackouts increases sharply to examine whether the probability distribution of blackout sizes shows the power tails observed in real blackout data. Three different models are used, including two simulations of cascading outages in electric power transmission systems. They also derive and use a new, analytically solvable model of probabilistic cascading failure which represents the progressive system weakening as the cascade proceeds.

1. Introduction

Analyses [5], [8] of 15 years of North American blackout data [1] show a probability distribution of blackout size which has heavy tails and evidence of power law dependence in these tails [5], [8]. These analyses show that large blackouts are much more likely than might be expected from, say, a Gaussian distribution of blackout size in which the tails decay exponentially. The power tails of probability distributions of blackout size merit attention because of the enormous cost to society of large blackouts.