Distributions of cascade sizes in power system emergency response

Following disturbances to a power system triggering emergency responses such as protection or load/generation shedding, several factors affect the way in which these responses may cascade through the network. Beyond deterministic factors such as network topology, in this paper we aim to quantify the effect of correlations in power disturbances. These arise, for example, from common weather patterns causing correlated forecast errors in renewable generation. Our results suggest that for highly connected networks, the cascade size distribution is bimodal and positively correlated disturbances have the benefit of reducing cascade size. For a fixed network the latter relationship is observed to be stronger when emergency responses are rare, which is consistent with the mathematical theory of large deviations.