Maximizing Branch Power Flows as a Descriptive Structural Metric for Electrical Networks

Abstract

This paper describes an optimization-based procedure that identifies the maximum power flow that each branch in an electrical network could be exposed to. The procedure uses a linear optimal power flow formulation that determines the flow-maximising generator dispatch and loading conditions for each branch in turn. This theoretical upper bound on the power flow that a branch could be exposed to is termed its loadability. The paper proposes this loadability as a descriptive structural metric that helps reveal the fundamental origin of congestion in power system. For instance, it is insightful to compare a branch's loadability with its as-built thermal capacity, to identify those branches that are most congestion-prone, or alternatively, those lines which can never exploit their full available capacity. In the six test systems studied, it is found that there is wide variation in the loadability of the various branches, where some would be loaded well beyond their thermal limits by particular generating schedules, whereas other branches can never operate beyond even a fraction of their thermal capabilities. Low branch reactance is found to be a key driver of high loadability in power systems, and this suggests new approches to alleviating transmission system congestion.