Noncircular Attacks on Phasor Measurement Units for State Estimation in Smart Grid

Abstract

With the evolution of phasor measurement units (PMUs) and the proposition to incorporate a large number of PMUs in future smart grids, it is critical to identify and prevent potential (zero-day) cyber attacks on phasor signals. The PMUs are the forefront of sensor technologies used in the smart grid and produce phasor voltage and current readings, which are complex-valued in nature. In this regard, the paper investigates potential attacks on complex-valued PMU signals and proposes the new paradigm of data-injection attacks, referred to as noncircular attacks. Existing state estimation algorithms and attack monitoring solutions assume that the PMU observations have statistical characteristics similar to that of real-valued signals. This assumption makes PMUs extremely defenseless against the proposed noncircular attacks. In this paper, we introduce the noncircular attack model, evaluate (both analytically and via experiments) the potential destructive nature of such attacks, propose a Bhattacharyya distance detector for monitoring the system against cyber attacks by transforming the detection problem to an equivalent problem of comparing innovation sequences in distribution via statistical distance measures, and propose a circularization approach, which enables the conventional detection algorithms to identify noncircular attacks.