Correlation-based Detection of PMU Time Synchronization Attacks

Real-time monitoring and control in power systems is increasingly dependent on Phasor Measurement Units (PMUs). PMUs depend on precise time synchronization, and thus it is essential to ensure the security of time synchronization. In this paper we consider the detection of low-rate time synchronization attacks against PMUs. Based on a general clock model and a PMU measurement model we provide a closed form expression for the correlation between the clock frequency adjustments and the measured PMU phase angles in the absence of an attack. Leveraging the intuition that an attack would affect the correlation between these two quantities, we propose a model-based and a non-parametric correlation-based detector for time synchronization attacks. We evaluate the proposed detectors using extensive simulations. Our results show that they outperform traditional change detection techniques for clocks with low accuracy, for which attack detection is most challenging.