PMU-based Line Differential Protection under GPS Spoofing Attack

Many power grid applications rely on the time synchronized measurement data collected by phasor measurement units (PMUs) and or Merging Units (MUs)). The synchronization of data from multiple PMUs and MUs relies on the global positioning system (GPS) to provide the time reference. The civilian GPS receivers used in PMU operate according to the publicly available mechanism. Therefore, attackers can easily generate false GPS signals with low-cost portable devices. During the spoofing attacks, the signal received by the PMUs and MUs is arbitrarily modified by the attacker without being detected, leading to the malfunction of other applications in the power system including transmission line protection. In this paper, we investigate the effect of GPS spoofing attack on transmission line differential protection schemes based on PMUs, including percentage differential method and alpha-plane protection method. The mis-operation of these relays is observed during GPS spoofing attacks. In addition, we propose a quasi-dynamic state-estimation-based method to detect GPS spoofing attacks, identify the affected PMUs, correct the compromised data, and enable the continuous and reliable operation of the relays. Numerical results show that the proposed method detects the GPS spoofing successfully and the recovered measurement data eliminate the misoperation of line differential protection