Results from Global Positioning System (GPS) spoofing tests against Phasor Measurement Units (PMUs) are presented, demonstrating that PMUs are vulnerable to spoofing attacks. A GPS spoofer can manipulate PMU time stamps by injecting a counterfeit ensemble of GPS signals into the antenna of the PMU’s time reference receiver. A spoofer-induced timing error of only a few tens of microseconds causes a PMU to violate the maximum phase error allowed by the applicable standard. These and larger errors can give automated or human power grid controllers a false perception of the state of the grid, leading to unnecessary, and possibly destabilizing, remedial control actions. To emphasize this threat, it is shown that a particular PMU-based automatic control scheme currently implemented in Mexico, and whose control architecture and setpoints have been published in the open literature, could be induced by a GPS spoofing attack to trip a primary generator.

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D.P. Shepard, T.E. Humphreys, A.A. Fansler, "Evaluation of the Vulnerability of Phasor Measurement Units to GPS Spoofing Attacks," International Journal of Critical Infrastructure Protection, Vol. 5, December, 2012.