Reliable GPS-based timing for power systems: A multi-layered multi-receiver architecture

Synchronized voltage and current phasor measurements provided by phasor measurement units (PMUs) have the potential to augment power system monitoring, control, and protection functions. PMUs use the Global Positioning System (GPS) to synchronize measurements across a wide geographical area. Unfortunately, low-received-power, unencrypted civil GPS signals are vulnerable to jamming and spoofing attacks. Accidental receiver malfunction can also lead to incorrect position/time solutions. This paper presents a multi-layered multi-receiver architecture that hardens GPS-based timing against jamming, spoofing, and receiver errors. Our architecture integrates eight countermeasures in all layers of receiver signal and data processing; most of the countermeasures exploit the static and networked nature of time reference receivers. We define five threat models, and qualitatively analyze the effectiveness of each countermeasure against each threat model. The analysis demonstrates that the redundant, independent but complementary countermeasures provide high reliability and robustness.