A new way to keep power grid time in sync—even when GPS fails

What is it about?

KEPCO has developed a practical, network-based time synchronization system to enhance the reliability of phasor measurement units (PMUs) used in wide-area monitoring systems (WAMS). In South Korea, GPS signals—traditionally used for time sync—are often disrupted by intentional jamming from North Korea and blocked in mountainous areas. To overcome these issues, KEPCO synchronized atomic clocks with Korea Standard Time (KST) using optical fiber from the Korea Research Institute of Standards and Science (KRISS). The precise time is then distributed to substations nationwide using the Precision Time Protocol (PTP) over existing optical ground wire (OPGW) networks. Field tests confirmed time accuracy within 10 nanoseconds to KST and 300 nanoseconds at distant substations, exceeding GPS performance. This cost-effective and secure approach avoids additional infrastructure and provides a reliable model for grid operators facing similar geographic or security challenges.

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Photo by taro ohtani on Unsplash

Photo by taro ohtani on Unsplash

Why is it important?

1. Solves a Real-World Problem South Korea faces frequent GPS disruptions due to jamming from North Korea and terrain-based signal blockages. These issues directly threaten the reliability of phasor measurement units (PMUs) and wide-area monitoring systems (WAMS)—key technologies for real-time grid stability. 2. Proposes a Practical, Scalable Solution KEPCO’s approach doesn’t rely on expensive or vulnerable GPS systems. Instead, it leverages existing infrastructure (optical fiber, substations, control centers) to implement a secure, high-accuracy time sync system—a model that other utilities can realistically adopt. 3. Improves Grid Reliability and Security By achieving nanosecond-level synchronization, KEPCO ensures trustworthy synchrophasor data, even in environments hostile to satellite signals. This enhances grid resilience, especially as renewables introduce more variability. 4. Supports Global Transition to Smarter Grids As countries aim for decarbonized, digitalized, and decentralized power systems, accurate timing becomes essential. This paper contributes a field-tested, cost-effective solution to one of the most pressing technical barriers in that transition.