Measurement of PTP Synchronization Accuracy and Study of its Application to IP Networks of Japanese TSOs

Although the Global Navigation Satellite System (GNSS) is widely employed as a time synchronization method, its vulnerability to security threats such as jamming and spoofing has been pointed out. In contrast, the Precision Time Protocol (PTP), as defined by IEEE 1588, has attracted attention as a technology capable of providing high-precision time synchronization over IP/Ethernet networks. By operating PTP grandmaster devices without GNSS synchronization, it is possible to mitigate GNSS-related security risks while maintaining synchronized sampling timing between substations.

However, the impact of various PTP configuration parameters—such as delay measurement mechanisms—and differences of PTP features among switches on synchronization accuracy has not been sufficiently evaluated. This paper presents an empirical assessment of the influence of PTP configuration variations on time synchronization accuracy. Based on these results, we propose application strategies for IP networks used in power system protection by enumerating fundamental allocation patterns of PTP features on switches, evaluating their advantages and disadvantages, and identifying the most promising configurations.

Experiments were conducted using switches from different vendors equipped with 1 Gbps and 10 Gbps ports. Synchronization errors were measured under various PTP settings, including

End-to-End versus Peer-to-Peer delay mechanisms, One-Step versus Two-Step clock operation, and conditions with and without network load. The results indicate that the application of switches or routers equipped with PTP synchronization functions—namely Transparent Clock

(TC) or Boundary Clock (BC)—is indispensable to meet the requirements of current differential relays for transmission line protection and PMUs. Furthermore, when TC or BC is employed, differences in accuracy between One-Step and Two-Step modes or between End-to-End and

Peer-to-Peer mechanisms are negligible.

Finally, assuming a hierarchical topology for Japanese TSOs IP networks, six allocation patterns for PTP synchronization features on switches and routers were enumerated. For each pattern, we analyzed advantages, disadvantages, and feasible combinations of PTP configuration options, narrowing down to three promising patterns.