Clock Synchronization Method of Feeder Terminal Unit Using Power Frequency Voltage Signal

Clock synchronization protocols that are commonly used in distribution automation, such as simple network time protocol, have a large synchronization error due to inconsistent round-trip time of clock synchronization commands. Based on the fact that the phase angle difference of the same phase power frequency voltage signal on the same distribution line is very small, a clock synchronization method using the phase angle of power frequency voltage as the time reference is proposed. The feeder terminal unit for clock synchronization should agree in advance the corresponding power frequency voltage phase when the clock synchronization command is sent. The sender sends the timing command when the voltage reaches the prescribed phase angle. After receiving the timing command, the receiver marks the time when the previous voltage is at the prescribed phase angle as the reference receiving time. The error caused by the inconsistencies of the command round-trip is avoided by marking the same conventional phase. Theoretical analysis and experimental verification shows that the clock error is less than 1 ms when the round-trip delay time is less than 20 ms. © 2019 Automation of Electric Power Systems Press.