Most of the existing power quality monitoring devices are mainly based on the internal clock to achieve time synchronization. However, due to the clock crystal oscillator error or damage and other problems, the monitoring device often has clock anomaly problems, which seriously affects the later data comparative analysis. In order to solve the problem of automatic detection of clock anomaly in power quality monitoring device, a clock anomaly detection method based on voltage sag homologous identification is proposed according to the characteristics of fast propagation speed and negligible time deviation of voltage sag in the system. Firstly, the voltage sag waveform data recorded by different monitoring devices are identified by homology, and then the time deviation of the same sag event recorded in different monitoring devices is compared to judge whether the clock of the monitoring device is abnormal according to the time deviation. The simulation data and measured data are used to verify the method. The results show that the method can accurately detect the clock anomaly of power quality monitoring device, and is of good accuracy and feasibility.

clock anomaly; homology detection; power quality monitoring system; voltage sag