Power quality monitoring is mainly through the use of up to standard tester or power quality online monitoring device, some important nodes in the power grid and power quality related indicators are monitored, and according to the standard value of each index for comparative study, the original data analysis process.

At present, the disputes and power grid accidents caused by power quality are on the rise, so it is more and more important to monitor power quality and control power pollution. The establishment of a perfect power quality monitoring system is very important for the power quality management and improvement of the whole power system and the healthy development of the whole economy.

The power quality monitor is a kind of instrument installed in the substation to monitor the indicators of power quality in real time. By collecting the real-time voltage and current on site, and through a series of calculations, the indicators of power quality can be displayed directly on the LCD screen.

After the monitoring terminal detects the voltage event, it should record the occurrence time, duration and amplitude of the voltage event. The A-level monitoring terminal uses half wave refresh voltage RMS to detect voltage events. The time of a cycle is determined by the frequency measurement of the reference channel. For multi-phase system, the voltage sag event starts when one or more channel voltages are lower than the threshold, and ends when all measured channels are higher than the threshold and the hysteresis voltage is added. The voltage sag event starts when the voltage of one or more channels is higher than the threshold, and ends when all channels are lower than the threshold and the hysteresis voltage is subtracted. The sag depth is the maximum of all channels in the process of sag.