In the operation of power grid system, short circuit fault, start-up or switching of large capacity equipment, lightning strike and so on are the main reasons for unstable voltage sag. With the continuous development of the national economy, all kinds of precision instruments and equipment are put into use, and the demand for voltage is higher and higher. The power quality online monitoring device is installed in the power grid system to carry out real-time online monitoring of power quality.

Impact of voltage instability on the automotive industry: in the automotive industry, a large number of industrial robots are used. When the robot controls the drilling, cutting and other precision machining or spraying equipment for metal parts, if the voltage temporary event occurs, it will cause the robot misoperation and cause the product scrapping.

Impact of voltage instability on semiconductor, precision electronics and other industries: when voltage sag occurs, if the equipment can not make timely action to the change of power supply voltage, it may cause the possibility of failure. When the equipment stops working, the quality of the products produced declines. It will cause the whole product line to stop running, causing the chip and motherboard to be burned.

At present, the unstable voltage rise and drop has caused direct economic losses of several billion yuan annually to petrochemical, semiconductor, papermaking, chemical, pharmaceutical, textile and other industries in China, and the indirect losses are immeasurable. Therefore, it is necessary to find out the source of voltage instability and carry out power quality control.

In power quality problems, the fluctuation, drop, sudden rise, imbalance and harmonic of power grid voltage will affect the power quality. Therefore, it is necessary to carry out the system power quality test and evaluation. It is necessary to install the power quality online monitoring device to monitor the power quality in the power grid in real time, which can capture the harmonic, voltage fluctuation, flicker and power on site Three phase imbalance and other common solutions for power quality improvement.