Power quality monitoringdeviceIn Chinese, voltage sag refers to the system frequency remaining at the nominal value and then returning to normal level when the user's duration drops to 10% to 90% of the rated voltage or current within 0.5 cycles to 1 minute due to a system fault or interference, with an amplitude ranging from 0.1 p.u. to 0.9 p.u. (per unit value). Internationally, it is generally believed that power supply interruptions with voltage amplitudes below 0.1p.u. (per unit value) or greater than 0.5 cycles are considered power outage faults for both sensitive and strict users.

Voltage sag may cause production interruptions or an increase in defect rates for certain users, and the power supply recovery time depends on the action time of automatic reclosing or automatic function conversion devices. Therefore, traditional mechanical circuit breakers can no longer meet the requirements for sensitive and strict electrical loads. Currently, customized power technology is mainly used to solve these problems.

Voltage rise refers to the increase in the effective value of the voltage to more than 110% of the rated value. A typical value of 110% to 180% of the rated value is called voltage rise, which temporarily exceeds the nominal value by more than 10%. The system frequency remains at the nominal value, with a duration of 0.5 cycles to 1 minute, and an amplitude of 1.1 p.u. to 1.8 p.u. (per unit value).

For photovoltaic power generation, users are not only users of electricity, but also producers. Due to environmental impacts, photovoltaic power generation has high harmonic content and unstable power generation, all of which cause grid pollution and affect power quality. Therefore, in order to prevent serious pollution of power quality, the country has strict standards for photovoltaic power generation.

Photovoltaic power stations must be equipped with Class A online power quality detection devices that meet the IEC61000-4-30 "Electromagnetic Compatibility - Part 4-30: Testing and Measurement Techniques - Power Quality" standard when connected to the power grid. Through these standard specifications, the impact of photovoltaic power generation on power quality can be reduced. So household photovoltaic power generation requires the installation of an energy quality monitoring analyzer. However, the analysis of power quality currently requires careful screening of manufacturers and brands, as there is a mixed bag of fish and dragon in the market.