What is voltage sag?
The IEEE standard and the national standard "Power Quality Voltage Dips and Short-term Interruptions" (GB/T30137-2013) stipulate the definition of voltage sag: Voltage sag refers to the power frequency voltage at a certain point in the power system The effective value is temporarily reduced to 10%~90% of the rated voltage (that is, the amplitude is 0.1~0.9 (p.u.)) and lasts for 10ms~1min. During this period, the system frequency is still at the nominal value, and then returns to the normal level. Phenomenon. Voltage sag is measured as a percentage of remaining voltage. Short-term interruption means that the voltage frequency of one or more phases drops below 0.1p.u. and the duration is 10ms -1min.