Research on classification of voltage sag sources based on recorded events

In recent years, with the widely application of power electronic devices and stringent requirement of industrial process, voltage sag has caused much attention in many countries. To design effective and efficient mitigation and management strategies, it is essential to have accurate classification of voltage sag sources. In this paper, based on the analysis of massive voltage sag events in the grid recorded by online power quality monitoring systems in several different regions in China, a more extensive and practical classification of voltage sag sources is given. The voltage sags are divided into eight categories due to short circuit faults with symmetric and asymmetric faults included, transformer energizing, induction motor starting, lightning faults, self-extinguishing faults, the combined action of short circuit faults and heavy load starting, upgrade faults and multistage voltage sags. For each category of the voltage sag sources, both the instantaneous value and the root mean square (RMS) value of the waveform of the typical recorded events are given. In addition, the reasons are analysed and the waveform characteristics are summarized for each category of the voltage sag sources. Finally, the frequencies of eight categories under different voltage levels and the statistical result analysis are given.