Voltage recovery after unbalanced and balanced voltage dips in three-phase systems

This paper studies the recovery of the voltage after a voltage dip due to a fault in a three-phase system. The instant of voltage recovery corresponds to the instant of fault clearing. For single-phase and phase-to-phase faults, a single point-on-wave of voltage recovery can be defined. For two-phase-to-ground and three-phase faults, the recovery takes place in two or three steps. The voltage recovery is described in a systematic way by using a classification of three-phase unbalanced voltage dips. The voltage recovery needs to be modeled correctly for studies of equipment immunity against voltage dips.