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Megha

This is a stability phenomenon, where the power system looses its ability to control load bus voltage due to various reasons. This phenomenon can lead to failure of the total or partial power system due to interventions of various control and protection actions. The reasons for voltage instability could be - Failure to provide necessary power support to the loads as a consequence of power transfer limit. The power transfer limit is determined not only by the bus voltage phase angle, but also by bus voltage magnitude - Failure to meet power requirements due to equipments reaching their control and operating limits. Examples are transformer tap limits, generator reactive power supply capabilities. - Inconsistency in the load power requirements as function of bus voltage and power supply characteristics.