Characteristic of voltage dips (Sags) in power systems

This paper analyzes the characteristic of voltage dips in power systems with special emphasis on unbalanced dips and symmetrical components analysis. A generalized dip model is built for all unbalanced dips, taking into account the fault types, transformer types and load connections. It shows the transformation for different types of unbalanced dips. The characterization results in a so-called Remaining Complex Voltage (a generalized magnitude and phase angle shift) for balanced and unbalanced dips as well as a factor, related to the rotating machine contribution to the source impedance for unbalanced dips. It is shown that the factor is close to unity, so that both balanced and unbalanced dips can be characterized with one phasor.