Impact of voltage sags in practical power system networks

Voltage sags are momentary dips in voltage that may cause misoperations to the customer's sensitive loads of the power utility and are recognised as the most important power quality problems. The scope of the work presented in this paper includes: (i) critical awareness on the importance of characterization and impact of voltage sags, (ii) identification of a suitable algorithm for voltage sag analysis, and (iii) demonstration of the chosen methodology on a practical power system case study. The ability to estimate voltage sag characteristics offers an opportunity to evaluate alternate configurations. The overall methodology proposed utilizes the standard software packages of load flow analysis, short circuit studies and interface modules developed specifically for this problem. Methodology for sag analysis includes the characteristics of sag, like magnitude, duration, phase angle jump, sag frequency, some of the important factors affecting sag magnitude, and area of vulnerability for radial distribution systems.