Voltage Sags Mitigation on Distribution Utilities

Voltage sags are important to industrial reliability. Modern process controls are often sensitive to voltage sags, that may cause significant production outages. World-wide experience proves that a main origin of voltage sags affecting customers are short circuits on utility lines, with special reference to the overhead radial distribution ones. Since the voltage sag during the fault is proportional to the short-circuit current, an effective fault-current limitation by means of a device connected at the beginning of the most exposed radial feeders will limit the expected voltage sag amplitude and improve the system power quality. In the paper a proposal for a simple but effective fault-current limiter is given and discussed.