Modified symmetrical component method for characterization of unbalanced voltage sags

Abstract

This paper suggests a modification in symmetrical component (SC) method, used for characterization and classification of voltage sags, by incorporating an angle, ɸ, in it. The ɸ is considered as an angle between drop in positive-sequence voltage components, associated with single line-to-ground and line-to-line faults. The modified formula is tested on two data sets of real power systems and compared with the SC method. The results suggest that this modification offers advantages of giving accurate comprehensive information on the nature of (i) voltage sag, (ii) associated fault, and (iii) faulted buses, simultaneously. This study aims to establish a precise characterization method for voltage sags due to faults in low-voltage resistance-grounded distribution systems (LVRGDS), as their more frequent occurrence and vulnerability of economic impacts to industrial customers than the shallow voltage sags due to faults in high-voltage solidly grounded transmission systems (HVSGTS). For this, the variations in φ, for different fault locations in LVRGDS and HVSGTS, are evaluated, resulting in large values of φ in LVRGDS. These larger values of φ establish better characterization capability, for voltage sags in distribution systems, with the proposed method than the SC method. Also, the capability of φ to identify the behavior of un-faulted phase voltages has been revealed. Copyright © 2015 John Wiley & Sons, Ltd.