Different methods for classification of three-phase unbalanced voltage dips due to faults

This paper presents a systematic and an intuitive approach to the analysis of voltage dips due to faults in three-phase systems. The systematic approach (symmetrical component classification) is based on the decomposition of the three phase voltages in symmetrical components. From positive and negative-sequence voltage a generalised magnitude for the event is defined as wen as a second characteristic that quantifies, among others, the load effect on the voltages. Next to the systematic approach a more intuitive approach is introduced. This so-called ABC classification uses only the generalised magnitude as a characteristic. This method is more appropriate as a basis for testing of equipment and for interpretation of the propagation of dips through the system. The basics behind the symmetrical-component classification are explained from a systematic analysis of non-symmetrical faults. The two methods are compared and the effect of dynamic load on the characteristics is discussed. (C) 2003 Elsevier Science S.A. All rights reserved.