Propagation of Voltage Sags and Under-voltages through Scott Transformers

Abstract

Scott transformers are a class of equipment that converts three-phase power into two-phase, four-phase and even three-phase power and vice versa. This paper investigates how voltage sags originating from the main three-phase network propagate through these transformers and aims to complement the existing literature on the effect of ordinary transformers on the propagation of voltage sags. The paper also includes an overview of three-phase voltage sags and their classification, as well as some technical details of Scott transformers. The results are presented using the example of a voltage sag with certain characteristics, but the proposed methodology of investigation can be applied to any generic voltage sag and, by extension, to any under-voltage event.