The influence of transformer winding connections on the propagation of voltage sags

This paper presents the influence of different types of transformer winding connections on the propagation of voltage sags caused by symmetrical and asymmetrical faults in the power system. Single and multiple transformers are considered. A particular propagation of voltage sags from customer buses to industry facilities through the transformers employed at the entrance of the facilities is highlighted in the study. Different winding connections, dominantly used in the U.K. distribution networks, were modeled at the service transformers. The study was performed on a generic distribution network, and a bus from the 11-kV distribution network was randomly selected. It was found that the performance of voltage sags inside the industry facility is a function of transformer connections used at the service transformer.