The influence of transformer winding connections and grounding in the indices of voltage sags

This paper analyzes the influence of transformers winding connection and transformers neutral grounding mean on the prediction of voltage sags indices according to Brazilian standard Prodist. The case study was performed on the IEEE 13 Node Test Feeder. Voltage sags were obtained by symmetrical and asymmetrical faults simulations in all systems nodes. One node with a MV/LV transformer was chosen to be a sensitive customer connection node. Several simulations changing the transformer connection and transformer neutral grounding were performed. It was found that both features have strong influence on the voltage sags indices at the sensitive customer node.