Analytical analysis of transformer interaction caused by inrush current

This paper analyzes the phenomenon of sympathetic interaction between transformers which is very likely to occur when a transformer is energized on to a system where are other transformers already connected. This interaction significantly changes the duration and the magnitude of the transient magnetizing currents in the transformers involved and may lead to maloperation of some power protections. This article presents the formation process of sympathetic inrush current through the flux analytical expression and bias flux attenuation between two parallel operation transformers. After that, the reasons of sympathetic inrush current generation are illustrated. Presented analytical analysis is valuable for comprehensive understanding of sympathetic inrush current, estimating the reasons of generation and eliminating it.