Investigation and modelling of sympathetic inrush due to transformer energization

This paper presents a preliminary study of sympathetic inrush - a phenomenon when an already energized transformer experiences unexpected saturation during the energizing of another transformer connected in parallel. Power transformer can be saturated, giving rise to transients which lead to overvoltage and overcurrent. With the increase of distributed generations that can exaggerate more switching events, transients will become prevalent in such an operating environment. This can also bring power quality variation. Detailed MATLAB-Simulink models are developed and a small scale laboratory experiment using two parallel transformers has been set up to observe the sympathetic inrush interaction and the effect of point-on-wave switching. The simulation results are presented and the analytical calculations are shown to be validated by experiment.