Operation of three-phase three-leg power transformers subject to voltage swell

This paper studies the effects of voltage swells on the behavior of three-phase three-leg power asymmetric power transformers. Based on electric and magnetic circuit topologies, a nonlinear model of a three-phase three-leg transformer is implemented for this study. Electromagnetic transient behavior exhibited in transformer voltages, currents and magnetic fluxes are computed and analyzed in time-domain. Simulations are performed for various voltage swell conditions with different magnitudes, starting and termination (recovery instant waveform) angles and durations. The impacts on the deterioration of power quality in input and output current and voltage waveforms are examined.