Reclosing during a permanent fault subjects the transformer to secondary impacts,thereby increasing the likelihood of transformer damage.In this paper,a computational model for calculating the leakage magnetic field of a three-winding transformer operating in"high-medium-low"mode is first established.Subsequently,a nonlinear model for the axial vibration of winding coils is developed,and a dynamic calculation method for the axial pressure on the coils and spacers is proposed.Finally,the established model is utilized to evaluate the axial strength of a 110 kV transformer under reclosing operation conditions.The results indicate that during reclosing in the poorest operating condition,the leakage magnetic field of the transformer increases,vibrations become more intense,and the forces acting on the coils and spacers are greater,thereby increasing the possibility of axial instability in the transformer.These findings can provide a basis for the verification of operating conditions for transformers during reclosing.
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