A peak time shifting phenomenon in transformer axial short-circuit electromagnetic force due to the coupling of electromagnetic-axial vibration

Accurately calculating axial electromagnetic force is essential to analyse transformer winding axial stability. Prior research has mainly focused on the effect of winding structure on static axial electromagnetic force and studying vibration by substituting the static force in a time-varying function. However, the coupling effect between axial electromagnetic force and winding vibration has not been addressed, and no calculation method for the axial electromagnetic force that considers both winding meso-structures and vibration coupling effects has been proposed. Previously the authors presented an electromagnetic force calculation model that considers winding structure characteristics, and an iterative algorithm for magnetic-structure coupling calculation. Currently, the winding vibration model was first proposed and the dynamic calculation method was formulated. By applying the method to a typical 110kV transformer, the spatial-temporal distribution of winding axial short-circuit electromagnetic force was obtained. It was found that the peak value of the axial short-circuit electromagnetic force of some windings appears at the second or third peak moment of the short-circuit current, which is called as peak time shift phenomenon. Further stress analysis indicates that existing evaluation methods may overestimate the short-circuit resistance of windings by only considering short-circuit electromagnetic force under maximum peak of short-circuit current. Based on the concept of iterative coupling, the magnetic-structure coupling calculation was conducted for a typical 110kV transformer, taking into account the characteristics of the winding structure and the coupling effect of vibration. And the peak time shifting phenomenon of axial electromagnetic force was first revealed. Those results indicate that an overestimation of the winding short-circuit resistance would occur by only considering short-circuit electromagnetic force under maximum peak of short-circuit current.image