Time-domain finite-element technique for quantifying the effect of sustained ferroresonance on power transformer core bolts

Detailed investigation of the effects of ferroresonance on power transformers requires a method that is able to quantitatively and topologically assess the core saturation and the stray fields attributed to flux redistribution. This study describes a time-domain finite-element approach to model a ferroresonance condition and quantify its effect. More specifically the model generates sustained ferroresonance waveforms and, crucially, also allows examination of the effect of the resulting high core fluxes on the transformer core clamping bolts. Two benchmarking concepts are used to aid this: (i) the space-averaged permeability variation and (ii) a topological calculation of flux variation within the core.