变压器绕组非线性动力学模型及多次短路冲击下的振动特征

Transformer windings suffer huge electromagnetic forces and show significant non-linear vibration with harmonics during external short-circuits. To further investigate the vibration characteristics under multiple short circuits, nonlinear mechanical properties of pressboards were considered in establishing windings’ dynamic model. The thickness shrinkage of paperboards from cumulative effect was studied. Then, the vibration entropy (VE), dominant component ratio (DCR), and the root mean square (RMS) of harmonics were deployed to illustrate the vibration harmonics. Furthermore, the influence of current amplitude, windings’ natural frequencies, and the accumulative effect on the VE, DCR and RMS are analyzed. Lastly, multiple short circuits tests were conducted on a retired 220 kV power transformer. The results show that the nonlinear mechanical properties of pressboards lead to harmonics at multiple times of 50 Hz over 100 Hz. At lower short circuit current, the RMS and VE increase with the increasing current amplitude, while the DCR decreases. Otherwise, the accumulative effect is obvious where the VE and the DCR decrease and increase respectively during multiple short circuits. The conclusion can provide references for the vibration-based condition monitoring of transformer windings.