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

Nonlinear Vibration Model of Transformer Windings and Their Vibration Characteristics During Multiple Short Circuits

变压器绕组在外部短路过程中承受巨大电动力,会产生强烈的非线性振动响应,其振动信号中存在大量谐波。为进一步研究多次短路冲击下绕组振动特征的变化规律,首先建立了计及纸板力学非线性的绕组动力学模型,研究了累积效应作用下纸板厚度的收缩规律;然后提出表征振动特征的振动熵、主频能量比和谐波有效值,分析了上述特征值随电流幅值、绕组固有频率和累积效应的变化规律;最后对1台220 kV退运变压器进行了多次突发短路试验。结果表明:绝缘纸板非线性力学特性导致振动信号中产生了高于100 Hz的50 Hz倍频谐波分量;短路电流较小时,谐波有效值和振动熵随短路电流增大而增大,主频能量比减小;短路电流较大时,绝缘材料累积效应显著,随短路次数的增多,振动熵减小,主频能量比分增大。所得结论可为基于振动信号的绕组机械状态评估提供参考。

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.