基于热刺激电流的大电机VPI主绝缘电老化特性

Electrical Aging Characteristics of VPI Main Insulation of Large Generator Based on Thermally Stimulated Current

为了研究大型发电机定子线棒主绝缘在不同电老化阶段的老化机理,利用热刺激电流(thermally stimulated current,TSC)法对少胶真空压力浸渍(vacuum pressure impregnating,VPI)定子线棒绝缘进行研究。主要分析了VPI绝缘TSC峰的形成机理,计算了不同TSC峰的特征参数,利用傅里叶红外光谱(Fourier transform infrared spectroscopy,FTIR)分析了绝缘材料含有的胶黏剂的基团变化,利用扫描电镜(scanning electron microscopa,SEM)观测了微观状态下材料形貌变化。试验结果表明:在所测–40~120℃区间内,VPI绝缘TSC谱为1条由转向极化和界面极化引起的双峰曲线,峰值温度分别在–5℃和70℃附近。随着电老化时间的增加,转向极化峰活化能略有下降,界面极化峰活化能明显上升,各峰曲线幅值及释放电荷量均有不同程度的增加。因此该研究结果为利用TSC法分析定子线棒主绝缘老化机理奠定了基础。

In order to study the electrical aging characteristics of main insulation of large generator stator bar, the thermally stimulated current(TSC) was used to research the main insulation properties of vacuum pressure impregnating(VPI), the formation mechanism of TSC peak was analyzed, and the characteristic parameters of the TSC peak were calculated. Fourier transform infrared spectroscopy(FTIR) was used to analyze the group changes of the adhesive contained in the insulating material, and scanning electron microscopy(SEM) was used to observe the changes in material morphology in the microscopic state. The test results show that the TSC spectrum of VPI main insulation is a double-peak curve caused by turning polarization and interface polarization in measured range of -40~120 ℃, and the peak temperatures are at around -5 ℃ and 70 ℃. With the increase of electrical aging time, the activation energy of turning polarization peak decreases slightly, the interface polarization peak increases obviously, and the amplitude and release charge of each peak curve increase to different degrees. The results of this study lay the foundation for analyzing the aging mechanism of the main insulation of stator bar by using the TSC method.