复合绝缘子脱粘缺陷的超声导波检测

为了实现复合绝缘子脱粘缺陷的快速无损检测,提出了利用超声导波衰减系数分段检测复合绝缘子的方法。根据超声导波的传播理论,建立了双层复合绝缘子的简化模型,据此绘制出导波在复合绝缘子中纵向和扭转模态的频散曲线。依托理论分析,进行了复合绝缘子脱粘检测的实验,实验结果表明:由于导波在硅橡胶中传播时衰减过大,对于电压等级高、长度较长的复合绝缘子,只能进行分段检测;当检测范围内有脱粘时,导波在复合绝缘子中传播时的衰减系数会减小,并且脱粘大小会影响衰减系数,因此可以通过检测导波传播的衰减系数,来判断是否有脱粘缺陷并判断缺陷大小;L模态导波的衰减系数可以判断检测区域内是否有脱粘缺陷以及周向脱粘大小,但无法估计轴向脱粘大小,T模态导波可以用来判断是否有轴向和周向脱粘缺陷并估计其缺陷的大小。

Inspection of Debonding Defects of Composite Insulators by Ultrasonic Guide Wave

In order to inspect debonding defects of composite insulator accurately and non-destructively, we proposed a new method for segmented detection that is based on the attenuation coefficient of ultrasonic guide waves. According to the theory of ultrasonic guide wave propagation, a simplified model of bilayer composite insulator was constructed, and the dispersion curves of longitudinal(L) and torsional(T) guided wave modes were plotted. On the basis of the theoretical analysis, experiments of detecting debonding of composite insulator were carried out. The experimental results showed that, as the guide waves attenuated excessively during propagation in the silicone rubber, a segmented detection method would be adopted for a long composite insulator of high voltage level;the attenuation coefficient of guide waves would decrease, when there was debonding within the detection range;the size of debonding would influence the attenuation coefficient, so we could determine whether there was debonding defects as well as the size of defects by inspecting the attenuation coefficient of guided waves;the attenuation coefficient of longitudinal mode could be used to determine whether there was debonding defects and estimate the size of circumferential debonding, but could not estimate the size of axial debonding;we could determine whether there was axial and circumferential debonding defects as well as the size of defects by the attenuation coefficient of torsional mode.