基于微波反射法的复合绝缘子无损检测方法

Microwave-based Non-destructive Testing Method on Composite Insulators

为了对运行复合绝缘子内部缺陷进行无损探伤(NDT),提出一种基于高频微波的检测方法,利用微波在硅橡胶与缺陷以及缺陷与芯棒交界面处的折反射进行缺陷检测。首先通过计算不同缺陷类型处的折反射信号幅值,从理论上验证该方法可行性;其次,搭建了针对复合绝缘子的微波检测平台,并对加入不同类型人造缺陷的绝缘子样品上进行试验,优化各系统参数;最后对收集到的现场出现异常温升的绝缘子进行检测,找出缺陷位置,并解剖进行验证。实验结果表明:采用近场微波方法无需偶联剂,即可对复合绝缘子进行无接触、无损检测;可以检测到绝缘子内部的不同类型(介电常数)的缺陷;可识别尺寸小于0.4 mm的细微缺陷。通过实验验证了微波反射法应用于复合绝缘子内部缺陷检测的可行性。

In order to realize the non-destructive testing（NDT） of the internal defects in composite insulators, we presented a microwave detection system, which is based on microwave＇s refraction and reflection features on interfaces between silicone rubber and defects or between core rod and defects. Firstly, by calculating the magnitude of refraction and reflection signals according to different types of defects, we theoretically verified the method＇s feasibility. Secondly, a microwave detection platform for composite insulators was built up and used to test insulator samples with different artificial defects, and consequently various parameters of the system were optimized. Finally, we tested an insulator with unusual temperature rise collected from operation site. The defect position was located and then confirmed through anatomizing the insulator. The results show that the near-field microwave method needs no coupling agent to accomplish non-contact, non-destructive testing of composite insulators, and it can figure out different types of inner defects（with different dielectric constants）, and identify subtle defects of less than 0.4 mm in size. In conclusion, the feasibility of applying microwave reflection method to detect internal defects in composite insulators was verified by the experiments.