环氧复合绝缘表面微裂纹检测的超声临界折射纵波法

Ultrasonic LCR Method for Detecting Micro-cracks on the Surface of Epoxy Composite Insulation

气体绝缘金属封闭开关设备(gas-insulated metal-enclosed switchgear,GIS)盆式绝缘子表面微小裂纹在工作电压及运行环境下进一步发展,可引发局部放电或沿面闪络,威胁设备的安全运行。针对此,制备252 kV GIS盆式绝缘子相同材料和工艺的环氧复合材料试样,制作表面微裂纹,并搭建超声检测系统,进行取向、高度不同的裂纹超声临界折射纵波(critically refracted longitudinal waves,LCR)检测试验;提出单探头模式下以缺陷反射波来确定裂纹,双探头模式下以接收波幅值的变化来评估裂纹的检测方法。结果表明,用2.5 MHz超声可变角探头,单探头和双探头模式均可检测到高0.5~2.0 mm、取向不同的表面微裂纹,裂纹高度和波形幅值呈线性关系;与单探头模式相比,裂纹取向对双探头模式检测效果的影响较小。

Micro-cracks on the surface of basin insulators inside GIS could trigger partial discharges or surface flashovers under working voltages and operating environments,threatening safe operation of equipment.Therefore,epoxy composite specimens were made of similar materials and manufacturing processes for 252 kV GIS basin insulators,micro-cracks on the insulator surface were made artificially and an ultrasonic testing system with critically refracted longitudinal waves(LCR)was built for the ultrasonic test on micro-cracks with different orientations and depths.A method was proposed to evaluate a crack by the defect reflected wave using a single transducer and decreasing the amplitude of received waves using the double transducers.The results show that surface micro-cracks with a depth of 0.5~2.0 mm and different orientations could be detected using 2.5 MHz ultrasonic variable angle transducers under the modes of the single transducer and double transducers.The relationship between the heights of cracks and the amplitudes of waveforms is linear.Compared with the mode of the single transducer,crack orientations have less influence on the detection using the double transducers.