Acoustic Emission and Propagation Characteristics of Metal Particles in GIS

Metal particle pollution was one of the significant factors that endangered the reliability of the gas-insulated switchgears (GISs). The detection of metal particles in GIS was crucial for ensuring the safe operation of GIS. This article established a calculation model for the cut-off frequency of acoustic emission (AE) generated by the metal particle collision with the GIS enclosure. The effects of metal particle materials, the Gaussian equivalent radius, and the bounce heights on the cut-off frequency of the AE signal were obtained. Through the AE measurement experiments of metal particle colliding with an aluminum plate, the accuracy of the cut-off frequency calculation model was verified. Besides, the experiment confirmed that the propagation mode of the AE signal on GIS enclosure was primarily the S0 mode Lamb wave. The attenuation of the AE signal was analyzed. The geometric attenuation and the energy loss attenuation were determined as the primary attenuation processes. A calculation model for the attenuation of AE signal was established. Based on this, the variation of the cut-off frequency after propagation on the GIS enclosure was clarified. The AE and propagation characteristic proposed in this article provided guidance for optimizing the frequency band of ultrasonic sensors and setting up the measurement points.