Improving Detection Effectiveness of Latent Metal Particles in GIS by Applying Mechanical Impact in Power-Frequency Withstand-Voltage Test

Metal particles are. a great threat to GIS insulation, especially latent metal particles with higher densities, which are difficult to detect and provide early warnings before sudden faults. Thus, the detection of particles in predelivery or handover test stage is necessary and urgent. This paper proposed a new method by applying mechanical vibration to excite latent particles in power-frequency withstand-voltage test (PVT) to improve the detection effectiveness. In a scaled GIS, the charging and moving properties of latent particles under power-frequency voltage and impact vibration were investigated by experiment and simulation. Results showed that impact vibration could dramatically decrease particle lifting field by over 50% and trigger continuous bouncing under a lower electric field, releasing detectable acoustic signals. Validation tests were also conducted in a 330-kV GIS. In routine PVT, the critical detectable thickness of silver disc-type particles was ∼0.1 mm, while an 80 g--20 ms impact vibration could expand critical thickness to ∼0.4 mm, greatly enlarging the detectable parameter domain. Finally, the propagation and attenuation of impact vibration in different GIS components were studied, and the application method was discussed. The proposed new method affiliated to PVT could improve the detection effectiveness of latent particles and thus the insulation reliability of GIS