"Multi-Particle-in-Series" Phenomenon and Discharge Properties Induced by Multiple Free Particles in GIS

Free conductive particle is one of the main insulation threats to GIS. However, due to the extremely strong variety and randomness of particle behaviors, it is difficult to reproduce the particle-induced-breakdown in GIS, and the breakdown mechanism with multiple-micro-particle coexisting, are unclear and need further investigations. In this research, the movement pattern of multiple particles in a 1100 kV GIS was firstly analyzed, and found that the slight axial electric field could drive particles to move towards the convex side of the basin insulator, eventually causing an accumulation in a region. "Multi-particle-in-series" (MPIS) phenomenon was observed, with a low probability, but inevitably in the long run. Secondly, the physical model of multiple-particle-induced breakdown was established based on the streamer criteria, and a step-by-step discharge during MPIS process was responsible for the breakdown. Lastly, a 252 kV GIS was employed to act as a scaled model to equivalently simulate the electric field in 1100 kV GIS and experimentally study the particle-induced breakdown properties. A single particle in each state and position was difficult to induce the breakdown, while MPIS triggered several breakdowns, although at a very low working coefficient, which eventually verified the breakdown mechanism induced by MPIS in GIS.