Prediction of microparticle-initiated breakdown in mm-scaled air gap based on townsend theory and streamer inception

This paper addresses the prediction of microparticle-initiated breakdown in mm-scaled air gaps which has a transition Pd value of about 200 Pa.m. Predictions by Townsend theory and streamer inception are compared with experimental measurements and the results indicate that the Townsend theory is in better agreement. Based on this method, the breakdown voltage of an air gap with a single microparticle is calculated and drops quasi-linearly with its radius at a decay factor about 35 V/μm. The relative reduction rates of U b caused by single r m =10 and 100 μm microparticle reaches 3.1 and 37.3%, respectively. However once r m =10 μm microparticles cluster, the reduction rate rises to 7.2 and 35.5%. This provides a prediction method to assess the effects of microparticles on gas breakdown, especially in mm-scaled gap with transition Pd value and contributes to development of insulation performance.