Experimental study on the onset of positive corona in atmospheric air

This paper reports the findings of a study into the gas physical processes which lead to the inception of the positive corona discharge in atmospheric air. A multiple avalanche process is observed to be a basic feature, and correlation with the works reported in the literature suggests that at corona onset the physical phenomena are independent of electrode radius of curvature ρ in the range 0.04<ρ (mm) <250. The various models used to simulate the precorona discharge sequence and to predict corona-onset field-strength values are then examined. It is concluded that the development of a rigorous physical-mathematical model of corona onset must await a full understanding of the avalanche-to-corona transition mechanism. Prior to this, a simple empirical approach is adequate for the prediction of corona-onset field strengths.