Optical Observation of Streamer Branches in a 1 m Rod-Plate Air Gap under Positive Impulse Voltages

In this study, based on two CMOS cameras, an orthogonal optical observation platform has been set up for positive streamer branches under 1 m rod-plate air gap. The Monopodia branch and the Dichotomous branch have been proposed for steamer branch classification. The branch length, the branch angle and the optical diameter are statistical obtained and compared for the two branch types under different impulse voltages. The empirical function between the branch length Ls and the inception voltage Ui of the Monopodia branch has been obtained. The distributions of the branch angle and the axial angle of the two types have been given, and the mean optical diameters have been provided. Based on the comparisons, the formation mechanism of the two branch types has been proposed. This experimental result can provide the basic data to the numerical calculation of positive long air gap discharge.