An investigation of spark breakdown paths in air using an image processing technique

A video camera has been used to record the path of spark breakdowns across a negative point/plane air-gap. By using a prism as a mirror two images were obtained from which the path could be determined in three dimensions by subsequent computer processing and analysis. About 100 images were analysed for each of five angular positions of the point electrode´s axis, the gap remaining constant. The paths were analysed into a series of straight-line segments as a means of describing and investigating spark breakdown paths statistically. It was found that the first and last segments were significantly longer but varying with electrode-axis angle in the case of the first. The intermediate segments varied according to a Poissonian distribution. The results are consistent with a stepped development from the point electrode in a semi-random manner approximately following the field direction