Dimensional Analysis of Corona Discharges: the Small Current Regime for Rod-Plane Geometry in Air

The technique of dimensional analysis is applied to a general corona discharge between two electrodes of arbitrary shape. This theory is then simplified to apply to rod-plane geometry for currents near inception. A series of experiments with hemispherically tipped rods has been carried out in ambient air. The variations with geometry of the inception voltage and of the slope of the current-voltage curve at inception have been recorded with considerable care. Analysis of the results confirmed known relationships, but also revealed previously unsuspected geometric dependencies. These are discussed in terms of the known behaviour of glow discharges. The dimensional methods have led to the formulation of a new current-voltage law appropriate to the inception regime for small point