Effects of the grid geometry on the performances of a triode-type corona electrode system

Abstract

The triode-type electrode system is frequently employed for accurately controlling the corona charging of insulating materials. The primarily aim of this paper is to characterize the effects of grid geometry of the triode-type corona electrode system by current-voltage and current density distribution measurements. The ionizing element of the electrode system is a thin Tungsten wire (diameter: 200 μm) attached to a cylinder (diameter: 26 mm) and distanced at 34 mm from its axis. The wire-cylinder assembly is a “dual” electrode, facing a grid electrode, connected to a well-defined potential, and a grounded plate electrode. The geometry of the grid has a very significant influence on the current-voltage characteristics of the triode system, on the corona onset voltage value and on the repartition of the current density. The experimental results obtained for different geometries of the grid electrode system are interpreted in order to make some recommendations regarding its design.