Experimental and Numerical Characterization of Corona Discharge Generated by a Triode Electrode System

The triode electrode system is frequently employed for accurately controlling the corona charging of insulating materials. The primarily aim of this paper is to characterize this electrode system by current-voltage and current density distribution measurements. The electrostatic aspect of the electric field generated by the triode electrode system is also numerically analyzed using a charge simulation program. 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 grounded plate electrode (aluminum, 250 mm × 130 mm). The interelectrode spacing has a very significant influence on the current-voltage characteristics of the triode system and on the extension of the corona discharge generated by it. The experimental results obtained for different geometries of the electrode system are interpreted in the light of the numerical modeling of the electric field, in order to make some recommendations regarding its design: reduce/increase the wire-grid distance in order to diminish the operating high voltage/expend the surface affected by the corona discharge.