The behaviour of DC corona discharge in air that is free of particulate matter with the wires-to-plane geometry was analysed in this work. The formulae I = KV (V − V0) and I = A (V − V0)m commonly used for the current-voltage characteristics were used to determine the various corona parameters for the two polarities of the corona discharge. Using curve fitting, it has been shown that the geometric factors K and A and the exponent m are strongly affected by the number n of the discharging wires. However, the corona inception voltage determined from the measurements is weakly influenced when n is small, and it remained constant for n > 5 discharging wires. As for the breakdown voltage of the discharge, it is practically independent of the number n. Furthermore, it was verified that the two formulae above can be used for both negative and positive corona in multiple wires-to-plane geometries.

This paper aims to analyze the behavior of DC bipolar corona discharge in a two wires-to-plane configuration under variable humid air conditions. A circular biased probe was adapted to the plane and used to measure the ground-plane current density and electric field during the bipolar corona. The values of the electric field and the current density at the plane surface were the maximum beneath the two corona wires which decreased when moving away from them. The current-voltage characteristics followed the quadratic Townsend’s law. The experimental results show that the bipolar corona discharge is strongly affected by the air humidity. The current density and the electric field decrease linearly with the humidity for all the tested wire diameters.