Characteristics and Underlying Physics of Bipolar Corona Discharge of Floating Conductor

Bipolar corona discharge is the fundamental phenomenon that preoccurs in air breakdown for nongrounded objects facing a high-voltage source, which sets important bases for aircraft protection crossing thunderclouds and improvement of high-voltage switches with floating conductors, while this phenomenon has not been fully understood to date. This article proposes a bipolar corona plasma model (BCPM) based on the plasma hydrodynamic process and the chemical reactions of air discharge. The numerical analysis of the charged particle distribution matches the experimental result of the bipolar corona discharge appearance. Furthermore, the characteristics of bipolar corona discharge are described from the perspective of electric field and electron current density at the two opposite ends of the floating conductor. Results show that, at the positive end, the corona discharge has a long columnar shape in a faint light blue. While at the negative end, the corona presents a spherical shape in a stronger luminous light purple. There exists a density extremum at the position 0.03 cm away from the conductor ends in the distribution of electrons, where a low electron density zone with a concentration of 0.42
$\times \,\,10^{13}\,\,\text{m}^{-3}$
forms at the positive end, while electrons group to a high density of 2
$\times \,\,10^{16}\,\,\text{m}^{-3}$
at the negative end. The geometric length of the high-density ions zone is enlarged by 2 times at the positive end compared to the negative end. The peak electric field at the negative end is about 1.5 times stronger than the electric field at the positive end, consistent with the space charge distribution at the positive and negative ends. The unbalance of the emission and entry of electron current results in a slightly positive polarity for the floating conductor. This study can be consulted for shedding light on the underlying physics of bipolar corona discharge of floating conductors.