Negative corona in air at atmospheric pressure due to a voltage impulse

摘要

This article presents a numerical modeling of a negative corona caused by an overvoltage pulse (～250), in a point-to-plane electrode system. The field value applied to the cathode is high, thus, the numerical simulation described in this article attempts to show that the field-effect emission can be responsible for the ignition of the corona and for its first stage of development, while the positive-ion bombardment is responsible for sustaining the discharge during the current decay phase. A time-dependent enhancement factor is introduced in the classical Fowler-Nordheim relationship in order to model the switch on of some emissive site at the cathode surface. Preliminary experiments were carried out in order to better understand the ignition and development of the corona. The role of the field-effect emission is underlined and the dimension of the corona is optically determined. The negative corona current pulse and its associated emitted UV light are computed and compared to experimental results.