Polarity Effect of Flowing Air Discharge

Gas discharge theory as an important subject has been widely employed to solve various questions related to discharge. However, previous concerns about gas discharge were mainly related to some discharge situations in static gases, which do not consider the influence of airflow on discharge. In this paper, the influence of both the airflow direction that is parallel to the field direction and the airflow velocity on air discharge is studied. The airflow is found to induce an obvious polarity effect, which results in a substantial difference in the breakdown voltage values. Compared with the breakdown voltage in static air, the breakdown voltage in airflow decreases because of the downwind effect and increases because of the headwind effect. The relative mean free path of electrons, the diffusion radius of electrons, and the air density are the three major factors affecting the discharge process, and they change with the airflow direction and airflow velocity. The combined effects of those three factors determine the variation trends in breakdown voltage with airflow velocity. These results can provide guidance for the design and insulation coordination of high-voltage equipment in an airflow environment.