Flashover characteristics and mechanisms of insulation surface under flowing air conditions

The surface flashover problems along the gas-solid interface of solid insulation materials are a crucial issue affecting the insulation performance of high-voltage power equipment, especially in outdoor insulation systems, where flashover failures caused by flowing air pose a serious threat the stability and reliability of the power system. In this paper, a surface discharge testing system for epoxy resin insulating dielectrics in an airflow condition was established. The effects of different airflow velocities on the surface flashover voltage, discharge morphology, and flashover path of insulating dielectrics were studied, and the underlying physical mechanisms were revealed. The results demonstrate that the surface flashover characteristics of insulating dielectrics in flowing air conditions differ markedly from those in static air conditions. Specifically, the flashover voltage shows a notable decreasing trend with increasing airflow velocity. Additionally, under flowing air conditions, the flashover path is closely confined to the surface of the circular groove of the insulating dielectrics, as opposed to a non-surface path along the shortest distance between the electrodes in static air. The discharge pattern transitions from a dispersed columnar discharge in static air to a stable filamentous discharge under flowing air conditions. Further analysis reveals that the electrons and ions blowing away effect, surface charges dissipation effect, and the gas density effect are considered as the three dominant factors attributing to the change in surface flashover characteristics in flowing air conditions. When the airflow velocity is low, the gas density effect dominates, causing a decrease in flashover voltage. As the airflow velocity further increases, the electrons and ions blowing effect and surface charges dissipation effect become the dominate factors, resulting in an increase in flashover voltage. The findings in this study may contribute to a further understanding mechanism of insulation failure at the gas-solid interface of outdoor high-voltage insulation equipment in a flowing air condition, and it provides a reference for fault diagnosis.