To ascertain the flashover mechanism of external insulations on train roof in a high-speed airflow environment

we investigated the breakdown characteristics and mechanism of short needle-plate air gaps in high-speed airflow based on an artificial experimental wind-tunnel platform. We obtained the breakdown characteristics regularity of the air gaps in wind sand environment by studying the influences of sand mass concentration

wind speed

gap distance and sand diameter on the breakdown voltage. It is found that the breakdown voltage of air gaps decreases with the increase of the sand mass concentration

and increases with the increase of the gap distance. When the wind speed increases

the breakdown voltages in weather of wind dust and wind both appear to be a curve which increases at first and then decreases

and the breakdown voltage in weather of wind dust is lower than the other. The breakdown voltage decreases first and then increases with the increase of the sand mass concentration

and there is a minimal value. Research results can provide a theoretical basis for protection of roof external insulation in a high-speed airflow environment.