Discharge Characteristics of Short Air Gap and Insulation Surface Under Flame Conditions

An experimental study was conducted to investigate the discharge characteristics of short air gap and insulation surface under flame conditions. The influence of ac electric field on flame and the mechanism leading to the reduction of breakdown voltage under flame conditions are analyzed. Results show that under the ac electric field, the flame is deflected to the high voltage electrode, and compared with normal conditions (without flame), the breakdown voltage of the short air gap and the insulation surface is decreased by 74.4% and 70%, respectively. Besides, arc levitation appears at high probability under the flame conditions. Furthermore, the decrease of the breakdown voltage of short air gap and the flashover voltage of insulation surface under the flame conditions are mainly due to the increase of the air conductivity and the decrease of the air density. For the insulating dielectric, the change of the flashover path is also one of the main reasons for the decrease of the flashover voltage.