Characteristics and Mechanisms of Rod-Rod Electrode Gap Breakdown Induced by High-temperature and Clean Flame

In order to investigate influence of high-temperature and intense flames derived from real wildfires on air gap breakdown properties around high voltage transmission lines, a rod-rod electrode breakdown-discharge test system under clean flame conditions was developed. After igniting ethanol, the gap between two copper rod electrodes was adjusted from 3.0 to 8.0 cm above and into the bulk flame, and dynamic charge load (from 0 to 50 kV) was applied externally to electrodes at each gap distance until there occurred breakdown across air gap. Evolution waveform and data of leaked current and instantaneous breakdown were recorded during the breakdown and discharge processes. Results show that under condition of high-temperature flame (750.0 °C~850.0 °C), breakdown voltages decrease by 55.7 %~68.3 % and 78.6 %~82.9 % when the flame is not bridged and bridged between two electrodes compared with those in pure air atmosphere. Under the action of a certain portion of flame plasma, insulating strength of rod-rod gap decreases significantly compared with that of pure air, which indicates that the high-temperature flame has a great influence on the formation and development of streamer, and is easier to form discharge channels.