Positive Leader Velocity and Discharge Current Considering Leader Branching Under Different Air Pressures

Determined from leader velocity, leader channel length is an important parameter in gas discharge calculations which helps in studying the voltage drop from the electrode and the electric field distribution in the gap. For comprehensive air-gap discharge studies, a pressure-adjustable test platform including an artificial climate chamber and a Mach-Zehnder laser interferometer was used. Discharge current waveforms, interference images, and luminescence images at air pressures ranging from 0.3 to 2 atm were obtained. A discharge initiates several stems simultaneously and the leader channels form significant branches during the discharge. At lower pressures, fewer stems formed simultaneously in the early discharge, but there were more main leader channels before gap breakdown. The reverse occurred at higher pressures. From recorded data, which was verified using high-speed cameras, the total discharge current was found distributed over several leader channels. The relationship between leader velocity and current is analyzed considering the branching, and a power-law function between the positive leader velocity and current is found.