Time-resolved measurements on thermal parameters of leader discharges using a Mach-Zehnder interferometer

Leader discharge is a main phase of long gap breakdown, characterized by high gas temperature (generally accepted to be above 1500 K). To evaluate the thermal parameters of leader channel, a Mach-Zehnder interferometer was established in our previous work. The diameter, radial distribution of gas density and gas temperature of leader channels can be derived from the interference fringe images. However, only one fringe image was obtained every impulse discharge before. In this paper, improved time-resolved interferometry was applied to the investigation of positive leader discharge produced by IEC standard switching impulse voltages. Thermal expansion process of leader channel was observed and quantitatively studied. Resolving of fringe patterns shows that the typical value of leader…