Leader Transition Properties of Propagating Partial Discharges in SF6 Gas and the Scaling Law under the Negative Lightning Impulse Voltage Application

This paper described leader transition properties of propagating partial discharges (PDs) in SF6 gas under the negative standard lightning voltage application with taking into consideration of effects of Trichel pulses and displacement current flowing between the PDs intermittently generated and around the wave front of the impulse voltage. Also, the scaling laws related to critical charge amount Qcr for the leader transition, leader step length ΔL and leader step time τLD were applied to the obtained results to discuss the applicability and difference in the polarity effect. As a result, the valuable negative PD's data to allow to apply the scaling las were obtained from this study. It was revealed that the distinctive displacement current, i.e. gradient of the wave front of the impulse voltage with relatively higher amplitude, and Trichel pulses during the negative polarity discharges can affect the leader transition, and change of the capacitance by propagating PDs also affects the leader transition as well as the scaling law with a parameter of dV/dt because the displacement current flowing thorough the discharge channel is influenced by the capacitance.