Simulation of Initial Streamer Discharge in Mineral Transformer Oil Considering Multiple Ionized Molecular Clusters

A simulation model of needle-plate electrode discharge in mineral transformer oil is established on COMSOL finite element simulation software. In order to investigate the influence of multi/single ionized molecular clusters on streamer discharge in oil, numerical calculations were conducted for the charged particles in the discharge model, considering different ionized molecular clusters, voltage peaks, and voltage rise times. The electric field distribution along the
$z$
-axis and branching direction, as well as the distribution characteristics of the charged particles, were analyzed. The simulation results indicate that under different ionized molecular cluster conditions, streamer branching forms near the needle electrode. When considering multiple ionized molecular clusters, the morphology of the streamer is determined by the low ionization potential molecular clusters, while high ionization potential molecular clusters affect the electric field strength inside the streamer channel. The development of the streamer exhibits a staged propagation, which is more significant when considering only high ionization potential molecular clusters. Higher voltage peak will cause the streamer to propagate farther and form secondary streamer more easily. Faster voltage rise times facilitate the formation and propagation of the streamer, and the thickness of the streamer head is positively correlated with the voltage rise time. This study contributes further understanding of the mechanisms behind streamer discharge in liquid dielectrics, with mineral transformer oil serving as a representative medium.