The Intrinsic Streamer Branching in Insulating Oils: Discharge Properties and Dynamic Balance at the Streamer Head During Early Propagation

In this paper, the intrinsic branching properties of streamers in natural ester and naphthenic crude oil are investigated in terms of the variability of electric field distorted by space charge at streamer head. In the microsecond-scale electrohydrodynamic streamer simulation of these two oils, by extracting and comparing the propagation parameters at the streamer head in the first branching position of these two oils, streamers in natural ester were found to have more active discharge characteristics and lower resistance to initiation and propagation compared to naphthenic crude oil. Further, theoretically, there is a threshold point in the evolution of the streamer through which streamer undergoes a certain degree of morphology change, and localized maximum space charge density and electric field intensity appear at neck of the streamer in natural ester, which consequently lead to branching of streamers in the initial phase. Research findings in this paper prove that, without considering additional space ionization mutation factors, the differences in the discharge properties at streamers head, i.e., space charge and electric field intensity, are dominant factors for the initiation and development of intrinsic streamer branches.