The evolution of discharge dynamics in N 2 -SF 6 mixtures under long-term repetitive submicrosecond pulses is investigated based on pulse-sequence resolved electrical and optical diagnostics. The effects of gas pressure, pulse repetition frequency (PRF), and SF 6 concentration on discharge evolutions are determined. The number of applied pulses before breakdown is shown to non-linearly decrease with increasing PRF for all included gas pressures and SF 6 concentrations. A higher SF 6 concentration is favourable for increasing relative insulation capability under repetitive pulses. Unexpected complexities of discharge evolutions under repetitive pulses are reported for the first time for the discharge mechanism transition when a strong electronegative gas is introduced. A pulseto-pulse progressive streamer (first discharge)-to-precursor (before breakdown) transition is observed in an N 2 -SF 6 mixture under positive repetitive pulses and is less dependent on gas pressure than traditional scenarios. The formation of a precursor section is jointly supported by electrical and optical signatures. The discharge mechanism transition and the detour phenomenon under repetitive pulses are discussed based on the effects of space charges on the spatial distribution of the electric field strength.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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