Streamer‐to‐precursor transition in N ₂ –SF ₆ mixtures under positive repetitive submicrosecond pulses

Abstract

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.

Positive and negative streamers in air and nitrogen in a sharply inhomogeneous electric field under conditions of runaway electron generation

“…The same streamers were observed in Refs. [12,18,19,22,25,26,38,44,46,[49][50][51][62][63][64][65][66]. It is seen that the streamer diameter can reach the order of the length of the interelectrode distance d. Figure 2c shows that the streamer front moves in the direction of the grounded electrode at different velocities as in our previous studies [51,67].…”

“…The same streamers were observed in Refs. [12, 18, 19, 22, 25, 26, 38, 44, 46, 49–51, 62–66]. It is seen that the streamer diameter can reach the order of the length of the interelectrode distance d .…”

Periodical discharge regime transitions under long-term repetitive nanosecond pulses

“…However, many experimental and simulation results have demonstrated that the NRP discharge regime is not consistent although voltage waveforms in a pulse train are fixed [10,[19][20][21][22][23]. One representative example is the 'corona-to-spark' transition under repetitive pulses concerned by the high-voltage insulation design [19,24]. Complicated discharge regime transitions undermine the consistency of plasma parameters and cause discharge control complexities.…”

Evolutions of repetitively pulsed positive streamer discharge in electronegative gas mixtures at high pressure

“…Effects of oxygen addition on production of reactive species have been extensively discussed. However, evolutions of streamer developments (e.g., primary and secondary streamers [34,35]) under long-term repetitive pulses in electronegative gas mixtures at high pressure have not been thoroughly elucidated.…”