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C4F7N/CO2 mixture has been widely studied as an environmental-friendly insulating gas expected to replace sulfur hexafluoride (SF6) in high-voltage equipment. In high-voltage power systems, the medium dielectric characteristics under switching impulse (SI) voltage are an important factor in insulation coordination. Nevertheless, few studies on this aspect of C4F7N/CO2 mixture have been reported. This article investigates the surface flashover of a cylindrical insulator in a C4F7N/CO2 mixture under switching voltage. The effects of molar fraction, gas pressure, creepage distance, and insulator materials on surface flashover voltage are studied in a uniform field. The result shows that the increase of flashover voltage indicates a saturation trend with the increase of C4F7N molar fraction and pressure, respectively. The dielectric strength of 13% C4F7N/87% CO2 relative to SF6 can reach at least 84%. The limiting factors of the flashover voltage increase under high pressure are preliminarily discussed. Additionally, the empirical formula on the critical flashover electrical field has been obtained, which can provide a reference for insulation design for environment-friendly gas insulation equipment. [ABSTRACT FROM AUTHOR]

By triggering the switches in sequence and controlling the brick charging voltage independently, a pulsed power system can generate flexible current waveform in the load, which could allow high-accurate magnetic pressure in experimental materials in the study of EOS data and dynamic response of material characterization. Currently, a 1.5-MA driver with 20 independent bricks has been developed, and a programmable 256-brick parallel discharge driver which is able to generate shaped current greater than 6.5 MA is under construction in the China Academy of Engineering Physics. In this paper, for these two multibrick parallel discharge drivers, the method of optimizing the output current waveform of the driver is studied by using the genetic algorithm and the corresponding optimization results of different target current waveforms are obtained. An experimental platform is set up for studying the gas switch breakdown characteristics. The self-breakdown and triggering breakdown experiments of the switch are conducted, and its breakdown characteristics are researched. Meanwhile, the effect of breakdown delay and jitter on the output current waveform is studied by simulation. This paper is of great significance to the actual operation of the multibrick parallel discharge drivers. [ABSTRACT FROM AUTHOR]

The capillary-based pulsed plasma thruster (PPT) has high-energy transfer efficiency, which provides potential to improve traditional PPT performance. In this paper, the discharge characteristics of a capillary-based PPT have been investigated. First, the typical process of voltage and current waveform is recognized. It is featured with a fast voltage drop (~25 ns) and a consequent damped sine wave oscillation discharge. Then based on the circuit analysis, the equivalent plasma resistance has been calculated. The current waveform is well fit with a linearly increasing resistance model. The influence of charging voltage has also been studied. The deposited energy increases while the transfer efficiency decreases with the increasing applied voltage. The cavity dimension has effects on the equivalent circuit parameters. The results show that longer cavity and smaller diameter lead to more deposited energy and higher transfer efficiency. The influence of voltage and capillary dimension on the mass shot characteristic has been discussed. Finally, the estimated impulse bit has been calculated and the impulse bit characteristics have been discussed. These results can contribute to the further optimization of PPT. [ABSTRACT FROM PUBLISHER]