Study On The Breakdown Characteristics Of Commonly Used Dielectrics In The Closing Switch Of Mesoband Device

Our laboratory is undertaking a research project about a kind of mesoband device based on switch oscillator currently. Previous studies showed that performance of the closing switch determines the radiation power and energy efficiency of the broad band device. The closing switch is a kind of self-breakdown spark gap switch which is designed with a uniform field and works under the condition of rapid charging, in nanoseconds the voltage of which can be up to several hundred kilovolts. At present, the theory of dielectric breakdown under high voltage nanosecond pulse is still in the stage of exploration, and the experimental data isn't sufficient. In order to provide preference to the optimal design of closure switch and promote further improvement to the field of nanosecond pulses dielectric breakdown both in experimental data and theoretical research, this paper carries out the experimental study of the breakdown characteristics of transformer oil?SF6 and N2 under high voltage nanosecond pulse. The main work of this article include the following aspects:1?We designed an experimental apparatus for nanosecond pulse dielectric breakdown experiments. At first we analyzed the main features of the closure switch, and designed a kind of breakdown experimental components with a structure of uniform field and a kind of high voltage pulse driving source, which is based on the idea of storage capacitor fast charging capacitive load through the inductor; then we analyzed the influence of the component parameters(the storage capacitor Cm, wiring inductance Lr and workload CL) to the experimental apparatus; at last we carried out preliminary experiment tests, and the result showed that the experimental apparatus can successfully produce a charge pulse with 10 ns rise time and 200 k V amplitude voltage in the input of the switch chamber, which improves that this experimental apparatus was capable of carries out the experimental study of the breakdown characteristics under high voltage nanosecond pulse.2?We designed measuring system for the measurement of high-frequency experimental signals. In order to accurately detect the voltage signal at the input and output of switch chamber during the breakdown process, we designed a capacitive divider with coaxial structure and measurement circuit, and analyzes the impact of signal frequency and compensation resistor on the working performance of the measurement system, then we tested the working performance of the measurement system by the calibration experiment, proving that this measuring system can accurately measure high frequency test signal.3?With the experimental apparatus and measurement systems introduced above, we carried out the experimental study of breakdown characteristics under nanosecond pulses of transformer oil, SF6 and N2. At first we carried the nanosecond pulsed breakdown experiment of the transformer oil, and summed up a curve fit according to the results of transformer oil with the rise time of 4~10ns, at the same time we analyzed the influence of the circulation device?hydrostatic pressure and the rise time of the pulse(10 ns?15 ns) on the breakdown characteristic of transformer oil; then we carried out the experimental study of breakdown characteristics under nanosecond pulses of SF6(1~18 atm) and N2(1~40 atm),then we summarized an empirical formula both applicable for SF6 and N2 with the rise time of 4~14 ns according to the experiment results.