| Gas dielectrics are widely used in the field of electrical insulation,especially sulfur hexafluoride?SF6?,but the degradation of SF6 is very slow,which will seriously aggravate the atmospheric greenhouse effect.Some scholars try to replace SF6 with perfluorocarbons,but there are still many problems,such as:octafluorocyclobutane?c-C4F8?gas is easy to liquefy and decompose carbon;CF3I liquefaction temperature is too high and the price is expensive.None of these gases can completely replace SF6.Recently,the characteristics of nitrogen?N2?environmental protection have been widely favored.Therefore,it is of certain academic value to study the discharge characteristics of nitrogen.The molecular structure and orbital energy distribution of nitrogen are discussed in detail.There are six orbitals in nitrogen molecule:2?g?2?u?1?u?3?g?1?g?3?u.Their corresponding energy levels are:-35.92eV,-18.78eV,-16.73eV,-15.59eV,7.42eV and 30eV respectively.In this thesis,an experimental method for studying nitrogen discharge by acquiring spectra is proposed.The calculation methods and results of particle temperature and concentration in the process of nitrogen discharge by spectral information are given.Based on the basic principle of gas discharge and hydrodynamic model,numerical analysis of nitrogen discharge in typical rod-plate electrode structure is carried out.The time evolution and axial spatial distribution of electron temperature,space potential,positive ion concentration,electron concentration and electric field are obtained.The average electric field of streamer is 106V/m,and the electron density of streamer head is in the range of 1019-1020m-3.The velocity varies between105-106m/s,the radius of the streamer channel is about 10-3-10-5m,the electron temperature in the streamer channel is about 2.7eV,and the electron temperature in the streamer head is about 6.3eV,which is in accordance with the research results of relevant scholars.On the basis of deeply exploring the mechanism of nitrogen discharge,an experimental device for nitrogen discharge was designed and constructed.The discharge spectra of rod-plate electrode and tip-tip electrode at different spacing and voltage were collected by ICCD,and the spectral information was read by computer connected with ICCD.The formation and development of electron avalanches,the formation and development of streamers and breakdown phenomena are intuitively obtained.According to the experimental results of 10mm rod-plate electrode spacing,the calculated electron temperature is 2.7eV,and the electron concentration is 2.66×1020m-3,which is in agreement with the numerical results.This thesis provides an effective experimental method and reliable theoretical basis for the application of nitrogen in the field of high voltage insulation. |
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