The Effect Of Electrical Properties Of SF₆ Alternative Gas On Electrical Breakdown Strength

Insulating gas six sulfur hexafluoride（SF₆）with excellent insulating,arc-queand difficult to liquefaction in its nomal state,has been mostly widely used in power industry.However,SF₆ has been listed as one of the six greenhouse gases that must be limited due to its high global warming potential.Therefore,the problem for search the SF₆ replacement gas has been the most urgent problem at present.The electrical properties criterion of SF₆ replacement gas is proposed that can provide reliable information for futureexperimental investigations through the study at the atomic and molecular levels.Stationary point equilibrium geometries on the ground state in the OCCHCN isomerization reaction have been optimized by density functional theory（DFT）and 6-311+G（d,p）basis set,and the harmonic vibration frequencies are calculated at the same level.The HOMO-LUMO energy gaps（Eg）,ionization potentials（IP）,and electron affinities（EA）of the studied molecules are obtained.The minimum energy path（MEP）is obtained by the intrinsic reaction coordinate（IRC）theory,and the energetic information is further refined by QCISD（T）（single-point）method.The results show that OCCHCN can be used as SF₆ alternative insulation gas in high voltage equipment according to potential energy surface analysis.The stationary point equilibrium geometries of C5-PFK,C6-PFK,C2F₃ N,C3F5N and C₄F₇ N have been optimized,and calculated their IP,EA and Eg,which explained（CF₃）2CFCOCF₃ and C₄F₇ N can be used as a potential alternative to SF₆ gasat the atomic and molecular levels.All the possible decomposition channels and species of C₄F₇ N has been researched,and the structural optimizations and vibrational frequency calculations of reactant,intermediates,transitions states and productsin the decomposition process of C₄F₇ N by use of B3 LYP method with 6-311+G（d,p）basis set.Furthermore,the potential energy surface information were confirmed with MPWB1K/6-311+G（3df,2p）level.The results show that C₄F₇N→CF₃CFCN+CF₃ and CF₃ CFCN decomposition channels were dominant in all channels.C₄F₇ N → CF₃CFCF₃+CNand C₄F₇ N →（CF₃）2CCN+F decomposition channels were dominant in all channels.C₄F₇N→CF₃CFCF₃+CN and C₄F₇N→（CF₃）2CCN+F decomposition channels were minor.This paper is hopeful to provide theoretical basis for the insulating properties of C₄F₇ N.