Effect of micro-H 2 O and micro-O 2 on the decomposition characteristics of insulating medium C 3 F 7 CN gas using molec
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ORIGINAL PAPER
Effect of micro-H2O and micro-O2 on the decomposition characteristics of insulating medium C3F7CN gas using molecular dynamics and transition state method Meng Xiao 1
&
Xiaoman Feng 1 & Xiayu Li 1 & Ruize Gao 1 & Boxue Du 1
Received: 10 June 2020 / Accepted: 26 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In recent years, heptafluoroisobutyronitrile (C3F7CN) has been proved to be a potential eco-friendly insulating medium to replace sulfur hexafluoride (SF6, the strong greenhouse gas). In this paper, the effect of micro-H2O and micro-O2 on the decomposition of C3F7CN was investigated based on the reactive force field molecular dynamics (ReaxFF-MD) and transition state theory (TST). It was found that H2O obviously promoted the decomposition of C3F7CN, and new products HF, COF2, CO, and NO were generated. The influence of O2 on the C3F7CN dissociation was weaker than that of H2O, and O2 slightly promoted the C3F7CN decomposition only when 50 O2 molecules were added. The simultaneous presence of H2O and O2 promoted the decomposition of C3F7CN, the promotion of which was closed to H2O existing alone. The calculation results showed that the energy barriers of the two reactions forming COF2 were 31.38 kcal/mol and 23.85 kcal/mol, respectively, which indicated that the reactions were difficult to proceed spontaneously. The energy barrier of F + H2O → HF + OH was relatively lower than that of COF2. These values corresponded well to the ReaxFF simulation results. This study provides theoretical support for the effect of H2O and O2 on the decomposition of C3F7CN. Keywords Micro-H2O and micro-O2 . Decomposition characteristics . C3F7CN gas . ReaxFF-MD . Transition state theory
Introduction Sulfur hexafluoride (SF6) has been widely used in gasinsulated equipment as a dielectric medium for its excellent insulation and arc extinguishing performance [1–5]. However, SF6 is a powerful greenhouse gas with a global warming potential (GWP) of 23,900 and an atmospheric lifetime of 3200 years [6–10]. It is necessary to control the use and emission of SF6 and develop an environmentally friendly insulating gas. In recent years, some eco-friendly insulating gases, such as C3F7CN and C5F10O, have been developed and attracted widespread attentions. These gases were confirmed to have great insulating properties and could be used in * Meng Xiao [email protected] * Boxue Du [email protected] 1
Key Laboratory of Smart Grid of Education Ministry, School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China
electrical equipment instead of SF6 in some practical application [5, 11–16]. During long-term operation of gas-insulated electrical equipment, discharge or overheating fault is inevitably generated in the equipment due to internal defects, which leads to the dissociation of the gas and the formation of various decomposition products [17]. Before large-scale application of new gases, their decomposition characteristics in special cases should be stu
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