Environment-friendly Insulating Medium HFO-1234ze(E) Mixed Gas Insulation Performance And The Study Of Decomposition Characteristics

At present,SF₆is widely used in gas insulation equipment due to its good insulation properties and excellent arc extinguishing performance.But it is undeniable that SF₆is also a very harmful greenhouse gas.With the improvement of people’s environmental awareness.All sectors of society began to call for the reduction and restriction of the use of the gas.At the same time,studies have shown that the decomposition products of SF₆under the action of various factors are toxic.This poses a serious threat to the lives of electric workers.Therefore,finding a new type of insulating medium that is environmentally friendly and safe for people has become the task and mission of workers in the electric power field.In recent years,HFO-1234ze（E）gas has attracted great attention due to its non-flammable,explosive,mass-produced,non-toxic,small greenhouse effect,and high dielectric strength.It’s considered to have the potential to be used in medium and low voltage insulation equipment.However,there are relatively few studies on the insulation properties and decomposition properties of HFO-1234ze（E）gas.This article explores the insulating properties of HFO-1234ze（E）/CO₂mixed gas from an experimental level.First,the saturated vapor pressure curve of HFO-1234ze（E）/CO₂mixed gas under different pressures was calculated and the experimental plan was determined.Then,using the gas insulation comprehensive performance test platform,the breakdown voltage of the HFO-1234ze（E）/CO₂mixed gas under different pressure,mixing ratio and electric field unevenness was measured,The optimal mixing ratio and pressure value of HFO-1234ze（E）/CO₂mixed gas used as a potential substitute for SF₆in engineering practice are discussed.The research results show that the maximum pressure of HFO-1234ze（E）without liquefaction at-15℃is120k Pa.Under different uniform field conditions.The insulation performance of HFO-1234ze（E）/CO₂mixed gas is improved with the increase of the mixing ratio,the breakdown voltage increases approximately linearly;Under the condition that the mixing ratio remains unchanged.Increasing the air pressure can significantly improve the insulation performance of HFO-1234ze（E）/CO₂mixed gas;The breakdown voltage of HFO-1234ze（E）/CO₂mixed gas performs best under quasi-uniform field conditions.At the same time under the condition of 0.3MPa,HFO-1234ze（E）with a content of20%-25%not only has a good insulation level,and it is relatively less affected by the unevenness of the electric field.In this paper,based on the density functional theory,the decomposition characteristics of HFO-1234ze（E）/CO₂mixed gas are studied from the simulation level and combined with experiments.First,by establishing a molecular simulation model,the basic properties of HFO-1234ze（E）are calculated,the bond breaking and bonding laws of gas molecules are obtained,and the reaction direction and mechanism of HFO-1234ze（E）/CO₂mixed gas are calculated.Then the self-recoverable insulation properties of HFO-1234ze（E）/CO₂mixed gas were discussed through experiments,and finally,gas chromatography mass spectrometry（GC/MS）was used to analyze the discharge decomposition components.Studies have found that the primary dissociation pathways of HFO-1234ze（E）molecules are mainly C=C double bonds,C-H and C-F single bonds;And it is found that there are more paths to produce free radical F,and the corresponding enthalpy change is lower,which is dominant in the decomposition process;The decomposition products are mainly hydrofluorocarbons（HFC）and hydrocarbons（HC）.Analysis of the frequency characteristics of the decomposition products found that the decomposition products are relatively stable;HFO-1234ze（E）/CO₂mixed gas has good self-healing insulation characteristics,and the final decomposition products all have high ionization energy and most of the products are not harmful to the environment.This paper explores the insulation and decomposition characteristics of HFO-1234ze（E）/CO₂mixed gas in two aspects:experiments and simulation calculations.The corresponding research results will provide theoretical and technical guidance for the application of new gases in medium and low voltage insulation equipment.