Experimental Study On The Post-Arc Self-Reduction Characteristics And Decomposition Products Of SF₆/N₂ Mixed Gas

Pure SF₆ has super ability to extinguish arcs in gas-insulated equipment,and has excellent insulation performance,and is used in large-scale power equipment.In recent years,some of the shortcomings exposed by SF₆,especially the greenhouse effect,have reached intolerable Therefore,reducing the use of SF₆ in electrical equipment has been put on the agenda.At present,SF₆/N₂ mixed gas has been gradually promoted to replace pure SF₆ in the power industry,and SF₆/N₂ mixed gas discharge decomposition products detection tests have been carried out to explore SF₆/N₂ The self-reduction characteristics of mixed gas are of great significance to the evaluation of the operation status of electrical equipment.In order to deeply understand the law of SF₆/N₂ mixed gas arc discharge decomposition products,this paper mainly explores the following aspects.（1）Design of arc test circuit.In this paper,the LC oscillating circuit is used as the arc discharge test power source,the test tank is used as the test sample,and the arc interruption test is completed with the pneumatic operating mechanism.Select the amount of capacitance and inductance according to the test plan,as well as the selection of contact processing and measuring devices.A gas chromatograph with a built-in SF₆ special chromatographic column was selected as the decomposition product detection system for the detection of decomposition products.（2）Arc test and detection of decomposition products.In this paper,pure SF₆,30%SF₆/70%N₂,40%SF₆/60%N₂ mixed gas is used as the research object,and arc tests under different breaking currents and different breaking times are carried out.The breaking current was measured,and the arc single discharge energy was calculated.After the test was completed,the decomposition products were detected by gas chromatograph,and the variation rules of the types and contents of the decomposition products under different arc breaking currents and different breaking times were explored.（3）Simulation calculation and rule summary.In this paper,firstly,according to the four laws that SF₆/N₂ plasma follows at high temperature,the equations are written,and the equations are solved.Post self-reduction characteristics and decomposition process,calculate the reaction heat of the possible decomposition paths of SF₆/N₂ mixed gas in the case of arc discharge,explore the endothermic and exothermic conditions of these reactions,and analyze the difficulty and difficulty of forming the main decomposition products.Then,the relevant ionization parameters of the gas components after the decomposition of the SF₆/N₂ mixed gas are calculated by using density functional theory,and the properties of the products after the decomposition of the SF₆/N₂ mixed gas are studied according to the calculated molecular parameters.The test results show that the main components of the SF₆/N₂ mixed gas decomposed under arc discharge are CF4,CH4,CO2,C2F6,SO2F2,SOF2,SO2,NF3 and N₂ O.Next,the production of CF4 and C2F6 was the lowest.And the larger the proportion of N₂ in the mixed gas,the higher the generation of NF3 and N₂ O after the arc discharge,and the lower the generation of the remaining components.In the actual working condition,the larger proportion of N₂ can be selected under the premise of ensuring the insulation performance.The simulation calculation results show that after the discharge decomposition,SF₆/N₂ first undergoes a primary reaction to generate low-fluorine sulfides,and then further reacts to generate various decomposition components.The calculation results of the ionization parameters of the decomposition components show that the decomposition products of SF₆/N₂ after discharge The ionization energy is lower than that of SF₆,and the insulation performance is reduced.In addition,the two components of NF3 and N₂ O are stable and non-toxic,and can be used as the characteristic components of the decomposition products of SF₆/N₂ mixed gas.