| The SF6 circuit breaker is the key equipment to guarantee the safe and stable operation of the power system.With the rapid development of my country’s power industry,the power system level and transmission capacity continue to increase,and higher requirements are placed on the breaking performance of the SF6 circuit breaker.Compared with carrying out experimental research,the method of numerical simulation analysis has the advantages of low cost,high efficiency and short cycle.To this end,a 252 k V SF6 circuit breaker is researched and analyzed in this paper.A suitable mathematical model was established to simulate the no-load breaking and short-circuit current breaking process of the circuit breaker,and the influence factors of the dielectric recovery intensity,the dynamic arc characteristics and the breaking characteristics during the breaking process of the circuit breaker were analyzed and studied.The main tasks are as follows:(1)A two-dimensional finite element model is established according to the structure of a 252 k V SF6 circuit breaker.Simulation and analysis are made for the electric field and airflow field of the circuit breaker.The variation curve of the electric field non-uniform coefficient f with the contact open distance is obtained by electric field calculation.the electric field calculation result is introduced into the flow field,and the mathematical model of dielectric recovery is established based on the stream injection theory.The breakdown voltage between the contacts gap SF6 gas under different pressure is calculated.And analysis were made for the influencing factors of the cold dielectric recovery characteristics of the circuit breaker.(2)Based on the conservation control equations of fluid mechanics,the P-1 radiation model and the standard k-ε turbulence model are used to consider the radiation and turbulence effects in the arc,and the arc simulation model is established.The arc simulation calculation of the circuit breaker is performed,and the different moments of extinction are obtained through the simulation calculation.The distribution of parameters such as temperature and pressure in the arc extinguishing chamber at different times is obtained,and the dynamic changes of the arc during the breaking process and the characteristics of the pressure and airflow in the arc extinguishing chamber during the arcing process are analyzed.(3)Through arc simulation calculation of the circuit breaker short-circuit current,the pressure and temperature parameters in the arc extinguishing chamber at different moments such as the first zero crossing of the arc,the current peak value,and the current extinguishment under different opening speeds,different opening phase angles,and different charging pressures are obtained.The influence of different influencing factors on the breaking process is analyzed,and the influence of different influencing factors on the temperature and pressure in the arc extinguishing chamber is analyzed during the arcing process.The mathematical model of dielectric recovery is used to calculate the dielectric recovery strength after the arc under different conditions.The dielectric recovery strength after the arc under the influence of different breaking phase angles and different pressures are analyzed.The numerical calculation results and simulation analysis are combined to further determine the excellent breaking conditions. |
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