Analysis Of The Factors Affecting The Breaking Characteristics Of 363KV SF₆ Circuit Breaker

The high-voltage SF₆ circuit breaker is used as an overload protection equipment in the power system and the breaking performance affects the daily operation of the power grid.In the process of breaking current,the arc will be generated between the moving and static contacts.How to extinguish the arc quickly and ensure the success of thermal recovery is the key to the research in this field.The gas parameters during the arc extinguishment have a direct impact for the success of interruption.On the one hand,the charging pressure affects the pressure,velocity,and density of the dielectric.Above characteristics determine the temperature of the arc-quenching chamber and affect the recovery of dielectric insulation;On the other hand,the metal vapor and residual free electrons between the contacts may be re-burned under the uneven electric field,then resulting in breaking failure.So the research on the influencing factors of dielectric recovery characteristic has important significance for optimizing the performance of high-voltage SF₆ circuit breakers.Based on above background,this dissertation was selected 363kV compressed gas SF₆circuit breaker as the research object.Simulation analysis with the help of ANSYS Fluent then modeling and analysis the watershed part to simulate the breaking action under no-load and load working conditions.Calculated the changes of electric field intensity,Mach number,pressure,temperature and density at different opening distance,then analyze the influence of gas parameters on arc energy during the breaking process and their changes under different charging pressure.Then draw the transient recovery voltage graphic with the circuit near-field fault and compare with the breakdown voltage curves of charging pressure at 0.5Mpa,0.6Mpa,0.7Mpa and 0.8Mpa respectively to judge the influence of charging pressure on breaking performance.Using the conclusions based on the above analysis,this dissertation was proposed a way to increase the breaking performance by setting incremental gas pressure,which the breakdown voltage was calculated by functions to control the incremental gas pressure.The result shows that under the no-load condition,the constant charging pressure increases,the breaking down voltage increases accordingly.In the load condition,the constant charging pressure directly affects the airflow speed.With the increasing of the opening distance,the dielectric flow speed is accelerated,and the high-temperature gas produced by the arc can be quickly discharged out of the arc-quenching chamber to improving the breaking performance.When the maximum charging pressure is the same,the dielectric flow speed under the increasing charging pressure is higher than that under the constant charging pressure condition,which made the arc-quenching chamber cool down rapidly.When the circuit breaker under load condition,increasing the gas pressure is an effective way to improve the breaking capacity.Compared with the constant pressure condition,the incremental gas pressure condition made the breaking time advance greatly during the breaking process.This method can increase the breaking speed of the circuit breaker effectively and enhance the reliability of the breaking circuit without changing the structure of the arc-quenching chamber.