Simulation On Gas Flow Field Of 550kV SF₆/N₂ Mixed Gas Disconnector

With the continuous improvement of my country’s electricity level,researches on high-voltage disconnectors are imperative.According to researches,the SF₆/N₂ mixed gas has better insulation properties and arc extinguishing properties,which can be used to replace SF₆ gas,thereby reducing the harm to the environment and the human body.However simulation on the airflow field of the disconnectors with higher calculation accuracy is of great significance for understanding the breaking characteristics and realizing the optimal design and performance improvement.At the same time,it can also reduce the number of tests and reduce research and development cost.Therefore,the 550k V SF₆/N₂ mixed gas disconnector is selected as the research object to study the characteristics of the air flow field during the breaking process in this paper.It is firstly calculated that the viscosity,constant pressure specific heat,thermal conductivity and diffusion coefficient of SF₆,N₂ and their mixed gas,and then the geometric and mathematical model of the 550k V SF₆/N₂ mixed gas disconnector is built.It is put forward that the criteria for judging the quality of the grid,as well as a method for calculating the cold air flow field and two methods of calculating the hot air flow field,and dynamic grid technology is used for simulation calculation.In this paper,the 550k V SF₆/N₂ mixed gas disconnector’s air flow characteristics in the cold state are simulated and studied,and the pressure,density and temperature changes between the static and dynamic arc contacts are studied,as well as the medium recovery characteristics and the influence of contact moving speed and inflation pressure on the cold air flow field.After that,the simulation on the hot air flow field under the loading of a small DC current is carried out to study the pressure,density and temperature changes between the dynamic and static arc contacts,as well as the influence of contact moving speed and inflation pressure on the hot air flow field.Finally by loading the same size of alternating current,the difference of the airflow field distribution of the disconnector when the alternating current and the direct current are loaded is studied.According to the above research results,it can be concluded that:The pressure,density and temperature between the static and dynamic arc contacts in the cold state change in an attenuation curve,first decrease and then increase,until it is infinitely close to the initial state;The medium recovery characteristic of the disconnector is good in the cold state;The faster the contact moving speed,the more conducive to the breaking of the disconnector in the cold state,and the inflation pressure has less influence on the breaking characteristic of the disconnector in the cold state;In the hot state,the pressure between the static and dynamic arc contacts is distributed around the initial pressure in a decay curve,but its change range is smaller than the pressure change range in the cold state.The arc start to burn stably at about 10ms,and the temperature is about 1270K.With the increase of the opening distance,the arc is continuously elongated and extinguished at about 30 ms.The faster the contact moving speed,the greater the inflation pressure,the more conducive to the breaking of the disconnector in the hot state;The arc temperature when AC is loaded is lower than the arc temperature when DC is loaded and its breaking time is shorter.