Research On VFTO In GIS Based On Dynamic Arc Model

At present,the level of international and domestic grid voltage is constantly improving.With the continuous improvement of the power grid voltage level,the demand for all aspects of the power grid is constantly improving.In the high-voltage transmission system,the high voltage switch electrical equipment has an important role.The SF₆ Gas Insulation Substation?GIS?is the most widely used electrical equipment.In GIS,a high frequency is present,and the wave head is very steep and the over voltage is very-fast-transient over voltage?VFTO?.VFTO may pose a threat to GIS and its adjacent equipment,even causing major accidents.Therefore,it is very important to study VFTO in GIS.The isolation switch arc model plays a key role in the calculation and simulation of VFTO in GIS.Current VFTO calculation is widely used in the electric arc model with fixed value resistance model and time-varying resistance model.These models have certain limitations and can not accurately simulate arc characteristics.Therefore,it is very important to simulate the arc model accurately.In this thesis,based on a 1000kV ultra-high voltage substation,the high voltage power distribution device adopts GIS,and the line terminal is equipped with parallel reactor and line terminal equipment.The simulation model of the actual circuit is built by using the graphic preprocessing program ATPDraw,and then the arc model is constructed by the MODELS module.The arc single breakdown model designed in this thesis is divided into three stages.The first stage,the prebreakdown phase,is simulated by the time-varying resistance model in this stage.The experiment shows that the arc can be accurately simulated by using the Cassie arc model in the stage of high current.Therefore,in the second stage,the steady combustion stage,the Cassie arc model is used to simulate the characteristics of the arc at this time.In the third stage,that is,the arc quenching stage,the characteristics of the arc are simulated by the Mayr arc model.The arc single breakdown model designed in this thesis is compared with the current arc model used in engineering practice to verify its applicability.Considering the actual situation,the arc can't exist only once.Therefore,combined with arcing criterion,arcing is decided by breakdown criterion according to breakdown criterion in real time.The arc reburning model is designed,the arc is simulated,and the simulation is carried out.Based on the single breakdown model of arc designed in this thesis,the influence of GIS branch length and inductance at isolation switch on the very-fast transient over voltage is studied by simulation.The influence of the contact velocity of the isolated switch on the very-fast-transient over voltage is studied through the simulation of the arc reignition model.Finally,the effects of the two factors on the suppression of the very-fast-transient over voltage are studied by simulation.