Calculation and analysis the dynamic breakdown characteristic of SF6 discharge caused by GIS disconnector operation

In order to accurately calculate the very fast transient overvoltage(VFTO), it is very important and necessary to carry out the study on breakdown characteristic of SF6 gas discharge and get the expression of critical breakdown voltage during GIS disconnector operation. Therefore, a study of dynamic breakdown characteristic of SF6 discharge caused by GIS disconnector operation is conducted. For gas discharge modeling, considering the micro discharge process will lead to the problems of complex modeling and difficult solution. A new method which can avoid the problems of complex modeling and solution is proposed in this paper. Researches have revealed that there is a certain relationship between the critical electric field breakdown strength and the gas density. Thus, the solution of dielectric strength is transformed into the solution of gas density. Then a 3D multiple physical field coupling model of disconnector operation to solve the gas density is established. The dynamic meshing technology is applied to solve the problem of dynamic description contact moving. And then linear regression fitting method is used to obtain the expression of dynamic breakdown voltage of SF6 gas discharge. After checking the quality of fitting function by index F, P and R-2, the SF6 gas breakdown voltage expression with the characteristic of dynamic variation under different operation conditions are obtained successfully.