The Influence of Electric Field Distribution on Insulator Surface Flashover

Insulator surface flashover is one of the main causations for the gas insulated metal enclosed switchgear (GIS) devices failure. The local electric field enhancement is the intrinsic reason for the surface discharge. To clarify the relationship between insulator surface flashover and its surface electric field distribution, we manufactured insulator samples with various shapes and embedded electrodes, then studied their flashover voltage under the standard lightning impulse in a vessel filled with 0.2 MPa pure SF6gas. In addition, we simulated the surface electric field distribution of samples by the finite element method, and analyzed the relationships between the maximum and average value of surface electric field strength. As a result, conclusions come as follows. As the size of the embedded electrodes increases, the flashover voltage of wave and concave insulators decreases, while that of the convex shape increases. The total surface electric field is of the greatest impact on the flashover voltage. The tangential component of the surface electric field contributes more than the normal component in the flashover voltage, but the latter could affect the flashover arc direction. In all case, the surface flashover initiation condition in this paper is about 75 kV/(mm·MPa) which is lower than the critical condition of 88.5 kV/(mm·MPa) in the SF6 gas gap.