Transient Electric Field Analysis Of Basin Insulaitor In Isolating Switch Under Fast Transient Overvoltage

Basin insulator plays an important role in isolating gas chamber,supporting conductor and insulation in GIS.Its performance is related to the stable operation of GIS.In the production process of basin insulator,there will be defects such as bubbles or impurities in the interior of the insulator due to non-standard operation,imperfect process and unstable equipment.When VFTO intrudes into the disconnector,defects such as bubbles will cause electric field distortion of the basin insulator,lead to partial discharge or surface flashover,affect the normal operation of GIS,and endanger the insulation safety of the basin insulator.It is of great significance to study the electric field distribution of the basin insulator under the action of VFTO for improving the security and stability of GIS operation.Firstly,one 1100 kV GIS substation is taken as an example in this paper,the equivalent simulation model of electrical equipment in GIS was built by using electromagnetic transient program.The VFTO of the main electrical equipment and transformers connected with the disconnector during the closing operation are simulated and calculated.The waveform,amplitude and main frequency of VFTO at disconnector are simulated.Based on the finite element theory,the electric field distribution of the basin insulator under VFTO or power frequency voltage is simulated and calculated when there are bubbles or wire defects inside the basin insulator,and the influence of the radial position and size of the bubbles or wire defects on the electric field distribution of the basin insulator is analyzed.The results show that under the action of VFTO,the closer the bubble defect is to the metal end,the stronger the electric field strength of the basin insulator is.When bubbles exist near the surface of the basin insulator,the electric field along the surface of the basin insulator will be distorted at the corresponding position,which will easily cause flashover or discharge along the surface of the basin insulator.The electric field distortion on and near the surface of bubbles is serious.The degree of distortion is related to the location and size of bubbles.In serious cases,partial discharge may occur,which endangers the insulation safety of basin insulators.Under the action of VFTO,when there are metal wire defects in the interior of the pot insulator,the maximum field strength is near the ends of the metal wire and the minimum field strength is in the middle of the metal wire.The maximum field strength of the basin insulators is related to the radial position,size anddistribution direction of the metal wire.The existence of metal wire defects will seriously affect the safety of the pot insulator.