Suppression of Surface Charge Accumulation on GIS Insulator in Extremely Cold Environment by Functional Nonlinear Conductivity Coating Design

Surface charge accumulation distorts the electric field and induces flashover along the GIS insulator, harming the reliability of power system. When GIS works in extremely cold regions, a huge temperature gradient is generated along the insulator, causing further surface charge accumulation, but its investigations are scarce due to the tough measurement conditions. Herein, a surface charging simulation model involves electro-thermal-fluid multiphysics fields and surface charging differential equations is established to analyze the surface charging in a cold environment, and a conventional high conductivity coating and a nonlinear conductivity coating design are applied to the insulator to suppress charge accumulation. The numerical simulation indicates a large temperature gradient is produced along the insulator by decreasing environment temperature, increasing current, or increasing heat transfer coefficients, causing lots of charges to accumulate near the ground electrode. The application of nonlinear conductivity coating effectively suppress charge accumulation in extremely cold environments, and the maximum charge density drops by 41.5% and 50.4% for convex and concave insulators compared to uncoated insulator, which is superior to conventional high conductivity coating that exhibits 31.6% and 37.7%. The charging path analysis indicates although conventional high conductivity coating reduces charges near the ground electrode, it elevates charge density at other positions. For nonlinear conductivity coating, it only regulates charges near the electrode with the large electric field. This work presents charge accumulation characteristics and its inhibition strategy for insulators in extremely cold environments, which are beneficial for protecting GIS secure operation in extreme conditions.