Electroquasistatic Field Simulation for the Layout Improvement of Outdoor Insulators Using Microvaristor Material

A possible solution to locally reduce the high electric-field stress along the surface of outdoor insulators is to use the resistive field grading materials such as zinc-oxide microvaristor polymer compounds. This material is nonlinearly semiconductive and its conductivity depends on the electric-field intensity. In this paper, the field control effect of this material is demonstrated. Different configurations in order to optimize the layout of this material are compared. A case study is carried out for a 765-kV outdoor large-scale long rod polymeric insulator using different layouts of the microvaristor material. Electroquasistatic simulations are performed to evaluate the tangential electric-field distributions along the surface of the insulator for the dry clean surface condition and with a few single water droplets on the surface.