Temporal growth of partial discharge generated nanometric mica structures

Mica-polymer insulation systems are integral to high power rotating plant: mica is used in the insulation found in the stator windings of high power rotating plant as it provides high dielectric strength and resistance to partial discharge. Current and forecast future economic factors are forcing owners of high power rotating plant to assess the integrity and remnant life of mica based insulators as well forcing the development of plant life extension strategies. As exposure to partial discharge is thought to provide stress which leads to degradation of mica, contributing to eventual failure, experiments were undertaken to investigate the material effects. This paper compares and analyses mica in the natural condition with mica that has undergone exposure to point plane stressing with 2kV 1mm gap in air. Atomic Force Microscopy (AFM) was used to examine the resulting changes in surface topography.