Study on short-term DC breakdown and coronaresistance mechanism of polyimide

Nano-doping has a significant effect on dielectric and electrical insulation for polymer dielectrics. Pure polyimide 100HN and nano-doping polyimide 100CR from DuPont Company are adopted to conduct short-term breakdown and long-term corona-resistant experiments. The results show that, the short-term breakdown strength of 100CR is 6.4% lower than 100HN. For long-term corona resistance, the corona-resistant time of 100CR is 400% longer than 100HN. In order to study the influencing mechanism of nanoparticles on short-time breakdown and long-term corona resistance, isothermal surface potential decay experiments were conducted to investigate traps characteristics of two samples. It is found that the traps energy and density of 100CR is less than that of 100HN. The volume conductivity of 100CR is much higher than 100HN. The eroded surface morphologies of 100HN and 100CR are observed by Scanning Electron Microscope, which are groove channels and different eroded layered rings respectively. The results show that the effect of nanoparticles on short-term breakdown and long-term corona resistance are different. For short-term breakdown, the main consideration is the change of traps and conductance changed by nano-doping. For long-term coronaresistance, the collision scattering effect of nanoparticles against the charged particles plays the dominate role.