Degradation mechanism of A12O3 nano filled polyimide film due to surface discharge under square impulse voltage

Failure mechanism due to corona aging and characteristics of PD (partial discharge) on nano doped PI (polyimide) film are investigated under bipolar impulse voltage. Chemical characterization of material is analyzed through SEM (scanning electron microscope) and FTIR (Fourier transform infrared spectroscopy). The results show that failure of specimens is mainly caused by surface discharge which could be suppressed by the addition of nano particles. The Al₂O₃ nano fillers improved the corona resistant property of PI film significantly. The corona resistant lifetime of PI/Al₂O₃ sample is six times longer than that of pure PI. Furthermore, to know the frequency and rise time effect of surface discharge on specimens, mean discharge quantity of PD under impulse voltage is measured. Increase of pulse frequency leads to enhancement of PD activity, whereas increase of rise time, weakens PD activity. The discovered effects of profound significance will help on improving dielectric properties of nanocomposites towards various applications.