Effect of surface discharge on nano filled polyimide film under square voltage

Failure mechanisms and PD (partial discharge) characteristics on rigid polyimide film are revealed under bipolar pulse voltage. Mean discharge quantity of PD under square waveform is measured for pure polyimide (PI) and nano doped PI film. Results of Scanning Electron microscope (SEM) showed that surface discharge (corona) is main reason of PI insulation material failure and nano particles addition can suppress PD activity. Increase in frequency leads higher PD activity, while increase of rise time decrease PD activity. The results show that the traps during mobility and residual effect of space charges have larger influence on PD activity, and high surface conductivity of nano samples can reduce memory effect of charges and PD activity. The nano filler provides shielding layer to repel surface erosion and thermal conduction.