Partial Discharge Properties till Breakdown of Boehmite Added Enameled Twisted Pair under Bipolar Repetitive Impulse Voltage Application

This paper presents partial discharge (PD) degradation and life characteristics of enamel twisted pair coated with nano-boehmite (AIOOH) filler added polyimide (PI) layer under bipolar repetitive impulse voltage application for developing surge resistant winding that exceeds the conventional insulation life. An attempt is also made to compare thus obtained results with those for additive-free PI sample (PI neat). An electric circuit using a capacitance connected in series with a sample was constructed to measure PD charge till breakdown (BD). Experimental results revealed the time to breakdown of boehmite/PI extended over that of PI neat, while the average PD charge increased with time and then dropped after the peak, leading to BD. This result was interpreted by the erosion suppression effect of the boehmite filler accumulating on the layer surface due to PD degradation.