It is known from literature that several electrical characteristics such as Partial Discharge (PD) Resistance of Polypropylene (PP) Films can be improved by homogeneous dispersion of Nanofillers into the polymer matrix. In this work, effect of variation in aging voltage on PD characteristics of PP and its remnant breakdown strength (BDS) is investigated for unfilled (PP+0%) and natural Nanofilled PP (PP+2% and PP+6%)
Using PD measurement set up several AC voltages (multiple of inception voltage, Vi) are applied on each sample for a duration of two hours and PD parameters such as average discharge; maximum discharge, Weibull Scale (α) and Shape Factor (β) of PD distribution etc. are continuously acquired. After the completion PD measurement experiments, surface erosion of aged PP samples was measured using Profilometer to investigate effects of change in applied voltage and Nanofillers concentrations on the PD Resistance of PP samples. Using microscopic analyses degradation of PP samples were evaluated. At the end, Breakdown Strength Measurement experiment of all unaged and aged PP samples were conducted to dig into the effect of degree of aging of PP samples on their breakdown strengths when the samples contained different amounts of nanofillers.
Variation of applied voltage influences PD characteristics because of different space charge accumulation threshold voltages for unfilled and Nanofilled PP samples. Above a threshold voltage rate of space charge accumulation is lower in Nanofilled PP than in base PP. Percolation limit of filler concentrations will also play a vital role on the variations in PD characteristics. Above a percolation limit discharges become higher because of the presence of surpassable double layers.
Changes in aging voltage will affect the polymer morphology changing the BDS in turn. Two parameter (Scale Factor α and Shape Factor β) Weibull Distribution were used to analyze breakdown strength of all samples. Comparison of PD characteristics of all samples (unaged and aged) were done finally and the effect of voltages on PD during aging and consequently the remnant Breakdown Strength in presence and absence of nanofillers were investigated.