Physical, thermal and partial discharge evaluation of nano alumina filled silicone rubber in inclined plane test

Silicone rubber (SiR) composite material is a modern-day insulator for high voltage outdoor applications. The imperfection attributed to SiR is its weak resistance to tracking and erosion when exposed to outdoor polluted environment which reduces its operational lifetime. This work investigates the performance of SiR with the addition of 0, 1, 2.5, 5, 10 and 20% by weight contents of nano alumina (Al2O3). Indined plane test is performed according to IEC 60587 with step up tracking voltage method with an initial voltage of 3.0 kV and the contaminant solution flow rate is maintained at 0.3 ml/min using a peristaltic pump. The applied voltage level is increased at a rate of 0.25 kV/h. Results suggest that physical tracking, erosion, RMS leakage current and surface partial discharge (PD) performance of samples is improved with the addition of nano alumina. The tracking length, eroded mass, RMS leakage current and average PD magnitude are measured 22%, 79%, 30% and 52% lesser in 20wt% relative to 0wt%, respectively. The thermal distribution analysis is undertaken with infrared camera and it is found that heat is accumulated in the discharge area of liquid flow. The maximum temperature on the insulating specimen is decreased with increasing nanofiller contents. The above promising findings can be due to better thermal stability with low chain mobility at the interaction zone of SiR and alumina. Moreover, less liquid evaporation due to better thermal conduction and improved physical bonding between SiR and nano alumina are possible reasons behind the excellent performance of nanocomposites.