Thermal analysis and tracking process in hybrid composites of silicone rubber

Abstract

Carbonized tracking due to thermal depolymerization on weather-shed materials of polymeric insulators is one of the key insulation failure modes, adversely affecting the reliability of power delivery networks. This paper investigates the tracking process and thermal distribution of micron-AlN and hybrid micron-AlN + nano-silica filled silicone rubber composites. Micron sized aluminum nitride (AlN: 5∼10 μm) and nano-silica (SiO2: 20 nm) particles were procured for fabricating composites in this work. The inclined plane test according to IEC 60587 was used; tracking voltage method 2 was adopted with initial applied voltage of 3 kV and ramping rate of 0.25 kV/h over duration of 240 minutes. Measurement results show hybrid composites exhibit substantially lower tracking length as compared to micron-AlN filled composites. Thermal accumulation is found significantly reduced in hybrid composites which could be due to better thermal stability and thermal conductivity. Moreover, the hybrid set of filler particles may increase the surface area of particles in the composites, provide better scattering, reduce secondary electron collision and impede release of high energy causing thermal depolymerization.