Comparative AC tracking and erosion resistance of micro-A1N and BN filled silicone rubber composites

Thermal degradation due to dry band arcing in the discharge region causes tracking and erosion failure of composite insulators. This work investigates resistance against tracking and erosion of silicone rubber filled with micron sized aluminum nitride (AlN) and boron nitride (BN) particles. Their performances are evaluated by comparing the average tracking length, eroded mass and thermal distribution across the tested specimens. Micron AlN (5-10 μm) and BN (5 μm) particles were acquired for fillers. For each test sample, the inclined plane test (IPT) according to IEC 60587 was carried out, lasted for 4 hours with initial applied voltage of 3 kV and then increased at a rate of 0.25 kV/h. The experimental findings indicate that remarkable resistance to tracking length and eroded mass is achieved with higher filler loadings of 20wt% and 30wt% of BN as compared to AlN. Thermal distribution results indicate that heat is mainly accumulated in the discharge region and higher BN loadings suppressed it more effectively than AlN counterparts. The maximum temperatures in the discharge region at 3.5 h of IPT are measured at 384°C, 440°C and 130°C for 0wt%, 30wt%-AlN and 30wt%-BN, respectively. It is concluded that BN provides better thermal conductivity than AlN which helps in dissipation and reduction of heat in the discharge region and improves the tracking and erosion resistance.