A Study of Composite Insulator Aging Using the Tracking Wheel Test

In this paper, silicone rubber (SR) insulators are investigated as to the aging behavior at different aging time in tracking wheel. Sampling was done every 200h till 2000h. Thermo Gravimetric Analysis (TGA), Fourier Transform Inferred Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), contact angle measurement, Energy Dispersive X ray scattering (EDX), mechanical and electrical tests were carried out for these purpose. The correlation coefficient of 0.9 proved an acceptable relation between migration of smaller size low molecular weight molecules (SLMWs) and contact angle. TGA and extraction testes results showed SLMW are almost 15% of total LMWs and responsible for recovery of hydrophobicity. Also TGA results demonstrated that after 2000h accelerated aging, thermal stability (potential thermal-resistant property) of the PDMS polymer decreases about 10%. ATR-FTIR analysis results showed the rate of Si-O-Si peak changes was higher than vSi-C and the vOH peak decreases by the 50%. The surface hardness increased about 20% with increasing aging time to 2000h. An average reduction of 30% and 25% in the tensile strength and strain at break were found with respect to the virgin sample aged. Increasing aging time increases leakage current from 50 to 500 (mu A) that still is lower than 1 mA so means there is no critical degradation.