Effect of Al(OH)3 and thermal ageing on the dielectric performance of composite insulator shed based on THz-TDS

Composite insulator shed is easy to be affected by temperature, ultraviolet radiation, and other factors, resulting in the declining of insulation performance and threatening the safe operation. This paper aims at studying the terahertz frequency domain characteristics of high temperature vulcanized (HTV) silicone rubber (SIR) by terahertz time-domain spectroscopy (THz-TDS). Besides, the effects of high temperature on HTV SIR and the ageing mechanism in terahertz frequency domain are explored. The results show that ATH (Al(OH)3) in HTV SIR has obvious characteristic peaks at 1.2THz and 1.33THz, which can also increase the refractive index and dielectric constant of HTV SIR. Moreover, thermal ageing increases the refractive index and dielectric constant of HTV SIR in terahertz frequency domain with ageing time. The results of Fourier transform infrared spectroscopy (FTIR) show that the intensity of -OH increases but the intensity of C-H, -CH3 and Si-O-Si decrease with ageing time, which helps explain the results of THz-TDS. This study shows that THz-TDS is of great significance to the detection of polymers.