Dielectric breakdown characteristics of HTV silicone rubber under multiple stress conditions

This study investigates the aging of high-temperature-vulcanized (HTV) silicone rubber insulator under multiple stress conditions. Silicone rubber specimens were subjected to accelerate degradation using an accelerated weathering chamber. The specimen was subjected to accelerated aging cycle in accordance to ASTM G154 cycle 4 for a total of 3000 hours. The aging cycle goes through a cycle of 70°C and ultraviolet exposure at irradiation intensity of 1.55 W/m² for eight hours followed by four hours condensation at 50°C. Morphology examination and chemical characterization using Scanning Electron Microscope (SEM) and Fourier Transforms Infrared Spectroscopy (ATR-FTIR) method are performed on the specimen. In this study, the aging performance of the silicone rubber insulator and the interdependence between the stressed material and dielectric breakdown strength are also under investigation. The results in this paper show that there are clear trend developed in the interval plots of the chemical elements such as carbon, oxygen, silicon and aluminum. These results agree with the decrease in the dielectric breakdown voltage as the period of aging cycle increases. The results obtained in this work indicate that the chemical characterization methods combining with electrical testing method can be used an effective tool to quantify and understand the aging process of silicone rubber insulator.