Lifespan Evaluation of HTV Silicone Rubber in Outdoor Composite Insulators Considering Temperature Cycling and Corona Discharge

The reliability of high-voltage overhead lines is strongly correlated to the status of outdoor insulators, which is correlated to the condition of high-temperature vulcanized silicone rubber (HTV-SR) used as insulator sheds. Current research pays attention to HTV-SR’s degradation under different environmental stresses (e.g., temperature and corona discharge). However, the lifetime assessment of the aged HTV-SR is unclear, and the effect of temperature cycling is seldom considered. In this study, a remaining useful lifetime (RUL) prediction method for HTV-SR is proposed, which considers both temperature cycling and corona discharge. Accelerated lifetime tests of HTV-SR are conducted, and the key parameters of the model are determined by the experimental data. Thus, a formula for quantitative RUL prediction is put forward, which indicates that when the cyclic temperature is $5.5~^{\circ }$ C $\sim 21.3~^{\circ }$ C and the electric field strength at the sample surface is 4.5 and 6.8 kV/cm, the RUL with 90% reliability is 25.9 and 8.4 years. Furthermore, verification of the prediction model is conducted using the elongation at break of field-aged insulators with different operation times. This study provides a method to estimate the RUL of HTV-SR materials, which can guide the maintenance of outdoor insulators of power transmission lines.