Approach for Reliability Evaluation of Cross-Linked Polyethylene Under Combined Thermal and Vibration Stresses

Based on Wiener process model, a new approach for reliability evaluation of cross-linked polyethylene (XLPE) is proposed to improve the lifetime evaluation reliability of XLPE under multi-stressing conditions and study the failure probability distribution. In this paper, two accelerated aging tests are carried out under combined thermal and vibration conditions. The volume resistance degradation data of XLPE samples are tested with a 24 h interval under the accelerated stressing conditions at (130 °C, 12 m/s²) and (150 °C, 8.5m/s²), respectively. Nonlinear degradation data obtained from the experiment are transformed to linear intermediate-variable values using time scaling function, and then linearized degradation data are calculated and evaluated on the basis of linear Wiener process model. Considering traditional Arrhenius equation and inverse power criterion, parameters of the linear Wiener model are estimated according to the maximum likelihood function. The relationship curves on probability density and reliability are given, and the lifetime distribution of XLPE under different stressing conditions is also obtained for evaluating the reliability of XLPE insulation. Finally, the life expectancy of XLPE is 17.9 a under an allowance temperature of 90 °C and an actual vibration acceleration of 0.5m/s². The approach and results in this paper may be used for reliability assessment of high-voltage multiple samples or apparatuses.