Correlation between antioxidant depletion kinetic model and ageing behaviour of cross‐linked polyethylene cable insulation

Abstract

AbstractA concise kinetic model catering for the antioxidant reaction of thermally aged cross‐linked polyethylene (XLPE) cable insulation before its abrupt performance deterioration is proposed for life prediction and condition assessment. The alternating current breakdown strength, elongation at break, carbonyl index, and pyrolysis activation energy of XLPE insulation are found to consistently display an abrupt change at a certain point of ageing time. This is strongly correlated to the depletion of the antioxidant whose content gradually decreases with ageing time and drops to a critical value, after which the abrupt degradation of the above macroscopic performances happens. Based on the simplified chain reactions of XLPE during thermal‐oxidative ageing, a concise kinetic model about antioxidant prediction is accordingly established by solving the chemical kinetics equations. It indicates that the antioxidant content decays with the reciprocal of time before the abrupt degradation occurs. Results of antioxidant content predicted by the kinetic model at different temperatures matches well with the experimental results, and its reliability can also be proved by the Arrhenius relationship of the obtained results. The kinetic model proposed herein demonstrates satisfying conciseness and thus can be highly feasible in ageing condition assessment and life predicting of XLPE insulation.