Model to estimate the trapping parameters of cross-linked polyethylene cable peelings of different service years and their relationships with dc breakdown strengths

In this study, an improved trapping/detrapping model was used to simulate the charge dynamics in cross-linked polyethylene peelings from different-year aged cables. Injection barrier of trapping parameters was estimated by the model fitted to experimental data for each type of sample. Moreover, dc breakdown tests were operated on those samples. It has been found that the dc breakdown strength of inner-layer samples is the lowest in cable sections with thicker insulation layer taken from high-voltage ac (HVAC) 220 kV service condition, whereas for the cable with thinner insulation from HVAC 110 kV, middle-layer samples have worst breakdown performance. This might be explained by the space charge issues under long-term HVAC condition. More importantly, a clear relationship between estimated model parameters, including injection barrier, trap depth and trap density, with the dc breakdown strength in each layer has been reported in this study.