Effect of cross-linking temperature on charge decay behavior in XLPE

XLPE films were employed as test samples to investigate the effect of cross-linking temperature on space charge decay behavior. The samples were cross-linked with temperature ranged from 150 °C to 180 °C in thickness of 200 µm. Corona charging method was employed to introduce charges on sample surface, after which open-circuit decay test was carried out at 35 °C with relative humidity of ~ 45%. Surface potential was measured by using an electrostatic probe, and mean decay rate of the charge was calculated. In addition, fourier-transform infrared (FTIR) spectroscopy was used to analyze the characteristic functional groups of byproducts that were generated in the cross-linking process within the samples. Obtained results show that with the increase of cross-linking temperature, mean decay rate of both negative charge and positive charge initially decreases then appears to increase. The decay behavior remarkably depends upon the polarity of charged particles. It is proposed that the charge decay dynamics is related to the content of cross-linking byproducts, namely acetophenone, cumyl alcohol and α-methylstyrene, which is varied as a function of the cross-linking temperature.