Effect of Thermal Aging on Space Charge Dynamics in LDPE

Understanding space charge phenomenon in polyethylene under long-term thermal stress is essential and is of huge practical importance. In this article, low-density polyethylene (LDPE) sheet samples are thermally aged for up to 256 days, and space charge dynamics are investigated at low and high electric fields experimentally. For highly aged samples, the space charge is measured in the vicinity of breakdown. A clear difference in trend of packet-like charge movement is observed in the highly aged samples when compared to packet charge of fresh samples reported until now. Interesting insights on the injection and movement of charges through the bulk, mean accumulated charge density, field enhancement factor (FEF), and the shift of space charge regimes with aging are presented, which were apparently not given adequate attention in the literature so far. The results are believed to be useful for high-voltage direct current (HVdc) insulation designers and utilities.