Analysis of Packet-like Space Charge Behavior in Low-density Polyethylene

When a high dc electric field of more than 1 MV/cm was applied to low-density polyethylene (LDPE), a huge amount of positive packet-like charge of more than 100 C/m3 was injected into the bulk of the film and it moved towards the cathode side increasing its amount of charge. The movement of the packet-like charge gradually became slowly, and then it stopped in the bulk as it seems to be a stable state. Consequently, the electric field near the cathode was sometimes enhanced up to more than twice of the applied electric field. To analyze the feature of the positive packet-like charge behavior in LDPE, we carry out a simple numerical simulation based on the experimental results. The hypothesis is based on the idea that the zone where is passed through by the packet-like charge has a higher conductivity than that in front of the packet-like charge. By considering a simple model, we have a good agreement between the numerical simulation and the experimental results. Since an analysis for the behavior under dc stress has already shown before, an analysis under short circuit condition is mainly reported here.