Combined space charge and electroluminescence detection in polyethylene under AC stress

Time-resolved space charge and electroluminescence measurements are carried out during 50 Hz AC voltage cycles to probe injection, trapping and recombination of charges in polyethylene films. Space charge detection allows defining a field value above which space charge accumulates. This field is well correlated with the onset for electroluminescence. The behavior is consistent with a model of bipolar injection. It is also shown that different polyethylenes behave differently regarding the field above which charge is injected, providing a way to compare the ability of different materials to sustain AC field.