AC LOSS AND DC CONDUCTION MECHANISMS IN POLYETHYLENE UNDER HIGH ELECTRIC-FIELDS

Polyethylene subjected to strong electric fields up to about 100 kv/mm was investigated. Based on an electronic charge carrier hopping transport model including trap-like and donor-like states, it is shown that the current is bulk-limited under both ac and dc conditions. However, the sources of the electronic charge carriers taking part in the ac loss and dc conduction processes, respectively, are different. At direct voltage, the electrons are injected from the cathode whereas at alternating voltage they are predominantly activated from donor-like states in the bulk of the dielectric by a Poole-Frenkel mechanism.