Investigations of electrical aging in polymers under high AC field strength

To analyze the beginning of dielectric aging of polymeric materials under high alternating electric fields, different parameters were studied. All measurements were carried out on a PE needle-plane specimen. As the first stage, results from online measurements of charge-carrier injection at high field strength reveal repetitive charge-carrier motions through the metal-polymer interface as the initial mechanism of electrical aging. The second stage is characterized by electroluminescence phenomena at a significantly higher stress level. This level represents the beginning of polymer degradation, leading to tree initiation and finally to breakdown. This last stage is investigated by phase-resolved partial discharge measurements. The electroluminescence phenomena are strongly influenced by the amount of oxygen dissolved in the polymer