Analysis of interfacial metal Migration into dielectric materials subjected to high voltage stress

This paper presents the experimental results obtained during an investigation into the interaction at the interface between different dielectric materials and a copper conductor in an electric field during partial discharge action. The experimental setup compares the following metal-dielectric layers: cross-linked polyethylene, ethylene-propylene rubber, epoxy composite, dielectric enamel and paper insulation. The electrical mechanism of metal migration into a dielectric material is investigated through partial discharge patterns. The electric field-driven migration of the copper particles from the conductor to the insulating medium was observed. In order to understand the relationship between the electrical stress and the associated morphological changes, a microstructural analysis of the insulator surface, by means of electron microscopy and elemental analysis, was performed. The migration of metal particles into dielectric insulation systems might occur when a strong electric field is accompanied by certain thermal phenomena. It is important to recognize the role that a Cu conductor material plays in this phenomenon. Hence, the understanding of the migration mechanism and associated assessment criteria is a relevant and important research topic. Migration effects occurring at the metal/dielectric interface are presented quantitatively in the paper. A novel aspect relates to the investigation of the electrode metal concentration for different dielectric materials.