Development of Tracking and Tree-Like Structures From Voids at Dielectric Interfaces

Long-term degradation of polymer insulation systems is a major reliability issue for the electrical generation and supply industries. In the laboratory, unrepresentative needle geometries are ubiquitously used to generate and study electrical tracks and trees. This paper describes how tree-like structures and tracking can be generated, without the use of needles, from an engineered cavity at the interface between two polymers. Under these conditions trees can be grown at relatively low average applied fields of 2 kV/mm. Characteristic partial discharge activity and light emission are associated with the generation of tree channels. A model describing the growth of such defects is presented containing five stages. The paper provides insight into how interfacial stress can lead to failures in high-voltage systems. X-Ray Computed Tomography (XCT) was used to characterize the channel structures and establish a correlation between PD and the shape and type of channel. The use of such voids may present an alternative and improved platform, compared to traditional needle-plane geometries, for investigation of insulation failure.