Water Treeing in Solid Dielectrics

The phenomenon of water-tree degradation of polyolefin insulating materials is reviewed with particular emphasis on the materials aspect of the problem. Specific topics include: methods of producing water trees in the laboratory, water-tree morphology, the nature of tree growth curves, and the effects of temperature, material, electrical variables, chemical factors and physical and mechanical changes on tree growth. Proposed mechanisms for tree initiation and growth, and contradictions in mechanisms and observations, are analyzed. Where possible, suggestions are made for experiments which would help clarify points of dispute. Appendices contain commonly accepted methods for staining treed materials, including filled rubber.