A composite insulator containing means for providing early warning of impending failure due to stress corrosion cracking, flashunder, or destruction of the rod by discharge activity conditions is described. A composite insulator comprising a fiberglass rod surrounded by a polymer housing and connected with metal end fittings on either end of the rod is doped with a dye-based chemical dopant. The dopant is located around the vicinity of the outer surface of the fiberglass rod. The dopant is formulated to possess migration and diffusion characteristics, and to be inert in dry conditions and compatible with the insulator components. The dopant is positioned within the insulator such that upon the penetration of moisture through the housing to the rod through a permeation pathway in the outer surface of the insulator, the dopant will become activated and will leach out of the same permeation pathway or diffuse through the housing. The activated dopant then creates a deposit or stain on the outer surface of the insulator housing. The dopant comprises an oil-soluble dye, an indicator, or a stain compound that can either be visually identified, or is sensitive to radiation at one or more specific wavelengths. The dopant could also be formulated by a nanoparticle enabled material. Deposits of activated dopant on the outer surface of the insulator can be detected upon imaging of the outer surface of the insulator by appropriate imaging instruments or the naked eye.
Joseph N. Mitchell; Spring M. Haby; Dennis S. Rushforth; Mark E. Van Dyke; Henry W. Oviatt Jr.; Andrew J. Phillips; Ralph H. Hill Jr.; Mary C. Marshall