Three types of material from which a guy strain insulator is manufactured are porcelain, fiberglass, and which material?

• A. Glass
• B. Carbon
• C. Nylon-reinforced steel
• D. Wood

Answer: (D)

Materials chosen for guy strain insulators must provide good electrical insulation while standing up to outdoor weather and the mechanical load of the line. Historically, three families have been used: porcelain, glass, and wood. Porcelain and glass are ceramic insulators with strong dielectric strength and weather resistance, but wood has also been used because it’s readily available, easy to shape, and can be treated to improve moisture resistance. In contexts where a traditional set is taught, wood completes the trio alongside porcelain and fiberglass (the modern polymer alternative). So, wood fits as the third material in this traditional lineup. The other options aren’t used as insulator materials in this specific context.