In polymer/composite insulators, what is the typical construction?

• A. A ceramic housing around a steel core.
• B. A polymer housing around a fiberglass core.
• C. A glass housing around a carbon fiber core.
• D. A metal shell with a ceramic core.

Answer: (B)

In polymer/composite insulators, the outer shell is a polymer housing around a fiberglass core. The polymer outer layer provides electrical insulation, weather resistance, and a hydrophobic surface to shed water, while the fiberglass core supplies the necessary mechanical strength and stiffness to carry loads. This combination gives a lightweight, durable insulator with good performance in wet conditions, which is why it’s preferred over ceramic or glass housing designs. The other constructions mix materials not typical of polymer/composite insulators—ceramic or glass housings, or metal shells with ceramic cores—so they don’t match the standard polymer-over-fiberglass configuration.