Overhead conductors are generally bare and insulated from other object by porcelain glass or _____________ insulators.

• A. polymer
• B. wood
• C. leather
• D. steel

Answer: (A)

Overhead conductors are kept apart from structures and other conductors by insulators that both isolate electrically and support the line. While porcelain and glass are traditional insulator materials, modern lines use polymer insulators as well. These are usually silicone-based or other rubber-like polymers that provide strong electrical insulation and good mechanical strength, but with the advantage of being lighter and less brittle than ceramic. They also have non-porous, hydrophobic surfaces that shed water, reducing leakage currents in wet conditions and helping prevent arcing. Materials like wood would absorb moisture and deteriorate, leather would similarly take on moisture and degrade, and steel is conductive, so it wouldn’t insulate. That’s why polymer insulators are the appropriate choice.