Sparkover is defined as a disruptive discharge along which path?

• A. Through the air
• B. Across a dielectric surface
• C. Along a solid material such as an insulator string
• D. Along a liquid

Answer: (C)

Sparkover is the disruptive discharge that travels along the surface of insulation, i.e., creepage along a solid insulating medium such as an insulator string, rather than jumping through air. When the insulation surface becomes contaminated or moist, its surface resistance drops and a conductive path forms along the solid dielectric, allowing breakdown to occur along the material between conductors or to ground. This surface path is distinct from arcing through air, which would involve a gap in the air rather than a path along insulation, and from discharges through liquids or across dielectric surfaces in a way that doesn’t involve the solid insulating surface itself.