Power lines are often protected by lightning _____ that exhibit a very high resistance at the normal volt of the line.

Power lines are often protected by lightning _____ that exhibit a very high resistance at the normal volt of the line.

• A. Fuses
• B. Switches
• C. Insulators
• D. Arrestors

Answer: (D)

Surge protection on power lines relies on devices that stay nonconductive at normal voltage but become conductive during a surge. Lightning arrestors are designed to have a very high impedance when the line voltage is normal, so they don’t draw current or waste power. When a lightning-like surge raises the voltage, the arrestor conducts and provides a low-impedance path to ground, damping the surge and keeping equipment safe downstream. Fuses would only react to excessive current and then open the circuit, switches are control devices, and insulators block current but don’t provide a path to ground for surges. So the device described is lightning arrestors.

Surge protection on power lines relies on devices that stay nonconductive at normal voltage but become conductive during a surge. Lightning arrestors are designed to have a very high impedance when the line voltage is normal, so they don’t draw current or waste power. When a lightning-like surge raises the voltage, the arrestor conducts and provides a low-impedance path to ground, damping the surge and keeping equipment safe downstream. Fuses would only react to excessive current and then open the circuit, switches are control devices, and insulators block current but don’t provide a path to ground for surges. So the device described is lightning arrestors.