Surge protection components – lightning arrester material choice Which of the following components is commonly used inside modern lightning arresters/surge protectors to clamp overvoltage transients?

Introduction:
Lightning arresters and surge protective devices (SPDs) safeguard equipment by limiting transient overvoltages. The core element must switch from high to low impedance rapidly to absorb and shunt surge energy to ground.

Given Data / Assumptions:

• Protection against fast, high-energy impulses (lightning or switching surges).
• Device should exhibit strong voltage-dependent resistance.
• Widespread industrial practice.

Concept / Approach:

Metal-oxide varistors (MOVs) exhibit a highly nonlinear V–I characteristic: at normal line voltages they have very high resistance; under surges they conduct heavily, clamping the voltage. Gas discharge tubes are also used in some arresters, but among the given options the generic, correct choice is “Varistor.”

Step-by-Step Solution:

Verification / Alternative check:

SPD datasheets list MOVs as primary elements for Class II/Type 2 protections; thermistors are for temperature/current limiting; transistors are not surge clamping elements in high-energy lightning service.

Why Other Options Are Wrong:

Thermistors are temperature-sensitive resistors; photoconductors change resistance with light; transistors require bias and are not suitable for kA surges; tunnel diodes are specialized microwave components.

Common Pitfalls:

Confusing MOVs with TVS diodes; TVS diodes are used for lower-energy, faster ESD transients, while MOVs handle larger surge energy.

Final Answer:

Varistor