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Knowledge Hub

From lightning concepts to low-voltage power-line SPD products—a structured guide for engineers, panel builders, and local partners.

2. Surge Phenomena & Overvoltages · Page 3 of 6

Insulation Coordination Basics

How surge levels relate to equipment withstand voltages.

Withstand voltage categories

Equipment is designed for certain impulse withstand levels depending on installation category (overvoltage category I–IV in IEC thinking).

Role of the SPD

An SPD lowers the expected transient voltage at a point in the installation so that it stays below the withstand of connected equipment, including a safety margin.

Cascaded protection

Upstream devices take energy; downstream devices refine the voltage. Coordination ensures the upstream SPD operates first under high-energy events.

← Sources of Surges in LV Networks

Common-Mode vs Differential-Mode Surges →

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