Siemens SIMATIC ET 200AL, System Manual

Page: 2244 / 2255

Designing interference-free controllers
26
Function Manual, 06/2014, A5E03461486-AB
Lightning protection and overvoltage protection
7
7.1 What is lightning and overvoltage protection?
Introduction
The term "Lightning and overvoltage protection" covers both the concept and system for the
protection of structural systems (such as buildings or electrical equipment). This concept
also includes the protection of people and animals.
Overvoltages are most frequently caused by lightning strikes.
Lightning protection system
The lightning protection system is the complete system used to reduce physical damage to a
structural system as a result of direct lightning strikes and overvoltages. The lightning
protection system is divided into external and internal lightning protection.
External lightning protection
External lightning protection is part of the lightning protection system and comprises an
interception device, an arrester and a grounding system. In the event of a lightning strike, the
external lightning protection serves to divert the lightning current safely to the ground. This
measure most frequently prevents fire damage.
Internal lightning protection
Internal lightning protection is part of the lightning protection system and comprises lightning
protection equipotential bonding and/or electrical isolation with respect to the external
lightning protection. In the event of a lightning strike, the internal lightning protection reduces
the damage caused by overvoltages resulting from the lightning.
Even at larger distances of up to 1.5 km, lightning strikes can sometimes still cause damage.
You obtain effective lightning protection by expanding the external lightning protection into
an overall protection system. This system includes equipotential bonding and surge
protection devices.