Appendix
A.3 Lightning and surge voltage protection
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
A-19
Note
This section can only provide information on the protection of a PLC against surge voltage.
However, complete surge protection is guaranteed only if the whole surrounding building is
designed to provide protection against overvoltage. This applies especially to constructional
measures for the building at the planning stage.
If you wish to obtain detailed information on surge protection, we therefore recommend you
contact your Siemens partner or a company specialized in lightning protection.
A.3.2 Lightning protection zone concept
Principally of the Lightning protection zone concept to IEC 61312-1/DIN VDE 0185 T103
The principle of the lightning protection zone concept states that the volume to be protected
against overvoltage, for example, a manufacturing hall, is subdivided into lightning protection
zones in accordance with EMC directives (see Figure ).
The specific lightning protection zones are formed by the following measures:
Lightning protection of the building exterior (field side) Lightning protection zone 0
Shielding
• Buildings
• Rooms and/or
• Devices
Lightning protection zone 1
Lightning protection zone 2
Lightning protection zone 3
Effects of the Lightning Strike
Direct lightning strikes occur in lightning protection zone 0. Lightning strike generates high-
energy electromagnetic fields which can be reduced or eliminated from one lightning
protection zone to the next by suitable lightning protection elements/measures.
Overvoltage
In lightning protection zones 1 and higher, a lightning strike might additionally cause
overvoltage as a result of switching operations, coupling etc.
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