Siemens S7-300 Installation And Operating Manual page 64

General technical data
7.3 Electromagnetic Compatibility
Surge protection for S7-300/ET 200M with fail-safe signal modules
If your system requires a degree of protection higher than severity level 2, it is advisable to
install an external protective circuit in order to provide sufficient surge strength to an S7-
300/ET 200M with fail-safe signal modules.
The precise type name is available in
Installation
Note
Lightning protection measures always require individual assessment of the overall plant. The
maximum surge protection can only be achieved if the entire building of the plant is
interconnected with a surge protection system. This involves in particular structural
measures in the building design phase.
In order to obtain comprehensive information about surge protection, you should consult
your Siemens partner or a company specializing in lightning protection.
64
Lightning and surge voltage protection
, chapter
S7-300 Automation System, CPU 31xC and CPU 31x:
.
Installation and Operating Manual, 01/2010, A5E00085586-10
Fail-safe signal modules