Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 237

Key
The table below explains consecutive numbers in the figure above:
Table A-11 Example of a circuit conforming to lightning protection requirements (legend to previous figure)
Consec. no. Component
from figure
above
1 Lightning arrester, depending on the mains system, for
example, a TN-S system:
1 x DEHNbloc/3
Order no.: 900 110* and
1 x DEHNbloc/1
Order no.: 900 111*
2 Surge arresters,
2 x DEHNguard 275;
Order no.: 900 600*
3 Surge arrester
Blitzductor CT surge arrester, type MD/HF
Order no.: 919 506* and 919 570*
4 Digital input modules:
FDK 2 D 60 V order no.: 919 993*
Digital output modules: FDK 2 D 5 24 V order no.:
919 991*
Analog modules:
MD 12 V Blitzductor CT,
order no.: 919 506 and 919 541
5 Bus cable shielding mounting device with EMC spring
clamp on the basic unit of Blitzductor CT, order no.:
919 508*
6 Cable for equipotential bonding: 16 mm
7 Blitzductor CT, Type B for building transitions;
order no.: 919 506* and 919 510*
* Please order these components directly from:
DEHN + SÖHNE GmbH + Co. KG
Elektrotechnische Fabrik
Hans-Dehn-Str.
D-92318 Neumarkt
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
A.3 Lightning and surge voltage protection
Meaning
High-voltage protection against direct lightning
strike and surge voltage as of transition 0 <-> 1
High-voltage surge protection at transition 1 <-
> 2
Low-voltage surge protection for RS485
interfaces at transition 1 <-> 2
Low-voltage surge protection, signal modules
I/O at transition 1 <-> 2
Discharge of interference current
Standardization of reference potentials
High-voltage surge protection for RS485
interfaces at transition 0 <->1
Appendix
A-27