Siemens SIMATIC S7-300 Hardware And Installation Manual page 209

• Use grounded, spiraled, current-conducting metal straps or metal braiding as a
cable shield at both ends, for example, NYCY or A2Y(K)Y.
• Install cables in one of the following media:
in continuous metal pipes that are grounded at both ends, or
–
in continuously armored concrete ducts or
–
on closed metal cable trays grounded at both ends.
–
Use optical waveguides instead of metal conductors.
–
Additional Measures
If you cannot take measures as described above, you must install a high-voltage
protection for your system between the 0 <-> 1 transition points with a lightning
conductor. The table below contains the components you can use for high-voltage
protection of your plant.
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
Appendix
11-21