Outdoor Routing Of Cables; Lightning And Surge Voltage Protection; Overview - Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual

Appendix
A.3 Lightning and surge voltage protection
A.2.9

Outdoor routing of cables

Rules for EMC-compliant cable routing
The same EMC-compliant rules apply both to indoor and outdoor routing of cables. The
following also applies:
• Running cables on metal cable trays.
• Electrical connection of the joints of cable trays/ducts.
• Ground the cable carriers.
• If necessary, provide adequate equipotential bonding between connected devices.
• Take the necessary (internal and external) lightning protection and grounding measures
Rules for lightning protection outside buildings
Run your cables either:
• in metal conduits grounded at both ends, or
• in concrete cable ducts with continuous end-to-end armoring.
Overvoltage protection equipment
An individual appraisal of the entire plant is necessary before any lightning protection
measures are taken.
A.3

Lightning and surge voltage protection

A.3.1

Overview

We show you solutions for the protection of your S7-300 against damage as a result of surge
voltage.
Failures are very often the result of surge voltage caused by:
• Atmospheric discharge or
• Electrostatic discharge.
We will begin by showing you what the theory of surge protection is based on: the lightning
protection zone concept
At the end of this section, you will find rules for the transition points between individual
lightning protection zones.
A-18
in as far as they are applicable to your particular application.
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05