Siemens Simatic S7-300 CPU 31xC Series User Manual

Appendix
A.3 Lightning and surge voltage protection
S7-300, CPU 31xC and CPU 31x: Installation
A-18 Operating Instructions, Edition 08/2004, A5E00105492-05
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
in as far as they are applicable to your particular application.
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.

Siemens Simatic S7-300 CPU 31xC Series Specifications

General

Series	S7-300 CPU 31xC
Power Supply	24 V DC
Communication Interfaces	MPI, PROFIBUS DP
Programming Languages	LAD, STL, FBD, SCL
Operating Temperature	0°C to +60°C
Memory	48 KB - 512 KB
Dimensions	40 x 125 x 130 mm (varies by model)