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-20 Operating Instructions, Edition 08/2004, A5E00105492-05
Scheme of the lightning protection zones of a building
The figure below shows a block diagram of the lightning protection zone concept for a
detached building.
Lightning protection zone 0 (field side)
Lightning protection
zone 2
Lightning protection zone 1
Data cable
Power
cable
Internal
cable
Metal
part
Lightning
protection
zone 3
device
Lightning protection
equipotential bonding
Local equipotential
bonding
Building shielding
(steel armor)
Room shielding
(steel armor)
Device shielding
(metal housing)
Nonelectrical
cable (metallic)
External
lightning
protection
Principle of the transition points between lightning protection zones
At the transitions points between lightning protection zones, you must take measures to
prevent surges being conducted downstream.
The principle of the lightning protection zone concept also specifies that all cables which are
capable of carrying lightning current (!) and installed at the transition points of lightning
protection zones must be included in the equipotential bonding.
Conductors and cables capable of carrying lightning current are:
• Metal pipes (e.g. water, gas and heat)
• Power cables (for example, mains voltage, 24 V supply)
• Data cables (for example, bus cable).

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)