Grounding; Measures For Protective Grounding - Siemens SIMATIC S7-300 Hardware And Installation Manual

4.8.5

Grounding

Bonding
Low-resistance connections to ground reduce the risk of electric shock in case of a
short-circuit or system fault. Low-impedance connections (large surface, large-
surface contact) reduces the effects of interference on the system or the emission
of interference signals. Here, effective shielding of cables and devices is also a
significant contribution.
Warning
All protection class 1 devices, as well as all larger metal parts, must be connected
to protective ground. This is the only way to ensure that the system user is
protected from electrical shock. It also deflects interference which is emitted from
external power supply cables and signal cables to cables connected to I/O devices.

Measures for protective grounding

The table below shows an overview of the most important measures for protective
grounding.
Table 4-8
Device
Cabinet/mounting
structure
Module rack / profile rail
Module
I/O Device
Sensors and actuators
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
Measures for protective grounding
Connection to central ground (e.g. equipotential bus line) via
cables with protective conductor quality
Connection to central ground with cable of minimum cross-
section of 10 mm
cabinet and not interconnected with larger metallic parts.
None
Grounding via Schuko plug
Grounding in accordance with regulations applying to the
system
Measures
2
, if the profile rails are not installed in the
Configuring
4-21