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

Configuring

5.8.5 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, and 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 5-8
Device
Cabinet/mounting
structure
Rack / rail
Module
I/O Device
Sensors and actuators
5-26

Protective grounding measures

Measures
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
and not interconnected with larger metallic parts.
None
Grounding via Schuko plug
Grounding in accordance with regulations applying to the
system
S7-300 Programmable Controller Hardware and Installation
2
, if the rails are not installed in the cabinet
A5E00105492-02