Siemens SIMATIC ET 200M Operating Instructions Manual page 56

Assignment planning
3.6 Configuring the electrical structure
3.6.3 Configuration of an ET 200M with ungrounded reference potential
In the configuration of the ET 200M with ungrounded reference potential, the occurring
interference currents are deflected to the grounding wire via an RC network that is integrated
in the IM 153-x (see following figure).
For information on older IM 153-x versions, refer to Appendix "RC network with 1 MΩ for a
configuration with ungrounded reference potential (Page 246)".
Application
In extensive units it may be necessary, e.g. for the purposes of earth leakage monitoring, to
configure the ET 200M with ungrounded reference potential. This is the case, for example, in
the chemical industry or in power stations.
Connection diagram
The following figure shows the configuration of an ET 200M with IM 153-x and ungrounded
reference potential. If you don´t want to ground the reference potential, then you must
remove the bridge on the IM 153-x between the terminals M and the functional earth. If the
bridge isn´t connected then the reference potential of the ET 200M is connected internally to
the grounding wire via an RC combination and via the rail. This way, high-frequency
interference currents are deflected and static charge avoided.
①
*
Figure 3-12
Network devices
When using network devices, note that the secondary winding must not be connected with
the grounding wire. We recommend you use the power supply module PS 307.
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1
Ground bus
22 nF in IM 153-1AAx3, IM 153-2AA02, IM 153-2BA00, IM 153-2AB01, IM 153-2BB00
Configuration of an ET 200M with ungrounded reference potential
Operating Instructions, 12/2008, EWA-4NEB780600602-08
ET 200M