Siemens simatic ET 200MP, System Manual

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Wiring
6.2 Operating the ET 200MP on grounded incoming supply
ET 200MP Distributed I/O System
System Manual, 01/2013, A5E03723484-01
53
6.2 Operating the ET 200MP on grounded incoming supply
Introduction
The following provides information on the overall configuration of an ET 200MP distributed
I/O system on a grounded incoming supply (TN-S network). The specific subjects discussed
are:
●
Shut-off devices, short circuit and overload protection in accordance with IEC 60364
(corresponds to DIN VDE 0100) and IEC 60204 (corresponds to DIN VDE 0113).
● Load power supplies and load circuits.
Grounded incoming supply
In grounded incoming supplies, the neutral conductor of the supply line is grounded. A single
fault between a live conductor and ground or a grounded part of the installation results in
tripping of the protective devices.
Safe electrical isolation (SELV/PELV in accordance with IEC 60364-4-41)
Network devices/power supply modules with safe, electrical isolation are necessary for
operating the ET 200MP. This protection is designated as SELV (Safety Extra Low
Voltage)/PELV (Protective Extra Low Voltage) in accordance with IEC 60364-4-41.
Reference potential of the ET 200MP
The reference potential of the ET 200MP distributed I/O system is connected internally with
the mounting rail (protective conductor) via a high-resistance RC combination. In this way,
high-frequency interference currents are conducted and electrostatic charges are avoided.
Despite the grounded mounting rail, the reference potential of the ET 200MP has to be
considered as ungrounded due to the high-resistance connection.
If you wish to configure the ET 200MP with grounded reference potential, then connect the
reference potential of the interface module (M connection) galvanically with the protective
conductor.
A simplified representation of the potential relationships is available in the chapter Electrical
configuration of the ET 200MP (Page 56).