Siemens SIMATIC ET 200SP System Manual page 56

Wiring
5.3 Operating the ET 200SP on grounded incoming supply
Safe electrical isolation (SELV/PELV in accordance with IEC 60364-4-41)
Load current / power supply modules with safe electrical isolation are required for the
operation of the ET 200SP distributed I/O system. This protection is referred to as SELV
(Safety Extra Low Voltage) / PELV (Protective Extra Low Voltage) according to
IEC 60364-4-41.
Configuration of ET 200SP with ungrounded reference potential
To conduct interference currents, the reference potential of the CPU/interface module and
the BaseUnits BU15...D is connected internally via an RC combination (IM/CPU:
R = 10 MΩ / C = 100 nF, BU15...D: R = 10 MΩ / C = 4 nF) with the mounting rail (protective
conductor).
● This configuration conducts high-frequency interference currents and prevents static
charges.
● It is always possible to configure an ungrounded setup of the ET 200SP distributed I/O
system as the ET 200SP distributed I/O system has no fixed ground connection. The
power pack/power supply module for 24 V DC must also be ungrounded and electrically
isolated.
If you want to configure the ET 200SP distributed I/O system with grounded reference
potential, connect the 1M connection of the CPU/interface module electrically with the
protective conductor.
Short-circuit / overload protection
Various measures as protection against short-circuits and overloads are required for setting
up a full installation. The type of components and the binding protective measures depend
on which IEC (DIN VDE) regulation applies to your system configuration. The table refers to
the figure below and compares the IEC (DIN VDE) regulations.
Table 5- 1 Components and protective measures
Disconnecting device for controller,
sensors, and actuators
Short-circuit / overload protection:
In groups for sensors and actuators
Load current supply for AC load cir-
cuits with more than five items of
electromagnetic equipment
56
Refer to figure IEC 60364 (DIN VDE 0100)
①
Main switch
②
Single-pole protection of
circuits
③
②
Galvanic isolation by trans-
former recommended
IEC 60204 (DIN VDE 0113)
Disconnector
With grounded secondary
circuit: single-pole protection
otherwise: all-pole protection
Galvanic isolation by trans-
former recommended
Distributed I/O system
System Manual, 12/2015, A5E03576849-AF