Wiring
6.2 Operating the S7-1500 on grounded infeed
S7-1500 Automation System
System Manual, 01/2013, A5E03461182-01
55
6.2 Operating the S7-1500 on grounded infeed
Introduction
The following provides information on the overall configuration of an S7-1500 on a grounded
infeed (TN-S network). The specific subjects discussed are:
● Disconnecting devices, short-circuit and overload protection to IEC 60364 (corresponding
to DIN VDE 0100) and IEC 60204 (corresponding to DIN VDE 0113).
● Load power supplies and load circuits.
Grounded infeed
In the case of grounding incoming supplies (TN-S system) the neutral conductor (N) and the
protective conductor (PE) are each grounded. Both conductors form a part of the overvoltage
concept. When a plant is in operation, the current flows across the neutral conductor. When
a fault occurs, for example a single ground fault between a live conductor and ground, the
current flows through the protective conductor.
Safe electrical isolation (SELV/PELV in accordance with IEC 60364-4-41)
Load current supply modules / power supply modules with safe electrical isolation are
necessary for operating the S7-1500. 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 controller
The reference potential of the S7-1500 automation system is connected with the mounting
rail through 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 S7-1500 automation system has to be
considered as ungrounded due to the high-resistance connection.
If you want to configure the S7-1500 automation system with grounded reference potential,
connect the reference potential of the controller (M connection of the CPU) galvanically with
the protective conductor.
A simplified representation of the potential relationships is available in the chapter Electrical
config
uratio
n of the S7-1500 (Page 58).
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