■
Mounting the devices on conductive metal surfaces.
■
Correct grounding of the devices/metal surfaces in the system.
■
Low-impedance and current-carrying equipotential bonding between areas with dif‐
ferent ground potentials, if necessary.
=
4
=
3
1
2
8
5
7
6
CLV61x
Dual Port
IO Controller
(PLC)
Power Supply
I
U
PROFINET
PROFINET
Figure 16: Occurrence of equipotential bonding currents in the system configuration
1
IO controller (PLC)
2
Power supply
3
Shielded electrical cable
4
Metal housing
5
Grounding point 2
6
Closed current loops with equalizing currents via cable shield
7
Ground potential difference
8
Grounding point 1
If these conditions are not fulfilled, equipotential bonding currents can flow along the
cable shielding between the devices due to differing ground potentials; this can be dan‐
gerous. This is, for example, possible in cases where there are devices within a widely
distributed system covering several buildings.
Remedial measures
The most common solution to prevent potential equalization currents on cable shields
is to ensure low-impedance and current-carrying equipotential bonding. If this is not
possible, the following solution approaches serve as a suggestion.
NOTICE
We expressly advise against opening up the cable shields. This would mean that the
EMC limit values can no longer be complied with and that the safe operation of the
device data interfaces can no longer be guaranteed.
Measures for widely distributed system installations
On widely distributed system installations with correspondingly large potential differen‐
ces, the setting up of local islands and connecting them using commercially available
electro-optical signal isolators
is recommended. This measure achieves a high degree
of resistance to electromagnetic interference while at the same time complying with all
the requirements of EN 60950-1.
6
ELECTRICAL INSTALLATION
28
O P E R A T I N G I N S T R U C T I O N S | CLV61x Dual Port (PROFINET)
8017842/ZMG5/2017-06-12 | 8M_DR | SICK
Subject to change without notice