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The better the equipotential bonding in a plant, the smaller the chance of interference due to
fluctuations in potential.
Equipotential bonding should not be confused with protective earthing of a plant. Protective
earthing prevents the occurrence of excessive contact voltages in the event of equipment
faults whereas equipotential bonding prevents the occurrence of differences in potential.
4 4 .10.6
Cable shielding
Signal cables must be shielded in order to prevent coupling of interference.
The best shielding is achieved by installing the cables in steel tubes. However, this is only
necessary if the signal cable is routed through an environment prone to particular
interference. It is usually adequate to use cables with braided shields. In either case,
however, correct connection is vital for effective shielding.
The following generally applies:
Figure 4-21
The shielding bus should be connected to the control cabinet enclosure in a manner allowing
good conductance (large-area contact) and must be situated as close as possible to the
cable inlet. The cable insulation must be removed and the cable clamped to the shielding
bus (high-frequency clamp) or secured using cable ties. Care should be taken to ensure that
the connection allows good conductance.
SIMATIC RF600
System Manual, 06/2019, J31069-D0171-U001-A22-7618
For analog signal cables, the shield has to be connected at one end on the receiver side
For digital signals, the shield has to be connected to the enclosure at both ends
Since interference signals are frequently within the HF range (> 10 kHz), a large-area HF-
proof shield contact is necessary
Cable shielding
4.10 Guidelines for electromagnetic compatibility (EMC)
RF600 system planning
103
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