Siemens S5-155U System Manual page 45

Wiring of Programmable Controllers for EMC
3.3.2
Equipotential Bonding
3 - 16
Between separate sections of an installation, potential differences can
develop if
• • programmable controllers and I/O devices are connected via a
non-floating link, or
• • cable shields are connected at both ends and are grounded at
different parts of the system.
Different AC supplies, for example, can cause potential differences.
These differences must be reduced by installing equipotential bonding
conductors to ensure functioning of the electronic components.
The following points must be observed for equipotential bonding:
• • The lower the impedance of the equipotential bonding conductor,
the greater is the effectiveness of equipotential bonding.
• • Where shielded signal lines are laid between the relevant sections
of the system and connected at both ends to the ground/protective
conductor, the impedance of the additional equipotential bonding
conductor must not exceed 10 % of the shield impedance.
• • The cross-section of the equipotential bonding conductor must be
rated for the maximum circulating current. The following
cross-sections of copper have proved to be satisfactory in practice:
2
- 16 m of copper for equipotential bonding conductors of up to
200 m in length
2
- 25 m of copper for equipotential bonding conductors of more
than 200 m in length
• • Use copper or zinc-plated steel for equipotential bonding
conductors. They must be given a large-area connection to the
ground/protective conductor and protect it from corrosion.
• • The equipotential bonding conductor should be laid so that the
smallest possible areas are enclosed between the equipotential
bonding conductor and signal lines.
Equipotential Bonding Conductor
Figure 3-4 Routing of Equipotential Bonding Conductor and Signal Line
Signal Line
System Manual
C79000-B8576-C199-03