
2-17
SIMATIC 545/555/575 System Manual
Pre-installation Guidelines
2.8 Grounding the Power System
!
WARNING
A good grounding system is essential for proper operation of the system. It is
one of the most important considerations in planning your installation.
Failure to provide a good grounding system could lead to erratic operation of
the equipment, which could result in death or serious injury to personnel,
and/or damage to equipment.
Ensure that you have a good grounding system when you install your
equipment.
In some installations, a metal conduit that connects to the neutral phase at
the circuit-breaker box supplies the earth ground of the power receptacle.
Depending on site conditions, this metal conduit could conduct current from
other sources that can interfere with the operation of the equipment.
To reduce this possibility, isolate earth ground and neutral from the conduit
(except at the service entrance housing); see Figure 2-11. Ensure that
system power is wired in accordance with NEMA specifications. Also comply
with the following:
• Ensure that the protective ground wire resistance is less than 0.1 ohm.
• Ensure that the resistance to earth ground is 0.1 ohm or less.
Conduit Conduit
Protective
ground
Circuit
breaker
panel
Base
power supply
AC line
AC neutral
Ground
Service
entrance
Power
company
transformer
Power
company
earth ground
Earth
ground rod
Figure 2-11 Isolating Ground and Neutral From Conduit
Earth Ground
Comentarios a estos manuales