ABB AC 800M, User Manual

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Special conditions regarding the installation of PROFIBUS DP Section 4 Commissioning of
96 3BDS009029R5001 B
Special conditions regarding the installation of
PROFIBUS DP
When using PROFIBUS - DP, also in intrinsically safe zones with remote I/O
modules, the following conditions regarding screening / earthing have to be
observed:
• Electrical grounding of the PROFIBUS cable screen on two points at the AC
800M control station:
– Connection at the 9-pole SUB-D plug on every device, for example
CI854(A), CI840, CI920, etc.
– Connection of the cable screen with a grounding clamp at the housing
entry.
• If the installation contains areas with high potential differences, a potential
equalization cable should be added to the data line when using an RS485
PROFIBUS cable . The potential equalization cable must have a minimum
cross-sectional area of 16 mm
2
and must be linked with the shield of each
node. This avoids compensation currents through the cable shield or data lines.
A more flexible solution is provided by fiber-optic cables.
• Additionally, another screen grounding is required at each cubicle entry in non-
intrinsically safe and intrinsically safe zones by a low impedance connection
over a large surface via cable clips. The screen must continue between all DP
devices (Master/slaves) connected to the PROFIBUS.
Remark: The requirement for multiple screen grounding results from:
– Requirement according to the PROFIBUS installation Guideline ("The
cable shield should be connected to ground at both ends of the cable.")
– The screen grounding of the bus cable on both sides is also possible in
hazardous locations if there are no compensating currents on the screen
which should be ensured in case of an optimum equipotential bonding
according to VDE 0165.
• Connection of all earthing points via continuous low impedance equipotential
bonding. In any case, it must be ensured that an adequate equipotential bonding
is existing during the whole life of the system. If an adequate equipotential
bonding cannot be ensured for the whole life of the system, an additional