2.6.4 Connecting the shielding with the equipotential bonding
The shield is a necessary part of the PROFIBUS copper cable. It shields the two data cores in the cables against electrostatic interference. For the shielding to be effective, it must be connected to the equipotential bonding system. Ungrounded shielding has no effect whatsoever. The PROFIBUS copper cable shield must be connected with the equipotential bonding system at the following points:
At the PROFIBUS station
Connect the PROFIBUS cable shield to the equipotential bonding at every PROFIBUS station.
The PROFIBUS connector, where used, provides connection for the cable shield. However, this requires a properly made the shield connection in the connector. Additional information about the connector assembly can be found in chapter 2.2.
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PROFIBUS stations with direct PROFIBUS cable connection generally also offer an option for connecting the cable shield with the equipotential bonding. If the PROFIBUS cable is correctly assembled, no additional connection of the PROFIBUS cable shield is required. Additional information about the direct connection of PROFIBUS stations can be found in chapter 2.3.
If no shield connection exists, the shielding of the PROFIBUS cable must be connected to the equipotential bonding as close as possible to the PROFIBUS station. Additional information about establishing the connection between shielding and equipotential bonding can be found in chapter 2.6.5.
If the PROFIBUS station features a ground terminal, it must also be connected with the equipotential bonding.
Connect the mounting bracket (e.g. mounting rails) with the equipotential bonding system. For some PROFIBUS stations, the connection between shielding and equipotential bonding is established via the mounting screws.
At the cabinet entry
Connect the PROFIBUS cable shield to the equipotential bonding at the entry point to a control cabinet. The connection should use a large surface area. This prevents any outside interference picked up on the PROFIBUS cable from being transmitted into the cabinet.
For this purpose, attach an equipotential bonding rail at the cabinet entry behind the cable strain relief.
Methods of connecting the cable shield to the equipotential bonding are described in chapter 2.6.5.
At the building entry
Connect the shield of the PROFIBUS cable directly with the equipotential bonding system at the building entry point. The connection should have a large surface area to provide minimum resistance.
For this purpose, attach an equipotential bonding rail at the building entry.
Additional information about establishing the connection between shielding and equipotential bonding can be found in chapter 2.6.5.
