Is PROFIBUS grounding possible, you ask? PROFIBUS International (PI) claims that omitting the ground wires makes handling the cables easier. However, the association does suggest isolating the interface circuit from the local ground for safety, which may make that handling a little more difficult. Your mileage may vary, as always.
So, PI offers a document with all its recommendations for installing, grounding and shielding its cables. So you should refer to it when you have a question about PROFIBUS installation. You can also contact PROFIBUS suppliers to talk to their experts about your projects and network auditions.
The following links have more about PROFIBUS:
Other resources that might interest you
PROFIBUS PA and PROFIBUS DP
Does PROFIBUS PA have advantages? Can you implement every device in the PROFIBUS DP network?
PROFIBUS Class 1 and Class 2 masters!
Is there a difference between a Class 1 and a Class 2 master on a PROFIBUS network?