Hello,

I've a tanker truck with sinamics g120x, plc s7-1200 1214 dc/dc/dc and one hmi.

Some times and in different customers the drive faults with 7800 and 8526 alarms.

I've read the manual.

Can this errors be in the ground circuit?

Can I do something?

you can see the error in the attached photo.

Due your description I assume you may have a EMC problem.
See this FAQ:  https://support.industry.siemens.com/cs/ww/en/view/60612658

1. Ground all components in HF relevant way 
2. Separate the motor cables from other cables.

My hints:

• Make sure the G120X and all other components are correctly grounded. The plate the G120X is mounted should be grounded too, if possible the motor too. Use short and not to thin grounding cables. Use as much contact area as possible. Small cables in terminal are insuffizient.
• The cables of the G120X to the motor should be separated from other cables.

Read the chapters 4.1 and 12.9 (PDF file) of the G120X manual:  https://support.industry.siemens.com/cs/ww/en/view/109776312 

I can't know the grounding of the customers, and the qüestion is, if I remove the screw for functional grounding the problem finish.

thanks.

I've fixed 8526 via TIAPortal: Online & Diagnostic => Assign Profinet Name (to sinamics g120x drive).

After this, i've recompiled my CPU (hw and sw "rebuild all"). 

After i've downloaded my project to CPU (with start/stop CPU) - and it helps to me.