I would like to know the reasons why the EVAL-ADE9000-Shield has isolated the grounds of the part where the signals are acquired and the part where the microcontroller is connected.
1) Does this only work as a protection mechanism for the microcontroller?
2) Is there any other advantage? Maybe the noise decreases? improve accuracy? etc.
The ground of the ADE9000 is referenced to the Neutral Line of the Power line. The ground of your micro controller is different. So it needs to be completely isolated system. If you do not put islation then you are grounding your microcontroller to the neutral reference, and it is as if you connect the ground to the other systems connected to the neutral (etc motors, etc). So to answer your questions:
1. Not only for protection but for complete isolation of the system.
2. Advantage in functionality and performance.
Please do not remove this second level of isolation (1st level is the isolation of the phases thru the use of CT).