Kai:
we are a little off topic but it is sunday so here goes
In above 400 amp systems the ground loop current problem is taken very seriously. To the point that the connector bushings are mounted into the box in a specific order,the steel enclosure is cut between the holes to prevent circulating currents melting the enclosure. The wires in them are cut to exact length for current balancing to reduce these effects.
I have personaly repaired several generator instalations that were damaged from ground loop faults. These faults manifest most often during spring thaw as the exposed ground saturated and changed the ground resistance balance between protected ground and exposed ground.

For new generator instalations I take extreme care to provide a very positive ground then run all grounds back to that point (common ground node).
For back up generator installations I put a chart recorder on the ground system and get at least a weeks worth of data to confirm ground quality before I start an instalation. If I see problems they must be corrected before I will install a unit because I can not warantie an instalation otherwise.

All that said we are talking mega watts vs microwatts and obviously the effects and results of ground loops will be different in both cases.

As a final note one difference in trouble shooting is that on large power systems your first clue to what went wrong is often "the dam thing is missing" for example the guts of the switch are vaporized , or 40 feet of 500 mcm( about 3 cm in diameter) ground wire is gone. and yes I have seen both happen. Terry