Perhaps a silly question, but:
A detached structure usually requires grounding electrodes. These grounding electrodes need to be connected to the equipment grounding and bonding system in the detached structure. But do these grounding electrodes need to be connected _directly_ to, eg, the ground bus in the panel or whatever serves as such?
I've been pondering the issue of ground currents caused by nearby lightning strikes, and thinking about the current carried by the egc between two structures if they both have their own ground electrodes. I wonder if it would be better to have a grounding electrode system that spans the entire property, connected to the equipment grounding system at one location only. At the detached structure you would have grounding electrodes or a ground ring, but connected back to the main structure by a heavy GEC. Then the detached structure would be grounded by the EGC that comes with the feeder. This EGC might be oversized to meet the requirements for GECs, and there would be grounding electrodes right in the vicinity of the detached structure. Its just that the connection would be indirect.
In this way, the EGC would become something of an 'isolated ground', and not carry currents between grounding electrodes. Instead any earth currents coupled to the electrodes would be carried by the heavy GEC.
Just a meandering mind