Cindy:
I can't answer the specific question as to the NEC's intentions relative to ground rings.
Is there a distinction made between a ground ring used for the grounding electrode and a ground ring used for situations where lightning-protection is required (towers...)?
If I understand correctly, any "extra" grounding systems (lightning, radio transmission, etc.) need to be tied in with the electric system anyhow.
P. S. Here are some links I found:
http://www.psihq.com/iread/ufergrnd.htm http://www.cpccorp.com/deep.htm
