Sparky,
My fault. The answer to Cindys question is: There is no time you need to have more than a # 6 conductor to a ground rod. My fault for going into an explanation that is way to lengthy for a quickie forum answer.

Lemme try one more time to amend my error.

The purpose of OUR (meaning low voltage, supply side electricians) designed intent of the Grounding Electrode System is to prevent any potential difference between electrical equipment and the earth upon which we are standing. No more than that. The circuit you speak of, in this case, is the equipment, your hand - through your body to your feet to anything metallic to earth (whether this path is through your water heater, insta-hots, or any plumbing/electrical connection) back into the electrical equipment. If they are not 'equalized' through a ground connection any inductive effects which you would have because it's AC, would be felt, and potentially deady.

Which is why there is never more than a #6 required to a ground rod. If you use larger than a #6, you create a choke coil, actually slowing down the process through capacitance. So why does the utility often use larger than a #6 ?

The UTILITY cannot afford low impedance/reluctance to earth on the line side or a near strike (remember NOTHING survives a direct strike) would be completely dissipated in one spot, destroying equipment. They 'spread' out the strike over several miles of line and arrestors and 'ease' the strike out. That is why you design 2/0 connections to ground rods at transformers, #2 to ground rods at poles, etc.. All this depends upon several things, length of circuit, voltage, # of transformers, # of reclosers, # of arrestors, etc.. It is complicated and # of recorded strikes, lineman callouts in storms, storm days, etc, go into your design and consideration. None of this goes into the low voltage design criteria.

Our design does allow, as it should, the occasional "drain" (if you will) of overvoltage, but only when the utiity system has failed or been overwhelmed, which does happen. My fault (or problem) for getting a bit 'ticked' at hearing that the design intent of our system is for lightning dissipation.

See why the ground rod (or whatever electrode you care to use) at a 2nd building fed from the same service is there ? Not to prevent, or dissipate lightning, but to eliminate potential difference between the earth upon which you are standing, and the electrical equipment you are using. The dissipation, removal (drain) of inductive influences is a secondary benefit, not a designed benefit. The earth is simply not a good enough conductor to be relied upon for this task is is is separated from the primary structure by any distance at all.

One example, and I'll quit. Installing a service at a convenience store that had burned down (arson). A utility transformer at the rear of the store was 'leaking'. My galvanometer told me we had 5 volts seeping into the ground from the xfrmr. I told the utlility, who really didn't care (they did a month later when the leaking feeder blew). Refrigeration equipment at the rear of the store was bonded to my service and sitting on fiberglass pads. I measured, on dry ground, a potential difference of the full 5 volts between the ground and the correctly grounded equipment. What could be the consequences of walking away ? How about an A/C service man servicing equipment after an thunderstorm, or snow, or rain ? Will he feel that 5 volts given that he is probably wet, kneeling beside the equipment ? you bet he would. Cure ? Drive a ground rod at the equipment (You can supplement your system anywhere you like, and that is why) and eliminate the potential difference.

There is no requirement to use arrestors on our equipment which would mean we design for lightning dissipation, and there ain't gonna be that requirement, because that portion of grounding has to be considered BEFORE it ever enters the structure, as it should be.

Ok, we've 'bout beat this puppy to death, thanks for listening, and I apologize to all for beginning a very detailed analysis in a forum when I should not have. Mostly because I've still only covered the bare tip of a VERY large iceberg, and one which is difficult enough to understand without half an explanation.