Re: Size of concrete encased electrode
Since the grounding electrode system is primarily used for limiting voltages imposed by lightning, consider what is basically happening during the lightning event.
Lightning is a constant current source. No matter what the total impedance of the grounding system is, that current is the exact current that will flow through effected circuit(s). The impedance of these paths will indicate the potential imposed voltage on the conductors and equipment.
The typical lightning flash has a return stroke around 30KA. Be aware that it can be as high as 400KA. Using 30KA, if the grounding system resistance is at the magical 25-ohms, the imposed voltage will be 750,000-volts. If the the resistance is 200-ohms, the imposed voltage would be 6 million volts.
Based on this, it would appear that the better your GE system is, the lower the voltage that will be imposed on the system, and therefor that is a good thing. However, it is again bonding the makes this whole situation insignifcant. If all the systems (limited energy) and non-current carrying parts are bonded together effectively, there will be no ill-effects of this transient voltage. It bascially becomes a "bird on a wire" condition. There will be no potential between any equipment or conductors, save any weird inductive and capacitive effects of conductors in metal enclosures and insulation on conductors.
The whole system raises to the high energy state and then collapses back down to normal. Equipment not properly bonded or metallic parts near lightning energized parts may become damaged from potential flash over.