Distance limitations for grounding electrode conductor (GEC)

[philly]

Does the NEC have any distance limitations for the length of GEC between the grounded conductor and the grounding electrode in a SDS?

We have a project where we are installing a temporary 2500kVA 12.47kV-480V transformer (system bonding jumper at transformer) and need to use an existing building grounding rod as the grounding electrode (no other grounding electrode options available) however the existing ground rod is located 80ft from the transformer location.

I do not see any distance limitations specified in 250.30(A)(5) for the grounding electrode conductor. I do see in 250.30( A)(4) that the grounding electrode should be as near as possible and preferably in same area as the GEC connection to the system which in this case would be the transformer. However there does not appear to be a specific limitation on distance.

Is anyone aware of a specific distance limitation here? I suspect the increased distance would have an effect on overall resistance to ground for the grounding connection between SDS and grounding electrode. I thought I saw somewhere that GEC sizes in 250.66 were based on an a study for GEC lengths of 100ft of less which any distance over 100ft requiring increasing size similar to VD size increase on CCC's?

 

[tom baker]

No distance limits in NEC

 

[mbrooke]

I'd be much more worried about an EGC than an GEC.

 

[infinity]

Is anyone aware of a specific distance limitation here? I suspect the increased distance would have an effect on overall resistance to ground for the grounding connection between SDS and grounding electrode.

The NEC doesn't really care about resistance to ground, or more specifically the resistance of the electrode (unless its a single rod). If you had two rods as the electrode and their resistance were 500 ohms it would still be code compliant. The more important component is a proper sized and installed system bonding jumper.

 

[don_resqcapt19]

...
Is anyone aware of a specific distance limitation here? I suspect the increased distance would have an effect on overall resistance to ground for the grounding connection between SDS and grounding electrode. I thought I saw somewhere that GEC sizes in 250.66 were based on an a study for GEC lengths of 100ft of less which any distance over 100ft requiring increasing size similar to VD size increase on CCC's?

Given the very high resistance of the grounding electrode as compared to that of the grounding electrode conductor, I don't see where it makes any real difference. The smallest permitted grounding electrode conductor has a resistance of less than one ohm per 1000 feet.