When is a "ground ring" required?

[pkortesoja]

I'm a newbie and it may be obvious with this question, but I've been browsing NFPA 70 section 250 and NFPA 780 and many other references virtually all day and cannot find any statement of when a "ground ring" type of ground terminal is actually required (whether for the electrical system ground or a lightning protection ground). When and why is a "ground ring" required - and where in the code and/or related standards for system grounding and/or lightning protection is this explicitly stated?

 

[GoldDigger]

I'm a newbie and it may be obvious with this question, but I've been browsing NFPA 70 section 250 and NFPA 780 and many other references virtually all day and cannot find any statement of when a "ground ring" type of ground terminal is actually required (whether for the electrical system ground or a lightning protection ground). When and why is a "ground ring" required - and where in the code and/or related standards for system grounding and/or lightning protection is this explicitly stated?

A ground ring is one type of grounding electrode recognized by the NEC, and as such can be used in combination with other types of electrodes to meet the NEC requirement for a Ground Electrode System (GES).
It can provide a relatively low overall electrode resistance to remote earth (the standard reference point for ground voltage and impedance). It can also help to provide an equipotential region around the perimeter of a building or substation.
But where it is "needed" or desirable from a design standpoint is not addressed by the NEC and is subject of other standards and of contractual requirements.
Some design documents, for telecommunications, substations, and other specific usages, may require a ground ring. If you are designing such a facility you need to see what other industry (as distinct from regulatory) standards may apply. When constructing, the contract may specify a ground ring, since the code does not. When you are designing you need to make the determination whether to require a ground ring based on customer input or industry standards.

 

[infinity]

Part of the reason that they're not used very often is that they are required to encircle the entire building or structure. For a building it's likely easier to accomplish similar results by simply using a CEE instead.

 

[pkortesoja]

Part of the reason that they're not used very often is that they are required to encircle the entire building or structure. For a building it's likely easier to accomplish similar results by simply using a CEE instead.

Thanks a bunch! Very helpful. I assume "CEE" means Concrete Encased Electrode. No need for a reply if I've got that right. Thanks again.

 

[kwired]

The difference with the CEE though is if it is present, it must be used. A ground ring is totally optional, and normally wouldn't be present unless you intended to use one.

Ground rods are also totally optional - but are the most preferred method because of cost and simplicity when you must add an electrode where there is none or must supplement one where there is nothing else to supplement it with.

 

[petersonra]

I don't believe there's any enforceable code that ever requires a ground ring. There are occasions when it is a contractual requirement which is still a requirement.