Buried Earthing Grid in Concrete Foundations - German Philosophy

J

Joao

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portugal
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engineer
Attached file with some photos of buried earthing grid inside concrete foundations.

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  • Rede de terras no betão.pdf
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See: BS 7430:2011
9.5.8.5 Structural steelwork
 
jaggedben said:
Just looks like the normal reinforcement, not purposefully for earthing.
Click to expand...
5.4.4 Natural earth electrodes
Interconnected reinforcing steel in concrete foundations in accordance with 5.6, or other
suitable underground metal structures, should preferably be used as an earth electrode.
When the metallic reinforcement in concrete is used as an earth electrode, special care shall
be exercised at the interconnections to prevent mechanical splitting of the concrete.
 
Joao said:
5.4.4 Natural earth electrodes
Interconnected reinforcing steel in concrete foundations in accordance with 5.6, or other
suitable underground metal structures, should preferably be used as an earth electrode.
When the metallic reinforcement in concrete is used as an earth electrode, special care shall
be exercised at the interconnections to prevent mechanical splitting of the concrete.
Click to expand...
What code are we quoting here? Is there a question? Agree that steel in concrete foundations makes a good grounding electrode.
 
EPRI did a research project to provide an initial evaluation of the impact of concrete blocks on substation safety and performance as well as recommendations for dealing with this issue. The study produced a number of important and useful recommendations.
A secondary objective is to bring these issues to the attention of industry groups involved with standards development, such as the Institute of Electrical and Electronics Engineers (IEEE) for possible incorporation into the standards as it is written in the article.
Results & Findings
The study showed that the presence of concrete blocks in the vicinity of a substation might generate increased touch and step voltages, especially in cases where concrete blocks are outside
the substation fence but close to it and are not bonded to the substation grounding system.
However, in cases where the concrete blocks are bonded to the substation grounding system, the effect was beneficial in most cases considered in this parametric study. In any case, only a small amount of fault current usually goes through the steel rebar. The performed parametric study was limited in scope and therefore does not capture all possibilities that may occur. For example, the study has not addressed the issue of lightning currents and what percentage of lightning current may flow in steel rebar bonded to the grounding system.
See:
EPRI
Effects of Steel Reinforced Concrete on
Grounding System Performance
 
Julius Right said:
EPRI did a research project to provide an initial evaluation of the impact of concrete blocks on substation safety and performance as well as recommendations for dealing with this issue. The study produced a number of important and useful recommendations.
A secondary objective is to bring these issues to the attention of industry groups involved with standards development, such as the Institute of Electrical and Electronics Engineers (IEEE) for possible incorporation into the standards as it is written in the article.
Results & Findings
The study showed that the presence of concrete blocks in the vicinity of a substation might generate increased touch and step voltages, especially in cases where concrete blocks are outside
the substation fence but close to it and are not bonded to the substation grounding system.
However, in cases where the concrete blocks are bonded to the substation grounding system, the effect was beneficial in most cases considered in this parametric study. In any case, only a small amount of fault current usually goes through the steel rebar. The performed parametric study was limited in scope and therefore does not capture all possibilities that may occur. For example, the study has not addressed the issue of lightning currents and what percentage of lightning current may flow in steel rebar bonded to the grounding system.
See:
EPRI
Effects of Steel Reinforced Concrete on
Grounding System Performance
Click to expand...
As per results if those concrete blocks are connected to main buried grid the impact was beneficial. Those connections are usually done inside substation.

Also is not usually use concrete blocks in vicinity of the substation. If needed to decrease touch and step voltages we can use an internal and ouside rings as per IEEE 80 case studies for grounding fences.

I do not see any problem.
 
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