Grounding Conductor Over Concrete

[EngAriz]

Hello,

Is it acceptabile to lay substation grounding mesh cupper conductor over a lean concrete of the foundation of cable trench in some places, knowing that the conductor will touch bars and there will be another layer of concrete over the conductor. Dose the cupper conductor get chemical interaction with the concrete or bars. There is suggestion to pull grounding conductor in such places through pvc sleevs of length 3.60 meters but I am afraid that this affect on discharging short circuit current.
We facing this situation as the contractor didn't pulled grounding conductor before making lean concrete of the cable trench.
Thanks

 

[tase2004]

Hello,

The fact that the conductor is touching the bars is not a problem. But usualy for grounding is not used copper, becouse it has a high cost, it is used NiZn conductors. But if you use copper i don´t know if it will interact with the concrete.

 

[jghrist]

There is no problem with the interaction of copper and concrete, but the problem may be ingress of water into the concrete. If you have stranded copper penetrating the concrete and touching the rebar, water may get to the rebar and cause corrosion of the rebar. See thread238-139366

It would be better to clamp the ground wire to the rebar, thereby using the reinforced concrete trench as an additional grounding electrode.

 

[7anoter4]

First of all you may use copper lead [or tin] covered conductor instead of bare stranded conductor. But, I think it is better to connect [outside the concrete] the rebar to the copper conductor and to use the concreted rebars as "Ufer Grounding" as jghrist proposed.

 

[cuky2000]

In my oppinion, water moisture may not be a signifcant negative impact to corrosion and grounding performance since the concrete is a gygroscopy material that extract and retain moisture from the surrounding soil. If
the corrosion in reinforced rebar Is a concern, additinal tickness or increase in rebar should be consider.

In several grounding fcilities, the concrete rebar and the semiconducting characteristics of the concrete was used to design an equipptential mesh taking advantageof the high moisture content in concrete and the conductivity of the steel rebar tied to copper loops. Ths arangement is safe, however test are recommende to verify that not be significant voltage difference between adjacent points to qualify the concrete slab as an equipptential surface.