Grounding Copper Conductor size check

[ashish.rao]

Hello All,

I am approaching you experts, asking the methodology for determining the thickness or corrosion allowance of copper conductor being used in a plant electrical grounding system. As a corrosion engineer after the grounding design team decides on the minimum conductor size (units in MCM) if I am asked to determine if the same is sufficient with respect to corrosion allowance how do I determine?
Currently we ask for the Geotechnical report which would contain the Soil resistivity, soil moisture percent, chloride levels, sulphate levels etc and compare the same with research papers such as that of Romanoff to determine corrosion rate in similar soil parameters. This corrosion rate is used to further calculate max corrosion loss in Kcmil.
This method is not very effective as it just gives a rough estimate and usually the exact soil type would not match and the corrosion rate considered is usually assumed. Is there a different method to determine the same?

 

[cap1a79]

Is it insulated as a barrier between soil and the metal? If yes, have you considered regular check-up for the insulation integrity rather than adding corrosion allowance?
It would be much easier to check regularly and replace it once lifetime of the insulation is used up. (ex. every 10 to 15 years)

Lee SiHyoung,
WorleyParsons Oman Engineering,