CP for Copper Ground Grid

[Kiribanda]

Gentlemen,

As far as I understand (please correct me if I am wrong),
the protective levels required for the following underground structures protected by an Impressed current system are,
1) Steel = -0.85 V dc
2) Copper = -0.20 V dc
with respect to a Cu/ CUSO4 half cell.

Now if we bond an underground copper ground grid to an underground steel line already protected by an impressed current system,definitely the electrical loading on the rectifier will increase.

Question: How can we resonably estimate the percentage increase in electrical loading on the existing impressed current system due to such type of bonding?

Kiri

 

[SJones]

By looking at Materials Performance, August 2002, pages 22 to 25

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[Kiribanda]

SJones,

Thanks for the reply.

Since I am an electrical guy I donot subscribe to the the magazine you have mentioned. Could you please post the pages 22-25 in here in pdf to download?

Kiri

 

[SJones]

Kiri,

I have the pages but I'm pretty sure that copyright law will prevent me from posting them anywhere. The essence of this paper is that, if one simply must incorporate copper earthing into a cathodically protected system, then one should really perform accurate earthing calculations to get the amount of copper down to the absolute bare (excuse the pun) minimum. Even when that has been done, the author found the need to increase transformer/rectifier and groundbed capacity by 167% in that particular case.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/