10106 Copper Grounding System Corrosion Due to DC Interference, Use of CP to Solve the Situation

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Product Number: 51300-10106-SG

ISBN: 10106 2010 CP

Author: Rogelio de las Casas

Publication Date: 2010

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An electrical substation copper grounding system has suffered from a severe corrosion due to the presence of direct stray current, originated from an aluminum plant. A study was done to demonstrate the presence of dynamic direct stray current as the cause of the corrosion of the copper grounding system.

To mitigate the influence of the stray direct current over the copper grounding system and to facilitate the application of cathodic protection, the electrical substation grounding mat was first disconnected from the aluminum plant grounding mat and then reconnected through polarization cell replacement (PCR) devices. Since the stray direct current could not be interrupted to measure structure to soil true potentials, four different types of IR drop free test stations were designed and installed.

To protect the substation grounding mat from corrosion, three impressed current cathodic protection (ICCP) systems with distributed anodes were installed and adjusted. In order to ensure the copper grounding system was protected, a cathodic polarization potential criterion of at least -300 mV with respect to a Cu/CuSO4 (CSE) was used.

Keywords: DC interference, cathodic protection, copper grounding system, distributed anode system, copper grounding system cathodic protection, stray direct current, and stray current corrosion.