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.