Pipeline safety gas code in 49 CFR Part 192 requires that IR drop be considered when applying cathodic protection current. IR drop is the resistance of wires and soil between the measurement cell and the buried pipe. Voltage measurements must account for this IR drop or a protection standard like the 850 mv might not be sufficient to prevent corrosion.
For distribution systems with galvanic anodes, many times operators assume the IR drop is negligible because of the low voltage applied with a galvanic anode compared to a rectifier. This is indeed many times true but code still requires distribution operators to demonstrate that IR drop is negligible. I recommend you review your corrosion and cathodic protection plan to see if you have covered a periodic review to demonstrate that IR drop is negligible in your galvanic anode system.
If you don’t have a method to demonstrate that IR drop is negligible, I would be happy to help and teach you what I call the “Rizzo method” to accomplish this. It is straight forward and simple to do on a periodic basis.
This month’s special: $100 to cover: a) review of your IR drop section of your corrosion and cathodic protection plan, b) suggest edits RE periodic testing to determine if IR drop is negligible, and c) provide you instructions on the “Rizzo method” of determining whether IR drop is negligible.