Definition - What does Long-Line Current mean?
Long-line current is a type of current that flows throughout the ground from a cathodic or anodic spot and goes back along pipelines (or other types of metal structures) below the ground. Most of the time, the current travels an extensive distance, as brought about by cell action concentration.
It is similar to stray currents. The only difference is that it occurs at extensive distances from the source of electric current.
Corrosionpedia explains Long-Line Current
Stray current that is commonly found in electric railways and other structures is one of the major causes of high corrosion rates in underground pipelines.
Long-line currents possess characteristics that are similar to stray currents. However, these currents occur at extended distances from probable electric current external sources. They are expected to appear between the pipe and the soil. Frequently, these currents follow the direction of the pipe, sometimes even for miles, with no amperage change.
Proper measurement of long-line currents can help in the determination of its influence in the rate of mechanism of corrosion. One method of measuring long-line current is to measure its value in an oil line where corrosion has occurred. Once the line has been removed, the degree of corrosion can be identified merely by inspection.