Current through paths other than the intended circuit is called stray current. Most frequently stray currents arising from DC train, AC power lines and foreign CP systems. Static CP survey is used to detect these dangerous interferences.
All cathodic protection systems make currents flow through the electrolyte in order to achieve a certain protection level on the protected structure. These currents may cause earth current corrosion in the foreign structures. This is called interference from cathodic protection systems.
Important discriminating the effect of different potential fields like, stray current, foreign CP and coating defect potential gradient.