Stray Current Interference 6:3
CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
Identification of Stray Current
Dynamic Stray Current
Measurement Indications
Dynamic stray currents are manifested by fluctuations in structure-to-
electrolyte potentials and, on pipelines, by variations in line current flow. If
you encounter such fluctuations, you should suspect the presence of stray
current. Additional testing is required to determine the extent of the
fluctuations and the source of the stray current.
To determine the extent of the fluctuations, you need a recording
instrument such as a strip chart recorder or datalogger. These instruments
store or display the measurements over the test period so that the stray
current activity can be evaluated. Figure 6.1 shows a typical recording of
potentials produced by dynamic stray current.
POTENTIAL
TEST POINT
Figure 6.1 Recording of Dynamic Stray Currents
Proximity of Possible Sources
Even before you encounter fluctuating measurements, you may suspect that
you are working in a stray current area. The presence of any of the sources
listed above should lead you to suspect that you might encounter dynamic
stray current.
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