Estimating harmful effect of dynamic stray currents on pipeline by simultaneous multiparametric field measurements, continuous wavelet cross‐correlation analysis, and frequency plots
This paper presents the detection method and analysis methodology of dynamic stray current effects on underground pipelines based on simultaneous multiparametric measurements in combination with continuous wavelet cross‐correlation and frequency plots. Measurements presented within this paper were conducted at two locations experiencing tram induced dynamic stray currents, in the first case, on unprotected pipeline and in the second case, on pipeline under cathodic protection. On both pipelines, measurements of pipe‐to‐soil potential, lateral potential gradient, corrosion probe current, and pipeline current were simultaneously done for time period of 20 min. For both locations, the two wavelet cross‐correlation spectrograms for the quantities: lateral potential gradient and probe current versus pipe‐to‐soil potential show that 5% statistical significance levels are in periods between 16 and 128 s. Time spans and period lengths of observed cross‐correlations on spectrograms reflect the stray current influence that may be linked to specific events, such as passing of trams. On the other hand, frequency plots of the measured quantities give clear visual representation of the time that pipeline spends in a certain state related to the possible harmful effect of stray current and also show the degree of cathodic protection beneficial effect.