Use of FFT Method for the Detection and Characterization of a Pipeline’s AC Stray Current Interference

Keywords: AC corrosion, pipeline, FFT (fast fourier transform) data signal proecssing, stray current 

Use FFT (Fast Fourier Transform) data signal processing method for the detection and characterization of oil & gas pipeline's alternating voltage stray current interference. The results showed that this method is capable of distinguishing power frequency AC (alternating current) stray current interference from the dynamic DC (direct current) stray current of the pipeline. It can easily pick-up the DC part and AC part of specified frequency. The experiments carried out in laboratory and field showed that the result gained by FFT method is the same as that by conventional instruments, which is designed of analog filter circuit. And the carbon steel work electrodes under cathodic and anodic polarization  experiments showed that the polarization potential change toward the natural corrosion potential with the increase of AC current applied on the work electrode, but the carbon steel electrode under natural corrosion showed its potential change toward more active direction . All the above showed that the FFT method is an ideal tool for the detection and characterization of the buried pipeline's AC stray current.