Fluctuation Characteristics of Pipe-to-Soil Potential under Dynamic Stray Current Interference

196 sets of data on pipe-to-soil potential of pipeline under dynamic stray current interference caused by metro, high-speed railway and high voltage direct current (HVDC) transmission system grounding bipolar operation were obtained through field monitoring. The dynamic fluctuation characteristics of pipe-to-soil potential under different interference were analyzed in time domain first, and then in frequency domain by means of continuous wavelet transform (CWT). The periodic distribution ranges of pipe-to-soil potential under different interference were calculated, and the difference of their periodic distribution was compared. The results show that the three interference sources all caused dynamic DC interference to the pipeline. The interference from metro and high-speed railway presented a periodic change of serious during the day and the stable at night, while the interference from HVDC was related to the intensity and direction of the current from grounding electrode in high-voltage transmission line and had no obvious difference between day and night. The AC interference of high-speed railway was accompanied by significant DC interference. The period proportion of metro DC interference increased first and then decreased with the increase of the period. The period distribution of interference to pipeline changed with high-speed railway line, but it was mainly in the range of greater than 500 s. The potential fluctuation period of pipe-to-soil DC caused by HVDC interference was evenly distributed.