Case Analysis of Natural Gas Pipeline Interfered by Strong Subway Stray Current

A natural gas pipeline was interfered by strong stray current. The degree of interference to pipeline was evaluated by potential monitoring, the law of stray current inflow and outflow was analyzed, and the interference zone was determined. The effect of increasing cathodic protection current on suppressing positive potential shift was studied by feeding test. The results show that the pipeline was interfered by strong DC stray current from subway. The pipe sections at both ends of the pipeline were the inflow and outflow areas of DC stray current for each other, and the middle section of the pipeline and the two ends of the pipeline were the inflow and outflow areas of DC stray current for each other. Cathodic protection current could effectively suppress the positive deviation of pipeline potential, but the suppression range (length) was limited. The problem of dynamic DC stray current interference from subway to pipeline requires the cooperation of the subway party and the pipeline party.