Testing and Evaluation of Pipeline Cathodic Protection Potentials Affected by Subway DC Interference

In order to study the interference distance and severity of subway DC interference on pipeline cathodic protection, a special investigation was conducted using coupon test and data logger. Long term on/off potentials of pipeline were also monitored . The results showed that severe DC stray current interference was found at 0-64 km pipeline section with insulation connectors on both sides. Drainage measures should be taken as the trend of positive excursion of polarized potential at daytime exceeded the threshold of related standard. The other section at 64-130 km after insulation connector also suffered mild DC stray current interference, but not servere enough to take measures.