Effects Of AC/DC Stray Currents On Pipeline Systems

With the rapid development of electricity power,communication,track traffic and green energy,pipelines are booming.Due to the space limitation and similar route selection principles,different routes may be crossed or paralleled in some areas.That is why stray current interferences become more serious than before,and traditional cathodic protection techniques are no longer satisfied with the need of integrity management.Therefore,investigations on influences of stray current interferences on pipelines are significant to their safety operations.The discharge data of high voltage direct current grounding-electrodes along the pipeline,alarm information of pipeline protection systems and relevant accidents are collected.The influences of high voltage direct current grounding-electrodes are analyzed,and the risks of damages to various instruments are summed up.Four typical pipeline sections are selected to analyze the applicability of AC inference criterion with calculation or field measurement methods,which are the most commonly used in the engineering.Differences between measured and calculated current densities in various soil surroundings with different moistures are investigated.The results show that the differences become greater as the soil moistures increases and corrosions become more serious,and that AC inference criterion with the calculation method from the standard doesn't work.Finite element software ANSYS is used to simulate a model of coupon method to investigate effects of acting time,voltage and other typical factors on stray current densities.Simulation results demonstrate good agreements with measured values.Conclusions are drawn that DC interference shows greater impact than AC inference.Direct current density remains constant over time,but alternative current density rises over time.In combination of field test and simulation,Impacts of stray current interferences on pipelines are shown,and amendment of current interference criterion in the standard is proposed to help pipeline professionals get closer to the truth of the stray current corrosion and take effective measures timely.