直流杂散电流对天然气管道干扰影响案例分析

Case Study on Interference Effect of DC Stray Currents on Natural Gas Pipelines

采用试片断电法和电位监测系统,对广东地区的某天然气管道进行24h的通/断电电位检测和长期监测,发现管道存在明显的直流杂散电流干扰。电位检测和监测结果分析表明:广东地区的天然气管道同时存在高压直流输电系统不平衡电流、单极大地回路电流和地铁杂散电流干扰;管段由于直流杂散电流的干扰,造成阀室内绝缘卡套放电烧蚀、恒电位仪内部元器件烧毁、恒电位仪无法正常运行以及全线管道的不同位置均有管体腐蚀发生。管体腐蚀最严重的位置腐蚀深度已经达到3.69mm,此位置管道在高压直流接地极输电系统单极大地运行模式时受干扰严重管道电位能达到-174.6V。同时,由于高压直流输电系统的不平衡电流和地铁杂散电流的叠加干扰,造成管道长时间处于欠保护状态,多个因素共同作用综合造成此段管道腐蚀严重。

Using test piece power-off method and potential monitoring system,24 hon/off potential detection and long-term monitoring of a natural gas pipeline in Guangdong area were carried out,and it was found that there was obvious direct current（DC）stray current interference in the pipeline.The potential detection and monitoring results show that the natural gas pipelines in Guangdong had unbalanced current,single-maximal loop current and subway stray current interference.Due to the interference of DC stray current,the tube segment was ablated,the internal components of potentiostat were burned out,the potentiostat could not operate normally,and the tube corrosion occurred at different positions of the pipeline.The corrosion depth of the pipe with the most serious corrosion reached 3.69 mm.In this position,the pipe was disturbed by the pipeline in the single-maximum operation mode of highvoltage direct current（HVDC）grounding transmission system,and the pipeline potential could reach -174.6 V.At the same time,due to the superimposed interference of the unbalanced current of HVDC transmission system and the stray current of subway,the pipeline was in an under-protected state for a long time,and the combination of several factors caused the corrosion of this section of the pipeline to be severe.