油气管道受直流杂散电流影响规律及防护措施研究

Research on rule and protection measures of oil and gas pipelines affected by DC stray current influence

为降低高压直流输电线路在接地极放电时引发的杂散电流干扰,降低管道腐蚀速率和失效率。利用电位远程监测系统,采用断电试片法监测管道的通、断电电位,得到不同放电类型下的干扰规律,并针对管道分段绝缘和敷设锌带两种缓解措施进行效果评价。结果表明,高压直流接地极每年的干扰频次、时长远超过标准要求;越靠近接地极,管道电位的偏移量越大,阳极放电时远离接地极的管段为杂散电流流出段,阴极放电时靠近接地极的管段为杂散电流流出段,此时管道存在腐蚀风险;分段绝缘可有效降低管道中点处的电位差,敷设锌带可在局部范围内降低泄露电流密度;采用双重防护措施后,风险减缓幅度比任何一种防护措施都大;防护措施实施后,可节约管道更换里程,减少天然气泄露量,年可节约运行成本105万元~259万元。研究结果可为直流接地极和油气管道之间的腐蚀防护设计提供实际参考。

In order to reduce the stray current interference caused by the grounding electrode discharge of high voltage direct current transmission lines,the corrosion rate and failure rate of pipelines are reduced.The potential remote monitoring system is used to monitor the on-off potential and offoff potential of the pipeline by using the power off test piece method,and the interference rule under different discharge types is obtained.What's more,the effects of two mitigation measures,segmental insulation and laying zinc strip,are evaluated.The results show that the annual interference frequency and time of high voltage direct current grounding electrode exceed the standard requirement.The closer to the grounding electrode,the greater the potential offset of the pipeline.When the anode is discharged,the pipe segment that is far away from the grounding electrode is the stray current outflow section.When the cathode is discharged,the pipe segment that is close to the grounding electrode is the stray current outflow section.there is a risk of pipeline corrosion at this point.The segmental insulation can effectively reduce the potential difference at the middle point of the pipeline,and the zinc strip can reduce the leakage current density in a local scope.After the use of dual protective measures,the risk reduction is greater than any other protective measures.After the implementation of protective measures,it can be saved the mileage of pipeline replacement and reduced the amount of natural gas leakage,saving the operation cost of 1.05 million yuan~2.59 million yuan every year.The research results can provide practical reference for corrosion protection design between DC grounding pole and oil and gas pipeline.