考虑土壤散流的电力线路邻近处油气管道雷击过电压防护

Lightning overvoltage protection for oil and gas pipelines adjacent to power lines with consideration for current dispersion in soil

【目的】目前油气管道与电力线路交叉邻近的工况愈发多见,“两线一地”交叉互邻情况下的雷击过电压问题引起了相关行业的高度关注。【方法】针对电力线路邻近处的油气管道雷击过电压防护问题,采用COMSOL Multiphysics软件建立油气管道与电力线路“两线一地”交叉互邻情况下的雷击过电压计算模型,阐明管道本体电位及防腐层耐受电位差的产生机理;通过仿真计算分析了土壤电阻率与分层结构对管道过电压的影响规律,并提出了考虑杆塔接地网散流作用下的管道过电压防护方法。【结果】通过仿真算例验证了该优化改造方案的管道限压效果并论证了其工程应用价值,管道本体电位以及防腐层的耐受电位差受接地体散流方向影响较大,二者整体呈现出两侧对称分布形态。典型土壤电阻率条件下管道防腐层的耐受电位差不超过极限值,单次雷击放电不足以击穿管道外侧3PE防腐层。当防腐层存在局部破损点时,耐受电位差会增大防腐层破损面积。通过改变管道与杆塔接地体之间的夹角和相对距离,能够有效降低管道本体电位与防腐层耐受电位差。【结论】通过改变管道邻近杆塔接地网的结构与散流维度,可有效降低管道电位及防腐层耐受电位差,其可实施性和技术经济性高,研究成果可为油气管道的设计、施工及安全运维提供参考。

[Objective]In light of a growing number of oil and gas pipelines crossing or running near power lines,the issue of lightning overvoltage at these locations has garnered increasing attention within these two industries.[Methods]In this study,a calculation model was developed using COMSOL Multiphysics software to depict the generation mechanism of potential difference between pipelines and their anticorrosive coatings at locations where these pipelines cross or run near power lines.Simulation calculations were performed to analyze the impact of soil resistivity and soil layering on pipeline overvoltage amplitude.As a result,a pipeline overvoltage protection method was proposed,considering the dispersion of current over the grounding grids at nearby towers/poles.[Results]The simulation results confirmed the effectiveness of the proposed optimization solution in limiting the voltage,establishing its practical application value.Although the potential on the pipelines and the withstand voltage of their anticorrosive coatings were generally balanced,the difference between them was notably influenced by the direction of current dispersion from the grounding electrodes.Under typical soil resistivity conditions,the withstand voltage difference between the pipelines and their anticorrosive coatings remained within limits.Additionally,it was observed that individual lightning discharges alone were insufficient to cause breakdown in the three-layer polyethylene(3PE)anticorrosive coatings.However,the withstand potential difference did contribute to the enlargement of local damage points that already existed within the coatings.To mitigate the withstand potential difference,an effective approach is proposed involving adjustments to the included angle and relative distance between the pipelines and grounding electrodes at nearby towers/poles.[Conclusion]It is proposed to effectively reduce the potential difference between pipelines and their anticorrosive coatings by modifying the configuration and current dispersion dimensions of the grounding grids at nearby towers/poles.With proven technical feasibility and economical efficiency,the findings of this study serve as a valuable reference for the design,construction,safe operation,and maintenance of oil and gas pipelines.