地磁暴引起的埋地管道管地电位“波节”和“纠缠”分布特征

磁暴在大地介质中感应生成地电场和地磁感应电流,进而导致长输埋地管道的管地电位偏离安全范围,加剧管道的腐蚀。西气东输二线西部管道多处管地电位监测数据显示,不同位置的管地电位具有幅度不同且变化趋势相同或相反的特征。对该区域进行三维大地电导率建模,应用2016年9月28日乌鲁木齐地磁台监测数据作为电磁激励,结合Galerkin有限元法与LZS-DSTL理论,计算了该区域管地电位的时空分布,通过与监测数据对比,验证了该方法的有效性。通过对管地电位时空分布特征分析,提出了管地电位空间分布的"波节"和时间变化的"纠缠"概念,根据理论分析和现场管道监测数据揭示了二者之间的内在联系,进一步研究了影响管地电位"波节"分布的重要因素。研究结果表明,管地电位"波节"和"缠绕"现象是普遍存在的,"波节"既是管地电位的空间分布过零点,又是管地电位时域变化趋势的分界点;管道地磁感应电流的极值位置往往与管地电位"波节"相对应,为管道阴极保护装置的合理配置提供了理论依据。

Distribution characteristics of wave joint and entanglement of pipe-to-soil potential on buried pipeline induced by geomagnetic storm

The magnetic storm induces geoelectric fields and geomagnetic induced currents (GIC)in the earth medium, which cause the pipeline-to-soil potentials (PSP)of long-distance buried pipelines to deviate from the safe range, aggravating the corrosion of pipelines. Monitoring data from multiple PSP on the western area of the 2nd west-east pipeline project (WEPP II)show that PSP at different locations has different amplitudes and the same or opposite variation trends. This paper study carries out 3D earth conductivity structures modeling for the area, and applies the monitoring data obtained from Urumqi geomagnetic station on September 28, 2016 as the electromagnetic excitation. In combination with the Galerkin finite element method and LZS-DSTL theory, a calculation is performed on the spatial and temporal distribution of pipeline PSP. Finally, the validity of this method is verified by comparison with the monitoring data. Based on analyzing the spatial and temporal distribution characteristics of PSP, the paper proposes two concepts of spatially distributed PSP "wave joint" and time-varying PSP "entanglement", reveals the intrinsic connection between the two based on theoretical analyses and on-site monitoring data of pipelines, and further explores the crucial factors impacting the distribution of PSP "wave joint". The research results show that the PSP "wave joint" and PSP "entanglement" are common phenomena. The "wave joint" is both the zero-crossing point for the spatial distribution of PSP and the demarcation point of the change of PSP time-domain. The extreme position of GIC often corresponds to the PSP "wave joint", providing a theoretical basis for the rational configuration of cathodic protection device of the pipeline.