考虑非线性极化效应时直流接地极电流在油气管道耦合的电压电流建模和计算

Modeling and Calculation of the Coupled Voltage and Current on the Oil and Gas Pipeline From the HDVC/UHDC Electrode Grounding Currents While Considering the Nonlinear Polarization Effect

准确预测直流输电接地极电流对埋地油气管道的腐蚀影响,并采取合理的防护措施,对能源输送安全至关重要,但现有预测方法缺乏对管道金属与土壤间非线性极化影响的系统研究。该文建立考虑非线性极化效应时直流接地极入地电流对埋地油气管道耦合电压和电流的数学模型;提出矩量法与有限元法结合计算含非线性极化交界面三维电流场的方法,并试验验证该方法的有效性;对不考虑极化、考虑线性和非线性极化时的计算与试验结果进行对比,获得误差分析结果;最后,进行工程应用分析。结果表明:提出的计算方法可有效考虑非线性极化效应的影响,采用不考虑极化或线性极化影响的计算结果进行管道腐蚀评估,将导致腐蚀风险被高估或低估。为准确预测管道电压和电流,管道金属与土壤间的非线性极化效应不可忽略。在管道设计和建设中,考虑非线性极化影响将避免增加不必要的防护和维护成本,或避免预测不足带来的腐蚀风险。

It is very important to calculate the corrosion effects of HVDC grounding current on the pipelines accurately and take proper protective measures for the energy transmission safety.Related prediction methods are still short of systematic research considering the nonlinear polarization between on the interface between soil and the interfered pipeline.A mathematical model was established for the coupling voltage and current on the buried oil gas pipelines induced by grounding currents considering nonlinear polarization.A method was proposed to calculate threedimension electric flow field by combination of the method of moments(MoM)and the finite element method(FEM)when considering nonlinear polarization.The validity of calculation method was verified by experiments.Error analysis results were obtained by comparing the calculation results of no polarization model,linear polarization model and nonlinear polarization model with the experiment results.The calculation results of a typical engineering cases were analyzed in the end.The results show that the proposed method can effectively consider the influence of nonlinear polarization.Pipeline corrosion risk will be overestimated or underestimated when assessing the pipeline safety considering no polarization or linear polarization.The nonlinear polarization between pipeline meatal and soil cannot be neglected for accurate prediction of the leakage current density and pipe-to-soil potential.A lot unnecessary protection and maintain cost can be avoided,alone with the risk resulting from underestimated prediction in design and construction stage by proper calculation and analysis when considering nonlinear polarization.