交流输电线路对管道腐蚀影响的安全距离研究

Research on safety distances between AC transmission lines and buried pipelines for mitigating AC corrosion

随着我国经济的高速发展,能源输送网络不断建设完善,在许多地区由于地理位置限制使得高压输电线路和油气管道形成“公共走廊”。高压交流输电线路通过电磁感应作用对埋地管道产生交流干扰,当电流从管道防腐层破损点流出时会引发交流腐蚀问题。实际工程中掌握输电线路与管道的安全距离,就可以从选址阶段进行有效避让,避免后期管道可能受到的干扰问题。针对该问题,首先确定了交流腐蚀的安全指标,然后利用数值模拟技术建立了交流输电线路对埋地管道交流干扰模型,计算研究了典型的土壤电阻率、防腐层、输电线路等级、输电系统不平衡度、管径情况下的输电线路与管道的安全距离。结果表明:输电线路电压等级越高,需要的安全距离越大。对于220 kV及以下高压交流输电线路(单相电流小于1000 A),当其与管道间距大于868 m时,管道所受交流腐蚀风险可以忽略。并行长度越长,需要的安全距离越大。当并行长度大于40 km时,安全距离变化不大。土壤电阻率、管道防腐层以及输电线路等级对安全距离影响比较明显。土壤电阻率越低,所需的安全距离越大,因此当管道处于农田土或者盐碱土中时,需要更大的安全距离。管道防腐层质量越好,需要的安全距离也越大,因此3PE防腐层需要更大的安全距离。输电系统不平衡度对安全距离影响较小,这表明对于临近安全距离的管道,其交流干扰的主要来源是相线之间位置差异,而不是电流的不平衡性。管道直径对于安全距离的影响也比较小,这是因为管道的纵向阻抗相比于泄漏阻抗要低很多,也就导致其对纵向电场的累积效果影响不大,因此对安全距离影响较小。在此基础上建立了安全距离图谱和评价方法,并将该方法应用于某实际管道的交流干扰分析,结果显示根据安全距离可以很好地判断管道的干扰风险。本研究成果为新建管道与输电线路避让提供了方法和参考依据。

With the rapid development of China's economy and the substantial construction of energy transmission networks,high voltage transmission lines and oil and gas pipelines usually form a"Right-of-Way",especially in space restricted areas.AC transmission lines can induce AC interference in the pipeline.When the AC current flows out from the defects of the pipeline’s coating,AC corrosion will be caused.The safe distances between AC transmission lines and pipelines should be clearly defined for keeping them away from each other at the routing stage,and possible interference on the pipeline will be avoided.In this paper,safety indicators for AC corrosion were first identified,then numerical simulation was used to establish the buried pipeline’s AC interference model.The safe distances in typical conditions were calculated.These include soil resistivity,pipeline coating,voltage level of HVAC transmission line,three-phase imbalance and pipeline diameter.The results indicated that the higher the voltage of the transmission line,the greater the safety distance required.For high-voltage AC transmission lines with voltage less than 220 kV and phase current less than 1000 A,when the distance between the pipelines and the high voltage transmission line was greater than 868 m,the AC corrosion risk of the pipelines could be ignored.The longer the parallel length was,the greater the safety distance required.When the parallel length was greater than 40 km,the safety distance did not change much.Soil resistivity and pipeline coating had obvious effects on the safety distance.The lower the resistivity of the soil,the greater the safety distance required,and therefore greater safety distance was required when the pipeline was in farmland or saline soil.The better the coating of the pipeline,the greater the safety distance was required,so a greater safety distance was needed for 3PE coated pipeline.Three-phase imbalance current had little effect on the safe distances,which indicated that the main source of AC interference for pipelines near safety distance was the position difference between phase lines,rather than the current imbalance.The pipeline diameter also had little effect on the safety distance.It was due to the longitudinal impedance of the pipeline being much lower than the leakage impedance,it had little effect on the longitudinal electric field.And on this basis,a safety distances map and evaluation method were established.Then,this method was applied to the AC interference assessment of a real pipeline,and the results showed that the interference risk of a pipeline can be estimated well from the safety distance.The results of this study provide a method and reference for dealing with pipelines and high voltage transmission lines in“Rights-of-Way”.