高压直流接地极对埋地管道的电流干扰及人身安全距离

高压直流输电系统的直流接地极在运行初期或发生故障和检修时,会产生瞬间大电流,给附近埋地油气管道设施及操作人员带来极大的安全隐患。为了保障埋地管道附近人员的安全,对高压直流接地极对埋地管道的电流干扰及人身安全距离(以下简称安全距离)进行了研究。首先利用数值模拟技术建立了埋地管道受电磁干扰的模型,进而利用该模型计算了不同土壤电阻率、管线长度、管道防腐层、接地极入地电流、管道尺寸等情况下,高压直流接地极对埋地管道杂散电流干扰的安全距离,并分析了上述条件对高压直流接地极干扰程度的影响规律。研究结果表明:①管线长度对高压直流接地极干扰程度的影响较大,管线越长,安全距离越大,但当管线长度达到或超过600 km时,安全距离则基本不变;②管线涂层对高压直流接地极干扰程度的影响较大,随着涂层面电阻率的增加,安全距离逐渐增大;③对于多层土壤结构,可将最大的单层电阻率作为整体电阻率,其计算得到的安全距离最大,评价结果也更为保守。结论认为,利用计算结果得到的4类长度管线的安全距离图谱,可供高压直流接地极及管线设计时参考,并且可以作为拟建高压直流接地极或埋地管线安全距离选取的依据。

Current interference of HVDC ground electrode to buried pipelines and its personal safety distance

When DC ground electrode of a high-voltage direct current (HVDC) transmission system is in the stage of early operation or in the case of failures and maintenance, an instantaneous large current will be generated and bring great potential safety hazards to the nearby buried oil/gas pipelines and facilities and operators. In order to ensure the safety of the persons near the buried pipelines, we investigated the current interference of HVDC ground electrode to buried pipelines and its personal safety distance (hereinafter referred to as a safety distance). Firstly, the model simulating the electromagnetic interference to buried pipelines was established by means of the numerical simulation technology. Then, the model was used to calculate the safety distance corresponding to eddy current interference of HVDC ground electrode to buried pipelines under different soil resistivities, pipeline lengths, pipeline anti-corrosion insulations, earth currents of ground electrode and pipeline sizes. Finally, the influence laws of above mentioned factors on the interference degree of HVDC ground electrode were analyzed. And the following research results were obtained. First, the influence of pipeline length on the interference degree of HVDC ground electrode is great. The longer the pipeline, the greater the safety distance. When the pipeline is equal to or longer than 600 km, however, the safety distance is basically the same. Second, the effect of pipeline coating on the interference degree of HVDC ground electrode is great. As the coating surface resistivity increases, the safety distance increases gradually. Third, for multi-layer soil structures, the maximum single-layer resistivity can be taken as the overall resistivity. And correspondingly, the calculated safety distance is the longest, and the evaluation result is more conservative. In conclusion, the safety distance diagrams of the pipelines with 4 lengths which are obtained based on the calculation results can be used as reference in the design of HVDC ground electrode and pipelines, as well as the basis for selecting the safety distance of HVDC ground electrode or buried pipelines to be constructed.