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 persons near the buried pipelines, we investigated the current interference of the 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 interference of the 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 obtained 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 electrodes and pipelines, as well as the basis for selecting the safety distance of HVDC ground electrode or buried pipeline to be constructed.