Experimental Research On Electromagnetic Interference Of UHVDC And Geomagnetic Storms In Buried Pipelines

The grounding current caused by grounding poles of Ultra High Voltage Direct Current(UHVDC)and the buried pipelines are interfered by geomagnetic storms and,which is the problem worth being investagated and controlled for the development of power grid and oil and gas pipeline network.This problem involves electrotechnics,engineering,space physics,geophysics and other disciplines.Theoretical analysis is not enough to explain the problem,so the scientific experiments should be carried out in order to research the interference mechanism and prove the theoretical analysis.In this paper,the characteristics and rules of UHVDC and geomagnetic storm disturbing buried pipelines are analyzed through the observation experiment and model calculation of pipeline stray current including geomagnetic induced current(GIC)and pipeline ground potential(PSP).On this basis,an effective prevention scheme of pipeline stray current is put forward.The main contents and achievements are as follows:(1)The stray current and PSP observation scheme are designed,according to the structure and characteristics of buried pipeline network.For the first time,stray current(GIC)and PSP observation data of ground polar current are obtained,as well as,the phenomenon of geomagnetic storm impacting pipelines in]ow and middle latitudes is observed.The results show:in the pipeline 150 km away from the grounding pole,the stray current is 3.3A and the PSP offset exceeds 100mV;in the pipeline 60 km away from the grounding pole,the stray current is 7A and the PSP offset is 900mV,the GIC of the small and medium geomagnetic storms is 3.98A,the PSP offset is relatively small,the GIC of the large geomagnetic storms is 7.5A and the PSP offset is 430mV.These experimental data provide a basis for understanding the characteristics and rules about interference of ground polar current and geomagnetic storm on pipelines.(2)The computing method of stray current and PSP of pipeline are improved by combining three-dimensional georesistivity model and classical transmission line theory.Then the accuracy of the algorithm is illustrated by monitoring data.The characteristics and rules are obtained,about the influence of the distance between pipeline and UHVDC grounding electrode on buried pipeline.The influencing factors of stray current and PSP under UHVDC interference pipeline are determined,including the cathodic protection current and the insulation joint.The relationship between influence level with distance,pipeline direction and structural parameters is discussed.It is recognized that pipelines 50-60 kilometers away from grounding poles need anti-corrosion measures.(3)The computing method of GIC and PSP of pipeline are improved by combining the three-dimensional georesistivity model with the distributed source transmission line theory,the GIC and PSP of the pipeline are calculated theoretically.The correctness of the model and algorithm of the interference effect of geomagnetic storms on buried pipelines is verified by comparing the simulation results with the measured results.The characteristics of the GIC and PSP effects of medium and large geomagnetic storms on buried pipelines are obtained.The influence factors of pipeline corrosion caused by different intensity geomagnetic storms are determined.It is recognized that the influence of geomagnetic storm electromagnetic interference on pipeline corrosion is great.The results of observation experiments and theoretical calculation in this paper have changed the mistaken understanding of the influence of geomagnetic storms on pipelines in high latitudes and the existence of geomagnetic storms.The characteristics and rules of the stray current(GIC)and PSP effects of buried pipelines have been proved,which are of great significance to the prevention and control of pipeline corrosion.