Research On Stray Current And Overvoltage Protection At The Intersection Of Transmission Lines And Oil-Gas Pipelines

Due to the large area occupied by transmission lines in China,overhead lines are sometimes adjacent to and crossed with oil-gas pipelines along the way,which makes the electromagnetic interference problem caused by the "two lines and one place" of transmission lines and oil-gas pipelines is increasingly prominent,and the safe operation and protection of pipelines are attracting more and more attention.This paper mainly studies the electromagnetic influence of transmission lines crossing buried oil-gas pipelines and the protective measures.Firstly,the influence mechanism and calculation method of ac transmission lines on buried oil and gas pipelines are analyzed.Second,by CDEGS software established 500 kV transmission lines and buried oil-gas pipeline crossing across the electromagnetic influence model,then by using this model the influence of crossing angle of transmission lines and pipelines,soil resistivity,soil stratification,average height of the wire,wire load current and the pipe outer diameter,wall thickness,coating resistivity and grounding grid on electromagnetic interference in the case of normal operation of transmission lines and lighting strike is analyzed.Finally,this paper analyzes the electromagnetic interference protection in the view of "two lines and one place" for transmission lines and oil-gas pipelines: comparative analyze of the effect of protection line made by bare copper and flexible graphite composite grounding material on remitting line interference voltage and AC interference current under normal operation condition,research the influences of different shapes grounding grids made by zinc-coated steel and flexible graphite on lightning overvoltage of adjacent pipeline by simulation,and give the construction suggestions for protection of oil and gas pipeline overvoltage under lightning strike.The research shows that the angle between the transmission line and the pipeline and the load current of the wire have a great influence on electromagnetic interference,while the soil structure,the height of the wire and the outside diameter of the pipe have little influence,and the wall thickness of the pipe and the grounding device have little influence.In the case of a lightning rod transmission line,the lightning current amplitude,soil structure and the distance between the line and the pipeline have a great influence on the pipeline overvoltage,and the shape of grounding device only affects the pipeline overvoltage within a short distance.Laying protection line has significant effect on mitigating continuous interference and ?30mm double graphite protection line and 100×8mm planar graphite material performance better than bare copper belt.By changing the extension direction of the grounding body of the tower,the induced over-voltage of the underground pipe and coating can be buried,and the electric shielding wire laid along the pipe can significantly reduce the electric potential difference between the inside and outside of the pipe coating.?30mm graphite composites grounding grid has similar effect of reducing pipeline overvoltage to ?10mm metallic material when using the same shape.The conclusion of this paper can provide practical reference for transmission line design and oil and gas pipeline safety protection.