Analysis Of Electric Corrosion Effect Of Yanmenguan DC Grounding Electrode On Nearby Buried Metal Structures

There are multiple substations(Wuzhai,Yijing),wind farms(Shenchi Banjing,Nanhuashan,Jiyangshan,Liugou,Limin)and gas pipelines(Shenchi-Pianguan)around the DC grounding electrode of Yanmenguan in northern Shanxi.When the DC grounding electrode is operated in a single-maximum return line mode,the huge DC current will change soil potential greatly.Direct current into the ground will not only destroy the stability of the nearby AC power grid,but also accelerate the corrosion of nearby buried metal components and affect the normal use of electrical facilities.For the former,the influence of the grounding electrode on the AC grid is chiefly reflected in the DC bias of the transformer.And the research of DC bias technology has become more mature.For the latter,the effects of ground current to corrosion and cathodic protection of underground metal facility is still a lack of effective assessment method,which makes direct current transmission project construction in a security risk.The thesis mainly studies the respects below:(1)First,the soil structure near Yanmenguan was inverted using CDEGS software and an electromagnetic simulation model of the DC transmission system operating in single-max mode was built.Then the voltage distribution of nearby substations,wind farm grounding grids and buried metal pipelines when the Yanmenguan DC grounding electrode operates in a single-maximum loop mode is calculated.Finally,the effects of injection current,soil resistivity,local uneven soil resistivity,and distance on the voltage distribution of buried facilities are studied.(2)Based on the magnitude and duration of the DC grounding current into the ground,combined with Faraday’s electric corrosion law,the annual corrosion amount of the substations,wind farm grounding grids and buried metal pipelines near the Yanmenguan DC grounding electrode is calculated.According to the results of the voltage distribution of buried metal facilities and the depth of electrical corrosion,the rationality of the DC grounding electromagnetic interference limit is verified.(3)In view of the corrosion of DC grounding electrode to buried metal pipelines,several measures to suppress the corrosion of DC grounding electrode to metal pipelines are studied.including insulation layer performance,installation of insulating joints,forced current method,sacrificial anode method.At the same time,the protective effect and applicability of these measures were evaluated.