Study On Hydro-power Station Grounding In The High Soil Resistivity Region

The Hydro-power Station grounding system is ultimate insurance and step which ensuring power system run safely, protecting the safe of stuff and instructions. Therefore, research on the grounding system has played a decisive role in grounding design of hydro-power station, especially large-scale hydro-power stations which is in high soil resistivity area, because of great ground fault current, in order to ensure system security and reliable operation, grounding resistance should be reduced.On the basis of geological survey results, site visits and survey data of design institute, as Hydro-power Station is located in high soil resistivity area, underwater grounding grid is taken as the research object in this paper. According to the characteristics taking Nuozadu hydro-power station as example, horizontal three-layer and vertical three-layer soil model is adopted, and based on complex image method the Green's function is derived for hydro-power station geological structure, moreover, using program compiled by boundary element method to calculate the grounding resistance of Nuozadu hydro-power station.For hydro-power station, analysis the impact of water depth, river resistivity, resistivity of river bottom rock on grounding resistance of hydro-power station. According to the maximum short-circuit current, analysis the maximum contact and step potential and it is conclude that t the grounding resistance of hydro-power station whether or not meet the requirements. it was calculated that the grounding resistance of Nuozadu hydro-power station does not meet the requirements.For most of high soil resistivity areas, especially mountain hydro-power station, generally the field has high soil resistivity, small, thin soil and the soil is mostly landwash waste, sand, or completely stones. Soil resistivity as high as 2000~3000??m, some even as high as 5000~8000??m, and thus most number of hydro-power station has high grounding resistance. Based on this reducing resistance techniques and methods are introduced briefly.â‘ using of natural grounding body.â‘¡setting manual grounding grid. The methods of manual grounding grid introduces underwater grounding grid, exterior grounding conductor, deep-well grounding, manual changing soil, grounding device and adding Resistance Reducing Agent. According to the actual situation of Nuozadu hydro-power station, underwater grounding grid of 150000 square meter is adopted by analysising grounding parameter in difference area, and it is considered that laying eight 30m long vertical grounding rods around the layout of 500kV outgoing line field based on the analysis of grounding parameter.