Research On Optimization Of Natural Grounding Scattering Of UHV Transmission Line Poles

The grounding network of transmission line towers generally includes natural grounding and artificial grounding.Among them,the structure and dispersion characteristics of concrete pile foundations are generally determined during the construction of the towers.In order to enhance the dispersion and reduce the grounding resistance,the pile foundation needs to be laid.Horizontal extension grounding body.The design size of the extension grounding body is large,and the construction requires a lot of manpower,material resources and financial resources.At the same time,the natural grounding of the pole-pile foundation has not been paid much attention.After the pole-pile foundation is naturally air-dried,the construction method of immediate backfilling is usually adopted,which fails to give full play to the dispersive capacity of the steel bar.Practical engineering experience shows that the pole-pile foundation pit has the characteristics of large size and deep embedment.In the "golden age" of pole-pile foundation pit excavation,the vertical grounding device is used as the main body of the transmission tower to optimize or even cancel the space.Extension grounding reduces the area occupied by cultivated land.Based on this,this paper proposes to build a vertical external grounding device for the pole and tower pile foundation based on flexible graphite composite grounding materials,and uses COMSOL simulation calculation software to establish a single pile and bearing type UHV transmission line pole and tower pile foundation dispersion calculation model.The main research content of this paper as follows:(1)Simplify the equivalent value of the steel structure model of the single-pile and bearing type concrete pile foundation to the equivalent structure model.The error of the single-pile pile foundation before and after the equivalent value is within 5%,and the error of the bearing type is within 0.5%,etc.The error before and after the value is within the allowable range,which effectively reduces the difficulty of establishing a simulation model and increases the speed of simulation calculation.(2)The dissipation models of single-pile external cage,single-helix and double-helix grounding devices were established respectively,and the dissipation coefficient and resistance reduction efficiency of the three grounding devices were compared and analyzed.Increasing the number of turns of the grounding device can make three The dissipation coefficient of the grounding device is increased,and the dissipation coefficient of the cage grounding device is the highest.When the soil resistivity is 1000Ω·m,the dissipation coefficient of the cage grounding device can reach more than 70%,and the resistance reduction efficiency can reach up to 36 %,while the dissipation factor of the single screw grounding device is less than 60%,and the resistance reduction efficiency is only about 26%.(3)Establish the natural grounding,external application optimization and extension optimization dispersion model for the full pile foundation of the single-pile tower,and analyze the dispersion characteristics of the external application optimization and the extension optimization.The analysis results show that for natural grounding and extensional grounding,the pole-tower pile foundation needs to bear 70% of the dispersed current component,while for external grounding,the pole-tower pile foundation only needs to bear about 40% or even less of the dispersed current component,which is very good.Relieve the diffuse pressure of the pile foundation of the pole tower.(4)Extend the analysis of single-pile pile foundation to bearing type multi-pile pile foundation,establish the natural grounding,external application optimization,and extension optimization dispersion model of the whole pile foundation of the multi-pile pile caps,and compare the three grounding methods.The impact of grounding current shunt.The calculation results show that under the condition of layered soil,when the upper soil resistivity is low,the epitaxial grounding body can shunt about 40% of the current of the bearing platform,which effectively reduces the potential rise of the tower pile foundation to the grounding;the lower soil resistivity is lower At this time,the cage grounding device bears more than 70% of the current shunt,and the maximum grounding potential rises and drops by more than 11%.The relevant conclusions of this article can provide references for the grounding design and construction of power poles,telecommunication poles,railway poles,factories and mines,wind turbines and other industries.