Study On The Impulse Characteristics Of Grounding Devices Considering Soil Dynamic Ionization Effect

The good dispersion characteristics of the grounding device are an important prerequisite for reducing lightning accidents and the basis for ensuring the safe and reliable operation of the entire transmission system.Accurate analysis of the impact characteristics of grounding devices is particularly important for evaluating the lightning protection calculations of transmission lines and towers.In addition,the uneven distribution of ground caused by the discharge process may form a large step voltage difference,which will seriously threaten the safety of supervisory and maintenance staff and threaten the electrical integrity of IED.Therefore,studying the impact characteristics of grounding devices is of great significance to the stable operation of power systems.Therefore,the thesis launched a research on the impact characteristics of grounding devices.The specific research work is as follows:Firstly,on the basis of researches of the impact characteristics of grounding devices by domestic and foreign scholars,considering the nonlinear relationship between the soil resistivity and the electric field in the ground,a finite element calculation model of the impact characteristics of the grounding devices for soil dynamic ionization is established.To verify the accuracy of the model,the simulated results are compared with the on-site measured results.At the same time,in order to solve the problems of non-convergence of the simulated results caused by the fine meshing of grounding devices and the insufficient computer running memory,the space coordinate transformation and the finite difference time domain method are introduced,and the smooth function is used to transition the parameter changes of the finite element.Secondly,it focuses on the relative leakage current of the grounding electrode conductor section,and quantitatively analyzes the dispersion characteristics of the grounding electrode.The research results show that the leakage current of the grounding device presents an uneven distribution shape,and the distribution of the leakage current along the grounding conductor during the impact dispersion shows an obvious edge effect.Subsequently,the results of the soil dynamic ionization model proposed in this paper are compared with those in the literature.From the perspective of engineering practicability,this paper analyzes the ground potential distribution of several grounding electrodes before and after soil dynamic ionization.Then,by changing the influence parameters,the variation of grounding grid surface potential,current density,electric field strength and impact ground resistance are simulated and analyzed.The research results show that: 1)The greater the soil resistivity,the more uneven the grounding grid surface potential distribution,the more significant the edge effect,and the greater the ground grid impulse ground resistance;2)The smaller the current amplitude,the smaller the grounding grid’s electric field strength,and the ground surface potential.The more uneven the distribution,the smaller the impulse ground resistance;3)The smaller the area of grounding grid,the smaller the peak of the surface potential,the greater the impact grounding resistance,and the smaller the difference in electric field strength.Finally,aiming at the edge effect and shielding effect of the grounding electrode under the action of the impulse current and from the perspective of improving the utilization rate of the grounding electrode conductor,the arrangement length,arrangement angle and arrangement type of the added short conductor are systematically studied.The results show that adding the auxiliary grounding electrode can partly reduce the impulse ground resistance,balance the surface potential distribution,and improve the current dissipation efficiency of the grounding device.The research results of this paper can provide theoretical guidance and engineering design ideas for the design of actual engineering grounding devices.