Study On Impulse Characteristics And Its Influencing Factors Of Grounding Grid In Substations

When a substation is subjected to a lightning strike,the grounding grid is the main channel for the lightning current to flow into the ground.Due to the inductance effect of the grounding grid and the high amplitude and high frequency of the lightning current,the ground potential will rise rapidly,giving people and electrical equipment in the station.Poses a serious threat.Therefore,studying the impact characteristics of the substation grounding grid is of great significance to the lightning protection of the substation.Due to the high amplitude and high frequency lightning current,the soil will cause non-linear ionization,which makes the impact characteristics of the grounding grid significantly different from the power frequency characteristics.In addition,the impact characteristics of the grounding grid are also affected by soil parameters and lightning current parameters.The influence of factors such as the structural parameters of the grounding grid and other factors interfere with each other and are inseparable.Therefore,it is extremely important to study the influence of these factors on the impact characteristics of the grounding grid considering the nonlinear ionization effect of soil.Based on this,this paper combines the shortcomings of the existing research on the impact characteristics of the grounding network,and conducts the following studies:Based on the existing research results and theories,this paper proposes two methods of simulating soil nonlinear ionization based on equivalent radius theory and residual resistivity theory,and compares them with experimental values in the literature to establish a simulation method.Considering the correctness of this article,considering that this article will perform a large number of analysis and calculations on complex grounding grids,the residual resistivity theory is selected to simulate the nonlinear ionization effect of soil.A simulation of grounding grids considering soil nonlinear ionization effect based on CDEGS software is established Model and calculation process.Based on this model,the effects of factors such as soil resistivity,grounding grid depth,grounding conductor radius,vertical grounding pole,lightning current parameters,and compression ratio of the grounding grid on the impact characteristics of the substation grounding grid were systematically analyzed.The variation of the impact of the grounding network on the ground resistance,the maximum ground potential rise,the contact voltage,the step voltage,and the ground potential distribution under the above factors.Due to the mutual interference between the various influencing factors,they are inseparable.In order to further study the primary and secondary relationship of the impact of multiple factors on the impact characteristics of the grounding network,orthogonal experiments and range analysis methods were used to analyze the impact of the various factors on the impact of the grounding network.The influence law and the primary and secondary relationship of the impact of each factor on the impact characteristics are obtained,and the return analysis of each impact factor can provide a reference and basis for the optimal design of the grounding grid.Based on the analysis of the influence of various influencing factors on the impact characteristics of the grounding grid and the distribution of ground potential,combined with the arrangement of ground conductors with unequal spacing,a 110 k V substation grounding grid was proposed to reduce the impact ground resistance and balance the ground potential Optimize the design.The calculation results show that the safety indexes of the optimized grounding grid can reach the required safety limit range,the impact grounding resistance has been greatly reduced,the surface potential distribution has been greatly improved,and the safety level of the substation has been greatly improved,which illustrates the effectiveness of the optimization design method.It can provide reference and guidance for the optimal design of the actual grounding grid project.