Study On Polarization Excitation Corrosion Detection And State Evaluation Method Of Grounding Grid

With the development of society,the capacity of modern power grids is getting larger and larger,the area of grounding grids is getting larger and larger,the fault current carried is also increasing,and the requirements for various performance indicators of grounding grids are also getting higher and higher.However,due to frequent safety accidents caused by grounding grid problems,regular inspection and diagnosis of grounding grids is imperative.Most of the grounding grid materials in China are flat steel,and many grounding grid accidents are caused by grounding grid corrosion,so it is also of great significance to evaluate the degree of grounding grid corrosion.Based on this,the paper starts the research on the monitoring method of the grounding grid corrosion and the evaluation method of the corrosion degree,as well as the research work on the grounding grid condition assessment and grounding grid transformation.Aiming at the corrosion problem of grounding grids,a new corrosion detection method is proposed,which is electrical source induced polarization corrosion detection.The voltage decay curve is obtained by injecting high voltage into the ground grid,and then the relationship between the decay time constant and the corrosion degree of the ground grid is obtained through data analysis.This method overcomes the shortcomings of weak anti-interference ability of the conventional polarization curve method and improves the reliability of the data.A conventional polarization curve corrosion detection experiment platform is established for long-term ground network corrosion detection.The experimental data is processed and analyzed through three data fitting methods.The larger the corrosion current,the faster the ground network corrosion rate is.The reliability of the method is proved,and the result is used as a reference for verifying the new detection method.An experimental platform for excited polarization corrosion detection was established,and it was proposed to use bipolar square wave excitation for polarization research.The bipolar excitation successfully offsets the impact of the corrosion voltage of the grounding grid itself.Compared with the unipolar excitation,the detection result is more accurate,and the bipolar excitation is more resistant to interference.Through longterm experiments,combined with multiple sets of data statistics of the voltage decay time constant and the trend with time,the conclusion is drawn that the greater the corrosion of the grounding grid and the smaller the decay time constant,and the correctness of the conclusion is verified through theoretical analysis.For different emission currents,different pole distances,different grounding grid sizes,and different operating currents,the experiments are respectively compared.Experimental and theoretical analysis show that the current amplitude frequency and pole distance have no effect on the experimental results.When laterally analyzing different sizes of grounding grids It is necessary to normalize the area of the time constant τ obtained by the experimental treatment to compare and analyze.Therefore,the concept of normalized corrosion degree is proposed,and the corrosion degree of the grounding grid is directly evaluated by this.Establish a ground grid state assessment system and a ground grid state assessment model with software CDEGS as the core,analyze the impact of different normalized corrosion degrees on the ground grid safety performance,and conduct a ground grid safety state assessment.Finally,based on the analysis of the impact of deep well grounding on the grounding grid,the grounding grids in horizontally and vertically layered soils were analyzed in terms of the location,number,and length of the grounding poles in the deep wells.