Frequency Sweeping Characteristics And Safety Analysis Of Grounding Towers Of Overhead Transmission Lines

The grounding device of transmission line tower is the connecting channel between the tower and the earth.The grounding system state directly affects the lightning protection performance of transmission lines.The grounding device of the tower is buried in the ground,so it is easy to form grounding system failure due to corrosion of the soil environment.Therefore,it is of great significance to carry out the corrosion state detection of the tower grounding and accurately assess its safety performance,which is of great significance for the safe and stable operation of overhead transmission lines.In view of the grounding corrosion detection problem of the overhead transmission line towers,this paper analyzes the electrochemical corrosion mechanism of the tower grounding body and the influencing factors of corrosion.A grounding resistance swept frequency measurement method is proposed that does not disconnect the ground lead wire,and the feasibility of the method is verified by simulation.In order to study the dispersion characteristics of different types of grounding electrodes and the effects of different corrosion states on the distribution characteristics of grounding electrodes,a dynamic finite element analysis model of horizontal grounding electrodes and a cross section model of grounding bodies with different corrosion shapes were established.The relationship between the distribution of the magnetic field distribution of the grounding pole and the frequency under various conditions was simulated.At the same time,the grounding impedance sweeping characteristics under corrosion cracking,overall corrosion and local corrosion were obtained.A lossy transmission line model of horizontal grounding body is established to study the impact wave process of horizontal extended grounding body.The relationship between the waveform of the impact grounding resistance and the location of the corrosion point and the corrosion depth of the grounding body was analyzed when the impact current was injected into the first end of the horizontal earth body and the grounding body was corroded.The research results show that the grounding resistance sweep frequency measurement method can accurately measure the grounding resistance of the tower without disconnecting the ground deflector and reduce the workload of grounding corrosion evaluation.The analysis of the sweep impedance of grounding impedance can clearly distinguish whether the grounding system has corrosion cracking,overall corrosion and local corrosion defects.In areas with high soil resistivity,the waveform characteristics of the impact resistance of the tower can effectively reflect the local corrosion location of the tower grounding body and Corrosion degree.It provides a new method for corrosion detection of the tower grounding system.Finally,the safety of the tower grounding system is analyzed,and on the basis of which,the corresponding protective measures are proposed.This provides technical support for the safety evaluation of the tower grounding of the overhead transmission line.