| Grounding grid is an important facility of power system.It is closely related to the safety of personnel and equipment and the stable operation of power system.The metal of grounding grid will be corroded by soil in an electrochemical way.The service life of grounding grid will be shortened by corrosion causing serious economic losses.In addition,corrosion will affect the performance of grounding grid and endanger the power system.Studying on the corrosion behavior of different metals is important to improve the evaluation methods of corrosion characteristics in our country,and to estimate the actual service life of the grounding grid.So this paper can be a reasonable guide for materials selection in projects.In this paper,the key reasons for the metal corrosion in soil are researched,the influence factors of soil corrosivity are analyzed.Based on the single evaluation method of soil corrosivity,the comprehensive evaluation system of soil corrosivity is put forward and verified.This evaluation system helps to judge the strength of soil corrosion more accurately.Various evaluation methods of corrosion characteristics are compared in this paper and the weak polarization evaluation method is selected.Different data processing methods such as ’Barnartt three-point method’,’four-point method’,and ’Single direction polarization three-point method’ are compared.The TLBO intelligent algorithm is applied to analyze the polarization curve in this paper.It shows that this method has advantages on data utilization rate and results accuracy compared with other traditional methods.It is a more scientific and reliable evaluation method.Based on the electrochemical polarization tests,the factors that affect the corrosion characteristics are analyzed in this paper:①The relationship between corrosion potential and water content is analyzed.The experimental results show that the corrosion potential is stable with the increase of the polarization time,and decreases with the decline of soil water content;②The relationship between corrosion current density and water content is analyzed.The experimental results show that the corrosion current density increases first and then decreases with the increase of soil water content,which is at a low level when the water content is saturated;③The corrosion rates of carbon steel,galvanized steel and copper plated steel are compared so as to help the materials selection in projects.The experimental results show that the corrosion rate of carbon steel is the fastest,galvanized steel is the second,and the copper plated steel is the slowest. |
