Research On Current Overflowing Effect On Corrosion Of Earth Electrode

Earth electrode is used as a connection between electrical appliances and earth,thus it can transmit the short circuit current protecting the grid,electrical appliances.With the earth electrode deeply laid in the soil for long,the corrosion,which mainly consists of chemical corrosion,electrochemical corrosion and anaerobic corrosion,unavoidably will occur.Meanwhile,grounding current affect the corrosion of the earth electrode as well.When the corrosion is much too serious,transmission between the earth and fault current will be cut off.This paper covers the characteristics of various current inputted to earth electrode and its effect on the corrosion of earth electrode.Main work content of this paper as follows:Firstly,current-overflowing theoretical models of single horizontal,vertical and slant earth electrode in infinite homogeneous soil by collocation method is built.Current overflowing model of single earth electrode in homogeneous soil and corrosion model respectively is built also.With the two models,the model is verified through simulation and analysis.To make the research closer the reality,the influence of down lead to the earth electrode and the influence of amplitude of ground current towards current dispersion are analyzed.Secondly,electrochemistry principle of corrosion of the earth electrode is been analyzed so that a model using equivalent conductivity to show conductive property of the soil electrolyte is built without consideration of diffusion effect.Simulation of distribution and time of corrosion deformation,pore saturation of soil and conductivity is carried out to reveal the connection between them.Finally,the principle of current circulation in earth electrode is revealed.With changing the electric potential of electrode surface or surrounding soil,the current dispersion of electrode is able to improve.Injecting separately positive or negative dc current and ac current,the influence of electric potential,current dispersion density,cathode and anode electrochemical reaction and corrosion deformation distribution is researched with consideration of consideration of diffusion effect.