Study On Current Overflowing Characteristic Of Earth Electrode And Effect On Corrosion Of Earth Electrode

Earth electrode is laid in the soil for current overflowing, to ensure secure and stable operation of power grid and electric accessory. Compared with general pipeline laid in the soil, earth electrode is under the circumstance of unbalanced grounding current of neutral point and electric field induced by high-voltage transmission line, so there is current straightly overflowing from electrode surface to the earth. Grounding current density carried by earth electrode is large, with an important effect on electrochemical corrosion of earth electrode in the soil. If serious corrosion happens, it will result in blocked current overflowing, rising in grounding resistance. Grounding potential will rise to high voltage sneaking into secondary circuit, which always expands fault accident, when there is ground-fault or lightning accident, once earth electrode cannot meet the thermal stability requirements. Therefore, model current overflowing and corrosion of earth electrode, to study effect of various current inputted to earth electrode on its corrosion, which will be of great significance to corrosion degree prediction and evaluation of earth electrode with various grounding current in power system.For the effect of current overflowing of earth electrode on its corrosion, this paper builds current overflowing model of single earth electrode in homogeneous soil and corrosion model respectively. This paper, moreover, study effect of various current inputted to earth electrode on its corrosion, combining current overflowing model and corrosion model. Main work content of this paper as follows:Firstly, build current-overflowing theoretical models of single horizontal, vertical and slant earth electrode in infinite homogeneous soil by collocation method. Considering effect of buried depth of earth electrode, build current-overflowing theoretical models in semi-infinite homogeneous soil. Choose horizontal earth electrode as representative for theoretical calculation. Build current-overflowing 2D simulation model of horizontal earth electrode in infinite/semi-infinite soil to verify the theory and analyze applicability of theoretical model. Because earth electrode connects power device by down lead, build more practical current-overflowing 2D and 3D simulation model of horizontal earth electrode with down lead in semi-infinite soil and carry out simulation analysis. What's more, study effect of amplitude and frequency of grounding current on electrical characteristic of earth electrode.Secondly, build simplified corrosion model irrespective of species diffusion and precise corrosion model respective of species diffusion respectively for earth electrode corrosion, based on soil conductive mechanism by whether to take species diffusion into account. In corrosion model irrespective of species diffusion, soil conducting property is expressed with equivalent conductivity, study corrosion potential, current, deformation, and effect of soil conductivity on corrosion. Build precise corrosion model respective of species diffusion, considering mass transfer process and equilibrium reactions. Simulate corrosion potential, current and deformation. Study effect of Fe(OH)2 precipitation on corrosion.Finally, based on corrosion model built above, make comparative study on effect of various type of current overflowing on deformation of corrosion and cathodic and anodic current, which is the character of corrosion. What is more, study effect of alternating current amplitude and frequency on corrosion. Furthermore, do simulated experiment and compare experiment results, results in other published literatures and simulated analysis of software to verify corrosion model and effect of current overflowing on corrosion.