The information in this paper includes the basic corrosion theory and forms of substation grounding grid corrosion. In order to investigate the corrosion in substation grounding grid and acquire corrosion data to give a guide for steel grounding grid's design, 21 grounding grids of substations distributed in different areas of Foshan were excavated to test corrosion rates of grounding conductors. Corrosion data show that corrosion in grounding down leads and grounding conductors in cable trenches are more serious than in the main grounding grid. Corrosive factors in the substation soil samples were measured on the spots and in the lab, and the data were analyzed using the principal component analysis method for statistics. The result demonstrated that soil resistivity, pH value, water content and soluble salts content were the key factors in substation grounding grid corrosion. Different methods available for the protection of steel grounding grids are discussed in this paper. Allowance for corrosion should be provided for both uniform and pitting corrosion while selecting the area of the grounding conductors based upon the soil corrosion data.
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