Corrosion And Protection Of Extre High Voltage Grounding Grid

Grounding grid is an important device which ensure the safe operation of Substation. With the development of High Voltage Transmission, grounding grid corrosion is the key to the safe operation of the electric power. For this reason, Shanxi Provincial Power Company issued a research project as "Substation Grounding Grid Corrosion Protection". According to the requirements of the project,the protection of grounding grid was studied,using of soil inhibitor with impressed current cathodic protection method of combining. Meanwhile, Laboratory test results were laid in Weinan Xiaoyi 750kV Substation as Engineering Test. In the inhibitor study, by antithesis corrosion inhibitor concentration, temperature, soil moisture, etc were studied, selected the corrosion inhibitor formulations in low concentration with good effects. In the Impressed Current Cathodic Protection study, the polarization curves of carbon steel test samples in soil environment was detected by electrochemical three-electrode system, parameters such as the protection voltage were determined, on this basis, the degree of protection was calculated. Grounding Grid Corrosion relationship between speed and resistance was studied, which provided the basis for resistance method for corrosion rate measurement of grounding grids in project. The main conclusions are as follows:(1) Corrosion inhibitor formulation which have the best prevention of Q235 steel grounding grid corrosion effect in the soil as follows:0.4% NaNO2,1.2%(NaPO3)6 and 1.6% Na2MoO4, protection degree of up to 91.8%.(2) Impressed Current Cathodic Protection Act have better protection, When the protective voltage is-1.5V(SCE), the average protection degree is 78.3%. Corrosion inhibitor and impressed current cathodic protection act joint protection, protection degree of up to 98%.(3) Corrosion inhibitor and impressed current cathodic protection in bentonite, the protection degree of up to 98%, but the protective effect influenced by the moisture content in bentonite. (4) It was found that stray electrical currents have a significant impact on substation grounding grid corrosion in grounding grid burial sample experiment. Mixed inhibitor with impressed current cathodic protection combined action protection degree is only 89.6%, Compared with the results of laboratory studies to reduce by nearly 10%.(5) In the grounding grid pitting corrosion experiments, Corrosion depth A relationship with the resistance R is Minimum cross-sectional area has the greatest impact on resistance.