Electrochemical Method on the Optimum Cathodic Protection Potential of Grounding Grid in High Resistivity Soil

High resistivity soil may cause serious corrosion of substation grounding grid. The cathodic polarization curve and electrochemical impedance spectroscopy (EIS) of grounding grid metal at open circuit potential and different cathodic polarization potential were measured by electrochemical method. The method to determine the optimal cathodic protection potential (OCPP) of grounding grid in high resistivity soil was established. The result showed that the OCPP of Q235 steel was about -850 mV (vs. SCE), and the method was verified by immersion weight loss test. It is simple and feasible to use electrochemical method to study OCPP for cathodic protection of substation grounding grid, which is of great significance to prevent the corrosion of grounding grid, extend the service life of grounding grid and ensure the safe operation of grounding device.