Corrosion Rate Simulation and Influence Factors of a Vertical DC Grounding Electrode

Abstract

Corrosion affects the performance of grounding electrode materials buried in soil and threatens the safe operation of power systems. Natural corrosion of grounding electrode materials occurs over a long time and involves many influencing factors. Simulating the true corrosion environment of grounding electrode materials, exploring the corrosion mechanism, and accurately determining the corrosion condition of these materials are problems that must be solved urgently. In this paper, a corrosion simulation model of a vertical carbon steel grounding electrode was built based on the principle of electrochemical corrosion. The influence of soil parameters (oxygen concentration, pH value, and chloride ion concentration) on the corrosion characteristics of the grounding electrode was calculated. The corrosion rates of the vertical grounding electrode at different burial depths were compared with and without direct current. Simulation results showed that the corrosion rate of the grounding electrode changed linearly with oxygen concentration in the soil, changed negatively and exponentially with pH, and changed logarithmically with chloride ion concentration. Grounding electrode materials should be buried at a depth of 2 m when the time with no current in the grounding electrode is more than that with current. This burial depth can effectively reduce the influence of oxygen concentration on grounding corrosion. Moreover, the local reduction in hydrogen ion content must be considered during the construction of a grounding electrode to ensure that the grounding electrode surface is in a strong alkaline environment, which can passivate the grounding electrode and reduce the corrosion rate.