The Method Of Grounding Grid Corrosion Rate Detection Of Weak Polarization And The Corrosion State Evaluation Of Strong Polarization

Grounding grid is a network formed by connecting to a plurality of grounding by grounding lines. Its main role is to the safe operation of the equipment, while providing fault current discharge channel. With the development of the power system, the ground fault current is increasing, and the requirements for safety grounding grid reliability proposed also higher. Because of poor grounding mesh welding, soil erosion and other factors, the main grounding grid and ground deflectors will emerge to corrosion or even fracture. This will lead to ground discharge performance degradation, and affecting the normal operation of the power system. Also, because the grounding grid buried in the ground, it is hard to detect whether its corrosion or not. So, a new diagnostic methods for grounding grid corrosion detection has practical significance to power system operation reliability.This paper discusses and compares the grounding grid’s corrosion diagnosis method at domestic and foreign. Relatively few studies on grounding grid corrosion rate monitoring and grounding grid corrosion evaluation of these two aspects, so it needs to be improved for grounding grid corrosion rate monitoring and condition assessment method of research. Because of the grounding grid in the soil is mainly emerge to electrochemical corrosion, this article discusses the factors affecting corrosion and the mechanism occurred grounding grid erosion in soil. Also, we analyze the feasibility of grounding grid corrosion diagnosis based polarization principle, and discuss the different polarization measurement methods. We get the conclusion that corrosion rate monitoring at weak polarization region and corrosion evaluation at strong polarization region are feasible.This paper establishes indoor experiment platform and discussed grounding grid corrosion rate of different materials in the same kind of environment. We get the conclusion that the more active metal more prone to corrosion. By monitoring the different corrosion degree of grounding material in the corrosion rate under the same kind of environment, we found that the state of corrosion of metal surfaces come influence on the corrosion rate, which Shows that this method is only applicable to instantaneous corrosion rate of detection but does not reflect the state of the ground material corrosion. Simultaneously, we design a simple three-electrode electrochemical probe, and to verify the feasibility of the method in real grounding grid indirect measurement of the corrosion rate.Based on the electric double-layer model, we propose a method to use polarization decay curve parameters to evaluate corrosion. In this method, we fit the decay curve parameters of the ground electrode. By decay time parameters, charging factor and other parameters, we used to evaluate the grounding grid electrode face corrosion conditions. This method shows differences on different metal material by fitting the parameters of polarization decay curves. By analyzing the measure results of the proving ground, and after normalization by the current parameters, we get that different signal strength have no effect on the results of the fit parameters; and for uniform corrosion ground network conductors, measurements are unrestricted by the position of the grounding.