Novel method for diagnosing corrosion of grounding electrodes in soil

Tower grounding electrodes buried in the soil are prone to corrosion. The current dissipation will be affected by corrosion. Accurate evaluation for the corrosion status of grounding electrodes is critical for the safe and stable operation of power system. At present, grounding resistance closely related to environmental soil resistivity is an important indicator for evaluating grounding performance. To eliminate the influence of soil resistivity, a method for diagnosing corrosion of tower grounding electrodes is proposed. The grounding resistance in soil of different resistivity can be equivalent to the grounding resistance in soil of reference resistivity to diagnose the corrosion degree under the unified diagnostic criteria. In this study, the corrosion deformation and corrosion products are analysed, and a model of horizontal linear tower grounding electrode with corrosion products layer is established. Calculation method of the grounding resistance for corroded electrode is studied. The relative grounding resistance is proposed as a corrosion diagnosis criterion and dividing the corrosion degrees based on the criterion. Finally, the error analysis of the diagnosis method are given, and the measurement and diagnosis system is studied through field experiments. Calculation and experiment results validated the accuracy of the proposed method.