Investigation on test schemes for grounding grids corrosion diagnosis

The requirements of a good test scheme are described, such as independent excitation, none-repeated measurement, large voltage signals and sensitive to the changes of branch resistances. Reciprocity theorem and superposition theorem can be used to determine whether a test scheme is completed. Theorem of Maximum Voltage is proved through reduction to absurdity, and its three inferences are put forward, based on which, the theoretical best test scheme is obtained, which suffers from the remarkable influence of grounding down line resistances. The suggested test scheme is presented which can avoid of above problem. A grounding grid with sixty branches is used as an example. Simulation results verify that the suggested test scheme is the most appropriate and with high performance in the practice.