Splitting method for grounding grids corrosion diagnosis using a block dividing approach

To benefit the corrosion diagnosis, generally, the spiltting method of circuit theory is used which can divide the larger ground grid into several small scaled sub-grids to diagnosis by several touchable nodes. The testability for branches can be changed, by adopting the traditional splitting method, namely, along with the touchable nodes splitted. First, the influence of testability for braches is analyzed. The concepts of blocks and their prototypes, uncertain-branch groups and their prototypes, projection of blocks and part of touchable nodes are defined. Based on the mode of block, a new approach of grounding grids corrosion diagnosis by blocks is put forward. According to the desired corrosion diagnosis area, the blocks together with their projections and the parts of touchable nodes, which participate in the diagnosis are determined. According to the testing data of the corresponding parts, the resistances of intrinsic branches in a block can be determined by a linear least square method, thereby, the resistances of clear branches in the block can be worked out. The ranges of resistances of uncertain-branches in the block are also evaluated by a dichotomy algorithm. With the proposed approach, a grounding grid can be divided into several small scaled sub-grids. As a result, the efficiency is improved and the cross-interferences are reduced. An experimental grounding grid with thirty-eight branches is used as an example. The results of corrosion diagnosis show that the proposed approaches are feasible and only a few tests are needed to meet the requirements of diagnosing a certain part of the grounding grid, and the efficiency of corrosion diagnosis can be improved rapidly by the method.