Corrosion Diagnosis of Conductors and Down Lead Lines for Grounding Grids Maintenance

To improve the efficiency of the corrosion diagnosis, based on the hierarchical model, an actual grounding grid can be divided into six levels, such as actual grids, quasi- circuit-domain, circuit-domain, circuit-network, touchable network and intrinsic network. Based on above model, a novel node partition based approach is put forward. In which, a grounding grid is divided into several small-scale sub-grids. Taking the down lead line resistances into consideration, a set of linear equations for the conductance of the intrinsic branches in each sub-grid is deduced and solved, respectively, without the nonlinear iteration. Corrosion diagnosis of the down lead lines is also carried out for each sub-grid, respectively. A dynamic planning based optimization procedure to reduce the work in the maintenance is proposed, with which, the best test scheme can be worked out. An experimental grounding grid with sixty branches is used as an example. The results of corrosion diagnosis show that the proposed approaches are feasible with the maintenance works remarkably reduced.