Fault Diagnosis For Grounding Grids Based On Electric Network Theory

Grounding grid in substation is vital for preserving the safety and reliablity of power system, protecting the operator and electrical equipment. The grounding grid of substation is buried in the ground. The soil acid and alkali induce the grid corrosion, which leads to the grounding performance deteriorated, and will cause accidents and bring huge economic losses. Large-scale excavation is often used method of corrosion failure of the grounding checks, this method with much of blindness. So looking for a kind not excavation case, for the grounding systems fault diagnosis is very necessary.This paper applied electric network theory, matrix theory, optimization technique for the analysis of substation grounding grid model, using a variety of incentive method for measuring the potential of grounding grid grounding wire, using Tellegen theorem establish fault diagnosis equation, with iterative and optimization method to solve underdetermined equations. Grounding grid is equivalent to a pure resistance network, with PSpice software network simulation calculation, reaching its port resistance original data at not fault; Then based on the network have one or a few branch corrosion or break, get the new port resistance, compared with the original data, solving fault diagnosis equation get resistance branch, realizing fault diagnosis. By measuring the resistance of the ground lead changes, generation into diagnosis program testing grounding grid corrosion. For more complex network, first block reduction network, the increase of the proportion of the touchable nodes, and then diagnosing network, it is concluded that the fault branch of position.In order to validate the theory method, first with small resistance components lap a small resistance network. Setting fault branch, with different resistance to replace the branch, and simulation of different level corrosion fault; Then cut off the branch to simulate the breaking of branch. To further validate this method, a simulation of welded steel grounding grid, its branch resistance very similar to the actual value, so when measureing this data, try to avoid contact resistance and lead resistance interference. Diagnostic results of experimental measurements are consistent with the actual set position, which verification of this method of grounding fault diagnosis accuracy and feasibility. Finally, the impact of the grounding network diagnostic factors are analyzed.