Creditability analysis of grounding grid corrosion diagnosis

In China, the serious accidents due to severe corrosion of substation's grounding grid often take place. To better analyze results of corrosion diagnosis for grounding grids, a novel approach to creditability analysis by means of testability matrix factorization was presented. A new testability matrix was derived, which has only to do with topological structure and test information without any partial derivative operation, and then nonlinear diagnostic equations were established. The branch ambiguity groups and the set of surely testable branches were obtained through the testability matrix by Gauss-Jordan elimination method. The example of simulation shows that the results of the surely testable components are changeless in different diagnosis under fully tested conditions. It points out that misdiagnosis is inevitably due to the existence of ambiguity groups.