The difference between old grounding grid and new one is that the old grounding grid has some corroded branches in addition to the breakage of some conductors.In order to analyze the impacts of the corroded branches on diagnosis of the conductor breakage in grounding grid

this paper establishes a mathematical model of grounding grid conductor breakage diagnosis using MATLAB based on binary genetic algorithm.Taking the real grounding gird of Chongqing 110 k V Shangqiao substation as an example

eight groups of simulation experiments are conducted.The diagnostic results of the eight groups of simulation experiments and the potential variation of each node are analyzed

and the values of fitness function under different cases of conductor breakage are calculated.The impacts of corroded branches on the diagnostic results are also analyzed by making use of branch sensitivity method.Experimental results show that: for the grounding grid without corrosion or with slight corrosion

the diagnoses can accurately find the branch containing broken conductor;for grounding grid with medium or severe corrosion

the diagnoses do not miss the branch containing broken conductor

but misdiagnosis may happen.The reason why misdiagnosis happens is that the corroded branch is located near the fixed point in the fixed point measurement method.By removing the measured data of node No.22

the diagnoses give accurate results.