To effectively analyze the impulse characteristics of a substation grounding grid and ensure the reliable operation of electrical equipment in the substation as well as the security of personnel

two grounding grid models with regular and irregular configurations were designed according to the real grounding grid in 35 kV substations on the basis of the principle of dimensionless similarity. The typical faults of grounding grid

including corrosion and fracture

were simulated with the models

and experiment was conducted to measure the impulse grounding resistance of the grounding grid models. The experimental results show that: 1)The impulse characteristics vary with the impulse current and the injecting position;2)The transient leakage current characteristics of the regular grounding grid is better than that of the irregular grounding grid; 3)For the same injecting position of impulse current in grounding grid

the shorter the wave head of impulse current

the higher the impulse grounding resistance of the grounding grid;4)The impulse grounding resistance get the smallest when the impulse current is injected to the center of the grounding grid; and 5)The impulse grounding resistance increases when there are typical faults in the grounding grid

and the increment of the resistance depends on the wave head of impulse current.