Study on the affection of ground grids with varied aspect ratio on frequency characteristics of grounding impedance

In order to study ground grids with varied aspect ratio impact on grounding impedance, this paper considers the characteristics of the transient electromagnetic conductors and compares frequency characteristic curve of grounding impedance, after the simulation and calculation based on the CDEGS, which is famous for measuring the grounding resistance in the world. The results show the inductive component of grounding impedance is related to injecting point of ground short-circuit current. As the aspect ratio of ground grids decrease at power frequency, the resistive component of grounding impedance be comes greater and greater. The impact of grounding impedance under five different aspect ratio is compared at several frequencies other than power frequency, by parameter calculation and simulation analysis, the results indicate the design of large substation ground grids should be made with an aspect ratio of 6/5: 5/6, and perhaps could be set as a standard in grounding system design and modification in distribution substations.