Abstract：Based on the fault analysis for a small current grounding system, a model for the system is built.The characteristic frequency bands are selected by a db10 wavelet packet. And the output of different type lines were analyzed by Duffing chaotic oscillator principle. By analyzing pure overhead lines, cable lines, and pure hybrid cable lines, it is found that the phase trajectories and first-order differential waveform have a large difference in the different line parameters. This difference can provide a new way to study the different types of line faults, and a new approach to investigate the amplitude and frequency in fault signals.

Keyword：chaotic oscillator;motion space;characteristic frequency band;phase trajectory;