Modeling and Simulation Analysis of Cable Ground Fault Detection in Ungrounded Neutral Systems in Coal Mines

When a single-phase high-impedance grounding fault occurs in a neutral point ungrounded system of a coal mine power grid, the fault characteristics are inconspicuous and the current is weak, imposing high measurement accuracy requirements on sensors and protection devices. To address the fault circuit identification problem, a fault line selection method based on the steady-state zero-sequence deviation method is proposed. The steady-state signal waveform is more stable and the state is more consistent compared with the transient signal, and it has a longer duration. Through formula derivation of the steady-state signal, it is found that the steady-state zero-sequence currents of the faulty line and the healthy lines exhibit deviations in both phase and amplitude, which is used as the line selection criterion. A simulation model is built using MATLAB/Simulink based on the actual coal mine power grid. The generated zero-sequence current waveforms of each line are analyzed, and the simulation results verify the effectiveness of the proposed line selection method.