Fault identification for single-phase auto-reclosure of transmission lines with high speed grounding switches

Along with the enhancement of power grid connection in China, it is possible for EHV/UHV transmission lines not to suppress power frequency over-voltage by reactors but by high speed grounding switches (HSGS) for fast arc extinction. In this paper the different features of current signals passing through HSGS due to instantaneous single-phase earth fault and permanent fault respectively are analyzed. Using Prony method, the current signals passing through HSGS are fast fitted every other power frequency period and the amplitudes of power frequency quantities can be extracted; then by means of analyzing the obtained series of amplitude information, it is discovered that for instantaneous fault the amplitude of power frequency quantity jumps from one stable value to another new value and the new value keeps stable, and yet for permanent fault the amplitude of power frequency quantity does not so behave, from this the nature of fault can be judeged. The Prony method possesses good fitting result for non-stationary signals and can implement the adaptive decomposition of frequencies, in addition, it is sensitive to the variation of signals, so the defect of Fourier algorithm that the non-stationary signals cannot be processed is remedied. Simulation results by Matlab/Simulink show that the proposed method is effective and correct.