A method for determining a faulty line in a power system compensation grid, wherein the power system compensation grid is a power system grid whose neutral point is not directly grounded, wherein said power system compensation grid comprising a plurality of lines connected to a busbar, a pulse clock equipment configured to generate pulsed clock signals and a zero-sequence current in each line of said plurality of lines, an extinction coil, a capacitor connected in parallel with said extinction coil and a transformer connected with said busbar, said extinction coil is connected with the neutral point of said transformer, and said method comprising: - using pulsed clock signals generated by the pulse clock equipment to periodically enable/disable said capacitor to periodically generate detection currents on each line of said plurality of lines if a grounding fault happens in said power system compensation grid, wherein the enabling duration of said capacitor is preferably not equal to the disabling duration of said capacitor; - acquiring the detection currents on a line to be detected in said power system compensation grid, - determining a number of characteristic waveform patterns contained in waveforms of said detection currents in a preset range based on a change rate of said detection currents, wherein a characteristic waveform pattern is a waveform pattern reversely matching a one-period signal waveform of said pulsed clock signals, and - determining that said line to be detected is a faulty line if the number of characteristic waveform patterns is greater than or equal to a preset threshold, characterized in that determining the number of characteristic waveform patterns contained in the waveforms of said detection currents in the preset range based on the change rate of said detection currents comprises: - determining each current jump point in the waveforms of the detection currents in said preset range, wherein at a current jump point the current changes from a rising state or a steady state to a falling state, or from a falling state or a steady state to a rising state, - determining the corresponding steady-state current at each current jump point, and - determining the number of characteristic waveform patterns contained in the waveforms of said detection currents in said preset range based on the change rate of the corresponding steady-state current at each current jump point relative to the corresponding steady-state current at the previous current jump point. - using pulsed clock signals generated by the pulse clock equipment to periodically enable/disable said capacitor to periodically generate detection currents on each line of said plurality of lines if a grounding fault happens in said power system compensation grid, wherein the enabling duration of said capacitor is preferably not equal to the disabling duration of said capacitor; - acquiring the detection currents on a line to be detected in said power system compensation grid, - determining a number of characteristic waveform patterns contained in waveforms of said detection currents in a preset range based on a change rate of said detection currents, wherein a characteristic waveform pattern is a waveform pattern reversely matching a one-period signal waveform of said pulsed clock signals, and - determining that said line to be detected is a faulty line if the number of characteristic waveform patterns is greater than or equal to a preset threshold, - determining each current jump point in the waveforms of the detection currents in said preset range, wherein at a current jump point the current changes from a rising state or a steady state to a falling state, or from a falling state or a steady state to a rising state, - determining the corresponding steady-state current at each current jump point, and - determining the number of characteristic waveform patterns contained in the waveforms of said detection currents in said preset range based on the change rate of the corresponding steady-state current at each current jump point relative to the corresponding steady-state current at the previous current jump point.