Pilot protection method and system for high-voltage direct-current transmission line

The invention discloses a pilot protection method and system for a high-voltage direct-current transmission line, and the method comprises the steps: carrying out the low-pass filtering of voltages and currents measured at protection installation parts at two sides of a line after relay protection devices at two sides of positive and negative direct-current transmission lines are started, and carrying out the pole-mode conversion; obtaining rectification side 1-mode voltage and 1-mode current and inversion side 1-mode voltage and 1-mode current; enabling the DC line to be segmented and equivalent to two pi-shaped lines, and calculating the midpoint current of the DC line based on the segmented and equivalent lines; scanning and matching the waveform of the midpoint current, and judging thefault position. According to the method, the internal and external faults of the direct-current line area can be quickly and accurately judged, the protection performance is not influenced by the fault transient state, the t