Single-phase earth fault positioning method and system

The invention discloses a single-phase earth fault positioning method and system. The method comprises the following steps: when a single-phase earth fault of a line is detected, selecting the line and judging whether the line is instantaneously grounded or not; if yes, the zero-sequence current and the grounding alarm signal of the off-station terminal are obtained, and topology checking is carried out on the line selection result; if the verification is passed, calculating a zero-sequence current score according to the zero-sequence current abrupt change rate, calculating an alarm score according to the grounding alarm signal at the fault moment, and calculating a weighted sum of the zero-sequence current score and the alarm score to obtain an assigned score of the terminal outside the station; and selecting a target off-station terminal of which the difference between the assignment value of the target off-station terminal and the assignment value of the adjacent downstream off-station terminal is greater