Single-phase grounding fault direction discriminating method of double-circuit lines on the same tower

The invention discloses a single-phase grounding fault direction discriminating method of double-circuit lines on the same tower. The single-phase grounding fault direction discriminating method of double-circuit lines on the same tower measures the fault phase voltage, zero-sequence voltage and the zero-sequence current of a single-circuit line in double-circuit lines on the same tower. A compound polarized voltage is obtained by subtracting the fault phase voltage from the zero-sequence voltage. A direction judging evidence can be formed by a phase angle relationship between the zero-sequence current and the compound polarized voltage, so that a positive direction fault or an opposite direction fault happening in the protected circuit line can be actually discriminated. According to the single-phase grounding fault direction discriminating method of double-circuit lines on the same tower, the direction judging evidence is formed by utilizing the phase angle relationship between the zero-sequence current and the compound polarized voltage, so that impacts of zero-sequence mutual inductance between lines to protecting dynamic performances can be eliminated theoretically, the fault direction can be actually discriminated, and relay protection malfunction happening when the opposite direction fault occurs in the protected circuit line can be effectively prevented.