Method and apparatus for determining the distance to phase-to-earth fault

摘要

Method and apparatus for determining a distance to a phase-to-earth fault on a three-phase electric line of an electric network, the apparatus comprising means for determining, during a phase-to-earth fault (F) on the three-phase electric line (30), current and voltage values, when a neutral to earth admittance of the electric network outside the electric line (30) has a first value, means for determining current and voltage values, when the neutral to earth admittance of the electric network outside the electric line (30) has a second value different from the first value, and means for determining the distance to the phase-to-earth fault (F) from the measuring point (40) on the basis of the determined current and voltage values, wherein the means for determining the distance are configured to use four equations derivable from an equivalent circuit for a phase-to-earth fault on a three-phase electric line.