| 摘要 |
<p>A method and an apparatus for detecting a phase-to-earth fault on a three-phase electric line (30) of an electric network, the apparatus comprising means for determining a neutral admittance, or a quantity indicative thereof, on the basis of a ratio between a difference between zero sequence currents on the three-phase electric line and a difference between zero sequence voltages in the electric network before an earth fault and during the earth fault; and means for comparing the determined neutral admittance, or the quantity indicative thereof, to a predetermined operation characteristic to detect a phase-to-earth fault on the three-phase electric line, wherein the predetermined operation characteristic, when presented on an admittance plane, defines a closed area such that the centre of the closed area is offset from the origin of the admittance plane towards a negative susceptance direction and/or towards a negative conductance direction.</p> |
