Patent ID: 8044666

Claim:
A method for determining a location of a phase-to-earth fault on a three-phase electric line of an electric network, the method comprising: monitoring current and voltage quantities of the three-phase electric line at a measuring point; determining an equivalent load distance curve of the electric line representing a voltage drop along the electric line in relation to a distance from the measuring point which voltage drop is scaled by an equivalent load distance of the electric line which indicates a distance of an equivalent load point from the measuring point which equivalent load point equals to a total load of the electric line modelled to be concentrated in a single point of the electric line; determining, after a fault occurs in the three-phase electric line, a fault distance line which indicates an estimate of the distance of the fault from the measuring point in relation to the equivalent load distance on the basis of values of the monitored current and voltage quantities during the fault and an equation which relates the monitored current and voltage quantities to the fault distance; determining a distance from the measuring point at which the equivalent load distance curve and the fault distance line intersect when superimposed; and selecting the determined distance as the distance between the measuring point and the point of fault.