A method for determining a distance of a phase-to-phase fault or a three-phase 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; detecting a phase-to-phase fault or a three-phase fault on the three-phase electric line, characterized in that the method comprises: determining a first estimate value for a distance between the measuring point and a point of the detected phase-to-phase fault or three-phase fault on the basis of values of the monitored current and voltage quantities and a first equation which relates the current and voltage quantities to the distance and is based on a fault loop model of the electric line, in which model the point of fault is located between the measuring point and the total load of the electric line which is modelled to be concentrated in a single point of the electric line; determining a second estimate value for the distance between the measuring point and the point of the detected phase-to-phase fault or three-phase fault on the basis of values of the monitored current and voltage quantities and a second equation which relates the current and voltage quantities to the distance and is based on a fault loop model of the electric line, in which model the total load of the electric line is modelled to be concentrated in a single point of the electric line and is located between the measuring point and the point of fault; and selecting according to predetermined criteria one of the determined two estimate values as the distance between the measuring point and the point of fault. monitoring current and voltage quantities of the three-phase electric line at a measuring point; detecting a phase-to-phase fault or a three-phase fault on the three-phase electric line, characterized in that the method comprises: determining a first estimate value for a distance between the measuring point and a point of the detected phase-to-phase fault or three-phase fault on the basis of values of the monitored current and voltage quantities and a first equation which relates the current and voltage quantities to the distance and is based on a fault loop model of the electric line, in which model the point of fault is located between the measuring point and the total load of the electric line which is modelled to be concentrated in a single point of the electric line; determining a second estimate value for the distance between the measuring point and the point of the detected phase-to-phase fault or three-phase fault on the basis of values of the monitored current and voltage quantities and a second equation which relates the current and voltage quantities to the distance and is based on a fault loop model of the electric line, in which model the total load of the electric line is modelled to be concentrated in a single point of the electric line and is located between the measuring point and the point of fault; and selecting according to predetermined criteria one of the determined two estimate values as the distance between the measuring point and the point of fault. determining a first estimate value for a distance between the measuring point and a point of the detected phase-to-phase fault or three-phase fault on the basis of values of the monitored current and voltage quantities and a first equation which relates the current and voltage quantities to the distance and is based on a fault loop model of the electric line, in which model the point of fault is located between the measuring point and the total load of the electric line which is modelled to be concentrated in a single point of the electric line; determining a second estimate value for the distance between the measuring point and the point of the detected phase-to-phase fault or three-phase fault on the basis of values of the monitored current and voltage quantities and a second equation which relates the current and voltage quantities to the distance and is based on a fault loop model of the electric line, in which model the total load of the electric line is modelled to be concentrated in a single point of the electric line and is located between the measuring point and the point of fault; and selecting according to predetermined criteria one of the determined two estimate values as the distance between the measuring point and the point of fault.