A method for use in earth-fault protection in a three-phase electric network, comprising: detecting a phase-to-earth fault in the three-phase electric network; determining at a measuring point in the three-phase electric network, for each of the three phases (A, B, C) of the three-phase electric network, a phase current during the detected phase-to-earth fault or a change in the phase current due to the detected phase-to-earth fault; and detecting a faulted phase of the three-phase electric network, characterized in that the method comprises: determining an estimate of an earth-fault current in a point of the detected phase-to-earth fault passing through the measuring point on the basis of the faulted phase and the determined phase currents of the three phases of the three-phase electric network, wherein the estimate is based on a negative-sequence current component, or on the basis of the faulted phase and the determined changes in the phase currents of the three phases of the three-phase electric network; determining a zero-sequence voltage of the three-phase electric network during the detected phase-to-earth fault or a change in the zero-sequence voltage of the three-phase electric network due to the detected phase-to-earth fault; and determining a direction of the phase-to-earth fault from the measuring point on the basis of the determined estimate of the earth-fault current and the determined zero-sequence voltage or on the basis of the determined estimate of the earth-fault current and the determined change in the zero-sequence voltage. detecting a phase-to-earth fault in the three-phase electric network; determining at a measuring point in the three-phase electric network, for each of the three phases (A, B, C) of the three-phase electric network, a phase current during the detected phase-to-earth fault or a change in the phase current due to the detected phase-to-earth fault; and detecting a faulted phase of the three-phase electric network, characterized in that the method comprises: determining an estimate of an earth-fault current in a point of the detected phase-to-earth fault passing through the measuring point on the basis of the faulted phase and the determined phase currents of the three phases of the three-phase electric network, wherein the estimate is based on a negative-sequence current component, or on the basis of the faulted phase and the determined changes in the phase currents of the three phases of the three-phase electric network; determining a zero-sequence voltage of the three-phase electric network during the detected phase-to-earth fault or a change in the zero-sequence voltage of the three-phase electric network due to the detected phase-to-earth fault; and determining a direction of the phase-to-earth fault from the measuring point on the basis of the determined estimate of the earth-fault current and the determined zero-sequence voltage or on the basis of the determined estimate of the earth-fault current and the determined change in the zero-sequence voltage. determining an estimate of an earth-fault current in a point of the detected phase-to-earth fault passing through the measuring point on the basis of the faulted phase and the determined phase currents of the three phases of the three-phase electric network, wherein the estimate is based on a negative-sequence current component, or on the basis of the faulted phase and the determined changes in the phase currents of the three phases of the three-phase electric network; determining a zero-sequence voltage of the three-phase electric network during the detected phase-to-earth fault or a change in the zero-sequence voltage of the three-phase electric network due to the detected phase-to-earth fault; and determining a direction of the phase-to-earth fault from the measuring point on the basis of the determined estimate of the earth-fault current and the determined zero-sequence voltage or on the basis of the determined estimate of the earth-fault current and the determined change in the zero-sequence voltage.