Method for detecting a fault on a line of an electrical power supply system, in which - first current values are measured at a first line end of the line ; - further current values are measured at least at a further line end of the line ; - the first and the further current values are used to check whether there is a fault on the line ; wherein - first voltage values are measured at the first line end of the line ; - further voltage values are measured at the at least one further line end of the line ; - the first current and voltage values measured at the first line end are used to ascertain first comparison current values indicating the current flowing at a comparison location on the line ; - the further current and voltage values measured at the at least one further line end are used to ascertain further comparison current values indicating the current flowing at the comparison location on the line ; and - the first and the further comparison current values are used to check for the presence of a fault on the line , and a fault signal is generated if the check has resulted in a fault present on the line being detected, wherein - the comparison current values are determined by using a mathematical model of the line for the fault-free case; and - the comparison current values are estimated by using the first and the further current and voltage values and also the mathematical model of the line, wherein the estimation is performed by considering the propagation of travelling waves along the line ; characterized in that - the comparison current values are estimated by subjecting the first and the further current and voltage values to a filtering, wherein the filter is used to reproduce a transfer function dependent at least on the propagation constant of a travelling wave along the line and/or a transfer function dependent on the characteristic impedance of the line. - first current values are measured at a first line end of the line ; - further current values are measured at least at a further line end of the line ; - the first and the further current values are used to check whether there is a fault on the line ; wherein - first voltage values are measured at the first line end of the line ; - further voltage values are measured at the at least one further line end of the line ; - the first current and voltage values measured at the first line end are used to ascertain first comparison current values indicating the current flowing at a comparison location on the line ; - the further current and voltage values measured at the at least one further line end are used to ascertain further comparison current values indicating the current flowing at the comparison location on the line ; and - the first and the further comparison current values are used to check for the presence of a fault on the line , and a fault signal is generated if the check has resulted in a fault present on the line being detected, wherein - the comparison current values are determined by using a mathematical model of the line for the fault-free case; and - the comparison current values are estimated by using the first and the further current and voltage values and also the mathematical model of the line, wherein the estimation is performed by considering the propagation of travelling waves along the line ; characterized in that - the comparison current values are estimated by subjecting the first and the further current and voltage values to a filtering, wherein the filter is used to reproduce a transfer function dependent at least on the propagation constant of a travelling wave along the line and/or a transfer function dependent on the characteristic impedance of the line. <EOS>