Differential protection method for monitoring a line of a power grid, in which - current indicator measured values are measured in each case with measuring devices at the ends (11a, 11b) of the line, said values indicating the amplitude and phase angle of a phase current flowing at the respective end (11a, 11b) of the line, wherein the measuring devices have local timers and allocate a timestamp to the current indicator measured values indicating the time of their measurement; - at least the current indicator measured values measured at one end are transmitted via a communication connection to an evaluation device; - a differential current value is formed through vectorial addition by means of the evaluation device with current indicator measured values temporally allocated to one another, wherein time delay information indicating the time delay between the local timers of the measuring devices is used for the temporal allocation of the current indicator measured values measured at different ends (11a, 11b); and - a fault signal indicating a fault affecting the line is generated if the differential current value exceeds a predefined threshold value; characterized in that - a check is carried out using electrical measured quantities temporally allocated to one another which have been measured at different ends (11a, 11b) of the line and a line-specific parameter relating to the line running between the ends (11a, 11b) in order to determine whether the time delay information indicates the actual time delay between the respective local timers, a comparative phase angle being determined using the electrical measured quantities and the line-specific parameter and using the comparative phase angle to check the time delay information, wherein the comparative phase angle is determined by extending the electrical measured quantities temporally allocated to one another by the amount of the line-specific parameter and using the angle located between the extended amplitudes as the comparative phase angle; and - a time error signal is generated if erroneous time delay information is detected in the check. - current indicator measured values are measured in each case with measuring devices at the ends (11a, 11b) of the line, said values indicating the amplitude and phase angle of a phase current flowing at the respective end (11a, 11b) of the line, wherein the measuring devices have local timers and allocate a timestamp to the current indicator measured values indicating the time of their measurement; - at least the current indicator measured values measured at one end are transmitted via a communication connection to an evaluation device; - a differential current value is formed through vectorial addition by means of the evaluation device with current indicator measured values temporally allocated to one another, wherein time delay information indicating the time delay between the local timers of the measuring devices is used for the temporal allocation of the current indicator measured values measured at different ends (11a, 11b); and - a fault signal indicating a fault affecting the line is generated if the differential current value exceeds a predefined threshold value; characterized in that - a check is carried out using electrical measured quantities temporally allocated to one another which have been measured at different ends (11a, 11b) of the line and a line-specific parameter relating to the line running between the ends (11a, 11b) in order to determine whether the time delay information indicates the actual time delay between the respective local timers, a comparative phase angle being determined using the electrical measured quantities and the line-specific parameter and using the comparative phase angle to check the time delay information, wherein the comparative phase angle is determined by extending the electrical measured quantities temporally allocated to one another by the amount of the line-specific parameter and using the angle located between the extended amplitudes as the comparative phase angle; and - a time error signal is generated if erroneous time delay information is detected in the check.