Differential protection method for monitoring a line of a power grid, in which - current phasor measured values are captured 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 phasor measured values indicating the time of their capture; - at least the current phasor measured values captured 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 phasor 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 phasor measured values captured at different ends (11a, 11b), wherein - the time delay information is determined using a transit-time-based time synchronization method; 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 quotient of the current phasor measured values temporally allocated to one another is formed with the formation of an asymmetry variable, wherein the asymmetry variable is used to check a transit time difference of messages transmitted via the communication connection, which transit time difference arises on account of transmission times which are different depending on the direction. - current phasor measured values are captured 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 phasor measured values indicating the time of their capture; - at least the current phasor measured values captured 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 phasor 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 phasor measured values captured at different ends (11a, 11b), wherein - the time delay information is determined using a transit-time-based time synchronization method; and - a fault signal indicating a fault affecting the line is generated if the differential current value exceeds a predefined threshold value; - a quotient of the current phasor measured values temporally allocated to one another is formed with the formation of an asymmetry variable, wherein the asymmetry variable is used to check a transit time difference of messages transmitted via the communication connection, which transit time difference arises on account of transmission times which are different depending on the direction.