A method of protecting an electrical link in a medium, high, or very high voltage network, in which two differential protection devices, or relays, (8, 9) are disposed at the two ends (A, B) of said link, including the following steps: · apply a voltage to the relay (step 20); · measure the outward-and-return propagation time (step 21); · phase shift the sinusoidal curves of the current received from the far end, on the basis of the ratio 0.5 outward/ 0.5 return (step 22); said method being characterized in that it comprises the following steps: · first test (step 23) to find out whether a determined time has elapsed; 1) If result of this first test is negative (step 23) · phase shift the sinusoidal curves of the current received from the far end, on the basis of the ratio 0.5 outward/ 0.5 return (step 24); · obtain Fresnel diagrams for the current without servocontrolling the phases at the far end (step 25); · calculate the differential current and the retained current for each phase (step 26); · second test to find out whether one of the differential currents is in the trip zone (step 27); · trip the differential protection apparatus if result of this second test is positive (step 28); 2) If result of this first test is positive (step 23) and if result of the second test is negative (step 27): · Test to compare the phase difference ΔØ between the locally measured current and the current measured remotely, for each phase, with at least one determined value, and optional servocontrol of the phase of each end current at 180° relative to each corresponding local current (step 30). · apply a voltage to the relay (step 20); · measure the outward-and-return propagation time (step 21); · phase shift the sinusoidal curves of the current received from the far end, on the basis of the ratio 0.5 outward/ 0.5 return (step 22); · first test (step 23) to find out whether a determined time has elapsed; 1) If result of this first test is negative (step 23) · phase shift the sinusoidal curves of the current received from the far end, on the basis of the ratio 0.5 outward/ 0.5 return (step 24); · obtain Fresnel diagrams for the current without servocontrolling the phases at the far end (step 25); · calculate the differential current and the retained current for each phase (step 26); · second test to find out whether one of the differential currents is in the trip zone (step 27); · trip the differential protection apparatus if result of this second test is positive (step 28); 2) If result of this first test is positive (step 23) and if result of the second test is negative (step 27): · Test to compare the phase difference ΔØ between the locally measured current and the current measured remotely, for each phase, with at least one determined value, and optional servocontrol of the phase of each end current at 180° relative to each corresponding local current (step 30). 1) If result of this first test is negative (step 23) · phase shift the sinusoidal curves of the current received from the far end, on the basis of the ratio 0.5 outward/ 0.5 return (step 24); · obtain Fresnel diagrams for the current without servocontrolling the phases at the far end (step 25); · calculate the differential current and the retained current for each phase (step 26); · second test to find out whether one of the differential currents is in the trip zone (step 27); · trip the differential protection apparatus if result of this second test is positive (step 28); · phase shift the sinusoidal curves of the current received from the far end, on the basis of the ratio 0.5 outward/ 0.5 return (step 24); · obtain Fresnel diagrams for the current without servocontrolling the phases at the far end (step 25); · calculate the differential current and the retained current for each phase (step 26); · second test to find out whether one of the differential currents is in the trip zone (step 27); · trip the differential protection apparatus if result of this second test is positive (step 28); 2) If result of this first test is positive (step 23) and if result of the second test is negative (step 27): · Test to compare the phase difference ΔØ between the locally measured current and the current measured remotely, for each phase, with at least one determined value, and optional servocontrol of the phase of each end current at 180° relative to each corresponding local current (step 30). · Test to compare the phase difference ΔØ between the locally measured current and the current measured remotely, for each phase, with at least one determined value, and optional servocontrol of the phase of each end current at 180° relative to each corresponding local current (step 30).