Damage diagnosis method for ultra-long cable

The invention discloses a damage diagnosis method for an ultra-long cable. The method comprises the following steps that an Ethernet physical layer chip sends a continuous pulse signal and starts a timer T; the Ethernet physical layer chip detects a first reflection pulse exceeding a threshold value A1 and records the time t1 of the timer at the moment, and a near-end reflection test is completed;the Ethernet physical layer chip resends the continuous pulse signal and restarts the timer T; the Ethernet physical layer chip dynamically adjusts the threshold A2 according to the timer T; the Ethernet physical layer chip detects a first reflection pulse exceeding a threshold value A2 and records the time t2 of the timer at the moment, and a far-end reflection test is completed; and the difference value between t2 and t1 is calculated to obtain the damage position of the cable. According to the damage diagnosis method for the super-long cable, the damage of the super-long cable can be accurately diagnosed. 本发明揭示了一种