The detection of cable fault generally goes through three steps: diagnosis, ranging and fixed point. 1. Cable fault nature diagnosis the diagnosis of cable fault nature, that is, to determine the type and severity of fault, so that testers can suit the remedy to the case and select appropriate cable fault location and fixed-point methods. 2. Cable fault location cable fault location, also known as rough measurement, uses instruments to determine the fault distance at one end of the cable. The common fault location methods at the test site include classical bridge method (high voltage bridge and low voltage bridge) and modern traveling wave method (pulse method: low voltage pulse method and high voltage pulse method). 3. Cable fault location cable fault location, also known as precise measurement, is to find out the general orientation of the fault point according to the fault location results and the path direction of the cable, and determine the accurate location of the fault point within a very small range by using the discharge acoustic measurement method or other methods. Generally speaking, successful cable fault detection must go through the above three steps, otherwise it will not be achieved if you want to speed up. For example, it is very difficult to detect the discharge sound at the fault point along a long cable path (possibly several kilometers long) without fault location. If the cable fault distance is known and a general orientation is determined, it is much easier to move the fixed-point instrument back and forth within a small range (about 10m) to detect the discharge sound at the cable fault point.