Due to the cable fault caused by cable laying, the location of cable fault varies with the cable laying mode, and the location increases gradually. Among them, the laying side in bridges, tunnels and trenches is relatively simple, and the direct burial method is difficult to locate. When the nature of the fault is simple, a special cable fault finder is used, and it takes 4-5 days or even longer to locate the equipment within dozens of minutes. When using echo method to locate cable fault, sometimes by transferring fault phase and wiring mode, complex fault will often be transformed into simple fault to quickly determine fault location. It is of great significance for the power supply user department to win time for the emergency repair of on-site lines. Low voltage power cables are generally multi-core cables. When faults occur in continuous use after laying, they generally show two core and multi-core phase to phase or phase to ground short circuit faults. Sometimes when it is detected that the fault waveform collected by one core is not ideal, it can be considered to convert the wiring to other fault cores for fault waveform detection, which often has unexpected effects, The collected and detected waveforms will become more typical and regular, so the specific location of cable fault point can be determined quickly. During the long-term on-site measurement of cable customers, it is found that the fault of small section copper core directly buried power cable (35mm2 and below) and aluminum core cable may be accompanied by short circuit and wire breakage at the same time. During on-site detection, converting short-circuit fault into broken line fault measurement according to the different fault nature of each fault core will often double everything with half the effort. For the medium voltage direct buried power cable with extruded armor as the inner lining, the fault is mostly caused by external mechanical damage. When the insulation core fails, the inner lining may have been damaged. When the cable insulation fault is special and it is difficult to collect the waveform with a professional cable fault tester, the acoustic method can be considered, When the high voltage pulse is directly applied between the steel strip and copper shielding layer of the cable, it will often be fixed quickly. Using the cable fault finder in the field measurement process, we also found that when using the acoustic method to locate the fault of low-voltage cable. When the high-voltage line and ground wire are connected between the bad phase and the metal shield or armor, due to the low resistance metal connection state of the insulation resistance of the two, the sound is very small, so the probe can not be used to listen to the fixed point, and the effect is not ideal. Through the actual listening side on the site for many times, it is found that the distance between the discharge ball gaps is appropriately increased. At the same time, if the high voltage and grounding wire are connected between the two faulty phases, the discharge sound will become louder and the fault point will be determined quickly.