Precautions are as follows:

1) First of all, it is necessary to list the possible causes of the fault and the basic situation of the cable, such as whether the fault is caused by operation or pre-test, whether it is a new cable or a cable with long operation time, the approximate length of the cable, whether there is a joint in the middle of the cable, whether the cable has failed before, whether the cable is directly buried or laid in the cable trench, and the type of cable, etc.

2) Make sure that the cable is tested only when there is no power. Both ends of the cable of the cable fault tester must be disconnected from other lines to ensure that the cable is dead and the surrounding environment of the cable is in a safe state.

3) The tester must pay attention to the operation safety. Before wiring with the cable each time, connect each phase line of the cable to the ground with a short line for discharge. During discharge, one end of the short line must be grounded and the other end must be connected to each phase line of the cable for discharge. For other electrical appliances, such as capacitors, test transformers, etc., pay attention to discharge before wiring and removing the connecting wire. In short, we should form operation habits and be not afraid of trouble. Before each operation, first pay attention to whether the operating electrical appliances are connected with the circuit, and then discharge before operation.

4) When testing the cable fault tester, first use the low-voltage pulse function of the flash tester to test the full length of each phase of the cable respectively to see whether the test waveform is consistent during the three relative tests. For most high resistance faults, the test waveforms of each phase are consistent. For low resistance fault and high resistance fault with open phase fault, the fault phase test waveform is inconsistent with the total length of the tested cable, so the fault distance can be measured directly with low-voltage pulse.

5) When the high voltage flashover method is used for testing, whether the cable fault is high resistance fault or low resistance fault, the high voltage impulse flashover method can be used for testing. For the low resistance or broken line fault that can directly test the fault distance with low-voltage pulse, it is generally necessary to use high-voltage impulse flash for verification test and accurate location of fault point.